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North American
Terrestrial Vegetation
Second Edition
Edited by
Michael G. Barbour
William Dwight Billings
=corred deciduous io'ess;
5aands; .^'=.Aopzlachian
_re<u; P= coaszl plain íorQ=:rup:ca! róresr$. Bou.rd-
g ro W. D. Bi!:ngs; zn
CAMBRIDGE
UNIVERSITY PRESS
Contri
Prefac
Prefac
PLSLKHHED BY THE PRE55 SYVD!CATE OF THE C\:VER:T: iF CAVBR:D-E
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CHAPTER 1
Arctic
Latrrer
CHAPTER 2
The Ti
Debor.
CHAPTER 3
Forest
Robe,
CHAPTER 4
Pacifi,
Jerry F
CHAPTER 5
Califo
Micha
CHAPTER 6
Chapa
Jon E.
CHAPTER 7
Interr
N'eii E
CHAPTER 8
Wa rn
James
CHAPTER 9
Grass
Phi!1ip
CHAPTER 10
Easte;
Hzzc,
CHAPTER 11
Veget
N'or,m,
CHAPTER 12
Fresh
Curar=
CHAPTER 13
Salta.
In iro
Cs Cambnd ,e Cniversity Press 2958, 2300
This book is in copyright. Subject to sta.`cton' escephon
and lo the pro\isions o£ relevant collectice '. icensn, agreements,
no reproduc tlon of am- part mav take place t. ithout
the ., r.tten permission of Cambridge Universri' Press.
First publ!shed 1955
Second edi on 2000
Pnnted in the Cnited States of Amenca
Tv?cfr:e, 9/11 Palatino pt. DeskTopPro Ln IRFI
A ca:aing rcccrd for ilds book is n,:.riloble 5em f e Eritislr Librare.
Lrr,-v of Corgress Ca:aI ^i,rq-in-A,b'ics;ian Gas
North American terrestrial vegetation / edited by \S:hael G. Barbour,
William D,.'ight Billings. - 2nd ed.
p. cm.
'nclndes bibliographiczl referentes (p. ) en-' índex.
ISBN 0-521-55027- 0 (hardhcund)
1. P!ant commnni:ies - North America. 2. Plant ecology - North
.America. Phvtereo,raphv - North A-, eric a. 1. Barbour , '1ichael G.
II. Biilings, W. D. Q1'illiam Ació t), 1910-;997.
QK11 O.N854 1999
551.722097 - de i
ISBN 0 531 55027 0 hardback
ISBN 0 521 55956 3 paperback
9729C'cl
CIP
CHAPTER 14 Alpir.
CHAPTER 15
Meza,
A!e;.,
CHAPTER 16
The C
Are!
CHAPTER 17 Tro,n
Contents
Contribulors
Preface to the First Edition
Preface to the Second Edition
HAPTER 1
Arctic Tundra and Polar Desert Biome
page vi¡
ix
xi
1
Lawrence C. 3liss
41
CHAPTER 2
The Taiga and Boreal Forest
Deborah L. Ellon-Fisk
CHAPTER 3
Forests and Meadows oí the Rocky Mountains
Roben K. Pee:
CHAPTER 4
Pacific Northwest Forests
Ierry F. Frankii❑ and Charles B. Ha!pera
CHAPTER 5
Californian Upland Forests and Woodlands
Michael C. Barbourand Richard A. Minnich
161
CHAPTER 6
Chaparral
Ion E. Keeiey
203
CHAPTER 7
Intermountain Valleys and Lower Mountain Slopes
%eii E. L1'est and la .mes A. Young
255
CHAPTER 8
Warm Deserts
James A. Mac.^;ahon
285
CHAPTER 9
Grasslands
Phil!ip L_ Sims and Paul C. Risser
323
CHAPTER 10
Eastern Deciduous Forests
Haze! R. Delcoun and Paul A. Delcou: r
357
CHAPTER 11
Vegetation oí the Southeastern Coastal Plain
397
23
Norman L. Christensen
449
CHAPTER 12
Freshwater Wetlands
CHAPTER 13
Saltrnarshes and.\langroves
Irvin, A. Mendelssohn and Karen L. McKee
501
CHAPTER 14
Alpine Vegetation
William Dwight Billings
53%
CHAPTER 15
Mexican Temperate Vegetation
Alejandro Velázquez, Victor Manuel Toledo, and !solda Luna
573
Cunisl. Richardson
CHAPTER 16 The Caribbean
593
Ariel E. Lugo, Julio Figueroa Colón, and Frederick N. Scarena
CHAPTER 17
Tropical and Subtropical Vegetation of Mesoamerica
Gary S. Hanshorn
623
W. D. Bi/!ings
,.d 'oil develop\!'_:dro^. C- ac er,
G. Molenazr. L,
:crs in z:Cic and
unes, R. W. Hoharn,
fed>-) The ecologv
Carnbridge.
;.,D. 1\'a!ker, and
.,. studies of
.enze +_.-S ^,'5. Czrboh drate
^Le plants..amer.
of paterned
bu'.l. Geo_c<ta Rica und itere
-, rrit den Ho.n 1?athematischiz^.: gan,e XR 3.
und der Literz;ar.
:I lir.ts of vascular
Chapter
15
Mexicali Temperate Vegetation
ALEJANDRO VELÁZQUEZ
VICTOR MANTUEL TOLEDO ISOLDA LUNA
S74
A.
Velázquez,
DIVERSITY AND NEARCTIC AFFINITIES
Mexico has a high diversitv of ecosvstems iRamamoorthv, Bye, Lot, and Fa 1993). Mexico includes
six oí the ten major terrestrial biomes oí the world
-extra-drv vegetation, mediterranean, temperate
forest, temperate grassland, montane, and tropical
rain forest (Cox and Moore 1993) - and it is one of
the ten most megadiverse countries oí the w'orld
(Mlttermeier 1988), harborirg 10-12% oí the
world's vascular species (Toledo and Ordoñez
1993)Mexico's vide elevation range (0-3000 rn), its
location astride the Tropic oí Cancer, and the influence oí two oceans across its reiatively narrow'
continental mass probable are determining factors
for the most significant features oí Mexico's climatic diversity. The Tropic oí Cancer is a significant therrnal demarcation and also deli.-nits the
transition between arid and semiarid climates
arid anticyclone high pressures toward the north
versus humid and semihumid trade winds and cyclones in the south. The complex ph\siography,
together with the differences determined by latihude and altitude, result in a climatic mosaic with
a great number oí yariations (García 1951). Maximum average temperatures (288-30° C) are recorded in the low-hing regions oí the Balsas Depression, w-hereas adjacent zones at -he top oí Pico
de Orizaba in Veracruz hace the iorest average
temperatures (-6' C). Some mountains Nave glaciers and permanent snow. Apart from these tw•o
extremes, the range oí temperatures most frequently recorded caries from 10 lo 2S° C. Precipitation also presents notable contrasts: from <50
mm annuallv and no wet season (as in parts oí
Baja California) lo >5500 mm annually and almost
no drv season (as in parts oí Tabasco and Chiapas).
As a consequence oí this climatic diversity,
Mexico has a largo variety oí vegetation types,
comparable only lo India or Pena. Altnough detailed studies haye distinguished up to 70 different
units of vegetation, based on phy'siognomc and floristic composition, it is possible to differentiate
fewer principal tapes of vegetation in Mexico at the
biome category (e.g., West 1971; Rzedow ski 1978,
1993; Flores 1993). At such a scale, it is apparent
7har.ks lo Martha Cual and R. M. Fonseca for support
en floristics. Comments by Jorge Llorecte, Javier Madrigal, and Richerd Minnici on an ear!y iersion, and bv
>tichaei Barbour on a late' version, are acknow!edged. J.
Rzedowski fully encouraged the preparation oí this chapter, and it vas further supported by a grant-in-a.'d from
DGAPA-GN.AM grant IN-209094, and FGO's Universiw
of Amsterdam.
V. M. Toledo and 1. Luna
Temperater
1 egetation
that Mexico mar be divided relatively easilv. Fin
ure 15.1 shows the distribution oí the main vegetation tepes oí Mexico as a function oí two clima tic
attributes: precipitation and temperature (the latter
is represented by eievation in the figure).
Although mane Cosmopolitan and Paleoarctie
taxa are present L-i Mexico, its geegraphic location
has favored the establishment cf hiotic elements
characteristic oí %vo main regions, Nearctic and
Neotropical. Mexico is si;uated un a transitional
,; adient from Neotropical to Nearctic environmer,ts.
A large part oí Mexico is dominated by ecosv°terns oí northem af fiiiation (Beard 1944; Rzedowski
1978). Two main historical events may explain the
present dominarce of arctic biota: (1) most oí Mexico's northem territorv has been linked permznen;k lo the rest oí North America, and (2) the last
glaciation (ca- IS,000 Nr ago) promoted the moyement south oí .mana northem taza within Mexico s
present political horders (Fe:rusquia-VÜlafranca
1993; Velázquez 1993:.
Temperate vegetation tvres on long north-south
mountain chains tcpifv Mexico's arctic affinities.
The Madrean Region from no7inem Mexico south
through the Xeovolcanic Transversal Belt lo Las
Cañadas de Chiapas is dominated by oak, alder,
p:.ne, and fir species. The absolute dominance oí
species oí Nearctic origLn che tree iayer and a
large number oí species oí Neotropicai origin in
the shrub and herb layers is commonly obsen'ed
(Gadow 1930). T,tic compiex ceeetztion patiem becoma more dominated by the Neotropical to the
south and bv +-he Nearctic lo tE:e north. T'ne Neocolcanic Transversal Belt tenis the heart oí the
gradient, and it contains a lame number oí endemic taxa (Fa 1959; Rzedow.wski 1993).
Data from a lar ge nuniber oí botanical and zoological expeditioti throughout tñe present centun
provide strong evidente oí `e great affinity of
montane regions of Mexico wi:h the rest oí North
America (Beard 1911; Goldman and Moore 1945;
Srnith 1940; Troll 1952; Wagner 1964). Structural
classficatiors oí Mexican vegetation tupes equated
temperate ecosvstems •.with mountanious regions
(Sanders 1921; Shelford 1926). Temperate montan e
vegetation tepes pave ra-ieusl;- been called (Table
15.1) montane raLn. forest, high m
.ountain forest,
and páramo (Beard 1944; Braman 1962); pine-oak
forest (Leopold 1950); low e.erreen forest, conifer-oak forest, oak forest, and :-,amo (Miranda
and Hernández-X. 1963); and mest recent!v cloud
montane forest, cornierous forest, uak iurest, and
grassiand (Rzedowsski 1978). Research that defines
the relationship oí these vegetation tapes lo ecological facters such as humidity, ssoil suitabilit',
5000 -____-___
2000 -__
i
:000 --TRi
e
I
3000
Hvperhumid Hu:
Figure 75.1. Maior.M,exka
a!ong gradients oí tempera:
rainfali in mi!!imeters). Abb
(TRF), subtr-oical caduciró
tbbus iorest T(1F), shrublan
Table 15.1. Equivaleni r
tarious authcrs
Beard (i 955) Herr
Montare rain iorest Deci(
.Montare iorest Pine
Páramo Alpin
Source: Rzedcvrski. (1978).
fire, number oí days w'iti
and mean anual prec:
scanty or restricted lo sr
initions oí temperate -\le
eeer, Nave been ¡nade
and Ordoñez 1993). M.
matic ecoregions are the
humid temperate, and
15.2).
3 and I. Luna Temperare l'ege:ai;on (Mierico
575
v easily. Figmain vegen,o climatjc
cre (the latter
_.e).
Cold
:d Paleoarctjc
spic location
5c elements
_ .carctic and
a trans_itional
rctic environ.
Semicold
Températe
Températe
ted by ecosvs1; Rzedosyski
ay explain the
:m,ost of Mexinked perraaand (2) the last
ted the moveaitin Mexico's
uja-Villafranca
ng north-south
rctic affinites.
Mexico south
sal Belt to Las
by oak, alder,
dom
,Lnance of
ce layer and a
pical origin in
ronly observed
ic n pa ttern be'cupical to the
crth. The Neoe heart of the
,.umber of en+3).
nical and zooresent centnrvv
eat aff ruty of
Test of Nonh
3 Moore 1945;
64). Structural
hiles equated
:nious region
erate montane
n calied (Tabie
,untain forest,
962); p,e-oak
n forest, coniamo (Miranda
recently cloud
,ak forest, and
;h that defines
types to ecooil suitability',
Sem v arm
\Yarm
\'erv \1'arrn
Semiarid Ard Hv^perarid
Sub.hum d
Hvperhumid F. =d
Transition
Trarsidon
Figure 15.7. Major Mercan vegetation ;upes ordir,ated
alon;S g^adien.s or ;erPper arare and precipCation (anm:al
rainiall in milümeter<i A±brevi tions tropical ruin tares;
(TRF,t subtropical caduc;rolius [ores; (Sri, tropical caduci-
(SAG), t.homshwb (T5), oak lores; !OF', cloud forest (CF),
rir [ores; !FR. pine lorest (PF), and alpine grassland (A C).
The nical zone is IC. (Modified rrom Toledo d RzedoHSki,
1995.)
[ollas [ores; (TCFh shrub avd íA, subafpine erassiaad
Tab'.e 15.1. Equ[va!er„ carnes ci ASexican :enoerate s ege'a?ion rypes ,iver, by
varicurs authors
Toledo &
Miranda &
Beard (1955;
. ernandez.X . ; 1963)
ntontane ram lorest
D eciducus lorest
.Montare forest
Páramo
PI^-e-ilr lorest
- .or ne bun..cir grass!acd
Rzedo,ski ; 19781
C:'ou ores;
Comer lorest
'taca;on.al"
Ordoñez;1993)
Hurnid temperare
Subhunid temperare
Cool temperare
Source: Rzc Jowsk;, t19-2:.
fire, number of daos -.,:th temperatures below teto,
and mean anual precipation is, on the schole,
scantv or restricted to specific places. General definitiors of temperate Mexican environments, hos+ever, hace been made (Rzedowski 1978; Toledo
and Ordoñez 1993). Major temperate biogeoclimatic ecoregions are the humid temperate, the subhumid temperate, and the cool (or alpine) (Fig.
15.2).
Tre humid temperase repon is characterized by
cloud forests dominated by oaks. Tse forests' tloristic composition includes beth boreal and tropical
elementü. This region nccupies yery restricted sites
of 600-3200 m elevation, mainly on slopes facing
the Gulf of Mexico from Tamaulipas tu Chiapas.
Distrbuted in 21 states, it covers an atea of approximateiy 10,000 km'.
The subhumid temperate region covers the
576
Temperate Vegetation
.4. Velazquez, V. . M. Toledo and 1. Cuna
0 2).
Figure 15.2. Climatograrx representad; e of thr ee nain ele'a:ion befts or nountain environmernr temperare humid
(Tlanchinoli, temperare subhumid iEl Guarda), and tempera:e cool :Hueuedaco). Months Jancan-DecemSeri are arranaed along the horizontal axis, mean monrh„S remperature along the lert rerlical axis, and monrhly p-ecipiration
greatest parí of the mountains of Mexico at elevatiotu of 2500-3000 ni. The characteristic vegetation
is forest of fir, pine, oak, or mixtures. It s distributed through 20 states (principally Chihuahua, Michoacán, Durango, and Oaxaca) and covers an area
of approximately 3_3,000 km'.
The cool (or alpine) region is located aboye timberline (>4000 m) on the 12 his,hest mountairs of
Mexico. It is dominated by alpine bunchgrasses, or
zaca tonales.
GEOGRAPHICAL DISTRIBUTION
OF TEMPERATE VEGETATION
Mexico is a ver, mountainous countn,, with over
half of its territon- >1000 m in elevation. Arid and
semiarid vegetation dorninates the high plateau of
central and northern Mexico, whereas temperate
vegetation (as defined in this chapter) covers the
steep and more humid areas ahoye 1000.n. Temperate vegetation thus covers 2200 of the Mexican
territon•. Mexico is also a countn- with evidente of
past volcanic activity. The most spectacular volcanic area is the great Neo;olcanic Transversal
Belt, which crosses Mexico from west to east at the
latitude of Mexico City (19-204). its landscape is
characterized bv thousands of old cinder tones and
dczens of tal) volcanic peaks (Fig. 15.3). Volcanism
continues todas', with many active or temporariiv
dormant volcanoes.
Earthquake activity is common, mostly along
the Pacific Coast and the Gulf of California. Earthquakes are also frequent in the Neovolcanic Trans-
along tne right verical axil. F'e Bical shading represe,-'s
soi1.rnoisture recharee ; solid srac,nc reoresenr$ precipi:ation bevond soil smraee caoacn, and doned shadi, represe%-5 soil mo .ivu: e derlc;r. Pa, ;Sienta) ir,rorma:/on is e,
e'a:ion, mean annual tempera:cre. acd an.- jzl
precip;:arion. Cii.ma:ic data a,e a' ere; es or :930-1990.
verse) Belt, often ca ❑sing considerable damage in
this heavily populated region.
Mexico can be divided finto five general rea':ras:
ext-atropical dn'lands, tropical highlands, tropical
lowlands, extratropical l gF.lands, and subhumid
lowlands (STest 1971). Diese realms match most
Mexican phvsiographic regions - Lar exampie, the
Baja California and Buried Rarees of northwest
Mexico, the western and eastem Sierra Macires, the
Neovoicanic Transversal Be!',, and the Highlands of
southem Mexico. Four repon q are considered temperate: the western Sierra Madre, the eastem Sierra
Madre, the Necvolcanic Transversal Belt, and th,e
southem Sierra Madre.
ic westem and ezstern Sierra Madres forra
dissected borders of the;vestern and eastem, edees
of :he central piateau. The croad crest of the western Sierra Madre vises up to 3000 m. The upeer
portion of the range is covered with thick lavers ef
lava. The western slope of -,he range forras rueged
can\ons and narrow ridges dropping down to the
Pacific coastal plain. The eastem Sierra Madre rises
to a sharper crest on the eastem rim of the central
piateau, with elevations up to 4000 m. In the
North, the Sierra is comprised of severa; irregular
ridges separated bv baria descending graduaily to
the Golf coastal p lain.
Tne Neoyoicanic Transversal Beft forms a maior
geological break ;, ith the central plateau. The belt
is hnrdered en the north bv a series of high bas:nS
on the south the )and drops sharply mito the drrr
Balsas Depression. included in this volcanic area
are Mexico's highest and best known peaks: Pico
Figure 15.3. o gital eles
me Vallev of México ' e:
de Orizaba (5700 m),
cíhuati (52S5 m), and
The Highlands o:
logically complex re
tions b'c the Isthmus
Sierra Madre in the
;ande in the east. ??-.
highly dissected mu
vailevs, a discontinu
a few highland basin
are dcminated bs- tl-,
teau rising up to an
These regions oc
Coahuila, Nuevo Lec
Luis Potosí, jalisco, c
Distrito Federal, Pu.
choacan, Oaxaca, ar
tened regions in the c
species: high elevatic
Baja California Sur, C
erra Fria in Aquasca
Sierra Lacandona aa
MAJOR TEMPERAT
VEGETATION TYPI
}
The four major ter^p
ico are comp^xd
(s,,:su Rzedow 'ki
Beard 1941 and Brau
can classifications ar,
laven and at ihe gene
phasis masks consic
leve). Fir forest (.
577
Temperate L'egeiation of ,\lexico
Digital £1"ation Nade]
Ajusto ( 3990 s)
Fi;ure 75.3. Dita! eleuaon model or southern portion o7 crea oi 805 kr are >J00 vo,'caric eones. From Velázrhe Vallev o México ;vericel exagaeration 3x:. )vithin Ihis quez 7993.)
7990.
.' dam age in
_._ral reair^s:
ropical
..;, subhumid
_ match rnost
epa-:ple, the
cf northwest
7a Madres, the
e Hi^iilands of
_r_.dered tem,e_stem Sierra
1 .,_.., and re
.ladres forro
cartero ed-_es
st cf tire westm. The upper
.,ick lavers oí
_ orms rugged
g do••Vn to the
ora Madre r,ses
.. of the central
:33 m. In C,e
.coral irregular
ng gradua„\ to
t forros a major
'.ateau. The belt
of high basins
v finto the deep
s co!canic area
n peaks: Pico
ce Orizaba (5700 m), Popocatépetl ( 5.1=2 m), lxtaccíhuatl (5255 rn), and Nevado de Toluca (4392 m).
The Highlands of southem Mexico are a geologically complex region separated oto hvo sections bv the isthmus of Tehuantepec : 'he southem
Sierra Madre in the west and tire Chiapas Highlands in tire east. The southem Sierra Madre is a
highly dissected mow,tain svstern w'ith narrow
vallevs, a discontinuas Pacific coastal plain, and
a few high!and basins. Tire southeastem highlands
are domi:nated by tire altiplano of Chiapas, a pieteau rising u,,- te en ele\ation of 2500 m.
Tpese regio.r.s occur in Chihuahua, Durango,
Coahuila, Nuevo Leon, Tamaulipas, Zacatecs, San
Luis Potosí, jalisco, Guanajuato, Hidalgo, Mexico,
Distrito Federal, Puebla, Veracruz, Morelos, Michoacan, Oaxaca, and Chiapas. Sorne other scattered regions in tire country also harbor temperate
species: high elevations of Sierra de San Lazaro in
Baja California Sur, Cerro Potosí in Tamaulipas, Sierra Fria in Aquascalientes, and high e.evatior<of
Sierra Lacandona and las Canarias in Chiapas.
1tA)OR TEti1PERATE
VEGETATION TYPES
Tire four major temperate vegetation upes of Mexico are comprsed of many plant comrtunities
(ser;e;r Rzedowski 1978) or associations (sensu
Beard 1914 and Braun-Elanquet 1951). Most Mexican ciassifications are purely based on tire canopv
layer and at tire generic level (Tabie 15.2). Tnis ernphasis rnasks considerable variation at tire species
level. Fir forest (A.cies), for instante, occurs
Tahle 15.2. Chzracreri;tic eecera or the Tour majo
temperare vegetar:on rape; o7.tfexico. ;hese genera
mav van' iro.m slooe :o sfone and moro sierra to
siena, so thar no single genus can be round
:hroughout a single temperare +egetation rype.
Cloud
Gene a
a^^<
t'.ein.vu.n,nia
forest
Pirre
ic'est
Y
X
x
Liquidaabar
x
Acer
x
iüa
x
Aluhtenéerla
ti
Ribes
x
x
x
x
He:e-ia
x
Cier^NJm
x
Roícana
3odd!eia
T udwm
Sh !ro pia
S2iz
Cirr:a
Srmphoricarpos
Alplne
grassland
x
cr.=e.tha«1:ia
Celos
Bacchariss
Fir
forest
X
X
x
x
x
x
x
Ca!amagros:is
x
A^roslis
x
Ttiselum
L'.mbilica ria
Bry oepihrophyllum
Siereocaulon
Cladonia
x
X
X
X
X
5 78
throughout Mexico, but co-dominant shrub species
and fir species change from north to south (Velázquez and Cleef 1993; Islebe, Cleef, and Velázquez
1995). Only a few phvtosociolodca] studies have
been conducted in central Mexico, sufficient to define associations and alliances based en fine-scale
differences in species..Another limitation to our
ability to summarize the vegetation is that a large
part oí the territorv where temperate vegetation
types are distributed has not been sun eved in detall. This lack oí homogeneous informa tion does
not permit us to provide a thorough description oí
al¡ communities. Thus a detailed description oí
temperate vegetation is beyond the scope this
chapter.
Our objective is to provide an ovenview oí major vegetation tepes and to emphasize those tha;
have been best studied. We also intend te outline
the consenation possibilities for temperate vegetation in Mexico. Additional details on the vegetation oí Mexican forests, grasslznds, deserts, alpine, and wetlands are found in Chapters 3, 8, 9,
13 and 14 oí this volume.
Cloud Forest ( Humid Temperate Forests)
Large biological heterogeneity t-pifies a cioud forest, which is a mix oí northem, southem, and endemic taxa , and oí ]ow- and upper-elevation laxa.
Because oí its diversit-, various .-.ames have been
given to Lhis vegetation tvpe; bosque mesófilo de
montaña (Miranda 1947), caducife'ious forest (Miranda and Hernández -X. 1963), temperate deciduous forest (Rzedowski 1963).
Five environmental requirements seem to govem the presence oí cloud forest Li Mexico: high
relative humiditv, montarte en;ironments. irregular topography, Jeep litter laye:, aad temperate el¡mate. Cloud foress covers at most 1% oí the total
Mexican surface, but it includes about 3000 vascular species (Rzedowski 1993), which is 12% oí the
countrv's vascular flora (Toledo and Ordoñez
1993). Currently, there are only a few large preserves oí cloud foress but thev are scatered
throughout the range oí the tepe.
Aiong an elevation gradient, the structural complexity oí cloud forest decreases totvard high e'.evations and varíes from slope te slope. Elevation
ranges from 600-3200 m, though trae vegetation a
best developed at 1000-1750 m. Precipitation :s
IS00-5500 mm }-r', and doudiness is commo;t
throughout the year. Freezing temperatures are
rare. Major temperature changes are seasonal, in
contrast to large daily changes un alpine environments at higher elevatiora.
A. Ve!azquez, V. M. Toledo and 1. Luna
Phvsiognomically, cloud forest is dense, 15-40
m high, and multilayered (Fig. 15.4). Some oí the
tree genera that reach more than 40 m are Engeihardia ard Pi.^.tanus. Tne upper free la}•er is dominated bv caducifolious (deciduous) taxa, the lower
tree laver bv perenrüo!ious (evergreen) ones. The
most diagnostic species is Liquidmnhar rnncnephu:'.:
(see Fig- and the most common associated
boreal elements are Ca-vinos caroliniar.a, Cornos disnjlora, Ti! mexicana, .4.'nos f, rn:yfolia, and Qnercus
car;dicros (Miranda 1947; Puig 1970). Some species
shared rvith the eastem deciduous forest oí North
America are Acer r:egundo, Carpinus carolinana,
Carca orcta, Cornos onda, Fagus mexicana, lllici:un
^9oriu'.aruat. Liquica.n:ber nz:rophy!la, Nyssa sylt'afica.
Oshva -i•cir, irisa, Pra:us serotina, Ti!ia foridana,
and Taxurs globosa. Species shared with western (oíten riparian) foress are Arsu:us xa!cpersis. Cei:is
pailid C. ret:cu!uta, and 5„mbucus mexicana. Mesoamerican Laxa f:eeuently, foud in cloud forest are
Clet!:ra spp., l"+eir:n:a; ✓ :: spp., Arctataphvlos argufn,
Ilex discokr, Litsen gia c scens, Magnolia schiedca nt,
Pinos :r;ontezun::.e, P. ps:udestrobos, Prunus brachyhotr✓a, arad Uimus mexisma. Among the endemic
taza are Canco eruta var. mexicana, Ilcx pring!ei, Juglans mol!:s, and P!atanus mexicana (Rzedowski
1978).
Commonly, there are wo shrub layers, both
with Neo:ropical al les- T,.e families Compost
tae, Gesneriaceae, Ciusiaceae, Labiatae, Legurninosae, Malvaceae, Me astomataceae, MyrsLnaceae,
Piperaceae, and Rubiaceae varousiv dominate, dependLng en elevation, !atitude, and humidity.
The herb laver Lncreases cover and diversitc
when the oversto:v is disturbed. Arboreal fems
(e.g., Cya:%rea) are comnion, as well as herbaceous
species. Mosses are aba-ndant. Flowering piants are
in the fzmilies Asclepiadeacea, Begoniaceae, Bromeliaceae (especialls' the genus Tillandsia), Cvperaceae, Compositae, Convolvulaceae, Cucurbitaceae, Dioscoriaceae, Equisetaceae, Gramineae,
Liliaceae, Lvcopodiaceae, Orchidaceae, Piperaceae,
Solanaceae, Urticaceae aad 1'erbenaceae. This ]ayer
has a Nectropical afí n-:, :.ith only a few rnosses
and mushrooms be", ci boreal afiinity (Crum
1951; Guzmán 1973; Delgadillo 1979).
Pine Forest (Subhumid Temperate Forests)
Mexico contains about naif oí the 1, orld's pire species (Critchfield aid Little 1966; Shles 1993). in
mu,i arras pino forests are co-dominants with
other broadleaf trees (AL;us and Quercus) and other
conifer species (Abies and Juuipen:s). Collectiveh
they, cover 1596 oí Mexico: on sandy soils of coastal
Temperate t
<
lag --
plains (Pinos
michoacmrus, ,'
(P. hartwegñ),
15, C- 10)a
not seem te
ment oí pine
sociated with
Hernández 19
Rzedowski
disturbance i^
of conifers, b,
shown that
succession tm
study is n =edc
grazL 0 en pir
fleco and 1. Luna
Temperare Vegetation oi.Mexico
579
is dense, 15-40
Some oí the
m are Engel_e laver is domi) tasa, the lower
,,creen) ones. The
,,tbar mr<crophypa
nmon associated
1 tia ra, Cor,;us dfsand Quercas
Some species
s forest of North
6:us carolfniana.
-ruL'xicmm, illiciuru
NyEsa sul:'atica,
Tilia floridana,
+ith westem (of,.. apersis, Ce;ris
_ a:exicano. Meso7, cloud forest are
. os tapl:ylus arguta,
?cro!ia sczicdenna,
?ranus brachuong the endemic
I:ex prir:giei, jugara (Rzedowski
:n b lavers, hoth
amilies Composiabiatae, Legurnieae, Myrsinaceae,
:s!v domínate, dend humidity.
per and dicersity
J Arboreal fems
ell as herbaceous
wering plants are
3egoniaceae, Bro'd:anisia), Cvper:eae, Cucurbitare, Gramineae,
cene, Piperaceae,
acere. This laver
nlv a few mosses
i affi dty (Crum
,79).
ate Forests)
sorld's pine speStvles 1993). In
-domL,ants with
uercus) and other
-ia). Collecñvely,
'.v soils of coastal
FI, ure 15.=. Asoect oí cloud forest at
encelo anea (2600 m). ICounesy oí
1. L. Convexas)
plairs (.Pü¢us car:b..ca, P. oocarpa), en lava flo•.+s (P.
michoacanus, P. *..-..,e.urrac), and at high elevarions
(P. kartaegif), (Rzedos+ski 197S). Temperature (ca.
15- C = 10) and precipitation (S00 = 150 mm) do
not seem to be .actors for the establishment oí pine speces. Acid soils, how+wever, are associated with pine íorests (Aguilera, Do,,', and
Hernández 1962).
Rzedo,+'ski and v?cVaugh (1966) state that fire
disturbance in pire forest favors the establishment
of corifers, bu t Sa ..chez and Huguet (1959) have
shows that fire, loó ing, and grazing induce
succession toward pine-alder-bunchgrass. More
studv is needed to document t-he e.`fect of fire and
grazing on pine forest (Velázquez 1994).
Major tupes of pine forest inciude alder-pire,
ponderosa pire, pine-oak, Hartxeg pine, and
mixed pine. Each is described in the following sections.
Alder-pne forest. Alder-pire forest is made up of
four structural lay.ers: (1) coniferous tree layer (50%
cc.ver, masimum height 22 m) of Pinus: (2) sh,-ub
layer (4 m height) of Alnus `nnifolia, Senecio cinerrricdes, and S
(3) dense
burchgrass ]ayer dorninated mai.nly by ,,luhlenbcrqia nmcrcur a and Frstaca tolucensis; and (4) ground
layer componed mairly of Alcheudlia pronm:bens
and Arenaría lycarndic:d s. The bunchgrass )ayer is
characterized by compact bunchgrasses -,+ith
580
A. Velazgoez, V. Al. Toledo and 1. Luna
Temperate Vei
Litsea glnucesc
laver. 'Ylidstai
mentioned, bt
are more dom
sir and 5,un:pic
Cure stage is
laur;na and Q
single species
dant subcanr
(Gonzáiez-Ese
phase is one a.
dominated by
understory (th
depends stron
Intensive r
comrnon in t.
bun agriculh:
ited, mainly a
Pinus hartwegh
scribed this
poor. 11, is mai:
pedregal lava
rather flat ut:;
330373 me
(1 m) are loam
Figure 73.5. Aspect oí pine íorest at Tláloc volcano (3300 m).
broad, long, tough grass leaves that seem to be
,veil adapted to fire and browsing (Fig. 15.5). The
íorest is restricted to ver] dissected, rol'.ino toeep slopes, and lava flo,vs at 2700-3500 m elevation. Soils are shallow i+ith grave'}- sandy loam
texture.
Constant diagnostic species include Alims frmi,`clfa, Arhutas glanduloso, Buddleia pare?ora, Ery»gium carlmae, Pere cn;on ge»tiarcides. P. campar:+Iatus, Pivus monte:Inliae, Qt4'rcus r;urina, Sicyos
1,ar,'ij7erus, Stellaria cuspidata, and Striu nm»arditblis.
Cervantes (1950) and González (1952) described
this ttpe of mixed forest, and Rzedowski (1951,
1975) referred to it as a mosaic of Air::rs finni olía
forest and M;dacuhcrgin gandridentata , assiand and
suggested that repeated buming and grating are
the main causes of the bunchgrass. Disturbed conifer forest in some parts of central Mexico is replaced by alder forest or by suba!pine coarse
bunehgrassland of .\hdiler. bcrgia and Festuca.
Velázquez and Cleef (1993) desccbed four associations ivithin alder-pine forest in central Mexico: Trisctunt alti];i um-Ahlus Frmifoi:r. Pinus-A6:us
fr; folia, Ervngiunt cr. rlinae-A.bu+c, ün :fol(o, and Pi. 77m7ife:unce-Al::us Jtrmi^ólia.
Pinus ponderosa forest. Ponderosa pine is chieflv
found in the western Sierra Madre ori granitic or
volcanic steep slopes or plains at 1021500 m elevation. Fires are frequent. Ponderosa pine dom:
nates large stands, are citen mixed ,vid:
Abies cor;cnlm. Studies of :...- forest's distribution
and d,-namics are scanty in con trast to many
publications about it in ti-e Urited States (Styles
1993).
Pirre-oak Forest ;Pinus oocarpa-Quercus aurina). .\lost landscapes at high elevations (23002i00 m) of Chiapas are covered by pine-oak forest
in sorne stage of recocerv from disturbance (1\'agner 1964; González-Espinosa et al. 1991). Onh' a
fe" patches of oíd-ero,v th forest remain. There are
no freezinng davs dur'ng the %ear. Soils are moderately deep (10 cm) calcarecus or clavey loaras
(Breedlove 1951).
Tnree seral stages - early. middle, and matare
forest - are apparer.t. At ec c stages, Pimis oocur;'a.
P. oaxacar:o. Quere2j9 Q. crass;fnlia, and Q.
rugosa prevail. Beio,,' the overstor' canopy is a ser
ind, io,,cr roe !:ccr i,,niinatei by Ra,anea ¡re,.
genserií and P: u :us serctira. Scla»urn 7igrica7:s and
The physio
layers: (1) an c
(2) a herb-bun
hergia. Festuca,
(3) a ground la
enana lucepec::
tbis forest are
qu.uiridentata; ::
Muhlenhergia
tuca tohrce»sis,
ter hvo bunchs
alpine grasslar
quez, and Lur:
The forest
layers, unlike
and Pelado yo'
,va,•s hace a de
is considered t
Em (1973), hoy
,vas a successic
religiosa forest,
alpine slopes a
gro,vs in a mal
i e_:rnu:e, and Q
.Haca, Nema:
boreal distriba
tains of Centra.
in Guatema!a's
eral plant coro:
••:üé v N:;.'.y;'n-eN '- .`..n '_6. -,
!'w+:^ i o+^ :-.i f 4 . :z
i% ni,'..
I. Luna
L!sca glaucescrns are abundant en the ground
laver. \•Iidstage stands share all the species just
mentioned , but pines are les i,r,portant and oaks
are more dorninant . In addition, Oreop „ i:az ^nlapcusis and Svnq'Iocos li noncillo are abundart. The matare stage is en oak forest don tinated by Quercus
laurina and Q. crass;fo'i a. Pinos are present, but no
single species prevaiis . CL-sera theaou'es is ara abundant subcanopy free. Shrubs are chiefiy abre,,^.t
(González-Espinosa et al. 1991). This pme-oak seral
phase is one of the best examples ef a canopv ]ayer
dominated by Holarctic species with a Neotropical
understorv (though the degree to t.+'hich this holds
depends strongly en geographic location).
Intensive grazing, cepping. and logging are
common in the Cañadas of Chiapas - Slash and
burra agriculture for coro productien is more .'imited, mainly conducted bar indigenous groups.
Pinus hamvegii forest. ?tzedowski (1951, 1978) described this vegetation as being rather speciespeor. It is mainly restric:ed to the upp er part of the
pedregal laya slopes beiow co.'canic rones or te
rather fíat undulating slopes forming plateaus at
3350--3=70 m elevation. Trae relaiive'y >haüow• mis
(1 m) are loamv clays with a thin Iitter la, er (5 cm).
The phvsiognomv of this forest consists of three
lavers: (;) en ove,storv free laver up te 20 m high;
Z) a herb-cunchgrass ]ayer with
e is chieflv
anitic or
.500 m elepine domd-:ixed with
stñbut ora
,t te manar
:ates (Stvles
creas laurr;ons (230
e-oak forest
.anee ('^1ao
a
r:. Tbere are
are mod.avev loares
and matute
cocar:",
and Q.
opy is a sec:::;:,:rea
_;r:crrs and
581
Temperare t'ege!arion of ntexico
Sergin, Festuca. and Cala' :::;ros::s grass species; and
(3) a ground !ayer dominated by.5ldaonaia and Arenara lvcopodioides. The main dia_nostic species of
this forest are Pinas Ccrtm ezíi and A'u1.!enberg-,a
qundridn:'nta; importar., associated species include
..",Qad:lenbergin nuaaeura, .=:r:r:aria lar:opa:üo:.yes, Fe>tuca tciucensis, and Calara:•-mstis tc.t;ic,sis. The 5t
ter rayo bunchgrass species are also diagn:ostic for
alpine grassland f.Almei^a, Cleef, Herrera, Veláscuez, and Luna 1994).
Trae forest lacks -weil-deti.-:ed s,,. and herb
lavers, unlike the Pin:,s i:.r;avri€ forest en Tláloc
and Pelado yolcanoes Ln central Mexico, which alw-a ys ha,.e a dense herb :a ver. Pi ': us 'ss r;;rc; ii f ores t
is considered by most te be a clímax community;
Em (1973), hotvever, s-a _,ested that P.rs:c rsrttrrgii
was a successional species in severel'y bu:ned AFies
n^'r^:bsn forest, a forest res::leed te yen. steep subaipine slopes at 2900-:23-0 m eleyation, and which
nmngro'.+s ir. a matriz tyith
and Qacrc:s /eres: (Pvede'.vski ;954, 1975;
.Anaya, Hernandez, and Madrigal 1980). Tne least
boreal distribution of FM C5 reaches high mountains of Central America arad are best represented
in Guatemala's mountains (Islebe et al. 1995). Several plant communities paye been identued asso-
ciated with bunchgrassland dominated mainly by
,Liulvler.ber,lia ^ruadridenL^!a or Festucn tolucensis.
Rzedowski (1975):eferred te these bunchgrass species, together with C.aL:.niagmstis tolucer,sis, as yen'
abundant associates of Pirms l:artwegii forest.
Evidence of recent buming and grazing (mainly
by sheep) is found in most aseas of this communitv. Wood extraction in central Mexico is practicaliv absent, though in Guatemala ordy a few
patches of this forest remain, due to the intensitv
of fuelwood cutting (Islebe 1993).
,vtixed pine forest. There are a number of large
forested aneas where no single species of pire
seems to be dominant. Such a complex pire unit is
apparently promoted by intensive logging practices and by fire. It occurs in very heterogeneous
landscapes that include flats and steep slopes. Soils
are shaiio'.v, acidic, and sandy. Often, there is recentii, deposited Nolcanic ash or lava (e.g., in the
Paricutín volcano area and other portions of the
Tran versal \eovolcztic Belt). The lava flows hace
en irregular topographv, which produces a diversity of microenvironmental stuations with many
endemic taxa.
Within the 40 m tal) overstorv are Piras nlicimacarsa. P. n:on!e:un:ac, P. lelepi,^ln, P. pseudostrobus, P.
riáis. P. t.'occ:e: and P. iar!:oegi;. A;rus and Quercus
species are present but w-ith less cover than Pinus.
The free canopv is open, more like that of a woodland than a forest. Beiow is en open shrub laver
with Senecto, BuddLfa, Rfbes, and Rubus as charcoteristic genera. The loivest understorv laver
contains Satureia, Stcria, Euyaforium, Salvia, and
cushion-like species such as Arenaría tiroides,
Geranrum seenrar.ii, and r.Id:cn:i!1a p rocunibe?:s. A
defínite bunchgrass laver is absent.
Fir Forest (Abies)
The rnost boreal Mexican yegetation tupe is Abies
forest, variously and locally described throughout
Mexico bv Leopold (1950), Rzedow•ski (1951), Beaman (1965), Anava (1962), Madrigal (1967), and
?,nava et al. (1980). Rzedo•,c ski (1975) has ó ven a
complete description on a natior.al scaie. Fir forests
t ricall% occur helow Pie:-s l:.v! a e;ü forest en high
yolcanoes, along escarpmenrs, and in giens betv een laya floi,'s. T.nec pret'er canyons or other
steep slopes protected from direct sunlight and
strong winds. Soils are rich i-n organic master and
ash.
1hree fir species uccur in Mexico: Abies corcolor,
A. religiosa, and A. gua!rralensis. They usually cooccur in the overstorv with Pimrs, Quercus, Pseu-
582
A. Velazquez, V. Al. Toledo and 1. Luna
Temperate Ve;
i
dotsuga, and Cupressus species. A lower free layer
is comprised chiefly of Alnus, Arbutus, Salix, Prunus, and Garrya species. In rare undisturbed stands,
there is a ground layer of mosses and cushion
plants.
T.he Abies religiosa forest is mainly restricted to
the Transversal Neovolcanic Belt. It occurs on steep
to moder ate (10-30`) outer slopes of volcanic cones
at 3000-3500 m elevation. Soils are deep and there
is a thick laver of Iitter on the surface. Some evidence of disturbance from grazL-ig, burning, loa
ging, and Cree harvest exists (Madrigal 1967; Rzedowski 1975).
The forest is dense and tal], reaching 30 m in
height (Fig. 15.6). The overstory ]ayer is dominated
bv A. religiosa. Below is a ]ayer of shrubs and tal]
herbs (0.5-3 m), dominated by Senecio angal folius
and Roldana barba-jolutnnis , and a ground layer (5
cm tal]) of rosaceous herhs (e.g., Alchemilla procumbens) and mosses (e.g., Polytrichum juniperir:um).
Other diaglostic and common species of this
plant corrmunity group are Ser:ecia toluccanus, S.
eallosus, S. platnn folius, Sihthorpia rrriens, Salix ox;leps, Festuca amplissima, Alchemi!!a procun:bens,
Thuidium delicetvlum, Acaena elongata, Stachvs species, lolium species, Galium, aschenbc nif, Cinna poc:e;ormis, Pernettya prostrata, Dydimaea alsinoides, and
Buddleia sessilijora. At lower eievations Chis forest
mixes with Mulilenbergia and Calamagrostis grassland and A!rus ^5rm,fotia forest (Velázquez and
Cleef 1993).
The Abies guatemalensis forest is mainly restricted to the southernmost part of Mexico and
into the Guatemalan mountains (Islebe et al. 1995).
It occurs on verv steep slopes at 2500.3900 m on
deep soils rich in organic matter (Islebe and Velazques 1994; Islebe et al. 1995). It is a dense forest
with three layers: an overstory fir layer 30 m tal¡;
a shrub layer dominated bv Roldana barba-johannis
and Tetragyron orirabensis; and a moss layer dominated by Thuidium delicatulum. Ot-her species present in this forest include Fuchsia microphy:'la, Senecio
callosus, Trifollunr amabile, Sabazia piretorum, and Pinus '
l n Mexico, there are no communities where
Abies concotor, the other fir species, is dominant. It
alwavs occurs mixed with ponderosa pine. At Sierra San Pedro Mártir, in Baja California Sur, Pinus
ie eyi coexists with Abies concolor as part of other
mixed forest communities (see chapter 5 of this
volume).
Alpine Bunchgrassland
Mexican alpine bunchgrassland is dominated by
tussock grasses restricted to steep volcanic slopes
at elevations aboye timberline (ca. 3800 m; Fig.
15.7). It has been studied by a large number of researchers throughout this centurv (Standley 1936;
Beaman 1962, 1965; Cruz 1969; Delgadillo 1987).
Beaman (1962, and 1965) called this vegetation "alpine prairie ," w'hereas \ 8randa and Hernández-X.
(1963) related it to .-ondean ecosvstems and called
it "high páramo." Almeida et al. (1994), however,
believed that the urique composition of Mexican
alpine regetation mide it different from the actual
páramo. Rzedowski (1975), in ap eement, treated it
as a separate vegetation tupe, which he called "alpine zacatonal."
Alpine bunchgrassiand cornmunities occur in six
main high-mountain formations: Cerro Potosí, Nevado de Colima, Nevado de Toluca, Sierra Nevada,
\4alinche volcano, and Pico de Orizaba volcano. No
svstematic survev has described asid compared
these communities. Recent surveys conducted at
Popocatápetl (Almeida et a;. 1999), lztacdhuatl, and
Nevado de Colima voicanoes rrovide a li-nited
surrunarv cf Mexican alpine ecos%stems. Near the
low'er lirnit, in tse }ic t of Pinus hart-u'egii forest,
Lupinus mo':,anua, Festue. tchrcer:=.., Calamagrostis
tohucensis, Per:aten=ion gentirnicdes, and Descarair:ia
impatier:s are the mest common species. These are
considered the diagnostic species of zonal alpine
communities . Arrizaría ovoides and Juniperus monticola tvpify the azonal aipLne cornrnunities. Near the
upper rival bordee mosses and lichens do=ate
(Bartran :ia and B: roe✓throphyl'urn). Intensive grazing asid fires are fast depleting these alpine ecosvstenrs . Tris vege:aticn also harbors a large number
of ende:rvc taza. Des ite the smail area covered bv
Mexican alpine b unc'r.gr-ssland (0.02% of the whole
countrv), five zonal and b.vo azonal plant associations (sensu Braun -Bianquet 1951) have been described by ALmeida et aL (1994).
In the southem mcuntains of Mexico, at the bordar with Guatemala, diere are smail patches of alpine grassland dominated bv Lupinus mortanus
asid tussocks of Calamagrosts culcar,ica up to 1 m
high. There is ¿!so a ground '-ver with mosses
such as Breu''elia asid L ptoda:ti;an. Other cornmon
species are Luzula -acrorosa , Agrostis telucensis.
Draba r:dcanica, Arrn.:r.'a b soldes, Graphalium srliiciloiium, and FoL^::,•i; (a ;cteresep-ala. On rocky outtcrops, Raccmitriunr ^ü?;dum is dominant. This
southem alpiste kege:ation grow s on gentle, winiprotected slopes wüh regosois (Islebe and Velázquez 199:).
Fire and grazi:g are the majos causes of degradation of alpine bunchgrassland ecosvstem5 \1'hen fires are frrq.:eni, Lupi r.us rucrtanus becores
dominant. Hiking pat5 significantly fragment (:sisa
vegetation (Almeida el, al. 1994).
F..gure 75.6. ,..spe
and 1. Luna
Temperare Vegetation oí.
Iexico
,00 m; Fig.
r; her of re1936;
délo 1987).
don "al.. ,f:ndez-X.
i d called
of Mexican
.:he actual
r+ treated it
"al.Cctr in six
Potcsí, Nevnra Nevada,
vc lcano. No
3 ccmpared
cnducted at
ccir^atl, and
e a limited
ns. Near the
upe; i forest,
C:„-:arr:ag ros!is
Desnrra:ina
es. These are
zonal a!pine
F cure 15.6. Aso ct ol irt ;crest at Ajusco vo'cano 3 , 1OO.m).
..es. Near the
ns dominate
.ensive grazLne ecosys-
rge number
a covered by
of che whole
,!ant associa;ce been de-
:o, al the bor:at&es of al:+;arta,:us
uptolm
.,ith mosses
roer common
to!ucetsfs.
.a!iurn salir, rc+.KV out-
,ant. Ihis
:entre, :cindand Veláz-
❑ ses of dei
ecosystems.
: us becomes
:ragment this
Figure I5.:. Aspect oi alpine bur,chg ^zssland at Izraccihuad cclcano (4i0O m)
583
584-
Subalpine Bunchgrassland (Festuca
tolucensis)
Ibis community is mainly restricted to the fíat valley bottoms within vokanic craters at 3500-3550 m
elevation. Soils are very deep and nave a thick surface ]ayer oí litter. The community consists of a
dense layer oí bunchgrasses 50 cm tall, doninated
by Festuca tolucensis and Cnlan;atirestis to'ucensis.
and an open ,round layer dominated bv.A7dumilla
procun:bcns. Other diagnostic spectes are Poa annua.
Trisetum spicatum, Pinus mnr:fe_u:rae, Pinas
gii. Mu'ilenbergia quadridentafa, Muhienbergia aff.
yusiha, Oxalis spp., Sicvos yar;i.`,on+s, Potent:lia
stanunca, Pedicrdaris ori_abae, Draa iorullensis, and
Arenaría brvoides.
Beaman (1965), Cruz (1969), Rzedowski (1975),
and Almeida et al. (1994) have observed this community in volcanoes along the Transversal Neovolcanic Belt where continuous buming and erazing disturhances take place. This is che reason these
authors considered this grassland to be a seral
communitv (Velázquez' 994). \Coodcutting could
promote this t\-pe oí vegetation.
Less Common Communities
Megarosettes oí Furcraea beding'rausii indicate a
vegetation upe restricted to the rolling , disse ted,
rocky lower slopes oí a few volcanoes in central
Mexico, such as Pelado (3090-3340 m) and Tláloc.
Soils are shallow, gravelly, loam.v clavs (pH 5.36.5). Half-meter - high monocauiescent agavaceous
me,arosettes oí the endemic F:;'aaea be.'ingluusü
characterize this community . The maximum height
ever measured for Furcraea is 53 m. A f oristiallc
rich out relatively open herb :aver is common.
Other characteristic species incude Senecia angulfolius, Stipa tchu, Sympharicarpos mfcrophvllus. Conv=a sciriedeana , Muhlenbergia n:a:rcura, M. quadridentata, Geranium poterrtiliacfo :.m, Gr:aphalivnt
on+yi:vi!u!u. AIchenrilla procunbens , Sibiharpía reyens,
and Festuca an: vtissin!a.
Stipa ici:u meadow is cornmonly known as a
"pradera" oí Potentüla cand ;'eans. It occurs on
poorly drained soils (Cruz 1969 ) cn flats surrounciing volcanic cones at 3000 -3300 m elevation. it is
restricted to the Valley oí Mexico (Rzedows)<Jand
Rzedowsk: 1975; Rzedowski 1981 ). Soils are deep
sandv loaras oí pH 5.G-6.2. Vegetation i s a single
ground laver (0.15 m height ), consisting oí lo,.v
forbs and grasses. Diagnostic and associated species include Stipa iclm. Potentfila ;n:dita; ,, Ast•
alas micrantlrus , Reseda 1uh'ola, 3idenc triylfi:er.'ie,
Hedeonra yipen!¡tut , Con:meiina alpes!n s , Vulpta myures, Akl:emilla procumbens , Gnayrv!i:mt seemannfi,
A. Velázquez, V. Al. Toledo and 1. Luna
and Salria species. This vegetation is significantly
disturbed by hikers and campers.
.An alpine scrub oí Jumpen:s manticnla, codominated by Tortula andico!a, E:3ngiam prctútlorum, and 5enecio n;.ciretfar:us, is restricted to rocks,
wet places aboye timberüne on most high Mexican
volcanoes, such as Po, oca tépetl, and it is also present in Guatemala (islebe and Velázquez 1994).
A narrow ecotonal Cupressus lusitanica forest
used to be widely common behveen fir forest and
cloud forest at about 2600 m eleyation. This transition has largely been deforested and transformed
finto farmland. In the feto remaining patches, Abies
is sometiines co-domLnant in the overstorv. 5enecio
piata,nfoiius, S. cinc arioides, Fudsia ndcrophvia, and
species oí Rubus and Rifes are common Ln an understora shrub layer.
BIOGEOGRAPHIC HYPOTHESES
Mexico's larse biodiversity has been attributed 'o
hvo mala hvpotheses. First, its geographic location
- where t.e Neaaic and the Neotropical zones
overlap - necessar ilv ,laxes temperate and tropical
elements. This is tl e dispersal h}pothesis. Additionaily, a substantial proportion of the total flora
oí ibis region is oí autochthonous origin, fo,nnLng
a heterogeneous mosaic oí species (e.g., Rzedowski
1978). 5econd, its role as a Pleistocene refu,e could
make .a':zeodv-nzrc events oí paramount importance la gocen.rg present vegetation (Toledo
1952 ).
T.ne dispersas hvpothesis imagines that the major mountain ran_es mned as bridges connecting
Mexican and North American .-oras. As a consequence, Holarctic taza reached Mexico across these
:nountzin bridges,.vhich provide a con:inuoaslc
similar climatic condition across latitude (e.g.. Graham 1972; Rzedowski 1975E The arrivzl pernnad oí
most boreal e!ernents is controversial: So:ne authors believe that it -,vas in the Ter;iarv and Early
Quatemary (Graham 1972), whereas Martín and
Harrell (1957), among others, suggest a ¡,lora recent arrival. Tne lose affinity behveen Mexican
and North Amerian temperate taxa has been commented on by severa! biogeographers (e.g., Islebe
and Velázquez 1994). Pczedo•,vski (1993) estimatei
the afíinit<• at 9f at ;`. aeneric 'evel and named
it the "nlega:nexice p :: ie,eograp ic unit."
According to Toledo (1976), hvo aneas of \fevice
functiened as Pleistocene refugia: the Lacondona
and Soconusco regio-s, both oí rvhich still harhor
a larse number of endernic specie s and subsp2c e`
Toledo also hopo;he>ized that additionol reos in
Guatemala and Belize sen-ed as refuges and tr`'t
collectively thev plaved this role several times dar'
. Temperare
ing the Qua
oí glaciers
present dise
vegetation.
There ar
(1952), for ,
between bic
convergent
extend bici
geograpv/-,
rente (1993)
DYNAMIC
Indigenous
tlers, and ci
tures all h;
!andscape.
ulation abo:
oí pre-corta
to rely on
Hemandezgeneralsucc
malnir,g Inc
a, d maintai
Ta: ahumara
1994). There
that suggest
colonial tim
tation couid
stand-replac
(Islebe e: al.
Bv the ti
1500), most
covered by
%Vhen wood
demands (
cvere clear-c
and near lar
sume extent
However, lo
creasing ove
tun•, expiain
forestexcept
Livestock for
tended finto
human pop
needed, and
popular me,
grazing prac
oasis througiledo 1955). A
mote regrow
dental canc
(Velázquez 1',
Most rece
d 1. l;:na temperate Ved
(0:.?, coto rockv,
\texican
pros- 94).
fc-est
etation
in, the Quatemarv. The expansion and contraction
of g)aciers mav additionally have modified the
present dstribution of temrerate humid montane
vegetation.
There are also alternative h•,potheses. Croizat
(1982), for example, finds a ciose correspondence
behceen biologic and geoloo:c histories, suggesting
convergent evolution aad vicariant patterns that
extend back across longer periods. The panbio,eegrapv/vicariance ideas of Espinosa and Llorente (1993) extend back to Laurasian time.
DYNAMICS OF VECETATION
-,b.,t d to
ic location
ica1 zones
..: cpkal
Addia! flora
forming
'.ze ow'skl
-_. e could
_ct imporn (Toledo
.aat th.e m
onnechrng
.s a consecross these
7..ti-:m.:ously
(e.g., Graperiod of
Sume auand Eariv
'aren and
more reMexican
roen cem-
?.,., Islebe
estlmated
named
ot,\fexico
acondona
`arbor
•,:bsoecies.
al arcas in
> and that
times dur-
Lndigenous Indians, contact-period Spanish settiers, and current mixed pepulations of many cultures all base modified t.e temperate Mexican
landscape. There is ve:v little published speculation about reconstruct-.e maps or descriptions
of pre-contact landscapes. Largely we have had
lo rely on experienced botanists Miranda,
Hemandez-X., Rzedowiti, Madrigal) who infer
general successional pathr..avs, and ora t-he ferc rem.aining Lidian groups _^a. _tia manase vegetation
.ai.tain sera] stages mar cultura! reasens (e.g.,
and m
Tarahumaras, Purépet'ras. TzotzLes) (Toledo
1993). There is some evidente from : ellen analvsis
that suggests that there l :as deforestation prior to
colonial times (Metcalfe et al. 1991). The deforestation could perhaps have been caused by large
stand-replacirg tires prornoted by drought periods
(lslebe et al. 1995).
By the time of -he am; al of the Spanish (ca.
L0 ), rnost arcas in central \fexico viere densely
covered by forest in di.`fere.-d successional stages.
when woodcutting took pace to fuif311 European
demands (_ 1700-1500), most temperate forests
were clear-cut on p!ateaus, valleys, around lakes,
znd near larse human se:t!ements. Remaining, to
some extent, vas montane temperate vegetation.
How.+ever. Jogging in montare arcas has been mcreasi.g oven the past 50 vr of the hventieth centurv, explaining the present ratchiness of montane
forest except in the highest, most inaccessible arcas.
Livestock foraging in the nrieteenth centurv extended finto tírese moun'.a..e envi:onr,ents. N'ith
human populatior increase, more meat vas
needed, andburning in t:-.e dn' season became a
popular rnethod to increase forage. This tregrazing practice is still i nlemented on a veariy
bass throughout most of ;Fe temperate rcgion (Toledo 1988).Although the tres are intended to promote regrowth in the understorv vegetation, accidental canopy tires frequently take place
(Velázquez 1992).
Most researchers (Miranda and Hernández-X.
oi
Vexico
585
:963; Madrigal 1967; Rzedowski 1978; Velázquez
and Ceef 1993) agree that fir forest s the mesic
climax tape of Mexican temperate ecosvstems (Fig.
15.S). Ahies co:nm'unities are favored by soils rich
in organic matter, humid terrains, and middle to
high elevations (Madrigal 1967). Clear-cutting for
paper production rransfo-ms :hese forests Lato subalpine bunch rasslar.ds dominated bv Mularrhergia, Calanwgresfis, ard Festuca; selective cutting
trzrsforns them into mixed oak forest w•ith manv
svmpatric Qaercus species. Fire and grazing may
then degrade subaipine bunchgrasslands Lnto a
scrabland of Senecio and Ribes, or roto meadows of
Fofertilia and Stipa rrhere soils are poorly drained.
Scrub and meadow mav regenerate into conifer
forest if there s not stror.g human interferente
(Fig. 15.5). Mixed oak forest can develop finto
mixed alder-oak forest and traen finto either cloud
forest (given sufficient moisture) or hito mixed
pire-aider 'orest (where soils are sandv and
acidic). Mixed pine-alder forest is 'he most w'idely
distributed \Iexican temperate ecosvstem at this
.ir.e. Pire and grazig favor pine species, transfcrmLne tris vegetation tape finto p•ure stands of
pi— forest (Pf s harrargi at Mgh elevations).
Mixed pire-aider forest mav, under very- limited
G: camstznces, develcp back finto fir forest (Hg.
15.5). This happers, for instante, in ver, humid
canvons with a thick litter la%er and an absence of
F:e and erazing. Puse pire forest can also be repiaced by fir forest but only at elevations where fir
species are better adapted tiran unes.
High-elevaion fir and pLne forests, when harvested, revert to alpine bunchgrassland dorninated
by Ca'armgrostis, Trsetum, Agrrstis, and Festuca.
\'exican alpino b•.:nchsrrassland, as well as the
tropical alpine gra stands of páramo and puna, expand where deforestation takes place (Baislev and
L-atevn 1992). Forest regeneration is suppressed =y
E:e- and grazing aovi^es.
Nearnal! temperate vegetation !upes of Mexico
are in some stage of regression or progression. Fire,
srazLng, wind, herbivon-, avalanches, landslides,
volcanism, and human disn:rbances are the causes
o-` tnis seral lancscape. Natural tire and arson may
be the most cornmon disturbznce<_ as evidenced by
t'-. e charcoal that is found in most soils throughout
\`.exco's :nountains. At retum Lntenals of 20 vr,
tire seerns to be a suitahle tool for forest management, but in central Mexico tires recur everv 1-5
vr. Only a few places have remained unbumed >5
vr. The reason for frecuent buming is that the forage becornes less palatable .`or domesticated animas ove, time. A larse amount of oxalates and
siliates, which accumulate in the leaves oí grasses,
may be the cause of low consumption of forage
A. Velázquez, V. Al. Toledo and 1. Luna
586
Vpine
bunchgassland
Cool
bdgh e^eaa ^. o.^s>3:00 n)
Fir forest
Mesic clima
wz.. chesmider:.;n•n_.e.,s
Oow re'va^ov cial:_)
Cloud forest
Figure 7 5 . 8. Sche natic summay of successional relationshios among Mexican temperate vegetaron tvpes. Mesic
climax rypes are s,haded darker than sera! s:ages . Thick arrows represen: natural, progressive succession , v.hereas
hin arrow5 represen: re:rogreirre success,on caused by
human in:e.nerence or by azora1 en, úonmental cond7ons.
(Velázquez 1985). Peasants who set fires, however,
are ignorant oí the fact that many nutrients released by the fire are leached and eroded awav.
Mexican temperate and tropical forests have
been more impacted, fragmented, and depleted
than anv other vegetation tupe (Toledo 19SS; Masera et al. 1992). Recent estimations by Masera et al.
(1992) are that fires (49%), livestock production
(28%), and agricuiture (16%) are the main causes
oí the depletion oí tem orate forests. How+'erer,
these estimates are based on onh• general field obsenatiors and anecd3tal comments from rural
people. Lntensive Jogging activities r+'ere common
Lhroughout the coun-r 30 vr ago. These activities
became regulated by la:v in the 1950s, although ac-
Those few mavs oí current Mexican vegetation
that have been published (e.g., Leopold 1950; Miranda and Hernández-X. 1963; Flores, Jimenéz,
Madrigal, Moncayo, and Takaki 1971; Rzedowski
1978) rapidly became out oí date as extensive human modification oí the landscape continued. Consequentiv, these maps should be considered as depicting potential vegetation ra:.her than actual
vegetation (Velázquez and Cleef 1593). Accordir.g
to Masera, Ordonez, and Dirzo (1992), temperate
forest deforestation (excluding doud forest) has
been estimated at 163,000 ha yr , equivalent to
O.Jl°b oí the total Mexican surface being deforested
every vear. In contrast, reforestation has been attempted en only 13,000 ha, and no: all the attempts
have been successful.
tual imp'.ementation oí :he regulations ,as limi:ed
to central Mexico. ^,e ,+'estem and eastern Sierra:
Madres are stil] beng clear-cut where the original
forests remain. Clcar-a;t;ing in Mexico is net followed bv reforestation; consequently, the neoztiv e
effects oí soil erosion and se¡¡ poductiviry are
astordshing.
Temperate Ve,
In contrast
as practiced f,
favors both re
trees. Minnicf
repeat aerial
have had a s
Aguascaliente
oí Aguascalie.
ests (Quercus :
roxvla, Q. rugí
rus deppeana) t
slopes oí barr
(Fig. 15.9). Ch
pungens, with
opensis, Garrea
abundant on
exploitation fc
using rudimer
tse 1920s dese
Repeat aerial t
1953 reveal th
pulse of wood
oline sawntills
1950 when dic
with the introc
the city oí Ag:
in exploited fe
from pollardir
broad-scale th_
by rapid incre.
establishment
change in the 1
declines in Pin:
attack c ring a
(Siquéir,,s-Def
chaparral expe
fires behyeen
to resprout or
lings from seec
geners in Caii
with open-rang
Recent direc
caused bv anor.
disn:rbance in
derstory in pv
frequent Ere pr.
species of Que'
fires v: ith modo
an ability to r
fines mav have
and encoura2ec
characteristie In.
United States (s
reduce the exte
S!aphylos punge'
aedo and 1. Luna
rcession caused bv
'ro.^.n]e0taf condi-
pical forests have
red, and depleted
Toledo 1988; Masby Masera et al.
estock production
e the main causes
forests. However,
general tie)d obments from rural
ries viere conunon
:o. These activities
i930s, although ac>tions esas lir ited
and eastern Sierra
i,here the original
Mexico is not tolently, the negafive
productivify are
587
Te.rperate Vegeta:ron of Mexico
Ln contrast, less intensive fue!w.wood gatr.ering,
as practiced for local consumption by rural people,
favorsboth re;eneration and de%elopment of adult
trees. \finnich et al. (1994 ) provide evidente from
repeat aerial photographs that land use mav not
have had a severe impact on pine-oak forest in
A uascalientes. The Sierra Fria, located in the State
of Aguascalientes , is dominated by pine-oak forests ( Quercus potesi na, Q. lacta, Q. eduardii, Q. sidermaa. Q- rugosa, Pinus teocore. P. leiopltylla, Junfpcru; de}>peann ) that forro contiguos forests on steep
slopes oí barrancas, and open savannas on mesas
(Fig. 15.9). Chaparral dominated by Arcto;tcphvlos
pun ens, with scattered Arburus glandalosa , .4. ralcpe:ss, Garrua spp. and Conreresta^ )rylos poiifclia, is
abundant on steep slopes . Technologies for forest
exploitatien for rirrtber and charcoal production,
using rudimentary ground kiins , viere limited until
the 1920s due to the inaccessibcity oí the range.
Repeat aerial photographs taken between 1942 and
1993 reveal that the range experienced a distinct
pulse oí woodo.:tt ng with the introduction of gasoline sawrnilis alter 19-0. This iand use ended in
1950 when the urban demand íor ;uelwood ceased
with the irtroduction oí ural gas pipelines into
the city oí Aguasca lientes. Oaks viere still common
in exploited forests because most species resprout
from pollardinz . Since 1942 there has also been
broad-scale thickening of pme-oak forests caused
by rapid inaeases of Jurti?er s dc,,peana and slow
establishment o: Qucrcus spp. There has been little
change im the dstrbution oí pues except for local
declines in Pms:eiephvüa and P. teocote from insect
attack during en El Atto-related drought in 19S4
(Siquéiros- Delgado 1989 ). Ardo;taphylos pr jenn
chaparral experienced little change in spite oí largo
;res betweer, 2920 and 1950. Most species appear
to resprout or to establish numerous postf:re seedlings from seedbanks (A. punge'a), similar lo congeners in California. Stand-tnickening ceinc`ided
with open-range cattle grazing.
Recent direcvona: vegetation changes mav be
caused by anoma )o'as)v infreauent Eire as a natural
dist'srbance ir' the siena . A dense )erhaceous understorv in p--e-oak forests probably supported
frequent fire prior to livestock grating . The cariors
species oí Qurc:is are adapted to sunive ground
tires with moderately thick bark, tal1 canopies, and
en ability to resprout from rootcrowns . Surface
tires may hale selective : v c'Iimtnated yni2ng Fines
and encouraged open o':d-growth forests, as esas
characteristic in cellow pire forests in the western
L'nited States (see Chapter 5). Recurrent tires mav
reduce the extent oí Juniperus deppeana and Arctostaphylos pur.gens because thev are nonsprouters
and do not establish abundant postfire seedlings
from seedbarls. J. dcpra :a mav have survived in
Eire-protected camyers where old-growth stands
no occar.
Urba:-tization v perhaps the most threatening
human aCivity lo temperate forests in central Mexico. Mares oí the maro urban concentrations oí the
co^untrv, includv,g Mexico City, are located in (or
near) temperate vegetation. According lo the National Censas oí Population of 1990, the area covered by temperate vegetation s inhabited by about
19 ,—n people, or one quarter oí the total Mexican
population (Toledo and Rzedowski 1995). Oí these
"•temperate" people, 62% live in cities and 3S°'o in
che co,:ntn-side. It is Chis latter nonurban population oí approimateiv 7.3 million who live most
int mately with temperate vegetation. We estimate
that t`re precortact population within temperate
veeetation „as - in contrast - only about 2 m indigenous people belonSing te 40 different ethnic
groups.
CO.NSERVATION IMPORTANCE
AND PROBLEMS
The tisea ecological regions that constitute the
temperate vegetation area oí Mexico are oí great
portante from a biodiversity point oí view. Despite its reiativ ely small area , t're humid temperate
cioud forest is bioleg caUy very rich. lt harbors a
large number o.` endemic plant species, especially
orchids, ferns, and mosses. Given the small area
and tie lar,e nwn:ber of specíes, it is floristically
the richest zone it \!exico bv unit area (Rzedowski
1993: Stvles 1993). The zone is notable as well for
its lar_e rumbee oí endemic mammals, amphibians, reptiles, and butterfiies (Flores 1993; Flores
and Gerez 1994) lo such an extent that it is one oí
ihe ^ncipal centers oí autochthonous species. Areas abone timberline (>4000 m) are also oí notable
biolc r) and biageog aph cal importance.
O'•erall, the temperate zone covers the greatest
p¿-:t oí the -nountainous arcas oí Mexico. Of special impon tanto s ;.he Transversal Neovolcanic Belt
hecause it harbors one of the highest concentratiors c` specíes dicersity and endemism presentiv
kno-t.-n (Fa 1959). Rzedocski (1993) estímates that
there are 7000 specíes oí flowering plants, oí which
49',J (ca. 75%) are endemic.
About 7.3% of the Mexican territorv is under
sonx po ic} oí protection (Flore; and Gerca 1994).
T.ne criteria for the selection oí protected arcas and
their boundaries hace changed from time lo time.
Most protected arcas (79 out oí 1660) are within
the temperate region and harbor temperate vege-
588
A.
Velazquez,
V, Al. Toledo and 1. Luna Temperare Veger
Figure 15. U Defortional Park 11,900 m'
heede !Dendroctonu
cation tepes (Fio(
naulative area is
al] protected area
surface. Most of th
'egetation are %-e.
that the probabilc
into the future s
trolling to reduce
croachment is lim:
pects nave been ta:permanence and c,
com 1994; Toledo
ÁREAS FOR
FUTURE RESEAR(
Figure 75.9. Pine-oak ioresi in me Sierra Frs. A,aasca- and savannas. 31 Tvpical trr cure ui ti:e ,ore>c., ood!."' `
tientes. (A) General aspect, sho.+irg mosaic oi v: oodlands
;Photographs Couiesy oi Richa:d htinnioh.l
Temperare cegetati
mous impon Lance
They also have ccc
Portante as sources
ceutica's, water, erc
rent knowledge is.
^lest studies ha\ e c:
munities in Central
d 1. Luna
Dresd,voodlar.d
589
,emperare Vegeta don oi A7exico
Fisure 15.70. Deioregytion :n Desierto de ¡os Leones xa:ionai Park 2900 m7 near M exico Ciry, caused bv bark
beet!e rDendroctonus adjuntes!. Air colutants initially
}, eakened :he ,ores:: inrestation by bark beedes then
caused the death or 15%% oí me «ees.
tation tupes (Flores and Gerez 1994), but their cumulative area is modest, accounting for only 4% of
all protected area , or oniv 0.32% of the Mexican
surface. Most of the protected areas witi^ temperate
ye etation are verv small in sine, which implies
that the probability of their cor.tinued existente
roto the future is low. Financial support for patrolling to reduce poaching and other human encreachment is limited. Furtherrnore, no social aspects have been taken finto account to ensure their
permanente and consen'ation (\IcNeely 1989; Alcem 1994; Toledo and Ordoñez 1993).
i-^ormatien about northem and southem communities. In addition te the need for mere descriptive
studies, ;reat effort should Se given to docurnenting ecosvstem processes such as vegetation dynamics and succession. These ecosvstem processes
are the least known aspects of temperate vegetation. The ¿ata are needed to model funare distributions and compositions of these communities.:f
Esancial sapport vvere available, such data could
be obtained re!aüvely quickly. In the absence of
supporz, the most feasible future of tmperate
piant comrnunares is their progressive destruction
(Fig. 15.10).
ÁREAS FOR
FUTURE RESEARCH
Temperate vegetation tepes of Mexico hace enormous importarte as resenvoirs of biodiversitr.
Thev also have economic and hum: n ! calth importance as sources of timber, fuel•.vood, p'r-armaceuticals, water, eroson control, and oxygen. Current know:edge is, hor+ever, far from complete.
Most studies have concentrated on describing communities in Central Mexico, leaving larse gaps in
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