Richness and Current Status of Gymnosperm Communities in Aguascalientes , Mexico

The gymnosperm diversity of Aguascalientes, Mexico, is presented. Fifteen species from five genera and three families are reported, two of Coniferales (Cupressaceae and Pinaceae) and one of Gnetales (Ephedraceae). Pinus is the most diverse and abundant genus with seven species. The most abundant species is P. teocote, while P. strobiformis is the scarcest. Juniperus is the next most diverse genus, represented by four species, with J. deppeana the most abundant and J. durangensis the scarcest. Cupressus lusitanica, Taxodium mucronatum and Ephedra compacta are each the sole representatives of their genera. Most conifers occupy the mountainous part of the state, forming temperate forest; exceptions are Taxodium, which is located on the margins of permanent streams, and J. coahuilensis, which is found in the low parts of the Aguascalientes Valley over calcareous soils in the northern part of the state. Ephedra is distributed in the northeast part of Aguascalientes in microphyll desert scrub. The current status of the gymnosperm communities in the state of Aguascalientes is discussed.


INTRODUCTION
According to the most recent molecular data, gymnosperms are a natural group that includes four extant main lineages: cycads as the most divergent group, followed by ginkgos and then conifers plus gnetophytes (Bowe et al. 2000;Chaw et al. 2000;Chase and Reveal 2009;Lu et al. 2014).Gymnosperms are distributed worldwide, the majority in temperate regions, although there are several species adapted to dry environments such as Ephedra and Welwitschia, or to tropical environments such as cycads and Gnetum.Even though Mexico is a megadiverse country (CONABIO 1998), gymnosperms make up only about 2% of its flora (Contreras-Medina et al. 2007).However, it has the world's second richest diversity in cycads and is an important center of diversity and endemism worldwide (Farjon and Styles 1997).Several treatments of Mexican gymnosperm diversity have been published (Martínez 1948(Martínez , 1963;;Carvajal and McVaugh 1992;Espinosa-Garduño 2001;García-Arévalo and González-Elizondo 2003;Del Castillo et al. 2004; Gernandt and Pérez de la Rosa 2014).Nevertheless, there are some Mexican states where gymnosperm diversity has been little explored, including Aguascalientes, which presents an interesting gymnosperm species distribution in spite of its arid landscape.
Aguascalientes is one of the smallest states of Mexico, which has enabled considerable progress in the study of its flora, especially as regards gymnosperms and dicots.Of the total flora of Aguascalientes, so far we have studied 142 of the 180 families that have been estimated for an updated floristic checklist of the State of Aguascalientes (Gerardo García-Regalado, Margarita C 2017, The Author(s), CC-BY.This open access article is distributed under a Creative Commons Attribution License, which allows unrestricted use, distribution, and reproduction in any medium, provided that the original author(s) and source are credited.Articles can be downloaded at http://scholarship.claremont.edu/aliso/.
De la Cerda-Lemus, Julio Ramírez-Martínez and María Elena Siqueiros-Delgado, in prep.), including the three gymnosperm families found in Aguascalientes (Cupressaceae, Ephedraceae and Pinaceae).Given the topography and climatic characteristics of Aguascalientes, gymnosperm diversity is moderate.However, in the mountainous area we can find conifer forests (Cupressus lusitanica, Juniperus spp.and Pinus spp.), scarce gallery forests (Taxodium mucronatum) along dry stream beds elsewhere in Aguascalientes, or as elements of xerophytic shrub (Ephedra compacta) in a small region in the northeast (Fig. 1-5).The highest percentage of gymnosperm species in Aguascalientes is located in the west of the state in a massif that has a north to south orientation and links a series of low hills and plateau systems, collectively called "Sierra Fría" in the north and "Sierra del Laurel" in the south (Fig. 6).Pine forests are common in the highlands, juniper forests in the plains, and cypress forests in the valleys, usually associated with oaks.Pure forests of pine, juniper or cypress are extremely scarce in Aguascalientes, covering an area of only 0.71% of the total area of natural vegetation (Siqueiros et al. 2016).However, the temperate region covered by mixed forest (oak-pine-juniper or oak-cypress), manzanita scrub [Arctostaphylos pungens Kunth] and temperate grasslands constitutes 30.48% of the natural Aguascalientes vegetation (Siqueiros et al. 2016).Ephedra compacta, on the other hand, occupies a smaller area in the northeastern part of Aguascalientes dominated by microphyll desert scrub, which is an extension of the Chihuahuan desert.
In recent years, significant progress has been made in the study of the Aguascalientes flora, and the study of the gymnosperm flora is now complete.Noteworthy among the publications on gymnosperm biodiversity in the state are Martínez (1948), Rzedowski andMcVaugh (1966), Sánchez-Durón et al. (1967), Bolio et al. (1970), Pérez de la Rosa (1985), García et al. (1999) and Siqueiros (1999).The most comprehensive works are those of Siqueiros (1999) and García et al. (1999) who reported 10 species of gymnosperms from Aguascalientes.This paper aims to present the complete and updated floristic list of gymnosperm species distributed in Aguascalientes and to provide some information about the current situation of their communities.(INEGI 1981).It is bordered by Zacatecas to the north, east and west, and by Jalisco to the south, and includes eleven municipalities (Aguascalientes, Asientos, Calvillo, Cosío, El Llano, Jesús María, Pabellón de Arteaga, Rincón de Romos, San Francisco de los Romo, San José de Gracia and Tepezalá; Fig. 6).Most of the state is occupied by a central plateau which corresponds to the physiographic region named "Mesa del Centro."It has a north to south orientation, extending eastward with a few isolated ranges, such as the "Sierra de Los Gallos," "Sierra de Tepezalá" and "Sierra de la Comanja" (Rodríguez-Ávalos 2014).This region is covered mainly by xerophytic scrub with Acacia schaffneri (S.Watson) F.J. Herm., A. farnesiana (L.) Willd., Prosopis laevigata (Humb.& Bonpl.)M.C.Johnst., or Mimosa monancistra Benth.Microphyll scrub is found in the eastern region, adjacent to Zacatecas, as a southern extension of the Chihuahuan Desert (Granados-Sánchez et al. 2011), with species such as Ephedra compacta, Calliandra eriophylla Benth., Condalia warnockii M.C.Johnst., Mortonia palmeri Hemsl., and a very restricted population of Larrea tridentata (DC.)Coville, among others.This zone occupies only 10.7% of the total xeric scrub of the state, and it is located in the municipalities of Asientos and Tepezalá.The mountainous region of Aguascalientes is located in the northwest in the foothills of the Sierra Madre Occidental.It exhibits a north-south orientation and mainly holds oak and conifer forests with elevations exceeding 3000 m.It encompasses the municipalities of San José de Gracia, Calvillo, Jesús María, Rincón de Romos and Pabellón de Arteaga and consists of several mountain ranges and plateau systems, separated by deep ravines and small intermountain valleys.Although they are collectively called "Sierra Fría", actually the Sierra Fría is the northernmost mountain range, which continues northward into Zacatecas.The Sierra de San Blas de Pabellón, Sierra de Palomas, Sierra de Guajolotes, Sierra del Pinal and, to the southeast, Sierra del Laurel are the more prominent ridges in Aguascalientes.
According to the classification system of Köppen, modified by García de Miranda (1973), the climates of Aguascalientes correspond to the semi-arid BS and the temperate C(w) climate groups, accounting for approximately 86% and 14% of the state, respectively (Table 2).Each group is further subdivided according to rainfall amount and season, temperature regime, and elevation, etc. (Table 2).Temperate climates occur in the mountainous areas of the Sierra Fría and Sierra del Laurel.The highest average annual rainfall (600-800 mm) occurs in the highest elevations (>2500 m) of the Sierra Fría and Sierra del Laurel where annual temperatures average 12-18 • C. Summer rainfall defines the two temperate climate subtypes C(w 0 ) and C(w 1 ) and predominates in the semi-arid subtypes (BS 1 kw(w) and BS 1 hw(w)), but some winter rainfall occurs in the most widespread subtype, BS 1 kw, in the semi-arid climate category that affects 63.8% of the state (Table 2).The warmest temperatures occur in semi-arid subtype BS 1 hw(w) where annual values average 18-21 • C.
Floristically, the state of Aguascalientes belongs to two regions: the Mexican Xerophytic and, to a lesser extent, the Mountain Mesoamerican (Rzedowski 1978).The major types of vegetation found in Aguascalientes are: (1) temperate vegetation, located in the mountain ranges, in the municipalities of San José de Gracia and Calvillo, with temperate forests (Quercus, Pinus, Juniperus and Cupressus forests with their respective mixtures), manzanita scrub and temperate grasslands; (2) tropical vegetation distributed in the southwest in the municipalities of Calvillo and Jesús María, with subtropical scrub and tropical deciduous forest as the main communities; (3) xerophytic vegetation localized in the north-central part of the state, including an extensive crassicaul thorn scrub and xeric grassland, in the municipalities of Aguascalientes, Cosío, El Llano and Jesús María, and microphyll scrub in Asientos and Tepezalá; and (4) small patches of riparian vegetation along natural and artificial bodies of water distributed state-wide (CONABIO-IMAE-UAA 2008).

Field Work and Data Analysis
Field work was conducted weekly throughout the state over four years, resulting in a total of 320 records of gymnosperms across their distribution range.Gymnosperm collections from Aguascalientes were reviewed in the MEXU and HUAA herbaria.The specimens were processed according to Lot and Chiang (1986) and identification of the material was carried out with specialized bibliography (Martínez 1948(Martínez , 1963;;Rzedowski andMcVaugh 1966, 1972;Zanoni and Adams 1979;McVaugh 1992;Stevenson 1993;Thieret 1993;Zamudio and Carranza 1994;Villanueva-Almanza and Fonseca 2011;and Adams 2014).Nomenclature of gymnosperm species follows Gernandt and Pérez de la Rosa (2014), except for Cupressus lusitanica, which in their paper is accepted as Callitropsis lusitanica (Mill.)D.P. Little (Little 2006).The NOM-059 and the IUCN Red List were reviewed to find any threatened gymnosperm species in Aguascalientes.Vegetation types were assigned according to Siqueiros et al. (2016).Oak-pine and pine-oak forests differ in the relative dominance of pine and oak.

RESULTS
Fifteen species of gymnosperm belonging to five genera and three families were recorded for Aguascalientes.The most abundant and diverse genus is Pinus with eight species, followed by Juniperus with four, and Cupressus, Taxodium and Ephedra with only one species each (Table 1).Among the pines, P. teocote and P. leiophylla are the most abundant species, while P. strobiformis is the scarcest.The most abundant Juniperus species is J. deppeana, while J. coahuilensis is the least frequent and only some old trees survive.Three of the fifteen species (Cupressus lusitanica, Pinus strobiformis and P. durangensis [as P. martinezii]) are in the NOM-059 in the Pr category (subject to special protection) and in the IUCN Red List of Threatened Species (2015) in the LC (least concern) category.Twelve species (all Pinus species plus Cupressus lusitanica) are distributed in the mountainous region in the municipalities of Calvillo, Jesús María and San José de Gracia; Taxodium mucronatum occurs in the municipalities of Aguascalientes and Jesús María, and Ephedra in Asientos and Tepezalá (Table 1).

Cypress Communities (Cupressus lusitanica)
Cupressus lusitanica, commonly called Mexican cypress, is distributed from Mexico southward throughout Central America to Bolivia.The origin of this species is controversial.According to Eckenwalder (2009) Mexican populations were introduced from Portugal.However, Martínez (1963) and Farjon (1993) stress its American origin, a fact that was overlooked after its early introduction to Portugal in 1645.In Aguascalientes, the earliest mention is by González (1881), who noted the presence of cypress and ahuehuetes (Taxodium mucronatum) in the State.The cypress forests in Aguascalientes comprise deteriorated communities, usually of primary origin, established in the bottom of sheltered wet canyons with accumulation of alluvium and sedimentary rocks, at elevations of 2200-2500 m.The cypresses usually run along ravines, associated with other species with high moisture requirements such as Arbutus spp. or Garrya spp.However, on the slopes of the canyons we can often find other types of plant associations, depending on steepness and exposure, such as oak or pine forests, or other riparian elements such as Populus tremuloides Michx.or Arbutus tessellata P.D. Sørensen.These forests are located in the municipalities of Calvillo, Jesús María and San José de Gracia and are characterized by the dominance of white cedar or cypress that can grow to 30 m high.Although scarce, difficult access to most of the cypress forests has led to their preservation.Some localities where preserved cypress forests can be found are: Barranca los Planes (Sierra de Guajolotes, San José de Gracia), Barranca Pilares Richness and Current Status Juniper Communities (Juniperus spp.) Four species of juniper are located in Aguascalientes: Juniperus coahuilensis, J. deppeana, J. durangensis, and J. martinezii.The juniper forests cover an area of 12.67 km 2 .LeSueur (1945), Gentry (1957) and Rzedowski (1978), among others, have proposed a secondary origin of juniper forests.In Aguascalientes, the juniper forests are communities of rapid recovery, and it is common to find a great number of juvenile trees in openly grazed areas as secondary vegetation on land cleared for livestock that was previously occupied by pine-oak forests at elevations of 2300-2700 m.Usually, these forests are open, Juniperus coahuilensis is native to the semi-arid southern plains bordering the Chihuahuan Desert to the east and west, extending from Chihuahua to Aguascalientes and Guanajuato.It occupies hills and piedmont slopes formed by outcrops of limestone and paleo-lake sediments that compose the Green River-San Pedro River basin.Currently this species is rare in the state, occurring as two disjoint populations in the north and south of Aguascalientes.However, it likely was part of an old corridor of calcicolous scrub with a continuous distribution from southern Zacatecas to Los Altos de Jalisco via the rolling hills crossing the Valley of Aguascalientes.It can be found between elevations of 2100 and 2400 m in climates ranging from temperate semi-dry to temperate sub-humid, associated with oak forests and natural grasslands.In lowlands it forms low and open scrub, but in the valleys and slopes it can rise to communities up to 8 m high and with a closed canopy.The best-preserved J. coahuilensis community is located in the valleys and piedmont of the Chiquihuitillo hill, north of Rincón de Romos, in the direction of Zacatecas City, where this plant community continues.Another population occurs at the southern end of the state near Tanque de los Jiménez.However, the original population was removed for posts, firewood and wood for making various utensils and regional crafts, so only a few junipers remain as a mature community.
Juniperus deppeana is widespread from the southwestern US as far as Puebla, Mexico, and in Aguascalientes it is the most abundant gymnosperm species, occurring in deep alluvial soils in San José de Gracia municipality (Díaz et al. 2012).It can be the dominant element of the forest and forms one of the most attractive forest communities for recreation, given the relatively flat land that it occupies, its easy access, and its scenic beauty.
This species can form pure forest or be associated with pine or oak forests, at elevations of 2400-2550 m (Siqueiros 1999).
Juniperus durangensis is distributed throughout north-central Mexico (Aguascalientes, Chihuahua, Durango, Jalisco, Sonora, Zacatecas), growing in oak, pine or mixed forests.Although apparently rare throughout its range and previously considered vulnerable (Farjon 2005), its status in the IUCN is LC (least concern [IUCN 2015]).In Aguascalientes it is also rare, located in the municipalities of Calvillo and San José de Gracia, as elements of oak and pine forest or scrubland, at elevations of 2340-2850 m, mainly on humid slopes or near streams.It is never the dominant element.
Juniperus martinezii is restricted to small, local populations in rocky areas (Adams et al. 1990).It grows in pine-oak forest and woodland and in oak woodland, often on calcareous soils, at elevations of 1950-2500 m.In Aguascalientes it is distributed in the municipalities of Calvillo, Jesús María, and San José de Gracia, in plateaus and slopes of shallow canyons of the Sierra Fría and Sierra del Laurel.It is never found as the dominant element.Given its restricted distribution range, this species fulfills the criteria for listing as Vulnerable.

Ahuehuete Communities (Taxodium mucronatum)
The "ahuehuetes" in Aguascalientes are located on the banks of ancient streams like rivers or springs.They form gallery forests in the municipalities of Aguascalientes, Calvillo and Jesús María.Formerly, streams and rivers in the state usually had gallery forests dominated by Taxodium mucronatum (González 1881), often accompanied by Populus fremontii S. Watson, Salix bonplandiana Kunth, S. humboldtiana Willd.and Fraxinus uhdei (Wenz.)Lingelsh.Today, it is rare to find preserved ahuehuete forests, which mostly have been cut, resulting in secondary forests of Salix spp. or Schinus molle L. Sometimes, they have been completely eradicated along dry riverbeds of urban areas, leaving only shrubs like Baccharis heterophylla Kunth, B. salicifolia (Ruiz & Pav.) Pers.or Salix taxifolia Kunth.However, we can still find a few places where the ahuehuete forest is preserved, with old and large trees such as the Sabinal in the city of Aguascalientes.In these conserved sites it is common for old trees to form a dense canopy over the surface of the water, with trees up to 25 m high.

Pine Communities (Pinus spp.)
Eight species of pines have been recorded for Aguascalientes: Pinus cembroides, P. chihuahuana, P. devoniana, P. durangensis, P. leiophylla, P. lumholtzii, P. strobiformis and P. teocote (Siqueiros 1999).Pinus strobiformis was discovered as late as 2014 by the Consejo Nacional Forestal (CONAFOR) in a very inaccessible location in Monte Grande de Sierra Fría, Aguascalientes being the most southern distribution of the species.Out of the eight Pinus species, four are scarce with very small populations (Pinus cembroides, P. devoniana, P. durangensis and P. strobiformis).In Aguascalientes, pines are usually associated with oaks or junipers.Pure communities are extremely scarce, covering only about 27 km 2 (0.5% of the total vegetation cover of the state).Of those, a little over 62% are conserved forests, while the rest represent secondary forests.The limited area of pure pine stands has long been located on private land.Thanks to this, some of these forests have remained as primary communities with different degrees of disturbance.
Logging, fires, severe droughts and pests through the years have gradually decimated populations of pine, eradicating them from many sites and preventing estimates of their possible original range.The intense exploitation of forest products occurred during three decades (1920s to 1950s) of logging, and charcoal production caused a negative impact on the density of pine and oak forests.However, information about historical use of these forests is limited.On the other hand, forest fires also contributed to the reduction of temperate forests in Aguascalientes.A severe fire in 1993 that devastated Monte Grande de Sierra Fría was recorded as having consumed an area of 6000 ha.There are records of at least nine fires per year over the past 14 years (Asociación Sierra Fría 2005).Comparing aerial photos from 1970 to 1993, Minnich et al. (1994) discovered high mortality of P. leiophylla due to the 1984 drought, weakening the forest and making it prone to pests such as Dendroctonus mexicanus Hopkins.Pests have been another decisive factor in the pine populations' decline in the state.Several infestations were detected over the past 30 years.During 2001, about 10,000 pines were destroyed by Dendroctonus mexicanus in the Sierra Fría (Sánchez-Martínez 2004).According to Chapa-Bezanilla et al. (2008), pine forest in Aguascalientes increased significantly in surface area from 1956 to date, indicating that there was recruitment of new individuals, and showing a moderate recovery despite the pressures of natural (infestations of bark beetles) or anthropogenic origin (logging or "sanitation").Most pine populations have been preserved on the southern flank of the region known as Monte Grande at the top of the Sierra Fría, as well as in some canyons that descend toward the southeast.Currently, there are scattered pine forests growing in the western escarpment of the Sierra Fría, in the eastern highlands near the town of La Congoja and in the high plateaus in the southern part of the mountains.Pine forests in the state establish at elevations ranging from 1790 to 2800 m, depending on the species.
Pinus cembroides in Aguascalientes forms scarce populations in the San José de Gracia municipality.It is believed that populations originally occupied the middle and lower slopes at the foot of the mountains and temperate grasslands between 2350 and 2400 m, usually in thin and poor mountain soils on steep slopes (lithosols).Today, unfortunately, only few populations survive, usually associated with oaks, rarely as pure stands (Rodríguez-Ávalos 2014).Only two populations have been recorded in Aguascalientes, one in Mesa de Hierba Anis and one in the Sierra de Guajolotes, the latter with non-viable seeds.
Pinus chihuahuana populations are rare in Aguascalientes.Commonly they occur as scattered individuals, often associated with Pinus leiophylla, P. teocote or Quercus spp., in mixed forests and woodlands.They thrive on flat terrain, gentle slopes, or in the bottom of canyons in deep and loamy soils (Vertisols) between 2250 and 2700 m in San José de Gracia and Jesús María municipalities.
Pinus devoniana is distributed from central Mexico to Guatemala.Aguascalientes and Zacatecas represent its most northern distribution in the Sierra Madre Occidental.This species was reported before as P. michoacana Martínez var.cornuta Martínez (Siqueiros 1999).In the state, P. devoniana is represented by only a few isolated individuals mixed with other pine species and oaks, usually on humid slopes, in the municipality of San José de Gracia from 2450 to 2650 m.It is a very scarce species.
Pinus durangensis is also very scarce in the state.It is distributed in the municipalities of Calvillo, Jesús María and San José de Gracia, forming populations of few trees in oak-pine forests, usually on high peaks, wet slopes or in the beds of ravines between 2450 and 2800 m.The species is included in the NOM-059 list as subject to special protection under its synonym Pinus martinezii E. Larsen (Gernandt and Pérez de la Rosa 2014).It is difficult to establish whether their populations were more extensive in the past and whether their decline was caused by natural or anthropogenic factors.
Pinus leiophylla is one of the most common species in the Aguascalientes pine forests; it can form pure patches, but it is usually associated with P. teocote, oaks and other forest elements such as Prunus serotina Ehrh.or Arbutus spp.Pinus leiophylla is located along streams and on wet slopes with northern exposure in the Sierra Fría, forming relatively pure stands in some localities such as "El Guaro", the Sierra de San Blas de Pabellón (Sánchez-Martínez 2004), or some areas of the Sierra del Pinal.Also, it can grow in high plateaus such as Mesa el Águila or Mesa el Aserradero (Minnich et al. 1994) between 2200 and 2700 m.
Pinus lumholtzii is called "sad pine" for its pendulous foliage.It rarely forms pure stands and usually occurs in very small populations in association with Quercus jonesii Trel.and sometimes P. durangensis.It inhabits low hills with poor soil, low plateaus or gentle slopes on land composed of outcrops of acid tuff between 2300 and 2800 m in San José de Gracia and Calvillo.
Pinus teocote is the most common species distributed in Aguascalientes, usually on very gentle or relatively flat topography such as in drier plateaus and middle slopes.It forms mixed forest, associated either with other species of pine or oaks, or forms pure patches (Siqueiros 1999), mainly in the municipalities of Jesús María and San José de Gracia at 1640 to 2830 m.The wood of this pine is strong and of good quality, contributing to its extensive use for construction and as fuel.
Pinus strobiformis is the scarcest species in the Aguascalientes temperate forests.This record constitutes the southernmost stand of its distribution.Only one population is known in Monte Grande de Sierra Fría.It is located on slopes with outcrops of acidic tuff on the highest peaks of the Sierra Fría on the border to Zacatecas at 2799 m in the municipality of San José de Gracia.Trees are scattered in the forest, mixed with P. teocote, P. lumholtzii, Quercus jonesii, Q. sideroxyla Bonpl., Juniperus deppeana and Arctostaphylos pungens.

Ephedra Communities
In Aguascalientes there is only one species of Ephedra, E. compacta, commonly associated with other shrubs of microphyll scrub such as Calliandra eriophylla, Jatropha dioica Sessé, Condalia warnockii, or Purshia plicata (D.Don) Henrickson, among others.It is occasionally associated with desert grasslands composed of Aristida purpurea Nutt., also common in this area of Aguascalientes.It is located on calcareous slopes, hills and piedmont to the south of the Sierra de Tepezalá and Asientos.The Ephedra community has been recorded only for Tepezalá and Asientos, two municipalities in the northeast of Aguascalientes, and possibly represents a continuation of the microphyll scrub of the Chihuahuan desert.It occupies approximately 71.7 km 2 , which represents 10.7% of the xerophyllous scrub of the State.The microphyll desert scrubland occurs on gentle limestone hills extending from the Sierra de Tepezalá to the south, until it reaches the edge of the Chicalote river basin.It establishes preferentially on outcrops of Cretaceous marine sedimentary rocks and their alluvial debris on shallow and poor soils with a high content of calcium carbonates.The current situation of the microphyll desert scrubland is worrying.It has been heavily damaged by anthropogenic activities ranging from underground and strip mining to overgrazing by horses, cattle, and goats.As a consequence, it is estimated that 80% of these communities are in a secondary condition.At present, mining activities in this region are threatening the existence of this unique plant community in Aguascalientes.It is essential to set aside areas of exclusion or reserves for implementation of long-term conservation plans.

DISCUSSION AND CONCLUSION
We recorded 15 gymnosperm species from Aguascalientes.Given that Gernandt and Pérez de la Rosa (2014) have been working on Mexican conifers for a long time, we follow their treatment rather than those of Eckenwalder (2009) or Farjon and Styles (1997).For instance, we use Juniperus martinezii instead of J. flaccida Schltdl.var.martinezii (Pérez de la Rosa) Silba and Pinus chihuahuana instead of P. leiophylla var.chihuahuana (Engelm.)Shaw.We tried to explore even the most hidden and inaccessible sites; however, there is always the possibility of finding something new.According to Villaseñor (2016), there are 23 gymnosperm species in Aguascalientes.However, during 30 years of botanical exploration we found only the 15 species documented here.Villaseñor mentioned, for instance, Abies religiosa (Kunth) Schltdl.& Cham., Pinus hartwegii Lindl., P. oocarpa Schiede ex Schltdl., or Podocarpus matudae Lundell, among others.However, requirements of these species are far from the climatic or topographic characteristics of the State.Besides, he does not mention any precise locality or bibliographic source for these species records.
Although Aguascalientes is one of the smallest Mexican states, its richness in conifers is good.This may be partly a function of a high species-to-area ratio due to thorough field work combined with the small size of the state.For instance, Aguascalientes possesses 14 conifer species in 5618 km 2 (2.492 × 10 −3 species/km 2 ), compared with larger states such as Jalisco with 36 species (Rodríguez-Contreras 2010) in 78,588 km 2 (4.6 × 10 −5 species/km 2 ) or Oaxaca with 24 species (Del Castillo et al. 2004) in 93,757 km 2 (2.6 × 10 −5 species/km 2 ).
The most abundant conifer species in the Aguascalientes forests are Juniperus deppeana, Pinus teocote and P. leiophylla, followed by P. lumholtzii, P. durangensis and P. cembroides.The remaining species are very scarce, with scattered individuals among other forest elements or along ancient water courses.The scarcest species are Pinus strobiformis and Juniperus coahuilensis, the juniper represented only by one or two individuals.Most of the decline in the pine populations is probably due to intense logging in past times and prolonged severe droughts and pests.On the other hand, the beauty of the area and the need to provide the human population with nearby recreational areas make it necessary to facilitate access to the mountains.The creation of new human settlements or the growth of existing rural areas, commercial and agricultural use of land and overgrazing are factors of a social type that have favored the depletion of the forest area as a whole.Regarding Ephedra compacta, despite the fact that its populations are in good shape so far, its natural habitat is threatened by mining activities that are growing in this part of the state.
Finally, in order to maintain our natural plant communities in good condition, it is imperative to establish programs to conserve a healthy and stable natural heritage that our children will inherit.

Table 1 .
Gymnosperm species recorded in the municipalities and plant communities of Aguascalientes, Mexico.The situation of the cypress forest can be considered in decline due to logging for local use and degradation of habitat.It covers an area of 1.49 km 2 , representing only 0.16% of the total area of the Aguascalientes temperate forest, although previously this forest likely was more widely distributed.Given that cypress forest is confined to the fringes of permanent streams with a constant supply of water, its recovery is extremely improbable because of the replacement of these permanent streams by seasonally wet streams that receive water only during the rainy season.The cur-rent distribution of cypress forest is patchy, each patch covering a relatively small area, and most are at the primary successional stage, albeit with different degrees of disturbance.This species is mentioned in the NOM-059 (SEMARNAT 2010) list in the category Pr (special protection).
(Sierra de San Blas de Pabellón, Calvillo), Barranca las Palomas (Jesús María), Barranca Adjuntas (Monte Grande de Sierra Fría, San José de Gracia), Barranca Cedros (Sierra de Guajolotes) and Ojo de Agua del Arriero (Boca Oscura stream, Sierra del Laurel).The community of Barranca los Planes is the largest, relatively well preserved and diverse, with abundant juveniles and evidence of recruitment.In contrast, the population of Barranca Ojo de Agua del Arriero is the smallest and the most affected by human activity(Siqueiros 1999; Rodriguez-Ávalos 2014).

Table 2 .
García et al. 1973)uascalientes(INEGI 2008)classified according to the Köppen system (modified byGarcía et al. 1973).stratification, and a dense herbaceous stratum.They are established on flat to slightly undulating land such as plateaus or beds of canyons in the mountainous part of the state, in alluvial soils derived from igneous rocks or tuff with deep soils of moderate drainage.Although these forests are of secondary origin and are considered to represent successional bance is the clearing of land for farming, which-if neglectedcauses problems of erosion and weed invasion.There are no reliable records of the exploitation of juniper forests in the area; however, they may have been cleared to allow agricultural activities.