The distribution of vascular plant species and guilds in space and time along a desert gradient

Abstract

Abstract. We studied distribution patterns of vascular plant species and environmental variables for three years along a permanent transect traversing a closed‐drainage watershed in the northern Chihuahuan Desert of south‐central New Mexico, USA. The transect extended for 2.7 km from a basin floor playa (1310 m elevation, fine‐textured soil), across a piedmont slope, and onto the base of a granitic mountain (1410 m elevation, coarse‐textured soil). The gradients in elevation and soils across our transect, along with variable seasonal rainfall, downslope redistribution of water and organic matter, and soil texture‐related variation in infiltration, water holding capacity, and moisture release characteristics, interact to generate a complex spatial and temporal gradient of available soil water and nitrogen. We grouped plant species into guilds according to growth form and photo synthetic pathway type. These guilds are spatially and temporally differentiated along the transect such that particular groups utilize particular seasonal phases or spatial regions of the gradient. We identified six distinct plant communities along the transect. C4 perennial grasses dominated the mesic/high nitrogen portion of the gradient, which occurred at the highest (upper piedmont grassland, dominated by Bouteloua eriopoda) and lowest (playa, dominated by Panicum obtusum) elevations along the transect. C3 shrubs were dominant in the xeric/low nitrogen portion of the gradient located near the middle of the transect (bajada shrubland, dominated by Larrea tridentata). C3 shrubs also dominated a narrow zone of vegetation located adjacent to the playa (playa fringe, dominated by Prosopisglandulosa). C4 perennial grasses, C3 subshrubs, and C3 and C4 perennial forbs and annuals were co‐dominant in the intermediate locations along the gradient, which occurred below (mixed basin slopes) and above (lower piedmont grassland) the bajada shrubland. Life‐form distribution patterns at the small scale of our study reflect some of the patterning that occurs at larger scales in response to climate gradients. The distributions of some species and guilds along the transect are apparently modified by competitive interactions.

Vegetation changes along a precipitation gradient in Central Argentina

“…In accordance with Danin & Orshan (1990) and Cornelius et al (1991), hemicryptophytes are more abundant in the areas with higher precipitation. Chamaephytes show a pattern similar to that of hemicryptophytes, which is in contrast with the life-form spectra observed in other transitional areas between semi-deserts and deserts (Shmida 1985;Shmida & Burgess 1988).…”

Relationships between landforms, geomorphic processes, and plant communities on a watershed in the northern Chihuahuan Desert

“…The plant communities present on the study site were described by Ludwig and Cornelius (1987), Wierenga et al (1987), Cornelius et al (1991). The slopes of Mount Summerford supported a high diversity of vegetation, including species normally found under much wetter climatic conditions, such as Juniperus spp., because of horizontal redistribution of water between microsites on the mountain slope.…”

“…Numbers 1 through 6 designate geomorphic surfaces aged at: (1) Lake Tank -present to 100,000 yr BP; (2) Jornada I -250,000 to 400,000 yr BP; (3) Jornada II -25,000 to 75,000 yr BP; (4) Isaacks' Ranch 8,000 to 15,000 yr BP; (5) Organ I -2,200-7,000 yr BP; (6) Organ II -1,100-2,100 yr BR The longitudinal profile of the surface is drawn to scale, but the width of the block diagram, and the thickness and depths of contact between geomorphic surfaces shown in cross section, have been exaggerated for purposes of illustration. Classification of landforms follows Peterson (1981), geomorphic surfaces were described and dated by Gile and Grossman (1979), vegetation was described by Ludwig and Cornelius (1987) and also in Wierenga et aL (1987), and Cornelius et al (1991).…”

“…Finally, we show how the redistribution of water explains the spatial pattern of plant communities at the Jornada LTER Site. Our work is based on previously published descriptions of the vegetation communities (Ludwig and Cornelius 1987;Cornelius et al 1991), soils (Nash 1985;Wierenga et al 1987), and geomorphic surfaces (Gile and Grossman 1979;Gile et al 1981) at the Jornada LTER Site and the description and classification of basin and range landforms by Peterson (1981).…”

Vegetation and climate characteristics of arid and semi-arid grasslands in North America and their biome transition zone

“…All three sites contain additional grassland and shrubland types that contribute to species richness. Furthermore, differences in landuse (grazing), topography, soils, and animal-generated soil disturbances can have important effects on species richness at each site (Cornelius et al, 1991;Singh et al, 1996;Fields et al, 1999;Ryerson & Parmenter, 2001). Variation in these factors could not be accounted for in our sampling.…”