Vegetation of the Santa Catalina Mountains, Arizona. V. Biomass, Production, and Diversity along the Elevation Gradient

Abstract

Measurements were taken in 15 communities along the elevation gradient from fir forest at high elevations, through pine forest, woodlands, and desert grassland, to deserts at low elevations in the Santa Catalina Mountains, Arizona, and in a Cercocarpus shrubland on limestone. Eight small-tree and shrub species of woodlands and deserts were subjected to dimension analysis by the Brookhaven system. Aboveground biomass decreased along the elevation gradient from 36-79 dry kg/m2 in fir and Douglas-fir forest to 0.26-0.43 kg/m 2 in the desert grassland and two desert samples. Net aboveground primary productivity similarly decreased from 1,050-1,150 g/m 2 • yr in mesic high-elevation forests to 92-140 g/m 2 • yr in desert grassland and deserts. Both biomass and production show a two-slope relation to elevation (and, probably, to precipitation), with a steeper decrease from the high-elevation forests to the mid-elevation woodlands, and a less steep decrease from dry woodlands through desert grassland into desert. The two groups of communities at higher vs. lower elevations also show different relations of leaf area index and chlorophyll to elevation and to productivity. The two groups may represent different adaptive patterns: surface-limiting, with low productivity in relation to precipitation but high production efficiency in relation to surface in the more arid lower elevations, vs. surface-abundant, with high productivity relative to precipitation based on high community surface area, but lower production efficiency in relation to this area, in the more humid higher elevations. Vascular plant species diversity shows no simple relation to productivity, but decreases from high-elevation fir forests to the pine forests, increases from these to the open woodlands, and decreases from dry woodlands through the desert grassland and mountain slope desert to the lower bajada (creosotebush) desert.

An examination of the interaction between climate, soil and leaf area index in a Quercus ilex ecosystem

“…Damesin et al [13] significantly related both within-and between-site variabilities in leaf d 13 C with the minimum seasonal leaf predawn potential. This response in d 13 C, and consequently in C i /C a , which tends to optimize the use of water resource can be extended to plant communities growing along a water availability gradient [70] and finally is in agreement with early results of Whittaker and Niering [79].…”

Differential responses of shrubs and herbs present at the Upper Minjiang River basin (Tibetan Plateau) to several soil variables

“…Using different scales, factors-dominating species composition could be different, for the resource variation is scale-dependent (Levins, 1992;Anderson et al, 2004), which may result in different species-environment relationships between stratal layers. Previous work has shown that at large scales, species abundance patterns have been attributed to habitat heterogeneity or environmental gradients, which fail to account for small-scale species interactions and the acquisition of resources (Whittaker and Niering, 1975;Shmida and Wilson, 1985;Currie, 1991), thus the different species-environment interactions between strata would be masked. In addition, the scales that affect species distribution may be not the same between different layers too.…”

The linkages among hillslope-vegetation changes, elevation, and the timing of late-Quaternary fluvial-system aggradation in the Mojave Desert revisited

“…In both Antinao and McDonald (2013a) and this study, the commonness/abundance of Juniperus is used as a proxy for woodland versus desert scrub (i.e., Juniperus rare/absent) vegetation types. Where biomass data are available in the southwestern US, the woodland-to-desert-scrub transition is associated with a step change in biomass (e.g., Whittaker and Niering, 1975). Since woody biomass "reduces runoff and overlandflow erosion by improving water infiltration, reducing impacts by water droplets, intercepting rain and snow, and physically stabilizing soil by their roots and leaf litter" (Kort et al, 1998), a transition from commonness/abundance to rarity/absence of Juniperus is likely to also be associated with a step-change increase in sediment supply to fluvial systems downstream.…”