Influence of Precipitation on Perennial Grass Production in the Semidesert Southwest

Abstract

Perennial grass production in the semidesert grass-shrub type (with and without a velvet mesquite (Prosopis juliflora var. velutina [Woot.] Sarg.) overstory) was dependent primarily on current summer rainfall and previous summer rainfall. The influence of previous summer rainfall was an interaction effect-not a direct effect. The best overall relationship involved current August rainfall, previous June through September rainfall, and the interaction product of these two. However, in interaction product alone yielded estimates essentially as good as the multiple regression, and explained 64%-91% of the year-to-year variability in grass production. Winter precipitation had no consistent effect on perennial grass production the following summer. The depressing effect of mesquite on perennial grass production was most noticeable at low rainfall levels, and became minor at high rainfall levels.

PAR extinction in shortgrass ecosystems: effects of clumping, sky conditions and soil albedo

“…This bimodal rainfall pattern promotes two growing periods, a minor one in late winter and early spring if temperatures are favorable, and the major one making up about 90% of the annual aboveground biomass production, during the summer monsoon season (Cable, 1975).…”

Exploiting Differential Vegetation Phenology for Satellite-Based Mapping of Semiarid Grass Vegetation in the Southwestern United States and Northern Mexico

“…For an individual vegetation type, this response has multiple expressions, including unique physiognomy, physiology and phenology [76,77] and variation in spatial distribution and surface cover. The phenology exhibited by the perennial C 4 grasses closely follows the seasonal precipitation pattern dictated by the North American Monsoon [60,62,68,72,73,78].…”

“…The perennial C 4 grasses, which are the dominant grass type in our study area, exhibit a phenological pattern that is tightly coupled with the region's characteristic but highly variable seasonal cycle of temperature (winter minimum, summer maximum) and precipitation (winter and summer, with drought in spring and autumn) [62,66]. Their principal, active growth period occurs during the summer and early autumn when warm temperatures suitable for C 4 photosynthesis coincide with the arrival of precipitation from the North American Monsoon, and is typically followed by a period of senescence and dormancy in winter and spring [62].…”

“…The surface cover and productivity of the perennial grass component of the arid and semiarid Southwest landscapes can vary widely across the region and over time, reflecting the interacting influences of climatic and edaphic conditions (expressed primarily as water limitations on growth), inter-species competition for resources, disturbance (e.g., wildfire and pests), herbivory, and land use associated with human activities, particularly (but not exclusively) grazing [14,[58][59][60][61][62]. Under these particular, highly variable growth conditions, grasses (as well as other plant types) exhibit unique adaptive strategies that provide distinct competitive advantages, which are integral to their occurrence and sustained existence in the Southwest.…”

“…Their principal, active growth period occurs during the summer and early autumn when warm temperatures suitable for C 4 photosynthesis coincide with the arrival of precipitation from the North American Monsoon, and is typically followed by a period of senescence and dormancy in winter and spring [62]. This pattern contrasts starkly with the phenology of the other major vegetation types, primarily shrubs, trees and succulents, that coexist with perennial grasses in Southwest landscapes and remain green during a longer period (mesquite and riparian trees) or throughout the year (most shrubs and succulents) [67][68][69].…”