Precipitation quantity and timing affect native plant production and growth of a key herbivore, the desert tortoise, in the Mojave Desert

Melia G Nafus,Tracey D Tuberville,Brian D Todd,Kurt A Buhlmann

doi:10.1186/s40665-017-0032-9

Abstract

BackgroundDeserts may be disproportionately vulnerable to changes in precipitation that accompany global climate change due to complex evolutionary relationships of species to historical conditions. Based on current and projected climate scenarios for the southwestern United States, we manipulated rainfall timing and quantity and measured the response by plants and the growth and behavior of the desert tortoise (Gopherus agassizii) to precipitation in the eastern Mojave Desert.ResultsWe found that winter-dominant rain – the current prevailing pattern in the eastern Mojave Desert – and greater total rainfall correlated with greater cover and species richness of plants. Winter-dominant rain also correlated with a higher proportion of native plants flowering relative to invasive plants. Juvenile tortoises grew more rapidly when they were subjected to rainfall treatments that associated with increased plant abundance and species richness, while their behavior appeared more driven by water availability.ConclusionsOur results suggest that precipitation timing may be as important as rainfall quantity when considering total effects of climate change on arid-adapted systems. Further research should explore how the timing of rainfall may interact with aridity or temperature to influence total effects due to climate change on arid communities.

Highlights

Deserts may be disproportionately vulnerable to changes in precipitation that accompany global climate change due to complex evolutionary relationships of species to historical conditions
The enclosures were located at the Ivanpah Desert Tortoise Research Facility (IDTRF), which is a “head-starting” facility in which juvenile tortoises are temporarily reared in captivity
Rainfall and supplemental treatments Mean monthly temperatures during the preceding decade tended to be cooler during winter months than during the study years

Summary

Introduction

Deserts may be disproportionately vulnerable to changes in precipitation that accompany global climate change due to complex evolutionary relationships of species to historical conditions. Based on current and projected climate scenarios for the southwestern United States, we manipulated rainfall timing and quantity and measured the response by plants and the growth and behavior of the desert tortoise (Gopherus agassizii) to precipitation in the eastern Mojave Desert. Water availability can affect many aspects of ecological communities, from primary productivity to activity patterns in wildlife [1, 2]. In arid ecosystems, where water is the primary limiting factor for most species [5], community structure may be susceptible to perturbations in precipitation. Southwestern North America has been identified as a regional climate change hotspot, which is an area that will show some of the greatest response to climate change [10, 11]. Climate projections for the southwest generally predict mean increases in annual temperature and increasing aridity [12, 13].

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