Performing Department
ESPM
Non Technical Summary
Over the next century, substantial shifts in precipitation regimes are projected for many parts of the world, including the United States. Global circulation models consistently forecast increases in the frequency of extreme events such as severe storms and droughts. The dual effects of altered precipitation and resultant changes in soil nutrient availability may have large consequences for rangeland forage production andcarbon sequestration - critical management priorities in range ecosystems. Range managers cannot control the weather, but they can influence species composition and soil organic matter by managing grazing. In aCalifornia rangeland,we test whether vegetation management that maintains high functional diversitycan optimize ecosystem rainfall use over a range of rainfall scenarios. For instance,diversity may allow different plant groupsto do well given different rainfall years(e.g., forbs better tolerate drought years, highly productive grasses dominate in non-drought years) and this match between rainfall and vegetationshould enhance soil resourcesand forage production. Our overarching goal is to identifymanagment strategies to increase rangeland resilience to climate variability and extremes.
Animal Health Component
0%
Research Effort Categories
Basic
70%
Applied
30%
Developmental
(N/A)
Goals / Objectives
Global circulation models consistently forecast increases in the frequency of extreme events such as severe storms and droughts. As precipitation more frequently departs from the historical range of variability, maintaining stability in forage production to increased climatic variability will be a critical management priority in range agroecosystems. A key mechanism that can lead to stability in forage production is compensatory dynamics, where plant functional groups respond differently to climate fluctuations (e.g., one group tolerates drought, another group is highly productive in non-drought conditions). We hypothesize that trade-off among functional groups should buffer the response of overall forage production to climate variability and better retain soil nutrients in dry-wet up cycles. Our specific objectives are to: 1) quantify relationships among the fate and retention of nitrogen, soil moisture dynamics, and species compensatory dynamics in drought and non-drought conditions; and 2) incorporate these relationships into process-based models of nitrogen retention and forage production in rangelands.
Project Methods
We will use an field experimental approach that manipulates precipitation quantity (drought, non-drought) and variability (drought with wet pluses or uniform rainfall distribution) over time, and the presence of functional groups available to "match" climate variability (grass, forbs, mixed functional diversity). We will use rainout shelters to vary the annual distribution precipitation, standardized water pulses to evaluate soil response to wet-up events, and a combination of species removals and seed additions to manipulate functional group composition. We will measure a full suite of biogeochemical processes affecting C, N, and water dynamics, including leaching, plant uptake, and cycling rates. Based on these measurements, we will use variations on the DAYCENT model to quantify water, C and N states and fluxes at annual, monthly and daily time steps, and the interactive influence of functional group compensation and drought.