Climate extremes, such as drought, are increasing in frequency and intensity, and the ecological consequences of these extreme events can be substantial and widespread. Yet, little is known about the factors that determine recovery (or resilience) of ecosystem function post-drought. Such knowledge is particularly important because post-drought recovery periods can be protracted depending on drought legacy effects (e.g., loss key plant populations, altered community structure and/or biogeochemical processes). These drought legacies may alter ecosystem function for many years post-drought and may impact future sensitivity (both resistance and resilience) to climate extremes. With forecasts of more frequent drought, there is an imperative to understand whether and how post-drought legacies will affect ecosystem response to future drought events. To address this knowledge gap, we experimentally imposed over an eight year period two extreme growing season droughts, each two years in duration followed by a two-year recovery period, in annually burned tallgrass prairie.
To assess response of recovery of tallgrass prairie plant community composition and ecosystem function to repeated extreme drought events.
Location of Sampling Stations (watershed name, or map with grid locations): HQA.
Frequency of Sampling: Annually (ANPP), twice-annually (plant species composition, plant stem densities), bi-weekly to monthly (soil CO2 flux).
Variable Measured: ANPP, plant species composition, plant stem densities, soil CO2 flux.
Four large rainfall manipulation shelters (each 6 x 26 m in size) were established in 2010. Within each shelter are 10 2 x 2 m plots arrayed in two offset rows of 5 plots each. Each 2 x 2 m plot is divided into four 1 x 1 m subplots. One subplot is designated for plant species composition measurements. The remaining three are designated for soil CO2 and ANPP measurements. Plant community composition is measured in early (late-May or early June) and late growing season (mid to late - Aug) by estimating the aerial cover to nearest 1% (less than 25%), 5% (26-50%) or 10% (less than 50%) in a permanent 1 x 1 m plot. Plant stem densities are measured at the same time as plant species composition early in the growing season. All stems are counted within a permanently marked 20 x 50 cm quadrat located within the 1 x 1 m species composition plot. Stems are separated into the following categories: Andropogon gerardii, Sorghastrum nutans, Solidago canadensis, other grass, other forb, and woody. Productivity is measured by clipping all aboveground biomass within two 20 x 50 cm quadrats. The biomass is separated in the field to the following categories: Andropogon gerardii, Sorghastrum nutans, Solidago canadensis, other grass, other forb, and woody. Soil CO2 collars are installed in two subplots at the beginning of the growing season and measurements are made on a bi-weekly to monthly basis.
Quality Assurance: Entered data is checked twice.