Public Abstract

DE-SC0019037: Using root and soil traits to forecast woody encroachment dynamics in mesic grassland

Award Status: Inactive

Institution: Kansas State University, Manhattan, KS
UEI: CFMMM5JM7HJ9
DUNS: 929773554

Most Recent Award Date: 08/04/2022
Number of Support Periods: 3
PM: Stover, Daniel

Current Budget Period: 09/01/2020 - 08/31/2023
Current Project Period: 09/01/2018 - 08/31/2023
PI: Nippert, Jesse

Supplement Budget Period: N/A

Public Abstract

Grasslands are a widespread and globally important biome providing key ecosystem services including carbon (C) storage and regulation of the water cycle. Grasslands face multiple threats, including changes in drought intensity and woody encroachment - a process that results in increased woody plant abundance corresponding with decreased herbaceous plant abundance. The combination of reduced soil moisture and shifts in plant dominance from herbaceous to woody are likely to alter C pools in the soil profile. We currently do not have the capacity to predict either the magnitude or rates of change in these C pools. In order to predict changes in grassland vegetation structure and the associated impacts on C cycling, we require a better understanding of the distribution of soil C pools at multiple soil depths, and the responses of these pools to changes in precipitation. The Land Surface Model (LSM) component of Earth System Models has the ability to capture these dynamic changes in ecosystem function, but currently lacks the data to accurately parameterize these processes at multiple depths within the soil profile. To support and perform this parameterization, we will undertake a detailed investigation of root and soil traits at varying soil depths, to capture the belowground impacts of changing dominant plant growth forms (grasses to shrubs) and the impacts of frequent drought. We have developed a set of objectives that combine observational, experimental and modeling approaches to improve our ability to predict ecosystem consequences of shrub encroachment and drought in the US Great Plains region. These objectives are: (1) Quantify differences in aboveground (stem and leaf biomass) and belowground C pools (root C, microbial C, bulk soil C) using detailed excavations of entire mixed shrub-grass assemblages. We will also subsample portions of the rhizosphere for detailed root physiological and microbial activity measurements, to provide information on rates of change in soil C pools; (2) Using rainout shelters built over mature shrub-grass communities, we will experimentally reduce the amount of precipitation. Comparing responses between shrubs and grasses, we will measure differences in source-water use, above and belowground productivity, canopy water stress, soil C pools and microbial C-cycling activity, and changes in plant cover and community dynamics; (3) Using a global demographic LSM (CLM FATES), we will forecast the impacts of available water on shrub-grass cover in the central Great Plains region, and the resulting effects of these dynamics on ecosystem services (aboveground production, above- and belowground C budgets). Results from this project will define the depth-resolved feedbacks of drought and dominant vegetation on belowground root architecture, soil microbial C cycling, and ecosystem C balance. The observation-experiment-modeling framework used here will improve our understanding of interactions and feedbacks between aboveground and belowground processes, by specifically measuring plant-soil-microbial traits at various depths in the soil profile. The details of these coupled interactions (plant-soil-microbial) will improve the representation of subsurface processes in LSMs and will improve forecasts of dynamic changes in ecosystem structure in grassland ecosystems.

Grasslands are a widespread and globally important biome providing key ecosystem services including carbon (C) storage and regulation of the water cycle. Grasslands face multiple threats, including changes in drought intensity and woody encroachment - a process that results in increased woody plant abundance corresponding with decreased herbaceous plant abundance. The combination of reduced soil moisture and shifts in plant dominance from herbaceous to woody are likely to alter C pools in the soil profile. We currently do not have the capacity to predict either the magnitude or rates of change in these C pools. In order to predict changes in grassland vegetation structure and the associated impacts on C cycling, we require a better understanding of the distribution of soil C pools at multiple soil depths, and the responses of these pools to changes in precipitation. The Land Surface Model (LSM) component of Earth System Models has the ability to capture these dynamic changes in ecosystem function, but currently lacks the data to accurately parameterize these processes at multiple depths within the soil profile. To support and perform this parameterization, we will undertake a detailed investigation of root and soil traits at varying soil depths, to capture the belowground impacts of changing dominant plant growth forms (grasses to shrubs) and the impacts of frequent drought.

We have developed a set of objectives that combine observational, experimental and modeling approaches to improve our ability to predict ecosystem consequences of shrub encroachment and drought in the US Great Plains region. These objectives are: (1) Quantify differences in aboveground (stem and leaf biomass) and belowground C pools (root C, microbial C, bulk soil C) using detailed excavations of entire mixed shrub-grass assemblages. We will also subsample portions of the rhizosphere for detailed root physiological and microbial activity measurements, to provide information on rates of change in soil C pools; (2) Using rainout shelters built over mature shrub-grass communities, we will experimentally reduce the amount of precipitation. Comparing responses between shrubs and grasses, we will measure differences in source-water use, above and belowground productivity, canopy water stress, soil C pools and microbial C-cycling activity, and changes in plant cover and community dynamics; (3) Using a global demographic LSM (CLM FATES), we will forecast the impacts of available water on shrub-grass cover in the central Great Plains region, and the resulting effects of these dynamics on ecosystem services (aboveground production, above- and belowground C budgets).

Results from this project will define the depth-resolved feedbacks of drought and dominant vegetation on belowground root architecture, soil microbial C cycling, and ecosystem C balance. The observation-experiment-modeling framework used here will improve our understanding of interactions and feedbacks between aboveground and belowground processes, by specifically measuring plant-soil-microbial traits at various depths in the soil profile. The details of these coupled interactions (plant-soil-microbial) will improve the representation of subsurface processes in LSMs and will improve forecasts of dynamic changes in ecosystem structure in grassland ecosystems.