Recipient Organization
INDIANA UNIVERSITY
JORDAN HALL 142
BLOOMINGTON,IN 47401
Performing Department
(N/A)
Non Technical Summary
Assessing the potential and performance of nature-based climate solutions in warmer and drier ecosystems requires a detailed understanding of the supply and demand of water from soils, plants, and the atmosphere. Plant water status and drought sensitivity is strongly controlled by how water flows across the gradient of water potentials between the soil, roots, plant xylem, leaves, and the atmosphere, which is commonly referred to as the "soil-plant-atmosphere continuum". However, characterizing water fluxes across the soil-plant-atmosphere continuum is difficult given how water potential measurements are currently made. Specifically, leaf water potential measurements, which are sporadically measured once or twice a day, rarely spatially align with soil water potential measurements that can be recorded every few minutes producing a substantial spatial-temporal mismatch. Thus, predicting the water movement between soils and plants influences our understanding of many biophysical processes, including microbial activity, transpiration, photosynthesis, soil infiltration, and root water uptake.Here, we ask three fundamental questions, Q1) What is the variability of root-zone soil water potential through space and time, and to what extent does plant cover and management regime affect that variability? Q2) How does accounting for the spatial heterogeneity of soil water potential improve explanations of plant growth and crop yields at the ecosystem scale? And Q3) how does integrating the variation in root-zone and soil water potential improve predictions of plant water use, specifically transpiration? To address these questions and reduce the mismatch of soil, root, and plant water potential measurements we will implement novel electrical resistivity imaging techniques to expand the spatial and temporal representation of soil water potential measurements. Moreover, we will use these novel data types to improve predictions of carbon and water exchange in two promising nature-based climate solutions, winter cover crops and naturally managed forests, for the Midwest United States. Our research objectives will improve confidence of biophysical models for predicting plant growth and carbon sequestration through the development of novel empirical observations across expanded spatio-temporal scales. Moreover, our proposed research is of particular importance for the USDA Partnerships for Climate-Smart Commodities aimed at combing private and public interests to develop and deploy climate-smart management practices for farmers, ranchers, and foresters.?
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Our goal is toconfrontspatial and temporal mismatch in water potential measurements, water available for plant growth,of both soil and the root-zone to reduce uncertainty in the plant water stress, thus bolstering predictions of net ecosystem productivity, evapotranspiration, and energy balance while simultaneously testing the performance of natural climate solutions. Additionally, we aim to produce a novel toolset toallow land managers insights on spatial and temporalvariation that will improve chances for successful seedling establishment.Our objectives are to:1) Quantify the variability of root-zone soil water potential in space and time and determine how management regimes or ecosystems influence the variability.2) Quantify how the spatial heterogeneity of soil water potential and soil-plant interactions improve explanations of net ecosystem productivity, evapotranspiration, and energy balance across different soils, ecosystems, and management regimes?3) Assess the how variation in soil water potential between the root-zone and bulk soils alters the interpretations of biophysical processes governed by the soil-plant water interactions (e.g., evapotranspiration).
Project Methods
Our work will take place in four intensive field sites: a) two broadleaf deciduous forests--Morgan Monroe State Forest and University of Michigan Biological Station--that are long-running AmeriFlux sites expressing high species richness, diverse water-use behaviors, and distinct soil characteristics (e.g., soil textures, depth), and b) two new corn/soy rotation cropland flux tower sites representing two co-located fields experiencing similar climates and soils, but different managements (traditionally managed versus cover crops). Together, these biomes capture two of the most promising nature-based climate solutions for the Midwestern US. Both Morgan Monroe State Forest located in southern Indiana, USA is dominated by approximately 90 years old secondary forest, with a mix of tulip poplar (L. tulipifera L.), white oak (Quercus abla L.), sassafras (Sassafras albidum (Nutt.) Nees), and sugar maple (Acer saccharum Marsh.). The University of Michigan Biological Station is the identical flux tower to Morgan-Monroe located in northern, Lower Michigan, USA with different hydroclimatic and conditions allowing us to test the root-zone water potential across a set of similar species and forest structures. The Michigan Biological station is dominated by late successional species such as red oak (Quercus rubra L.), red maple (Acer rubrum L.), white pine (Pinus strobus L.), American beech (Fagus grandifolia Ehrh.), and sugar maple (Acer saccharum Marsh.).The cropland sites are located in Northern Indiana, which is the setting of the USDA-NRCS funded Indiana Watershed Initiative project focused on watershed-scale investigations of cover crop impacts on water quality. Newly installed flux towers monitor sites corn/soy rotation fields in the watershed: one traditionally managed and one sown with winter cover cropping (i.e., cereal rye (Secale cereale) or similar cover crop). The water potential measurements here will compliment field-scale flux measurements, offering an unparalleled view on how cover crops impact not only carbon fluxes, but also local hydrologic cycling.All sites are equipped with eddy covariance measurements of net ecosystem productivity, evapotranspiration, and energy balance using infrared gas analyzers and sonic anemometers. Four-channel net radiometers will measure incident and outgoing short- and long-wave radiation, albedo, and surface temperature. Towers are also equipped with local micrometeorological instruments for measuring air temperature/humidity, and precipitation. Tower footprints are also instrumented with soil heat flux plates for quantifying soil energy fluxes. All sites have in situ soil water potential sensors measuring matric potential and soil moisture. In the forest, we will focus on the dominant tree species at Morgan-Monroe (i.e., white oak, tulip poplar, and sugar maple) and at the Michigan Biological Lab (i.e., red oak, red maple, and sugar maple) while water potential measurements will target corn and cover crops (e.g., cereal rye) depending on season in the agricultural fields. Measurements will be conducted using a combination of pressure chamber leaf water potential measurements and continuous xylem water potential measurements from stem or leaf psychrometers to quantify aboveground Ψ dynamics. Plant pressures will complement continuous sapflux measurements from thermal dissipation probes (built in lab) for estimating canopy-level transpiration and stomatal conductance in forested species. In the cover cropping fields, transpiration and stomatal measurements will be estimated using surface conductance derived from eddy flux measuring homogenous monocultured fields.Sites will be instrumented with electrical resistivity imaging transects in two disparate forests during the first year and two agricultural fields, during year two. Transects consist of 0.5 m spacing to focus on the top 5 m of soil. A Wenner array geometry will the maximize signal-to-noise ratio. Transects will span multiple species prioritizing areas with in situ soil moisture and water potential sensors to calibrate the electrical resistivity images. In the cover crop fields, transects will be systemically placed within the flux tower footprint where in situ co-located with soil moisture and water potential sensors. ERI transects will measure every 4 hours capturing diel and seasonal shifts in soil water.The soil hydrological properties will be measured using lab-based instruments from samples collected along the electrical resistivity images and co-located soil water potential sensors. Sampling will follow guidelines established by IU-B scientists as part of an ongoing collaboration with the AmeriFlux Management Project to generate information on soil water retention curves. Wet and dry ends of the SWRC will be measured using the HYPROP and WP4C (Meter Group), respectively.Statistical analysis will be conducted using R (R Development Core Team), RStudio, and Python languages. Timelapse inversions will be implemented in R2 and will be weighted based on reciprocal data errors. Timelapse analysis will be conducted based on model-differencing schemes within R2 where inversions are regularized to the result of the previous time step. Electrical images will be converted using Archie's transformation, mathematical equations for converting electrical conductance to soil water content and soil water potential. In situ soil water potential sensors within electrical imaging transects will be regressed against inversion models to serve as daily calibrations. The forest data and agricultural data will be analyzed separately. The linear mixed effect models will be used to analyze the seasonal dynamics of plant water potentials (xylem and leaf scale), evapotranspiration, net ecosystem productivity, against soil water potential, root-zone soil water potential, and the variation between them. Repeated measures, transect locations, and plot (forests or agricultural fields) will be treated as random variables. Model selection will determine model performance and most parsimonious models.