Linking root and soil microbial stress metabolism to watershed biogeochemistry under rapid, year-round environmental change
Active Dates | 8/15/2021-8/14/2024 |
---|---|
Program Area | Environmental Systems Science |
Project Description
Climate change
is occurring rapidly in northern forests, where air temperatures and precipitation are rising, but winter snowpack is shrinking, leading to more frequent soil freeze/thaw cycles in winter. These contrasting changes in soil temperature-moisture regimes are a major stressor for plant roots and soil microorganisms and can lead to changes in cycling of carbon and nutrients through whole forested
ecosystems.
Warming during the growing season may destabilize and release
soil carbon
(C) and
nitrogen
(N) into soil solution, but the severe thermal impact of soil freeze/thaw cycles in winter could magnify (in the case of N) or reverse (in the case of C) these losses. The combination of warming and increased freeze/thaw cycles appear to initially induce oxidation-reduction stress that selects for anaerobic N cycling-microbes and metal oxidizers, while shifting the majority of aerobic microbial C-cycling activity into deeper soil layers during winter. Soil
microbes
are also evolving under these extreme conditions to increase decomposition of plant and soil C, but decrease decomposition of organic P, potentially decoupling C, N, and P outputs to associated aquatic ecosystems. These climate change effects on microbial metabolism could impact the export of dissolved organic matter and nutrients in ways that may explain longer-term changes in stream water chemistry and productivity of forested
watersheds,
yet are poorly represented in ecosystem models. The objective of this proposed research is to improve mechanistic understanding and model representation of the combined effects of warming during the growing season and soil freeze/thaw cycles in winter on belowground biogeochemical cycles in northeastern forests. Our overarching hypothesis is that under climate change across seasons, microbes and plants exhibit a trade-off between stress metabolism and soil C, N, and P uptake and assimilation (short term) and
biomass
stabilization (longer term) that scales up to impact soil carbon and nutrient export at the watershed-level.
To test this hypothesis, we propose a model-data integration study using the Climate Change Across Seasons Experiment (CCASE) at the Hubbard Brook Experimental Forest (HBEF) and a complementary plot-to-watershed-level biogeochemistry model, PnET-BGC. At CCASE, replicate field plots receive one of three climate treatments: growing season warming (+5°C above ambient), warming + freeze/thaw cycles (+5°C above ambient in growing season plus up to four freeze/thaw cycles in winter), and reference conditions (no treatment). We propose to couple new seasonal belowground biogeochemistry measurements at CCASE (net and gross C, N, and P fluxes and rates of plant- and microbial-derived DOC/N/P production in soil solution) in organic and mineral soil horizons, with -omics data on soil microbial communities (population genomics, metagenomics, metabolomics) to reconstruct potential plant and microbial C, N, and P metabolism and export to the HBEF watershed over the past decade. To quantify the evolutionary trajectory of microbial evolution in situ during this time period, we will combine soil metagenomics datasets with new high-throughput characterizations of trait and gene evolution in individual soil bacteria and fungi collected from CCASE. To develop an integrated, scale-aware understanding of the consequences of evolving microbial stress and resource use traits for forest nutrient and C retention, we will incorporate both immediate and evolved responses of microbial C, N, and P cycling into new versions of PnET-BGC by applying an evolutionary algorithm to control specific C, N and P flux fluxes. Outputs of the revised PnET-BGC will be validated with over 40 years of existing forest C, N, and P pool and flux data from HBEF watersheds. By leveraging the versatile PnET-BGC model with a genes-to-ecosystems analysis of C, N, and P cycling at CCASE, this research will test our conceptual understanding of plant and microbial physiology responses to severe, compounding soil temperature perturbations across seasons, as well as the utility of a forest stand-level manipulative climate change experiment to understand the biogeochemical dynamics of a forest watershed undergoing rapid environmental change.
To test this hypothesis, we propose a model-data integration study using the Climate Change Across Seasons Experiment (CCASE) at the Hubbard Brook Experimental Forest (HBEF) and a complementary plot-to-watershed-level biogeochemistry model, PnET-BGC. At CCASE, replicate field plots receive one of three climate treatments: growing season warming (+5°C above ambient), warming + freeze/thaw cycles (+5°C above ambient in growing season plus up to four freeze/thaw cycles in winter), and reference conditions (no treatment). We propose to couple new seasonal belowground biogeochemistry measurements at CCASE (net and gross C, N, and P fluxes and rates of plant- and microbial-derived DOC/N/P production in soil solution) in organic and mineral soil horizons, with -omics data on soil microbial communities (population genomics, metagenomics, metabolomics) to reconstruct potential plant and microbial C, N, and P metabolism and export to the HBEF watershed over the past decade. To quantify the evolutionary trajectory of microbial evolution in situ during this time period, we will combine soil metagenomics datasets with new high-throughput characterizations of trait and gene evolution in individual soil bacteria and fungi collected from CCASE. To develop an integrated, scale-aware understanding of the consequences of evolving microbial stress and resource use traits for forest nutrient and C retention, we will incorporate both immediate and evolved responses of microbial C, N, and P cycling into new versions of PnET-BGC by applying an evolutionary algorithm to control specific C, N and P flux fluxes. Outputs of the revised PnET-BGC will be validated with over 40 years of existing forest C, N, and P pool and flux data from HBEF watersheds. By leveraging the versatile PnET-BGC model with a genes-to-ecosystems analysis of C, N, and P cycling at CCASE, this research will test our conceptual understanding of plant and microbial physiology responses to severe, compounding soil temperature perturbations across seasons, as well as the utility of a forest stand-level manipulative climate change experiment to understand the biogeochemical dynamics of a forest watershed undergoing rapid environmental change.
Award Recipient(s)
- Boston University (PI: Bhatnagar, Jennifer)