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Biology subjects

Ward, N. D.

Publications and source records attributed to Ward, N. D..

4 recordsLinked to original sources

Harnessing artificial intelligence to automate environmental predictions

Predicting heterogeneous and non-linear processes remains a fundamental challenge in Earth sciences. Here, we present an artificial intelligence (AI)-guided framework that iteratively combines predictive modeling with targeted field sampling to rapidly improve environmental predictions. We demonstrate our workflow by predicting oxygen consumption, a key process of stream metabolism, across the contiguous United States (CONUS). Our approach consisted of 18 iterative loops of measurements and models, combining distributed participatory field sampling, lab analysis, automated machine learning (ML) predictions, and error and distinctiveness analyses to autonomously guide the next sampling at optimal site locations. Through our approach, we increased the predictive power of sediment oxygen consumption across CONUS by over fifteenfold between the first and last iteration. Relative to our last sampling iteration, our first sampling missed sites with high rates and underestimated median oxygen consumption rates by 68%. In addition to identifying areas of high oxygen consumption rates, iterations enabled refinement of laboratory and data handling methods, and engagement with a broad community of field researchers. We conclude that AI-guided iterative loops between targeted sampling and predictive modeling are a powerful and efficient approach for improving predictions of heterogeneous environmental processes.

ecology↗

Experimental flooding impacts soil biogeochemistry but not aboveground vegetation in a coastal forest

Rising sea levels and intensifying storms increase flooding pressure on coastal forests, triggering tree mortality, ecosystem transitions, and changes to the coastal carbon cycle. However, the mechanisms that drive coastal forest mortality remain elusive due to the complex interplay between belowground and aboveground processes during flooding disturbances and limitations of observations typically reported in coastal forest mortality studies. We used an ecosystem-scale manipulation to simulate hurricane-level flooding of a coastal forest. Monitoring real-time soil conditions and tree physiological responses, we observed consistent impacts on soil biogeochemistry aligned with belowground drivers of tree mortality, but no consistent responses in aboveground vegetation. Our findings provide unprecedented empirically based insight into the earliest stages of a hypothesized forest mortality spiral and offer critical benchmarks for predicting coastal forest resilience in the face of accelerating climate change. Significance StatementChanging sea levels and storms are causing more flooding in coastal forests. This flooding kills trees, changing how coastal ecosystems function, but we do not fully understand what factors determine whether forests survive flooding. We designed an ecosystem-scale experiment to answer this question, with controlled saltwater and freshwater floods equivalent to a hurricane in experimental forest plots. Flooding quickly changed soil conditions, but we have not yet observed consistent tree stress responses. Our study provides the most detailed measurements to date of how coastal forests respond to flooding in real time. These findings will help us better understand the early mechanisms and warning signs of forests threatened by flooding.

systems biology↗

Short-term coastal forest responses to a hurricane-scale freshwater and saltwater flooding experiment

Coastal upland forests are exposed to intensifying precipitation regimes and sea level rise, increasing tree mortality and transforming these coastal forests into wetland ecosystems. Despite these well-known risks, the differing degrees to which hydrological, biogeochemical, and biological components of upland forests respond to novel salinity exposure is relatively unknown. The Terrestrial Ecosystem Manipulation to Probe the Effects of Storm Treatments (TEMPEST) experiment decouples two distinct disturbances associated with hydrological extremes: (1) flooding from heavy precipitation and (2) exposure to saline conditions from storm surge. Here we describe the immediate effects of saltwater and freshwater flooding on hydrologic, biogeochemical and vegetation ecosystem components following the first experimental ecosystem-scale flooding event. The experimental flooding treatments temporarily and significantly impacted the systems hydrology but had subtler effects on biogeochemical and vegetation system components, suggesting that this temperate deciduous forest was resistant to a single novel flooding exposure, even if the water is saline. However, such episodic events can cause large transient shifts in conditions such as soil moisture and oxygen levels that may impact how the system responds to future perturbations. While the first TEMPEST event did not create substantial shifts in biogeochemical or vegetative processes, ecosystem level analysis of responses to experimental flooding through time will allow us to assess the impacts of flooding and salinity disturbances on the coupled above and belowground mechanisms driving coastal upland forest to wetland conversion.

ecology↗

Groundwater redox dynamics across the terrestrial-aquatic interface of Lake Erie coastal ecosystems

Groundwater biogeochemistry in coastal areas is spatially and temporally dynamic because fluctuations in groundwater level may cause alternate redox between distinct hydrological conditions. Recent studies have proposed connections between biogeochemistry and large-scale hydrological processes, specifically focusing on the role of redox-active compounds in changing the oxidation state during flooding and draining events. While water saturation generally results in a shift of redox-active compounds from electron donors to acceptors, the specific mechanisms underlying the transition of groundwater between oxidizing and reducing conditions in response to water level fluctuations are uncertain. To determine the effects of groundwater levels on redox dynamics, we monitored groundwater redox potential across the terrestrial-aquatic interface in Lake Erie coastal areas throughout the high and low-water seasons. In contrast to previously observed responses to flooding in soils, our results revealed patterns of oxidizing redox potentials during high-water and reducing during low-water periods. Furthermore, short-term fluctuations in water table levels significantly impacted the redox potential of groundwater when dissolved oxygen increased, and redox dynamics displayed voltage hysteresis in most events. Based on these findings, we propose that for improved predictions of microbial functions and biogeochemical cycles, redox-informed models should incorporate the antagonistic changes in groundwater redox balance compared to soils and consider the time lags in redox fluctuations. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/544684v1_figu1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@4d7a19org.highwire.dtl.DTLVardef@8b2b92org.highwire.dtl.DTLVardef@d9bc11org.highwire.dtl.DTLVardef@ca3e13_HPS_FORMAT_FIGEXP M_FIG Graphical AbstractConceptual diagram of groundwater redox fluctuations in coastal ecosystems. Large redox fluctuations are derived by dissolved oxygen inputs and smaller more frequent redox fluctuations are led by redox sensitive species leaching from topsoil. C_FIG

ecology↗