Biology subjects

Bond-Lamberty, B.

Publications and source records attributed to Bond-Lamberty, B..

7 recordsLinked to original sources

bioRxiv2026

Drought duration does not impact soil microbiome resilience

Increasing global droughts exert large but poorly understood effects on the microbial communities and ecology of soil. Microbial communities generally show resilience and return to pre-drought conditions when short-term droughted soils are rewet; soils exposed to long-term drought, however, often show a lag upon rewetting, after which microbial communities may or may not return to their pre-stressed conditions. Though short-term droughts have been widely studied, long-term drought manipulation experiments remain rare, especially those that compare microbial response to short-term and long-term drought in tandem. We conducted a 1000-day drought simulation in controlled laboratory conditions with soil cores collected from a tidal freshwater ecosystem in Washington state, USA, and subsequently exposed them to rewetting for two weeks. We also included short-term (30-day and 90-day) drought and rewet treatments to directly compare microbial community and organic matter responses across drought durations. We found distinct microbial taxa belonging to Firmicutes and Actinobacteria enriched after the 1000-day drought, but not after the short-term droughts. While we hypothesized that the microbial community would recover from a short-term drought after rewetting to resemble pre-drought conditions, our results revealed community dissimilarities between rewet and pre-drought conditions across all drought durations. These findings suggest unique microbial life history strategies within certain microbial phyla that make them successful colonizers during an extended drought period, and the influence of environmental and physiological context on microbial responses to rewetting. ImportanceDroughts are increasing in frequency and intensity globally with severe implications for ecosystem services and soil functions. It is important to understand how long-term drought impacts soil microbial communities and organic matter chemistry to better predict future ecosystem responses to sustained moisture deficit conditions. We subjected soils to short-term (30 and 90 days) and long-term (1000 days) drought treatments and subsequently rewetted them to understand microbiome recovery to pre-drought conditions. Our results showed that prolonged drought drastically changes the microbial community and soil organic matter profile compared to short-term drought. While we expected the soil microbiome to recover upon rewetting after short-term drought, our results showed an altered microbiome composition, compared to pre-drought conditions, for both short-and long-term drought, suggesting microbial responses to soil rewetting was independent of drought duration imposed. These results provide important insights into soil biological and chemical functions that remain sensitive to change under fluctuating soil moisture conditions and future drought scenarios.

ecology↗

bioRxiv2025

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↗

bioRxiv2025

A large global soil carbon sink informed by repeated soil samplings

Partitioning the terrestrial carbon sink between vegetation and soil is crucial for predicting future climate change, but the role of soils remains poorly quantified. Here, we compiled 3,099 soil organic carbon time series spanning five decades. We found a global soil organic carbon sink of 1.83 {+/-} 0.9 (mean {+/-} SE) petagrams per year from 1992 to 2020, driven by extratropical young forests, boreal old forests, and grasslands, while trends in tropical ecosystems remain uncertain. Our findings suggest the net land sink resides almost exclusively belowground as soil carbon, emphasizing the global opportunity of soil conservation and restoration for climate mitigation.

ecology↗

bioRxiv2025

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↗

bioRxiv2024

The global spectrum of tree crown architecture

Trees can differ enormously in their crown architectural traits, such as the scaling relationships that link their height and crown size to their stem diameter. Yet despite the importance of crown architecture in shaping the structure and function of woody ecosystems, we lack a complete picture of what drives this incredible diversity in crown shapes. Using data from >500,000 globally distributed trees, we explored how climate, disturbance, competition, functional traits, and evolutionary history constrain the height, crown size and shape of the worlds tree species. We found that variation in height scaling relationships was primarily controlled by water availability and light competition. Conversely, crown width was predominantly shaped by exposure to wind and fire, while also covarying with other functional traits related to mechanical stability and photosynthesis. Additionally, several plant lineages had crown architectures that defy their environments, such as the exceedingly slender dipterocarps of Southeast Asia, or the extremely wide crowns of legumes in African savannas. Our study charts the global spectrum of tree crown architectural types. It provides a roadmap for integrating crown architecture with vegetation models and remote sensing observations, so that we may better understand the processes that shape the 3D structure of woody ecosystems.

ecology↗

bioRxiv2020

Controls on and consequences of specific leaf area variation with permafrost depth in a boreal forest

Specific leaf area (SLA, leaf area per unit dry mass) is a key canopy structural characteristic, a measure of photosynthetic capacity, and an important input into many terrestrial process models. Although many studies have examined SLA variation, relatively few data exist from high latitude, climate-sensitive permafrost regions. We measured SLA and soil and topographic properties across a boreal forest permafrost transition, in which forest composition changed as permafrost deepened from 54 to >150 cm over 75 m hillslope transects in Caribou-Poker Creeks Research Watershed, Alaska. We characterized both linear and threshold relationships between topographic and edaphic variables and SLA and developed a conceptual model of these relationships. We found that the depth of the soil active layer above permafrost was significantly and positively correlated with SLA for both coniferous and deciduous boreal tree species. Intraspecific SLA variation was associated with a fivefold increase in net primary production, suggesting that changes in active layer depth due to permafrost thaw could strongly influence ecosystem productivity. While this is an exploratory study to begin understanding SLA variation in a non-contiguous permafrost system, our results indicate the need for more extensive evaluation across larger spatial domains. These empirical relationships and associated uncertainty can be incorporated into ecosystem models that use dynamic traits, improving our ability to predict ecosystem-level carbon cycling responses to ongoing climate change.

ecology↗

bioRxiv2016

Critical transitions and the fragmenting of global forests

The replacement of forest areas with human-dominated landscapes usually leads to fragmentation, altering the structure and function of the forest. Here we studied the dynamics of forest patch sizes at a global level, examining signals of a critical transition from an unfragmented to a fragmented state, using the MODIS vegetation continuous field. We defined wide regions of connected forest across continents and big islands, and combined five criteria, including the distribution of patch sizes and the fluctuations of the largest patch over the last sixteen years, to evaluate the closeness of each region to a fragmentation threshold. Regions with the highest deforestation rates--South America, Southeast Asia, Africa--all met these criteria and may thus be near a critical fragmentation threshold. This implies that if current forest loss rates are maintained, wide continental areas could suddenly fragment, triggering extensive species loss and degradation of ecosystems services.

ecology↗