More Like this

1. Redefining temperate forest responses to climate and disturbance in the eastern United States: New insights at the mesoscale

   https://doi.org/10.1111/geb.12876  

   Druckenbrod, Daniel L. ; Martin‐Benito, Dario ; Orwig, David A. ; Pederson, Neil ; Poulter, Benjamin ; Renwick, Katherine M. ; Shugart, Herman H. ; Mayfield, ed., Margaret ( January 2019 , Global Ecology and Biogeography)

   Climate and disturbance alter forest dynamics, from individual trees to biomes and from years to millennia, leaving legacies that vary with local, meso‐ and macroscales. Motivated by recent insights in temperate forests, we argue that temporal and spatial extents equivalent to that of the underlying drivers are necessary to characterize forest dynamics across scales. We focus specifically on characterizing mesoscale forest dynamics because they bridge fine‐scale (local) processes and the continental scale (macrosystems) in ways that are highly relevant for climate change science and ecosystem management. We revisit ecological concepts related to spatial and temporal scales and discuss approaches to gain a better understanding of climate–forest dynamics across scales.

   Eastern USA.

   Last century to present.

   Temperate broadleaf forests.

   We review regional literature of past tree mortality studies associated with climate to identify mesoscale climate‐driven disturbance events. Using a dynamic vegetation model, we then simulate how these forests respond to a typical climate‐driven disturbance.

   By identifying compound disturbance events from both a literature review and simulation modelling, we find that synchronous patterns of drought‐driven mortality at mesoscales have been overlooked within these forests.

   As ecologists, land managers and policy‐makers consider the intertwined drivers of climate and disturbance, a focus on spatio‐temporal scales equivalent to those of the drivers will provide insight into long‐term forest change, such as drought impacts. Spatially extensive studies should also have a long temporal scale to provide insight into pathways for forest change, evaluate predictions from dynamic forest models and inform development of global vegetation models. We recommend integrating data collected from spatially well‐replicated networks (e.g., archaeological, historical or palaeoecological data), consisting of centuries‐long, high‐resolution records, with models to characterize better the mesoscale response of forests to climate change in the past and in the future.

    

   more » « less
2. Biotic and abiotic drivers of plant–pollinator community assembly across wildfire gradients

   https://doi.org/10.1111/1365-2745.13530  

   LaManna, Joseph A. ; Burkle, Laura A. ; Belote, R. Travis ; Myers, Jonathan A. ; Bartomeus, ed., Ignasi ( November 2020 , Journal of Ecology)

   Understanding how abiotic disturbance and biotic interactions determine pollinator and flowering‐plant diversity is critically important given global climate change and widespread pollinator declines. To predict responses of pollinators and flowering‐plant communities to changes in wildfire disturbance, a mechanistic understanding of how these two trophic levels respond to wildfire severity is needed.

   We compared site‐to‐site variation in community composition (β‐diversity), species richness and abundances of pollinators and flowering plants among landscapes with no recent wildfire (unburned), mixed‐severity wildfire and high‐severity wildfire in three sites across the Northern Rockies Ecoregion, USA. We used variation partitioning to assess the relative contributions of wildfire, other abiotic variables (climate, soils and topography) and biotic associations among plant and pollinator composition to community assembly of both trophic levels.

   Wildfire disturbance generally increased species richness and total abundance, but decreasedβ‐diversity, of both pollinators and flowering plants. However, reductions inβ‐diversity from wildfire appeared to result from increased abundances following fires, resulting in higher local species richness of pollinators and flowers in burned than unburned landscapes. After accounting for differences in abundance, standardized effect sizes ofβ‐diversity were higher in burned than unburned landscapes, suggesting that wildfire enhances non‐random assortment of pollinator and flowering‐plant species among local communities.

   Wildfire disturbance mediated the relative importance of mutualistic associations toβ‐diversity of pollinators and flowering plants. The influence of pollinatorβ‐diversity on flowering‐plantβ‐diversity increased with wildfire severity, whereas the influence of flowering‐plantβ‐diversity on pollinatorβ‐diversity was greater in mixed‐severity than high‐severity wildfire or unburned landscapes. Moreover, biotic associations among pollinator and plant species explained substantial variation inβ‐diversity of both trophic levels beyond what could be explained by wildfire and all other abiotic and spatial factors combined.

   Synthesis. Wildfire disturbance and plant–pollinator interactions both strongly influenced the assembly of pollinator and flowering‐plant communities at local and regional scales. However, biotic interactions were generally more important drivers of community assembly in disturbed than undisturbed landscapes. As wildfire regimes continue to change globally, predicting its effects on biodiversity will require a deeper understanding of the ecological processes that mediate biotic interactions among linked trophic levels.

    

   more » « less
3. Pyrodiversity begets plant–pollinator community diversity

   https://doi.org/10.1111/gcb.13236  

   Ponisio, Lauren C. ; Wilkin, Kate ; M'Gonigle, Leithen K. ; Kulhanek, Kelly ; Cook, Lindsay ; Thorp, Robbin ; Griswold, Terry ; Kremen, Claire ( February 2016 , Global Change Biology)

   Fire has a major impact on the structure and function of many ecosystems globally. Pyrodiversity, the diversity of fires within a region (where diversity is based on fire characteristics such as extent, severity, and frequency), has been hypothesized to promote biodiversity, but changing climate and land management practices have eroded pyrodiversity. To assess whether changes in pyrodiversity will have impacts on ecological communities, we must first understand the mechanisms that might enable pyrodiversity to sustain biodiversity, and how such changes might interact with other disturbances such as drought. Focusing on plant–pollinator communities in mixed‐conifer forest with frequent fire in Yosemite National Park, California, we examine how pyrodiversity, combined with drought intensity, influences those communities. We find that pyrodiversity is positively related to the richness of the pollinators, flowering plants, and plant–pollinator interactions. On average, a 5% increase in pyrodiversity led to the gain of approximately one pollinator and one flowering plant species and nearly two interactions. We also find that a diversity of fire characteristics contributes to the spatial heterogeneity (β‐diversity) of plant and pollinator communities. Lastly, we find evidence that fire diversity buffers pollinator communities against the effects of drought‐induced floral resource scarcity. Fire diversity is thus important for the maintenance of flowering plant and pollinator diversity and predicted shifts in fire regimes to include less pyrodiversity compounded with increasing drought occurrence will negatively influence the richness of these communities in this and other forested ecosystems. In addition, lower heterogeneity of fire severity may act to reduce spatial turnover of plant–pollinator communities. The heterogeneity of community composition is a primary determinant of the total species diversity present in a landscape, and thus, lower pyrodiversity may negatively affect the richness of plant–pollinator communities across large spatial scales.

    

   more » « less
4. Using Leaf δ13C to Assess Water Use Efficiency within Plant Communities Across a Successional Gradient in Temperate and Tropical Forests

   Meier, Josephine ; Lowe, Alexander ; Both, Sabine ; Oishi, A C ; Aguirre, E ; Strömberg, C A ( July 2023 , Botany)

   Understanding how plant communities of the past have responded to disturbance events can provide valuable insights when managing our natural resources and assessing human impacts on ecosystems. The geologic record has the potential to reflect these responses through the analysis of functional traits, which relate directly to plant function and ecosystem strategy. There is currently little evidence of how functional traits measurable in fossil leaves vary across succession in different forest types. Because of this, there is a limited ability to identify disturbance as the primary driver of vegetation change within the fossil record. To improve this ability, this study analyzes the carbon stable isotopic composition (δ 13C) of bulk organic matter sampled at the community-scale across successional gradients in a temperate deciduous forest (North Carolina, USA) and compares them against values from a previous study across succession in a tropical evergreen forest (Malaysian Borneo). Leaf δ13C is representative of a plant's water use efficiency (WUE), an important axis of ecological strategy representing the carbon assimilated per water lost in a plant during photosynthesis. Leaf δ13C as a functional trait has the advantage that it is often preserved during leaf fossilization and, integrated across a plant community, can be informative about prevalent ecological strategies, functional diversity , and community assembly dynamics. In Borneo, the community-weighted mean of leaf δ13C to be highest in early-succession plots, indicative of a higher WUE in plant communities closely following a disturbance event. Old growth plots were found to have a lower δ13C, and thus a more conservative WUE. This study will further investigate if this trend is followed within temperate forests, which is important as many mid-late Cenozoic plant assemblages come from what would have been temperate regions. Developing a method of identifying disturbances within the geologic record, will improve the ability to discern drivers of plant community change in the past. This improved knowledge will help guide management decisions across a range of ecosystems. 

   more » « less
5. Demographic trade-offs and functional shifts in a hurricane-impacted tropical forest

   https://doi.org/10.1093/aob/mcad004  

   Umaña, María Natalia ; Needham, Jessica ; Forero-Montaña, Jimena ; Nytch, Christopher J. ; Swenson, Nathan G. ; Thompson, Jill ; Uriarte, María ; Zimmerman, Jess K. ( January 2023 , Annals of Botany)

   Understanding shifts in the demographic and functional composition of forests after major natural disturbances has become increasingly relevant given the accelerating rates of climate change and elevated frequency of natural disturbances. Although plant demographic strategies are often described across a slow–fast continuum, severe and frequent disturbance events influencing demographic processes may alter the demographic trade-offs and the functional composition of forests. We examined demographic trade-offs and the shifts in functional traits in a hurricane-disturbed forest using long-term data from the Luquillo Forest Dynamics Plot (LFPD) in Puerto Rico.

   We analysed information on growth, survival, seed rain and seedling recruitment for 30 woody species in the LFDP. In addition, we compiled data on leaf, seed and wood functional traits that capture the main ecological strategies for plants. We used this information to identify the main axes of demographic variation for this forest community and evaluate shifts in community-weighted means for traits from 2000 to 2016.

   The previously identified growth–survival trade-off was not observed. Instead, we identified a fecundity–growth trade-off and an axis representing seedling-to-adult survival. Both axes formed dimensions independent of resprouting ability. Also, changes in tree species composition during the post-hurricane period reflected a directional shift from seedling and tree communities dominated by acquisitive towards conservative leaf economics traits and large seed mass. Wood specific gravity, however, did not show significant directional changes over time.

   Our study demonstrates that tree demographic strategies coping with frequent storms and hurricane disturbances deviate from strategies typically observed in undisturbed forests, yet the shifts in functional composition still conform to the expected changes from acquisitive to conservative resource-uptake strategies expected over succession. In the face of increased rates of natural and anthropogenic disturbance in tropical regions, our results anticipate shifts in species demographic trade-offs and different functional dimensions.

    

   more » « less