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1. General destabilizing effects of eutrophication on grassland productivity at multiple spatial scales

   https://doi.org/10.1038/s41467-020-19252-4  

   Hautier, Yann; Zhang, Pengfei; Loreau, Michel; Wilcox, Kevin R.; Seabloom, Eric W.; Borer, Elizabeth T.; Byrnes, Jarrett E.; Koerner, Sally E.; Komatsu, Kimberly J.; Lefcheck, Jonathan S.; et al (December 2020, Nature Communications)

   null (Ed.)

   Abstract Eutrophication is a widespread environmental change that usually reduces the stabilizing effect of plant diversity on productivity in local communities. Whether this effect is scale dependent remains to be elucidated. Here, we determine the relationship between plant diversity and temporal stability of productivity for 243 plant communities from 42 grasslands across the globe and quantify the effect of chronic fertilization on these relationships. Unfertilized local communities with more plant species exhibit greater asynchronous dynamics among species in response to natural environmental fluctuations, resulting in greater local stability (alpha stability). Moreover, neighborhood communities that have greater spatial variation in plant species composition within sites (higher beta diversity) have greater spatial asynchrony of productivity among communities, resulting in greater stability at the larger scale (gamma stability). Importantly, fertilization consistently weakens the contribution of plant diversity to both of these stabilizing mechanisms, thus diminishing the positive effect of biodiversity on stability at differing spatial scales. Our findings suggest that preserving grassland functional stability requires conservation of plant diversity within and among ecological communities. 

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2. Plant communities in Chicago residential neighborhoods show distinct spatial patterns

   https://doi.org/10.1016/j.landurbplan.2022.104663  

   Minor, Emily; Lopez, Bianca; Smith, Alexis; Johnson, Philip (April 2023, Landscape and Urban Planning)

   Residential yards and gardens can have surprisingly high plant diversity. However, we still do not understand all the factors that drive diversity in individual gardens, or how gardens scale up to create larger patterns of urban biodiversity. For example, social interactions between neighbors could affect whether they mimic each other’s yard design, affecting spatial turnover in plant communities. Further, socio-economic differences between neighborhoods might result in distinct plant assemblages across a city. In this paper, we used fieldwork, GIS, and spatial statistics to examine the variability in front yard vegetation—both cultivated and spontaneous plants—in 870 yards in Chicago, Illinois (USA). Our goals were to understand diversity and spatial patterning of plant communities in residential neighborhoods and how they vary with scale, considering alpha, beta, and gamma diversity. We addressed the following questions: (1) How do alpha, beta, and gamma diversity of cultivated and spontaneous plants vary between neighborhoods with different socioeconomic characteristics? (2) Within neighborhoods, do we see spatial autocorrelation in front-yard plant communities? If so, do those spatial patterns affect plant diversity at the neighborhood scale? We found diverse plant communities and distinct spatial patterns across Chicago. Richness and composition of both spontaneous and cultivated plants differed between neighborhoods, with some differences explained by socioeconomic factors such as education. Spontaneous and cultivated plants showed significant spatial autocorrelation, although that spatial autocorrelation generally did not influence neighborhood-scale diversity. Knowledge of these spatial patterns and their socioeconomic drivers could be exploited to increase adoption of environmentally-friendly yard management practices across a city. 

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3. Invasion‐mediated mutualism disruption is evident across heterogeneous environmental conditions and varying invasion intensities

   https://doi.org/10.1111/ecog.06434  

   Roche, Morgan D.; Pearse, Ian S.; Sofaer, Helen R.; Kivlin, Stephanie N.; Spyreas, Greg; Zaya, David N.; Kalisz, Susan (July 2023, Ecography)

   The impact of a biological invasion on native communities is expected to be uneven across invaded landscapes due to differences in local abiotic conditions, invader abundance, and traits and composition of the native community. One way to improve predictive ability about the impact of an invasive species given variable conditions is to exploit known mechanisms driving invasive species' success. Invasive plants frequently exhibit allelopathic traits, which can be directly toxic to plants or indirectly impact them via disruption of root symbionts, including mycorrhizal fungi. The indirect mechanism – mutualism disruption – is predicted to impact plants that rely on mycorrhizas but not affect non‐mycorrhizal plant species. To assess whether invader‐driven mutualism disruption explains observed changes in native plant communities, we analyzed long‐term (1998–2018) plant cover data from forest plots across the state of Illinois. We evaluated native plant communities experiencing a range of abundance of invasive allelopathic garlic mustardAlliaria petiolataand varying environmental conditions. Consistent with the mutualism disruption hypothesis, we showed that as garlic mustard abundance increased over time in 0.25 m²sampling quadrats, the abundance of mycorrhizal plant species decreased, but non‐mycorrhizal plant species did not. Over space and time, garlic mustard abundance predicted plant abundances and diversity at the quadrat level, but this relationship was not present at a larger scale when quadrats were aggregated within sites. Garlic mustard's impact on the plant community was highly localized, yet it was as important as abiotic variables for predicting local plant diversity. We showed that garlic mustard abundance was a key predictor of patterns of plant diversity across invasion intensity and environmental heterogeneity in a way that is consistent with mutualism disruption. Our work indicates that the mutualism disruption hypothesis can provide generalizable predictions of the impacts of allelopathic invasive plants that are evident at a broad spatial scale. 

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4. Diversity–stability relationships across organism groups and ecosystem types become decoupled across spatial scales

   https://doi.org/10.1002/ecy.4136  

   Wisnoski, Nathan I.; Andrade, Riley; Castorani, Max C. N.; Catano, Christopher P.; Compagnoni, Aldo; Lamy, Thomas; Lany, Nina K.; Marazzi, Luca; Record, Sydne; Smith, Annie C.; et al (July 2023, Ecology)

   Abstract The relationship between biodiversity and stability, or its inverse, temporal variability, is multidimensional and complex. Temporal variability in aggregate properties, like total biomass or abundance, is typically lower in communities with higher species diversity (i.e., the diversity–stability relationship [DSR]). At broader spatial extents, regional‐scale aggregate variability is also lower with higher regional diversity (in plant systems) and with lower spatial synchrony. However, focusing exclusively on aggregate properties of communities may overlook potentially destabilizing compositional shifts. It is not yet clear how diversity is related to different components of variability across spatial scales, nor whether regional DSRs emerge across a broad range of organisms and ecosystem types. To test these questions, we compiled a large collection of long‐term metacommunity data spanning a wide range of taxonomic groups (e.g., birds, fish, plants, invertebrates) and ecosystem types (e.g., deserts, forests, oceans). We applied a newly developed quantitative framework for jointly analyzing aggregate and compositional variability across scales. We quantified DSRs for composition and aggregate variability in local communities and metacommunities. At the local scale, more diverse communities were less variable, but this effect was stronger for aggregate than compositional properties. We found no stabilizing effect of γ‐diversity on metacommunity variability, but β‐diversity played a strong role in reducing compositional spatial synchrony, which reduced regional variability. Spatial synchrony differed among taxa, suggesting differences in stabilization by spatial processes. However, metacommunity variability was more strongly driven by local variability than by spatial synchrony. Across a broader range of taxa, our results suggest that high γ‐diversity does not consistently stabilize aggregate properties at regional scales without sufficient spatial β‐diversity to reduce spatial synchrony. 

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5. Tundra fires and surface subsidence increase spectral diversity on the Yukon–Kuskokwim Delta, Alaska

   https://doi.org/10.1088/2752-664X/ad9282  

   Anderson, D_P; Michaelides, R_J; Chen, W.; Frost, G_V; Macander, M_J; Lara, M_J (December 2024, Environmental Research: Ecology)

   Abstract Tundra fires can dramatically influence plant species cover and abundance, organic layer depth, and the magnitude of seasonal permafrost thaw. However, knowledge of the impact of wildfire on short and long-term interactions between vegetation and permafrost thaw remains limited. Here, we evaluate the spatial and temporal interactions between wildfire disturbance and surface subsidence on a remotely derived proxy for species diversity (i.e. spectral diversity (SD)) of 16 fire scars within the Izaviknek and Kingaglia uplands of southwestern Alaska’s Yukon–Kuskokwim Delta with burn dates between 1971 and 2015. SD was calculated as the sum of squared spectral variance of pixel spectra from the mean spectra, within a plant community (analogous to alpha diversity), between plant communities (beta diversity), and across terrain composed of a mosaic of communities (gamma diversity). Surface subsidence was calculated from spaceborne interferometric synthetic aperture radar data from Sentinel-1. Results indicate the burn scars had consistently lower total gamma diversity and greater rates of subsidence than paired unburned reference areas, where both gamma diversity (R²= 0.74,p< 0.001) and relative subsidence (R²= 0.86,p< 0.001) decreased with the time since burn. Compared to older burn scars, young scars had higher gamma spectral diversities (0.013 and 0.005) and greater subsidence rates (−0.097 cm day⁻¹and −0.053 cm day⁻¹). Communities subsiding at higher rates had higher gamma diversities (R²= 0.81,p< 0.001). Results indicate that rates of post-fire vegetation succession are amplified by the thickening of active layers and surface subsidence that increases both spectral and species diversity over 15 years following fire. These results support the idea that SD may be used as a remotely sensed analog of species diversity, used to advance knowledge of the trajectories of plant community change in response to interacting arctic disturbance regimes. 

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