An actionable anti-racism plan for geoscience organizations.

Geoscience organizations shape the discipline. They influence attitudes and expectations, set standards, and provide benefits to their members. Today, racism and discrimination limit the participation of, and promote hostility towards, members of minoritized groups within these critical geoscience spaces. This is particularly harmful for Black, Indigenous, and other people of color in geoscience and is further exacerbated along other axes of marginalization, including disability status and gender identity. Here we present a twenty-point anti-racism plan that organizations can implement to build an inclusive, equitable and accessible geoscience community. Enacting it will combat racism, discrimination, and the harassment of all members

Strong floristic distinctiveness across Neotropical successional forests

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained

Strong floristic distinctiveness across Neotropical successional forests.

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (<20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained

Biodiversity recovery of Neotropical secondary forests

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes. Copyright © 2019 The Authors, some rights reserved

Microbial Community Structure Varies Across Soil Organic Matter Aggregate Pools During Tropical Land Cover Change

Soil microorganisms regulate multiple input and loss pathways of soil carbon (C); hence, changes in microbial communities are expected to affect soil organic matter (SOM) cycling and storage. Despite this, very little is known about how microbes respond to changes in soil structure and vegetation with land use and land cover change. This study aimed to identify relationships between microbial community composition and the distribution of SOM among soil aggregate fractions to answer the following research questions: (1) Are different microbial groups associated with different SOM pools? and (2) How do these relationships differ with changes in vegetation during tropical forest succession? We measured microbial composition via phospholipid fatty acid (PLFA) analysis and C and nitrogen (N) concentrations on physically separated aggregate fractions of soils from pastures, secondary forests (40 and 90 years old) naturally regrowing on abandoned pastures, and reference or primary forests in Puerto Rico. We found different microbial communities associated with different soil aggregate fractions. Fungal to bacterial ratios decreased and gram-positive to gram-negative bacterial ratios increased with decreasing physical fraction size (from the macroaggregates to the silt and clay fractions). Microbial composition also varied with land cover type and forest successional stage, with consistent trends among soil fractions. These results show that the soil matrix and soil microsite properties play an important role in the spatial distribution of fungal and bacterial-dominated communities. The similarities in land cover effects on microbial communities at different spatial scales suggest similar controls may be influencing microbial composition with potential implications for SOM storage and turnover. In addition, the majority of C and N (relative to total soil C and fraction mass) was isolated in the macroaggregate-occluded silt and clay-sized fractions, suggesting that association with mineral surfaces, and not occlusion of particulate organic matter within aggregates, is the dominant stabilization mechanism for SOM in these highly-weathered, fine-textured soils. These results highlight the importance of soil aggregation in C storage but through mechanisms different than those reported for temperate grassland soils

Improving understanding of soil organic matter dynamics by triangulating theories, measurements, and models

Soil organic matter (SOM) turnover increasingly is conceptualized as a tension between accessibility to microorganisms and protection from decomposition via physical and chemical association with minerals in emerging soil biogeochemical theory. Yet, these components are missing from the original mathematical models of belowground carbon dynamics and remain underrepresented in more recent compartmental models that separate SOM into discrete pools with differing turnover times. Thus, a gap currently exists between the emergent understanding of SOM dynamics and our ability to improve terrestrial biogeochemical projections that rely on the existing models. In this opinion paper, we portray the SOM paradigm as a triangle composed of three nodes: conceptual theory, analytical measurement, and numerical models. In successful approaches, we contend that the nodes are connected—models capture the essential features of dominant theories while measurement tools generate data adequate to parameterize and evaluate the models—and balanced—models can inspire new theories via emergent behaviors, pushing empiricists to devise new measurements. Many exciting advances recently pushed the boundaries on one or more nodes. However, newly integrated triangles have yet to coalesce. We conclude that our ability to incorporate mechanisms of microbial decomposition and physicochemical protection into predictions of SOM change is limited by current disconnections and imbalances among theory, measurement, and modeling. Opportunities to reintegrate the three components of the SOM paradigm exist by carefully considering their linkages and feedbacks at specific scales of observation