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1. Cumulative nitrogen enrichment alters the drivers of grassland overyielding

   https://doi.org/10.1038/s42003-024-05999-9  

   He, Miao; Barry, Kathryn E; Soons, Merel B; Allan, Eric; Cappelli, Seraina L; Craven, Dylan; Doležal, Jiří; Isbell, Forest; Lanta, Vojtěch; Lepš, Jan; et al (December 2024, Communications Biology)

   Abstract Effects of plant diversity on grassland productivity, or overyielding, are found to be robust to nutrient enrichment. However, the impact of cumulative nitrogen (N) addition (total N added over time) on overyielding and its drivers are underexplored. Synthesizing data from 15 multi-year grassland biodiversity experiments with N addition, we found that N addition decreases complementarity effects and increases selection effects proportionately, resulting in no overall change in overyielding regardless of N addition rate. However, we observed a convex relationship between overyielding and cumulative N addition, driven by a shift from complementarity to selection effects. This shift suggests diminishing positive interactions and an increasing contribution of a few dominant species with increasing N accumulation. Recognizing the importance of cumulative N addition is vital for understanding its impacts on grassland overyielding, contributing essential insights for biodiversity conservation and ecosystem resilience in the face of increasing N deposition. 

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2. Pathogen dilution, resource partitioning, and precipitation generate productivity benefits from plant diversity

   https://doi.org/10.1073/pnas.2518980122  

   Podzikowski, Laura Y; Burrill, Haley M; Wang, Guangzhou; Mecke, Kristen L; Hawkins, Jaide H; Wagner, Maggie R; Foster, Bryan L; Schultz, Peggy A; Bever, James D (December 2025, Proceedings of the National Academy of Sciences)

   Climate change and biodiversity loss threaten terrestrial productivity. Mitigating productivity loss from interactions between these global change drivers requires a mechanistic understanding of the forces generating productivity benefits from species richness (i.e., overyielding). Progress has been limited by two challenges: i) individual mechanisms can be highly context-dependent, yet multiple mechanisms can produce similar responses to functional diversity loss or altered climate, and ii) most experiments test short-term weather events rather than sustained changes in precipitation. We address these limitations using direct tests of multiple mechanisms within a sustained, full factorial manipulation of plant richness, composition, and precipitation within experimental grasslands. Precipitation consistently increased overyielding, as yield declined in monocultures and increased in polycultures, consistent with greater specialist pathogen accumulation in mesic conditions. Resource partitioning and specialist pathogen dilution—estimated from physiochemical trait dissimilarity and soil pathogen dissimilarity—were positive predictors of overyielding, relationships that strengthened over time. Moreover, overyielding was best explained by the joint influence of resource acquisition traits and pathogen dissimilarities, indicating that multiple mechanisms generated productivity responses to richness. These two mechanisms can explain the robust findings across systems that productivity increases with plant biodiversity. Our findings predict that biodiversity loss will be most damaging in wetter climates, where pathogen dilution amplifies the benefits of diversity. 

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3. Home‐field advantage, N‐priming and precipitation independently govern litter decomposition in a plant diversity manipulation

   https://doi.org/10.1111/1365-2435.14515  

   Podzikowski, Laura Y.; Duell, Eric B.; Burrill, Haley M.; Bever, James D. (February 2024, Functional Ecology)

   Abstract Litter decomposition facilitates the recycling of often limiting resources, which may promote plant productivity responses to diversity, that is, overyielding. However, the direct relationship between decomposition,k, and overyielding remains underexplored in grassland diversity manipulations.We test whether local adaptation of microbes, that is, home‐field advantage (HFA), N‐priming from plant inputs or precipitation drive decomposition and whether decomposition generates overyielding. Within a grassland diversity‐manipulation, altering plant richness (1, 2, 3 and 6 species), composition (communities composed of plants from a single‐family or multiple‐families) and precipitation (50% and 150% ambient growing season precipitation), we conducted a litter decomposition experiment. In spring 2020, we deployed four replicate switchgrass,Panicum virgatum, litter bags (1.59 mm mesh opening), collecting them over 7 months to estimate litterk.Precipitation was a strong, independent driver of decomposition. Switchgrass decomposition accelerated with grass richness and decelerated as phylogenetic dissimilarity from switchgrass increased, suggesting decomposition is fastest at ‘home’. However, decomposition slowed with switchgrass density. In plots that contained switchgrass, we observed no relationship between decomposition and fungal saprotroph dissimilarity from switchgrass. However, in plots without switchgrass, decomposition slowed with increasing saprotroph dissimilarity from switchgrass. Combined these findings suggest that HFA is strongest when closely related neighbours, that is, heterospecific neighbours, are present in the community, rather than other individuals of the same species, that is, conspecifics. Legumes accelerated decomposition with more litter N remaining in those plots, suggesting that N‐inputs from planted legumes are priming decomposition of litter C. However, decomposition and overyielding were unrelated in legume communities. While in grass communities, overyielding and decomposition were positively related and the relationship was strongest in plots with low densities of switchgrass, that is, with heterospecific neighbours.Combined these findings suggest that plant species richness and community composition stimulate litter decomposition through multiple mechanisms, including N‐priming, but only HFA from local adaptation of microbes on closely related species correlates with overyielding, likely through resource recycling. Our results link diversity with ecosystem processes facilitating above‐ground productivity. Whether diversity loss will affect litter decomposition, productivity or both is contingent on resident plant traits and whether a locally adapted soil microbiome is maintained. Read the freePlain Language Summaryfor this article on the Journal blog. 

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4. Plant-soil feedbacks help explain biodiversity-productivity relationships

   https://doi.org/10.1038/s42003-021-02329-1  

   Forero, Leslie E.; Kulmatiski, Andrew; Grenzer, Josephine; Norton, Jeanette M. (December 2021, Communications Biology)

   null (Ed.)

   Abstract Species-rich plant communities can produce twice as much aboveground biomass as monocultures, but the mechanisms remain unresolved. We tested whether plant-soil feedbacks (PSFs) can help explain these biodiversity-productivity relationships. Using a 16-species, factorial field experiment we found that plants created soils that changed subsequent plant growth by 27% and that this effect increased over time. When incorporated into simulation models, these PSFs improved predictions of plant community growth and explained 14% of overyielding. Here we show quantitative, field-based evidence that diversity maintains productivity by suppressing plant disease. Though this effect alone was modest, it helps constrain the role of factors, such as niche partitioning, that have been difficult to quantify. This improved understanding of biodiversity-productivity relationships has implications for agriculture, biofuel production and conservation. 

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5. Seasonal structural stability promoted by forest diversity and composition explains overyielding

   https://doi.org/10.1002/ecy.70055  

   Guzmán_Q, J Antonio; Park, Maria H; Williams, Laura J; Cavender‐Bares, Jeannine (March 2025, Ecology)

   Abstract The stability of forest productivity is a widely studied phenomenon often associated with tree species diversity. Yet, drivers of stability in forest structure and its consequences for forest productivity remain poorly understood. Using a large (10 ha) young tree diversity experiment, we evaluated how forest structure and multiple dimensions of diversity and composition are related to remotely sensed structural metrics and their stability through the growing season. We then examined whether structural stability (SS) across the growing season (April–October) could explain overyielding (i.e., the net biodiversity effect, NBE) in annual wood productivity. Using Uncrewed Aerial Vehicle‐Light Detecting and Ranging (UAV‐LiDAR), we surveyed experimental tree communities eight times at regular intervals from before bud break to after leaf senescence to derive metrics associated with canopy height heterogeneity, fractional plant cover, and forest structural complexity (based on fractal geometry). The inverse coefficients of variation for each of these three metrics through the season were used as measures of SS. These metrics were then coupled with annual tree inventories to evaluate their relationships with the NBE. Our findings indicate that wood volume and, to some extent, multiple dimensions of diversity and composition (i.e., taxonomic, phylogenetic, and functional) explain remotely sensed metrics of forest structure and their SS. Increases in wood volume as well as functional and phylogenetic diversity and variability (a measure of diversity independent of species richness) were linked to higher SS of forest complexity and canopy height heterogeneity. We further found that higher SS of forest complexity and fractional plant cover were associated with increased overyielding, which was mostly attributable to the complementarity effect. Structural equation models indicate that the stability of structural complexity explains more variation in NBE among plots than dimensions of diversity or variability, highlighting its value as an informative metric that likely integrates multiple drivers associated with overyielding. This study highlights the potential to integrate remote sensing and ecology to disentangle the role of forest SS in shaping ecological processes. 

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