Ecology Letters最新文献

Nature-based climate solutions rely on the assumption that restoring plant diversity enhances soil organic carbon (SOC) sequestration. However, the persistence of SOC is threatened by the positive priming effects, where fresh plant carbon inputs accelerate the decomposition of native SOC. It remains unclear how increasing plant diversity impacts the soil priming effects. Here, using a natural tree species diversity gradient in a subtropical forest, we show that higher tree diversity was strongly associated with suppressed soil priming effects, attributable to reduced mineral protection of SOC and alleviated microbial energy limitation. Microbial community consequently shifts toward fast-growing specialists that outcompete decomposers of chemically complex carbon. Our study reveals that tree species diversity is a key regulator of SOC persistence and demonstrates that the biodiversity-driven priming suppression should be explicitly incorporated into nature-based climate solutions and Earth system models to reduce critical uncertainties in carbon cycle projections.

Understanding how plants influence each other's spatial distribution is pivotal not only for interpreting current communities, but also for anticipating their responses to global changes. The combination of high-resolution, multi-scale sampling and novel statistical frameworks now enables us to identify species aggregations and segregations within their local co-occurrences. By applying this approach to approximately 800 plant species and their communities across the French Alps, we discovered that local species associations are dependent on soil acidity and nitrogen rather than climate. By building a regional network from these associations, we identified a centralised core comprising a few dominant, stress-tolerant graminoids and shrubs with high leaf dry matter content and no unique functional roles. Our findings demonstrate that plant community assembly is less dependent on random co-occurrence and more dependent on segregation around a few dominant, stress-tolerant species, with soil conditions modulating the outcome of local associations.

Endotherms exhibit metabolic allometric slopes of 0.75, which were long viewed as evolutionary constraints but which are increasingly questioned. In insects, allometric relationships between body size and metabolism are understudied. We used comparative phylogenetic methods to investigate macroevolution of metabolic allometry in Odonata (dragonflies and damselflies), an insect group with a unique ecology and dramatic macroevolution of body size. We found an interspecific allometric slope close to one (isometry). Metabolic rates evolved gradually with a weak pullback force and multiple shifts in metabolic optima, body size and flight behaviour. Cell size, nucleus size and body surface area did not explain this steep allometric slope. Instead, metabolic isometry likely reflects the high aerobic demands of flight and evolutionary increases in body size via cell numbers rather than cell size. Our results challenge traditional allometric theories and suggest that metabolic allometries can and do evolve, with far-reaching implications for insect size evolution.

Terrestrial ecosystems serve as a major carbon (C) sink, but the increasing frequency and intensity of drought threaten the C sink and ecological communities. A comprehensive understanding of the change in ecosystem productivity due to the direct effect versus the legacy effect of drought is still lacking. We quantify the magnitude change in terrestrial gross primary production (GPP) globally due to both direct and long-term legacy effects. We find that the direct effect causes significant GPP decreases in magnitude of -5.94% [-13.40%, -3.21%] per year, while the legacy effect-induced GPP change is weaker and non-significant at a global scale. Drought legacy effects, however, are detectable in dry sub-humid regions. The direct effect-induced change is highly correlated with that of the legacy effect, and rooting depth is a key driver for both. These findings demonstrate the current resilience of global ecosystems to drought but underscore the long-term vulnerability of dryland ecosystems.

Phylogenetic divergence between species may weaken both negative and positive biotic interactions. Whether, as a result, divergent species aggregate or segregate remains unclear. These interactions differ among lineages, and without immigration, the effects of interactions might be overridden by dispersal limitation. We studied changes in co-occurrence across 5 years for 1770 pairs of grassland species drawn primarily from four major lineages (families), reducing dispersal limitation by seed addition. Across all lineages, changes in co-occurrence were almost unrelated to phylogenetic divergence, partly reflecting opposing relationships within two groups of families: Fabaceae/Poaceae, where more divergent species segregated, versus Asteraceae/Apiaceae, where they aggregated. Dispersal limitation through lack of immigration existed, without eliminating divergence effects. We conclude that species assembly differed between major lineages, with spatial aggregation in Asteraceae/Apiaceae possibly reflecting limiting similarity, whereas segregation in Fabaceae/Poaceae may reflect mutualist incompatibility or asymmetric competition. These processes could feedback on within-lineage diversification.

The communities of unicellular microbes (bacteria, protists and yeasts) that underpin ecosystems are changing. In warmer conditions, protists tend to shrink, but the consequences of these changes in size are unclear. We show preliminary evidence that warming-mediated declines in cell size observed in protists also apply to bacteria and yeasts. Predicting the consequences of these warming-mediated size declines requires that the relationships between cell size and key functional traits are well-characterised. We show that the critical relationship between unicellular size and energy use-that is, metabolic scaling-has been systematically mis-estimated in the past. Projections of the effects of warming on unicellular respiration change from superlinear to sublinear once the metabolic scaling relationship is updated, with worrying consequences for the biological carbon pump and other ecosystem services. Other size-function scaling relationships (e.g., photosynthesis) are likely to have been similarly mis-estimated. Next, we show that theory on the relationships between size, temperature and demography is more ambivalent than previously recognised, leaving uncertainty as to how warming will alter the dynamics of unicellular populations. Finally, we identify pathways for improving our capacity to predict future changes in unicellular size, and decrease the uncertainty surrounding the consequences of these changes.