Global Change Biology最新文献

Soil carbon dynamics in response to climate change hold critical implications for global carbon cycling and ecosystem resilience. Net primary productivity (NPP), the dominant source of soil carbon inputs, serves dual functions: it mediates climate effects via carbon input fluxes and moderates them by altering the intensity of climate impacts on soil carbon. In this study, we assembled a dataset of soil organic carbon (SOC; hereafter OC) and its fractions—particulate organic carbon (POC) and mineral-associated organic carbon (MAOC)—from 8147 repeated sampling sites across the European region in 2009 and 2018. Using structural equation modeling with joint mediation and moderation analysis across three major land uses, we identified two functionally distinct, context-dependent roles of NPP. NPP acts as a mediator: favorable climate increases belowground inputs and promotes OC accumulation, primarily through the formation and stabilization of MAOC. NPP also acts as a moderator: it amplifies temperature's negative impacts on soil carbon, with POC being most sensitive to warming. The effects of NPP on the relationship between climatic moisture and soil carbon exhibited a nonlinear reversal: under humid conditions, NPP mainly reduced decomposition-driven carbon loss, whereas under drought conditions, it enhanced input-driven carbon accumulation. In contrast, soil moisture consistently showed a stable positive influence, continuously supporting carbon inputs and accumulation. Cross–ecosystem comparisons show that forests rely more strongly on NPP-driven input and regulatory pathways, whereas in cropland the mediating and moderating roles of NPP are comparatively weaker, making soil carbon more directly influenced by climate. Overall, NPP plays a dual role in the climate–soil carbon pathway: as both a source of input enhancement and a marginal amplifier, representing a functional trade-off under climate change scenarios.

Soil invertebrates represent vital components of belowground biodiversity and play pivotal roles in regulating key carbon (C) cycling processes, particularly soil respiration. Despite the recognised effects of invertebrates on soil respiration, previous studies suffer from a major blind spot: a lack of global-scale interpretations of inferred associations describing how these organisms mediate C release. In this study, we integrated 556 datasets spanning 90 publications to systematically assess the global patterns and inferred associations by which soil invertebrates influence soil respiration. The results revealed that soil invertebrates, on average, enhanced soil respiration by 52%. Across climatic zones, the magnitude of this positive effect tended to decline from tropical to temperate regions. When classified by body size, among the large-bodied soil invertebrates, ants and termites increased soil respiration by 60% and 62%, respectively, whereas earthworms stimulated it by 47%. In contrast, small-to-medium-bodied soil invertebrates exerted no significant effect. Across ecosystem types, soil invertebrates stimulated soil respiration more strongly in forest ecosystems, with an increase of 55%, compared to a 44% increase in grassland ecosystems. The pathways through which soil invertebrates influence respiration varied markedly among body-size groups and ecosystem types. Overall, soil invertebrates primarily influenced soil microbial biomass C, fungal biomass and bacterial biomass, as well as soil organic N, soil organic C and soil pH, which in turn were closely associated with soil respiration. These findings underscore the key role of soil invertebrates in influencing soil CO₂ emissions and provide insights essential for improving Earth system models under ongoing climate change.

Microbial carbon and nitrogen use efficiencies (CUE and NUE) are critical regulators of soil carbon and nitrogen cycling, with their temperature sensitivities playing a pivotal role in mediating biogeochemical feedbacks under global warming. However, how the temperature sensitivity (Q₁₀) of CUE and NUE varies at different temperature ranges and whether their thermal responses are coordinated remains poorly understood. Here, we quantified the Q₁₀ of CUE and NUE in 55 soil samples collected from a ~4000 km latitudinal forest transect in eastern China. We further identified key drivers that shaped Q₁₀ variability from climatic, edaphic, and microbial factors. On average, Q₁₀ was 1.22 ± 0.08 for CUE and 1.46 ± 0.13 for NUE. However, both efficiencies exhibited clear temperature-interval dependence: the mean Q₁₀ of CUE declined from 1.47 ± 0.14 at 12°C–20°C to 0.97 ± 0.08 at 20°C–28°C, while the mean Q₁₀ of NUE decreased from 2.00 ± 0.23 to 0.93 ± 0.09. The Q₁₀ values of CUE and NUE were strongly correlated across temperature ranges and positively associated with the Q₁₀ of microbial growth, indicating a coordinated thermal response governed primarily by growth-based processes. At lower incubation temperature interval (12°C–20°C), variation in the Q₁₀ of CUE was primarily explained by soil stoichiometry and microbial community attributes, whereas under warmer conditions (20°C–28°C), climatic and edaphic constraints, particularly precipitation and soil N/P ratio, became dominant. Although microbial community attributes consistently explained most of the variance in the Q₁₀ of NUE, their influence weakened at higher incubation temperatures, paralleling the pattern observed for CUE and indicating a shift from biotic to abiotic control. Overall, these findings highlight that the temperature sensitivities of microbial CUE and NUE are tightly coupled, growth-mediated, and strongly temperature-context dependent, providing novel insights for improving predictions of soil carbon-nitrogen turnover under climate warming.

Coastal margins are critical sites for carbon (C) sequestration, yet the mechanisms stabilizing preaged, allochthonous C (externally-derived biospheric C) in these environments remain poorly understood. Specifically, the interplay between mineral association and microbial processing represents a significant knowledge gap. Here, we investigated C sequestration mechanisms in Chinese mangrove and saltmarsh soils by analyzing topsoils and cores across 36 sites spanning a 20-degree latitudinal transect. We found that saltmarshes, characterized by high mineral accretion and lower relative autochthonous C accumulation, exhibited significantly longer soil organic C (SOC) turnover times than mangroves (topsoils: ~2200 vs. ~500 years, respectively). This difference corresponded to higher proportions of preaged (~50%) and petrogenic (rock-derived; ~20%) SOC in saltmarshes. Linear mixed-effects models (LMM) confirmed that proxies for mineral protection (e.g., Al/Si) and advanced decomposition (lignin oxidation) were robust, positive predictors of turnover time across the latitudinal gradient. Further structural equation modeling (SEM) indicated a depth-dependent shift in drivers. In surface soils, microbial necromass accumulation was a significant predictor of C turnover (coefficient = 0.36). However, at depth (1 m), the degree of lignin degradation emerged as the primary predictor of multi-millennial C persistence (coefficient = 0.45). These results suggest a joint regulation mechanism whereby microbial processing transforms organic matter into stable forms that are subsequently protected by minerals. This mechanism effectively sequesters old, allochthonous C, challenging the paradigm that blue C storage is dominated solely by recent biomass and necessitating a reevaluation of coastal C management frameworks.

Biological nitrogen fixation (BNF) is a vital process for introducing new N into natural ecosystems, and this process has been demonstrated to be suppressed by high N deposition. However, the net ecological effect and underlying mechanisms of BNF under chronic low-level N deposition, characteristic of terrestrial ecosystems, remain highly uncertain. Given that climate warming is a key environmental change factor concurrent with N deposition, it is important to investigate whether climate warming can change BNF activity and alter the effects of N deposition on BNF. To fill these knowledge gaps, we implemented a decade-long-term manipulation experiment in an alpine grassland ecosystem with 5 treatments, that is, experimental warming (W), low-level N deposition (N_L), high-level N deposition (N_H), combination of climate warming and low-level N deposition (WN_L) and the control (CK). BNF rate was measured by ¹⁵N₂ isotope discrimination. We found that N_L significantly stimulated BNF by 112%, contrasting sharply with the complete suppression under N_H. Climate warming alone increased the BNF rate by 123%, while the WN_L amplified this effect, stimulating BNF by 234%. Structural equation modeling revealed that WN_L selectively favored specific diazotrophic groups (Desulfovibrio), whose proliferation directly drove the observed BNF shifts. In this N-limited alpine grassland, low-level chronic N deposition, especially when combined with warming, fundamentally shifts the diazotrophic community structure by driving a process of niche contraction. This selection process functionally enriches specialized diazotrophs, resulting in a dramatic, positive feedback that significantly promotes the overall biological nitrogen input. Our findings highlight the potential for increased N inputs under realistic future climate scenarios and provide a scientific basis for precision N management in alpine grasslands, both on the Qinghai-Tibetan Plateau and worldwide.