Global Change Biology最新文献

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.

Climate change-driven conservation strategies commonly project habitat availability but may not account for local adaptation among populations of the same species, which can influence prediction accuracy. Using the giant panda (Ailuropoda melanoleuca) as a case study, we developed a regional-scale species distribution model (SDM) and 33 population-specific local models to assess niche divergence and climate-induced habitat shifts (current vs. 2080–2100, SSP2-4.5). Comparisons between the two model scales, validated against observed habitat distributions, revealed clear differences in predicted habitat range, area, quality, and fragmentation among local populations. Specifically, regional-scale models predicted lower climate threats for 15 local populations, higher threats for 10, and did not identify suitable habitats for 8 populations, particularly those that were smaller and more isolated. These findings highlight the importance of incorporating population-specific climatic niche differentiation into conservation planning to improve the reliability of climate impact assessments and to guide population-level strategies for biodiversity conservation under future climate change.

Well-aerated upland soils serve as a crucial biological sink for atmospheric methane (CH₄), playing a key role in mitigating climate change. However, current understanding of how this CH₄ sink responds to global climate change remains limited. To address this, we integrated 1092 observational data points to construct a dataset covering multiple global change factors and used meta-analysis to quantify the response mechanisms of the upland CH₄ sink. Results show that warming, reduced precipitation, and elevated carbon dioxide concentrations significantly strengthened the CH₄ sink, while increased precipitation and nitrogen addition weakened it. Interactive effects were also observed: low-level nitrogen deposition acted antagonistically with increased precipitation, but synergistically with warming. We subsequently optimized a CH₄ oxidation model to explore the global distribution patterns and future trends under different climate scenarios. The current global upland soil CH₄ sink is estimated at approximately 37 Tg year⁻¹ and generally shows an increasing temporal trend. Spatially, the sink exhibits heterogeneity: a greater extent of desert areas in the Northern Hemisphere leads to a lower CH₄ sink per unit area compared to the Southern Hemisphere. Future spatiotemporal trends of the soil CH₄ sink will depend on the climate pathway. Under the Shared Socioeconomic Pathway (SSP) 1–2.6 scenario, the CH₄ sink declines over time, whereas under SSP5-8.5, it follows a unimodal trajectory. Variations in the soil CH₄ sink also differ across regions. These changes are primarily associated with atmospheric CH₄ concentrations under different climate pathways, as well as alterations in soil temperature and moisture resulting from various climate change drivers. These findings underscore the importance of the upland CH₄ sink in the global CH₄ cycle and significantly advance our understanding of its response mechanisms to climate change.

Land surface phenology is a key indicator of ecosystem responses to global change, but most studies largely emphasized temporal trends, leaving spatial patterns, particularly those shaped by canopy structure, underresolved. As disturbances from forest dieback, invasive species, and wildfire expand canopy openings that reshape microclimates, their consequences for the timing of spring green-up and fall senescence remain poorly quantified. Leveraging multi-source remote sensing data from 25 sites in the National Ecological Observatory Network (NEON), we evaluated how canopy gaps and their interactions with climate affect phenology across diverse biomes with a Bayesian spatially explicit model. Gaps were associated with earlier spring and later fall phenology in 15 and 18 sites, respectively; tropical seasonal and temperate rainforests showed delays in both seasons, whereas temperate seasonal forests generally advanced spring and delayed fall, and woodland/shrubland advanced spring but exhibited mixed fall responses. At typical average gap sizes (200 to 650 m²), spring green-up shifted by −2 to +2 days and autumn senescence by −1 to +5 days, with climate background modulating both magnitude and direction in some sites. Our models also achieved high out-of-sample accuracy (R² > 0.5 at 21 of 25 sites for spring and 20 of 25 for fall), highlighting canopy structure as a key driver of spatial variations in phenology. Because canopy structure can be modified through silvicultural practices, these findings provide actionable guidance for climate-resilient forest management.