Drought is one of the major abiotic stresses that limits plant growth. Roots, the primary organs responsible for water uptake, are the first to perceive and respond to water deficit conditions. Therefore, maintaining activity and promoting primary root elongation under drought stress are considered critical adaptive strategies for drought survival. However, despite increasing evidence of primary root elongation under drought stress, the underlying mechanisms, particularly hormonal regulation and its integration with environmental cues, remain poorly understood across different species and developmental contexts. Previous studies have shown that a highly coordinated network of plant hormone crosstalk plays a significant role in this adaptive process. In this review, data from diverse plant species confirmed the promoting effect of drought on primary root growth. This study further elucidated the role of abscisic acid (ABA) in enhancing primary root growth under drought conditions and explored the potential coordination of ABA with other hormones, including ethylene, auxin, and cytokinin, to synergistically promote primary root elongation. Furthermore, several physiological processes, such as cell cycle regulation, osmotic adjustment, and lateral root growth dynamics, had been systematically investigated for their contributions to this adaptive response. By dissecting these mechanisms, this study aims to propose feasible strategies to increase plant drought tolerance through targeted root system architecture modification, addressing challenges posed by future climate scenarios.

Ecological data frequently exhibit spatial autocorrelation, whereby geographically proximate sampling units are more similar in species distributions, community composition, or environmental attributes than expected by chance. Spatial Autoregressive models (SARs) address this issue by explicitly incorporating spatial dependence. However, disentangling the relative contributions of spatial structure and ecological predictors remains challenging, particularly in the presence of multicollinearity. The ‘spatialreg.hp’ R package extended the concept of average shared variance (ASV) to SARs, enabling the decomposition of total model R² into unique and shared contributions of spatial and non-spatial predictors. The package calculated individual R² values for spatial effects and environmental variables that summed exactly to the total model R², thereby providing a new measure of predictor importance. We illustrated the package using case studies based on classic spatial datasets. The ‘spatialreg.hp’ package offers ecologists and geographers a new framework for quantifying the interplay between spatial processes and environmental drivers in ecological modeling.

Tree planting is widely recognized as an effective strategy for enhancing terrestrial carbon sequestration, playing a crucial role in mitigating global climate change. However, our understanding of how it may affect soil fauna communities remains scarce. Here, we performed a global meta-analysis with 14 281 paired observations to evaluate tree planting effects on soil fauna abundance, biomass, and diversity across multiple former ecosystem types. Results showed that (i) tree planting had limited overall effects on soil fauna communities, only increasing Acari abundance, Protozoa abundance and Arthropod biomass by 36.9%, 56.9% and 777.3%, respectively, and decreasing the taxonomic richness of Collembola, the Pielou index of earthworm, and the Simpson index of Protozoa by 17.9%, 38.7%, and 77.1%, respectively; (ii) afforestation in non-forest lands showed strong positive effects on soil fauna abundance and diversity, especially in deserts where the abundance and Shannon-Wiener index of total soil fauna were increased by 92.5% and 65.8%, respectively, while reforestation in former forest lands generally had negative impacts; and (iii) tree planting effects on soil fauna were mediated by stand characteristics (e.g. stand age, canopy density, tree diameter) and pre-planting soil properties (e.g. bulk density, pH, carbon, nitrogen), but not by tree species type (leaf type or mycorrhizal association). These results demonstrate the contrasting effects of tree planting on soil fauna communities among different former ecosystem types, highlighting the importance of considering the legacy of former ecosystems when designing tree planting policies to restore/enhance carbon sequestration and biodiversity conservation under global environmental change scenarios.

Extreme climatic events often co-occur with persistent environmental disturbances, such as nitrogen enrichment, which may influence the resistance and recovery of plant communities to extreme climatic conditions. However, most studies have focused on the resistance and recovery of community functions (e.g. biomass) to climatic events while neglecting the corresponding responses of diversity. Here, we performed a soil nitrogen addition experiment in an alpine meadow from 2011 to 2020, with 2015 characterized by extreme drought. We explored the effects of nitrogen addition on the resistance and recovery of plant community biomass and diversity in response to extreme drought using measures including community biomass, taxonomic diversity (TD), phylogenetic diversity (PD) and functional diversity (FD). We found that nitrogen addition decreased biomass resistance, mainly due to species asynchrony rather than the diversity resistance, even though PD and FD resistance also declined. Meanwhile, nitrogen addition enhanced the recovery of biomass to drought. This was mainly attributable to the direct, positive impact of nitrogen on biomass recovery, coupled with an indirect influence of species asynchrony, without any diversity (TD, PD, FD) recovery effects. Our results indicate that soil nitrogen enrichment mainly influences plant biomass responses to extreme drought, with a relatively small effect on plant diversity. Additionally, the mechanisms driving diversity and biomass responses may operate independently, as changes in diversity response did not scale up to changes in biomass. We anticipate that maintenance of plant community biomass during extreme drought would be more challenging in conditions of high nitrogen deposition.

Herbivorous insects shape plant growth and community assembly, while conversely, plant traits, especially leaf traits, profoundly affect herbivore behaviors. However, which leaf traits and how they dominantly drive insect herbivory in a natural forest habitat remain undefined. In this study, we evaluated the background insect herbivory of 45 individual trees from five broadleaved tree species in the northeast of China. Based on that, 17 leaf traits representing four groups—leaf structural traits, photosynthetic pigments, nutrient traits, and secondary metabolites—were measured. Finally, the correlation between 17 leaf traits and background insect herbivory was investigated. The results indicated that the damaged leaf area (DLA) exhibited positive correlations with leaf structural traits (leaf mass per area and leaf size) and nutrient traits (soluble sugar (SS), non-structural carbohydrates (NSC), SS/NSC), and a negative correlation with photosynthetic pigments, nitrogen/phosphorus ratio, and anthocyanins. Meanwhile, SS/NSC, SS, leaf size, total phenol, and phosphorus were identified as the five relatively important leaf traits contributing to DLA by the quantitative estimation based on SHAP (SHapley Additive exPlanations) values. Furthermore, nutrient traits accounted for 52.9% of DLA explanation, showing the most important group of leaf traits. In addition, structural traits and secondary metabolites were found to interactively influence herbivory. These findings provide valuable insights into the complex interactions between host plants and herbivorous insects in forest ecosystems.

Peatlands store approximately one-third of global soil organic carbon (SOC) and clarifying SOC sources is essential to assess soil carbon (C) formation and stability in these C-rich ecosystems. However, large-scale patterns and drivers of plant- and microbial-derived C in peatlands remain poorly understood. This study applied lignin phenols and amino sugars as biomarkers for plant and microbial residues to investigate the regional distributions and controlling factors of plant- and microbial-derived C in surface peat (0–20 cm) across Zoige alpine peatlands. Our results showed that amino sugars contributed less while lignin phenols remained stable with SOC accrual, indicating the key role of plant-derived C in SOC accumulation. Soil nutrients and microbial properties explained the majority of the variation in lignin phenols, while soil nutrients and mineral protection played a more important role in amino sugars than microbial variables and climatic factors. Specifically, lignin phenols were negatively correlated with soil nutrients, fungal richness, and acid phosphatase activity, while showing a positive association with leucine aminopeptidase activity. In contrast, amino sugars were positively related to soil total phosphorus but negatively linked with Fe-associated C and Fe/Al-oxide. These findings provide the first empirical evidence of plant- and microbial-derived C and their divergent drivers in alpine peatlands over broad geographic scale, which advances our understanding of soil C formation and stability in these C-rich, climate-sensitive ecosystems.

Arbuscular mycorrhizal fungi (AMF) can enhance terrestrial plant growth by promoting nutrient uptake. However, the effects of interactions between AMF and nutrient inputs on plant functional traits and their trade-offs remain poorly understood. In this study, a pot experiment was conducted using Phragmites australis as the host species, with AMF inoculation and non-inoculation treatments under three levels of nitrogen addition and two levels of phosphorus addition. The results showed that AMF inoculation significantly increased AMF colonization in the roots of P. australis. Under unfertilized conditions, AMF significantly promoted plant morphological development and biomass accumulation. Nitrogen addition primarily enhanced aboveground growth, while phosphorus addition significantly stimulated root system development. Regarding photosynthetic traits, AMF inoculation significantly increased carotenoid content, whereas phosphorus addition significantly reduced net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) by 18.5%, 25.8%, and 28.2%, respectively. Furthermore, AMF inoculation increased leaf nitrogen and phosphorus contents but reduced stem nitrogen content and the N:P ratios in fine roots, rhizomes, and stems. Trait network analysis revealed that AMF inoculation shifted the central traits from leaf biomass to rhizome biomass, indicating a transition in hub traits from aboveground to belowground organs. These findings suggest that AMF inoculation significantly promotes the growth of P. australis although the magnitude of this benefit is modulated by soil nitrogen and phosphorus availability, with stronger effects observed under nutrient-poor conditions. This study advances our understanding of nutrient–AMF–plant interactions in wetland ecosystems and provides a theoretical foundation for ecological restoration and nutrient management in vulnerable aquatic habitats.

As global warming drives plant upward migration, the alpine tundra of Changbai Mountain is experiencing encroachment by Deyeuxia angustifolia (Komarov) Y. L. Chang, a low-elevation herb. However, its impact on native shrubs such as Rhododendron aureum Georgi remains unclear. Here, we analyzed the radial growth trends and climate sensitivity of R. aureum across elevations and encroachment gradients using linear and mixed-effects model methods, and explored the mediating roles of soil properties and plant traits. Our study revealed that R. aureum exhibited stronger positive long-term growth trend at higher elevations compared to lower elevations. Mild and moderate encroachment of D. angustifolia enhanced the positive growth trend of R. aureum, especially at the low elevations. Moreover, R. aureum showed weak climate sensitivity at mid-elevation but stronger responses to winter temperatures at low elevation and to spring–summer temperatures and precipitation at high elevation. D. angustifolia encroachment further intensified this sensitivity, characterized by stronger negative responses to spring, autumn, and winter temperatures but positive responses to summer temperatures and autumn precipitation. Overall, elevation primarily influenced R. aureum growth and its sensitivity to precipitation through soil conditions and plant size traits. Soil conditions and leaf economic traits influence temperature sensitivity. These findings advance understanding of alpine vegetation dynamics and contribute to ecosystem conservation under climate change.

Despite nitrogen (N) and phosphorus (P) being biologically coupled and controlling many biochemical reactions, few studies have examined the N:P patterns and controls of legumes and non-legumes at a global scale. Herein, we explored how the ratio of N and P in legumes and non-legumes responds to environmental factors, globally. Our results indicated that legumes exhibited stronger N-P coupling (R² = 0.39, P < 0.0001) in warm-humid environments (mean precipitation: 988.94 mm, temperature: 12.63 °C), and the N:P is negatively affected by the soil total P (scored at = −0.25). In contrast, non-legumes were more flexible in N and P (R2 = 0.23, P < 0.0001) in semihumid regions (precipitation = 785.01 mm, temperature = 8.85 °C), where soil total N (scored at = −0.22) and biodiversity (scored at = 0.16) emerge as dominant drivers for the N:P. Although legumes are expected to be more soil P-limited, our findings revealed that the leaf N and P were more coupled in legumes than in non-legumes, which offers a unique perspective on resource utilization and survival strategies in different plant functions.

Drought events and nitrogen deposition are substantially modifying the stability of terrestrial ecosystems. Previous studies have mostly investigated these factors separately, with an emphasis on productivity stability, leaving their combined effects on multiple dimensions of ecosystem stability poorly understood. We conducted a four-year grassland manipulative experiment to examine how three drought scenarios—intense drought, chronic drought, and precipitation frequency reduction—interact with nitrogen addition to influence community compositional stability and productivity stability. The results showed that drought and nitrogen enrichment independently influenced grassland stability without significant interactions. Both intense and chronic drought reduced productivity stability, while reduced precipitation frequency decreased compositional stability. Nitrogen addition decreased both types of stability. Productivity stability was driven by the dominant species’ productivity stability or a combination of it and species asynchrony, depending on the drought scenario. Compositional stability consistently depended on the dominant species’ compositional stability. Compositional and productivity stability remained decoupled across treatments. This study provides the first empirical evidence of the divergent responses of grassland compositional and productivity stability to various drought scenarios under nitrogen enrichment. Our findings highlight the importance of prioritizing dominant species and promoting species coexistence with diverse environmental responses to maintain stable grassland composition and productivity under global change.

CO₂ released into the atmosphere through soil respiration represents the second-largest carbon flux between terrestrial ecosystems and the atmosphere. While extensive research has concentrated on surface soils, limited studies have explored CO₂ emission patterns and their primary drivers across varying soil depths. In this study, soil CO₂ emissions were measured using static chambers at six different depths (10, 50, 100, 200, 300 and 400 cm) in a primary forest. Additionally, potential influencing factors, including soil physical and chemical properties, microbial diversity and community structure and function, were assessed. The results demonstrated that soil nutrients, along with fungal and bacterial diversity, generally declined with increasing soil depth. Soil CO₂ emissions also decreased significantly with depth, driven primarily by biotic factors such as fungal and bacterial alpha diversity and abiotic factors such as ammonium nitrogen and available phosphorus. These findings provide new insights into the mechanisms of carbon cycling within deep soil layers in forest ecosystems.

In water-limited ecosystems, photodegradation is a dominant pathway of carbon (C) turnover. However, the combined effects of spectral composition and litter traits in hyper-arid deserts remain poorly constrained, limiting the accuracy of C flux predictions. In a 637-day field experiment with three representative desert species (Populus euphratica, Alhagi sparsifolia and Karelinia caspia), we applied natural light filters to establish six spectral treatments. Full-spectrum exposure increased litter decomposition by 70%; of the five individual wave-bands, only UV-B (280–315 nm) and blue light (400–500 nm) significantly accelerated mass loss, accounting for 43% and 29% of the full-spectrum effect, respectively. These two wave-bands accelerated C and cellulose loss, whereas green light (500–580 nm) selectively promoted hemicellulose and lignin degradation without affecting total mass. UV-B and blue light also increased specific leaf area (SLA) by 12.9% and 7.0% and elevated litter microbial respiration rate (LMR, 24-h incubation at 25 °C, 60% relative humidity) by 54.6% and 40.6%, respectively. Across four spectral regions, initial C content, lignin:N ratio, SLA and LMR were significantly correlated with photodegradation rate, with LMR and lignin content per unit surface area being the strongest predictors of susceptibility. These results highlight the co-regulation of photodegradation by spectral composition and plant traits, advancing mechanistic understanding of C cycling in hyper-arid ecosystems and providing refined parameters for Earth system models changing solar regimes.

Seagrass meadows conservation and restoration are recognized as nature-based solutions for climate change mitigation. Seed-based restoration strategies have gained popularity owing to their potential for large-scale application. Despite an increasing number of successful seagrass restoration efforts, large-scale seeding restoration practices still face challenges, including low sowing efficiency and seedling emergence rates. To address these challenges, this laboratory study investigated the feasibility of adapting terrestrial seed tape sowing technology for seagrass restoration, specifically by examining the effects of seed tape sowing and various tape materials (polylactic acid, polypropylene, cotton, and paper) on Zostera marina L. seed germination and seedling establishment. The findings demonstrated successful eelgrass seed germination and seedling establishment using seed tape, achieving a maximum seedling establishment rate exceeding 80%. Seed tape materials were found to play a vital role in seed germination and seedling growth, primarily attributable to their structural properties rather than their degradation performance. Environmentally friendly cotton and paper tape materials were identified as more suitable for seagrass restoration compared to less readily degradable materials. These results indicate that seed tape sowing technology holds significant potential for large-scale seagrass restoration, offering benefits such as enhanced sowing efficiency through mechanized equipment and improved seed use efficiency. However, this technology requires further optimization and exploration in field settings. This research provides valuable theoretical insights and empirical data to support the application of seed tape sowing technology in seagrass restoration.

Understanding how interacting environmental drivers alter plant nutrient resorption is essential for elucidating nutrient cycling in grasslands. We conducted a 9-year field experiment in a meadow steppe to examine the effects of nitrogen (N, 10 g N m⁻² yr⁻¹) and zinc (Zn, 0.5 g Zn m⁻² yr⁻¹) additions and mowing on community-level nutrient resorption efficiency (RE). We quantified RE for 10 macro- and micronutrients and explored their links with soil properties, species richness and aboveground productivity. N addition enhanced RE for N (+12.9%), P (+15.4%), S (+159.1%) and Mg (+64.4%), supporting the growth optimization hypothesis. Mowing reduced RE for N (−14.0%) and P (−4.8%) but increased RE for Mg (+26.0%) and Fe (+60.4%), indicating compensatory strategies. Zn addition showed limited effects on macronutrient RE but markedly altered micronutrient dynamics, weakening ZnRE through negative feedback and modifying Fe resorption depending on context: reducing by 113.8% in CK and 61.4% under N addition but enhancing by 24.3% under mowing treatment and 51.3% in treatment of combined mowing and N addition. Aboveground productivity was the strongest predictor of RE, surpassing soil nutrient availability. Our findings reveal that additions of N and Zn and mowing jointly regulate element-specific nutrient resorption and plant functional adjustments, reshaping nutrient cycling and productivity patterns in temperate grasslands.

Human activities are strongly affecting ecosystems worldwide, altering abiotic factors and often triggering massive habitat invasions, as in the case of coastal dunes. Moreover, biotic interactions with native dune species can either facilitate or hinder the invasion process. In order to curb the invasion of alien plants, it is therefore important to understand the interplay between biotic and abiotic factors during the colonization process. Our experiment investigated the cascading effects of soil stress, plant growth, and the functional traits of the key species Cakile maritima, on the alien and native plant community. In an island of the Marano’s lagoon, Northern Adriatic Sea, we mechanically removed the vegetation in the back dune, triggering a new ecological succession. In the site we created a soil stress gradient by altering main soil properties (i.e. salt, nitrogen, and organic matter) with a randomized block design. Soil properties directly affected the plant functional traits of C. maritima and the diversity and composition of the whole community. Moreover, the cover, height, and functional traits of C. maritima showed a direct effect on native and alien species populations, likely competing with other native species, but only when soil conditions ameliorate, leaving free niches for the alien species colonization. These results showed a direct effect of soil on sand dune plant succession and diversity, but this was also indirectly mediated by the key species response. This study provided new information on the mechanisms of the coastal dune biological invasions, suggesting that induced soil stress can be effective to combat alien plant proliferation while maintaining native stress-tolerant species.

It is unclear whether and how tree-ring width is associated with photosynthetic productivity and nutrient recycling in forest ecosystems. Here, we aim to demonstrate how leaf turnover and nitrogen (N) resorption are crucial in regulating the seasonality of carbon (C) availability, and how tree radial growth is controlled by C supply in an alpine treeline forest. The seasonal litterfall, N resorption, leaf N concentration, leaf and twig non-structural carbohydrate (NSC) contents across eight trees were monitored every 2 weeks during the growing season, and radial increments were recorded by automatic dendrometers at Abies georgei var. smithii treeline. Leaf N showed a positive correlation with previous bi-weekly litterfall and N-resorption in the early season before late June, but with soil temperature in the later season. Leaf NSC typically peaked in the early growing season and showed significant relationships with previous bi-weekly litterfall and N-resorption and the following bi-weekly radial increment. There was a lagged chain from previous bi-weekly litterfall and N-resorption to current NSC in leaves, and then from current NSC in leaves to the following bi-weekly radial increment. As a significant C-storage pool, twig NSC reached a maximum in mid-July, and showed no correlation with litterfall, N-resorption and radial growth rate. N resorption and C supply regulated by leaf turnover controls tree radial growth at the alpine treeline. Our results highlight the significant role of nitrogen recycling and leaf source NSC production in driving tree radial growth, as compared to stored NSC.

Stand density management can influence understory natural regeneration and plant diversity during forest rewilding. Changes in plant diversity drive shifts in soil microbial communities and soil organic carbon (SOC) sequestration. However, the response of soil microbes, especially microbial carbon (C) metabolic functions, and SOC fractions to changes in stand density and plant diversity remains poorly understood. This study examined naturally regenerated Chinese fir (Cunninghamia lanceolata) stands after 30 years under three sprout density treatments (1200, 850 and 500 stems ha⁻¹). We investigated variations in plant diversity (tree species, structural and functional), SOC fractions (particulate and mineral-associated organic C), microbial diversity, CO₂ fixation pathways and carbohydrate-active enzymes, as well as the linkage among these variables in the topsoil (0–10 cm) using metagenomic sequencing. Tree species, structural and functional diversities, as well as fungal alpha diversity, increased with decreasing sprout density, whereas bacterial alpha diversity remained unchanged. The abundances of most C fixation pathways and genes involved in labile C degradation increased with decreasing sprout density. Microbial diversity and C fixation/degradation genes were primarily influenced by tree species diversity. The contents of SOC fractions increased with reduced sprout density and exhibited positive correlations with plant and fungal diversities, most C fixation pathways (e.g. Calvin cycle, rTCA cycle, DC/4-HB cycle and 3-HP/4-HB cycle), and labile C (e.g. cellulose and peptidoglycan) degradation genes. These findings highlight that reducing stand density significantly enhances tree species diversity over the long term, which in turn promotes SOC accumulation by influencing microbial C fixation and degradation potential. Our study provides new insights into how tree species diversity mediates microbial regulation of SOC sequestration during forest rewilding.

The spatial pattern and community assembly processes of soil microbial taxa are critical for understanding biodiversity formation and maintenance mechanisms. While rare fungal taxa likely exhibit distinct biogeographic patterns and assembly processes compared to abundant taxa, such differentiations remain poorly characterized, particularly at continental scales. Here, we investigated distance-decay patterns and underlying assembly mechanisms for abundant and rare fungal taxa in 129 soil samples collected across 4000 km in Chinese northern grasslands, based on high-throughput sequencing data. A total of 208 abundant operational taxonomic units (OTUs, relative abundance >0.1%) and 5779 rare OTUs (relative abundance <0.01%) were identified. Both abundant and rare fungal taxa showed significant distance–decay relationships (P < 0.001), but the turnover rate for rare taxa (0.0024 per 100 km) was nearly half that of abundant taxa (0.0054 per 100 km) based on the binary Bray–Curtis distance. The lower turnover of rare fungal taxa was likely due to their community assembly mechanism dominated by stochastic processes, which were less influenced by environmental gradients. In contrast, abundant taxa assembly was dominated by deterministic factors like soil variables and plant traits, which varied significantly along the geographic distance. Consistently, rare fungal taxa were also less sensitive to environmental changes, with a lower turnover rate by environmental distance (0.0027 vs. 0.0099) than abundant taxa. Our findings revealed that rare fungal taxa—shaped mainly by stochastic processes—had lower spatial turnover compared to abundant taxa, which are dominated by deterministic processes. This deepens our understanding of rare microbial biogeography.

Microbial carbon use efficiency (CUE) and nitrogen use efficiency (NUE) are key parameters that determine the fate of carbon (C) and nitrogen (N) in soils. However, the responses of microbial CUE and NUE to N deposition across soil depths remain poorly understood. In this study, we conducted an N-addition experiment in a Castanopsis faberi forest. Soil samples were collected from the topsoil (0–10 cm) and subsoil (20–30 cm) under three N addition levels to investigate depth-specific responses of microbial CUE and NUE. Changes in soil C fractions, microbial biomass, enzyme activities, and microbial community composition were assessed. Results showed a significant positive correlation between CUE and NUE, indicating a closed relationship between microbial C and N metabolism. Nitrogen addition reduced CUE and NUE at both depths, though the negative effects were less pronounced in the subsoil. Nitrogen addition significantly altered soil C fractions: labile C and particulate organic C increased in the topsoil, whereas mineral-associated organic C and recalcitrant C decreased in the subsoil. Microbial CUE and NUE were significantly correlated with the quantity of soil C fractions. Compared to the topsoil, the subsoil had lower CUE, NUE and dissolved organic C content but a higher C/N ratio, suggesting that differences in CUE and NUE between soil depths are regulated by both the quantity and quality of soil C. These findings reveal a depth-dependent yet directionally consistent effect of N addition on microbial resource-use efficiency, offering new insights into C–N coupling processes in forest ecosystems.

Although planting density is known to affect plant–soil interactions, its specific influence on the sources of soil organic carbon (SOC) in forest ecosystems remains unclear. To address this issue, we examined plant- and microbe-derived carbon (C) pools, using soil lignin phenols and amino sugars, across a planting density gradient (570–3000 trees hm⁻²) comprising 28 levels in temperate Robinia pseudoacacia forests. The results demonstrated that both the lignin phenols and microbial necromass C contents decreased significantly with increasing stand density (P < 0.05). Between them, lignin phenols (755.6–2539.3 mg kg⁻¹ SOC) contributed more substantially to SOC accumulation than microbial necromass C (767.5–1742.5 mg kg⁻¹ SOC). In particular, fungal-derived C ranged from 338.0 to 1260.1 mg kg⁻¹ SOC, while bacteria-derived C ranged from 329.8 to 570.3 mg kg⁻¹ SOC. These findings imply that increasing stand density limits the accumulation of SOC by decreasing the lignin phenol and microbial necromass C content. Notably, lignin phenols were primarily influenced by plant composition, while microbial necromass C was mainly determined by microbial properties and soil C content. These results highlight the significance of plant–soil trait interactions in shaping SOC composition and emphasize their relevance for predicting C-climate feedback in forest ecosystems. Overall, our findings provide new insights into the effects of planting density on SOC dynamics, highlighting important implications for sustainable forest management and climate feedback.

Coexisting plants in drylands with different rooting depths can exploit different spatial water sources to maintain productivity. The sequence of water potential thresholds for key physiological events during dehydration strongly influences overall plant function. However, how rooting depth coordinates with this water potential sequence remains poorly understood. Here, we measured leaf structural, hydraulic, and stomatal traits of eight coexisting desert woody species with rooting depths ranging from 69 to 337 cm. Rooting depth was positively related to hydraulic efficiency, turgor loss point, leaf embolism resistance and stomatal closure point, but negatively related to non-structural carbohydrates and water use efficiency. Positive correlations between rooting depth and hydraulic/stomatal safety margins suggested that deep-rooted species had a conservative water potential sequence, i.e. preemptively closing stomata to prevent substantial embolism occurrence. Conversely, shallow-rooted species displayed a risky water potential sequence but adopted compensatory strategies, including low water demand, strong embolism repair capacity and high carbon allocation to sapwood area relative to leaf area. Together, our results suggest that severe water limitation imposes strong selective pressure, resulting in tight coordination among rooting depth, stomatal regulation, water use, embolism resistance and repair and structural construction, which is critical for species coexistence in desert ecosystems.

The United Nations has designated 2021–2030 as the ‘Decade on Ecosystem Restoration’ to combat ecosystem degradation. Climate change and human activities are the primary drivers of this degradation, which has significantly impacted soil multifunctionality (SMF) in China’s drylands. However, the effects of human activities, particularly those related to ecological restoration policies, remain poorly understood. Here, we evaluated the influence of climate change and human activities on five soil functions based on 18 189 observations from 841 studies in China’s drylands and used machine learning methods to forecast future changes. We found that warming and precipitation changes had overall minimal effects on SMF. In contrast, nitrogen deposition improved it by 13.4%, mainly by enhancing soil nutrient supply and productivity. Human activities, particularly ecological restoration, had a greater impact on SMF than climate change. For instance, policies like the Grain for Green Program enhanced the climate regulation function by 32.2%. Further, we found that local climate conditions primarily influenced SMF responses to climate change, while the duration of restoration efforts shaped responses to human activities. Our projections of SMF under the sustainable emission scenario (SSP1-2.6) suggested that well-planned ecological restoration was likely to sustain and enhance SMF over time, particularly in hyper-arid areas. These findings highlight that human activities exert a more significant influence on SMF than climate change in China’s drylands and may provide a scientific basis for sustainable management and ecological restoration of arid ecosystems.

The nitrogen (N) vs. phosphorus (P) scaling exponent, indicating the allocation strategies of the two nutrients, plays an important role in predicting plant and ecosystem functioning. Besides the constant scaling relationship of N vs. P, plasticity of scaling exponents has been demonstrated, with proposed potential causes including plant functional groups (PFGs) or environmental factors. However, relatively little is known about whether the N vs. P scaling exponent of different PFGs response similarly to different environmental conditions. We measured N and P concentrations in leaves and twigs of 964 shrub individuals in a secondary subtropical forest in Eastern China and explored how the N vs. P scaling exponent vary with different light or soil nutrient conditions for deciduous and evergreen shrubs. The leaf N vs. P scaling exponent of evergreen but not deciduous shrubs was affected by light condition, with higher scaling exponent of understory shrubs than that of typical shrubs. The twig scaling exponent of understory shrubs was lower than that of typical shrubs for both PFGs. With increasing soil N availability, responses of scaling exponents in both organs for both PFGs consistent with compliant type first and resistant type later. The scaling exponents of deciduous and evergreen shrubs in both organs showed opposite trends at a relatively high soil P availability level. Our results reveal that environmental factors may alter the N vs. P scaling exponent differently across PFGs. These findings have important implications for improving predictions of stoichiometric models and broadening our understanding of plant responses to varying environments.

Leguminous species have an advantage in acquiring phosphorus (P) compared with non-leguminous species. Nonetheless, it remains unclear whether this advantage would diminish under long-term nitrogen (N) deposition. In the seventh year of a simulated long-term N deposition experiment, we sampled surface soil to measure acid phosphatase activity (ACP) in stands dominated by leguminous and non-leguminous species, respectively. To assess the response of ACP to prolonged N addition, we also collected data on ACP in the second, eighth, twelfth, and thirteenth years of the experiment. We found that the difference in soil ACP between the two plantation types disappeared after long-term N input, and this process was accelerated under high N addition. This occurred due to an exacerbated P-limitation, which primarily prompts ACP production only in non-leguminous species. Additionally, there was a relatively decreased N contribution efficiency to ACP in the stand with leguminous species, indicating that soil N content no longer primarily governs ACP. This study demonstrates that prolonged high N deposition accelerates the loss of the “P-acquiring advantage” in leguminous plantations. To elucidate the differences in P usage strategies between leguminous and non-leguminous species under global change, more systematic research is warranted in the future.

Plants’ compensatory growth is the common response following grazing/mowing, particularly determined by the damage severity, availability of resources and plant functional types. Clonal plants exhibit unique clonal functional traits, yet the compensatory growth strategies underlying their responses to clipping intensity under various nitrogen (N) availability levels remain poorly understood. In this study, a pot experiment was conducted to test how the clonal plant species Leymus chinensis responds to clipping and N enrichment under heterogeneous soil conditions. Moderate clipping significantly enhanced the total biomass of younger ramets by 22% and 12%, under high and low N conditions, respectively, but had no impact on the total biomass of older ramets. The results suggested that L. chinensis exhibited over-compensatory growth characterized by prioritized biomass allocation to younger ramets rather than to older ramets, which facilitated its spatial expansion. However, severe clipping reduced the total biomass of younger ramets by 23%. Furthermore, the older ramets reduced biomass allocation to belowground parts and decreased the rhizome length (−28%), which negatively affected the growth of younger ramets. The younger ramets exhibited adaptation to clipping through the enhancement of antioxidant enzyme activities and the elevation of osmotic regulatory substance concentrations. N enrichment did not influence the total biomass of younger ramets or the entire clone. However, under moderate clipping, the biomass of older ramets increased relative to conditions without N enrichment. Our findings indicate that N availability affected the compensatory growth of the L. chinensis clone induced by clipping, thereby promoting the spatial expansion of this species. These results hold significant potential utilization of clonal plants for the restoration of patchy degraded grasslands.