Search Results (28)

Ecological stoichiometry provides a useful lens for linking nutrient status to ecosystem functioning, but cross-compartment (green leaves, surface litter, and topsoil) evidence for subtropical secondary forests is still limited. In particular, it remains unclear how forest type regulates coupled carbon (C), nitrogen (N), and phosphorus (P) patterns in leaves, litter, and soils on P-retentive Acrisols and how these patterns can be used to infer nutrient limitations. We measured C, N, and P concentrations and stoichiometric ratios in leaves, surface litter, and topsoil (0–10 cm) from 38 plots representing four dominant forest types (shrub, coniferous, mixed coniferous–broadleaf, and broadleaf) in subtropical public welfare forests of eastern China. We compared elemental concentrations and ratios among forest types and compartments and examined cross-compartment associations. Forest-type differences in stoichiometric patterns were most pronounced for leaf and soil concentrations/ratios, whereas litter metrics were comparatively conservative. Coniferous stands had the highest leaf C concentration and the highest litter C:N and C:P ratios, together with relatively low soil N and P concentrations. Broadleaf stands had the highest soil C and N concentrations and the highest litter and soil N:P, suggesting a tendency toward P limitation under comparatively N-rich conditions. Shrub and mixed forests were intermediate, with shrubs exhibiting the lowest litter N:P. Leaf N:P averaged 7.5 in coniferous stands and 12.5–14.9 in mixed and broadleaf stands. Coherent correlations of C:P from leaves to litter and soils and a negative relationship between leaf N:P and soil C:N suggested coordinated stoichiometric linkages along the leaf–litter–soil continuum. Overall, the results show that forest type organizes plot-scale C:N:P coupling on Acrisols and that leaf–litter–soil stoichiometry can be used as a practical framework for identifying whether N- versus P-related constraints are more likely to dominate different subtropical forest types and for informing nutrient-aware restoration and management. Full article

Headwater streams comprise almost 90% of global river networks, and their microorganisms play critical roles in organic matter decomposition and nutrient cycling. These functions, however, are affected by recurrent drying and rewetting. This study examined spatial variation in microbial enzyme activity tied to organic carbon degradation (β-glucosidase, phenol oxidase, and peroxidase) and nitrogen (N-acetylglucosaminidase) and phosphorus (phosphatase) mineralization in water, epilithic biofilm, leaf litter, and sediment in two intermittent streams: Gibson Jack Creek (Idaho, USA) and Pendergrass Creek (Alabama, USA), representing different climactic and physiographic settings. Microbial activity was greater in Gibson Jack Creek, where the activity of leaf litter enzymes varied along the stream network, and there were strong correlations in microbial activity between different stream habitats. Microbial activity in Pendergrass Creek showed primarily within-habitat associations. Activity in water, sediment, and biofilm showed broader spatial heterogeneity in both stream networks. Ratios of microbial activity (enzyme stoichiometry) suggested that microbial communities in both systems were primarily limited by carbon and phosphorus, although there was more spatial variation in nitrogen limitation, particularly in water and sediment at Pendergrass Creek and in biofilm at Gibson Jack Creek. These findings underscore the spatial heterogeneity and environmental sensitivity of microbial processes in intermittent streams. Full article

Climate has shaped green leaf nitrogen (N) and phosphorus (P) patterns through its direct physiological effects (Temperature–Plant Physiology hypothesis), indirect pathways involving soil nutrients (Soil Substrate Age hypothesis), or vegetation composition (Species Composition hypothesis). However, the efficiencies of these hypotheses and the relative importance of the factors involved in predicting leaf litter N and P remain unresolved. We evaluated these hypotheses by analyzing 4657 global observations of leaf litter N and P concentrations and N/P ratios, demonstrating that litter stoichiometries diverged in plant functional types, and that litter N and N/P ratios declined with latitude, while P increased. The validity of each hypothesis in predicting latitudinal patterns of leaf litter P was confirmed, with the Species Composition hypothesis being the most effective model; however, all hypotheses failed to predict the litter N. Environmental and biological factors collectively explained over 40% of the variations in litter stoichiometries, with plant functional type, soil pH, and climatic factors being the most important drivers of litter N, P, and N/P ratio, respectively. The fundamentally different control mechanisms of litter stoichiometry patterns compared with those of green leaves challenge the idea that common hypotheses can predict biogeographic patterns across all leaf stages; thus, current litter element biogeochemical models and plant nutrition paradigms require revision. Full article

Litter nutrient stoichiometry and its drivers are important for understanding nutrient cycling in desert ecosystems, plant adaptation strategies, and the sustainability of ecosystem functions. However, little is known about the spatial variation in litter nutrient stoichiometry and its environmental drivers in desert shrubs. This study focused on two Nitraria species (N. tangutorum Bobrov and N. sphaerocarpa Maxim) in Northwestern China, analyzing leaf litter N, P, and K stoichiometry, their spatial variation, and environmental drivers. Nutrient concentrations and stoichiometric ratios did not differ significantly between the two species. The average N contents in the litters of N. tangutorum and N. sphaerocarpa were 11.363 mg g⁻¹ and 11.295 mg g⁻¹, respectively. The P contents were 0.591 mg g⁻¹ and 0.611 mg g⁻¹, whereas the K contents were 17.482 mg g⁻¹ and 16.255 mg g⁻¹, respectively. With the changes in geographic and climatic factors, the same nutrient elements of the two Nitraria species showed inconsistent variation patterns. Both species showed low P concentration, indicating high P resorption and possible P limitation, reflecting nutrient vulnerability in desert ecosystems according to the scaling exponents among elements. In litter, the residual nutrient contents ranked as K > P > N, suggesting strong N resorption but low K resorption, especially for N. sphaerocarpa. N was mainly influenced by latitude, P by soil properties, and K by mean annual temperature. Moreover, litter stoichiometric ratios of N. tangutorum were relatively stable, whereas those of N. sphaerocarpa were more sensitive to environmental variables. In conclusion, the two Nitraria shrubs exhibited differential nutrient use strategies under nutrient restriction, providing insights into nutrient cycling and supporting sustainable management of desert ecosystems. Full article

Karst rivers are increasingly contaminated by both heavy metals and nanoplastics, yet their combined impact on riparian litter decomposition remains unresolved. We conducted a 90-day microcosm experiment using Miscanthus floridulus leaf litter collected from the Donghe River, Jishou, China, and exposed it to Pb (1 mg L⁻¹), polystyrene nanoplastics (10 and 100 µg L⁻¹), and their combinations. Pb alone modestly inhibited mass loss (61.0%) and respiration, while NP10 significantly accelerated decomposition (67.0%), and NP100 suppressed it (60.4%); co-exposure produced non-monotonic, concentration-dependent effects. Enzyme stoichiometry revealed that all treatments intensified nitrogen limitation but alleviated carbon limitation through reduced microbial activity. Bacterial communities, dominated by Pseudomonadota, exhibited remarkably stable phylum-level composition, high network complexity, and identical keystone taxa across all treatments, indicating strong functional redundancy and resilience. In contrast, fungal communities suffered severe declines in Basidiomycota abundance, collapsed network stability, and a single keystone taxon, underscoring their vulnerability. βNTI–RC_bray analyses demonstrated that stochastic processes (>50%) overwhelmingly governed both bacterial and fungal assembly, with only marginal deterministic shifts. Collectively, our findings highlight that bacteria—not fungi—serve as the primary decomposers under Pb–NP co-stress and that stochastic assembly, coupled with bacterial redundancy, buffers ecosystem function against emerging mixed pollutants in subtropical riverine systems. Full article

The transformation of degraded stands represents an essential strategy for enhancing stand productivity and optimizing site adaptability. This study examined four typical monoculture forest stands transformed from underperforming Platycladus orientalis (PO) forests in the limestone area of Xuzhou, China: Acer pictum subsp. mono (AP), Pistacia chinensis (PC), Ligustrum lucidum (LL), and Firmiana simplex (FS). The contents of carbon (C), nitrogen (N), and phosphorus (P), along with the C:N:P stoichiometric ratios, were analyzed in plants (leaves and fine roots), litter, and soil. The relationships among these components and their main influencing factors were explored. The results indicated that FS leaves contained higher levels of N and P, whereas LL litter presented significantly elevated C:N and N:P ratios in comparison with those of the other forest stands (p < 0.05). With the exception of FS, leaves displayed lower P than fine roots, which presented pronounced P enrichment. The soil C, N, and P contents decreased with depth, with both the forest stand and depth significantly impacting the soil stoichiometry (p < 0.01). Redundancy analysis identified available potassium, total nitrogen, and microbial biomass carbon in the soil as key factors influencing the stoichiometric characteristics of the leaf–fine root–litter continuum. Collectively, the leaf N:P ratios (>16) and low soil P contents indicate that plantation growth was primarily constrained by P limitation. In response, AP, PC, and LL allocate more P to fine roots to adapt to the environment. Full article

This study examines the role of endophytic microbial colonization on the decomposition of oak leaf litter, a high-quality substrate in forest ecosystems. Over a one-year incubation, we observed a significant reduction in mass loss in colonized litter (46%) compared to non-colonized litter (80%), indicating an inhibitory effect of endophytes on decomposition. Structural equation modeling revealed a bimodal impact of endophytic microbes, with an initial enhancement followed by a pronounced inhibition as decomposition progressed. Extracellular enzyme stoichiometry showed phosphorus limitation became significant, particularly with endophytic colonization, contributing to reduced decomposition rates. Microbial diversity analyses exposed the variable impacts of endophytic colonization on fungal and bacterial communities, with taxa such as Helotiales (order) and Burkholderia–Caballeronia–Paraburkholderia (genus) significantly affected. The identification of 16 keystone species, mostly endophytic bacteria, underscored their pivotal influence on decomposition processes. Despite initial endophytic impacts, abundant carbon resources promoted stochastic colonization, potentially surpassing the effects of early endophytic establishment. This study provides insights into the priority effects of endophytic colonization and niche differentiation, offering a foundation for further research into the mechanisms underlying these processes and their ecological consequences in various ecosystems. Full article

The ecological stoichiometric characterization of plant and soil elements is essential for understanding the biogeochemical cycles of ecosystems. Based on three forest ages of Pinus taiwanensis Hayata (P. taiwanensis) plantations in the Gujingyuan National Nature Reserve (i.e., young (16 years), middle-aged (32 years), and mature forests (50 years)), we conducted a field experiment to analyzed C, N, and P stoichiometry and the relationships between needles, litter, soil, and micro-organisms in P. taiwanensis plantations. We intended to elucidate the nutritional characteristics and stability mechanisms of the artificial P. taiwanensis forest ecosystem. The results showed that the C contents of live needles, leaf litter, soil, and micro-organisms in P. taiwanensis plantation forests of the three forest ages were 504.17–547.05, 527.25–548.84, 23.40–35.85, and 0.33–0.54 g/kg, respectively; the respective N contents were 11.02–13.35, 10.71–11.76, 1.42–2.56, and 0.08–0.12 g/kg; and the respective P contents were 0.82–0.91, 0.60–0.74, 0.19–0.36, and 0.03–0.06 g/kg. Forest age significantly influenced both the C, N, and P contents in live needles, leaf litter, soil, and micro-organisms as well as stoichiometric characteristics (p < 0.05). Furthermore, although the litter N:P content was comparable to that of needles, the ratios of C:N and C:P in the litter were notably higher compared to those in needles. Soil C:P and N:P ratios were the highest in mature forests while microbial C:P and N:P ratios continuously decreased. Stoichiometric analyses of our findings suggest that forest stand age can influence divergent changes in element cycling among plants, soil, and micro-organisms. The presented results can aid in further understanding nutrient utilization strategies and regulatory mechanisms for P. taiwanensis plantation forest systems. Full article

Tropical trees that remain evergreen and exhibit leaf litterfall that is gradual over time coexist with trees that are seasonally deciduous and exhibit pulsed litterfall. The manner in which these trees acquire, store, and contribute nutrients to the biogeochemical cycle may differ. Green and senesced leaves from deciduous Ficus prolixa trees were compared with those from Ficus tinctoria on the island of Guam. The results enabled stoichiometry and resorption calculations. F. prolixa’s young green leaf nitrogen (N) and potassium (K) concentrations were double, and the phosphorus (P) concentration was triple, those of F. tinctoria. Concentrations converged as the leaves aged such that no differences in concentration occurred for senesced leaves, indicating that nutrient resorption proficiency did not differ between the two species. In contrast, the resorption efficiency was greater for F. prolixa than F. tinctoria for all three nutrients. The N:P values of 6–11 and K:P values of 5–7 were greater for young F. tinctoria leaves than young F. prolixa leaves. The N:K values were 1.1–1.6 and did not differ between the two species. No differences in pairwise stoichiometry occurred for senesced leaves for any of the nutrients. These Guam results conformed to global trends indicating that seasonally deciduous plants are more acquisitive and exhibit greater nutrient resorption efficiency. The differences in how these two native trees influence the community food web and nutrient cycling lies mostly in the volume and synchronicity of pulsed F. prolixa litter inputs, and not in differences in litter quality. These novel findings inform strategic foresight about sustaining ecosystem health in Guam’s heavily threatened forests. Full article

Assessing the functional traits and ecological stoichiometric characteristics of dominant species across different life forms within plant communities in karst environments and investigating the inherent connection between them can provide insights into how species adjust their functional attributes in response to habitat heterogeneity. This approach offers a more comprehensive understanding of ecosystem processes and functions in contrast to examination of the taxonomic diversity of species. This study examines the relationship between the functional characteristics of dominant species in plant communities of various life forms in karst environments, focusing on deciduous leaf–soil ecological stoichiometry. The investigation relies on community science surveys, as well as the determination and calculation of plant functional traits and ecological stoichiometries, in plant communities of various life forms in Guizhou (a province of China). The findings of our study revealed considerable variability in the functional trait characteristics of dominant species across different plant-community life forms. Specifically, strong positive correlations were observed among plant height (PLH), leaf area (LA), leaf dry matter content (LDMC), and specific leaf area (SLA) in the dominant species. Additionally, our results indicated no significant differences in leaf ecological stoichiometry among different life forms. However, we did observe significant differences and strong positive correlations between soil N:P, withered material C:N, and apomictic C:P. Furthermore, our study found that plant height (PLH), leaf area (LA), and specific leaf area (SLA) were particularly sensitive to the ecological stoichiometry of soil and apomixis. The results of our study suggest that the functional traits of diverse plant-community life forms in karst regions are capable of adapting to environmental changes through various expressions and survival strategies. The development of various plant-community life forms in karst areas is particularly vulnerable to phosphorus limitation, and the potential for litter decomposition and soil nutrient mineralization is comparatively weaker. The functional traits of various plant-community life forms in karst regions exhibit greater sensitivity to both the soil’s C:N ratio and the C:N ratio of apomictic material. Habitat variations may influence the ecological stoichiometric characteristics of the plant leaf–apomictic soil continuum. Full article

Ecological stoichiometry is essential for investigating biogeochemical cycling in an ecosystem. Thinning, a management practice that closely mimics natural processes, significantly influences stand structure and microclimate, thereby affecting nutrient cycling. Nonetheless, seasonal variations in ecological stoichiometry across the leaf-litter-soil continuum under different thinning regimes remain inadequately understood. In this study, we evaluated three thinning methods (strip filling (SF), ecological thinning (ET), and forest gap (FG)) to investigate the stoichiometric characteristics of Cupressus funebris Endl (C. funebris). within the leaf-litter-soil system in Southwest China. The samples were collected during four distinct seasonal periods: early dry season (January–March, EDS), late dry season (April–June, LDS), early wet season (July–September, EWS), and late wet season (October–December, LWS). The results indicated that the (1) carbon (C), nitrogen (N), and phosphorus (P) contents and C:N:P ratio in leaves, litter, and soils varied widely and were strongly influenced by thinning method and season. (2) In the EDS, the soil TP content significantly decreased by 36.9% (p < 0.05), 41.67% (p < 0.05), and 17.9% (p < 0.05) under ET, FG, and SF treatments compared to the pure C. funebris forest (PC). (3) Compared to the PC, the leaf organic C content under ET significantly increased by 6.6% (EDS, p < 0.05), 8.4% (EWS, p < 0.05), 24.8% (LDS, p < 0.05), and 11.5% (EWS, p < 0.05). (4) Under identical thinning methods, the contents of litter C, litter N, litter P, leaf N, and leaf P (excluding litter C in SF) were found to be highest in the LWS. Conversely, the ratios of litter C:N, litter C:P, litter N:P, leaf C:N, leaf C:P, leaf N:P, soil N:P, and soil C:P (except for the ratios of litter N:P in ET and FG) were observed to be lowest in the LWS. (5) Season and thinning method significantly affected the internal stability of P stoichiometric homeostasis, and litter P under ET (EWS) was categorized as “plastic” (p < 0.1, 0.75 < H). (6) The results of the structural equation model show that the thinning method has a direct positive impact on leaf C, N, and P contents and a direct negative impact on the chemical stoichiometry of leaves and soil. Season has a direct positive impact on soil C, N, and P contents, as well as on the chemical stoichiometry of litter and leaves; however, they have a direct negative impact on leaf C, N, and P contents. This study contributes to C. funebris plantation management and provides basic information for global stoichiometric analysis. Full article

Ecological stoichiometry is crucial in understanding nutrient dynamics and its impact on plant growth and development at various ecological scales. Among the different nutrients, nitrogen (N) and phosphorus (P) have been widely recognized as key elements regulating substance transport, energy utilization, and ecosystem conversion. The N:P ratio in plants serves as a sensitive indicator of ecological processes, reflecting the availability and balance of these nutrients. Therefore, studying the ecological stoichiometry of N and P is essential for accurately assessing soil fertility and site productivity, particularly in forest ecosystems with low-fertility soils. In this study conducted in Huitong, Hunan province, southern China, the contents of N and P, as well as the N:P ratios, were investigated in plant-soil systems across four different aged stands of Chinese fir forests (3-, 8-, 18-, and 26-year-old stands). The results revealed varying concentrations of N and P in soils and foliage across the different plantations. Soil N concentrations increased by approximately 4%, 30%, and 22% in 8-, 18-, and 26-year-old plantations compared to the 3-year-old plantation. Soil P concentration was significantly higher in 8-, 18-, and 26-year-old plantations compared to the 3-year-old plantation. The average soil N:P ratio followed the order of 3-year-old plantation > 18-year-old plantation > 26-year-old plantation > 8-year-old plantation. Regarding foliage, both N and P contents exhibited a similar pattern across the different aged leaves, with current-year-old leaves having higher concentrations than 1-year-old, 2-year-old, and 3-year-old leaves in all four Chinese fir plantations. The study further established relationships between soil and foliage nutrient ratios. Soil N:P ratio was positively correlated with soil N content but negatively associated with soil P content. The foliage N:P ratio also showed a significant negative correlation between leaf N and foliage P content. These findings suggest that soil nutrient conditions improved with the aging of Chinese fir plantations, mainly due to increased inputs of above- and below-ground litter. Overall, this study provides valuable insights into the ecological stoichiometry of N and P in Chinese fir plantations, offering a scientific basis for sustainable forest management practices in southern China. Full article

The ecological impact of nitrogen (N) deposition has gained significance since the advent of the industrial revolution. Although numerous studies have examined the impact of N deposition on soil organic carbon (SOC), certain arid and barren rocky mountainous regions, which experience more pronounced N limitations, have been overlooked. This study was conducted in the Yimeng Mountains, examining eight treatments created by four N addition levels (0 kg N ha⁻¹ yr⁻¹, 50 kg N ha⁻¹ yr⁻¹, 100 kg N ha⁻¹ yr⁻¹ and 200 kg N ha⁻¹ yr⁻¹) and two tree species (Quercus acutissima Carruth. and Pinus thunbergii Parl.). The research revealed variations in the effect of N addition on leaf litter decomposition and SOC density (SOCD) between different tree species. Notably, N addition stimulated the decomposition of leaf litter from Quercus acutissima Carruth. However, the decomposition of Pinus thunbergii Parl. leaf litter was enhanced at N addition levels below 100 kg N ha⁻¹ yr⁻¹, while it was hindered at levels exceeding 100 kg N ha⁻¹ yr⁻¹. In the Quercus acutissima Carruth. forest, the N addition levels of 50 kg N ha⁻¹ yr⁻¹, 100 kg N ha⁻¹ yr⁻¹ and 200 kg N ha⁻¹ yr⁻¹ resulted in decreases in SOCD by 10.57%, 22.22% and 13.66%, respectively, compared to 0 kg N ha⁻¹ yr⁻¹. In the Pinus thunbergii Parl. forest, the N addition levels of 50 kg N ha⁻¹ yr⁻¹, 100 kg N hm⁻² ha⁻¹ and 200 kg N ha⁻¹ yr⁻¹ led to increases in SOCD by 49.53%, 43.36% and 60.87%, respectively, compared to 0 kg N ha⁻¹ yr⁻¹. Overall, N addition decreases the SOCD of Quercus acutissima Carruth., but it increases the SOCD of Pinus thunbergii Parl., attributed to the alteration in soil enzyme stoichiometry and nutrient cycling by N addition. This study fills a theoretical gap concerning leaf litter decomposition and SOC sequestration in arid and barren rocky mountainous regions under global climate change. Full article

Ecological stoichiometry plays important roles in understanding the nutrient constraints on tree growth and development, as well in maintaining ecosystem services in forests, yet the characteristics of carbon:nitrogen:phosphorous (C:N:P) stoichiometry in forests under karst environment have not been sufficiently evaluated. In this study, concentration, distribution, stocks of Nitrogen (N) and Phosphorous (P), and ecological stoichiometry were studied in three common forest types: Masson pine natural forests (MPNF), Masson pine plantation forests (MPPF), and Slash pine plantation forests (SPPF) in a karst region of southwestern China. Results showed that N concentrations were higher in overstory than in understory and litter in the studied forests. However, P concentration was relatively low in overstory component of the forested ecosystems. Meanwhile, the N and P concentrations were higher in SPPF in the stem and litter, while these contents were higher in MPPF and MPNP in the overstory and understory. The N and P stocks ranged from 5.7–6.2 t ha⁻¹, and 0.5–0.6 t ha⁻¹ in the examined forests. The ecological stoichiometry of C:N:P in the three forest types was similar in litter (46–49:2:1), and relatively steady in soil (250–320:13–16:1) and tree leaf (100–200:14–20:1). Soil P status was the primary limiting factor in affecting tree growth in MPPF and SPPF (N:P ratio > 16), while both N and P conditions were the main restrictive factors in MPNP (N:P ratio = 15) in the study area. Our study provides scientific references and useful datasets of C:N:P stoichiometry for sustainable management of forest ecosystems in karst regions. Full article

Chinese fir (Cunninghamia lanceolata) is a kind of evergreen coniferous tree species, the expansion of its pure forest area and multiple generations of continuous planting has led to a decline of stand quality and woodland fertility. To further investigate the relationship between leaf, litter, and soil stoichiometry, microbial community status, and microbial resource limitation of Chinese fir after continuous planting. We studied the C, N, and P stoichiometries of leaf, litter, and soil from successive rotations of Chinese fir plantations. In addition to this, soil microbial biomass C, N, and P, extracellular enzymes, as well as the soil microbial community composition, were determined. The continuous planting of Chinese fir significantly increased the leaf N and P contents and decreased the C content of litter, and the soil C:N and C:P ratios, thus leading to a soil stoichiometric imbalance. The continuous planting of Chinese fir plantations significantly increased the soil microbial biomass. Compared with the first-generation plantations, the N and P contents of the second- and third-generation plantations increased by 37.11%, 21.83% and 46.28%, 73.38%, respectively, thus alleviating the restriction of microbial N and P. Under continuous planting, the extracellular enzyme activities of N (NAG + LAP) and P (AP) were significantly decreased, and those of the second- and third-generation plantations were significantly decreased by 7.05%, 9.43% and 11.79%, 48.94%, respectively, compared with those of the first-generation plantations, resulting in an increase of 7.85 and 3.19% in carbon-use efficiency. The fungi:bacteria (F:B) ratio of the soil microbial community was elevated in successive plantations. The least squares pathway model (PLS-PM) indicated that the stoichiometric ratio of ecological enzymes had an indirect negative effect on CUE, and was the strongest predictor. This study showed that the successive plantation of Chinese fir resulted in a leaf, litter, and soil stoichiometric imbalance, further affecting community composition and resource limitation of soil microorganisms. Full article