Search Results (79)

The ongoing global climate change has led to an increase in the frequency and complexity of drought events. Pinus yunnanensis, a native tree species in southwest China that possesses significant ecological and economic value, exhibits a high sensitivity to drought stress, particularly in its seedlings. This study investigates the response mechanisms of non-structural carbohydrates (NSCs, defined as the sum of soluble sugars and starch) and the stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) to repeated drought conditions in Pinus yunnanensis seedlings. We established three treatment groups in a potting water control experiment involving 2-year-old Pinus yunnanensis seedlings: normal water supply (CK), a single drought (D1), and three drought–rewatering cycles (D3). The findings indicated that the frequency of drought occurrences, organ responses, and their interactions significantly influenced the non-structural carbohydrate (NSC) content and its fractions, as well as the C/N/P content and its stoichiometric ratios. Under D3 treatment, stem NSC content increased by 24.97% and 29.08% compared to CK and D1 groups (p < 0.05), respectively, while root NSC content increased by 41.35% and 49.46% versus CK and D1 (p < 0.05). The pronounced accumulation of soluble sugars and starch in stems and roots under D3 suggests a potential stress memory effect. Additionally, NSC content in the stems increased significantly by 77.88%, while the roots enhanced their resource acquisition by dynamically regulating the C/P ratio, which increased by 23.26% (p < 0.05). Needle leaf C content decreased (18.77%) but P uptake increased (8%) to maintain basal metabolism (p < 0.05). Seedling growth was N-limited (needle N/P < 14) and the degree of N limitation was exacerbated by repeated droughts. Phenotypic plasticity indices and principal component analysis revealed that needle nitrogen and phosphorus, soluble sugars in needles, stem C/N ratio (0.61), root C/N ratio (0.53), and stem C/P ratio were crucial for drought adaptation. This study elucidates the physiological mechanisms underlying the resilience of Pinus yunnanensis seedlings to recurrent droughts, as evidenced by their organ-specific strategies for allocating carbon, nitrogen, and phosphorus, alongside the dynamic regulation of nitrogen storage compounds (NSCs). These findings provide a robust theoretical foundation for implementing drought-resistant afforestation and ecological restoration initiatives targeting Pinus yunnanensis in southwestern China. Full article

The purpose of this study was to evaluate the effects of different nitrogen (N), phosphorus (P), and potassium (K) fertilization ratios on the carbon (C), N, and P contents and their ecological stoichiometric characteristics in the leaf–soil–microbial system of Sapindus saponaria and elucidate their relationship with yield. A “3414” experimental design was employed in a 6-year-old Sapindus saponaria woodland located in Fujian Province of China. Fourteen N–P–K fertilization treatments with three replicates were established. Leaf, soil, and microbial samples were collected and analyzed for C, N, and P contents. Redundancy Analysis (RDA), Partial Least Squares Path Modeling (PLS–PM), and the entropy-weighted technique of ranking preferences by similarity to optimal solutions (TOPSIS) were utilized to assess the relationships among variables and determine optimal fertilization strategies. It was found through research that different fertilization treatment methods have a significant impact on both the soil nutrient content and the C, N, and P contents of soil microorganisms. Compared with the control group, soil organic C, total N, and total P, and microbial C, N, and P contents increased by 14.25% to 52.61%, 3.90% to 39.84%, 9.52% to 150%, 6.65% to 47.45%, 11.84% to 46.50%, and 14.91% to 201.98%, respectively. Results from Redundancy Analysis (RDA) indicated that soil organic C, total N, and total P exerted a significant influence on the leaf nutrients. PLS-PM demonstrated that fertilization indirectly affected leaf nutrient accumulation and yield by altering soil properties, with soil total phosphorus and leaf phosphorus being key determinants of yield. Additionally, soil microbial entropy impacted yield by regulating microbial biomass stoichiometric ratios. The entropy-weighted TOPSIS model identified the N₂P₂K₂ treatment (600 kg/ha N, 500 kg/ha P, and 400 kg/ha K) as the most effective fertilization strategy. Optimizing N–P–K fertilization ratios significantly enhances leaf nutrient content and soil microbial biomass C, N, and P, thereby increasing Sapindus saponaria yield. This research clarifies the underlying mechanisms through which fertilization exerts an impact on the C–N–P stoichiometry within the leaf–soil–microbial system. Moreover, it furnishes a scientific foundation for the optimization of fertilization management strategies in Sapindus saponaria plantations. Full article

Mongolian pine (Pinus sylvestris var. Mongolia) has been widely utilized as a key species for afforestation projects within the Three-North Shelterbelt of Liaoning Province in China. Its impressive ecological resilience has made it a favorite choice for this endeavor. However, as the stands mature and climate conditions shift, some areas are experiencing premature decline or even mortality. Ecological stoichiometry is capable of uncovering the supply and equilibrium of plant and soil nutrients within ecosystems and is extensively utilized in the identification of limiting elements. Therefore, studying its ecological stoichiometry and internal stability dynamics is of crucial significance for clarifying the nutrient cycling process in the Mongolian pine region and alleviating the decline situation. The eastern and northwestern regions of Liaoning differ significantly in precipitation and soil nutrient availability. This study examines Mongolian pine plantations in both regions, analyzing the carbon (C), nitrogen (N), and phosphorus (P) content in plant tissues, soil, microbial biomass, and stoichiometric ratio under distinct environmental conditions. In order to provide a theoretical basis for alleviating the decline of artificial poplar forests and healthy management. Results indicate that (1) leaf C, N, and P contents in the eastern Liaoning region averaged 496.67, 15.19, and 1.66 g·kg⁻¹, respectively, whereas those in northwestern Liaoning were 514.16, 14.82, and 1.23 g·kg⁻¹, respectively. Soil C, N, and P concentrations exhibited notable regional differences, with eastern Liaoning recording 34.54, 2.62, and 0.48 g·kg⁻¹, compared to significantly lower values in northwestern Liaoning (7.74, 0.77, and 0.21 g·kg⁻¹). Similarly, microbial biomass C, N, and P were higher in eastern Liaoning (18.63, 5.09, and 7.72 mg·kg⁻¹) than in northwestern Liaoning (10.18, 3.46, and 4.38 mg·kg⁻¹). (2) The stoichiometric ratio of soil in the Mongolian pine plantations is higher than that in northwestern Liaoning, but the stoichiometric ratio of plants shows the opposite trend. Specifically, microbial carbon-to-nitrogen (MBC/MBN) ratios are higher in eastern Liaoning, whereas microbial carbon-to-phosphorus (MBC/MBP) and nitrogen-to-phosphorus (MBN/MBP) ratios are greater in northwestern Liaoning. Correlation analysis of plant–soil–microbe stoichiometry indicates that plant growth in both regions is co-limited by nitrogen, with Mongolian pine exhibiting strong internal stability. Full article

Clarifying carbon (C), nitrogen (N), and phosphorus (P) ecological stoichiometry helps us to understand the ecological functions of wetland ecosystems. This study investigated the variations in ecological stoichiometry and their driving factors in the Yellow River wetland. Soil and plant samples were collected and analyzed from riparian lower-beach wetland (LBW), riparian higher-beach wetland (HBW), and depressional wetland (DW) at the junction of the middle and lower reaches of the Yellow River, respectively. Compared with HBW, DW exhibited higher soil C/N (9.15 ± 0.13), C/P (11.17 ± 0.52), and N/P (1.08 ± 0.09) (p < 0.01), indicating its stronger C and N storage capacity. At the community level, higher plant C/N and C/P in LBW (21.47 ± 1.61 and 206.80 ± 1.75, respectively) and HBW (22.91 ± 0.90 and 241.04 ± 3.28, respectively) compared to DW (14.44 ± 1.02 and 115.66 ± 2.82, respectively) (p < 0.01) suggested that plants in LBW and HBW had greater C assimilation and nutrient use efficiency. Soil electrical conductivity (EC) and hydrolyzed N (SHN) positively affected soil ecological stoichiometry (p < 0.01). In contrast, soil EC, soil organic C, dissolved organic C, and SHN negatively altered plant stoichiometric ratios (p < 0.05), which were regulated by plant functional groups. When pooling all wetlands, stoichiometric ratios of plants were closely correlated with those of soil (p < 0.05). These findings demonstrate that wetland types notably affect soil and plant stoichiometry. Wetland types exerted opposite effects on soil and plant stoichiometry due to the different influences of soil physicochemical properties and the coupling effects of nutrient and stoichiometry between soil and plants. Therefore, the interactions between plant and soil stoichiometry should be considered to explore the C and nutrient cycles in riverine wetlands. Our research emphasizes the necessity of considering wetland type differences and intricate plant–soil stoichiometric interactions in formulating management strategies and maintaining the sustainability of wetlands. Full article

Soil carbon (C), nitrogen (N), and phosphorus (P) cycling and microbial metabolism limitations are key factors affecting nutrient cycling and vegetation development. Extracellular enzyme activity (EEA) plays a key role in carbon and nutrient cycling in ecosystems, and their activities can serve as indicators of microbial nutrient requirements. At present, there is insufficient research on the nutrient limitations of microorganisms during ecosystem transition in abandoned jujube forests on the Loess Plateau. Four modes were selected: jujube forest replanted with Pinus tabulaeformis (CP), with Platycladus orientalis (PO), with medicinal materials (MM), and with alfalfa (AL). An abandoned jujube forest (CK) was used as a control. Soil physical and chemical properties, microbial biomass carbon, nitrogen, and phosphorus, as well as changes in the activities of β-1,4-glucosidase (BG), leucine aminopeptidase (LAP), N-acetylglucosamine (NAG), and alkaline phosphatase (AP), were studied. Analysis of changes in soil microbial nutrient limitations was performed. Compared with those in the CK treatment, the activities of soil C, N, and P extracellular enzymes significantly increased (p < 0.05) in the forest transition treatments, and the C:N_EEA, C:P_EEA, and N:P_EEA ratios of extracellular enzymes tended to decrease. Within the treatments, the activities of soil C, N, and P extracellular enzymes decreased as the soil layer deepened, whereas the enzyme stoichiometric ratio increased as the soil layer deepened, with significant differences observed between the soil layers. The vector model was used to quantify nutrient limitations in microbial metabolism and revealed that microbial metabolism in surface soil was limited mainly by C and P and that in the 10–20 cm and 20–40 cm layers, soil microbial metabolism was limited mainly by C and N. Correlation analysis revealed that SOC, pH, MBC, and MBN were the main factors affecting soil extracellular enzyme activity. Mantel’s test revealed that (NAG + LAP), AP, C:N_EEA, and C:P_EEA were important factors affecting vector length and angle. RAD analysis revealed that microbial properties had a greater impact on enzyme stoichiometry and microbial metabolic limitations than physicochemical indicators did. This study highlights the importance of vegetation in determining microbial metabolic processes and enhances our understanding of how ecological changes in jujube forests affect soil nutrient cycling and microbial metabolic constraints on the Loess Plateau. Forest transformation modes have important impacts on soil extracellular enzyme activity and microbial nutrient limitation. Full article

This study investigates the seasonal dynamics and stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) in four representative tree species—Juglans mandshurica Maxim., Phellodendron amurense Rupr. Quercus mongolica Fischer ex Ledebour and Fraxinus mandschurica Rupr.—at the Harbin Urban Forestry Demonstration Base, over the period 2022–2024. We monitored the nutrient content in tree leaves, trunks, branches, shrubs, herbaceous plants, and soil. Specifically, leaf N content in J. mandshurica decreased from 2.5% in May to 1.2% in November, while leaf P content in P. amurense dropped from 0.15% in June to 0.08% by the end of the growing season. Nutrient content in tree trunks and branches increased in the later growth stages, with trunk C content in Q. mongolica rising from 45% in May to 52% in November. Soil nutrients generally decreased over the growing season, with soil P content in F. mandshurica plantations declining from 0.12% in May to 0.06% in September. Moreover, the C:N and C:P ratios in tree and herb leaves, as well as in soil, increased during the growing period, while the N:P ratio in shrubs increased towards the end of the growth cycle. The study found significant correlations between specific nutrients in the leaves of trees and their surrounding soils. For instance, leaf C in J. mandshurica was positively correlated with soil C, while herbaceous plant P was positively correlated with soil N and leaf N with soil P. These relationships suggest that leaf N absorption is limited by soil P and herbaceous P by soil N. The analysis of nutrient correlations between shrubs, herbs, and trees showed a partial positive correlation between understory plants and tree leaf nutrients, indicating relatively weak competition among different plant groups. Furthermore, in P. amurense plantations, the P content in understory herbs was significantly positively correlated with soil P, suggesting that low soil phosphorus limits tree growth in this area. No significant correlation between soil and leaf nutrients was found in Q. mongolica plantations. In contrast, in F. mandshurica plantations, soil C and N were significantly positively correlated with tree leaf C, and understory shrub P and herb P were positively correlated with soil P, suggesting that leaf C absorption is constrained by soil C and N. Overall, this study highlights the nutrient competition between understory vegetation and tree layers, with all species showing a negative correlation between understory vegetation and tree nutrients, indicating nutrient competition. These findings provide valuable insights into the ecological dynamics of urban forests and offer guidance for optimizing urban forest management strategies. Full article

The degradation of black soil cropland has occurred to varying degrees in the northern agropastoral ecotone. Crop–forage rotation is an effective way to improve soil quality, with Medicago being the preferred perennial legume. The C, N, and P stoichiometric ratios are key indicators of soil quality and organic matter composition, reflecting the status of the internal C, N, and P cycles in soil. This study aims to investigate the ecological stoichiometric ratios of Medicago grassland soils with different planting durations, explore the regulatory effects of nitrogen fertilizer on soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) content, and assess the impacts of these changes on the Medicago grassland ecosystem. This study was conducted on the long-term cultivated grassland core experimental platform of the Hulunber National Field Station. Based on forage yield and soil nutrient measurements, field-based observations and laboratory analyses were carried out. Medicago × varia was the study subject, with different nitrogen fertilizer treatments: CK (0 kg N ha⁻¹), N₇₅ (75 kg N ha⁻¹), and N₁₅₀ (150 kg N ha⁻¹). A randomized block design was adopted. Variance analysis, boxplot statistics, and scatterplot fitting methods were used to examine soil properties and assess the effects of nitrogen application on the C, N, and P stoichiometry of soils in established perennial Medicago grasslands. The results indicate that, based on the growth characteristics of alfalfa, soil nutrient dynamics, and its effectiveness in improving soil quality, the optimal rotation period for alfalfa in the northern agropastoral ecotone is 4–5 years, but it can also be shortened to 3 years. Soil carbon, nitrogen, and phosphorus contents are significantly influenced by the planting duration. As the planting years increase, soil carbon and nitrogen contents first increase and then decrease, while soil phosphorus content initially decreases followed by a slight increase. Soil pH gradually rises with both planting years and soil depth. Both low and high levels of nitrogen fertilizer application reduce soil organic carbon concentration (by 0.40% and 10.14%, respectively). Low nitrogen fertilizer application increases soil nitrogen concentration (by 1.50%), whereas high nitrogen fertilizer application decreases it (by 7.6%). Both nitrogen levels increase soil phosphorus concentration (by 36.67% and 35.26%, respectively). For soil from an alfalfa grassland planted for 8 years, the carbon-to-nitrogen ratio ranges from 9.08 to 9.76, the carbon-to-phosphorus ratio from 13.00 to 151.32, and the nitrogen-to-phosphorus ratio from 1.65 to 17.14. In summary, alfalfa yield is primarily influenced by the nitrogen fertilizer application rate, planting duration, stoichiometric ratios, and pH. Nitrogen fertilizer application has a positive regulatory effect on soil stoichiometric ratios. The annual yield can reach 8.94 to 10.07 tons per hectare., but phosphorus remains a limiting factor. These findings provide crucial data for understanding the impact of ecological stoichiometry on crop–forage rotation cycles, as well as optimal land use and quality improvement. Full article

Water and fertilizer application strategies seriously affect the healthy growth of peanuts. The stoichiometric ratio can directly reflect the elemental requirements for crop growth, which are very important for improving fertilizer utilization efficiency. In order to investigate the response of C (carbon), N (nitrogen), and P (phosphorus) allocation pattern and stoichiometric characteristics in peanut seedlings to water and nitrogen addition, we designed a greenhouse pot experiment which had different water treatments (W1, 75–80% field capacity; W2, 45–50% field capacity) and nitrogen addition treatments (N0, 0 kg hm⁻²; N1, 90 kg hm⁻²; N2, 180 kg hm⁻²). The distribution and content changes in C, N, and P in different organs were measured and analyzed by ecological stoichiometry. The results showed that drought stress significantly increased the N or P content of different organs. The average N/P value of peanut roots treated with W2 decreased by 13.02% compared to W1. Restoring irrigation relieved this stress while reducing the C/N and C/P of roots, stems, and leaves, as well as the N/P of roots and stems. The water treatment after rehydration showed significant differences in the C/N, C/P, and N/P ratios of peanut roots. The average values of the C/N, C/P, and N/P ratios of peanut roots in W2 treatment were reduced by 13.54%, 28.66%, and 16.34%, respectively, compared to W1 treatment. On the other hand, nitrogen application significantly increased the N content of stems and leaves, while reducing C/N. On the contrary, it significantly reduced the P content of roots and stems, and increased the N/P ratio of roots, stems, and leaves. Overall, there is a significant interaction between water and nitrogen treatment on the stoichiometric characteristics of C, N, and P in different organs, with water treatment playing a dominant role. In terms of nutrient distribution in organs, the average N content in leaves is the highest. The coefficient of variation (CV) of P content is greater than that of C and N content. The CV of N content, P content, and C/N and N/P ratios of the stem are all greater than those of the roots or leaves, while the stems are more sensitive to water and nitrogen conditions. And the N and P content of roots, stems, and leaves were positively correlated. Meanwhile, peanut seedlings have the phenomenon of ionic synergism that occurs between nitrogen and phosphorus ions. In summary, studying the stoichiometric ratios can reflect the water and fertilizer demand status of peanuts, thereby better improving water and fertilizer utilization efficiency. Full article

Optimizing plant density and nutrient availability is essential for sustaining high forage yields and promoting environmental health, especially in semi-arid regions with sandy soil. Nonetheless, the mechanisms by which stoichiometric features govern nutrient utilization and forage output are still unidentified. We executed a two-year field experiment, integrating six nitrogen rates (0 (N0), 104 (N1), 138 (N2), 173 (N3), 207 (N4), and 242 (N5) kg N ha⁻¹) and four planting densities (3 (D1), 3.5 (D2), 4 (D3), and 4.5 (D4) million plants ha⁻¹). The C, N, and P contents, along with the C:N:P stoichiometry of different oat organs (leaf, stem, and root) and soil, were determined. It was found that the growth of oats in this area was limited by soil N. The pasture biomass increased nonlinearly with increasing planting density and N rate, and the maximum thresholds for C, N, and P uptake were 389.43 g kg⁻¹, 11.19 g kg⁻¹, and 3.10 g kg⁻¹ at N3, respectively. The maximum thresholds for C, N, and P uptake were 356.45, 9.47, and 2.78 g kg⁻¹ at D3, respectively, with an optimal biomass of 9221.74 kg ha⁻¹; at a planting density of D3, the maximum thresholds for C, N, and P uptake were 329.39, 8.54, and 2.47 g kg⁻¹, with an optimal biomass of 6276.10 kg ha⁻¹. SEM showed that N rate and density increases significantly changed the ecological balance of the soil. The C:N and C:P ratios in oat leaves tend towards lower values, while the N:P ratio tends towards higher values; in contrast, the C:N and C:P ratios in oat stems tend towards higher values, and the N:P ratio tends towards lower values. The nutrient use strategy maintains the stoichiometric balance at the organ level, which in turn improves the accumulation of oat biomass. The best NUE was obtained at an N rate and density of N3D3 with a 144% biomass increase as compared to N0D2. This study provides new insights into nutrient allocation, usage strategies, and the stability of oats in actual sandy land production. Full article

Understanding the relationships between nutrient content in plant roots and ecological stoichiometry is crucial for elucidating nutrient utilization strategies and material cycling in alpine plant communities. However, data characterizing the stoichiometric characteristics of plant roots in this region remain limited. In this study, we collected fine-root and soil samples from five common alpine shrub species—Salix gilashanica, Potentilla fruticosa, Caragana jubata, Caragana tangutica, and Berberis diaphana—to investigate the carbon (C), nitrogen (N), and phosphorus (P) stoichiometric characteristics of their fine roots and examine the potential nutrient control strategies based on the soil properties. Our analysis revealed that the mean C (541.38 g kg⁻¹) and P (1.10 g kg⁻¹) contents in the shrub fine roots exceeded the average levels of the plant roots in China. However, the mean N content (8.61 g kg⁻¹) was lower than the global average. Notably, the mean C:N ratio (71.3) in these fine roots was significantly higher than the global average, whereas both the mean C:P ratio (527.61) and N:P ratio (8.11) were considerably lower. The N:P ratios in the fine roots of the five shrub species were below 14, indicating nitrogen limitation for growth in the degraded alpine shrub communities. Our findings indicate that soil available phosphorus (33.2%) and pH (20.5%) are the primary factors influencing the eco-stoichiometric characteristics of shrub fine roots in the Qilian Mountains. These findings provide valuable data and theoretical support for a better understanding of the role of shrub roots in nutrient cycling within alpine ecosystems. Full article

Amid global desertification, this study investigates karst ecosystems; analyzing soil’s physiological and ecological properties within intricate fissure networks supporting plant root growth. This study investigates soil nutrients in three types of rocky fissure network habitats in Maolan, through field surveys and experimental measurements. Significant variability was found across habitats. The quantities of organic carbon, total nitrogen, available nitrogen, available phosphorus, and available potassium were highest in Type I soil, followed by Type III; and were lowest in Type II. Total phosphorus was highest in Type III, intermediate in Type I, and lowest in Type II; while total potassium content was highest in Type III, moderate in Type II, and lowest in Type I. Based on nutrient participation in C, N, P, and K cycles, Type I habitats had the highest levels, Type III had moderate levels, and Type II had the lowest levels; while potassium-related nutrients were highest in Type III. The nutrient ratios C/K, N/K, P/K, and N/P were highest in Type I, moderate in Type II, and lowest in Type III. C/N was highest in Type II, moderate in Type III, and lowest in Type I; while C/P was highest in Type II, moderate in Type I, and lowest in Type III. A comprehensive nutrient evaluation ranked Type I as the best, Type III as moderate, and Type II as the worst. Key factors such as average trace length, areal density, and integration significantly influence soil nutrients by impacting humus and soil storage, and the growth space for plant roots within rocky habitats. Additionally, the orientation of fissures primarily impacts nutrient cycling, while both the angles and lacunarity significantly affect the stoichiometric ratios of nutrients. Rocky habitat networks characterize soil quality. A comparison of existing studies reveals stoichiometric differences between karst and non-karst regions. Effective ecological restoration in karst areas requires targeted strategies that consider the specific attributes of different rocky habitats. This study enhances understanding of soil nutrients in karst forest ecosystems and proposes new approaches for soil’s ecological restoration and combating global desertification. Full article

Active vegetation restoration plays an important role in the improvement in soil organic matter (SOM), including the carbon (C), nitrogen (N) and phosphorus (P) sequestration of degraded mining ecosystems. However, there is still a lack of understanding of the key drivers of SOM pool size and dynamics in active vegetation restoration. For this study, soil was collected from five different sites (Xiaoxian, Dingyuan, Chaohu, Tongling and Dongzhi), four habitats (platforms, slopes, steps and native areas) and two soil layers (0–20 cm and 20–40 cm) in limestone mines of Anhui province to quantify the spatial distribution of SOM contents and their stoichiometric characteristics and influential factors. It was found that the top soil in Chaohu had the highest significant C, N and P contents in the ranges of 14.95–17.97, 1.74–2.21 and 0.80–1.24 g/kg, respectively. Comparing the stoichiometric ratios of the different sites revealed significant differences in C:N and N:P ratios, but C:P ratios were relatively consistent. In particular, the C:N and C:P ratios in deep soil were higher than those in top soil, whereas the N:P ratio in deep soil was lower than that in top soil, suggesting that soil N is a major limiting factor in the top soil. The SOM content did not differ significantly between the three reclaimed habitats, but was significantly higher than that in the native habitat, suggesting that mine restoration has significantly enhanced SOM accumulation. Further analysis showed that nutrient availability and enzyme activity are important factors affecting soil C, N and P content in top soil, while the relationship gradually weakens in deep soil. This was attributed to active anthropogenic management and conservation measures during the early stages of reclamation. This study shows that the ecological recovery of the mining area can be enhanced by implementing differentiated vegetation planting strategies and anthropogenic management on different habitats in the mining area. 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

Pinus yunnanensis is an endemic tree species in southwest China that has high ecological and economic benefits. Nowadays, global climate change is remarkable, the frequency of drought is increasing day by day, the distribution of rainfall is unbalanced, and even the phenomenon of alternating drought and flood has appeared, which is unfavorable to the growth of P. yunnanensis. We set up four treatments, namely normal water (CK), light drought (LD), moderate drought (MD), and severe drought (SD), and water content was controlled by the weighing method. After continuous drought for 30 days, re-watering was performed for 7 days. The stoichiometric characteristics of non-structural carbohydrates (NSC), soluble sugars (SS), and starch (ST), as well as carbon (C), nitrogen (N), and phosphorus (P), in various organs of P. yunnanensis seedlings were measured. The results revealed significant effects of re-watering on NSC and its components in P. yunnanensis seedlings. The SS and NSC contents in the leaves of P. yunnanensis seedlings treated with SD were significantly higher than those of the control. The C content in the leaves and stems of P. yunnanensis seedlings recovered to the CK level after re-watering under different drought degrees. The contents of N in different organs and P in the fine roots of P. yunnanensis seedlings increased after re-watering with the LD, MD, and SD treatments, while the C/N ratio decreased. In summary, the recovery mechanism of P. yunnanensis seedlings to re-watering varied with the drought degree. The contents and ratios of NSC, C, N, and P in different organs of P. yunnanensis seedlings were significantly affected by re-watering. Combining the phenotypic plasticity index and PCA results, seedlings of P. yunnanensis adapted to drought re-watering by adjusting leaf NSC, leaf P, stem SS/ST, fine root ST, and fine root NSC. Full article

Forest gaps alter the environmental conditions of forest microclimates and significantly affect the biogeochemical cycle of forest ecosystems. This study examined how forest gaps and non-gap areas affect soil’s physical properties and eco-stoichiometric characteristics. Relevant theories and methods were employed to analyze the impact of forest gaps on nutrient cycling in Pinus densiflora Sieb. (PDS) and Robinia pseudoacacia L. (RPL) forests located in the Taishan Mountains. The results revealed that (1) forest gaps significantly enhanced the soil physical properties of PDS and RPL forests compared to non-gap areas (NPs). Notably, the bulk density of the soil decreased by 53%–12%, particularly in the surface layer (0–20 cm). Additionally, its non-capillary porosity increased by 44%–65%, while the clay and silt content rose by 39%–152% and 24%–130%, respectively. Conversely, the sand content decreased significantly, by 24%–32% (p < 0.05). (2) The contents of C, N, and P in the gap soil of PDS forests showed a significant increase compared to those in non-gap soil, with increases of 56%–131% for carbon, 107%–1523% for nitrogen, and 100%–155% for phosphorus. There was a significant drop of 10%–33% and 39%–41% in their C:N and C:P ratios, respectively (p < 0.05). The contents of C and P in the gap soil of the Robinia pseudo acacia L. Forest increased significantly, by 14%–22% and 34.4%–71%, respectively. Its C:P and N:P ratios significantly increased, by 14% to 404% and 11% to 41%, respectively (p < 0.05). (3) Compared with NPs, the forest gap significantly reduced the soil electrical conductivity and increased the soil pH. Additionally, compared to the soil at the gap’s edge, the surface soil in the gap’s center had noticeably higher concentrations of C, N, and P. (4) Key variables affecting the soil pH, silt content, bulk density, and overall porosity in forest gaps include the concentrations of carbon (C), nitrogen (N), and phosphorus (P) present and their ecological stoichiometric ratios. The findings showed that forest gaps had a considerable impact on the soil’s physical characteristics and ecological stoichiometry. They also had a high potential for providing nutrients, which might aid in the establishment of plantation plants. Full article