Ecological Stoichiometry Research Articles

Effect of river-lake connectivity on ecological stoichiometry of lake and carbon storage status in Eastern Plain, China.

C, N, and P in lake sediment are the basis of material and energy cycle, reflecting the economic development, ecological function, and environmental effect. Current research on the effect of lake eutrophication on carbon storage and the river-lake connectivity on nutrient diffusion is lack. This work investigated the accumulation, distribution, correlations, and stoichiometric ratios of C, N, and P of 82 lakes (≥ 10km2) in Eastern China, analyzed the nutrient limitation, sediment carbon sink, and effect of river-lake connectivity, and discussed the relationships between eutrophication and sediment carbon storage. The average concentrations and ranges of total C, N, and P in lake sediments were (23.26mg/g, 0.08-153.45mg/g), (2.32mg/g, 0.29-14.17mg/g), and (0.86mg/g, 0.23-2.64mg/g), respectively. The ecological stoichiometry of C: N: P in lake sediments was 32: 3.2: 1. P can be easily accumulated in lakes connected from the Yangtze River, while C and N can be easily accumulated in disconnected lakes. The soil-water erosion in runoff is an important factor for P diffusion. The C/N and C/N/P weren't affected by the river-lake connectivity but depended on the plant type. The Eastern Plain Lake Region of China is C and N co-depletion, and P enrichment. The lake eutrophication leading to algal bloom is unfavorable to the goal of carbon storage and carbon neutrality. Outcome of this study will provide a significant reference and strategies for carbon sequestration research, eco-environmental protection, and watershed nutrient management.

Biomass, community composition and N:P recycling ratios of zooplankton in northern high‐latitude lakes with contrasting levels of N deposition and dissolved organic carbon

Abstract Global changes are causing decreases in inorganic nitrogen (N) concentrations, increases in coloured dissolved organic carbon (DOC) concentrations, and decreases in dissolved inorganic N to total phosphorus ratios (DIN:TP) in northern lakes. The effects of these changes on phytoplankton and zooplankton biomass and the N:P recycling ratio of zooplankton remain unresolved. In 33 Swedish headwater lakes across subarctic‐to‐boreal gradients with different levels of N deposition (low N in the north [Västerbotten, boreal; Abisko, subarctic] vs. high N in the south [Värmland, boreal; Jämtland, subarctic]), we measured water chemistry, phytoplankton biomass (chlorophyll‐a [Chl‐a], Chl‐a:TP), seston mineral quality (C:P, N:P), as well as zooplankton biomass, community composition, and C:N:P stoichiometry. We estimated nutrient imbalances and the N:P recycling ratios of zooplankton using ecological stoichiometry models. There was a large‐scale gradient from low lake DIN and DIN:TP in the north to high DIN and DIN:TP in the south, with lower DIN:TP in lakes coinciding with higher DOC within each region. Lower lake DIN was associated with lower phytoplankton biomass (lower Chl‐a:TP). Lower lake DIN:TP was associated with richer seston mineral quality (lower seston C:P and N:P) and higher zooplankton biomass. Zooplankton community composition differed in the north vs. south, with a dominance of N‐requiring calanoid copepods with high N:P in the north and P‐requiring cladocerans with low N:P in the south. Also, greater differences in zooplankton community composition were found between subarctic regions (with lower DOC) than between boreal regions (with higher DOC), suggesting that increases in lake DOC and associated declines in lake DIN:TP reduce differences in zooplankton community composition. The combination of lower lake DIN, higher lake DOC, and lower lake DIN:TP led to reduced zooplankton N:P recycling ratios, possibly by reducing seston N:P and/or by enhancing calanoid copepod dominance in the zooplankton community. Our findings suggest that the combination of declining N deposition and increasing lake browning in northern high‐latitude lakes will reduce phytoplankton biomass, but will concurrently enhance seston mineral quality and probably also zooplankton biomass and their recycling efficiency of P relative to N.

Application of ionomics and ecological stoichiometry in conservation biology: Nutrient demand and supply in a changing environment

The application of ionomics and ecological stoichiometry benefits conservation biology with necessary ecological and evolutionary relevance, allowing unresolved problems to be addressed. The use of ionomics and ecological stoichiometry enables consideration that changes in the environmental nutritional supply affect the ecophysiology, behavior, health and fitness of individuals, influencing their ecological interactions and population functioning. The resulting knowledge can help promote better conservation and restoration strategies. Ultimately, ionomics and ecological stoichiometry facilitate improved forecasting and mitigation of the negative effects of current global change. Here, we present the theoretical background followed by the application of ionomics and ecological stoichiometry in biological conservation. We also propose avenues for future research. For example, larval and adult pollinating insects belong to different feeding guilds, and larvae rely on various stoichiometrically (im)balanced foods (showing herbivory, pollinivory, detritivory or even carnivory). Therefore, the ecology and diversity of pollinators may be shaped by the nutritional quality of larval food, which is required for physiological development into fully functional adults. Although a stoichiometric balance during larval development is crucial for pollinator health and fitness, pollinator conservation is focused on the nutritional needs of adults. Another example is atmospheric CO2 increases leading to nutrient dilution in plant tissues, aggravating nutritional imbalances in consumers and challenging Earth's herbivore populations. CO2-driven nutrient dilution may affect food webs, ecosystems and human wellbeing. However, our understanding of this phenomenon is minimal. These and other unresolved conservation biology problems may be studied and solved using ionomics and ecological stoichiometry.

Spatial distribution patterns and influencing factors of soil carbon, phosphorus, and C:P ratio on farmlands in southeastern China

Soil organic carbon (SOC), total phosphorus (STP), and the carbon-to-phosphorus ratio (C:P) are important indicators of soil fertility. Knowledge regarding the spatial patterns of SOC, STP, and C:P and their influencing factors are of great significance for precise fertilization, soil management, food security, environmental protection, and global climate change. A total of 16,582 topsoil samples (0–20 cm depth) were collected from farmland in Jiangxi Province, southeastern China. The spatial variability and driving factors of SOC, STP, and C:P were characterized using classical statistics, geostatistical analysis, and random forest (RF) methods. The results showed that the mean values of SOC, STP, and C:P were 17.90 g kg−1, 0.52 g kg−1, and 38.29, and their coefficients of variation were 30.98%, 33.49%, and 45.08%, respectively, indicating a moderate degree of variability. The RF model contained 47 explanatory variables related to parent materials, soil types, soil physicochemical properties, environmental variables, climate, farmland use types, straw returning methods, and fertilizer application rates, which accounted for 72.70%, 60.89%, and 63.71% of the spatial variability in SOC, STP, and C:P, respectively. Soil physicochemical properties had the most significant influence on SOC, STP, and C:P, with contributions of 45.83%, 50.93%, and 51.06%, respectively. Of all the factors, soil total nitrogen was identified as mostly driving the spatial distributions of SOC, STP, and C:P (variable importance of 29.39%, 11.72%, and 23.95%, respectively), followed by the nitrogen application rate (variable importance of 20.90%, 11.37%, 12.79%, respectively). Therefore, conservation tillage, crop rotation, straw return, combined application of nitrogen and phosphorus, and green manure application are the most effective measures for improving carbon sequestration and phosphorus availability. According to the ecological stoichiometry characteristics of carbon, nitrogen, and phosphorus and their temporal variation trends, the farmland soils in Jiangxi Province are typical carbon sink systems that are likely to be limited by phosphorus. The results of this study provide important insights for assessing soil carbon and phosphorus pools and sustainable agricultural development.

Functional Diversity of Plant Communities in Relationship to Leaf and Soil Stoichiometry in Karst Areas of Southwest China

Assessment of relationships between functional diversity and ecological stoichiometry in plant communities can aid in determining the relative variability and ecological complementarity of functional attributes among species, which is a better approach to understanding ecosystem processes and functions than studying species taxonomic diversity. Here, we analyzed the relationships among community weighted means of functional traits, functional diversity, and leaf and soil chemical properties of plant communities during various stages of vegetation restoration in Mao Lan National Karst Forest Nature Reserve, located in humid subtropical Guizhou of China. Our results showed significant changes in four weighted functional traits of plant communities at different restoration stages, namely, plant height, leaf width to leaf length ratio, and leaf area. Additionally, with the progression of the recovery of plant communities, functional richness, functional separation, and quadratic entropy, the coefficient tended to increase. Functional divergence tended to gradually decrease. The association of functional diversity with soil chemical properties was stronger than that with leaf ecological stoichiometry. Regarding leaf and soil chemical properties, soil phosphorus content and leaf C:P were particularly important in influencing functional diversity. Our overall findings indicate that functional traits shift from “acquisitive” to “conservative” as the community is restored. Karst plant communities reduce interspecific resource competition as restoration proceeds, thereby increasing functional overlap effects.

Eutrophication drives regime shift via changes in stoichiometric homeostasis-based submerged macrophyte assemblages

Homeostasis for phosphorus (HP) in submerged macrophytes may influence the susceptibility of lakes to regime shifts; however, the mechanisms linking submerged macrophyte HP to regime shifts remain unclear. We conducted an in situ mesocosm experiment to compare the dynamic responses of a high-HP species, Potamogeton maackianus, and a low-HP species, Hydrilla verticillata, to different phosphorus (P) level gradients, as well as their effects on phytoplankton inhibition. The biomass of P. maackianus under mesotrophic P (MP; P concentration 0.05 mg L−1) and eutrophic P (EP; P concentration 0.10 mg L−1) conditions was either non-significantly different from, or lower than that under oligotrophic P conditions (OP; P concentration under detection limit of 0.01 mg L−1). Conversely, H. verticillata biomass under EP was significantly higher than that under MP on day 90, whereas it died under OP. This variable response of submerged macrophyte species to P level gradients increased the relative growth advantage of H. verticillata compared to P. maackianus during eutrophication. The inhibition ratio of phytoplankton (IRP) for P. maackianus was ~15 times higher than that for H. verticillata under EP. Our study demonstrated a trend that submerged macrophyte assemblage IRP increased along with its assemblage HP. Thus, the changes in submerged macrophyte assemblages from high-HP species-dominance to low-HP species-dominance would erode its phytoplankton inhibition capacity, and further promote the regime shift from a clear-water state to a turbid state. Our results advance the regime shift theory from an ecological stoichiometry perspective and highlight the importance of high-HP submerged macrophyte species in the restoration of eutrophic lakes.

Carbon, Nitrogen and Phosphorus Stoichiometry in Natural and Plantation Forests in China

Ecological stoichiometry is essential for understanding the biogeochemical cycle in forest ecosystems. However, previous studies of ecological stoichiometry have rarely considered the impacts of forest origins, which could help explain why to date so much uncertainty has been reported on this subject. In this study, we tried to reduce this uncertainty by examining carbon (C), nitrogen (N) and phosphorus (P) in roots, litter and soil in both natural and plantation forests throughout China. The sampled forest sites were divided into three groups according to the identified succession stages: early (ES), middle (MS) and late (LS) stages. Our results show that soil C, N and P concentrations were significantly higher in natural (NF) than in plantation (PL) forests. As succession/growth proceeded, P concentrations significantly increased in litter, roots and soil in NF, while the opposite occurred in PL. These results indicate that NF are able to use P more efficiently than PL, especially in the LS. Furthermore, the higher root N:P ratio indicates that the growth of PL was limited by P in both MS and LS. Our results also suggest that geographical and climatic factors are not the dominant factors in the differences in P between NF and PL, and, even more clearly and importantly, that native forests with native species are more capable of conserving P than planted forests, which are frequently less diverse and dominated by fast-growing non-site native species. These results will help improve biogeochemical models and forest management throughout the world.

Adaptive Pathways of Microorganisms to Cope With the Shift From P- to N-Limitation in Subtropical Plantations.

Ecological stoichiometry is increasingly acknowledged as one of the main control factors for microbial activity and diversity. Soil carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratios are usually much higher than microbial nutrient requirements and vary with planting density and stand age in forestlands. However, how microorganisms cope with such stoichiometric imbalances and how they regulate nutrient cycling remain unclear. Here, 5- and 35-year-old experimental Cunninghamia lanceolata [Lamb.] Hook plantations with five planting densities (1,667, 3,333, 5,000, 6,667, and 10,000 stems ha−1) were used to explore the underlying mechanism of the response of microorganisms to stoichiometric imbalances. We found that (i) enzyme activity and microbial biomass and diversity increased with planting density at age 5 but decreased at age 35; (ii) soil microorganisms were P-limited at age 5, but gradually shifted from P- to N-limitation during the development of plantations from 5 to 35 years; and (iii) significantly negative relationships between microbial biomass stoichiometry and enzymatic stoichiometry were observed. The adaptive pathways of soil microorganisms to cope with stoichiometric imbalances include (i) adjusting the stoichiometry of microorganisms and enzymes; (ii) changing the relative abundance of the dominant microbial phyla; and (iii) increasing the ratio of fungal to bacterial diversity. These results highlight how to use the ecological stoichiometry method to identify soil microbial nutrient limitations with planting density during the development of plantations. By underlining the important role of stoichiometry on microbial growth and activity, these findings furthermore emphasize the dependency of organic matter transformation and nutrient cycling on the microbial community.

Food web perspectives and methods for riverine fish conservation

AbstractFood web analyses offer useful insights into understanding how species interactions, trophic relationships, and energy flow underpin important demographic parameters of fish populations such as survival, growth, and reproduction. However, the vast amount of food web literature and the diversity of approaches can be a deterrent to fisheries practitioners engaged in on‐the‐ground research, monitoring, or restoration. Incorporation of food web perspectives into contemporary fisheries management and conservation is especially rare in riverine systems, where approaches often focus more on the influence of physical habitat and water temperature on fish populations. In this review, we first discuss the importance of food webs in the context of several common fisheries management issues, including assessing carrying capacity, evaluating the effects of habitat change, examining species introductions or extinctions, considering bioaccumulation of toxins, and predicting the effects of climate change and other anthropogenic stressors on riverine fishes. We then examine several relevant perspectives: basic food web description, metabolic models, trophic basis of production, mass‐abundance network approaches, ecological stoichiometry, and mathematical modeling. Finally, we highlight several existing and emerging methodologies including diet and prey surveys, eDNA, stable isotopes, fatty acids, and community and network analysis. Although our emphasis and most examples are focused on salmonids in riverine environments, the concepts are easily generalizable to other freshwater fish taxa and ecosystems.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness Water and Life > Methods

In defense of elemental currencies: can ecological stoichiometry stand as a framework for terrestrial herbivore nutritional ecology?

Nutritional ecologists aim to predict population or landscape-level effects of food availability, but the tools to extrapolate nutrition from small to large extents are often lacking. The appropriate nutritional ecology currencies should be able to represent consumer responses to food while simultaneously be simple enough to expand such responses to large spatial extents and link them to ecosystem functioning. Ecological stoichiometry (ES), a framework of nutritional ecology, can meet these demands, but it is typically associated with ecosystem ecology and nutrient cycling, and less often used to study wildlife nutrition. Despite the emerging zoogeochemical evidence that animals, and thus their diets, play critical roles in nutrient movement, wildlife nutritional ecology has not fully embraced ES, and ES has not incorporated nutrition in many wildlife studies. Here, we discuss how elemental currencies are "nutritionally, organismally, and ecologically explicit" in the context of terrestrial herbivore nutritional ecology. We add that ES and elemental currencies offer a means to measure resource quality across landscapes and compare nutrient availability among regions. Further, we discuss ES shortcomings and solutions, and list future directions to advance the field. As ecological studies increasingly grow in spatial extent, and attempt to link multiple levels of biological organization, integrating more simple and unifying currencies into nutritional studies, like elements, is necessary for nutritional ecology to predict herbivore occurrences and abundances across regions.

Dynamics of soil aggregate‐related C‐N‐P stoichiometric characteristics with stand age and soil depth in Chinese fir plantations

AbstractSoil C‐N‐P stoichiometry offers an effective way to explore the balance, limitation, cycling, and distribution of chemical elements in Chinese fir plantations. This research aimed to explore how soil organic C (Corg), total N (Ntot), and total P (Ptot) contents and stocks, together with their stoichiometric ratios vary with stand age (3, 9, 17, and 26 years) as well as soil layer (0–10, 10–20, 20–30, and 30–40 cm) at aggregate scales in Chinese fir plantations from Guangxi, China. For Chinese fir plantations of diverse ages, soil aggregate stability, Corg, Ntot, and Ptot contents and stocks, together with C/N, C/P, and N/P ratios, remarkably declined when soil depth increased. Stand age could influence C‐N‐P stoichiometric characteristics in soil, but such effect was more obvious in soil depth of 0–30 cm in comparison to that of 30–40 cm. In 0–30 cm soil layer, Corg and Ntot contents and stocks, together with C/P and N/P ratios, first rose and then reduced during Chinese fir planting; meanwhile, the highest levels could be observed in the 17‐year‐old Chinese fir plantations. However, Ptot content and stock, together with C/N ratio, were not related to the stand age. Overall, the present research helped to understand soil C, N, and P dynamics within a chronosequence of Chinese fir plantations. Also, it provided supplementary information for soil ecological stoichiometry in global terrestrial ecosystems.

Deposition Flux, Stocks of C, N, P, S, and Their Ecological Stoichiometry in Coastal Wetlands With Three Plant Covers

The depositional flux of coastal wetlands and the deposition rate of biogenic elements greatly affect the carbon sink storage. Ecological stoichiometry is an important ecological indicator, which can simply and intuitively indicate the biogeochemical cycle process of the region. This study investigated the soil deposition flux, stocks, and ecological stoichiometric ratios of C, N, P, and S under different water and salt conditions based on 137Cs dating technology in the Yellow River Delta (YRD) of China. The results showed that the deposition fluxes were 0.38 cm/year for PV wetlands, 1.08 cm/yr for PA wetlands, and 1.06 cm/yr for SS wetlands. Similarly, PA wetlands showed higher deposition fluxes of C, N, and S compared with SS and PV wetlands. PA wetlands had higher stocks of C (5.86 kg/m2), N (0.36 kg/m2) and S (0.36 kg/m2) in the top 1-m soil layer compared with PV and SS wetlands. However, the highest deposition rate of P (9.82 g/yr/m2) was observed in SS wetlands among the three wetlands. Three accumulative hotspots of C, N, and S in soil profiles of PA and SS wetlands were observed at soil depths of 0–10, 40–60, and 90–100 cm, whereas one accumulative hotspot of P was at the soil depth of 10–12 cm in SS wetlands and 80–82 cm in PA wetlands. PV wetlands showed higher accumulations of C, P, and S in the top 10 cm soil layer and N at the soil depth of 90–100 cm. The higher top concentration factors in these three wetlands indicated that the dominant input of plant residues was the main reason. The ratios of C/N and C/N/P of each sampling site were higher in the surface soils and decreased with depth. The ratios of C/P and N/P were larger in the surface layer (0–20 cm), the middle layer (40–60 cm), and the deep layer (90–100 cm). The ratios of N/P and C/N/P were relatively lower, indicating that these studied wetlands were N-limited ecosystems. The results implied that the coastal wetlands in the YRD have huge storage potential of biogenic elements as blue carbon ecosystems.

Biochar Addition Alters C: N: P Stoichiometry in Moss Crust-Soil Continuum in Gurbantünggüt Desert.

The biogeochemical cycling of soil elements in ecosystems has changed under global changes, including nutrients essential for plant growth. The application of biochar can improve the utilization of soil nutrients by plants and change the stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in plants and soil. However, the response of ecological stoichiometry in a moss crust-soil continuum to local plant biochar addition in a desert ecosystem has not been comprehensively explored. Here, we conducted a four-level Seriphidium terrae-albae biochar addition experiment (CK, 0 t ha−1; T1, 3.185 t ha−1; T2, 6.37 t ha−1; T3, 12.74 t ha−1) to elucidate the influence of biochar input on C: N: P stoichiometry in moss crusts (surface) and their underlying soil (subsurface). The results showed that biochar addition significantly affected the C, N, and P both of moss crusts and their underlying soil (p < 0.001). Biochar addition increased soil C, N, and P concentrations, and the soil N content showed a monthly trend in T3. The C, N, and P concentrations of moss crusts increased with the addition levels of biochar, and the moss crust P concentrations showed an overall increasing trend by the month. Moreover, the soil and moss crust C: P and N: P ratios both increased. There was a significant correlation between moss crust C, N, and P and soil C and N. Additionally, nitrate nitrogen (NO3−N), N: P, C: P, EC, pH, soil moisture content (SMC), and N have significant effects on the C, N, and P of moss crusts in turn. This study revealed the contribution of biochar to the nutrient cycle of desert system plants and their underlying soil from the perspective of stoichiometric characteristics, which is a supplement to the theory of plant soil nutrition in desert ecosystems.

Ecological Stoichiometry in Pinus massoniana L. Plantation: Increasing Nutrient Limitation in a 48-Year Chronosequence

Stoichiometric ratios of carbon (C), nitrogen (N), and phosphorus (P) are considered indicators of nutrient status and ultimate ecosystem health. A detailed investigation of these elements in the leaves, branches, forest layer vegetation and soil, depending on stand age, was carried out. We investigated the effects of stand age (9-, 18-, 28-, and 48-year) on the aboveground plant parts (leaf, branch, herb, shrub, plant litter) and belowground pools (soil, roots) of P. massoniana plantations. The CNP stoichiometry of trees was affected by stand age. Mean N content in the aboveground parts in the nine-yr stand was greater than the other stands (18-, 28-, 48-yr), which decreased with increasing stand age. As stands aged, the nutrient demands of the plantations increased as well as their N:P ratios in soil. C content in the soil ranged from 30 to 105, the total N was 0.06 to 1.6, and the total P content ranged from 3.3–6.4 g kg−1. Soil C, N and P contents were greatly influenced by both stand age and soil depth, because surface soil sequester C and N more actively compared to deeper horizons, and more nutrients are released to the topsoil by the plant litter layer. Similarly, the ratios of other layers had a similar pattern as CNP because more nutrients were taken up by the plantations, decreasing nutrient supply in the deeper soil horizons. The green leaves N:P ratios (16) indicate limited growth of P. massoniana, as the range for global nutrient limitation for woody plants oscillated between 14–16, indicating N and P limitation. Young stands were observed to have greater P content and P resorption efficiency (56.9%–67.3%), with lower C:P and N:P ratios (704.4; 14.8). We conclude that with stand development, the nutrient demands of the plantations also increase, and soil N:P stoichiometry shows that these improve soil quality.

Effects of Plastic Mulch Film on Soil Nutrients and Ecological Enzyme Stoichiometry in Farmland

Ecological enzyme stoichiometry can be used to evaluate the limit of soil microbial energy and nutrient resources. To illustrate the effects of plastic mulch film on soil ecological enzyme stoichiometry in farmland, this study collected soil with different amounts of mulching film residual and used the fluorescence analysis to determine the activities of key enzymes for the carbon, nitrogen, and phosphorus cycle processes including β-1,4-glycosidase (BG), β-1,4-N-acetyl amino glycosidase (NAG), and phosphatase (ACP) activity. This study investigated the effects of plastic mulch film on soil nutrient cycling and supply in farmland. The results showed that in the soil with chemical fertilizer, plastic film mulching decreased soil Olsen-P and NO3--N contents to 48%-62% and 16%-24% of those in the soil without plastic film mulching, respectively. In the soil with the combined application of organic-chemical fertilizers, plastic film mulching increased Olsen-P and NO3--N contents by 144%-203% and 1.9-5.1 times, respectively. In the organic-chemical fertilization soils, plastic film mulching decreased SOC:TN in soils by 6.6%-25.8%, whereas it increased SOC:TP and TN:TP significantly. MBC, MBN, and MBP contents in the soil with plastic film mulching were significantly lower than that in non-plastic film mulching farmland, and there were no significant differences in MBC:MBN and MBC:MBP between soil with and without plastic film mulching. The MBN:MBP was reduced by 36.6% and 23.8% in S1 and S2, and 5.4 and 1.3 times in S3 and S4 by plastic film mulching, respectively. The change pattern of NAG:ACP in soil was similar to that of the corresponding elements ratio in microbial biomass. In the soil from plastic film mulching, the ratio of BG:NAG was 1.3-15 times higher in organic-chemical fertilization soils than that with only chemical fertilizer. In conclusion, plastic film mulching reduced the availability of soil nutrients, and organic-chemical fertilization alleviated the limitation of soil nutrients to a certain extent. This study deepened the understanding of the response of soil microorganisms to nutrient cycling after plastic film mulching. It provides a theoretical basis for optimizing the farmland management in the use of plastic film.

Adaptation strategy of karst forests: Evidence from the community-weighted mean of plant functional traits.

Conservative survival strategy of plants growing in harsh karst habitats is observed from the view of plant functional traits, such as morphological traits and ecological stoichiometry. However, whether the plant communities in karst forests with high species turnover adopt a conservative strategy remains undetermined. This study comprehensively investigated the characteristics of functional traits of dominant plant species in four forests (i.e. Platycarya strobilacea, Quercus fabri, Quercus variabilis, and Pinus massoniana forests) in a trough‐valley karst watershed in Northern Guizhou Province, Southwestern China to explore the adaptation strategy of karst forests at the community level. At the organ and the species levels, traits differed among species, and the leaf and the bark morphological traits and root C:N:P ecological stoichiometry presented large interspecific variations. At the community level, the P. massoniana forest presented the lowest specific root length and dry matter content and tissue density of roots, branch, twig, and bark; the Q. fabri and the Q. variabilis forests displayed low specific leaf area and high dry matter content and tissue density of roots, branch, and twig; and the Platycarya strobilacea forest exhibited high specific leaf area. The P. massoniana forest was subjected to N and P colimitation, and the three other broad‐leaved forests were limited by P supply. The community‐weighted means rather than the arithmetic means of traits were preferential to represent the trait characteristics at the community level. From the view of plant functional traits at the community level, karst forests develop multiple functional traits like low specific leaf area, high dry matter content and tissue density of leaf, roots, branch, and twig, and decrease N and P investments in leaf for a conservative survival strategy to adapt to harsh habitats.

Variations in Ecological Stoichiometry Characteristics of C, N and P in Soils Beneath an &lt;i&gt;Abies fanjingshanensis&lt;/i&gt; Forest

Variations in Ecological Stoichiometry Characteristics of C, N and P in Soils Beneath an &lt;i&gt;Abies fanjingshanensis&lt;/i&gt; Forest

Role of Environment Variables in Spatial Distribution of Soil C, N, P Ecological Stoichiometry in the Typical Black Soil Region of Northeast China

The effects of environmental factors on topsoil nutrient distribution have been extensively discussed, but it remains unclear how they affect spatial characteristics of soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry at different depths. We collected 184 soil samples in the typical black soil region of northeast China. Ordinary kriging was performed to describe the spatial distribution of soil C, N, and P eco-stoichiometry. Redundancy analysis was used to explore relationships between C:N:P ratios and physicochemical characteristics. The soil classification was studied by hierarchical cluster analysis. The mean C, N, and P contents ranged from 15.67 to 20.08 g·kg−1, 1.15 to 1.51 g·kg−1, and 0.80 to 0.90 g·kg−1 within measured depths. C, N, and P concentrations and stoichiometry increased from southwest to northeast, and the Songhua River was identified as an important transition zone. At 0–20 cm, soil water content explained most of the C, N, and P content levels and ratios in cluster 1, while latitude had the highest explanatory ability in cluster 2. For 20–40 cm, soil bulk density was the main influencing factor in both clusters. Our findings contribute to an improved knowledge of the balance and ecological interactions of C, N, and P in northeast China for its sustainability.

Effects of precipitation changes on the stoichiometry and photosynthetic characteristics of Stipa bungeana Trin. at different growth stages in the Loess Plateau, China

AbstractThe aim of this study was to explore the response of the stoichiometric and photosynthetic characteristics of a dominant plant species in a typical grassland to changes in precipitation. Rain shelter technology was used to simulate 50%, 100%, and 150% of natural rainfall. The photosynthetic rate (Pn), intercellular CO2 concentration (Ci), transpiration rate (Tr), stomatal conductance (Gs), and ecological stoichiometry of the rhizosphere soil and Stipa bungeana at different growth stages were measured in May, July), and September, 2019 after 2 years of rainfall control. The results showed that the aboveground carbon (C) content of plants grown under 150% precipitation was significantly higher than that of plants grown under 100% precipitation in September. The aboveground nitrogen (N) content of plants under 50% precipitation was significantly higher than the plants grown under 100% precipitation. Under all different precipitation treatments, the aboveground C:N ratio was the lowest (16.4–19.6) in May. The range of average aboveground C: phosphorous (P) ratio was 373.7–617.8, and the N:P ratio in the descending order was July &gt; May &gt; September. The 50% precipitation treatment promoted the highest accumulation of underground C at all the growth stages. The productivity of the grassland under the 100% and 150% precipitation treatments was limited by the rhizosphere soil N and P. The underground C, P, C:P, and aboveground C:N ratios were sensitive indicators. Aboveground and underground N:P ratio showed the strongest significant correlation (P &lt; 0.001), and the correlation between underground stoichiometry and rhizosphere soil P (P &lt; 0.001) was stronger than that with rhizosphere soil N (P &lt; 0.05). The correlation between Ci and stoichiometry was opposite in direction to the correlation between Pn, Tr, Gs, and stoichiometry. The research results will provide a scientific reference for understanding of the material cycle and judgment of vegetation nutrient limitations in the Loess Plateau.

Short-term N addition in a Pinus tabuliformis plantation: Microbial community composition and interactions show different linkages with ecological stoichiometry

Increasing nitrogen (N) deposition severely impacts terrestrial biogeochemical cycles by altering the stoichiometry of ecological components. Although microbes are known to play an important role in biogeochemical cycles, the mechanisms how soil microbes drive nutrient cycling remain elusive under N deposition. Therefore, we investigated changes in microbial community diversity, composition, and interactions, and elucidated the relationship among microbial community responses, soil available nutrients, and ecological stoichiometry resulting from two years of N addition to a Pinus tabuliformis plantation on the Loess Plateau at four rates of N addition (0 (N0), 3.0 (N3), 6.0 (N6), and 9.0 (N9) g N m−2 y−1). N addition significantly influenced microbial composition, decreasing the relative abundance of Acidobacteria and Basidiomycota along N addition gradients and increasing the relative abundance of Ascomycota from N3 to N9. Along N addition gradients except N3, bacterial interactions increased from 62.70% to 73.38%, whereas interactions between bacterial and fungal communities decreased from 34.44% to 24.43%. Among all microbial interactions, the positive ones accounted for a larger proportion (over 55%), indicating a predominance of mutualism under all N addition treatments. Changes in the microbial composition were correlated with soil resource stoichiometry factors, including soil organic carbon: soil total N (SOC:TN) and SOC: soil total phosphorus (SOC:TP), whereas the topological network features were correlated with ammonium N (NH4+-N), nitrate N (NO3−-N), β-1,4-N-acetylglucosaminidase (NAG), alkaline phosphatase (AP), and eco-enzymatic stoichiometry. Therefore, the soil variables that caused changes to microbial composition and interactions were different. In this sense, microbial community compositions were more easily affected by soil resource stoichiometry, whereas microbial interactions were more easily affected by soil available nutrients. In addition, changes to microbial interactions could mediate microbial metabolism via eco-enzyme expression.