Nitrogen-phosphorus Ratio Research Articles

Nutrition addition alleviates negative drought effects on Quercus acutissima seedlings

Changing precipitation patterns have exacerbated severe drought events, causing tree die-off and forest mortality. Nutrition addition, as a critical method for forest management, may alleviate negative drought effects. Therefore, we set up a two-factor orthogonal experiment to study the responses of the leaf structural traits of Quercus acutissima to nutrition addition under drought stress. Leaf structural traits, including leaf morphological traits, leaf mass, and leaf nutrition traits, were measured under nine water and nutrition addition treatments. Two-way analysis of variance was used to detect the main effect and interaction of water and nutrition addition on leaf structural traits, principal component analysis was used to screen key traits. Our results show that drought had a unique and decisive effect on leaf length, leaf width, and leaf center, while leaf thickness only depended on nutrition addition. Conversely, no treatments changed the leaf length-width ratio and leaf nitrogen-phosphorus ratio. Besides, nutrition addition alleviated negative drought effects on leaf area, leaf saturated mass, leaf dry mass, leaf nitrogen content, leaf phosphorus content, leaf volume, specific leaf area, and leaf dry-matter content. According to the principal component 1 (54.83%), we screened seven key traits from leaf structural traits, including leaf area, leaf saturated mass, leaf dry mass, leaf nitrogen content, leaf volume, specific leaf area, and leaf dry-matter content, to effectively capture changes in leaf structural traits. Our results demonstrate that under drought stress, nutrition addition enhanced soil nutrition availability, increased leaf nitrogen and leaf phosphorus content, and finally alleviated negative drought effects. Thus, nutrition addition is crucial for plants to get through drought and for forest ecological restoration under global climate change.

Alpha and beta diversity of functional traits in subtropical evergreen broad-leaved secondary forest communities.

Intra-speciic variation is the main source of functional trait diversity and has similar ecological effects as inter-speciic variation. We studied 79 species and 3546 individuals from 50 ixed monitoring plots in subtropical evergreen broad - leaved secondary forests in Zhejiang Province, China. Using trait gradient analysis, we examined nine traits (speciic leaf area, leaf dry matter content, wood density, leaf area, chlorophyll content, leaf nitrogen content, leaf phosphorus content, leaf potassium content, and nitrogen-phosphorus ratio) by decomposing species functional traits into alpha (within-community) and beta (among-communities) measure the impact of environmental gradients and the presence of other species on the variation of traits. All nine functional traits showed some degree of differentiation in the forest communities, with a greater range of variation in alpha values than in beta values . Correlations were signiicantly different between the trait differences in the communities. The alpha values of each trait showed a higher correlation with other components than the beta values. The factors affecting intra-speciic trait variation were relatively complex. The alpha component had a more signiicant and stronger effect on intra-speciic trait variation compared to the beta component. Abiotic factors, such as soil nutrient content, soil nitrogen-phosphorus content, directly affected the beta component. In contrast, biotic factors, such as tree height variation, had a direct and stronger effect on the alpha component. Our results demonstrate that alpha and beta components, as independent differentiation axes among coexisting species, have different sensitivities to different environmental factors and traits in different ecological strategies and spatial scales. Trait gradient analysis can more clearly reveal the variation patterns of species traits in communities, which will help to understand the scale effects and potential mechanisms of trait relationships.

Influence of surface water and groundwater on functional traits and trade-off strategies of oasis communities at the end of the Keriya River, China.

Plant functional traits reflect the capacity of plants to adapt to their environment and the underlying optimization mechanisms. However, few studies have investigated trade-off strategies for functional traits in desert-wetland ecosystems, the mechanisms by which surface water disturbance and groundwater depth drive functional trait variation at the community scale, and the roles of intraspecific and interspecific variation. Therefore, this study analyzed specific differences in community-weighted mean traits among habitat types and obtained the relative contribution of intraspecific and interspecific variation by decomposing community-weighted mean traits, focusing on the Daliyabuyi Oasis in the hinterland of the Taklamakan Desert. We also explored the mechanisms by which surface water and groundwater influence different sources of variability specifically. The results showed that plant height, relative chlorophyll content, leaf thickness, leaf nitrogen content, and nitrogen-phosphorus ratio were the key traits reflecting habitat differences. As the groundwater depth becomes shallower and surface water disturbance intensifies, plant communities tend to have higher leaf nitrogen content, nitrogen-phosphorus ratio, and relative chlorophyll content and lower height. Surface water, groundwater, soil water content, and total soil nitrogen can influence interspecific and intraspecific variation in these traits through direct and indirect effects. As arid to wet habitats change, plant trade-off strategies for resources will shift from conservative to acquisitive. The study concluded that community functional traits are mainly contributed by interspecific variation, but consideration of intraspecific variation and the covariation effects that exist between it and interspecific variation can help to further enhance the understanding of the response of community traits in desert-wetland ecosystems to environmental change. Surface water disturbance has a non-negligible contribution to this adaptation process and plays a higher role than groundwater depth.

Effects of Dredging on Nitrogen and Phosphorus Storage Patterns and Retention Mechanisms in Column Core Sediments in the Caohai Region of Dianchi Lake

Dredging is a common technique for managing eutrophication problems in waters, reducing the accumulation of pollutants by removing sediments from the bottom of water bodies. However, dredging can have complex impacts on lake ecosystems, and it is crucial to understand its benefits and mechanisms for the environment. In this paper, the dredged and undredged areas in the Caohai portion of Dianchi Lake were studied to analyze the effects of dredging on nitrogen–phosphorus transport and conversion and changes in nitrogen–phosphorus morphology content and its mechanisms by comparing the nitrogen–phosphorus morphology content and percentage, the nitrogen–phosphorus ratio, and the release contribution of the two areas. It was found that the ratio of stabilized nitrogen (SN) to stabilized phosphorus (SP) in the dredged area was lower than that in the undredged area and the BD-P and TOC content had a large turnaround at the 16–20 cm position of the sediment in the dredged area. The main conclusions were that the dredging would disrupt the internal equilibrium of the lake system for many years, with the greatest effect on the balance of the BD-P in the phosphorus forms of the sediment, and that the column cores of the dredged area at 0 to 16 cm might be newly accumulated sediments after the dredging project. However, with time, the distribution of nitrogen and phosphorus forms in the newly accumulated sediments will gradually reach a new equilibrium. In addition, dredging will also cause significant changes in the retention efficiency of nitrogen and phosphorus in the sediment, and the stable nitrogen and phosphorus forms will be released and transformed into unstable nitrogen and phosphorus forms.

Model of nitrogen-phosphorus ratio and phytoplankton relationship in lake Laut Tawar, Indonesia

Phytoplankton blooms in the lake cause ecological, economic, health, energy, and aesthetic losses. It reduces water quality and biota diversity, creates toxins in the waters, and changes the structures and functions of the ecosystem. The essential nutrients for the growth of phytoplankton are nitrogen and phosphorus. Controlling phytoplankton growth can be managed by controlling the limiting nutrient input. This study aims to identify the limiting nutrient, analyze variations in TN:TP ratio spatially and temporally, and model TN:TP ratio and chlorophyll-a relationship. This study used secondary data from previous studies, namely TN, TP, and chlorophyll-a observed monthly in seven stations purposively during a year. Rainfall data was also obtained from the previous study. Limiting nutrients were determined by Redfield theory, and data were analyzed by Spearman correlation, One-way ANOVA, Kruskal-Wallis, and regression analysis. The results showed phosphorus was a limiting nutrient for phytoplankton growth in Lake Laut Tawar. TN:TP ratio and chlorophyll-a did not vary spatially, indicating the lake surface waters were evenly mixed. The parameters varied temporally, expressing the influence of hydroclimatological factors, especially rainfall. Rainfall increases nutrient input to the lake, but only rain below 200 mm/month causes an increase in the concentration of nutrients in the lake. The rainfall above 200 mm/month increases lake water volume significantly, thereby reducing nutrient concentrations. TN:TP ratio and chlorophyll-a related negatively and formed a non-linear relationship with an empirical model Chlorophyll-a = 2770.285 (TN/TP)-1.871. Eutrophication of Lake Laut Tawar should be anticipated by controlling the anthropogenic phosphorus input.Keywords:AnthropogenicChlorophyll-aEutrophication,Limiting nutrientRainfall

Effect of water stratification and mixing on phytoplankton functional groups: a case study of Xikeng Reservoir, China

A shift in reservoir stratification and mixing significantly affects the water column ecosystem, which in turn leads to changes in phytoplankton abundance and community structure. To explore the effects of stratification and mixing on the phytoplankton community structure of a diversion reservoir, a 1-year survey was divided into a stratification period in 2020, a mixing period in 2020, and a stratification period in 2021, and redundancy analysis (RDA), variance partitioning analysis (VPA) and Pearson correlation analysis were used to analyse the key drivers affecting the phytoplankton functional groups, using Xikeng Reservoir as a case study. During the study period, 8 phyla, 69 genera and 9 major functional groups were observed in this reservoir. The dominant functional groups varied significantly, being X1 in the stratified period in 2020; P and D in the mixing period in 2020; and D, X1, and M in the stratified period in 2021. The phytoplankton diversity index was greater in the mixing period than in the stratification period, in agreement with the results of the aquatic ecological status evaluation (Q index, higher in the mixing period than in the stratification period). However, phytoplankton diversity of Xikeng Reservoir was of limited value in assessing the degree of water pollution, so should be considered in combination with the Q index. Water temperature (WT), mixing depth (Zmix), nitrogen–phosphorus ratio (N/P), and total nitrogen (TN) were important drivers of phytoplankton functional group dynamics in different periods. The study provides a valuable reference for assessing the relationship between environmental factors and phytoplankton communities, as well as for the evaluation and conservation of aquatic ecosystems in southern China's water diversion reservoirs.

Assessment of Eutrophication Characteristics and Evaluation of the First-Generation Eutrophication Model in the Nearshore Waters of Shantou City

Based on the water quality monitoring results from 2002 to 2018 in the coastal waters of Shantou City, this study used eight methods, including the single-factor index method, eutrophication index method, nutrient status quality method, comprehensive index method, organic pollution index method, nitrogen–phosphorus ratio method, potential eutrophication evaluation, and dissolved oxygen saturation parameter method, to evaluate the eutrophication and organic pollution status of the area. The applicability of the first-generation eutrophication model was assessed from the perspective of red tide occurrence, and a comparison was made among the various evaluation methods. The results indicate that the coastal waters of the study area were mostly in a phosphorus-limited state, with a few periods of nutrient deficiency and a very small portion of time in a moderately nutritious state with both nitrogen and phosphorus limitations. The overall N/P ratio showed an increasing trend primarily due to the gradual increase in inorganic nitrogen content. In terms of evaluating eutrophication based on red tide symptoms, the comprehensive index method showed better performance in reflecting eutrophication conditions, while the eutrophication index method and dissolved oxygen saturation parameter method highlighted problematic areas but often exaggerated their extent. The nutrient status quality method and organic pollution index method did not provide distinctive indications and could not verify red tide symptoms. The nitrogen–phosphorus ratio method and potential eutrophication evaluation could reflect certain nutrient structures and eutrophication characteristics but also failed to verify red tide symptoms. Furthermore, this study found a certain correlation between the occurrence of red tide and the ratio of nitrate nitrogen to ammonia nitrogen, which consistently ranged from 1.15 to 1.94 during red tide events. Therefore, whether this ratio can serve as a characteristic value for red tide occurrence and be used for early warning and monitoring still requires further validation.

Characteristics of Soil Carbon, Nitrogen, Phosphorus, and Ecological Stoichiometry in Vegetable Fields and Orchard in the Coastal Area of Fuzhou

The soil ecological stoichiometric characteristics of different agricultural land use types have a certain indicator function for characterizing the level of soil nutrient supply and are of great significance to the management of nutrient resources in farmland ecosystems. In order to reveal the soil carbon (C), nitrogen (N), and phosphorus (P) contents and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land use types, this study took vegetable fields (taro field and jicama field) and orchards (citrus tree orchard, watermelon field, and pear tree orchard) as the research objects in the coastal area of Fuzhou City. The contents of soil C, N, and P and their ecological stoichiometric characteristics in different vegetable fields and orchard agricultural land uses were measured and analyzed. The soil C and N contents were in the order of orchard>vegetable field (P<0.05). The C content in the citrus tree orchard was the highest (4.44 g·kg-1), and the N content in the watermelon field was the highest (1.46 g·kg-1). The soil P content was vegetable field>orchard (P<0.05), and the jicama field had the highest P content (0.19 g·kg-1). The soil carbon and nitrogen ratio (C/N), carbon and phosphorus ratio (C/P), and nitrogen and phosphorus ratio (N/P) were orchard>vegetable field (P<0.05). Among them, the citrus tree orchard had the highest C/N (7.40) and C/P (61.43), and the watermelon field had the highest N/P (10.27). Soil N content was significantly and negatively correlated with bulk density and conductivity (r=-0.49, r=-0.28, P<0.05), and there was a significant and positive correlation with soil water content (r=0.61, P<0.05). C/P and C/N were significantly and positively correlated with SOM (r=0.71, r=0.64, P<0.01). In the process of crop planting and management in the coastal area of Fuzhou City, it is necessary to reasonably add nitrogen fertilizer to compensate for the N limitation, and slow-release nitrogen fertilizer is better for promoting the sustainable supply of nitrogen nutrients in the growth and development of crops.

The influencing factors of leaf functional traits variation of Pinus densiflora Sieb. et Zucc.

Trait-based approaches have emerged as promising strategies for understanding plant adaptation mechanisms to the changing environment. At present, there are a large number of studies on the relationship between plant leaf functional traits and environment, but these studies mostly use the average value of traits instead of species, ignoring the intraspecific changes of traits. Pinus densiflora Sieb. et Zucc. is not only an urban greening tree species, but also an important afforestation tree species, which plays an important role in China's terrestrial ecosystem. In this study, the leaf nitrogen content (LN), the leaf phosphorus content (LP), nitrogen phosphorus ratio (N/P), leaf area (LA) and specific leaf area (SLA) of 16 sites (160 records) distributed in Chinese P. densiflora were measured. (1) The results showed that LN increased with the increase of mean annual precipitation (MAP) and decreased with the increase of soil organic matter (SOM). LP and SLA decreased with the increase of mean annual temperature (MAT) and increased with the increase of AN (soil available phosphorus) and AP (soil available phosphorus). N/P increased with the increase of MAT and MAP, and decreased with the increase of AN and AP. LA increased with the increase of MAT and MAP. (2) Relative importance analysis showed that MAP was the most important driver of LN and LA. The main driving factors of LP is MAT, the main driving factors of N/P is SOM, and the main influencing factors of SLA is AP. Overall, climate was the main driving factor for the variation of leaf functional traits. The variation law of leaf functional traits along environmental gradient strongly supported the temperature-plant physiological hypothesis. It enriches the understanding of leaf functional traits distribution pattern and its driving mechanism under environmental change.

An electricity-generating bacterium separated from oil sludge microbial fuel cells and its environmental adaptability.

Electricity-generating bacteria as biocatalysts for microbial fuel cells (MFCs), their species, and power generation performance determine the pollution control and power generation performance of MFCs. And there are few studies on the types and performance of electricity-generating bacteria isolated from oily sludge microbial fuel cells. For improving the power generation performance of oily sludge MFCs, an electricity-generating bacterium was isolated from the oily sludge. More importantly, the adaptability of nitrogen to phosphorus ratio, temperature, and pH of the electricity-generating bacteria were adjusted by a controlled variable method. The results of this study showed that the electricity-generating bacterium was identified as Bacillus cereus, with a rod-shaped cell, about 0.5-1.0μm in length. The optimal nitrogen-phosphorus ratio, temperature, and pH of MFCs were 4.67:1, 25 ℃, and pH = 7, respectively. Its maximum power density, COD, and oil removal rate was up to 65 mW·m-3, 90.51%, and 87.76%, respectively. The study of this functional bacterium will provide beneficial assistance for the improvement of oil removal and power generation performance of oily sludge MFCs.

Performance and mechanism of Chlorella in swine wastewater treatment: Roles of nitrogen-phosphorus ratio adjustment and indigenous bacteria

The effects of adjusting the nitrogen-phosphorus (N/P) ratio of wastewater and indigenous bacteria on swine wastewater treatment by Chlorella sp. HL were investigated. The optimal N/P ratio of Chlorella in swine wastewater was 20 by adjusting the phosphorus concentration. The participation of indigenous bacteria increased total extracellular polymeric substances content, which was beneficial to maintain the stability of the algal-bacterial consortium, and improved the algal density and the removal rate of total nitrogen, total phosphorus, and chemical oxygen demand by 47.8%, 24.0%, 30.7%, and 326.7%, respectively. Proteobacteria was the dominant phylum with the relative abundance of 71.58% in the algal-bacterial system at optimal N/P ratio, and Brevundimonas, Chryseobacterium, and Pseudomonas played positive roles in the establishment of symbiotic systems at the genus level. These results provide a theoretical basis for the construction of an efficient algal-bacterial symbiotic system in swine wastewater treatment and support for commercial scale-up.

Increasing the hydrophyte removal rate of dissolved inorganic phosphorus using a novel Fe-Mg-loaded activated carbon hydroponic substrate with adsorption-release dual functions

At present, the plant floating bed is mostly used to remediate aquaculture tail water since its obvious advantage of eco-friendly. However, there is still the problem of low phosphorus removal efficiency due to the balance between the floating bed coverage area and the aquaculture area, as well as the phosphorus content fluctuation in water. To solve this problem, a phosphorus-controlling hydroponic substrate prepared from granular activated carbon loaded with nanoiron-magnesium hydroxide (AC-Fe-Mg) was prepared, and the phosphorus adsorption and slow-release performance of AC-Fe-Mg were evaluated. Moreover, the effect of the combination of AC-Fe-Mg and I. pseudacorus L. on phosphorus purification was studied. AC-Fe-Mg exhibited superior adsorption and release ability for phosphorus without substantial interference from coexisting substances such as Cl−, NO3−, HCO3− and humic acid (HA) within the pH range of 5–9. Finally, the phosphorus removal rate reached 98.66% under the combined effect of I. pseudacorus L. and AC-Fe-Mg at the initial P concentration of 20 mg L−1. At a high P-level, phosphorus was sequestered by AC-Fe-Mg and consumed as a growth nutrient by I. pseudacorus L. At a low P-level, phosphorus was released from AC-Fe-Mg and provided to I. pseudacorus L. The regulatory ability of AC-Fe-Mg can provide plants with continuous and stable phosphorus, and maintain the nitrogen-phosphorus ratio for plant demand. Thus, the dissolved inorganic phosphorus was controlled and efficiently removed. Accordingly, the novel AC-Fe-Mg with adsorption and slow-release dual functions can be used as a hydroponic substrate of emergent plants to improve water purification.

Effects of regulation measure on soil and microbial biomass of moderately degraded alpine meadow in Qilian Mountain, China

We examined the effects of different regulation measures (spring rest grazing, spring rest grazing-cutting turf, spring rest grazing-cutting turf-fertilization, spring rest grazing-cutting turf-sowing, spring rest grazing-cutting turf-fertilization-sowing) on vegetation, soil physical and chemical properties, and soil microbial biomass in mode-rately degraded alpine meadow in Qilian Mountain. The results showed that all the regulation measures significantly increased plant coverage and aboveground and underground biomass of degraded alpine meadows. Plant species richness increased significantly under the two measures of spring rest grazing-cutting turf-fertilization and spring rest grazing-cutting turf-fertilization-sowing. The dominant species of spring rest grazing-cutting turf-sowing and spring rest grazing-cutting turf-fertilization-sowing was Poa pratensis cv. Qinghai. Soil pH and bulk density in moderately degraded alpine meadow (control) were significantly higher than those of all regulation measures. Soil water content, soil organic carbon, total nitrogen and total potassium, carbon-nitrogen ratio and nitrogen-phosphorus ratio of spring rest grazing-cutting turf-fertilization-sowing measures were the highest, which were 21.3%, 22.30 g·kg-1, 2.77 g·kg-1, 19.93 g·kg-1, 8.3 and 3.5, respectively. Soil microbial biomass nitrogen and phosphorus (104.98 and 40.74 mg·kg-1) of degraded meadows under spring rest grazing-cutting turf-fertilization-sowing measures were significantly higher than those of other measures, while soil microbial biomass carbon (240.72 mg·kg-1) of degraded meadows under spring rest grazing-cutting turf-fertilization measures was significantly higher than that of other measures. The results of radar map showed that the regulation measures affected the characteristics of degra-ded meadow vegetation (aboveground and underground biomass), soil physical and chemical properties (water content, organic carbon, total nitrogen, total phosphorus, and total potassium) and soil microbial biomass (carbon, nitrogen and phosphorus). Spring rest grazing-cutting turf-fertilization-sowing measures had the best performance in restoraing degraded meadows in the study area.

不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究 DOI: 10.5846/stxb202009172425 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2017YFC0505003） Relationships between competition intensity and leaf phenotypic plasticity of woody plants in subalpine forests on different slope directions Author: Affiliation: Fund Project: 2017YFC0505003 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:表型可塑性是植物生长响应外界环境变化的重要表现形式，体现了植物个体在环境胁迫下的适合度。但是关于植物表型可塑性的驱动机制仍然存在很多争议。为了探讨植物表型可塑性的影响因素，以四川省阿坝藏族羌族自治州位于同一海拔梯度但坡向相反的天然次生林为研究对象，分析了不同坡向竞争强度与10种树木叶片功能性状表型可塑性的关系的差异。研究发现：（1）研究样地中阴坡水分和养分资源优于阳坡；（2）阴坡上林木平均种内和种间竞争强度高于阳坡，阴坡上林木种内竞争强度随着树木个体大小的增加而显著性减少，阳坡上林木种内竞争强度却随着个体大小的增加而增加；（3）阴坡上叶片表型可塑性高于阳坡，表型可塑性随着个体大小的增加而增加，在阳坡上却随着个体大小增加而降低。这些结果表明阴坡上水分等资源环境条件优于阳坡，林木生长受到环境资源限制较少。在林木生长过程中，较高的竞争强度引起的资源重叠加剧，尤其是种内竞争强度的变化，从而导致了阴坡上较高的叶片表型可塑性。因为较高的竞争强度，随着林木个体大小的增加，树木需要更高的可塑性赢得竞争优势来获取更多的资源支持生长。但是在阳坡上，资源相对缺乏，环境资源对树木生长的限制降低了叶片表型的可塑性，因为环境资源的限制，随着树木个体大小的增加越容易受到资源限制的影响，因此阳坡上表型可塑性随着个体大小的增加而降低。研究说明，阴坡上叶片表型可塑性主要受到竞争强度的影响，而阳坡上则主要受环境资源的限制。 Abstract:Phenotypic plasticity is an indicator of the responses of plant growth and development to environmental changes, which reflects the fitness of plant individuals under environmental stress. However, the driving mechanism of plant phenotypic plasticity is still controversial. To explore the impacts of environmental conditions and competition on the phenotypic plasticity of leaf traits in trees, we surveyed two secondary forests with different slope directions in the Ngawa (Aba) Tibetan and Qiang Autonomous Prefecture in western Sichuan, China and analyzed the difference in the relationship between competition intensity and phenotypic plasticity of 10 tree species leaf functional traits between shade and sunny slopes. Results show that:(1) water and nutrient availabilities were greater on shade slope than those on sunny slope. (2) Mean intraspecific and interspecific competitions of tree species on shade slope were higher than those on sunny slope; intraspecific competition intensity decreased with the increases of individual tree size on shade slope, but it increased along with the increase of individual size on sunny slope. (3) The leaf traits include specific leaf area (SLA), leaf carbon content (C), leaf nitrogen content (N), leaf phosphorus content (P), leaf kalium content (K), leaf carbon-phosphorus ratio (CPR), leaf carbon-nitrogen ratio (CNR), and leaf nitrogen-phosphorus ratio (NPR). Phenotypic plasticity of all eight measured leaf traits on shade slope was higher than on sunny slope. Phenotypic plasticity of leaf traits increased with the increase of individual tree size on shade slope, but decreased with the increase of individual size on sunny slope. These findings suggest that the environmental resources of community on shade slope were greater than on sunny slope. The growth of forest trees was less restricted by the availability of environmental resources on shade slope, where higher competition intensity led to the intensification of resource overlap, especially the high intraspecific competition intensity, ultimately resulted in the higher phenotypic plasticity of leaf traits on shade slope. Because of higher competition intensity, with the increase of individual size, trees need higher phenotypic plasticity to gain competitive advantage and obtain more resources to support growth. However, because resources were relatively poor, the limitation of the availability of environmental resources reduced to the lower phenotypic plasticity of leave traits on sunny slope. Due to the limitation of the availability of environmental resources, with the increase of individual size, trees were more likely to suffer resource constraints. Therefore, phenotypic plasticity of leaf traits on sunny slope decreased with the increase of tree individual size. To summary, our study demonstrated that leaf phenotypic plasticity was mainly affected by competition intensity on the shade slope, while it was mainly limited by the availability of environmental resources on the sunny slope. 参考文献 相似文献 引证文献

Bioaugmentation and biostimulation of crude oil contaminated soil: Process parameters influence

In this study, investigation of bioaugmentation and biostimulation process parameters’ influence on biodegradation effectiveness of bacteria isolates in a crude oil polluted soil for 60 days was conducted. A native environment of crude oil polluted site was considered for bacteria isolation. Dilution plate technique was used for bacteria culturing under laboratory conditions. Central composite design embedded in design expert software was used for the design of experiment and optimum point prediction. The influence of nitrogen:phosphorus nutrient ratio and bacteria concentration at varying crude oil concentration and soil pH on percentage of total petroleum hydrocarbons (TPH) biodegraded was investigated. Biostimulation was highly significant on the percentage of TPH biodegraded as revealed by experimental results. Degradation efficiency of 93.75% was obtained for a soil pH of 10 contaminated with 100 g/Kg of crude oil using 600 cell/g of bacteria supplemented with 8 g/g of nitrogen-phosphorus ratio. The model developed was effective for future prediction with better correlation between experimental and predicted values. A biodegradation efficiency of 77.42% was achievable at the optimum predicted point by central composite design. Hydrocarbons biodegradation in the crude oil contaminated soil via the action of supplemented bacteria isolates was revealed. Conclusively, bacteria isolates from native polluted site could be applied as effective scavenger for hydrocarbons in crude oil contaminated soil.

Optimization and characterization of crude oil contaminated soil bioremediation using bacteria isolates:Plant growth effect

This study investigated the effect of soil pH, nitrogen-phosphorus ratio, crude oil concentration and bacteria isolates (from petroleum hydrocarbon-contaminated soil) concentration on the optimization of crude oil-contaminated soil bioremediation using central composite design. The responses were total petroleum hydrocarbons (TPH) and plant growth. A 60-day pot experiment was conducted. Natural soil, crude oil-contaminated soil and bioremediated soil were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), carbon-hydrogen-nitrogen (CHN) analyser and gas chromatograph-mass spectroscopy (GC–MS). Optimum predicted values were 4.69, 7.68 g/g, 250.05 mL/L and 568.35 cell/g for soil pH, nitrogen-phosphorus ratio, crude oil concentration and bacteria isolates concentration respectively. Experimental run at optimum point affirmed the accuracy of the developed models. Characterization revealed contamination of natural soil by hydrocarbons and their biodegradation via the action of active functional groups present in bacteria isolates. Conclusively, the bacteria isolates could be applied as effective scavenger for hydrocarbon biodegradation in crude oil contaminated soil.

Soil Nutrient and Vegetation Diversity Patterns of Alpine Wetlands on the Qinghai-Tibetan Plateau

To predict the consequences of environmental change on the biodiversity of alpine wetlands, it is necessary to understand the relationship between soil properties and vegetation biodiversity. In this study, we investigated spatial patterns of aboveground vegetation biomass, cover, species diversity, and their relationships with soil properties in the alpine wetlands of the Gannan Tibetan Autonomous Prefecture of on the Qinghai-Tibetan Plateau, China. Furthermore, the relative contribution of soil properties to vegetation biomass, cover, and species diversity were compared using principal component analysis and multiple regression analysis. Generally, the relationship between plant biomass, coverage, diversity, and soil nutrients was linear or unimodal. Soil pH, bulk density and organic carbon were also significantly correlated to plant diversity. The soil attributes differed in their relative contribution to changes in plant productivity and diversity. pH had the highest contribution to vegetation biomass and species richness, while total nitrogen was the highest contributor to vegetation cover and nitrogen–phosphorus ratio (N:P) was the highest contributor to diversity. Both vegetation productivity and diversity were closely related to soil properties, and soil pH and the N:P ratio play particularly important roles in wetland vegetation biomass, cover, and diversity.

No-linear dynamics of lake ecosystem in responding to changes of nutrient regimes and climate factors: Case study on Dianchi and Erhai lakes, China

As different algae growths responding to a set of nutrients can occur under different conditions, the nutrient load management based on the relationship between chlorophyll a (Chla) and total phosphorus (TP) alone may not always effective for lake algae bloom control. It is not clear whether the lagged response of algae to reduced nutrients related to the utilization efficiency of algae to phosphorus (UEAP), and how UEAP could response to climate and water quality factors. Here we analyzed over 20 years monitoring data in two lakes with similar geology but different nutrient levels by using statistical and modeling methods. The aim was to reveal the impact of UEAP on lake algae dynamics and the driving factors of UEAP changes. The results showed that UEAP is one of the key factors affecting algae dynamics, the incorporation UEAP and its driving factors achieved greater modeling reliability. UEAP, Nitrogen phosphorus ratio (NPr) was the key driving factor in Dianchi Lake, while total nitrogen (TN) and air temperature (AT) were the key driving factors in Erhai Lake. The changes of nutrients and climate drove UEAP into the paralysis or sensitive phase depending on lake specific factors and conditions. This correlated to algae density dynamics, in particular to those characteristic of algae growth thresholds. The future trend of climate change will continue to promote the increase of UEAP in both lakes, but severer in Erhai Lake. The key finding here is of the value of a proxy index (UEAP) for phosphorus utilization was associated with the lagged response of algae to nutrient reduction. We demonstrated the related modeling procedures with two-function variable (UEAP) of both prediction and response can predict the trend of algae growth and determine the states of the lake ecosystem. Hence, the approaches are of great value for lake management policy making.

Fungal Diversity and Community Assembly of Ectomycorrhizal Fungi Associated With Five Pine Species in Inner Mongolia, China.

Ectomycorrhizal (EM) fungi play vital roles in ensuring host plants’ health, plant diversity, and the functionality of the ecosystem. However, EM fungal diversity, community composition, and underlying assembly processes in Inner Mongolia, China, where forests are typically semiarid and cold-temperate zones, attract less attention. In this study, we investigated EM fungal communities from 63 root samples of five common pine plants in Inner Mongolia across 1,900 km using Illumina Miseq sequencing of the fungal internal transcribed spacer 2 region. We evaluated the impact of host plant phylogeny, soil, climatic, and spatial variables on EM fungal diversity and community turnover. Deterministic vs. stochastic processes for EM fungal community assembly were quantified using β-nearest taxon index scores. In total, we identified 288 EM fungal operational taxonomic units (OTUs) belonging to 31 lineages, of which the most abundant lineages were Tomentella–Thelephora, Wilcoxina, Tricholoma, and Suillus–Rhizopogon. Variations in EM fungal OTU richness and community composition were significantly predicted by host phylogeny, soil (total nitrogen, phosphorus, nitrogen–phosphorus ratio, and magnesium), climate, and spatial distance, with the host plant being the most important factor. β-nearest taxon index demonstrated that both deterministic and stochastic processes jointly determined the community assembly of EM fungi, with the predominance of stochastic processes. At the Saihanwula site selected for preference analysis, all plant species (100%) presented significant preferences for EM fungi, 54% of abundant EM fungal OTUs showed significant preferences for host plants, and 26% of pairs of plant species and abundant fungal OTUs exhibited remarkably strong preferences. Overall, we inferred that the high diversity and distinctive community composition of EM fungi associated with natural pine species in Inner Mongolia and the stochastic processes prevailed in determining the community assembly of EM fungi. Our study shed light on the diversity and community assembly of EM fungi associated with common pine species in semiarid and cold temperate forests in Inner Mongolia, China, for the first time and provided a better understanding of the ecological processes underlying the community assembly of mutualistic fungi.

Effects of Precipitation Changes on Plant Community Diversity and Soil C:N:P Ecological Stoichiometric Characteristics in a Desert Steppe of China

Studying the influence of precipitation patterns on plant community diversity, soil C:N:P ecological stoichiometric characteristics, and the relationships between key soil factors and plant community diversity is of great significance for the protection of plant community diversity in desert grasslands. This paper was studied in the desert steppe of the west of Loess Plateau using a three-year precipitation manipulation experiment (40% reduction in precipitation, 20% reduction in precipitation, natural precipitation, 20% increase in precipitation, and 40% increase in precipitation), explored the influence of changes in precipitation in dry and wet years on the diversity of plant community and soil C:N:P ecological stoichiometric characteristics. And we also explored the relationship between soil C:N:P ecological stoichiometric characteristics and the key soil factors and the diversity of plant community under changes in precipitation. The results showed that in a normal year and the drier year (2013 and 2015), Patrick richness and Shannon-Wiener diversity index were significantly low under the 20% reduction treatment compared with the control and 40% increase treatments, respectively. During the wetter year, Patrick richness and Shannon-Wiener diversity index were no different between any of the precipitation treatments. In the normal year and the drier year, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and the carbon-nitrogen ratio (C:N), carbon-phosphorus ratio (C:P), and nitrogen-phosphorus ratio (N:P) all decreased with an increase in precipitation (the decrease in the C:N ratio was statistically significant). During the wetter year, SOC, TN, C:P, and N:P increased with an increase in precipitation. During the normal year, precipitation treatments had no significant influence on soil water content, having a limited influence on the plant community. TN, N:P, SOC, C:N, and microbial biomass nitrogen (MBN) had a more prominent influence on plant community diversity. In the wetter year, precipitation was abundant leading to a rise in soil nutrients. Water was not the most important factor limiting to plant growth whereas soil water content, soil nutrients, and ecological stoichiometric characteristics jointly regulate plant community diversity. In the drier years, precipitation treatments had a significant impact on soil water content, whereby an increase in precipitation led to high losses of soil nutrients. Therefore, soil water content was the most important factor affecting plant community diversity during drier years. These observations indicate that under dry and wet years, plant community diversity and soil C:N:P ecological stoichiometric characteristics have variable responses to precipitation and soil C:N:P effect on plant community were also different. These results provide a theoretical basis for the protection and management of desert steppe systems under future projected changes in precipitation.