Global Nitrogen Deposition Research Articles

Cascading impacts of nitrogen deposition on soil microbiome and herbivore communities in desert steppes

Human activities in the last century have intensified global nitrogen deposition, resulting in the degradation of ecosystem function and loss of biodiversity worldwide. Nitrogen addition is a crucial method for examining the effects of atmospheric nitrogen deposition on species composition and structure of soil microbiome and biotic community, as exogenous nitrogen inputs can trigger cascading effects on ecosystem functions. In a 6-year experiment, we evaluated the impact of nitrogen addition on soil microbial-plant-insect systems in desert steppes. Our results show that nitrogen addition significantly altered soil microbial composition and ecological function, leading to a decrease in nitrogen-fixing bacteria and an increase in saprophytic fungi. High levels of nitrogen addition increased total plant biomass while decreasing species diversity. Additionally, high nitrogen addition levels suppressed below-ground biomass of gramineae and legumes compared to low nitrogen addition. Nitrogen addition also increased herbivore abundance by altering insect community structure, particularly benefiting chewing pests over sucking pests, thus heightening the risk of biological disasters through trophic cascading effects. Consequently, excessive nitrogen addition may destabilize desert steppe ecosystems by disturbing soil microbial-plant-insect interactions, hindering the maintenance of biotic community diversity and steppe productivity.

Heavy Nitrogen Application Rate and Long-Term Duration Decrease the Soil Organic Carbon and Nitrogen Sequestration Rates in Forest Ecosystems

Nitrogen addition alters soil organic carbon (SOC) and total nitrogen (TN) accumulation in forest ecosystems, but the responses of SOC and TN sequestration rates and dynamics to nitrogen addition in forest ecosystems worldwide remain unclear. This study conducted a global analysis to evaluate the effects of the nitrogen application rate, nitrogen addition duration (time), and humidity on the SOC and TN accumulation rates from 257 data points (63 articles). Nitrogen addition increased SOC and TN by 4.48% and 10.18%, respectively. The SOC and TN accumulation rates were 0.65 and 0.11 g kg−1 yr−1, respectively. Moreover, the percentage changes of SOC and TN overall increased with the nitrogen application rate and duration of nitrogen addition; however, the accumulation rates of SOC and TN overall decreased with the nitrogen application rate and the duration of nitrogen addition. In addition, the percentage changes and change rates of SOC and TN increased overall with the humidity index. In conclusion, nitrogen addition promoted SOC and TN accumulation in forest soil, and the nitrogen application rate and nitrogen addition duration increased the percentage changes in SOC and TN; however, they decreased the accumulation rate, whereas humidity increased the accumulation rates of SOC and TN. These results enhance our understanding of soil carbon and nitrogen cycling in forest soils in the context of global nitrogen deposition.

Interruption after Short-Term Nitrogen Additions Improves Ecological Stability of Larix olgensis Forest Soil by Affecting Bacterial Communities.

Atmospheric nitrogen deposition can alter soil microbial communities and further impact the structure and function of forest ecosystems. However, most studies are focused on positive or negative effects after nitrogen addition, and few studies pay attention to its interruption. In order to investigate whether interruption after different levels of short-term N additions still benefit soil health, we conducted a 2-year interruption after a 4-year short-term nitrogen addition (10 and 20 kg N·hm-2·yr-1) experiment; then, we compared soil microbial diversity and structure and analyzed soil physicochemical properties and their correlations before and after the interruption in Larix olgensis forest soil in northeast China. The results showed that soil ecological stabilization of Larix olgensis forest further improved after the interruption compared to pre-interruption. The TN, C:P, N:P, and C:N:P ratios increased significantly regardless of the previous nitrogen addition concentration, and soil nutrient cycling was further promoted. The relative abundance of the original beneficial microbial taxa Gemmatimonas, Sphingomonas, and Pseudolabrys increased; new beneficial bacteria Ellin6067, Massilia, Solirubrobacter, and Bradyrhizobium appeared, and the species of beneficial soil microorganisms were further improved. The results of this study elucidated the dynamics of the bacterial community before and after the interruption of short-term nitrogen addition and could provide data support and a reference basis for forest ecosystem restoration strategies and management under the background of global nitrogen deposition.

Adaptation Strategies of Seedling Root Response to Nitrogen and Phosphorus Addition.

The escalation of global nitrogen deposition levels has heightened the inhibitory impact of phosphorus limitation on plant growth in subtropical forests. Plant roots area particularly sensitive tissue to nitrogen and phosphorus elements. Changes in the morphological characteristics of plant roots signify alterations in adaptive strategies. However, our understanding of resource-use strategies of roots in this environment remains limited. In this study, we conducted a 10-month experiment at the Castanopsis kawakamii Nature Reserve to evaluate the response of traits of seedling roots (such as specific root length, average diameter, nitrogen content, and phosphorus content) to nitrogen and phosphorus addition. The aim was to reveal the adaptation strategies of roots in different nitrogen and phosphorus addition concentrations. The results showed that: (1) The single phosphorus and nitrogen-phosphorus interaction addition increased the specific root length, surface area, and root phosphorus content. In addition, single nitrogen addition promotes an increase in the average root diameter. (2) Non-nitrogen phosphorus addition and single nitrogen addition tended to adopt a conservative resource-use strategy to maintain growth under low phosphorus conditions. (3) Under the single phosphorus addition and interactive addition of phosphorus and nitrogen, the roots adopted an acquisitive resource-use strategy to obtain more available phosphorus resources. Accordingly, the adaptation strategy of seedling roots can be regulated by adding appropriate concentrations of nitrogen or phosphorus, thereby promoting the natural regeneration of subtropical forests.

Analyzing the Impact of Simulated Nitrogen Deposition on Stoichiometric Properties and Yield of Ma Bamboo (Dendrocalamus latiflorus Munro) Shoots, Leaves, and Soil Substrate

The growth dynamics of Ma bamboo (Dendrocalamus latiflorus Munro) are intricately linked to nitrogen availability, a pivotal nutrient. Escalating global nitrogen deposition, primarily driven by anthropogenic factors, is reshaping nutrient fluxes and productivity within forest and bamboo ecosystems. Such alterations bear significant implications for the growth equilibrium and yields of rapid-growth species such as Ma bamboo, thereby influencing their sustainable management strategies. This investigation delves into the responses of Ma bamboo under varying nitrogen deposition scenarios (0 g·clump−1, 11.2 g·clump−1, 13.5 g·clump−1, and 22.5 g·clump−1), examining stoichiometric attributes in bamboo shoots, leaves, and soil across distinct growth phases. Our empirical findings reveal that in the early growth stage, nitrogen enrichment markedly augmented N and P concentrations in the foliage and shoots, alongside a corresponding enhancement in soil P content. This was paralleled by a substantial reduction in the C:N ratio in leaves and the C:P ratio in shoots and soil, indicating an amplified uptake of P and N in both plant and soil matrices. During the middle stage, all nitrogen treatments boosted nitrogen levels across various plant tissues, while concurrently, soil C content exhibited a notable decline with increased nitrogen supplementation. In the late stage, leaf and soil N content continued to ascend; however, alterations in C content in both soil and leaves were not pronounced. Contrastingly, N and P levels in shoots showed a gradual decrement. Yield assessments disclosed that during the early stage, the N3 treatment (22.5 g·clump−1) not only delayed shoot emergence by 14 days but also surged the yield by 115.87% in comparison to the control (CK). In the late stage, the N2 treatment (13.5 g·clump−1) extended emergence duration by 10 days, with the yield apex under N3 treatment (22.5 g·clump−1) evidencing a 116.67% yield augmentation over CK. In summation, this study elucidates the stoichiometric balancing and distribution strategies within the plant–soil system of Ma bamboo, investigating its adaptability and responsive feedback to diverse nitrogen deposition gradients. This research contributes to a deeper understanding of plant nutrient adaptation mechanisms in the context of nitrogen deposition, enriches the discourse on plant population stoichiometry, and offers valuable insights and scientific underpinnings for broader-scale community or ecosystem stoichiometry studies.

Plant functional traits mediate the response magnitude of plant-litter-soil microbial C: N: P stoichiometry to nitrogen addition in a desert steppe

Global nitrogen deposition is significantly altering the carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in terrestrial ecosystems, yet how N deposition simultaneously affects plant-litter-soil-soil microbial stoichiometry in arid grassland is still unclear. In a five-year experimental study conducted in a desert steppe in Northern China, we investigated the effects of N addition on the C:N:P stoichiometry of plants, litter, soil, and soil microbes. We also used structural equation modelling (SEM) exploring the direct or indirect effects of N addition, plant species diversity, functional traits and diversity, soil microbial diversity, soil pH, soil electrical conductivity (EC) and moisture on the stoichiometry in plant-soil system. The results showed that N addition increased the N, P concentrations and N:P in plants, the N concentration and N:P in litter, and the C, N concentrations, C:P and N:P in microbes. Conversely, it decreased the C:N and C:P in plants, and litter C:N. Functional traits, functional dispersion (FDis), soil pH and EC accounted for a substantial proportion of the observed variations in elemental concentrations (from 42 % to 69 %) and stoichiometry (from 9 % to 73 %) across different components. SEM results showed that N addition decreased C:N and C:P in plants and litter by increasing FDis and leaf N content, while increased plant and litter N:P by decreasing leaf C content and increasing specific leaf area, respectively. Furthermore, N addition increased microbial C:P by increasing leaf thickness. We also found the mediating effects of soil pH and EC on C:N, C:P of litter and microbial N:P. Overall, our research suggests that plant functional traits as key predictors of nutrient cycling responses in desert steppes under N addition. This study extends the application of plant functional traits, enhances our understanding of C and nutrient cycling and facilitates predicting the response of desert steppes to N deposition.

Effects of nitrogen addition on species composition and diversity of early spring herbs in a Korean pine plantation.

Under the background of global nitrogen deposition, temperate forest ecosystems are suffering increasing threats, and species diversity is gradually decreasing. In this study, nitrogen addition experiments were conducted on Korean pine (Pinus koraiensis) plantations in Northeast China to explore the effect of long-term nitrogen addition on herb species diversity to test the following hypothesis: long-term nitrogen addition further reduced plant species diversity by affecting plant growth, which may be due to soil acidification caused by excessive nitrogen addition. Experimental nitrogen addition was conducted from 2014 to 2021, and the nitrogen treatment levels were as follows: N0 (control treatment, 0/(kg N ha-1 year-1)), N20 (low nitrogen treatment, 20/(kg N ha-1 year-1)), N40 (medium nitrogen treatment, 40/(kg N ha-1 year-1)) and N80 (high nitrogen treatment, 80/(kg N ha-1 year-1)). A herb community survey was conducted in the region from 2015 to 2021. The results showed that long-term nitrogen addition decreased soil pH, changed the species and composition of herbaceous plants, and decreased the species diversity of understory herbaceous plants. With the increase in nitrogen application years, middle- and high-nitrogen treatments significantly reduced the diversity of early-spring flowering herbs and early-spring foliating herbs, and their diversity decreased with the decrease in soil pH, indicating that soil acidification caused by long-term nitrogen addition may lead to the decrease of plant diversity. However, for early-spring growing herbs, adequate nitrogen addition may promote their growth. Our results show that plants have evolved different life-history strategies based on their adaptation mechanisms to the environment, and different life-history strategies have different responses to long-term nitrogen addition. However, for most plants, long-term nitrogen application will have a negative impact on the growth and diversity of herbs in temperate forests.

Global nitrogen deposition inputs to cropland at national scale from 1961 to 2020

Nitrogen (N) deposition is a significant nutrient input to cropland and consequently important for the evaluation of N budgets and N use efficiency (NUE) at different scales and over time. However, the spatiotemporal coverage of N deposition measurements is limited globally, whereas modeled N deposition values carry uncertainties. Here, we reviewed existing methods and related data sources for quantifying N deposition inputs to crop production on a national scale. We utilized different data sources to estimate N deposition input to crop production at national scale and compared our estimates with 14 N budget datasets, as well as measured N deposition data from observation networks in 9 countries. We created four datasets of N deposition inputs on cropland during 1961–2020 for 236 countries. These products showed good agreement for the majority of countries and can be used in the modeling and assessment of NUE at national and global scales. One of the datasets is recommended for general use in regional to global N budget and NUE estimates.

Nitrogen Deposition May Benefit to Larix olgensis Root Soils

Atmospheric nitrogen deposition affects the health of forest ecosystems by altering soil microbial activity. However, the effects of nitrogen addition levels, morphology and ecosystem type on whether nitrogen addition is beneficial or detrimental to soil health is controver-sial, and most studies have focused on the negative effects on microbial structure. Based on this, this study conducted a four-year experiment of nitrogen (NaNO3) addition at two levels (10 and 20 kg N hm−2·yr−1) in the understory soil of Larix olgensis in northeastern China to study soil microbial properties, soil enzyme activities, and to analyze soil physi-cochemical properties and the correlation between them. The results showed that nitrogen addition reduced soil pH and increased soil NH4+-N and NO3−-N contents, thus promoting the activities of Urease (Ure), Acid phosphatase (ACP) and N-Acetamidoglucosidase (NAG) and inhibiting the activity of Leucine aminopeptidase (LAP) in soil, further improving the diversity and richness of soil microorganisms and increasing the dominant taxa of beneficial microorganisms. This may be due to soil acidification caused by the addition of nitrogen, which increases the effectiveness of nitrogen in the soil, improving soil properties, moving soil health in a beneficial direction, promoting beneficial microbial activity, and making the soil more suitable for the growth of the acid-loving tree species L. olgensis. In general, N addition favored the development of soil bacterial communities and the maintenance of soil nutrient status, and had a positive effect on the soil nutrient status of L. olgensis. The results of this study may provide an important scientific basis for adaptive management of forest ecosystems in the context of global nitrogen deposition.

Mapping global nitrogen deposition impacts on soil respiration

Soil respiration (Rs) is a key indicator of belowground biological activities of terrestrial ecosystems. Despite ongoing atmospheric nitrogen (N) deposition due to anthropogenic activities, it remains uncertain how Rs responds to globally varied atmospheric N deposition. Based on a meta-analysis of 340 simulated experimental nitrogen addition studies, we aimed to identify the key factors altering the responses of Rs to N deposition and extrapolate these results to the global mapping of Rs changes under N deposition. We found the overall experimental N addition effect on Rs was insignificant, but the responses of Rs significantly shifted from positive to negative with increasing accumulated N addition amount and lower soil pH, and the negative responses to increasing N amounts were significantly intensified in acid soils. Also, the response of heterotrophic respiration to N addition significantly increased with a lower N amount, and both responses of heterotrophic and autotrophic respiration were significantly more negative in soils with lower pH. Our mapping efforts showed that global Rs overall increased by 2.8 % in response to the accumulated N deposition from 2000 to 2020. Regions with combined characteristics of high accumulated N deposition amounts and low soil pH, including Eastern U.S., Europe, and Eastern Asia, were hotspots of Rs declines under current and future atmospheric N deposition. Our findings challenge the long-held notion that N deposition has universal negative impacts on Rs, and suggest the spatial heterogeneity in the impacts of N deposition on belowground activities and carbon release across the globe.

Nitrogen deposition enhances the deterministic process of the prokaryotic community and increases the complexity of the microbial co-network in coastal wetlands

Global nitrogen deposition has increased significantly in recent years. At present, research on the effects of different amounts and types of nitrogen deposition on soil microorganisms in coastal wetlands is scarce. In this study, based on 7 years of simulated nitrogen deposition at multiple levels (low, medium, high) and of multiple types (NH4NO3, NH4Cl, KNO3), the effects of different nitrogen deposition conditions on the diversity, community assembly processes, co-networks, and community function of soil prokaryotes in coastal wetlands were examined. The results showed that, compared with that in control, the microbial α diversity increased significantly under nitrogen deposition (P < 0.05). However, it decreased significantly in the high-NH4NO3 and high-NH4Cl treatments (P < 0.05). The deterministic process of community assembly was strengthened under the different types of nitrogen deposition. Compared with that under NH4+-N deposition, the microbial co-network under NO3−-N deposition was more complex. Network stability significantly decreased under different NH4+-N deposition levels. In addition, the results of FAPROTAX functional prediction showed that microbial community functional groups associated with carbon and nitrogen cycling changed significantly (P < 0.05). In conclusion, our results emphasize that nitrogen deposition environments cause changes in soil microbial community structure and interactions, and may also affect soil carbon and nitrogen cycling, but the effects of different forms and levels of nitrogen deposition are not consistent. This study provides new insights for evaluating the changes in soil microbial communities in coastal wetlands caused by different types of long-term nitrogen deposition, and has scientific significance for assessing the ecological effects of long-term nitrogen deposition.

Impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation

Global atmospheric nitrogen deposition significantly affects the nutrient cycling and C–N–P stoichiometry in ecosystems. Herein, a global meta-analysis was conducted based on 898 pairwise observations to analyze the impact of nitrogen addition on plant-soil-enzyme C–N–P stoichiometry and microbial nutrient limitation in different ecosystem types (cropland, grassland, and forest), nitrogen addition intensity (0–5, 5–10, and >10 g N m−2 yr−1) and duration (0–5, 5–10, and >10yr). Results showed that nitrogen addition significantly decreased plant C:N (shoot: 16.5%, root: 27.1%, litter: 16.5%), soil C:N (5.9%), enzyme C:P (1.2%), and enzyme N:P (5.1%), whereas significantly increased soil C:P (4.9%), enzyme C:N (7.1%), vector angle (4.4%), vector length (3.9%), and plant N:P (shoot: 24.1%, root: 23.8%, and litter: 13.5%). Furthermore, nitrogen addition mainly affected the enzyme C:N and vector length in grasslands. Additionally, the changes in C:N in plants, soil, and enzymes, and vector angle and length were higher at nitrogen addition intensity of >10 g N m−2 yr−1. The changes in C:N and C:P in plant and soil were higher at nitrogen addition duration of >10 yr. Finally, the N:P in shoot, soil and enzyme, and vector angle were strongly correlated with mean annual precipitation (MAP). In conclusion, nitrogen addition significantly reduced the C:N ratio in plants and soil and increased plant N:P, and microbial C and P limitation. These effects vary with the ecosystem type, MAP, and nitrogen addition intensity and duration. The results improve our understanding of the plant-soil-microbial nutrient cycling processes in terrestrial ecosystems under global nitrogen deposition.

Factors Influencing the Molecular Compositions and Distributions of Atmospheric Nitrogen‐Containing Compounds

AbstractAtmospheric nitrogen‐containing organic compounds (NOCs) are critical components of global nitrogen deposition and light‐absorption species. The sources and compositions of NOCs are complex and remain largely unknown. Here, NOCs in 55 ambient aerosol samples collected in Guangzhou, South China, were analyzed via ultrahigh‐resolution Fourier transform ion cyclotron resonance mass spectrometry in negative‐ion and positive‐ion electrospray ionization (ESI) modes. The molecular compositions of NOCs measured via ESI– and ESI+ exhibited considerable differences. NOCs detected in the negative mode were mainly composed of highly oxygenated organic nitrates (O/N = 6), whereas NOCs detected in the positive mode were mainly composed of reduced nitrogen‐containing compounds (e.g., amides and amino acids). CHN compounds potentially corresponding to amines and alkaloids showed low abundance in the detection modes. Non‐metric multidimensional scaling and individual compound correlation analyses showed that the molecular compositions of NOCs were mainly affected by anthropogenic activities and meteorological parameters. For example, anthropogenic activities such as biomass burning and secondary nitrogen‐chemistry processes led to the accumulation of aromatic and highly oxygenated NOCs during winter. During summer, higher OH radical concentrations and temperatures will result in more prevalent or persistent reduced aliphatic NOCs, particularly lipid‐like amines. Some variables (e.g., relative humidity) have distinct effects on the variation of different types of NOCs. More research is needed to reveal the influencing mechanisms. This study clarifies the molecular compositions of NOCs and the mechanisms by which various factors influence the molecular variations. The findings can guide the assessment of NOCs evolution and deposition.

Responses of surface ozone to future agricultural ammonia emissions and subsequent nitrogen deposition through terrestrial ecosystem changes

Abstract. With the rising food demands from the future world population, more intense agricultural activities are expected to cause substantial perturbations to the global nitrogen cycle, aggravating surface air pollution and imposing stress on terrestrial ecosystems. Much less studied, however, is how the terrestrial ecosystem changes induced by agricultural nitrogen deposition may modify biosphere–atmosphere exchange and further exert secondary feedback effects on global air quality. Here we examined the responses of surface ozone air quality to terrestrial ecosystem changes caused by year 2000 to year 2050 changes in agricultural ammonia emissions and the subsequent nitrogen deposition by asynchronously coupling between the land and atmosphere components within the Community Earth System Model framework. We found that global gross primary production is enhanced by 2.1 Pg C yr−1, following a 20 % (20 Tg N yr−1) increase in global nitrogen deposition by the end of the year 2050 in response to rising agricultural ammonia emissions. Leaf area index was simulated to be higher by up to 0.3–0.4 m2 m−2 over most tropical grasslands and croplands and 0.1–0.2 m2 m−2 across boreal and temperate forests at midlatitudes. Around 0.1–0.4 m increases in canopy height were found in boreal and temperate forests, and there were ∼0.1 m increases in tropical grasslands and croplands. We found that these vegetation changes could lead to surface ozone changes by ∼0.5 ppbv (part per billion by volume) when prescribed meteorology was used (i.e., large-scale meteorological responses to terrestrial changes were not allowed), while surface ozone could typically be modified by 2–3 ppbv when meteorology was dynamically simulated in response to vegetation changes. Rising soil NOx emissions, from 7.9 to 8.7 Tg N yr−1, could enhance surface ozone by 2–3 ppbv with both prescribed and dynamic meteorology. We, thus, conclude that, following enhanced nitrogen deposition, the modification of the meteorological environment induced by vegetation changes and soil biogeochemical changes are the more important pathways that can modulate future ozone pollution, representing a novel linkage between agricultural activities and ozone air quality.

Fertilization Failed to Make Positive Effects on Torreya grandis in Severe N-Deposition Subtropics

In managed orchards, fertilization brings out not only high productivity expectations but also severe environmental pollution. Because economic profit takes priority over environmental cost, increasing amounts of fertilizer have been used in mature subtropical Torreya grandis orchards. However, given the magnitude of global nitrogen deposition, it’s worth considering whether heavy fertilizer treatment is necessary. To elucidate the balance between T. grandis nutrient demands and fertilizer supply, we determined the C, N, and P concentrations of foliar and soil ([C], [N], [P]) at 9 orchards undergoing long-term fertilizer treatments in two scenarios of N and N + P addition with different intensity. After documenting the dynamic variation of plant growth, nutrients characteristic, and the corresponding resorption efficiency, we found that excessive N addition interfered T. grandis’ sensibility to P availability in this N-enrichment area, leading to an increasing foliar [P] and resorption efficiency (PRE) and decoupling plant C:N:P ratios. As a result, enhanced fertilizer supply failed to improve carbon accumulation, plant growth, and yield effectively. These results demonstrate that extra fertilization in the N-saturated study area highly reduced the economic and ecological efficiency of fertilizers. Thus, our research suggests that N addition in the studied orchards should be rejected, and we recommend organic management as a more conducive method to achieve sustainable development.

连续氮添加14年对温带典型草原土壤碳氮组分及物理结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 连续氮添加14年对温带典型草原土壤碳氮组分及物理结构的影响 DOI: 10.5846/stxb202004150898 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31770519）；国家重点研发计划（2017YFC0503805） Effects of 14-year continuous nitrogen addition on soil carbon and nitrogen composition and physical structure at different depths in a typical temperate steppe Author: Affiliation: Fund Project: 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:全球氮沉降对生态系统造成了深远的影响，研究长时间氮沉降对草地生态系统土壤理化特征的影响有助于加强生态系统对氮沉降响应的长效机制的理解。通过连续14年长期施加N0（0 g N m-2 a-1）、N2（2 g N m-2 a-1）、N4（4 g N m-2 a-1）、N8（8 g N m-2 a-1）、N16（16 g N m-2 a-1）、N32（32 g N m-2 a-1）六种浓度尿素模拟氮沉降，并将土壤分成0-10、10-20和20-40 cm三个深度土层，研究温带草原生态系统土壤碳氮组分及物理结构对氮添加的响应及其相互关系，结果表明：（1）氮添加显著降低0-10 cm土壤酸碱度及土壤微生物量碳含量，N32相比N0分别下降了27.63%和58.40%（P<0.05）；各土层总有机碳和全氮含量对氮添加处理无显著响应，0-10 cm土层显著高于20-40 cm土层。（2）同一土层深度不同梯度氮添加处理显著增加土壤无机氮离子含量（P<0.05），0-10 cm土层铵态氮含量N32相比N0增加了88.72%，20-40 cm土层硝态氮含量N32相比N0增加了19.55倍，土壤深度与氮添加对无机氮离子含量影响具有显著的交互效应。（3）同一土壤深度不同梯度氮添加处理土壤粒度分形维数及土壤团聚体差异不显著，相关分析表明土壤碳氮元素含量与土壤结构显著相关。土壤碳氮组分在适宜浓度氮添加的增加趋势说明氮添加在一定程度上可能促进土壤理化性质的改良，氮添加对土壤物理结构的影响还需要进一步的深入研究。 Abstract:Global nitrogen deposition has a profound impact on terrestrial ecosystems. Studying the effects of long-term nitrogen (N) deposition on the soil physical and chemical characteristics of the grassland ecosystem help to understand the permanent mechanism of ecosystem response to nitrogen deposition. In this study, six gradients of urea application (0, 2, 4, 8, 16 and 32 g N m-2 a-1, treatments demonstrated as N0-N32) were applied to simulate N deposition for 14 consecutive years, and the soil samples were collected with three soil depths (0-10, 10-20, 20-40 cm from soil surface), to study the response of soil carbon (C) and nitrogen (N) components and physical structure to N addition and their correlations in temperate grassland ecosystem. The results showed that: (1) N addition significantly reduced soil pH and microbial biomass carbon (MBC) in the 0-10 cm soil layer, and N32 decreased by 27.63% and 58.40% (P<0.05), respectively, compared with N0. The content of total organic carbon and total nitrogen in all soil layers showed no significant response to N addition treatment, but the content in 0-10 cm soil layer was significantly higher than that in 20-40 cm soil layer. (2) N addition at each soil depth significantly increased inorganic nitrogen (ION) content (P<0.05); The ammonium nitrogen content in the 0-10 cm soil layer increased by 88.72% compared to N0, and the nitrate nitrogen content in the 20-40 cm soil layer increased by 19.55 times compared to N0; Soil depth and N addition had significant interaction effect on ION. (3) There was no significant difference in the fractal dimension of soil particle sizes or soil aggregates at each soil depth, and correlation analysis demonstrated that soil carbon and nitrogen nutrient contents were significantly associated with the soil structure. In conclusion, the increasing trend of C and N components in soil with optimal N addition concentration indicates that N addition may favor soil physical and chemical properties to some extent, thus the effect of N addition on soil physical structure needs further in-depth study. 参考文献 相似文献 引证文献

Effects of water and nitrogen stress on water utilization of dominant species in broadleaved Korean pine forest in Changbai Mountain, China

The aggravation of global nitrogen deposition may change plant water utilization and affect plant growth. Understanding the changes of vegetation water consumption under nitrogen deposition is of great significance for simulating and predicting the evolution of each component of forest hydrological cycle. We used the hydrogen and oxygen isotope tracer method to analyze water consumption source, quantity and law of Quercus mongolica (Qm), Fraxinus manshurica (Fm) and Tilia amurensis (Ta), the dominant species in broadleaved Korean pine forest of Changbai Mountain, under different add amounts of nitrogen [low nitrogen addition group (11.8 kg·hm-2·a-1), LN; high nitrogen addition group (23.6 kg·hm-2· a-1), HN] and different amounts of simulated precipitation (water addition amount were 0, 400, 800 and 1600 mL, equivalent to single rainfall amount were 0, 16, 32 and 64 mm, respectively). The results showed that under the condition of relative drought, soil water utilization ratio of Qm, Fm and Ta in the LN group were 26%, 12% and 20%, higher than that in HN group. When the amount of simulated precipitation was 16 mm, soil water utilization ratio of Qm, Fm and Ta in LN group reached the highest, being 73%, 70% and 43%, respectively. This ratio also reached a high value in HN group, but being less than the values in LN group. When the amount of simulated precipitation was 32 mm, soil water content approximated the average value in broadleaved Korean pine forest in the growing season in Changbai Mountain. The average soil water utilization ratio of test tree species in HN group was 39%, higher than that in LN group (16%). When the amount of simulated precipitation reached 64 mm, the soil water was saturation. Soil water utilization ratio of Qm, Fm and Ta in LN group was 14%, 5% and 1%, which was lower than that in HN group, the corresponding ratio were 64%, 13% and 10%, respectively. In conclusion, under the condition of less precipitation and relatively dry soil, the soil water utilization ratio of those three tree species were lower, and the increases of nitrogen availability further reduced the ratio. When the amount of precipitation was high and soil moisture was higher than the average value of the growing season, soil water utilization ratio of those tree species was higher. With the increases of soil nitrogen availability, this ratio was further increased.

Effect of nitrogen additions on soil pH, phosphorus contents and phosphatase activities in grassland

Phosphorus is a key nutrient for all plant species and a limiting factor for grassland ecosystem function. In recent years, in response to the rapid increase of global nitrogen deposition, soil phosphorus contents and phosphatase activities changed to varying degrees in grassland ecosystems. We conducted a meta-analysis to examine the responses of soil pH, total phosphorus (TP), available phosphorus (AP), as well as activities of alkaline phosphatase (AlP) and acid phosphatase (AcP) in soils to nitrogen addition amount, nitrogen type, experimental duration, and sampling depth. The correlation between soil pH and phosphatase response ratio was investigated. The results showed that nitrogen addition significantly reduced soil pH, TP and AlP activity, while significantly increased AcP activity, but had no significant effect on AP. Soil pH and AlP activity significantly decreased under nitrogen addition >5 g·m-2·a-1, and AcP activity significantly increased under high nitrogen addition (>10 g·m-2·a-1). The contents of TP and AP significantly decreased when nitrogen addition was 5-10 g·m-2·a-1. NH4NO3 treatment significantly reduced soil TP and increased AcP activity, while urea treatment significantly reduced soil pH and AlP activity. Across all nitrogen addition amounts, when the experiment duration was 3 to 10 years, soil TP content and AlP activity were significantly reduced. Soil pH was significantly reduced after three years nitrogen addition, and AcP activitiy was significantly increased after 10 years nitrogen addition. In the 0-10 cm soil layer, the TP content and AlP activity significantly decreased, while the AP content significantly increased. In >10 cm soil layer, the AP content was significantly decreased. The significant negative correlation between soil pH and AcP activity indicated that change in soil pH caused by nitrogen addition may be an important factor for the variation of soil phosphatase activity.

Responses of non-structural carbohydrates content in leaves of different plant species in Pinus tabuliformis plantation to nitrogen addition

Through its impact on plant physiological processes, global nitrogen deposition could alter the structure and composition of forest ecosystems. However, we are not clear about the effects of N deposition on leaves' non-structural carbohydrate (NSC) content of different plants. In this study, we compared the responses of NSC contents in seven different plant species to four nitrogen addition levels (0, 3, 6, and 9 g N·m-2·a-1, referred to as N0, N3, N6, N9, respectively), including Pinus tabuliformis, Quercus liaotungensis, Lonicera japonica, Spiraea salicifolia, Rosa xanthina, Rubia cordifolia, and Carex lanceolata in an artificial Pinus tabuliformis forest located in the hilly area of the Loess Plateau. The contents of soluble sugar and starch varied greatly in plant species, with the highest variability in R. xanthina and the lowest in S. salicifolia and C. lanceolata. There were significant differences in the responses of soluble sugar and starch contents to nitrogen addition among different species. Under N6 treatment, the variability of soluble sugar and starch in R. cordifolia came the first while S. salicifolia exceeded all other species under N3 and N9 treatments on that rating. The specific species with the lowest variability of soluble sugar and starch contents differed with nitrogen addition levels. With the increases of nitrogen addition rate, the soluble sugar content of P. tabuliformis and C. lanceolata exhibited a continuous rising trend, an opposite trend of S. salicifolia, while that of Q. liaotungensis, L. japonica, and R. xanthina decreased first and then increased, reaching its minimum at N6 treatment. The response of R. cordifolia to nitrogen addition was complex. With respect to starch content, P. tabuliformis, L. japonica and C. lanceolata showed a continuous increase trend with nitrogen addition whereas S. salicifolia decreased first and then increased, troughing at N3 treatment. R. xanthina and R. cordifolia responded complicatedly yet Q. liaotungensis appeared less responsive. Under N addition treatments, there was no explicit correlation between NSC content and soil physical and chemical properties including pH, organic carbon, total nitrogen and phosphorus. There was a significant influence of those soil properties on the soluble sugar/starch ratio under N0 or N3 treatment. Our results indicate that different species have obviously different responses of NSC to nitrogen addition. Future research concerning the impacts of global nitrogen deposition on forest ecosystems should take into account the target species, especially to pay attention to the responses of vegetation with different life forms.

Global Estimates of Inorganic Nitrogen Deposition Across Four Decades

AbstractAtmospheric deposition of inorganic nitrogen is critical to the function of ecosystems and elemental cycles. During the industrial period, humans have doubled the amount of inorganic nitrogen in the biosphere and radically altered rates of atmospheric nitrogen deposition. Despite this rapid change, estimates of global nitrogen deposition patterns generally have low, centennial‐scale temporal resolution. Lack of information on annual‐ to decadal‐scale changes in global nitrogen deposition makes it difficult for scientists researching questions on these finer timescales to contextualize their work within the global nitrogen cycle. Here we use the GEOS‐Chem Chemical Transport Model to estimate wet and dry deposition of inorganic nitrogen globally at a spatial resolution of 2° × 2.5° for 12 individual years in the period from 1984 to 2016. During this time, we found an 8% increase in global inorganic nitrogen deposition from 86.6 to 93.6 TgN/year, a trend that comprised a balance of variable regional patterns. For example, inorganic nitrogen deposition increased in areas including East Asia and Southern Brazil, while inorganic nitrogen deposition declined in areas including Europe. Further, we found a global increase in the percentage of inorganic nitrogen deposited in chemically reduced forms from 30% to 35%, and this trend was largely driven by strong regional increases in the proportion of chemically reduced nitrogen deposited over the United States. This study provides spatially explicit estimates of inorganic nitrogen deposition over the last four decades and improves our understanding of short‐term human impacts on the global nitrogen cycle.