Soil Total Nitrogen Density Research Articles

宁夏草地土壤有机碳空间特征及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 宁夏草地土壤有机碳空间特征及其影响因素 DOI: 10.5846/stxb202201040022 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（42061037） Spatial characteristics of soil organic carbon in grassland of Ningxia and its influencing factors 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:草地是重要的碳汇资源库，在陆地生态系统碳循环中扮演着重要角色。探明草地土壤有机碳的空间分布格局及其影响因素对于推动区域生态系统碳汇管理，实现"双碳"目标和绿色高质量发展具有重要意义。以宁夏三种主要草地类型为研究对象，基于野外样点调查，采用结构方程模型，分析了草地土壤有机碳的空间分布特征及其影响因素。结果表明：不同类型草地土壤有机碳含量表现为草甸草原高于典型草原，荒漠草原最低，垂直剖面上均随土壤深度的增加而降低。草甸草原和荒漠草原有机碳空间变异自表层向下逐渐增大，典型草原在20-40 cm土层变异系数达到最大。有机碳分布在区域上从南部六盘山山地向中部干旱风沙带逐渐降低。路矩分析发现，海拔高度、地上生物量、降水量、温度和土壤含水量可解释土壤有机碳空间变异的91.4%。海拔高度对土壤有机碳总效应最大（作用系数为0.78），海拔高度引起的降水和温度等要素区域分异间接影响土壤有机碳含量；地上生物量对土壤有机碳的直接正向效应最大（0.559）；降水量对土壤有机碳效应分为直接效应和作用于生物量及土壤含水量的间接影响；温度表现为通过生物量对土壤有机碳间接产生负向效应（-0.259）。宁夏草地土壤有机碳的空间分布主要受降水量和与其密切相关的生物量的支配作用。近20年来降水量增多和草地人为干扰减少，宁夏草地碳汇作用显著。 Abstract:Grasslands are important contributors of carbon sequestration among terrestrial ecosystems, which play an important role in the global biogeochemical cycle and energy exchange. Based on field surveys in July-August 2021, soil samples of meadow steppe, typical steppe and desert steppe in Ningxia were collected. The organic carbon contents, bulk density, total nitrogen, and pH of these soil samples were measured. We also monitored factors affecting carbon distribution such as altitude, annual precipitation, annual mean temperature, aboveground biomass and soil water content. Results indicated that content of the soil organic carbon decreased along the vertical soil profile, the average organic carbon content followed the order of meadow steppe > typical steppe > desert steppe. The distribution of grassland soil organic carbon gradually decreased from the Liupan Mountains in the south to the dry sand belt in the middle along the altitude. Soil organic carbon was significantly positively correlated with aboveground biomass, annual precipitation, altitude and soil total nitrogen density, and significantly negatively correlated with annual mean temperature (P<0.001), positively correlated with soil water content, and negatively with soil bulk density (P<0.01), and no obvious correlation with soil pH. Amos structural equation model was applied to evaluate the combined effects of environmental factors on grassland soil organic carbon. The most important factors affecting organic carbon was altitude (r=0.78), which mainly caused regional differentiation of precipitation and temperature to affect soil organic carbon indirectly; followed by aboveground biomass (r=0.559); then annual precipitation (0.539), which not only directly but also indirectly affected the soil organic carbon by altering aboveground biomass and soil water content positively. Annual mean temperature indirectly affected organic carbon negatively by influencing aboveground biomass (r=-0.259). The spatial distribution of grassland organic carbon in Ningxia was dominated by precipitation and aboveground biomass closely related to precipitation. In the past 20 years, with the increase of precipitation and the reduction of grassland anthropogenic disturbance, grassland ecosystem in Ningxia had a very significant carbon sink function. 参考文献 相似文献 引证文献

Growing season grazing promotes the shallow stratification of soil nutrients while non-growing season grazing sequesters the deep soil nutrients in a typical alpine meadow

Grazing management and climate are known to be important drivers influencing soil nutrient accumulation. The change of soil nutrients in pasture depends on the excreta return and the vegetation regeneration. Livestock activities significantly affect plant growth and soil nutrients through feeding, trampling, and excretion. At the same time, grazing time and climate change are stimulating plant growth and altering plant composition. How long-term specific grazing management will affect soil nutrient storage and movement under a warming-humid climate trend needs further study. In 20-year grazing management trial, conducted in a typical alpine meadow in the Qilian Mountains on the Qinghai-Tibet Plateau, sampled and analyzed the soil from under a non-growing season graze pasture (WP) and a growing season graze pasture (SAP) in August 1999 and August 2019 along grazing gradients (GG) at different distances from the pasture entrance (0, 300, 600, 900, 1200, and 1500 m). The experimental results of 2019 compared to 1999 show that SAP and WP increased soil available nitrogen density (SAND) and availability (SAND:soil total nitrogen density [STND] ratio) in the first 300 m along the grazing gradient soil, while SAP showed a decrease in soil available phosphorus density (SAPD) and availability (SAPD:soil total phosphorus density [STPD] ratio), and WP had no significant difference between gradients. Grazing in spring and autumn increased soil organic carbon density (SOCD), and STND in the first 300 m along the gradient soil, whereas it had the reverse effect in WP. At the same time, STPD has no obvious changing trend along the gradient. Growing and non-growing season grazing increased the SOCD:STND ratio in the first 300 m along the grazing gradient but resulted to a lower STND:STPD ratio. The comparison found that long-term grazing from 1999 to 2019 increased the SAND and SAPD. SAP improved soil total C, N, and P density in the topsoil (0–10 cm), but WP improved it throughout the profile (0–40 cm). These findings indicate that time of grazing and the grazing gradient affect the accumulation and migration of different elements under long-term grazing. Furthermore, SAP and WP had a positive effect on the accumulation of topsoil and deep soil nutrients, respectively. We suggest that periodic pasture exchange in SAP and WP should be carried out to maintain the sustainability of the ecosystem. At the same time, for different gradients, especially the first 300 m, regular soil nutrient monitoring and human intervention (such as fertilization) should be carried out to eliminate potential element restrictions and focus on the development of possible problems caused by the livestock locked in the pens at night, such as nutrient enrichment (the excreta as the organic fertilizer and soil improvement material for farmland) and loss (element footprint) in pens, which are of important guiding significance for the grazing system’s stable development of alpine meadow.

Total Nitrogen Stock in Soil Profile Affected by Land Use and Soil Type in Three Counties of Mollisols

Soil total nitrogen is the major indicator of soil fertility and quality in agricultural ecosystems. However, few comparative studies investigated the spatial patterns of soil total nitrogen density (STND) in deep soils of different land uses and soil types. Therefore, our study aimed to identify the influence of environmental factors on spatial variability in STND by comparing the STND spatial patterns of different land uses and soil types in a typical Mollisols in northeast China. Results showed that land use types did not significantly affect STND, but the soil types did. The STND was more heterogeneous above 60 cm than that in subsoil, and no significant changes in STND were found in the same land use or soil type. The STND had a significant correlation with SOC, soil BD and pH regardless of land use or soil type. The STND in the soil profile (100 cm) and top 20 cm was fitted using a mathematical model. The results provided insights into nitrogen cycle and stock in similar areas in northeast China.

Drivers of Soil Total Nitrogen and Phosphorus Storage in Alpine Wetland Across the Three Rivers Source Region on the Qinghai-Tibetan Plateau

Although soil total nitrogen (STN) and soil total phosphorus (STP) play significant roles in terrestrial ecosystem function, their storage and driving factors in the alpine wetlands of the Qinghai-Tibetan Plateau remain unclear. In this study, we estimated STN and STP storage and their controlling factors, including vegetation, soil, and climate characteristics, using data collected from 50 sites across the wetlands in the Three Rivers Source Region. STN and STP storage in the top 30 cm of soil were 62.12 ± 37.55 Tg N and 9.24 ± 2.90 Tg P, respectively. Although STN density did not differ significantly for different vegetation types (i.e., alpine meadow and alpine wetland), belowground biomass showed a positive relationship with STN density. Mean annual precipitation (MAP) showed a significant positive relationship with STN density, whereas the effects of mean annual temperature on STN density were minor. Compared with the effects of vegetation and climatic factors, soil characteristics were found to not only exert a significant effect on STN density, but also influence the effects of climate and vegetation on STN density. For STP density, soil characteristics were found to be a significant controlling factor, whereas the effects of biomass and climatic factors were minor. The studied climate, soil, and vegetation characteristics jointly explained ∼54% of STN variance, whereas soil characteristics explained only 20% of STP variation. MAP indirectly affected STN density via effects on vegetation and soil, and its direct effect on STN density was minor. This indicated a strong relationship between biotic and abiotic effects and STN density. Identification of the factors influencing STN and STP variance in alpine wetlands contributes to our understanding of the biogeochemical cycle in high-altitude regions.

Spatial Variability of Soil Organic Carbon and Total Nitrogen in Desert Steppes of China’s Hexi Corridor

Stock estimates are critical to quantifying carbon and nitrogen sequestration, quantifying greenhouse gas emissions, and understanding key biogeochemical processes (i.e., soil carbon and nutrient cycling). Many studies have assessed soil organic matter and nutrients in different ecosystems. However, the spatial distribution of carbon and nitrogen and the key influencing factors in arid desert steppe remain unclear. Here, we investigated the soil organic carbon (SOC) and soil total nitrogen (STN) to a depth of 100 cm at 126 sites in a desert steppe in northwestern China.SOCandSTNcontents decreased with increasing depth; the highest averageSOCandSTNcontents were 12.70 and 0.65 g kg−1in the surface 5 cm, and the lowest were from 80 to 100 cm (4.49 and 0.16 g kg−1, respectively).SOCdensity (SOCD) andSTNdensity (STND) to a depth of 100 cm averaged 8.94 and 0.45 kg m−2, respectively. The top 1 m of the soils stored approximately 1,041 TgSOCand 52 TgSTNin the study area. Geostatistical analysis showed strong and moderate spatial autocorrelation forSOCDin different soil layers, but the autocorrelation forSTNDgradually weakened with increasing depth.SOCDandSTNDdecreased from southwest to northeast in the study area, along an elevation gradient. Both were significantly positively correlated with topographic variables, precipitation, and the normalized-difference vegetation index, but negatively correlated with temperature and aridity. More than 40% of theSOCDandSTNDspatial variation was explained by elevation, which was the dominant factor. The data and high-resolution maps from this study will support future soil carbon and nitrogen analyses.

Relative importance of climatic variables, soil properties and plant traits to spatial variability in net CO2 exchange across global forests and grasslands

Compared to the well-known drivers of spatial variability in gross primary productivity (GPP), the relative importance of climatic variables, soil properties and plant traits to the spatial variability in net ecosystem exchange of CO2 between terrestrial ecosystem and atmosphere (NEE) is poorly understood. We used principal component regression to analyze data from 147 eddy flux sites to disentangle effects of climatic variables, soil properties and plant traits on the spatial variation in annual NEE and its components (GPP and ecosystem respiration (RE)) across global forests and grasslands. Our results showed that the largest unique contribution (proportion of variance only explained by one class of variables) to NEE variance came from climatic variables for forests (24%-30%) and soil properties for grasslands (41%-54%). Specifically, mean annual precipitation and potential evapotranspiration were the most important climatic variables driving forest NEE, whereas available soil water capacity, clay content and cation exchange capacity mainly influenced grassland NEE. Plant traits showed a small unique contribution to NEE in both forests and grasslands. However, leaf phosphorus content strongly interacted with soil total nitrogen density and clay content, and these combined factors represented a major contribution for grassland NEE. For GPP and RE, the majority of spatial variance was attributed to the common contribution of climate, soil and plant traits (50% - 62%, proportion of variance explained by more than one class of variables), rather than their unique contributions. Interestingly, those factors with only minor influences on GPP and RE variability (e.g., soil properties) have significant contributions to the spatial variability in NEE. Such emerging factors and the interactions between climatic variables, soil properties and plant traits are not well represented in current terrestrial biosphere models, which should be considered in future model improvement to accurately predict the spatial pattern of carbon cycling across forests and grasslands globally.

Effects of fencing and grazing on the temporal dynamic of soil organic carbon content in two temperate grasslands in Inner Mongolia, China

This study aimed to investigate the impact of long-term grassland management on the temporal dynamic of SOC density in two temperate grasslands. The top soil SOC density, soil total nitrogen density and soil bulk density (0–20 cm) under long-term fencing and grazing treatments, the aboveground net primary productivity of fenced plots and the associated climatic factors of Leymus chinensis and Stipa grandis grasslands in Inner Mongolia were collected from literatures and analyzed. The results showed that the SOC density increased linearly with fenced duration but was insensitive to grazed duration in both grasslands. Compared with long-term grazing, fenced plots had larger potential for carbon sequestration, and the accumulation rate of SOC density was 29 and 35 g Cm–2y–1 for L. chinensis and S. grandis grasslands. Fenced duration and mean annual temperature jointly contributed large effect on temporal pattern of SOC density. Climate change and grazed duration had little influence on the inter-annual variance of SOC density in grazed plots. Our results confirmed the enhancement effect of long-term fencing on soil carbon sequestration in degraded temperate grassland, and long-term permanent plot observation is essential and effective for accurately and comprehensively understanding the temporal dynamic of SOC storage.

Spatial and Seasonal Variations of Soil Carbon and Nitrogen Content and Stock in a Tidal Salt Marsh with Tamarix chinensis, China

To investigate the spatial and seasonal variations of soil organic carbon (SOC) and total nitrogen (TN) contents and stocks in tidal salt marsh soils, 15 cores to a depth of 40 cm were collected in five sampling sites along a sampling belt during three seasons. Our results showed that higher SOC and TN contents occurred in the surface soils in three sampling seasons. Spatial distributions of SOC and TN showed moderate variability. The C/N ratios were higher in the summer and autumn than in spring. The soil organic carbon density (SOCD) and soil total nitrogen density (TND) ranked in the following order: autumn > spring > summer. And the SOCD values positively correlated with the distances from the tidal creek in summer, while this correlation was negative in autumn and spring. The soil properties, such as the soil moisture, salinity, C/N ratio and C/P ratio, significantly correlated with the SOC and TN contents and stocks. The water and salinity regulation and the alternation of ratios of ecological stoichiometry should be considered to strengthen carbon and nitrogen sequestration in coastal wetlands.

福建省耕地土壤全氮密度和储量动态变化研究

福建省耕地土壤全氮密度和储量动态变化研究

Plant dispersal systems in Neotropical forests: availability of dispersal agents or availability of resources for constructing zoochorous fruits?

AbstractAimWe used abiotic and biotic factors as predictors of the proportions of different dispersal systems in Neotropical forests, to test whether the geographical patterns in dispersal systems are mostly related to the availability of resources for constructing zoochorous fruits or to the availability of dispersal agents.Location101 one‐hectare vegetation plots established in eight Holdridge life‐zones in Colombian Neotropical forests.MethodsWe assigned dispersal systems to 2262 species and 1210 morphospecies, using the relative frequency and relative abundance of endozoochory, synzoochory, anemochory and hydrochory per plot as response variables. We assessed the relationships between dispersal systems and ecological factors (elevation, climatic and edaphic variables, raw and weighted richness of potential frugivores, biomass of primates, wind speed, flooding regime and fragmentation), controlling for spatial autocorrelation and phylogenetic constraints.ResultsEndozoochory was highly represented in all plots. High levels of rainfall and low precipitation seasonality were associated with high proportions of zoochory (endozoochory and synzoochory) and low proportions of anemochory. The biomass of primates was positively associated with the relative abundance of endozoochory, and the weighted richness of frugivores was positively associated with the relative frequency of endozoochory. Contrary to the resource‐availability hypothesis, synzoochory (the most expensive dispersal system in terms of plant investment in fruit mass) was most common in soils with low carbon densities. Finally, the proportions of anemochory and hydrochory were highest in windy areas and flooded forests, respectively.Main conclusionsAlthough there is a relationship between rainfall, zoochory and anemochory, the absence of any positive relationships between zoochory, temperature, soil total nitrogen density and soil carbon density shows that the proportions of dispersal systems in Colombian Neotropical forests are mostly related to the availability of dispersal agents.

Effects of Soil Quality Arising from the Conversion of Intrazonal Grassland in an Agro-Pasturage Ecotone of China

Understanding the effects of land-use changes on soil property is crucial for the sustainable development in an agro-pastoral ecotone of China. Although grassland conversion is an important land-use change in northern China, most studies have focused on zonal grassland areas and the intrazonal grassland areas have been ignored, which is not climatic climax of natural grassland, because it is constrained by terrain, surface water, components of the earth surface and other ecological factors. The present study aims to determine the effects of the conversion of intrazonal grassland into cropland on soil properties in the Bashang area where a typical agro-pastoral ecotone of northern China is found. The results showed that intrazonal grassland conversion and subsequent tillage practices increased soil bulk density and decreased soil porosity, capillary moisture capacity, and soil nutrients content. Available soil zinc content in the study area was at extremely low level, which could not meet the need of crop growing based on the soil trace elements appraisal criteria of China. On the average, the conversion of intrazonal grassland into cropland led soil organic carbon density (SOCD) decreased from 22.49 kg m-2 to 13.24 kg m-2, and soil total nitrogen density (STND) from 2.23 kg m-2 to 1.27 kg m-2; that is, the meadow conversion resulted in a 41-43% reduction of SOCD and STND in 0–60 cm soil depth over about 20 years. To conserve the present status, the further conversion of grassland into cropland should be stopped, and encourage the restoration of cropped area into grassland to combat the soil desertification and degradation in the agro-pasturage ecotone of Northern China.

ASSESSMENT OF LAND COVER CHANGES AND THEIR EFFECT ON SOIL ORGANIC CARBON AND SOIL TOTAL NITROGEN IN DAQING PREFECTURE, CHINA

The aim of this study was to examine the influence of land cover changes on soil organic carbon (SOC) and soil total nitrogen (STN) in the Daqing Prefecture of China, where heavy industrialisation in the form of dense oil wells has impacted the environment. Time-series presentations for the period 1978 to 2008 of remotely sensed data and soil survey data were used to assess the extent of the changes. The study revealed soil degradation under all land cover types and in all soil types, grassland retreat (−15 per cent), swampland retreat (−45 per cent) and increases in the area of farmland (+19 per cent), sand land (+1450 per cent) and alkaline land (+52 per cent). Depletion of the SOC pool occurred in swampland (−64 per cent) both because of the decrease in the area of swampland and because of a decrease in SOC density (−34 per cent). An increase in the SOC pool occurred in alkaline land because of the increase in the area and also because of an increase in SOC density (+297 per cent), but there was little change in the SOC pool in farmland because the increase in area was largely offset by a decrease in SOC density (−14 per cent). The decrease in the STN pool was substantial (−44 per cent), with the largest contributor being the decrease in swamplands (−74 per cent), partly because of the decrease in the area of swampland and partly because of a decrease in STN density (−52 per cent). Large decreases in the STN pool also occurred in farmland (−22 per cent) and grassland (−41 per cent). The direct impacts of construction associated with the expansion of the oil industry were overshadowed by indirect impacts such as interference with water flows and water levels resulting in salinisation of soil. The study also revealed that land cover changes are much more dynamic than a simple analysis would reveal, and because of lag times in the loss of SOC, soil degradation will continue even if land cover changes cease. Copyright © 2012 John Wiley & Sons, Ltd.

松嫩平原玉米带农田土壤氮密度时空格局

Nitrogen is a major nutrient for all living organism on Earth and plays a central role in regulating the composition,structure,and function of ecosystems.Most nitrogen within terrestrial ecosystems is stored in soil organic matter.Total nitrogen in soils is mostly correlated with soil organic carbon content.The enrichment experiments of carbon dioxide further indicate that nitrogen limitation directly influences carbon sequestration by terrestrial ecosystems.Increased nitrogen availability normally increases productivity and biomass accumulation in ecosystems.However,few studies have been conducted to calculate soil nitrogen density and storage and to analyze its tempo-spatial variations in the Songnen Plain Maize Belt. Based on the second national soil survey of Jilin Province conducted around 1980 and field measurements of nitrogen density taken in years from 2003 to 2006,this study was devoted to calculate the density and total storage of nitrogen in top soils(0—20 cm) of the Songnen Plain Maize Belt and investigate the spatial and temporal variations of nitrogen density and possible underlying factors during the period from 1980 to 2005,including land-use types,original nitrogen content,and soil organic carbon changes.The totals of soil nitrogen storage were(40.47 ± 1.67)×108 kg and(40.28 ± 1.35)×108 kg in 1980 and 2005,respectively.The spatial patterns of soil total nitrogen density were similar in 1980 and 2005,higher in the centre and lower in the edge parts.The average of soil total nitrogen density over the entire study area changed only marginally in 25 years,about 0.31 kg/m2 in 1980 and 2005.However,the changes of soil total nitrogen density in 25 years varied with soils and land use types.Soil total nitrogen density increased in dark brown,paddy,and boggy soils.It did not change or even decreased in other soil types.Soil total nitrogen density changed a little in dry lands while it decreased obviously in paddy lands.The annual decrease rate of total nitrogen storage in top soils was 7.6×105 kg/a.The change of soil total nitrogen density in 25 years was negatively correlated with its initial value in 1980,but positively correlated with the change of soil organic carbon density.Soil nitrogen sequestration potential was generally defined as the difference between the equilibrium value of soil nitrogen storage and its initial value.The new equilibrium value of soil total nitrogen density was 0.32 kg/m2 in the study area.Without changes in land use and management after 1980,the soils of croplands in the study area has a potential of annually sequestrating nitrogen at the rate of 5.18×106 kg/a.However,the total nitrogen storage in 2005 was 1.2×108 kg lower than the potential of nitrogen sequestration.Actually,the application of nitrogenous fertilizer increased in the past 25 years according to the census data of Jilin Province.Therefore,reasonable fertilization should be practiced in this area.The management of croplands should be enhanced,especially for paddy lands converted from uplands.

Spatial variability of soil carbon, nitrogen, and phosphorus content and storage in an alpine wetland in the Qinghai - Tibet Plateau, China

This study considers the spatial variability of soil organic carbon, nitrogen, and phosphorus storage in a drained alpine wetland and the possible relationships with soil properties. Top 0–0.30 m soil samples were collected in a typical alpine wetland in the south-eastern Qinghai–Tibet plateau using grid sampling. There was high spatial variability for soil organic carbon density (SOCD), soil total nitrogen density (STND), and soil total phosphorous density (STPD) in the drained alpine wetland. Spherical models best described the structure of the semivariograms for SOCD and STPD, and an exponential model for STND, with the range parameter of &lt;4 m. Similar spatial distribution with lower or higher patches of C, N, and P storage were observed. SOCD, STND, and STPD were significantly negatively correlated with soil moisture (P &lt; 0.01), and significantly positively correlated with bulk density (P &lt; 0.01). However, no significant correlations were observed between SOCD, STND, and STPD and soil pH values. Wetland drainage might lead to higher C, N, and P densities in top 0.30 m soils due to peat compaction; thus, it is necessary to incorporate water table fluctuations or the whole depth of peat layers to estimating precisely C, N and P storage.