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1.
土壤有机碳(SOC)是陆地生态系统碳库的核心组成部分,其动态平衡受气候、土壤、植被、地形及人类活动等的影响,但在不同的空间尺度上,这些影响因素的相对重要性和差异还不明确。为阐明不同尺度和不同土层深度土壤有机碳密度(SOCd,kg/m3土壤)的环境影响因子差异,选用全球113571个土壤剖面SOCd测量数据以及38个环境协变量数据,利用数据挖掘方法,分析了全球尺度和生物群系尺度不同土层深度SOCd的控制因子,并量化了空间自相关对相关结果的影响。研究结果表明:仅空间自相关就能解释全球尺度不同土壤深度13%-20%的SOCd空间变异,但是随土壤深度的增加,空间自相关的解释率降低。在剔除空间自相关的影响后,分析结果表明:全球尺度上,气候因素对SOCd空间变异的解释率最高,但只能解释17%-20%,这种解释率在不同土层之间没有显著差异。在生物群系尺度上,除北方森林地区,气候因素能够解释SOCd空间变异的24%-37%;而在北方森林地区,地形是影响SOCd空间变异的重要因素,对SOCd的解释率为21%-43%。这些结果表明,SOCd的控制因子在不同的尺度上明显不同。无论是在全球尺度上,还是生物群系尺度上,如果不考虑空间自相关,地形的影响会被低估,其他环境因素的影响被严重高估。为了准确计算全球与生物群系尺度上各土层SOCd分布的控制因子及其分异情况,空间自相关必须被考虑。 相似文献
2.
The impact of regional climate change on net primary productivity (NPP) is an important aspect in the study of ecosystems’ response to global climate change. China’s ecosystems are very sensitive to climate change owing to the influence of the East Asian monsoon. The Lund–Potsdam–Jena Dynamic Global Vegetation Model for China (LPJ-CN), a global dynamical vegetation model developed for China’s terrestrial ecosystems, was applied in this study to simulate the NPP changes affected by future climate change. As the LPJ-CN model is based on natural vegetation, the simulation in this study did not consider the influence of anthropogenic activities. Results suggest that future climate change would have adverse effects on natural ecosystems, with NPP tending to decrease in eastern China, particularly in the temperate and warm temperate regions. NPP would increase in western China, with a concentration in the Tibetan Plateau and the northwest arid regions. The increasing trend in NPP in western China and the decreasing trend in eastern China would be further enhanced by the warming climate. The spatial distribution of NPP, which declines from the southeast coast to the northwest inland, would have minimal variation under scenarios of climate change. 相似文献
3.
Effect of land use conversion on soil organic carbon sequestration in the loess hilly area, loess plateau of China 总被引:5,自引:0,他引:5
Liding Chen Jie Gong Bojie Fu Zhilin Huang Yilong Huang Lide Gui 《Ecological Research》2007,22(4):641-648
Changes in land use may alter land cover, which results in carbon stock changes in biomass as well as in the soil. In China’s
loess plateau, vegetation restoration has been conducted since 1950s to control soil erosion and improve the ecosystem, with
significant investment of money and manpower. Despite these efforts, soil erosion has still been severe. To reduce soil erosion
and improve land quality, China initiated another state-funded project, Grain-for-Green, in 1999 in the loess plateau. However, it is not clear how effective this newly initiated project will be. In this study,
we evaluated the effect of land-use conversion on soil organic carbon (SOC) and the potential effect of the current project
on SOC sequestration in the Anjiapo catchment area of the loess hilly area of the loess plateau in China. This evaluation
is based on SOC measurements in cropland versus in other converted land use types. We found that SOC sequestration mainly
occurred in the surface soil after land use conversion took place. Land use conversion from cropland to shrubland or wild
grassland (i.e. undisturbed land) was better for SOC sequestration than tree plantation in the semi-arid loess hilly area.
By using the land use change in the study area as a scenario, the potential contribution of land use change on SOC sequestration
due to the Grain-for-Green project was estimated. It was found that this project in the loess plateau of China would be helpful for SOC sequestration
if successfully implemented. 相似文献
4.
白洋淀湿地区土壤有机碳密度及储量的空间分布特征 总被引:2,自引:0,他引:2
湿地生态系统碳储量是陆地生态系统碳循环的重要组成部分,提供重要的生态系统服务功能。白洋淀湿地是国家重要生态湿地和华北平原最大的淡水湿地,同时是雄安新区的核心水系,湿地区土壤碳储量的估算研究将为湿地生态系统服务评估和湿地生态恢复提供数据支撑。研究通过对白洋淀湿地7种不同地类的105个土壤剖面进行分层取样,揭示了其湿地土壤有机碳密度及储量的空间分布特征,结果表明:(1)白洋淀湿地区土壤有机碳含量整体偏低,在各层土壤中,淹水芦苇湿地的有机碳含量均显著高于其他植被类型,约为其他类型土壤碳含量的3倍左右。(2)在各植被类型中土壤有机碳含量均以表层(0—20 cm)最高,其分配比例均集中在30%左右,随着土壤剖面深度的增加,湿地土壤的有机碳含量逐渐减少。(3)不同植被类型土壤有机碳含量与土壤有机碳密度的差异显著,具体表现为:乔木园地<旱地<常绿针叶林<落叶阔叶林<水田<台田芦苇<淹水芦苇。(4)根据估算,白洋淀湿地区的土壤有机碳储量约为5816.77×103Mg。随着雄安新区环境治理工作的推进,白洋淀湿地区生态系统固碳将呈现持续向好态势,结... 相似文献
5.
Ecosystem carbon stocks and their changes in China’s grasslands 总被引:5,自引:0,他引:5
The knowledge of carbon (C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China’s
terrestrial C cycle. To date, a comprehensive assessment on C balance in China’s grasslands is still lacking. By reviewing
published literature, this study aims to evaluate ecosystem C stocks (both vegetation biomass and soil organic C) and their
changes in China’s grasslands. Our results are summarized as follows: (1) biomass C density (C stock per area) of China’s
grasslands differed greatly among previous studies, ranging from 215.8 to 348.1 g C m−2 with an average of 300.2 g C m−2. Likewise, soil C density also varied greatly between 8.5 and 15.1 kg C m−2. In total, ecosystem C stock in China’s grasslands was estimated at 29.1 Pg C. (2) Both the magnitude and direction of ecosystem
C changes in China’s grasslands differed greatly among previous studies. According to recent reports, neither biomass nor
soil C stock in China’s grasslands showed a significant change during the past 20 years, indicating that grassland ecosystems
are C neutral. (3) Spatial patterns and temporal dynamics of grassland biomass were closely correlated with precipitation,
while changes in soil C stocks exhibited close associations with soil moisture and soil texture. Human activities, such as
livestock grazing and fencing could also affect ecosystem C dynamics in China’s grasslands. 相似文献
6.
Land use induced changes of organic carbon storage in soils of China 总被引:29,自引:0,他引:29
Using the data compiled from China's second national soil survey and an improved method of soil carbon bulk density, we have estimated the changes of soil organic carbon due to land use, and compared the spatial distribution and storage of soil organic carbon (SOC) in cultivated soils and noncultivated soils in China. The results reveal that ~ 57% of the cultivated soil subgroups ( ~ 31% of the total soil surface) have experienced a significant carbon loss, ranging from 40% to 10% relative to their noncultivated counterparts. The most significant carbon loss is observed for the non‐irrigated soils (dry farmland) within a semiarid/semihumid belt from northeastern to southwestern China, with the maximum loss occurring in northeast China. On the contrary, SOC has increased in the paddy and irrigated soils in northwest China. No significant change is observed for forest soils in southern China, grassland and desert soils in northwest China, as well as irrigated soils in eastern China. The SOC storage and density under noncultivated conditions in China are estimated to ~ 77.4 Pg (1015 g) and ~ 8.8 kg C m?2, respectively, compared to a SOC storage of ~ 70.3 Pg and an average SOC density of ~ 8.0 kg C m?2 under the present‐day conditions. This suggests a loss of ~ 7.1 Pg SOC and a decrease of ~ 0.8 kg C m?2 SOC density due to increasing human activities, in which the loss in organic horizons has contributed to ~ 77%. This total loss of SOC in China induced by land use represents ~ 9.5% of the world's SOC decrease. This amount is equivalent to ~ 3.5 ppmv of the atmospheric CO2 increase. Since ~ 78% of the currently cultivated soils in China have been degraded to a low/medium productivities and are responsible for most of the SOC loss, an improved land management, such as the development of irrigated and paddy land uses, would have a considerable potential in restoring the SOC storage. Assuming a restoration of ~ 50% of the lost SOC during the next 20–50 years, the soils in China would absorb ~ 3.5 Pg of carbon from the atmosphere. 相似文献
7.
Soil organic carbon (SOC) plays an important role in soil fertility and carbon sequestration, and a better understanding of the spatial patterns of SOC is essential for soil resource management. In this study, we used boosted regression tree (BRT) and random forest (RF) models to map the distribution of topsoil organic carbon content at the northeastern edge of the Tibetan Plateau in China. A set of 105 soil samples and 12 environmental variables (including topography, climate and vegetation) were analyzed. The performance of the models was evaluated using a 10-fold cross-validation procedure. Maps of the mean values and standard deviations of SOC were generated to illustrate model variability and uncertainty. The results indicate that the BRT and RF models exhibited very similar performance and yielded similar predicted distributions of SOC. The two models explained approximately 70% of the total SOC variability. The BRT and RF models robustly predicted the SOC at low observed SOC values, whereas they underestimated high observed SOC values. This underestimation may have been caused by biased distributions of soil samples in the SOC space. Vegetation-related variables were assigned the highest importance in both models, followed by climate and topography. Both models produced spatial distribution maps of SOC that were closely related to vegetation cover. The SOC content predicted by the BRT model was clearly higher than that of the RF model in areas with greater vegetation cover because the contributions of vegetation-related variables in the two models (65% and 43%, respectively) differed significantly. The predicted SOC content increased from the northwestern to the southeastern part of the study area, average values produced by the BRT and RF models were 27.3 g kg−1 and 26.6 g kg−1, respectively. We conclude that the BRT and RF methods should be calibrated and compared to obtain the best prediction of SOC spatial distribution in similar regions. In addition, vegetation variables, including those obtained from remote sensing imagery, should be taken as the main environmental indicators and explicitly included when generating SOC maps in Alpine environments. 相似文献
8.
Effects of wind erosion on the spatial heterogeneity of soil nutrients in two desert grassland communities 总被引:9,自引:0,他引:9
Wind is known to affect the spatial heterogeneity of soil resources in arid and semiarid systems, but multi-year, quantified
observations are largely absent. We studied the effects of wind erosion on the spatial distribution of soil organic carbon
(SOC) and other soil nutrients at the Jornada Experimental Range, in southern New Mexico. Enhanced wind erosion was encouraged
by grass cover reduction in a Sporobolus-mesquite dominated site (SM) and a Bouteloua-mesquite dominated site (BM). The scale and magnitude of spatial dependence for the soil analytes were quantified using geostatistical
analyses. Results of this study show that soil organic matter related analytes such as SOC, TN, Navail, and SO4
2- are among the first to be eroded and redistributed; cations such as Ca2+ and Mg2+ may not be removed and redistributed significantly; and other ions such as K+, Na+ and Cl− showed no discernible pattern of change. Geostatistics show that wind appeared to increase the scale of spatial autocorrelation,
but decrease the scale of spatial dependence of most soil analytes over 2–3 windy seasons. In the wind enhanced plot of the
SM site, up to 99% of the spatial dependence of SOC was autocorrelated at the distance of 1.45 m before the initiation of
wind erosion, but the spatial dependence dropped significantly to only 60% at a larger autocorrelation distance of 2.76 m
after three windy seasons. Similar but less significant changes were observed for SOC in the BM site. Despite the differential
effects of wind on the soil analytes, we conclude that the overall results of wind on the grass cover reduction plots are
the disappearance of small, strong fertile islands, which may be related to grasses; and the reinforcement of large fertile
islands, which are likely related to mesquite shrubs. In addition, the change of the spatial patterns of SOC and other soil
nutrients induced by enhanced wind erosion may persist and reinforce soil islands associated with shrubs, thus allowing a
positive feedback for further desertification in this arid grassland. 相似文献
9.
Spatial Distribution of Soil Organic Carbon and Its Influencing Factors in Desert Grasslands of the Hexi Corridor,Northwest China 总被引:1,自引:0,他引:1
Knowledge of the distribution patterns of soil organic carbon (SOC) and factors that influence these patterns is crucial for understanding the carbon cycle. The objectives of this study were to determine the spatial distribution pattern of soil organic carbon density (SOCD) and the controlling factors in arid desert grasslands of northwest China. The above- and belowground biomass and SOCD in 260 soil profiles from 52 sites over 2.7×104 km2 were investigated. Combined with a satellite-based dataset of an enhanced vegetation index during 2011–2012 and climatic factors at different sites, the relationships between SOCD and biotic and abiotic factors were identified. The results indicated that the mean SOCD was 1.20 (SD:+/− 0.85), 1.73 (SD:+/− 1.20), and 2.69 (SD:+/− 1.91) kg m−2 at soil depths of 0–30 cm, 0–50 cm, and 0–100 cm, respectively, which was smaller than other estimates in temperate grassland, steppe, and desert-grassland ecosystems. The spatial distribution of SOCD gradually decreased from the southeast to the northwest, corresponding to the precipitation gradient. SOCD increased significantly with vegetation biomass, annual precipitation, soil moisture, clay and silt content, and decreased with mean annual temperature and sand content. The correlation between BGB and SOCD was closer than the correlation between AGB and SOCD. Variables could together explain about 69.8%, 74.4%, and 78.9% of total variation in SOCD at 0–30 cm, 0–50 cm, and 0–100 cm, respectively. In addition, we found that mean annual temperature is more important than other abiotic factors in determining SOCD in arid desert grasslands in our study area. The information obtained in this study provides a basis for accurately estimating SOC stocks and assessing carbon (C) sequestration potential in the desert grasslands of northwest China. 相似文献
10.
Soil organic carbon budget and fertility variation of black soils in Northeast China 总被引:5,自引:0,他引:5
Black soils in Northeast China are characteristic of high soil organic carbon (SOC) density and were strongly influenced by
human activities. Therefore, any change in SOC pool of these soils would not only impact the regional and global carbon cycle,
but also affect the release and immobilization of nutrients. In this study, we reviewed the research progress on SOC storage,
budget, variation, and fertility under different scenarios. The results showed that the organic carbon storage of black soils
was 646.2 TgC and the most potential sequestration was 2887.8 g m−2. According to the SOC budget, the net carbon emission of black soils was 1.3 TgC year−1 under present soil management system. The simulation of CENTURY model showed that future climate change and elevated CO2 concentration, especially the increase of precipitation, would increase SOC content. Furthermore, fertilization and cropping
sequence obviously influenced SOC content, composition, and allocation among different soil particles. Long-term input of
organic materials such as manure and straw renewed original SOC, improved soil structure and increased SOC accumulation. Besides,
soil erosion preferred to transport soil particles with low density and fine size, decreased recalcitrant SOC fractions at
erosion sites and increased activities of soil microorganism at deposition sites. After natural grasslands were converted
into croplands, obvious variation of soil chemical nutrients, physical structure, and microbial activities had taken place
in surface and subsurface soils, and represented a degrading trend to a certain degree. Our studies suggested that adopting
optimal management such as conservation tillage in black soil region is an important approach to sequester atmospheric CO2 and to slow greenhouse effects. 相似文献
11.
盐沼湿地在缓解温室效应和应对气候变化方面发挥着重要作用,是重要的"蓝碳"生态系统。储存在盐沼湿地土壤中的有机碳(SOC)是盐沼湿地碳汇的主要成分,但受植被覆盖、土壤环境等生境要素变化的显著影响。以长江口崇明岛周缘的盐沼湿地为典型研究区域,分别测量了环岛不同样线和不同植被区SOC含量及环境因子(盐度、容重、碳氮比(C/N)等),在此基础上分析了盐沼湿地SOC储量的空间分布格局及其影响因素。结果表明:(1)崇明岛周缘盐沼湿地SOC含量和储量均存在明显的空间异质性,北侧的土壤SOC含量高于南侧,东北侧的SOC储量高于西南侧区域;(2)垂直各层上,SOC含量呈现随土层深度增加逐渐减少的趋势,表层0-50 cm深度的单位面积SOC储量大于50-100 cm深度;(3)植物类型和土壤理化因素(土壤C/N、土壤盐度、土壤容重等)在一定程度上影响了崇明岛周缘盐沼湿地土壤碳储量的空间格局。研究表明,受河口区植被和土壤理化性质等多种因素空间异质性的共同影响,盐沼湿地土壤SOC储量格局也易呈现空间差异,因此在开展盐沼湿地储碳机制研究、科学评估盐沼湿地储碳能力及实现盐沼"蓝碳"固碳增汇时应充分考虑区域间的环境和生态的空间异质性特征。 相似文献
12.
Losses of soil organic carbon under wind erosion in China 总被引:7,自引:0,他引:7
Hao Yan Shaoqiang Wang† Changyao Wang‡ Guoping Zhang Nilanchal Patel§ 《Global Change Biology》2005,11(5):828-840
Soil organic carbon (SOC) storage generally represents the long‐term net balance of photosynthesis and total respiration in terrestrial ecosystems. However, soil erosion can affect SOC content by direct removal of soil and reduction of the surface soil depth; it also affects plant growth and soil biological activity, soil air CO2 concentration, water regimes, soil temperature, soil respiration, carbon flux to the atmosphere, and carbon deposition in soil. In arid and semi‐arid region of northern China, wind erosion caused soil degradation and desert expansion. This paper estimated the SOC loss of the surface horizon at eroded regions based on soil property and wind erosion intensity data. The SOC loss in China because of wind erosion was about 75 Tg C yr?1 in 1990s. The spatial pattern of SOC loss indicates that SOC loss of the surface horizon increases significantly with the increase of soil wind erosion intensity. The comparison of SOC loss and annual net primary productivity (NPP) of terrestrial ecosystem was discussed in wind erosion regions of China. We found that NPP is also low in the eroded regions and heavy SOC loss often occurs in regions where NPP is very small. However, there is potential to improve our study to resolve uncertainty on the soil organic matter oxidation and soil deposition processes in eroded and deposited sites. 相似文献
13.
Soil inorganic carbon storage pattern in China 总被引:1,自引:0,他引:1
NA MI SHAOQIANG WANG JIYUAN LIU GUIRUI YU WENJUAN ZHANG ESTEBAN JOBBÁGY 《Global Change Biology》2008,14(10):2380-2387
Soils with pedogenic carbonate cover about 30% (3.44 × 106 km2) of China, mainly across its arid and semiarid regions in the Northwest. Based on the second national soil survey (1979–1992), total soil inorganic carbon (SIC) storage in China was estimated to be 53.3±6.3 PgC (1 Pg=1015 g) to the depth investigated to 2 m. Soil inorganic carbon storages were 4.6, 10.6, 11.1, and 20.8 Pg for the depth ranges of 0–0.1, 0.1–0.3, 0.3–0.5, and 0.5–1 m, respectively. Stocks for 0.1, 0.3, 0.5, and 1 m of depth accounted for 8.7%, 28.7%, 49.6%, and 88.9% of total SIC, respectively. In contrast with soil organic carbon (SOC) storage, which is highest under 500–800 mm yr−1 of mean precipitation, SIC storage peaks where mean precipitation is <400 mm yr−1. The amount and vertical distribution of SIC was related to climate and land cover type. Content of SIC in each incremental horizon was positively related with mean annual temperature and negatively related with mean annual precipitation, with the magnitude of SIC content across land cover types showing the following order: desert, grassland >shrubland, cropland >marsh, forest, meadow. Densities of SIC increased generally with depth in all ecosystem types with the exception of deserts and marshes where it peaked in intermediate layers (0.1–0.3 m for first and 0.3–0.5 m for latter). Being an abundant component of soil carbon stocks in China, SIC dynamics and the process involved in its accumulation or loss from soils require a better understanding. 相似文献
14.
Bomb <Superscript>14</Superscript>C enrichment indicates decadal C pool in deep soil? 总被引:1,自引:0,他引:1
Studies of changes in soil organic carbon (SOC) stocks normally limit their focus to the upper 20–30 cm of soil, yet 0–20 cm
SOC stocks are only ∼40% of 0–1 m SOC. Accounting for only the upper 20–30 cm of SOC has been justifiable assuming that deeper
SOC is unreactive since it displays 14C-derived mean residence times of hundreds or thousands of years. The dramatic increase in the 14C content of the atmosphere resulting from thermonuclear testing circa 1963 allows the unreactivity of deep SOC to be tested
by examining whether deep soils show evidence of ‘bomb-14C’ incorporation. At depths of 40–100 cm, a well-studied New Zealand soil under stable pastoral management displays progressive
enrichment of over 200‰ across samplings in 1959, 1974 and 2002, indicating substantial incorporation of bomb 14C. This pattern of deep 14C enrichment—previously observed in 2 well-drained California grassland soils—leads to the hypothesis that roots and/or dissolved
organic C transport contribute to a decadally-reactive SOC pool comprising ∼10–40% of SOC below 50 cm. Deep reactive SOC may
be important in the global C cycle because it can react to land-use or vegetation change and may respond to different processes
than the reactive SOC in the upper 20–30 cm of soil. 相似文献
15.
Variation in soil carbon stocks and their determinants across a precipitation gradient in West Africa 总被引:1,自引:0,他引:1
Gustavo Saiz Michael I. Bird Tomas Domingues Franziska Schrodt Michael Schwarz Ted R. Feldpausch Elmar Veenendaal Gloria Djagbletey Fidele Hien Halidou Compaore Adama Diallo Jon Lloyd 《Global Change Biology》2012,18(5):1670-1683
We examine the influence of climate, soil properties and vegetation characteristics on soil organic carbon (SOC) along a transect of West African ecosystems sampled across a precipitation gradient on contrasting soil types stretching from Ghana (15°N) to Mali (7°N). Our findings derive from a total of 1108 soil cores sampled over 14 permanent plots. The observed pattern in SOC stocks reflects the very different climatic conditions and contrasting soil properties existing along the latitudinal transect. The combined effects of these factors strongly influence vegetation structure. SOC stocks in the first 2 m of soil ranged from 20 Mg C ha?1 for a Sahelian savanna in Mali to over 120 Mg C ha?1 for a transitional forest in Ghana. The degree of interdependence between soil bulk density (SBD) and soil properties is highlighted by the strong negative relationships observed between SBD and SOC (r2 > 0.84). A simple predictive function capable of encompassing the effect of climate, soil properties and vegetation type on SOC stocks showed that available water and sand content taken together could explain 0.84 and 0.86 of the total variability in SOC stocks observed to 0.3 and 1.0 m depth respectively. Used in combination with a suitable climatic parameter, sand content is a good predictor of SOC stored in highly weathered dry tropical ecosystems with arguably less confounding effects than provided by clay content. There was an increased contribution of resistant SOC to the total SOC pool for lower rainfall soils, this likely being the result of more frequent fire events in the grassier savannas of the more arid regions. This work provides new insights into the mechanisms determining the distribution of carbon storage in tropical soils and should contribute significantly to the development of robust predictive models of biogeochemical cycling and vegetation dynamics in tropical regions. 相似文献
16.
Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon
(C) cycle. However, little is known about biomass C stocks and dynamics in these grasslands. During 2001–2005, we conducted
five consecutive field sampling campaigns to investigate above-and below-ground biomass for northern China’s grasslands. Using
measurements obtained from 341 sampling sites, together with a NDVI (normalized difference vegetation index) time series dataset
over 1982–2006, we examined changes in biomass C stock during the past 25 years. Our results showed that biomass C stock in
northern China’s grasslands was estimated at 557.5 Tg C (1 Tg=1012 g), with a mean density of 39.5 g C m−2 for above-ground biomass and 244.6 g C m−2 for below-ground biomass. An increasing rate of 0.2 Tg C yr−1 has been observed over the past 25 years, but grassland biomass has not experienced a significant change since the late 1980s.
Seasonal rainfall (January–July) was the dominant factor driving temporal dynamics in biomass C stock; however, the responses
of grassland biomass to climate variables differed among various grassland types. Biomass in arid grasslands (i.e., desert
steppe and typical steppe) was significantly associated with precipitation, while biomass in humid grasslands (i.e., alpine
meadow) was positively correlated with mean January-July temperatures. These results suggest that different grassland ecosystems
in China may show diverse responses to future climate changes. 相似文献
17.
The spatial variability of soil organic carbon (SOC) and total nitrogen (STN) levels is important in both global carbon-nitrogen cycle and climate change research. There has been little research on the spatial distribution of SOC and STN at the watershed scale based on geographic information systems (GIS) and geostatistics. Ninety-seven soil samples taken at depths of 0–20 cm were collected during October 2010 and 2011 from the Matiyu small watershed (4.2 km2) of a hilly area in Shandong Province, northern China. The impacts of different land use types, elevation, vegetation coverage and other factors on SOC and STN spatial distributions were examined using GIS and a geostatistical method, regression-kriging. The results show that the concentration variations of SOC and STN in the Matiyu small watershed were moderate variation based on the mean, median, minimum and maximum, and the coefficients of variation (CV). Residual values of SOC and STN had moderate spatial autocorrelations, and the Nugget/Sill were 0.2% and 0.1%, respectively. Distribution maps of regression-kriging revealed that both SOC and STN concentrations in the Matiyu watershed decreased from southeast to northwest. This result was similar to the watershed DEM trend and significantly correlated with land use type, elevation and aspect. SOC and STN predictions with the regression-kriging method were more accurate than those obtained using ordinary kriging. This research indicates that geostatistical characteristics of SOC and STN concentrations in the watershed were closely related to both land-use type and spatial topographic structure and that regression-kriging is suitable for investigating the spatial distributions of SOC and STN in the complex topography of the watershed. 相似文献
18.
Vertical distribution of fine roots in relation to soil factors in Pinus tabulaeformis Carr. forest of the Loess Plateau of China 总被引:5,自引:0,他引:5
Growth and vertical distribution of fine root closely depend on soil resource availability. Better understanding of relationships
of root profile with vertical distribution of available soil resource and soil characteristics can allow ecologists to predict
the fine root distribution on the scales ranging from individual plants to vegetation communities. The objective of the study
was to understand the fine root mass density (FRMD), fine root length density (FRLD), fine root area density (FRAD), mean
root diameter and specific root length (SRL), vertical distribution in soil profile and their relation with soil environment
factors in semiarid and arid Loess Plateau of China. The vertical fine root distribution and soil bulk density, soil moisture
and soil inorganic N in 0-60 cm soil profile (0–15, 15–30, 30–45 and 45–60 cm intervals) were investigated by soil coring
methods in three Pinus tabulaeformis Carr. forests chosen at three locations. The fine root density parameters (FRMD, FRLD and FRAD) and SRL peaked in the most
upper soil layer (0–15 cm interval) and decreased with increased soil depth. The results provided a strong support that soil
water rather than soil inorganic N is a key control on fine root distribution in the Loess Plateau. With increased soil moisture,
the root mass, length and SRL increased and the mean root diameter decreased. The effects of soil bulk density on the fine
root parameters were consistent with those of the soil water. An unexpected result was obtained about the relationships between
soil organic N and the root distributions and occurrences because of no differences among the soil depth intervals in soil
inorganic N content. It might be associated with severe soil water deficit limiting soil nitrogen utilization efficiency in
arid Loess Plateau. 相似文献
19.
桂西北典型喀斯特峰丛洼地退耕还林还草的固碳效益评价 总被引:3,自引:0,他引:3
退耕还林还草作为桂西北喀斯特地区主要的土地利用转变方式,对该区域产生了积极的生态效益。就退耕还林还草政策的实施对该区域土壤有机碳储量的影响进行评价。结果表明:1)将剖面碳密度与深度做对数拟合得到的参数进行协同克里格插值的方法能较准确估算研究区碳密度,R2为0.723;2)退耕还林还草措施对土壤有机碳(SOC)含量产生了显著的影响,耕地(19.3 g/kg)转变为牧草(23.5 g/kg,退耕近10a)和草地(34.6 g/kg,退耕30a)的SOC含量均有增加,转变为人工林(17.8 g/kg,退耕8a)的SOC含量略有下降;3)退耕还林还草工程实施后研究区土壤碳储量提高了23.43%,退耕后单位面积土壤碳储量为2938 t C/km~2;4)种植牧草兼顾固碳效益和经济效益,是一种较好的退耕模式。 相似文献
20.
Jian Ni 《Nordic Journal of Botany》2000,20(4):415-426
Net primary production (NPP) and leaf area index (LAI) of Chinese biomes were simulated by BIOME3 under the present climate, and their responses to climate change and doubled CO2 under a future climatic scenario using output from Hadley Center coupled ocean‐atmosphere general circulation model with CO2 modelled at 340 and 500 ppmv. The model estimated annual mean NPP of the biomes in China to be between 0 and 1270.7 gC m‐2 yr‐1 at present. The highest productivity was found in tropical seasonal and rain forests while temperate forests had an intermediate NPP, which is higher than a lower NPP of temperate savannas, grasslands and steppes. The lowest NPP occurred in desert, alpine tundra and ice/polar desert in cold or arid regions, especially on the Tibetan Plateau. The lowest monthly NPP of each biome occurred generally in February and the highest monthly NPP occurred during the summer (June to August). The annual mean NPP and LAI of most of biomes at changed climate with CO2 at 340 and 500 ppmv (direct effects on physiology) would be greater than present. The direct effects of carbon dioxide on plant physiology result in significant increase of LAI and NPP. The carbon storage of Chinese biomes at present and changed climates was calculated by the carbon density and vegetation area method. The present estimates of carbon storage are totally 175.83 × 1012 gC (57.57 × 1012 gC in vegetation and 118.28 × 1012 gC in soils). Changed climate without and with the CO2 direct physiological effects will result in an increase of carbon storage of 5.1 and 16.33 × 1012, gC compared to present, respectively. The interaction between elevated CO2 and climate change plays an important role in the overall responses of NPP and carbon to climate change. 相似文献