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1.
The distribution of soil organic matter (SOM) and nitrogen on Gongga Mountain was studied in this paper. The results showed that the content of SOM and nitrogen (N) of A horizon had an ascending trend with the increase of the elevation. The vegetation types distributed higher than the mixed broad-leaved and coniferous forest have the irregular trends. In the transitional zone vegetation such as mixed trees and treeline, the content of SOM and N is higher than other vegetation types. The distribution of SOM and N of A horizon is dependent on the synthetic effect of climate and vegetation types. The vertical distribution of SOM and N in soil profiles has the similar trends for all kinds of vegetation types, i.e., the content of A horizon is higher than that of the B and C horizons, which is the same to the distribution of dead animal and plant in soil. The soil C:N is between 7 and 25, which is relatively low comparing to the appropriate C:N of 25-30. The ratio of soil carbon to nitrogen (C:N) increases with the increase of the elevation, but its vertical distribution in soil horizons varies with different vegetation types. The N exists in SOM mainly in the form of organic nitrogen, and the soil C:N correlates significantly with SOM.  相似文献   

2.
Soil respiration is one of the primary fluxes of carbon between soils and the atmosphere.It is produced by rhizosphere respiration and soil microbial respiration.Soil respiration is not only affected by environmental factors,but also changes with the hu-man-induced disturbances of ecosystems.Land-use,the measures of land management,the pollution of soil,and so on can affect soil respiration and change the soil efflux.According to some research,the authors summed up their impacts on soil respiration by human activities through land-use changes and land-management measures among agroecosystem,grassland ecosystem,and for-est ecosystem.The results showed that (1) when adding fertilization to farmland,the soil respiration will increase;(2) fenced land can decrease soil respiration,while soil respiration in the grazed land at a grassland ecosystem will decline with the increasing of grazing intensity;(3) with grassland fertilization;farmland cultivation;fire,fertilization,and cutting of forest,conflicting results were found in the changes of soil respiration.Perhaps plant species,site condition,and measurement season can lead to different results on soil respiration.  相似文献   

3.
In order to analyze the effect of rain enrichment on soil respiration rate of a Nitraria sphaerocarpa community, we measured soil respiration rate in bare and vegetated areas in a hyperarid area （Dunhuang） during the growing season. Results show that rain enrichment can increase bare and vegetated soil respiration rates. The more rainfall enrichment, the greater the increment and the longer duration time effect for soil respiration rate. 200% （16 mm） and 300% （24 mm） of rain enrichment can significantly increase bare soil respiration rates by 90% and 106% （P〈0.01）, respectively. By contrast, areas with 100% （8 mm）, 200% （16 mm） and 300% （24 mm） of rain enrichment can significantly increase shrub area respiration rates by 68%, 157% and 205% （P〈0.01）, respectively. The response time of bare and vegetated soil respiration to rainfall enrichment is asynchronous. Response variable of soil respiration in vegetated soil is higher （118%） than in bare soil. There was significant positive correlation between soil respiration rate and soil water content during the growing season （P〈0.01）. For every 1 mm increment of precipitation, soil respiration rate increased by 0.01 and 0.04 pmol/（m2.s）, respectively in vegetated and bare soils.  相似文献   

4.
陕北地区退耕还林还草工程土壤保护效应的时空特征   总被引：1，自引：1，他引：0  
This paper looks at the Green for Grain Project in northern Shaanxi Province.Based on remote sensing monitoring data,this study analyzes the locations of arable land in northern Shaanxi in the years 2000,2010 and 2013 as well as spatio-temporal changes over that period,and then incorporates data on the distribution of terraced fields to improve the input parameters of a RUSLE model and simulate and generate raster data on soil erosion for northern Shaanxi at different stages with a accuracy verification.Finally,combined with the dataset of farmland change,compared and analyzed the characteristics of soil erosion change in the converted farmland to forest(grassland)and the unconverted farmland in northern Shaanxi,so as to determine the project’s impact on soil erosion over time across the region.The results show that between 2000 and 2010,the soil erosion modulus of repurposed farmland in northern Shaanxi decreased 22.7 t/ha,equivalent to 47.08%of the soil erosion modulus of repurposed farmland in 2000.In the same period,the soil erosion modulus of non-repurposed farmland fell 10.99 t/ha,equivalent to 28.6%of the soil erosion modulus of non-repurposed farmland in 2000.The soil erosion modulus for all types of land in northern Shaanxi decreased by an average of 14.51 t/ha between 2000 and 2010,equivalent to 41.87%of the soil erosion modulus for the entire region in 2000.This suggests that the Green for Grain Project effectively reduced the soil erosion modulus,thus helping to protect the soil.In particular,arable land that was turned into forest and grassland reduced erosion most noticeably and contributed most to soil conservation.Nevertheless,in the period 2010 to 2013,which was a period of consolidation of the Green for Grain Project,the soil erosion modulus and change in volume of soil erosion in northern Shaanxi were significantly lower than in the previous decade.  相似文献   

5.
This study investigated the effects of various grazing systems, including continuous grazing, rotational grazing, and no-grazing systems, on the community biomass in the Stipa breviflora Griseb desert grassland during the grazing seasons in 2005, 2006, and 2007, based on study sites established in 1999. We found that the seasonal dynamics of the aboveground biomass were quite similar among the three treatments, which reached peak values in period from August to September during each study year. The continuous grazing system reduced the aboveground biomass from 2005 to 2007 under drought conditions, and the rotational grazing and no-grazing systems maintained more aboveground biomass than the continuous grazing system did. The belowground biomass declined with the increase of soil depth among the three treatments, and in the surface 20-cm soil layer it accounted for more than 60% of the total biomass. The belowground biomass was found to be highly correlated with soil depth under rotational grazing. The total belowground biomass within the 0–100-cm soil layer for rotational grazing was significantly higher than for continuous grazing and no-grazing, and had 15,775 kg/ha more biomass. Our results demonstrate that conservative rotational grazing can alleviate grassland deterioration by reserving more aboveground and belowground biomass than the continuous grazing system does.  相似文献   

6.
Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.  相似文献   

7.
From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China (NSTEC). Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency (WUE) and nitrogen use efficiency (NUE), and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed: (1) vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. (2) Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE (p<0.001). While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE (p<0.001). Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. (3) There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC (p<0.001), indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mechanism and give a dramatic disturbance to the ecosystem biogeochemical cycle.  相似文献   

8.
This paper focuses on the growth response of Caragana microphylla seedlings to changes of artificially controlled water table in Horqin Sandy Land, China. Monitoring results of soil water content shows that soil moisture is closely correlated to groundwater depths. Soil volumetric water increased rapidly when close to water sources and finally stabilized in a saturated state. The soil moisture trend of CK(control) increased gradually at 0–50 cm of soil depth then decreased to 4% below 50 cm soil depth. C. microphylla can adapt to different soil environments by changes in ecological and physiological characteristics. By comparing the ecological characteristics of C. microphylla seedlings at various water tables, we found that a shallow water table of 40 cm depth inhibited seedling growth because of weak ecological characteristics. A groundwater depth of 120 cm was more advantageous for plant height and canopy growth of C. microphylla seedlings. During the first two years, the most suitable water depth for root biomass was 120 cm, and 180 cm for root length. The growth of vertical roots is positively correlated with groundwater depth, and root thickness is the determinate factor for root biomass while the fine root is the determinate factor for root length. A thick root would grow much more in a natural drought environment while access to ground water promotes the growth of fine roots.  相似文献   

9.
Based on the MODIS NDVI data and Landsat TM/ETM data of 2002 and 2012, this paper extracts the planting area of winter wheat–summer maize, single spring maize, cotton and forest/fruit trees, vegetable and paddy, and made the agricultural land use map of the North China Plain(NCP). Agricultural land use area accounted for 63.32% compared to the total area of the NCP in 2002. And it increased to 65.66% in 2012, which mainly caused by the vegetables and forest/fruit trees increasing. Planting areas of winter wheat–summer maize, cotton, single spring maize, forest/fruit trees, vegetables and paddy were 5031.21×10~3, 865.90×10~3, 1226.10×10~3, 1271.17×10~3, 648.02×10~3, 216.51×10~3 ha in 2012. Rank of changes was: vegetables(+45%) forest/fruit trees(+27.4%) paddy(–23.7%) cotton(–20.4%) single spring maize(+17.3%) winter wheat–summer maize(–0.6%). In developed region like Beijing and Tianjin, planting area of crops with high economic benefit(such as fruit trees and vegetables) increased significantly. Government policies for groundwater protection caused obvious decline of winter wheat cultivation in Hebei Province. Cotton planting in Shandong Province decreased more than 200,000 ha during 2002–2012. The data products will be published in the website: http://hydro.sjziam.ac.cn/Default.aspx. To clarify the agricultural land use in the NCP will be very helpful for the regional agricultural water consumption research, which is the serious problem in the NCP.  相似文献   

10.
To study the distribution characteristics and variation regularity of the temperature field during the process of seepage freezing,a simulated-freezing test with seepage of Xuzhou sand was completed by using a model test developed in-house equipment.By means of three group freezing tests with different seepage velocities,we discovered the phenomenon of the asymmetry of the temperature field under the influence of seepage.The temperature upstream was obviously higher than that downstream.The temperature gradient upstream was also steeper than that downstream.With a higher seepage velocity,the asymmetry of the temperature field is more pronounced.The asymmetry for the interface temperature profile is more strongly manifest than for the main surface temperature profile.The cryogenic barrier section is somewhat"heartshaped".With the increasing velocity of the seepage flow,the cooling rate of the soil decreases.It takes much time to reach the equilibrium state of the soil mass.In our study,seepage flow velocities of 0 m/d,7.5 m/d,and 15 m/d showed the soilcooling rate of 4.35°C/h,4.96°C/h,and 1.72°C/h,respectively.  相似文献   

11.
Based on biomass investigations, soil respiration and plant photosynthesis measurement of dominant trees in Hailuogou valley of Mt. Gongga, Southwest China, the carbon (C) storage, absorption and release for several typical woodlands in sub-alpine zones have been discussed. For Abies fabri forest of 3,000 m above sea level, the C storage amount is 177.4 t/ha for above-ground biomass and 143.2 t/ha for soil below-ground biomass. The annual gross C fixed by vegetation photosynthesis is 20-24 t/ha. The C release by canopy respiration is 3.0-5.5 t/ha for arbors and 10-19 t/ha for surface soil and roots. The annual net C fixed of forest ecosystem is about 6.0-7.1 t/ha. At lower elevations, the amount of C released by woodlands is higher than that of woods at higher elevations. The C fixed capacity of renewed forest with middle-aged trees is higher than that of mature forest. Before becoming over-matured forest, woodland is an important sink of C whereas bareland in woods is the source of atmospheric C.  相似文献   

12.
Based on biomass investigations, soil respiration and plant photosynthesis measurement ofdominant trees in Hailuogou valley of Mt. Gongga, Southwest China, the carbon (C) storage,absorption and release for several typical woodlands in sub-alpine zones have been discussed. ForAbies fabri forest of 3,000 m above sea level, the C storage amount is 177.4 t/ha for above-groundbiomass and 143.2 t/ha for soil below-ground biomass. The annual gross C fixed by vegetationphotosynthesis is 20-24 t/ha. The C release by canopy respiration is 3.0-5.5 t/ha for arbors and 10-19t/ha for surface soil and roots. The annual net C fixed of forest ecosystem is about 6.0-7.1 t/ha. Atlower elevations, the amount of C released by woodlands is higher than that of woods at higherelevations. The C fixed capacity of renewed forest with middle-aged trees is higher than that of matureforest. Before becoming over-matured forest, woodland is an important sink of C whereas bareland inwoods is the source of atmospheric C.  相似文献   

13.
贡嘎山亚高山林地碳的积累与耗散特征   总被引：15，自引：0，他引：15  
程根伟  罗辑 《地理学报》2003,58(2):179-185
根据贡嘎山海螺沟内5种主要林地上的生物量调查、土壤呼吸和光合作用测定,研究亚高山地区典型林带上C的存贮、吸收和排放关系。对于海拔3000 m附近的峨眉冷杉林,其地上和地下C贮量分别为177.4 t/hm2和143.2 t/hm2,森林光合作用吸收的C量在22～24 t/hm2·a之间,通过呼吸释放C量为3～5.5 t/hm2·a (乔木冠层) 和10～19 t/hm2·a (地面土壤及根系),年光合作用净固定的C为7.05 t/hm2。低海拔处生态系统C的呼吸量较大,100a以内的中幼龄树木固C能力高于成熟林的固C作用。林地在成为过熟林之前主要还是C的汇,林间裸地是大气的C源。  相似文献   

14.
干旱区油蒿生物量凋落分解与土壤呼吸   总被引：7，自引：7，他引：0  
生物量的凋落分解与土壤呼吸影响流沙基质中CaCO3的淋溶和淀积。为研究腾格里沙漠油蒿群落中土壤CaCO3的形成,对油蒿当年生物量的凋落分解与土壤呼吸进行了探讨。结果表明：在腾格里沙漠,固定沙地上油蒿当年生物量[（41.51±1.76）g·m-2]显著高于半固定沙地[（32.31±0.92)g·m-2],固定沙地上油蒿叶量籽量和[（32.89±1.34)g·m-2]也显著高于半固定沙地[（19.32±0.64)g·m-2];但不同立地油蒿叶量和籽量的分解速率均大于0.6692 g·g-1·a-1,且油蒿的凋落物需要4.48 a才能达到分解最大值。另一方面,油蒿半固定沙地、油蒿固定沙地和油蒿+冷蒿固定沙地的土壤呼吸速率均存在显著差异;统计分析表明,油蒿+冷蒿固定沙地土壤呼吸速率最低[（7.37±1.07)mg CO2·m-2·h-1]可能与油蒿+冷蒿固定沙地土壤中较高的pH值和较低的土壤呼吸脱氢酶活性有关。可见,干旱区油蒿群落越到固定阶段,凋落量越大,释放的Ca2＋越多,土壤呼吸速率越低,土壤中的pH值越高,而这越有利于土壤中CaCO3的形成。  相似文献   

15.
The National Forest Inventory (NFI) is an important resource for estimating the national carbon balance (These data were unpublished data, and we could only obtain the data before 2008 through data search by now). Based on the data from sample plots, the literature, and NFI, as well as the relationships between volume, biomass, annual litterfall and soil respiration of different forest types, the net ecosystem production (NEP), changes in forest biomass carbon storage (△Cbiomass) and non-respiratory losses (NR) of China’s forests during 1999-2008 were estimated, and the forest soil carbon sequestration (△Csoil) was assessed according to the carbon balance principle of the forest ecosystem (△Csoil = NEP - NR - △Cbiomass). The results showed that the total NEP, △Cbiomass, NR and △Csoil values for China’s forests were 157.530, 48.704, 31.033 and 77.793 Tg C yr-1 respectively, and average NEP, △Cbiomass, NR, and △Csoil values were 101.247, 31.303, 19.945 and 49.999 g C m-2 yr-1 respectively. There were large spatial differences in forest soil carbon sequestration in different parts of China. The forest soil in Jiangxi, Hunan, Zhejiang, Fujian, Anhui, Shanxi, Shaanxi, Guangxi and Liaoning served as carbon sources and the carbon released was about 25.507 Tg C yr-1. The other 22 provinces served as carbon sinks and the average carbon sequestration by forest soil came to 103.300 Tg C yr-1. This research established a method for evaluating soil carbon sequestration by China’s forests based on the NFI, which is a useful supplement to current statistical data-based studies on the forest ecosystem carbon cycle, and can promote comparable studies on forest soil carbon sequestration with consistent research methods at the regional scale.  相似文献   

16.
为了研究古尔班通古特沙漠荒漠-绿洲过渡带区域龟裂土立地条件下免灌人工梭梭林生态特征,探讨林分的最佳建植密度,对莫索湾1983—2021年38 a集水造林地初始种植梭梭、梭梭自然更新苗及不同坡位的土壤水分进行了调查,研究了梭梭生长对密度差异的响应,同时分析了各林地土壤水分的变化特征,探讨了梭梭生长与土壤水分的关系,以期为人工梭梭林的营建与可持续性提供科学依据。结果表明：（1） 当梭梭造林密度为6 m×3.5 m时（480 株·hm-2）,母树存活率最高。随造林密度增大,母树保存率与梭梭自然更新比逐渐下降;母树保留密度越大的林地,其长势越差、生物量越低;盖度、郁闭度越高的林地,阻碍浅层土壤水分的补给,导致梭梭更新苗长势及生物量越差。（2） 梭梭母树的林木生长与其根部140~280 cm深度土壤含水量之间均呈显著负相关（P<0.05）,且主要利用根部140~240 cm土壤水分,对比3个林地可知该层土壤水分含量越高的林地,其母树的长势越好、生物量越高。（3） 当母树保留密度为360株·hm-2（株行距4 m×7 m）时,梭梭长势较好、整体生物量最高,林下植被更为丰富,林地土壤水分条件相对较好。综上所述,在该地区进行集水造林时,保持该密度更有利于免灌人工梭梭林结构稳定、持续发挥防风固沙效益。  相似文献   

17.
北京森林碳储量海拔梯度上的变化趋势(英文)   总被引：2，自引：0，他引：2  
像北京这样的中国城市化地区的快速人口和GDP增长已经导致了来自化石燃料的大量CO2排放。森林被认为是最重要的碳汇,可以中和碳排放。本研究基于2009年森林清查数据和森林植被碳含量,采用生物量扩展因子(BEFs)方法评价了北京森林植被碳储量,利用森林凋落物与森林生物量的比例以及凋落物碳含量计算了凋落物碳储量,利用土壤厚度、容重和SOM含量计算了土壤碳储量。我们总结得出,阔叶林是北京森林主要碳库,森林碳储量主要分布在海拔60m的平原地区和60-600m的低山地区。北京森林碳密度几乎随着海拔增加而增加,但是在海拔200-400m地区略有下降,其中植被碳密度在60m的平原地区相对较高,这主要是由于碳密度较高的杨树和落叶松人工林的比例较高以及灌溉、施肥等促进植物碳累积的人工管理措施较多;森林土壤碳密度几乎随着海拔增加而增加,这主要是由于土壤碳输出随着海拔增加而逐渐下降,因为林下种植、灌溉和施肥加速了低海拔地区的土壤异氧呼吸但随着海拔增加而下降,同时海拔200-800m的低山地区常见的土壤侵蚀也会随着林下种植等干扰措施的减少而下降。本研究可以为区域森林生态系统管理者提供保护森林生态系统和改善森林碳储量提供科学知识。  相似文献   

18.
山顶苔藓矮林是中国西南地区热带、亚热带高山顶部一类重要而特殊的湿性常绿阔叶林,附生植物非常发达,其中以分解、半分解枯死残留物为主的林冠腐殖土是山地森林生态系统一个重要的养分库。以云南哀牢山山顶苔藓矮林为对象,对其林冠腐殖土及林下0～10 cm,10～20 cm和20～40 cm地表不同深度土壤的营养元素含量、微生物生物量及呼吸速率等进行了分析和测定。结果表明,该山顶苔藓矮林中林冠腐殖土中有机C、全N、全Ca、全P和全Na的含量,水解N、NH4+-N与NO3—N以及速效K、速效P的含量明显地高于林下地表各层土壤;在土壤微生物生物量C、N和呼吸速率方面,雨季大于旱季,林冠腐殖土明显高于林下地表冠层土壤,而且随着林地土层深度的增加,其养分含量和生化活性出现出显著下降的趋势。林冠腐殖土较高的养分含量和生化活性在林冠繁茂的附生植物生长发育和维持林冠附生植物多样性格局方面具有重要的生态功能。  相似文献   

19.
放牧对内蒙古羊草群落土壤呼吸的影响   总被引：11，自引：0，他引：11  
马涛  董云社  齐玉春  徐福利  彭琴  金钊 《地理研究》2009,28(4):1040-1046
采用静态暗箱法,比较测定了放牧对内蒙古锡林河流域羊草群落土壤呼吸的影响以及水热等相关环境因子与土壤呼吸的关系。结果表明:放牧没有改变羊草群落土壤呼吸的季节性变化特征,但降低了土壤呼吸速率的年幅度;生长季放牧样地土壤呼吸速率显著低于封育样地,非生长季两样地土壤呼吸强度均处于较低水平,而且出现负通量的现象,放牧使羊草群落土壤呼吸年总量下降了约33.95％;从全年来看,无论是围栏还是放牧样地,封育样地和放牧样地土壤呼吸与温度因子均显著正相关(p<0.01,n=15),其中与10cm处地温相关性最好,但放牧降低了土壤呼吸对温度变化的敏感性;生长季水分影响作用高于温度,围栏封育样地0~10cm土壤含水量的变化可以解释土壤呼吸变异的87.4％,放牧样地10~20cm和20~30cm土壤含水量的变化共同可以解释土壤呼吸变异的74.9％。  相似文献   

20.
汤洁  刘畅  杨巍  李昭阳  吴佳曦 《地理科学》2012,(10):1247-1253
应用SWAT模型对辽宁省大伙房水库汇水区农业非点源污染进行了模拟,利用2006~2009年的水文和水质监测数据对模型进行率定与验证。研究结果表明:研究区泥沙坡面产量为15.40×104t,属于微度侵蚀,其中耕地的土壤侵蚀模数最高,为475.84 t/(km2.a),疏林地次之,灌林地、有林地的土壤侵蚀模数较小;汇水区农业非点源氮、磷产生量分别为1 248.83 t和102.88 t;不同土地利用类型氮、磷的产生量差异较大,耕地远远高于林地等其他类型。总体上,流域农业非点源污染的产生量浑河流域高于苏子河流域,社河流域最小,且河流上游地区高于下游。研究结果揭示了研究区农业非点源污染空间分布特性,可以为水土保持和非点源污染防治提供基础支持。  相似文献   

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