Soil erosion rates and characteristics of typical alpine meadow using <Superscript>137</Superscript>Cs technique in Qinghai-Tibet Plateau

Alpine meadow is the predominant ecosystem in Qinghai-Tibet Plateau.The firm turf of alpine meadow formed by sub-surface anfractuous roots can be effective in conserving water and soil.Alpine meadow is a primary contributor to the Chinese Water Tower.For quantitative assess anti-erosion ability of alpine meadow,this paper selected three typical meadow slopes with>60% vegetation coverage to evaluate soil erosion rates using 137Cs.The results showed that(1)soil erosion intensity of typical alpine meadow was slight to light.Erosion rates were 464 t km–2 a–1 in Malong Village,415 t km–2 a–1 in Yeniugou Town and 875 t km–2 a–1 in Zhenqin Town respectively;(2)soil erosion rates were correlated negatively with vegetation coverage,and the relationship was clearer at the slope scale than plot scale;(3)the relationship between soil erosion and vegetation coverage showed that vegetation coverage was a predominant factor in retaining soil and water on slopes.With complete turf and high vegetation coverage, alpine meadow was of great significance for soil conservation and prevention of soil erosion.     

Relations between the underground biomass and soil organic carbon and nitrogen of the alpine meadow at the Eastern Margin of the Qinghai-Tibet Plateau

This article, by combining field investigation with laboratorial analysis, studies diverse alpine meadow at the Eastern Margin of the Qinghai-Tibet Plateau for the underground biomass dynamics, vertical distribution of the content of soil carbon and nitrogen, the connection between the biomass and the content of carbon and nitrogen. The studies show that underground biomass in the herb layer of upland meadow is more than that in the terrace meadow, while underground biomass in the upland shrubland is the most. The vertical distribution of underground biomass of each type is obvious as in shape of＂T＂. As to the distribution of the content of soil organic carbon in the three sample grounds, it showed that the deeper the soil the less the content of soil organic carbon. In May, unlike at terrace meadow, the underground biomass and the content of soil organic carbon in positive proportion, such revelation at upland meadow and upland shrubland is not apparent. In July, at upland meadow and terrace meadow the underground biomass and the content of soil total nitrogen in positive proportion, such revelation at upland shrubland is not apparent either.     

Distribution characteristics of soil organic matter and total nitrogen on the Yajiageng vertical belt,Gongga Mountain around the Dadu River banks

Distribution characteristics of soil organic matter（SOM） and total nitrogen（TN） were studied in different plant communities of the Yajiageng vertical belt in Gongga Mountain around the Dadu River banks. The results show： （1） the contents of SOM and TN of the plant communities gradually decreased with the following order： subalpine coniferous forest （3 027 m）, subalpine meadow （3 873 m）, coniferous broadleaved mixed forest（2 737 m）, subalpine shrub（3 565 m） and treeline（3 564 m）. （2） With soil profile depth increasing, the contents of SOM and TN gradually decreased. For different vegetation types, the contents of SOM and TN in sub-alpine coniferous forest were higher than that of other vegetational types. （3）The ratio of the content of carbon to the content of total nitrogen （Cc/CTN）WaS 13.5-27.6, which was relatively lower than the appropriate Cc/CTN of 25-30, and indicated that the soil in favor of the organic matter decomposed and nutrients released. Cc/CTN in the soil had no correlation with sea level altitude. However, its distribution in the soil x, aried with different vegetation types. （4） Nitrogen in SOM existed mainly in the form of organic nitrogen, and Cc/CTN in the soil was not obvious correlated with SOM and TN.     

Impacts of Soil Moisture Content and Vegetation on Shear Strength of Unsaturated Soil

It is analyzed that the impacts of vegetation type and soil moisture content on shear strength of unsaturated soil through direct shearing tests for various vegetation types, different soil moisture contents and different depth unsaturated soil. The results show that the cohesion of unsaturated soil changes greatly, and the friction angle changes a little with soil moisture content, h is also shown that vegetation can improve shear strength of unsaturated soil, which therefore provides a basis that vegetation can reinforce soil and protect slopes.     

Effect of land use on microbial biomass－C, －N and －P in red soils

Eleven red soils varying in land use and fertility status were used to examine the effect of land useon microbial biomass -C, -N and -P. Microbial biomass-C in the red soils ranged from about 68 rag C/kg to 225 mg C/kg, which is generally lower than that reported from other types of soil, probably because of low or-ganic matter and high acidity in the red soils. Land use had considerable effects on the amounts of soil Cmic.The Cmic was the lowest in eroded fallow land, followed by woodland, tea garden, citrus grove and fallow grassland, and the highest in vegetable and paddy fields. There was significant correlation between Cmic and organic matter content, suggesting that the influence of land use on Cmie is mainly related to the input and ac-cumulation of organic matter. Microbial biomass-N in the soils ranged from 12.1 Nmg/kg to 31.7 Nmg/kg andwas also affected by land use. The change of Nmic with land use was similar to that of Cmic. The microbial C/N ratio ranged from 5.2 to 9.9 and averaged 7.6. The Nmic was significantly correlated with soil total N and available N. Microbial biomass-P in the soils ranged from 4.5 mg P/kg to 52.3 rag P/kg. The microbial C/P ratio was in the range of 4-23. The Pmic was relatively less affected by land use due to differences in fertili-zation practices for various land use systems.     

Impacts of climate change on ecosystem in Priority Areas of Biodiversity Conservation in China

Priority Areas of Biodiversity Conservation （PABCs） are the key areas for future biodiversity conservation in China. In this study, we used 5 dynamic global vegetation models （DGVMs） to simulate the ecosystem function changes under future climate change scenario in the 32 terrestrial PABCs. We selected vegetation coverage, vegetation productivity, and ecosystem carbon balance as the indicators to describe the ecosystem function changes. The results indicate that woody vegetation coverage will greatly increase in the Loess Plateau Region, the North China Plain, and the Lower Hilly Region of South China. The future climate change will have great impact on the original vegetation in alpine meadow and arid and semiarid regions. The vegetation productivity of most PABCs will enhance in the coming 100 years. The largest increment will take place in the southwestern regions with high elevation. The PABCs in the Desert Region of Inner Mongolia-Xinjiang Plateau are with fastest productivity climbing, and these areas are also with more carbon sink accumulation in the future. DGVM will be a new efficient tool for evaluating ecosystem function changes in future in large scale. This study is expected to provide technical support for the future ecosystem management and biodiversity conservation under climate change.     

Dynamic of Grassland Biomass in Different Degenerative Stages

The dynamics of plant community and above- and belowground biomass of the different degenerative stages was researched of Kobresia hurnlis meadows of Nakchu prefecture in Tibet Autonomous Region. The results indicated that the aggravation of the degree of deterioration of alpine meadow is, the lower the vegetation coverage, percentage of excellent forage, and biodiversity are. The total aboveground biomass is highest in the lightly degraded stages while it is lowest in the extremely degraded stages. With the aggravation of degradation, the aboveground biomass of forbs increases while that of Cyperaceae decreases. We found that the belowground biomass was mostly distributed in the 0-10 cm soil depth in the alpine meadow with a ＂T＂-shape distribution feature, and with the acceleration of deterioration, the numbers of roots becomes less and less. Meanwhile, the above- and belowground biomass of the different degraded communities was significantly correlated（r= 0. 963）. There is an obvious positive correlation with the above- and belowground biomass in different degenerative stages, and their ratio increased with the aggravation of degradation.     

Influences of the degradation of swamp and alpine meadows on CO2 emission during growing season on the Qinghai-Tibet Plateau

CO2 emission fluxes of two types of ecosystem, swamp meadow and alpine meadow, in the Fenghuo- shan region of the Qinghai-Tibet Plateau were studied by the static chamber-portable infrared chro- matographic method. The results showed that there was large difference in the CO2 emission fluxes between the two ecosystems and in the same ecosystem of different degradation degrees. CO2 emis- sion flux of the swamp meadow gradually decreased with increasing degradation degree, while that of the alpine meadow gradually increased with increasing degradation degree except in May. The CO2 emission flux of undegraded swamp meadow was 65.1%―80.3% higher than that of undegraded alpine meadow; and the CO2 emission flux of moderately degraded swamp meadow was 22.1%―67.5% higher than that of alpine meadow; but the CO2 emission flux of severely degraded alpine meadow was 14.3%―29.5% higher than that of swamp meadow. The soil moisture content and temperature in the upper 5 cm soil layer and above-ground biomass were significantly correlated with the CO2 emission fluxes and regarded as the main environment factors to control the CO2 emission.     

Extracting change information of land use and soil erosion based on RS & GIS technologystration

Rapid landuse change has taken place in many arid regions of China such as Yulin prefecture over the last decade due to rehabilitation measures. Landuse change and soil erosion dynamics were investigated by the combined use of remote sensing and geographic information systems (GIS). The objectives were to determine landuse transition rates and soil erosion change in Yulin prefecture over 15 years from 1986 to 2000. Significant changes in landuse and soil erosion occurred in the area over the study period. The results show the significant decrease in barren land mainly due to conversion to grassland. Agricultural land increased associated with conversions from grassland and barren land. The area of water erosion and wind erosion declined. The study demonstrates that the integration of satellite remote sensing and GIS is an effective approach for analyzing the direction, rate, and spatial pattern of landuse and soil erosion change.     

Three-year changes of surface albedo of degraded grassland and cropland surfaces in a semiarid area

Diurnal, seasonal and interannual variations of surface albedo of degraded grassland and cropland surfaces at a semiarid area of Tognyu have been investigated based on the continuous three years observational data from 2003 to 2005. The changes of surface albedo with solar elevation angle and soil moisture have been discussed also. It has been found that surface albedo has almost the same diurnal and seasonal variations on degraded grassland and cropland surfaces in the semiarid area, while surface albedo is large in winter and small in summer. The diurnal variation of the surface albedo has relationship with the weather condition. The diurnal cycle of the surface albedo likes the ＂U＂ shape curve in sunny day, while it is low-high after the rain, and high-low after the snow. The surface albedo has large variation in cloudy day, while it has no any variation in overcast day. The large difference of the surface albedo can be 0.04 in winter between two land surfaces, because the snow has large effects on the surface albedo in winter. The rainfall is an important factor in summer on the surface albedo, while the difference of the surface albedo is 0.01 only between two land surfaces. The differences of the surface albedo can also be 0.04 in autumn due to vegetation growing. The seasonal-average surface albeo from 2003-2005 is 0.25, 0.22, 0.24, 0.32 respectively in spring, summer, autumn and winter on the degraded grassland surface, while it is 0.25, 0.21,0.22, 0.33 respectively in spring, summer, autumn and winter on the cropland surface. The surface albedo becomes smaller with the increase of solar elevation angle. When the solar elevation angle is greater than 40°, the surface albedo changes very little and tends to be a constant. The surface albedo has negative exponent functions with soil moisture in the growing season.     

退化喀斯特植被不同恢复阶段土壤质量变化

为探讨退化喀斯特生态系统植被恢复对土壤质量的改良效果。本文对花江流域退化喀斯特植被不同演替阶段的土壤的石砾含量、含水量、容重、持水量、孔隙度、pH值、有机质、全氮、全磷、全钾、碱解氮及速效P、K等理化指标进行测定分析。结果表明:植被恢复促进了喀斯特山地土壤pH值降低、控制了土壤pH值的上升。土壤石砾含量随植被恢复而下降;有机质含量随植被恢复而上升。在整个演替的过程中,全氮、全磷、全钾、碱解氮及速效P、K含量随植被的恢复而呈波动变化的趋势;土壤质量的生境变化总体上表现为石沟较高。综合分析表明,研究区植被恢复总体上促进了土壤理化质量的提高。     

不同退化程度高寒草地土壤有机碳分布特征

在青海省三江源区选择了甘德县青珍乡高寒草甸和玛多县花石峡镇高寒草原典型样区,各划分5种不同退化程度样地(未退化、轻度退化、中度退化、重度退化和极度退化),分层采集0~10,10~20和20~30 cm不同深度土层样品,分析土壤有机碳含量。结果表明:研究区内高寒草地土壤表土有机碳含量及有机碳密度均随退化程度的加剧和土层的加深呈显著下降,各退化程度间均差异极显著(P0.01)。与原生植被相比,轻度退化、中度退化、重度退化和极度退化下0~30 cm土层有机碳含量在青珍样地分别平均降低了21.7%,38.8%,67.4%和79.6%,花石峡样地分别平均降低了19.4%,44.4%,67.0%和79.7%。表层土壤有机碳及有机碳密度在生态系统退化下变化剧烈,不同土层不同退化程度高寒草甸土壤有机碳含量及有机碳密度均高于高寒草原草地,估计退化下土壤有机碳密度平均下降了16 t/hm2,累积退化下表土有机碳损失可能在12 Pg以上。     

青海河南高寒草地生态系统健康评价

以青海省河南县高寒草地为研究区域,从"植被状况-土壤状况-干扰状况-生态系统价值"4个方面的17个指标构建高寒草地生态系统健康评价体系(目标层A、准则层B、因子层C).利用层次分析法确定评价体系中各指标权重,最后利用综合指数法进行高寒草地生态系统健康评价.结果表明:准则层中植被和土壤状况所占权重较大,分别为0.453 4和0.298 4,在高寒草地生态系统健康评价体系中占有主要地位,其中,因子层土壤有机质、地上生物量和植被盖度权重较大,分别为0.168 2,0.164 9,0.164 9,对高寒草地生态系统健康影响显著,虫口密度、土壤碳储能力和牧草生产对草地生态系统健康影响较小,其权重分别为0.007 5,0.010 5,0.010 5.青海河南高寒草地生态系统健康状况评价较好,除样地7外皆属于健康之列.但样地3和样地5评分较低,偏向恶化.应在草地处于初级退化阶段时,积极采取保护措施.     

伊犁河上游典型草地生态系统氮磷含量及化学计量特征

【目的】了解伊犁河上游典型草地养分限制状况,为不同草地类型群落营养循环及植物-土壤养分管理提供理论依据,也为该区域生态环境的改善提供科学依据。【方法】通过野外调查采样和室内分析测定,采用相关性分析方法,分析了不同类型草地群落植物-土壤氮、磷、钾含量及化学计量学特征。【结果】研究区不同草地类型植物群落植物地上部分和地下部分根系的氮、磷、钾含量变异较大,山地草甸草原和高寒草甸植物地上部分氮含量荒漠草原、半荒漠草原和高寒草甸的氮含量;荒漠草原和半荒漠草原植物地下部分根系的氮含量山地草甸草原、山地草甸和高寒草甸的氮含量;不同草地群落类型植物地上部分的P含量与植物N/P比值呈显著负相关,土壤N与土壤P含量、土壤P含量与土壤N/P比值分别呈显著正相关,土壤N和土壤N/P比值极显著相关,其相关系数为0.983。【结论】研究区土壤氮素缺乏,可以考虑在草地生长过程中适当添加氮肥。     

坝上高原不同土地利用类型耕层土壤含水量对比——以康保县为例

分别在坝上高原康保县3个综合农业区相互毗邻的耕地、草地、灌木林地和乔木林地4种不同土地利用类型地块进行土壤采样,测定距地表约20 cm、30 cm耕层土壤水分百分比,结合野外考察、农户走访,对比分析了不同土地利用类型地块耕层涵养土壤水的能力.结果表明:耕地和草地土壤含水量普遍高于乔木林地,灌木林地居中;留茬耕地高于春翻耕地;留茬耕地和草地约20 cm深土层土壤含水量普遍低于30 cm深处,乔木林地与之相反,灌木林地无明显规律.建议在生态恢复重建中重点还草还灌植被,注重草灌乔混交模式;耕地采用保护性留茬,晚翻耕或免耕.     

川西北高寒草甸生长季土壤氮素动态

研究了川西北高寒草甸生长季土壤氮素变化特征,结果表明:研究区0～40 cm土层在整个生长期内,有机质含量均高于60 g.kg-1,全氮含量高于2.83 g.kg-1,养分含量丰富.浅丘山地草甸土壤氮素随季节变化呈现增加的趋势,植被覆盖变化(浅丘山地灌丛)或退化程度增加(丘前阶地草甸)使得土壤氮素随季节呈现出先减少后缓慢增加的变化,但影响主要表现在0～30 cm土层中,并且越往表层,差异越大.川西北高寒草甸土壤C/N值偏小(<25),利于氮的矿化养分释放.由于研究样地中灌丛的出现,虽然没有引起明显的"沃岛"现象,但加大土壤养分空间异质性的趋势.     

水分迁移对高山草甸区非冻结路基土的影响

高山草甸区域内道路冻胀、翻浆等病害大量发生,水分迁移是产生冻胀翻浆病害的主要原因.为了研究初始含水率、细颗粒含量及入流通量对非冻结路基土中水分迁移的影响.依托拉妥至芒康公路改建工程,进行室内试验.结果表明:当土体处于最佳含水率时,不同细颗粒含量的土样毛细水上升高度不同;在一定细颗粒含量范围内,土体总入流量及入流通量随细颗粒含量的增加而增大;当初始含水率为11％时,细颗粒含量为19％的土样总入流量随时间变化曲线表现为"S"形,而细颗粒含量为22％的土样却表现为拱形,说明土样总入流量随时间变化曲线随着细颗粒含量的增加,土样同样出现滞后现象.土体总入流量及入流通量与初始含水率成反比,总入流量随时间变化曲线由拱形变化为"S"形.结果表明高山草甸区的最低路基填筑高度控制在1.5 m以上,能有效防治路基冻胀翻浆.研究成果可对西藏高山草甸区公路建设与养护提供科学的依据和指导意义.     

若尔盖高寒草甸不同功能群植物数量特征对退化演替的响应

为了查明若尔盖高寒草甸退化过程中植物群落各功能群数量特征的变化趋势,2013年8月利用样方法对若尔盖县境内的沼泽草甸、草原草甸、中度退化草甸和重度退化草甸的植物群落和土壤环境进行了调查.结果为:草地退化过程中,禾本科植物密度、高度和重要值均无显著变化,仅盖度呈显著波动性变化;莎草科植物密度、高度、盖度在中度退化前均无显著变化,重度退化阶段显著降低,重要值呈持续显著下降趋势;豆科植物高度和盖度以中度退化阶段最高,但密度和重要值以草原草甸最高,重度退化阶段最低;蓼科植物密度、高度、盖度和重要值从沼泽草甸到中度退化阶段均显著增加,重度退化阶段消失;杂类草植物密度和盖度在退化过程中呈波动变化,高度和重要值呈波动性增加趋势.结果表明:高寒草甸不同退化阶段功能群植物的生长规律不尽相同,但严重退化可显著影响莎草科、豆科、蓼科和禾本科的生长.回归分析表明土壤氮、磷、钾含量是莎草科、豆科和蓼科的主要限制因子,这意味着向退化高寒草甸中同时施加氮、磷、钾三种肥料将可以促进莎草科、豆科和蓼科植物的生长,有利于高寒草甸生态恢复.     

河北坝上地区不同土地利用类型的土壤风蚀研究

通过137Cs示踪和土壤粒度分析,着重探讨了河北坝上地区土地利用与土壤风蚀的关系,揭示了不同土地利用类型的侵蚀强度为沙质丘陵草原耕地退耕还草地人工林石质丘陵草原,提出了对研究区保持石质丘陵草原现状、保护原有人工林等植被恢复的建议。