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121.
122.
Biological soil crust development and its topsoil properties in the process of dune stabilization, Inner Mongolia, China 总被引:4,自引:0,他引:4
This study was undertaken at Horqin Sand Land, Inner Mongolia, Northern China. Field samples of biological soil crusts (BSCs)
and underlying topsoil (0–5 cm under BSC) were taken in areas of different dune stabilization stages, and their physicochemical
properties were analyzed, including particle size distribution, bulk density, organic matter, nitrogen, phosphorus, electrical
conductivity (EC), pH, and CaCO3 content. The results revealed that semi-mobile dunes, semi-fixed dunes and fixed dunes had developed a physical crust, algae
crust and moss crust, respectively. The thickness, hardness, water content, fine fraction and nutrient contents of BSCs were
gradually increasing along the dune stabilization gradient. Meanwhile, BSC establishment and development enhanced the bulk
density, silt and clay content, and nutrients of the topsoil under it, in an increasing tend from semi-mobile dune to fixed
dune. Organic matter concentrations and other nutrients in the 0–5 cm topsoil layer under BSCs were significantly higher compared
to unconsolidated soil (control). Moreover, there were strong significant positive correlations between topsoil and BSCs’
organic matter, total nitrogen, available nitrogen, available phosphorus, CaCO3, and <0.05 mm particle content, suggesting that BSCs have an influence on some of the properties of the underlying topsoil. 相似文献
123.
内蒙古科右中旗—突泉地区出露一套缺少化石、遭受接触变质作用的巨厚层碎屑岩,其先后被划归为早二叠世索伦组、晚二叠世林西组、下寒武统。取自该套地层砂岩样品的碎屑锆石LA-ICP-MS U-Pb定年数据表现为2个主要年龄区间:255~354Ma,峰值年龄为263Ma和283Ma;413~529Ma,峰值年龄为485Ma。另有5颗锆石的年龄值分别为625Ma、965Ma、1372Ma、1707Ma、1727Ma。263Ma的峰值年龄限定了该套地层的沉积下限应为晚二叠世,结合区域地层对比,认为是晚二叠世林西组。该地层年代为突泉盆地下伏第二低阻层为林西组的推断提供了年代学证据。 相似文献
124.
125.
Soil Moisture Effects on Sand Saltation and Dust Emission Observed over the Horqin Sandy Land Area in China 下载免费PDF全文
In this study, the effects of soil moisture on the processes of sand saltation and dust emission are investigated using observations from three dust events in 2010 over Horqin Sandy Land area. The minimum friction velocity initiating the motion of surface particles, namely threshold friction velocity, is estimated to be 0.34, 0.40 and 0.50 m s-1, under the very dry, dry and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission flux during the wet event is smaller, but the saltation activities of sand particles (d ≥ 50 μm) are stronger. The size distributions of airborne dust particles (0.1 ≤ d ≤ 20 μm) show that the finer dust particles (0.1 ≤ d ≤ 0.3 μm) have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have larger size, and hence more potential saltating particles are available. This explains the phenomena of stronger saltation processes observed under wet soil conditions. 相似文献
126.
在科尔沁沙地测定分析了流动沙丘栽植樟子松林23 a后的土壤碳截存作用,以及林地和流动沙丘土壤呼吸对干湿变化的响应。结果表明:①流动沙丘造林后土壤容重减小,土壤颗粒中极细沙和黏粉粒含量显著增加;②樟子松林地0~5 cm和5~15 cm层土壤有机碳截存量分别为221.8 g·m-2和113.9 g·m-2,截存速率分别为9.64 g·m-2·a-1和4.95 g·m-2·a-1;CaCO3-C截存量分别为4.0 g·m-2和2.5 g·m-2, 截存速率分别为0.17 g·m-2·a-1和0.11 g·m-2·a-1;③干旱条件下土壤呼吸随气温的升高呈现指数减小;无论是干旱还是降雨后,林地土壤呼吸速率均显著高于流动沙丘;④降雨刺激后土壤呼吸显著增加,林地增加的幅度显著高于流动沙丘;林地地表凋落物去除后土壤呼吸速率下降,并且在降雨后下降更为明显。 相似文献
127.
植被覆盖度是监测生态系统及其功能的关键参数,如何提高大区域植被覆盖度的反演精度,对生态脆弱区环境可持续发展至关重要。本研究基于人工神经网络、支持向量回归和随机森林等机器学习方法,利用无人机、Worldview-2与Landsat 8 OLI遥感数据,对科尔沁沙地植被覆盖度进行多尺度反演。结果表明:随机森林模型比人工神经网络、支持向量回归模型表现佳,可在单元(试验区)、区域(研究区)尺度上较高精度地反演沙地的植被覆盖度,反演值与无人机实测值均在线性水平上呈显著相关(P<0.01);在单元、区域尺度上,构建的植被覆盖度反演模型测试集R2分别为0.84、0.80,MSE分别为0.0145、0.0370,一致性指数d分别为0.9576、0.8991。利用多源遥感数据和机器学习方法,通过局部区域的高精度反演逐步实现低空间分辨率遥感影像的大区域植被覆盖度反演,不仅可有效提高沙地植被覆盖度的反演精度(R2=0.78,大于0.63),也为区域生态环境监测与生态系统健康评价提供支持。 相似文献
128.
科尔沁沙地不同生境土壤氮矿化/硝化作用研究 总被引:6,自引:4,他引:2
利用顶盖埋管原位培育法测定了科尔沁沙地不同生境(丘间低地、固定、半固定、半流动和流动沙丘)土壤氮素矿化/硝化速率的月际动态及净矿化/硝化量。结果表明:①沙地土壤无机氮主要以NO-3-N的形式存在,各类生境土壤NH+4-N平均含量比NO-3-N低58.2%~79.7%;②土壤氮素矿化/硝化速率随植被与土壤条件的恶化呈现递减的趋势,从丘间低地到流动沙丘,净矿化速率分别为61.0、43.4、29.1、5.3 mg·m-2·d-1和2.7 mg·m-2·d-1,净硝化速率分别为61.8、46.2、30.1、6.2 mg·m-2·d-1和3.4 mg·m-2·d-1;③从丘间低地到固定、半固定、半流动和流动沙丘,矿化氮总量分别减少28.8%、52.3%、91.4%和95.5%,硝化总量分别减少25.3%、51.3%、90.0%和94.5%;④不同类型生境土壤净硝化氮占净矿化氮的比例都为100%,表明沙地土壤中植物可利用氮素易于淋溶或氨挥发损失。 相似文献
129.
科尔沁沙地典型地区人工造林对沙漠化过程的影响 总被引:4,自引:2,他引:2
在3S技术的支持下,以奈曼旗1975年、1985年、1995年和2005年的遥感影像为信息源,分析了研究区近30 a人工造林对沙漠化过程的影响。结果表明,在持续的人工造林过程影响下,沙地面积呈现出持续减少的趋势,其中固定沙丘面积减少幅度尤为显著,面积净减量为39 545.77 hm2;沙漠化程度指数呈现出线性减少的变化趋势,自1985年以来,减少幅度尤为明显,由1985年的0.21下降到2005年的0.03;土地沙漠化正、逆过程同时存在,但逆转趋势远大于发展趋势,土地沙漠化过程总体上正处于全面逆转期;斑块数和景观形状指数均呈现出先增后减的变化趋势,斑块形状经历简单—复杂—简单的变化过程。 相似文献
130.
Xiaoan Zuo Halin Zhao Xueyong Zhao Yirui Guo Jianying Yun Shaokun Wang Takafumi Miyasaka 《Environmental Geology》2009,58(6):1227-1237
The Horqin Sandy Land is one of the most severely desertified regions in northern China. Plant communities and soil conditions
at five stages of grassland desertification (potential, light, moderate, severe and very severe) were selected for the study
of vegetation pattern variation relating to soil degradation. The results showed that vegetation cover, species richness and
diversity, aboveground biomass (AGB), underground biomass, litter, soil organic carbon (C), total nitrogen (N), total phosphorus
(P), electrical conductivity, very fine sand (0.1–0.05 mm) content and silt (0.05–0.002 mm) content decreased with the desertification
development. Plant community succession presented that the palatable herbaceous plants gave place to the shrub species with
asexual reproduction and sand pioneer plants. The decline of vegetation cover and AGB was positively related to the loss of
soil organic C and total N with progressive desertification (P < 0.01). The multivariate statistical analysis showed that plant community distribution, species diversity and ecological
dominance had the close relationship with the gradient of soil nutrients in the processes of grassland desertification. These
results suggest that grassland desertification results in the variation of vegetation pattern which presents the different
composition and structure of plant community highly influenced by the soil properties. 相似文献