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1.
《干旱区科学》2017,(2)
Greenhouse gas(GHG) emissions from the surface soils and surface water receiving animal excreta may be important components of the GHG balance of terrestrial ecosystems, but the associated processes are poorly documented in tropical environments, especially in tropical arid and semi-arid areas. A typical sylvo-pastoral landscape in the semi-arid zone of Senegal, West Africa, was investigated in this study. The study area(706 km2 of managed pastoral land) was a circular zone with a radius of 15 km centered on a borehole used to water livestock. The landscape supports a stocking rate ranging from 0.11 to 0.39 tropical livestock units per hectare depending on the seasonal movements of the livestock. Six landscape units were investigated(land in the vicinity of the borehole, natural ponds, natural rangelands, forest plantations, settlements, and enclosed plots). Carbon dioxide(CO_2), nitrous oxide(N_2O) and methane(CH_4) fluxes were measured with static chambers set up at 13 sites covering the six landscape units, and the 13 sites are assumed to be representative of the spatial heterogeneity of the emissions. A total of 216 fluxes were measured during the one-year study period(May 2014 to April 2015). At the landscape level, soils and surface water emitted an average 19.8 t C-CO_2 eq/(hm2·a)(CO_2: 82%, N_2O: 15%, and CH_4: 3%), but detailed results revealed notable spatial heterogeneity of GHG emissions. CO_2 fluxes ranged from 1148.2(±91.6) mg/(m2·d) in rangelands to 97,980.2(±14,861.7) mg/(m2·d) in surface water in the vicinity of the borehole. N_2O fluxes ranged from 0.6(±0.1) mg/(m2·d) in forest plantations to 22.6(±10.8) mg/(m2·d) in the vicinity of the borehole. CH_4 fluxes ranged from –3.2(±0.3) mg/(m2·d) in forest plantations to 8788.5(±2295.9) mg/(m2·d) from surface water in the vicinity of the borehole. This study identified GHG emission "hot spots" in the landscape. Emissions from the surface soils were significantly higher in the landscape units most frequently used by the animals, i.e., in the vicinity of the borehole and settlements; and emissions measured from surface water in the vicinity of the borehole and from natural ponds were on average about 10 times higher than soil emissions. 相似文献
2.
Methane(CH4), carbon dioxide(CO2) and nitrous oxide(N2O) are known to be major greenhouse gases that contribute to global warming. To identify the flux dynamics of these greenhouse gases is, therefore, of great significance. In this paper, we conducted a comparative study on an alpine grassland and alpine wetland at the Bayinbuluk Grassland Eco-system Research Station, Chinese Academy of Sciences. By using opaque, static, manual stainless steel chambers and gas chromatography, we measured the fluxes of CH4, N2O and CO2 from the grassland and wetland through an in situ monitoring study from May 2010 to October 2012. The mean flux rates of CH4, N2O and CO2 for the experimental alpine wetland in the growing season(from May to October) were estimated at 322.4 μg/(m2?h), 16.7 μg/(m2?h) and 76.7 mg/(m2?h), respectively; and the values for the alpine grassland were –88.2 μg/(m2?h), 12.7 μg/(m2?h), 57.3 mg/(m2?h), respectively. The gas fluxes showed large seasonal and annual variations, suggesting weak fluxes in the non-growing season. The relationships between these gas fluxes and environmental factors were analyzed for the two alpine ecosystems. The results showed that air temperature, precipitation, soil temperature and soil moisture can greatly influence the fluxes of CH4, N2O and CO2, but the alpine grassland and alpine wetland showed different feedback mechanisms under the same climate and environmental conditions. 相似文献
3.
内蒙古草原土壤斥水性的季节变化 总被引：2，自引：0，他引：2
土壤斥水性是指水分不能或很难湿润土壤颗粒表面的物理现象,具有斥水性的土壤称为斥水土壤。本文以内蒙古锡林浩特市白音锡勒牧场中国科学院内蒙古草原生态系统定位站的羊草样地为例,运用滴水穿透时间法分析了1979年禁牧1、999年禁牧、冬季放牧和连续放牧等条件下内蒙草原土壤斥水性的季节变化。结果表明:草原土壤总体上表现为轻度斥水性或无斥水性,且斥水性具有显著的季节变化特点,一般在雨季或多雨年土壤具有较强的斥水性;不同的利用方式对草原土壤斥水性的季节变化规律具有一定的影响,存在时间上的滞后性,持续放牧处理在雨季较多的样点最先表现斥水性,其次为冬季放牧处理,然后为1999年禁牧处理,最后为1979年禁牧处理。 相似文献
4.
内蒙古是我国风力侵蚀较为严重的地区之一,同时也是我国土地利用方式剧烈变化的地区之一。依据两期土地利用数据以及相应年代的土壤风力侵蚀数据,研究了20世纪90年代内蒙古自治区土地利用和风力侵蚀的静、动态格局。根据土地利用和风力侵蚀的空间分布及动态变化特点,设计了内蒙古土地利用—风力侵蚀动态区划,基于该区划详细讨论了内蒙古不同地区占主导地位的土地利用动态与风力侵蚀动态,由此揭示了两者之间存在的驱动——被驱动关系。研究发现,在过去10年里,内蒙古土地利用和风力侵蚀的基本格局没有太大变化,但风力侵蚀在总体上是增强了,而土地利用的变化主要反映为草地的退化和耕地的扩张。土地利用动态与风力侵蚀动态有着良好的时空对应关系草地的退化与耕地的扩张导致了显著的风力侵蚀增强,而草地的改善以及耕地的收缩对风力侵蚀的影响不是很大,这同时也表明了土地利用动态对风力侵蚀动态正、反向驱动力的不平衡性。 相似文献
5.
SOC storage and potential of grasslands from 2000 to 2012 in central and eastern Inner Mongolia,China 总被引：1，自引：0，他引：1
《干旱区科学》2016,(3)
Grassland ecosystem is an important component of the terrestrial carbon cycle system. Clear comprehension of soil organic carbon(SOC) storage and potential of grasslands is very important for the effective management of grassland ecosystems. Grasslands in Inner Mongolia have undergone evident impacts from human activities and natural factors in recent decades. To explore the changes of carbon sequestration capacity of grasslands from 2000 to 2012, we carried out studies on the estimation of SOC storage and potential of grasslands in central and eastern Inner Mongolia, China based on field investigations and MODIS image data. First, we calculated vegetation cover using the dimidiate pixel model based on MODIS-EVI images. Following field investigations of aboveground biomass and plant height, we used a grassland quality evaluation model to get the grassland evaluation index, which is typically used to represent grassland quality. Second, a correlation regression model was established between grassland evaluation index and SOC density. Finally, by this regression model, we calculated the SOC storage and potential of the studied grasslands. Results indicated that SOC storage increased with fluctuations in the study area, and the annual changes varied among different sub-regions. The SOC storage of grasslands in 2012 increased by 0.51×1012 kg C compared to that in 2000. The average carbon sequestration rate was 0.04×1012 kg C/a. The slope of the values of SOC storage showed that SOC storage exhibited an overall increase since 2000, particularly for the grasslands of Hulun Buir city and Xilin Gol League, where the typical grassland type was mainly distributed. Taking the SOC storage under the best grassland quality between 2000 and 2012 as a reference, this study predicted that the SOC potential of grasslands in central and eastern Inner Mongolia in 2012 is 1.38×1012 kg C. This study will contribute to researches on related methods and fundamental database, as well as provide a reference for the protection of grassland ecosystems and the formulation of local policies on sustainable grassland development. 相似文献
6.
Deserts are sensitive to environmental changes caused by human interference and are prone to degradation. Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand. However, the effects of grazing, which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification, on the greenhouse gas (GHG) fluxes from soils remain unknown. Herein, we investigated GHG fluxes in the Hobq Desert, Inner Mongolia Autonomous Region of China, at the mobile (desertified), fixed (vegetated), and grazed (re-desertified) sites from January 2018 to December 2019. We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential (GWP). CO2 was emitted at an average rate of 4.2, 3.7, and 1.1 mmol/(m2•h) and N2O was emitted at an average rate of 0.19, 0.15, and 0.09 µmol/(m2•h) at the grazed, fixed, and mobile sites, respectively. Mean CH4 consumption was as follows: fixed site (2.9 µmol/(m2•h))>grazed site (2.7 µmol/(m2•h))>mobile site (1.1 µmol/(m2•h)). GHG fluxes varied seasonally, and soil temperature (10 cm) and soil water content (30 cm) were the key micrometeorological factors affecting the fluxes. The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO2 and N2O emissions and decreased CH4 absorption. Grazing also significantly increased the GWP of the soil (P<0.05). This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage. These findings could be used to formulate informed policies on the management and utilization of desert ecosystems. 相似文献
7.
通过分析内蒙古草原生态补偿标准存在的问题,确定内蒙古草原生态补偿标准应该包含三方面的内容：直接成本、机会成本和草原生态服务功能价值。根据内蒙古经济社会发展现状及草原生态退化程度确定内蒙古草原生态补偿应处于第三个阶段,即＂补偿标准=直接成本＋全部机会成本＂,并以内蒙古禁牧为例,以全国城镇居民人均可支配收入和农村居民人均纯... 相似文献
8.
With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate and the magnitude of the conversion in Inner Mongolia is among the national highest where the areal extent of planted grasslands ranks the second in China. Such land-use changes(i.e., converting natural grasslands into planted grasslands) can significantly affect carbon stocks and carbon emissions in grassland ecosystems. In this study, we analyzed the effects of converting natural grasslands into planted grasslands(including Medicago sativa, Elymus cylindricus, and M. sativa+E. cylindricus) on ecosystem respiration(F_(eco)) in Inner Mongolia of China. Diurnal F_(eco) and its components(i.e., total soil respiration(F_(ts)), soil heterotrophic respiration(F_(sh)) and vegetation autotrophic respiration(F_(va))) were measured in 2012(27 July to 5 August) and 2013(18 July to 25 July) in the natural and planted grasslands. Meteorological data, aboveground vegetation data and soil data were simultaneously collected to analyze the relationships between respiration fluxes and environmental factors in those grasslands. In 2012, the daily mean F_(eco) in the M. sativa grassland was higher than that in the natural grassland, and the daily mean F_(va) was higher in all planted grasslands(i.e., M. sativa, E. cylindricus, and M. sativa+E. cylindricus) than in the natural grassland. In contrast, the daily mean F_(ts) and F_(sh) were lower in all planted grasslands than in the natural grassland. In 2013, the daily mean F_(eco), F_(ts) and F_(va) in all planted grasslands were higher than those in the natural grassland, and the daily mean F_(sh) in the M. sativa+E. cylindricus grassland was higher than that in the natural grassland. The two-year experimental results suggested that the conversion of natural grasslands into planted grasslands can generally increase the F_(eco) and the increase in F_(eco) is more pronounced when the plantation becomes more mature. The results also indicated that F_(sh) contributed more to F_(eco) in the natural grassland whereas F_(va) contributed more to F_(eco) in the planted grasslands. The regression analyses show that climate factors(air temperature and relative humidity) and soil properties(soil organic matter, soil temperature, and soil moisture) strongly affected respiration fluxes in all grasslands. However, our observation period was admittedly too short. To fully understand the effects of such land-use changes(i.e., converting natural grasslands into planted grasslands) on respiration fluxes, longer-term observations are badly needed. 相似文献
9.
Yibo ZHANG 《干旱区科学》2017,9(6):810-822
Due to increasing global demand for crop production and energy use, more and more reactive nitrogen(Nr) has been generated and emitted to the environment. As a result, global atmospheric nitrogen(N) deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA(DEnuder for Long Term Atmospheric sampling) system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH_3, NO_2, HNO_3, particulate NH_4~+(pNH_4~+) and particulate NO_3~-(pNO_3~-) in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m3, respectively, and that the annual mean volume-weighted concentrations of NH_4~+-N and NO_3~--N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components(including NH_3, NO_2, HNO_3, p NH_4~+, pNO_3~-, NH_4~+-N and NO_3~--N) exhibited different seasonal variations. Specifically, NO_2 and HNO_3 exhibited higher concentrations in autumn than in summer, while the other Nr components(NH_3, pNH_4~+, pNO_3~-, NH_4~+-N and NO_3~--N) showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/(hm~2·a) for NH_3, NO_2, HNO_3, p NH_4~+ and pNO_3~-, respectively, and the calculated annual mean wet/bulk deposition fluxes were 5.37 and 3.15 kg N/(hm~2·a) for NH_4~+-N and NO_3~--N, respectively. The estimated annual N deposition(including dry N deposition and wet/bulk N deposition) reached 14.7 kg N/(hm~2·a) in grassland of Duolun County, approaching to the upper limit of the N critical load(10–15 kg N/(hm~2·a)). Dry and wet/bulk deposition fluxes of all Nr components(with an exception of HNO_3) showed similar seasonal variations with the maximum deposition flux in summer and the minimum in winter. Reduced Nr components(e.g., gaseous NH_3 and p NH_4~+ in atmosphere and NH_4~+-N in precipitation) dominated the total N deposition at the sampling site(accounted for 64% of the total N deposition), suggesting that the deposited atmospheric Nr mainly originated from agricultural activities. Considering the projected future increases in crop and livestock production in Inner Mongolia, the ecological and human risks to the negative effects of increased N deposition could be increased if no mitigation measures are taken. 相似文献
10.
内蒙古温带草地植被的碳储量 总被引：18，自引：3，他引：18
草地生态系统在全球碳循环中起着极为重要的作用。大部分草地碳储存在地下,但是实测数据十分匮乏,因此准确估算温带草地植被碳储量对评价草地生态系统碳循环具有重要意义。作为一个区域性资料积累工作,作者对内蒙古温带草地的碳储量进行了大范围的实测研究,以估算该地区草地植被的碳储量。主要结果如下:(1)内蒙古温带草地总面积为58.46×106hm2,总植被碳储量为226.0±13.27Tg C(1 Tg=1012g),平均碳密度为3.44Mg C.hm-2;(2)地下根系储存的碳是地上碳储量的6倍左右,地上、地下生物量碳储量分别为33.22±1.75和193.88±12.6 Tg C,平均碳密度分别是0.51和2.96 MgC.hm-2;(3)不同草地类型的碳储量差异较大,典型草原最大(113.25 Tg C),占草地总碳储量的50%,其次是草甸和草甸草原,荒漠草原碳储量最低(15.37 Tg C)。 相似文献
11.
Grassland degradation is influenced by climate change and human activities, and has become a major obstacle for the development of arid and semi-arid areas, posing a series of environmental and socio-economic problems. An in-depth understanding of the inner relations among grassland vegetation dynamics, climate change, and human activities is therefore greatly significant for understanding the variation in regional environmental conditions and predicting future developmental trends. Based on MODIS (moderate resolution imaging spectroradiometer) NDVI (normalized difference vegetation index) data from 2000 to 2020, our objective is to investigate the spatiotemporal changes of NDVI in the Xilin Gol grassland, Inner Mongolia Autonomous Region, China. Combined with 12 natural factors and human activity factors in the same period, the dominant driving factors and their interactions were identified by using the geographic detector model, and multiple scenarios were also simulated to forecast the possible paths of future NDVI changes in this area. The results showed that: (1) in the past 21 a, vegetation cover in the Xilin Gol grassland exhibited an overall increasing trend, and the vegetation restoration (84.53%) area surpassed vegetation degradation area (7.43%); (2) precipitation, wind velocity, and livestock number were the dominant factors affecting NDVI (the explanatory power of these factors exceeded 0.4). The interaction between average annual wind velocity and average annual precipitation, and between average annual precipitation and livestock number greatly affected NDVI changes (the explanatory power of these factors exceeded 0.7). Moreover, the impact of climate change on NDVI was more significant than human activities; and (3) scenario analysis indicated that NDVI in the Xinlin Gol grassland increased under the scenarios of reduced wind velocity, increased precipitation, and ecological protection. In contrast, vegetation coverage restoration in this area was significantly reduced under the scenarios of unfavorable climate conditions and excessive human activities. This study provides a scientific basis for future vegetation restoration and management, ecological environmental construction, and sustainable natural resource utilization in this area. 相似文献
12.
土壤退化与草地退化关系的研究 总被引：40，自引：4，他引：40
内蒙古草原在畜牧业生产及环境生态上均占有重要的地位 ,但草地退化比较严重 ,土壤是草地生态系统的基础环境 ,土壤退化与草地退化关系十分密切 ,都受到自然因素与生产活动的影响 ,但土壤退化比草地上植被的退化缓慢 ,土壤具有较强的抗拒退化的能力 ,它是土壤性质的综合表现 ,可以称之为土壤稳定性 ,土壤的稳定性是支撑草地生产稳定和恢复的重要因素 ,在评价与改良退化草地时 ,要充分了解土壤的退化程度 ,引起退化的主导因子 ,因地制宜地采取措施才能收到良好的效果 相似文献
13.
草原是我国重要的自然资源,承担着生产、生态和生活等多种功能,在构建生态屏障、促进牧业经济以及维系社会稳定等方面具有重要意义。近几十年来,受全球气候变化和人为过度利用草原的共同影响,我国草原发生大范围退化。草原退化提高了啮齿动物栖息地适合度,促使其种群数量增加,最终导致草原鼠害发生。草原害鼠采食牧草降低草地生产力,掘洞造丘消弱草原固碳、水土保持等生态功能,携带病菌威胁人畜健康。因此,控制草原鼠害事关退化草原治理修复和社会经济的可持续发展。尽管国家开展了一系列草原鼠害研究和工程实践,取得了阶段性成果,但由于草原生态系统的复杂性和社会经济发展需求的不断提升,现有草原鼠害防治成果难以满足草原生态保护与建设的需求,相关理论和技术体系尚未完全形成,学科交叉、技术集成等亟待加强。本文总结了中国草原鼠害发生和防治的现状,并对草原鼠害防治存在的问题进行了讨论,最后从管理和技术层面对加强草原鼠害防治工作进行了展望。 相似文献
14.
内蒙古草原旅游资源及其开发研究 总被引：14，自引：4，他引：14
内蒙古拥有丰富的草原旅游资源 ,发展草原旅游对内蒙古旅游业与促进草原保护具有重要意义。本文在介绍内蒙古草原旅游资源类型的基础上 ,认为其具有视野开阔、夏季气候舒适、动植物种类多样、文化内涵丰富、景观相对单调、生态环境脆弱等特征 ,进而结合草原旅游开发中存在的问题与制约因素 ,提出内蒙古草原旅游资源主要有依托城市型、规模集聚型和独立点状型等 3种开发模式 ,并有针对性地阐述了内蒙古草原旅游资源开发的对策。 相似文献
15.
16.
呼伦贝尔退化草地植被演替特征研究 总被引：4，自引：1，他引：3
由于气候环境条件的变化和人类长期不合理的草地利用方式,致使呼伦贝尔草原退化、沙漠化趋势加剧,草地的退化严重威胁着当地的生态环境,制约着畜牧业的发展。对草甸草原、典型草原和沙地植被三种草地类型的植被退化演替特征研究结果表明:随着草地退化(沙化)程度加大,群落结构与多样性逐渐丧失,草层高度、植被盖度、株丛密度、地上部生物量等,都呈现不同程度的递减趋势,草地退化过程中,群落物种组成逐渐单一,数量逐渐减少,物种组成发生显著的变化。未退化草地以禾本科植物占主导地位,随着退化程度的加大,退化指示类的菊科植物的重要地位得到提升,中度退化阶段蔷薇科植物不断增加,并占据优势地位,重度退化阶段,多以耐践踏的蔷薇科植物和小型禾草为优势种,其中重度沙化草地,多年生植物几乎全部消失,而被一年生植物替代。 相似文献
17.
内蒙古典型草原区植被动态与植被恢复——以锡林郭勒盟典型草原区为例 总被引：2，自引：0，他引：2
内蒙古草原植被是一个极脆弱的生态系统,易受干旱等自然灾害影响。自1999年以来,全区大部分地区连续三年干旱和虫害(蝗灾),造成严重的草原退化和沙化。2002年后,内蒙古天然植被整体上有不同程度好转,草原生态环境有所改善。本文以锡林郭勒1999至2004年MODIS和TM影象数据和地面样点数据为依据,从宏观和微观两方面揭示了锡林郭勒草地植被动态规律和变化趋势,并系统分析了草地植被发生的变化原因、驱动因素和机理,阐明了锡林郭勒盟典型区草地所面临的问题,以期为我区草原植被恢复应采取的对策和措施提供依据。 相似文献
18.
Grazing is a main human activity in the grasslands of Xinjiang, China. It is vital to identify the effects of grazing on the sustainable utilization of local grasslands. However, the effects of grazing on net primary productivity(NPP), evapotranspiration(ET) and water use efficiency(WUE) in this region remain unclear. Using the spatial Biome-BGC grazing model, we explored the effects of grazing on NPP, ET and WUE across the different regions and grassland types in Xinjiang during 1979–2012. NPP, ET and WUE under the grazed scenario were generally lower than those under the ungrazed scenario, and the differences showed increasing trends over time. The decreases in NPP, ET and WUE varied significantly among the regions and grassland types. NPP decreased as follows: among the regions, Northern Xinjiang(16.60 g C/(m~2·a)), Tianshan Mountains(15.94 g C/(m~2·a)) and Southern Xinjiang(-3.54 g C/(m~2·a)); and among the grassland types, typical grasslands(25.70 g C/(m~2·a)), swamp meadows(25.26 g C/(m~2·a)), mid-mountain meadows(23.39 g C/(m~2·a)), alpine meadows(6.33 g C/(m~2·a)), desert grasslands(5.82 g C/(m~2·a)) and saline meadows(2.90 g C/(m~2·a)). ET decreased as follows: among the regions, Tianshan Mountains(28.95 mm/a), Northern Xinjiang(8.11 mm/a) and Southern Xinjiang(7.57 mm/a); and among the grassland types, mid-mountain meadows(29.30 mm/a), swamp meadows(25.07 mm/a), typical grasslands(24.56 mm/a), alpine meadows(20.69 mm/a), desert grasslands(11.06 mm/a) and saline meadows(3.44 mm/a). WUE decreased as follows: among the regions, Northern Xinjiang(0.053 g C/kg H_2O), Tianshan Mountains(0.034 g C/kg H_2O) and Southern Xinjiang(0.012 g C/kg H_2O); and among the grassland types, typical grasslands(0.0609 g C/kg H_2O), swamp meadows(0.0548 g C/kg H_2O), mid-mountain meadows(0.0501 g C/kg H_2O), desert grasslands(0.0172 g C/kg H_2O), alpine meadows(0.0121 g C/kg H_2O) and saline meadows(0.0067 g C/kg H_2O). In general, the decreases in NPP and WUE were more significant in the regions with relatively high levels of vegetation growth because of the high grazing intensity in these regions. The decreases in ET were significant in mountainous areas due to the terrain and high grazing intensity. 相似文献
19.
The rapid desertification of grasslands in Inner Mongolia of China poses a significant ecological threaten to northern China. The combined effects of anthropogenic disturbances(e.g., overgrazing) and biophysical processes(e.g., soil erosion) have led to vegetation degradation and the consequent acceleration of regional desertification. Thus, mitigating the accelerated wind erosion, a cause and effect of grassland desertification, is critical for the sustainable management of grasslands. Here, a combination of mobile wind tunnel experiments and wind erosion model was used to explore the effects of different levels of vegetation coverage, soil moisture and wind speed on wind erosion at different positions of a slope inside an enclosed desert steppe in the Xilamuren grassland of Inner Mongolia. The results indicated a significant spatial difference in wind erosion intensities depending on the vegetation coverage, with a strong decreasing trend from the top to the base of the slope. Increasing vegetation coverage resulted in a rapid decrease in wind erosion as explained by a power function correlation. Vegetation coverage was found to be a dominant control on wind erosion by increasing the surface roughness and by lowering the threshold wind velocity for erosion. The critical vegetation coverage required for effectively controlling wind erosion was found to be higher than 60%. Further, the wind erosion rates were negatively correlated with surface soil moisture and the mass flux in aeolian sand transport increased with increasing wind speed. We developed a mathematical model of wind erosion based on the results of an orthogonal array design. The results from the model simulation indicated that the standardized regression coefficients of the main effects of the three factors(vegetation coverage, soil moisture and wind speed) on the mass flux in aeolian sand transport were in the following order: wind speedvegetation coveragesoil moisture. These three factors had different levels of interactive effects on the mass flux in aeolian sand transport. Our results will improve the understanding of the interactive effects of wind speed, vegetation coverage and soil moisture in controlling wind erosion in desert steppes, and will be helpful for the design of desertification control programs in future. 相似文献
20.
Land use change significantly influences soil properties.There is little information available on the long-term effects of post-reclamation from grassland to cropland on soil properties.We compared soil carbon(C) and nitrogen(N) storage and related soil properties in a 50-year cultivation chronosequence of grassland in the agro-pastoral ecotone of Inner Mongolia.Field surveys on land use changes during the period of 1955-2002 were conducted to build a chronosequence of cropland of different ages since the conversion from grassland.The results showed that soil C and N storage,soil texture,and soil nutrient contents varied with land use types and cropland ages(P<0.01).In the 0-30 cm soil layer,the soil organic carbon(SOC) density was significantly lower in the croplands(3.28 kg C/m2 for C50 soil) than in the grasslands(6.32 kg C/m2).After 5,10,15,20,35,and 50 years of crop planting(years since the onset of cultivation),the SOC losses were 17%,12%,19%,47%,46%,and 48%,respectively,compared with the grasslands.The soil total nitrogen(TN) density of the grasslands was 65 g N/m2,and TN density of the cropland soil was 35 g N/m2 after 50 years of crop planting.Both the SOC and TN densities could be quantitatively determined by a negative exponential function of cropland age(P<0.0001,R2=0.8528;P<0.0001,R2=0.9637).The dissolved organic carbon(DOC) content,soil available potassium(AK) content,clay content,and pH value were decreased;and the soil bulk density and sand content were increased since the conversion of grassland into cropland during the 50-year period.Our results show soil nutrients were higher in grassland than in cropland.The conversion of grasslands to croplands induced a loss of soil C storage and changes of related soil properties.The reclamation time of cultivated soil(cropland age) had significant effects on soil properties in the study area. 相似文献