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1.
Potential of Desertification Control to Sequester Carbon and Mitigate the Greenhouse Effect 总被引：16，自引：0，他引：16
R. Lal 《Climatic change》2001,51(1):35-72
There is a strong link between desertification of the drylands and emission of CO2 from soil and vegetation to the atmosphere. Thus, there is a strong need to revisit the desertification process so that its reversal can lead to C sequestration and mitigation of the accelerated greenhouse effect. Drylands of the world occupy 6.31 billion ha (Bha) or 47% ofthe earth's land area distributed among four climates: hyper-arid (1.0 Bha), arid (1.62 Bha), semi-arid (2.37 Bha) and dry sub-humid (1.32 Bha). Principal soils of drylands are Aridisols (1.66 Bha), Entisols (1.92 Bha), Alfisols (0.38 Bha), Vertisols (0.21 Bha) and others (1.27 Bha). Drylands occur in all continents covering 2.01 Bha in Africa, 2.00 Bha in Asia, 0.68Bha in Australia, 1.32 Bha in the Americas and 0.30 Bha in Europe. Desertification, degradation of soil and vegetation in drylands resulting from climatic and anthropogenic factors, affects about 1.137 Bha of soils and an additional 2.576 Bha of rangeland vegetation. The rate of desertification is estimated at 5.8 million hectares (Mha) per year. Desertification is a biophysical process (soil, climate and vegetation) driven by socio-economic and political factors. The principal biophysical processes involved, accelerated soil erosion by water and wind and salinization, reduce soil quality and effective rooting depth, decrease vegetal cover, reduce biomass productivity, and accentuate vagaries of climateespecially low and variable rainfall. Major consequences of desertification include reduction in the total soil C pool and transfer of C from soil to the atmosphere. Total historic loss of C due to desertification may be 19 to 29 Pg. The rate of C emission from drylands due to accelerated soil erosion is estimated at 0.227 to 0.292 Pg C y–1. Therefore, desertification control and restoration of degraded soils and ecosystems would improve soil quality, increase the pool of C in soil and biomass, and induce formation of secondary carbonates leading to a reduction of C emissions to the atmosphere. Desertification control and soil restoration are affected by establishing vegetative cover with appropriate species, improving water use efficiency, using supplemental irrigation including water harvesting, developing a strategy of integrated nutrient management for soil fertility enhancement, and adopting improved farming systems. Adoption of these improved practices also have hidden carbon costs, especially those due to production and application of herbicides and nitrogen fertilizers, pumping irrigation water etc. Restoration of eroded and salt-affected soils is important to C sequestration. Total potential of C sequestration in drylands through adoption of these measures is 0.9 to 1.9Pg C y–1 for a 25- to 50-year period beyond which the rate of sequestration is often too low to be important. In addition to enhancing productivity and food security, C sequestration in soils and ecosystem has numerous ancillary benefits. Therefore, identification and implementation of policies is important to facilitate adoption of recommended practices and for commodification of carbon. 相似文献
2.
土壤有机质是土壤的重要组成部分,对许多土壤属性有重要影响.利用光谱技术进行土壤有机质的快速测定是实现精细农业的基础.近几十年中,高光谱技术的发展为土壤研究提供了新的手段.受土壤有机质质量分数、组成以及土壤水分、土壤质地的影响,室内光谱的估算结果总体较好;受大气、地表植被等影响,航空或卫星的成像光谱估算精度较低.星载成像技术的进步将在一定程度上提高土壤有机质的估算精度,为快速、大范围土壤有机质质量分数的遥感制图提供技术支持. 相似文献
3.
以黄河三角洲退化湿地人工引水恢复区为研究对象,采用野外植被调查、土壤采样结合室内实验方法,对植被的种类、密度、盖度、频度和重要值以及土壤含水量、pH值、有机质、全氮以及全磷等指标进行分析,旨在探讨人工引水恢复工程对黄河三角洲退化湿地所产生的生态效应。结果表明：随着水分条件的改善,恢复区植被呈现出正向演替;恢复区土壤含水量明显高于未恢复区,pH值则明显降低,土壤有机质含量高于未恢复区,土壤全氮、全磷含量变化不大。可见,引水恢复工程已经使退化湿地的生态环境得到了一定程度的改善,淡水资源仍是制约退化湿地恢复的关键因素。 相似文献
4.
This study examines spatial and time evolutions of the principal constituents of the
Tunisian background aerosols under Sirocco wind circulations. Aerosols coming from the Sahara
Desert were found to be loaded with particulate matter, especially silicon. The aerosols were
shown to have varying geochemical behaviour along the ``South-North" displacement of the Saharan
plumes, depending on the wind flow characteristics, geomorphologic features and the nature of
soils swept by the wind. In the south and the center part of the country, the transfer of aerosol
constituents to the soil (by gravity and/or impaction) was probably predominated by localized
enrichment phenomena. The latter are reinforced by the effect of turbulent winds over bare soils,
wind wakes and probably selective disintegration, especially in the vicinity of the geomorphologic
features of central Tunisia. These relatively high features, extending over important distances,
appear to be of paramount importance for the phenomena of redistribution of aerosol constituents
even during periods without Sirocco wind circulations. In the northern section of the country,
aerosol constituent concentrations dropped to almost 50%, in spite of the abundance of localized
turbulent winds. This may be explained by the effect of forests and the relatively dense vegetation
cover, which clearly reinforces the transfer phenomena to the soil and the attenuate of dust
entrainment. 相似文献
5.
The aim of this study was to generate a land productivity dynamics (LPD) map of a degraded catchment located in sub-humid terrestrial ecosystem via a land degradation assessment using three indicators, namely land use and land cover, land productivity, and soil organic carbon density. The study was carried out in two adjacent microcatchments located in Gediz River Basin and conducted between 2001 and 2015. For this purpose, Landsat satellite images were used to determine changing of land use and land cover and vegetation density. In addition, 319 soil samples were collected from surface and subsurface soil depths to detect soil organic carbon density of the study area in May 2015. According to the study results, in more than 23% of the catchments’ area of approx. 3896 ha, land productivity is observed to decline while about 24% shows early signs of decline level. Some of these areas used under agricultural cropping, overgrazed pasture, and artificial areas showed evidence of soil erosion problem. Only very small area of the catchment shows stable and increasing land productivity dynamics trend during the 14-year period. 相似文献
6.
利用1971-2016年青藏高原81个气象站逐月积雪日数和45个测站第一冻结层下界观测资料,分析了青藏高原积雪冻土的时空变化特征及其与高原植被指数（NDVI）的关系,探讨了积雪冻土下垫面变化对高原植被及沙漠化的可能影响。结果表明：1）青藏高原积雪日数分布极不均匀,巴颜喀拉山和唐古拉山为高原积雪日数的大值区,且年际变率较大。2）青藏高原积雪日数总体上呈现减少趋势,平均以3.5 d/（10 a）的速率减少,且在1998年前后发生突变,减少速率进一步加快,达到5.1 d/（10 a）。3）青藏高原第一冻结层下界呈上升趋势,达到-3.7 cm/（10 a）,与青藏高原增暖紧密相关。4）青藏高原NDVI呈缓慢增加趋势,与高原气温、降水的增加趋势相一致,积雪冻土的变化对不同区域植被NDVI的影响有显著差异。在气候变暖背景下,形成的暖湿环境促进积雪消融、冻土下界提升,使土壤浅层含水量增加,有利于植被恢复和生长,其结果对高原土地沙漠化防治有一定参考作用。 相似文献
7.
沙尘暴天气数值预报系统及其预报效果检验 总被引：9，自引：3，他引：6
沙尘暴天气数值预报系统包括区域大气模式、陆面过程模式、风沙模式(包括风蚀、输送和沉降模式)和地理信息系统。用该系统对2002年3月20日和4月7日2次沙尘天气进行了预报试验,利用地面观测资料和卫星观测资料对模式输出的主要沙尘天气预报产品进行了对比分析。分析结果认为,沙尘暴天气数值预报系统对沙通量、尘通量和垂直积分质量有很好的预报能力,但仍需改进陆面参数和沙尘气溶胶的初始值。 相似文献
8.
Incorporating organic soil into a global climate model 总被引：3，自引：1，他引：2
Organic matter significantly alters a soil’s thermal and hydraulic properties but is not typically included in land-surface
schemes used in global climate models. This omission has consequences for ground thermal and moisture regimes, particularly
in the high-latitudes where soil carbon content is generally high. Global soil carbon data is used to build a geographically
distributed, profiled soil carbon density dataset for the Community Land Model (CLM). CLM parameterizations for soil thermal
and hydraulic properties are modified to accommodate both mineral and organic soil matter. Offline simulations including organic
soil are characterized by cooler annual mean soil temperatures (up to ∼2.5°C cooler for regions of high soil carbon content).
Cooling is strong in summer due to modulation of early and mid-summer soil heat flux. Winter temperatures are slightly warmer
as organic soils do not cool as efficiently during fall and winter. High porosity and hydraulic conductivity of organic soil
leads to a wetter soil column but with comparatively low surface layer saturation levels and correspondingly low soil evaporation.
When CLM is coupled to the Community Atmosphere Model, the reduced latent heat flux drives deeper boundary layers, associated
reductions in low cloud fraction, and warmer summer air temperatures in the Arctic. Lastly, the insulative properties of organic
soil reduce interannual soil temperature variability, but only marginally. This result suggests that, although the mean soil
temperature cooling will delay the simulated date at which frozen soil begins to thaw, organic matter may provide only limited
insulation from surface warming. 相似文献
9.
积雪季节变化特征的数值模拟及其敏感性试验 总被引：4，自引：0，他引：4
文中利用综合陆面模式 (ComprehensiveLandSurfaceModel,CLSM )对法国ColdePorte 1 993/ 1 994 ,1 994 / 1 995年及BOREASSSA OJP 1 994 / 1 995年积雪个例进行了模拟试验 ,通过模拟结果与观测资料的对比 ,检验了CLSM对积雪变化特征的模拟能力 ,并通过敏感性试验探讨了降雪密度、积雪持水量等积雪参数化方案及植被对积雪模拟可能产生的影响。结果表明 :(1 )CLSM能够准确地模拟出积雪的变化过程 ,对积雪的演变特征作出了合理的描述 ;(2 )降雪密度、积雪持水量参数化方案对积雪模拟结果均具有一定的影响 :降雪密度参数化主要对积雪深度的模拟产生影响 ;而积雪持水量参数化方案对积雪的演变过程 ,尤其是积雪的消融 ,具有重要的作用 ;(3)有、无植被存在的情况下 ,积雪 土壤系统的变化过程存在显著的差别 ,植被通过改变积雪 /土壤表面的能量平衡 ,对积雪及土壤的变化过程产生重要影响 :植被的存在有利于积雪的维持 ,使得积雪融化进程推迟 ,冻结土壤的增温明显偏慢 相似文献
10.
利用2种植物带(芦苇、香蒲与芦苇)对受非点源污染河水进行植物带处理污染物的降解效果模拟试验研究。结果表明,植物带处理污染物的降解效果明显优于无植物带,且以混合植物带效果最好。香蒲与芦苇植物带对COD、TN、TP和NH3-N去除率的周平均值分别为31.62%、37.84%、30.65%和34.31%。植物带能够截留地表径流中的颗粒物,提高水域中的溶解氧含量,对防止水土流失与改善流域水质均有显著作用。 相似文献
11.
Sensitivity of the Terrestrial Ecosystem to Precipitation and Temperature Variability over China 
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下载免费PDF全文 SUN Guo-Dong 《大气和海洋科学快报》2014,(5):382-387
In this study, the sensitivities of net primary production （NPP）, soil carbon, and vegetation carbon to precipitation and temperature variability over China are discussed using the state-of-the-art Lund-Potsdam-Jena dynamic global vegetation model （LPJ DGVM）. The im- pacts of the sensitivities to precipitation variability and temperature variability on NPP, soil carbon, and vegeta- tion carbon are discussed. It is shown that increasing pre- cipitation variability, representing the frequency of ex- treme precipitation events, leads to losses in NPP, soil carbon, and vegetation carbon over most of China, espe- cially in North and Northeast China where the dominant plant functional types （i.e., those with the largest simu- lated areal cover） are grass and boreal needle-leaved for- est. The responses of NPP, soil carbon, and vegetation carbon to decreasing precipitation variability are opposite to the responses to increasing precipitation variability. The variations in NPP, soil carbon, and vegetation carbon in response to increasing and decreasing precipitation variability show a nonlinear asymmetry. Increasing pre- cipitation variability results in notable interannual variation of NPP. The sensitivities of NPP, soil carbon, and vegetation carbon to temperature variability, whether negative or positive, meaning frequent hot and cold days, are slight. The present study suggests, based on the LPJ model, that precipitation variability has a more severe impact than temperature variability on NPP, soil carbon, and vegetation carbon. 相似文献
12.
Blowing dust is symptomatic of severe wind erosion and deterioration of soils in areas undergoing dessication and/or devegetation. Dust plumes on satellite images can commonly be traced to sources in marginally arable semiarid areas where protective lag gravels or vegetation have been removed and soils are dry, as demonstrated for the Portales Valley, New Mexico. Images from Landsat and manned orbiters such as Skylab and the Space Shuttle are useful for illustrating the regional relations of airborne dust plumes to source areas. Geostationary satellites such as GOES are useful in tracking the time-histories of episodic dust storms. These events sometimes go unrecognized by weather observers and are the precursors of long-term land degradation trends. In areas where soil maps and meteorological data are inadequate, satellite images provide a means for identifying problem areas where measures are needed to control or mitigate wind erosion. 相似文献
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15.
D. W. Sanders 《Climatic change》1986,9(1-2):33-42
About one third of the Earth's land surface lies in the arid and semi-arid regions. This area is important as in addition to supporting 600 million people, it produces much of the world's grain and a substantial amount of animal produce.However, much of this area is now either suffering, or is threatened by the processes of desertification.In this paper, seven different desertification processes—degradation of vegetative cover, wind erosion, water erosion, salinization, soil crusting and compaction, reduction in organic matter, and accumulation of toxic substances— are identified and their effects described.It is pointed out that these processes are usually closely interrelated, the occurrence of one frequently leading to the occurrence of one or more of the others. But whatever the process, the end result is the same—degraded land with a reduced productive capacity.The paper concludes by pointing out that desertification occurs due to man's influence on the environment and we must therefore look beyond the purely physical processes if we are to solve the problems of desertification. 相似文献
16.
By using Comprehensive Land Surface Model (CLSM), three snow cases, i.e., France Col de Porte 1993/1994, 1994/1995 and BOREAS SSA-OJP 1994/1995, were simulated. The simulated results were compared with the observations to examine the capability of the model to describe the evolutions of snow cover under two different land cover conditions. Several sensitivity experiments were performed to investigate the effects of the parameterization schemes of some snow cover internal processes and vegetation on the model results. Results suggest that the CLSM simulates the basic processes of snow cover accurately and describes the features of snow cover evolutions reasonably, indicating that the model has the potential to model the processes related to the snow cover evolution. It is also found that the different parameterization schemes of the snowfall density and snow water holding capacity have significant effects on the simulation of snow cover. The estimation of snowfall density mainly impacts the simulated snow depth, and the underestimation (overestimation) of the snowfall density increases (decreases) the snow depth simulated significantly but with little effect on the simulated snow water equivalent (SWE). The parameterization of the snow water holding capacity plays a crucial role in the evolution of snow cover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads to larger snow density and heat capacity by storing more liquid water in the snow layer, and makes the temperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holding capacity, contrary is the case. The results also show that the physical processes related to the snow cover variation are different, which are dependent on the vegetation existed. Vegetation plays an important role in the evolution of soil-snow system by changing the energy balance at the snow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover and delays the increase of underlying soil temperature. 相似文献
17.
风蚀起沙的影响因子及其变化特征 总被引：19，自引：4，他引：15
以敦煌地区的戈壁和绿洲为例,对地表土壤风蚀起沙的临界摩擦速度及其变化特征和风蚀起沙过程中地表土壤的粒子尺度分布及其对垂直尘粒通量的影响进行了分析研究。结果表明,地表土壤风蚀起沙的临界摩擦速度随土壤水分含量和植被覆盖度的增大而增大,随粒子尺度的变化是先减小后增大,在中间某一尺度处有一最小值;土壤的人工利用和管理对临界摩擦速度也有着相当大的影响,风蚀起沙过程中,地表土壤的粒子尺度分布随时间发生变化,瞬时的粒子尺度分布不同于平均的粒子尺度分布,利用前者计算得到的垂直尘粒通量对摩擦速度的变化更敏感,利用后者计算得到的垂直尘粒通量偏大。 相似文献
18.
半干旱区植被覆盖度对边界层气候热力影响的数值模拟 总被引：14，自引：0，他引：14
在陆－气相互作用的中小尺度系统研究中，水平非均匀下垫面的强迫作用是主要的物理过程。本文利用能量闭合二维陆面过程与大气边界层耦合模式，研究了我国西北半干旱地区（３８°Ｎ，１０５°Ｅ）夏季下垫面物理特征的变化对区域边界层气候的影响。结果表明：土壤湿度、植被覆盖度对局地环流和区域边界层气候的形成起着决定性的作用。模拟结果揭示了在半干旱地区大面积植树造林、提高植被覆盖度，可涵养土壤水分，改善局地生态环境，是人工持续改造干旱、半干旱荒漠地区局地气候的重要途径。 相似文献
19.
NUMERICAL SIMULATION OF THE INFLUENCE OF VEGETATION COVER FACTOR ON BOUNDARY LAYER CLIMATE IN SEMI-ARID REGION 总被引：2，自引：0，他引：2 下载免费PDF全文
下载免费PDF全文 A numerical model has been developed for simulating land-surface processes and atmosphericboundary layer climate of vegetation and desert in semi-arid region.Dynamically,thermal andhydrological processes take place in the atmospheric boundary layer.Vegetation and surface layerof soil are included in the soil-vegetation-atmosphere coupled system,in which,vegetation isconsidered as a horizontally uniform layer,soil is divided into 13 layers and the horizontaldifferences of variables in the system are neglected.The influence of local boundary layer climateby vegetation cover factor is simulated with the coupled model in the semi-arid region of NorthwestChina (around 38°N,105°E).Results indicate that due to significant differences of water andenergy budgets in vegetation and desert region,the air is colder and wetter over the vegetation andcorrespondingly an obvious local circulation in the lower atmosphere is formed.Simulating results also show that maximum updraft and downdraft occur around thevegetation-desert marginal area,where the dynamical and thermodynamical properties of PBL(Planetary Boundary Layer) are uncontinuous.It is stronger at daytime,weaker and reverse atnighttime.In the simulation,the moisture inversion phenomena are analyzed.Finally.theinfluences of vegetation cover factor exchange on local boundary layer climate are simulated.Thesimulating results bring to light that water may be conserved and improved by developing treeplanting and afforestation,and improving cover factor of vegetation in local ecoenvironment,andthis is an important way of transforming local climate in arid and semi-arid area.Results indicatethat the coupled model can be used to study the soil-vegetation-atmosphere interaction and localboundary layer climate. 相似文献
20.
半干旱区陆面模式参数对水分循环的敏感性研究 总被引：2，自引：0，他引：2
植被覆盖对陆气之间物质和能量交换过程具有极其重要的影响,但植被覆盖对于交换过程的影响因子很多,关系复杂.作者研究了各种植被因子对陆气之间水分循环的作用和相对重要性.首先通过单点NO-AH模式对吉林通榆农田下垫面2004年土壤和边界层各物理量进行模拟,并与观测结果比较和评价,肯定了单点NOAH模式模拟能力.使用这一模式进行敏感试验,将与植被有关的参数分别在其取值范围取较大与较小值,比较水分循环各物理量如土壤湿度、土壤蒸发、植被蒸腾等的变化情况.试验表明在各参数中植被气孔阻抗、根系深度、土壤湿度初值和反照率对水分循环的影响较大,而叶面积指数、粗糙度和冠层阻抗则影响较小. 相似文献