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1.
利用EOS/MODIS数据估算西藏藏北高原地表草地生物量 总被引：4，自引：0，他引：4
植被生物量作为一个重要的植被状态参数,其估算不仅对研究陆地生态系统植被生产量、碳循环、营养分配等方面具有重要意义,植被生物量的大小直接影响人类对地表植被的利用特点,而且影响其他的生物物理参量。各种不同空间分辨率、时间分辨率和波谱分辨率遥感数据的出现,使得实时监测大范围的植被生长成为可能。文中根据2004年8月至9月草地植被地面观测资料结合同期的EOS/MODIS卫星遥感数据建立了西藏藏北高原草地植被地上生物量、绿色干物质获得量与EOS/MODIS归一化植被指数(NDVI)、增强植被指数(EVI)之间的关系,并与影响草地植被空间分布的主要气候和高程要素之间的关系进行了分析。结果表明:在藏北高原NDVI较EVI能有效地估算草地地上生物量和绿色干物质获得量;藏北高原草地地上生物量与绿色干物质获得量的空间分布特征是从东南部到西北部逐渐减少,东南部部分地区每平方公顷的草地地上生物量在2000 kg以上,到西北部地区减少到200 kg以下。影响草地地上生物量空间分布的主要气候要素是降水,两者的相关系数为0.64,其次为温度,相关系数为0.44;草地植被地上生物量的空间分布与高程呈反比,即海拔越高的地段生物量越低。 相似文献
2.
Jeffrey L. Michalek John E. Colwell Norman E. G. Roller Nicole A. Miller Eric S. Kasischke William H. Schlesinger 《Climatic change》2001,48(2-3):417-425
Along the international border separatingthe U.S. (Arizona) and Mexico (Sonora), differencesin the grazing intensity of domestic livestock arecommonly presumed to have created a large differencein vegetation cover between the two countries. Thisvegetation difference is reportedly responsible for anextensive albedo and temperature discontinuity thatmay be affecting regional climate. In this study, weused Landsat Thematic Mapper data to examinetrans-border differences in these two biophysicalparameters. Albedo and radiant temperature estimateswere computed for 25 km-long (east-west) transectsthrough semi-desert grassland on each side of theborder at two different times of year. Only smallaverage trans-border differences in these parameterswere found, and in some cases average albedo andtemperature data were essentially equal on each sideof the border. In addition, we found significantspatial heterogeneity in conditions on both sides ofthe border. These results suggest that, based on asmall sample, it may be difficult to assess whetherthere are significant differences in biophysicalproperties of semi-arid grassland between Arizona andMexico in the vicinity of the border. We concludethat more extensive spatial and temporal sampling iscritical in assessing any possible trans-borderdifferences in average terrain conditions that mightaffect climate, and that this data must be coupledwith more extensive meteorological data to assesswhether a difference in climate also exists. 相似文献
3.
西北地区MODIS-NDVI指数饱和问题分析 总被引：6，自引：0，他引：6
为了了解西北地区MODIS-NDVI和MODIS-EVI两种植被指数的特点,本文利用美国NASA LP DAAC(Land Process Distributed Active Archive Center)2004年1~12月的250 m分辨率16天植被指数合成的MOD13 Q1数据集,对西北地区不同类型植被NDVI和EVI的特征进行分析,并对西北地区MODIS-NDVI饱和问题进行了初步研究。结果表明:NDVI和EVI对干旱—半干旱气候区植被覆盖度不高的植被类型描述能力相似,月际变化趋势一致。西北地区各种植被类型NDVI比EVI高,NDVI与EVI的差异总体上呈现从半荒漠、草原、农区到林区,随NDVI值的增加而增大的规律。对植被度覆盖度高的阔叶林和针叶林,在植被生长旺盛期,NDVI总在0.8附近波动,NDVI随植被的生长增加的很小,一直维持在一个高且平的范围内,不再能看出植被生长变化的现象,即饱和现象严重;而EVI表现良好,随着植被的生长而增加,能明显地反映出植被生长的季节变化。西北高寒草甸和陕西关中农业区NDVI也出现有不同程度的饱和,饱和时间因植被的不同从1~2月不等。0.8可作为NDVI饱和的阈值。NDVI饱和问题对卫星监测植被的研究和应用会产生误差,EVI能较好地解决NDVI的饱和问题。 相似文献
4.
Jennifer M. Mangan Jonathan T. Overpeck Robert S. Webb Carol Wessman Alexander F. H. Goetz 《Climatic change》2004,63(1-2):49-90
The Nebraska Sand Hills exist in a semi-arid climatic environment and the land surface is grassland growing on sandy soils. These soils have been periodically active throughout the Holocene, but are currently stabilized by the vegetation. However, a shift in climate could cause grassland death and eventual sand dune remobilization. Our studies used the CENTURY nutrient cycling and ecosystem model to investigate the impacts of drought, plant functional type, fire, grazing, and erosion on Nebraska Sand Hills vegetation and dune stability. Fire and grazing alone had little impact on the vegetation, but when combined with mild drought, biomass decreased. Overall biomass increased if one plant functional type was allowed to dominate the ecosystem. Addition of as little as 1 mm of erosion per year under current climate conditions decreases vegetation as much as a drought 20 percent drier than the worst of the 1930s drought years in Nebraska. 相似文献
5.
Aerodynamic parameters including the zero-plane displacement (d), roughness length (20), and friction velocity (u*) on the different underlying surfaces of heavy-grazing site, medium-grazing site, light-grazing site, no-grazing site, dune, inter-dune, grassland, rice paddy site, wheat site, soybean site, and maize site have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorologically observed data of dune and vegetation in the semi-arid area at Naiman, Inner Mongolia of China, conducted jointly by the Institute of Desert Research, Chinese Academy of Sciences and the National Institute of Agro-Environmental Sciences of Japan in 1990-1994. And their relationships between wind speed and Richardson number are analyzed. The aerodynamic characteristics of different man-made disturbed grassland ecosystems are also compared. Result shows that the vegetation coverage and the above-ground biomass decrease with the increase in man-made stress of the grassland. The roughness length for different underlying surfaces is closely related to vegetation height, above-ground biomass, and ground surface undulation, and Richardson number Ri is also its influencing factor. The friction velocity varies largely on different underlying surfaces, and it is positively proportional to wind speed and roughness length. The aerodynamic parameters of various times on the same underlying surface are different, too. Above results indicate that grassland and vegetation are of significance in preventing desertification, especially in the arid and semi-arid land ecosystems. And the results of this paper are also important for constructing the land surface physical process as well as regional climate model. 相似文献
6.
中国北方四类典型下垫面能量分配特征及其环境影响因子研究 总被引：1，自引：0，他引：1
中国北方疆域辽阔,多种植被类型交错分布,陆面过程较为复杂。研究该区域地表能量平衡及分配过程,有助于进一步了解其生态系统的生产力及气候变化。本文使用"中国北方协同观测实验"观测资料,选取中国北方四种植被类型——高寒草甸、荒漠草地、玉米农田及半干旱草地,在深入认识地表能量分配特征的基础上,讨论了环境因子对能量分配的影响。结果表明,上述四类典型下垫面能量闭合度在71%~91%,其中半干旱草地最大,玉米农田最小。从各能量分量与净辐射的比率来看,荒漠草地、半干旱草地净辐射主要通过感热形式加热大气,感热通量占净辐射的百分比分别为29%和36%;高寒草甸、玉米农田潜热通量占主导地位,其值分别占净辐射的42%和37%。影响各下垫面水热综合参数Bowen比的气象因子中,半干旱草地受地-气温差(R2=0.64)和饱和水汽压差(R2=0.56)的影响;玉米农田则主要受地-气温差(R2=0.52)的影响;荒漠草地地-气温差(R2=0.37)和平均风速(R2=0.23)是其主要影响因子。Bowen比与NDVI之间存在显著的指数关系(R2=0.74),且随NDVI的增大而减小。 相似文献
7.
分别对草甸、草原和荒漠3种草地类型进行了生物量的实测工作。根据同步的MODIS与AVHRR资料,应用ENVI软件提取出这两种传感器在3种草地类型上的植被指数：NDVI和RVI。经过统计分析得到两种传感器在3种草地类型上的生物量模型,从而建立起MODIS植被指数与草地生物量的相关关系,并对MODIS和AVHRR植被指数估产模型进行了评价与分析。 相似文献
8.
不同下垫面空气动力学参数的研究 总被引：7，自引：0，他引：7
文中利用中国科学院沙漠研究所与日本国家农业环境技术研究所合作于1990—1994年在中国内蒙古自治区奈曼市半干旱地区沙丘和植被区下垫面观测的微气象数据,根据Monin-Obukhov相似性理论,计算了重度干扰草原、中度干扰草原、轻度干扰草原、无干扰草原、沙丘、沙丘内地、草地、稻田、小麦田、大豆田和玉米田11种下垫面的空气动力学参数粗糙度长度z0,零平面位移d,摩擦速度u*,并分析了它们与水平风速u和Richardson数的关系,比较了不同人为干扰草原生态系统条件下的空气动力学特征。结果表明:地表生物量和覆盖率随着人为干扰强度的增加而减少。不同人为干扰下垫面的粗糙长度与生物量和植被高度以及地表起伏程度有着密切关系;Richardson数也是其影响因子。风速、粗糙度都与摩擦速度成正相关,但对于不同下垫面有所不同,从中可以看到草地对沙漠化有一定的防治作用。同一种下垫面不同时期的空气动力学参数也存在差异。这些结果对建立陆面过程和区域气候模式具有重要的意义。 相似文献
9.
Christopher Potter Peggy Gross Steven Klooster Matthew Fladeland Vanessa Genovese 《Climatic change》2008,90(3):269-282
A plant and soil simulation model based on satellite observations of vegetation and climate data was used to estimate the
potential carbon pools in standing wood biomass across all forest ecosystems of the conterminous United States up to the year
1997. These modeled estimates of vegetative carbon potential were compared to aggregated measurements of standing wood biomass
from the U. S. Forest Service’s national Forest Inventory and Analysis (FIA) data set and the Carbon Online Estimator (COLE)
to understand: 1) predominant geographic variations in tree growth rate and 2) local land cover and land use history including
the time since the last stand-replacing disturbance (e.g., from wildfire or harvest). Results suggest that although wood appears
to be accumulating at high rates in many areas of the U.S. (Northwest and Southeast), there are still extensive areas of relatively
low biomass forest in the late 1990s according to FIA records. We attribute these low biomass accumulation levels to the high
frequency of disturbances, which can be observed even in high production areas such as the Southeast due to frequent forest
harvests. Ecosystem models like the one presented in this study have been coupled with satellite observations of land cover
and green plant density to uniquely differentiate areas with a high potential for vegetative carbon storage at relatively
fine spatial resolution. 相似文献
10.
Lindsey Christensen Michael B. Coughenour James E. Ellis Zuo Zhong Chen 《Climatic change》2004,63(3):351-368
The vulnerability of grassland vegetation in Inner Mongolia to climate change and grazing was examined using an ecosystem model. Grazing is an important form of land use in this region, yet there are uncertainties as to how it will be affected by climate change. A sensitivity analysis was conducted to study the effects of increased minimum and maximum temperatures, ambient and elevated CO2, increased or decreased precipitation, and grazing on vegetation production. Simulations showed that herbaceous above ground net primary production was most sensitive to changes in precipitation levels. Combinations of increased precipitation, temperature, and CO2 had synergistic effects on herbaceous production, however drastic increases in these climate scenarios left the system vulnerable to shifts from herbaceous to shrub-dominated vegetation when grazed. Reduced precipitation had a negative effect on vegetation growth rates, thus herbaceous growth was not sustainable with moderate grazing. Shifts in temporal biomass patterns due to changed climate have potentially significant implications for grazing management, which will need to be altered under changing climate to maintain system stability. 相似文献
11.
The regional climate effects of vegetation change in arid and semi-arid regions of China, which has experienced serious grassland degradation, are investigated in this study using the Weather Research and Forecasting (WRF) regional climate model. Two long-term simulation experiments (from January 1, 1980 to March 1, 2010), one with the land cover derived from the original United States Geological Survey’s (USGS) data (denoted as CTL) and the other (denoted as SEN) with a modification of the former one by vegetation degradation in arid and semi-arid regions of China, are undertaken to investigate the influence of land cover change on regional climate over arid and semi-arid regions of China. The possible mechanisms of how land cover change affects the regional climate in arid and semi-arid regions of China are also examined. The simulation results indicate that when compared with the observation datasets, the WRF model simulates the spatial pattern of observed temperature and precipitation quite well. After vegetation degradation over the arid and semi-arid regions of China, the net radiation and evaporation are reduced mainly within the degraded areas in summer, consistent with the reduction in precipitation and the increase in 2-m air temperature (T2 m). 相似文献
12.
草地植被指数季节变化的遥感动态监测研究 总被引：1，自引：0，他引：1
利用EOS/MODIS卫星遥感数据,针对MODIS的应用特点,借鉴国内外基于遥感手段监测植被的方法以及植被指数的研究进展,探讨了草地变化动态监测的方式和方法。以乌鲁木齐地区为研究对象,用植被指数最大合成法,合成了该地区2004年4月至10月每个月的最大植被指数图。同时,利用每月合成的最大植被指数图,以乌鲁木齐南郊天山中段北坡的草地为典型研究区,通过典型区野外实地采样得到与MODIS影像资料时相一致的草地地上生物量数据,并利用ENVI软件提取出典型区各样点的植被指数值,分析了遥感植被指数与植被生物量的相关关系,从而建立起了植被指数在草甸和草原不同季节的生物量估测模型。 相似文献
13.
Our objective was to evaluate the transient responses of grasslands in the central grassland region of North America to changes in climate. We used an individual plant-based gap dynamics simulation model (STEPPE-GP) linked with a soil water model (SOILWAT) to evaluate the effects of changes in climate on the composition and structure of grassland vegetation. Five functional types of plants were simulated based upon lifeform, physiology, and rooting distribution with depth. C3 and C4 perennial grasses with either a shallow or deep rooting distribution, and deeply rooted C3 shrubs were simulated under current climatic conditions and under a GFDL climate change scenario for nine sites representative of the temperature and precipitation regimes in the grassland region.Although vegetation at the sites responded differently to climate change, shifts in functional types occurred within 40 years of the start of the climate change. C4 grasses increased in dominance or importance at all sites with a change in climate, primarily as a result of increases in temperature in all months at all sites. The coolest sites that arc currently dominated by C3 grasses were predicted to shift to a dominance by C4 grasses, whereas sites that are currently dominated by C4 grasses had an increase in importance of this functional type with a change in climate. Current annual temperature was the best predictor of changes in C3 biomass, and C3 and C4 biomass combined; current annual precipitation was the best predictor of changes in C4 biomass. These predicted shifts in dominance and importance of C3
versus C4 grasses would have important implications for the management of natural grasslands as well as the cultivation of crops in the central grassland region. 相似文献
14.
文章利用1952-2006年实际调查资料对围封和放牧条件下典型草原地上生物量、植物群落组成、数量特征、土壤含水量等进行对比分析,结果表明:与围封样地比较,放牧草场土壤下层水分明显减少,0～100cm土层水分减少12.5mm;植被生产能力下降,羊草和针茅的高度分别下降4.2％和5.2％,生物量减少14.9％和32.1％,群落总生物量下降29.2％,LAI减小22.2％.群落组成结构发生变化,多样性指数降低14.8％,退化现象比较明显. 相似文献
15.
This article studies the response of the distribution pattern and the physiological characteristics of the ecosystem to the spontaneous precipitation and the interaction between vegetation and the atmosphere on multiple scales in arid and semi-arid zones, based on measured data of the ecological physiological parameters in the Ordas Plateau of northern China. The results show that the vegetation biomass and the energy use efficiency of photosynthesis are especially sensitive to the annual precipitation; strong and complex interactions exist between the vegetation and the atmosphere on multiple scales leading to supernormal thermal heterogeneity of the underlying surface, the strong vortex movement and turbulence. This study can facilitate understanding of the land surface processes and the influences of global climate change as well as human activities on the human environment in the arid and semi-arid zones. It also aids in improving the parameterization schemes of turbulent fluxes of a heterogeneous underlying surface for land surface processes in climate models. 相似文献
16.
There is now substantial empirical evidence that climatic variability increases international migration, but relatively little is known about the mechanism driving the association and about adaptations that may reduce it. We use detailed data on migrants from Mexico to the U.S. to provide evidence in support of the hypothesis that drought induced migration from Mexico to the U.S. is mediated by agricultural income shocks. Migration rates increase in drought years, but only in Mexico’s drier regions, and the response is stronger in states and seasons in which agricultural production is also more sensitive to precipitation. Moreover, among the sample, only farmers display a significant increase in migration rates in drought years, and the effect is substantially weaker for households with access to irrigation. 相似文献
17.
André Lyra Pablo Imbach Daniel Rodriguez Sin Chan Chou Selena Georgiou Lucas Garofolo 《Climatic change》2017,141(1):93-105
Tropical rainforest plays an important role in the global carbon cycle, accounting for a large part of global net primary productivity and contributing to CO2 sequestration. The objective of this work is to simulate potential changes in the rainforest biome in Central America subject to anthropogenic climate change under two emissions scenarios, RCP4.5 and RCP8.5. The use of a dynamic vegetation model and climate change scenarios is an approach to investigate, assess or anticipate how biomes respond to climate change. In this work, the Inland dynamic vegetation model was driven by the Eta regional climate model simulations. These simulations accept boundary conditions from HadGEM2-ES runs in the two emissions scenarios. The possible consequences of regional climate change on vegetation properties, such as biomass, net primary production and changes in forest extent and distribution, were investigated. The Inland model projections show reductions in tropical forest cover in both scenarios. The reduction of tropical forest cover is greater in RCP8.5. The Inland model projects biomass increases where tropical forest remains due to the CO2 fertilization effect. The future distribution of predominant vegetation shows that some areas of tropical rainforest in Central America are replaced by savannah and grassland in RCP4.5. Inland projections under both RCP4.5 and RCP8.5 show a net primary productivity reduction trend due to significant tropical forest reduction, temperature increase, precipitation reduction and dry spell increments, despite the biomass increases in some areas of Costa Rica and Panama. This study may provide guidance to adaptation studies of climate change impacts on the tropical rainforests in Central America. 相似文献
18.
利用海北州海晏县1979—2009年地面气象观测资料和1997-2009年地上生物量资料,分析了1979年以来青藏高原的气候变化和水热条件变化,以及气温和降水量与地上生物量之间的响应关系。结果表明,1979—2009年该地区的年平均气温和降雨量均呈增加趋势,年平均气温的增加速率达0.33℃.(10a)-1,年降雨量增幅为33.1mm.(10a)-1;>0℃的有效积温、生物温度和实际蒸散量均呈明显的增加趋势,而湿润度则呈明显的减少趋势。海晏县高寒草地牧草草地地上生物量呈波动增加,且与冬季降雨量呈显著的正相关,与春季降雨量相关性不显著,与夏季平均气温相关性最高。 相似文献
19.
The response of a grassland ecosystem to climate change is discussed within the context of a theoretical model.An optimization approach,a conditional nonlinear optimal perturbation related to parameter(CNOP-P) approach,was employed in this study.The CNOP-P,a perturbation of moisture index in the theoretical model,represents a nonlinear climate perturbation.Two kinds of linear climate perturbations were also used to study the response of the grassland ecosystem to different types of climate changes.The results show that the extent of grassland ecosystem variation caused by the CNOP-P-type climate change is greater than that caused by the two linear types of climate change.In addition,the grassland ecosystem affected by the CNOP-P-type climate change evolved into a desert ecosystem,and the two linear types of climate changes failed within a specific amplitude range when the moisture index recovered to its reference state.Therefore,the grassland ecosystem response to climate change was nonlinear.This study yielded similar results for a desert ecosystem seeded with both living and wilted biomass litter.The quantitative analysis performed in this study also accounted for the role of soil moisture in the root zone and the shading effect of wilted biomass on the grassland ecosystem through nonlinear interactions between soil and vegetation.The results of this study imply that the CNOP-P approach is a potentially effective tool for assessing the impact of nonlinear climate change on grassland ecosystems. 相似文献
20.
基于GIMMS（global inventory modeling and mapping studies）NDVI 3g数据,在提取北半球荒漠草原过渡带每年植被物候期的基础上,研究了1982-2012年物候期的时间演化趋势及空间分异特征,并结合全球气候再分析资料,探讨了物候变化的气候驱动因素。结果表明：在1998年之前,荒漠草原过渡带植被物候期变化地区间差异较大,而在1998年之后,北半球荒漠草原过渡带生长季结束期整体提前,平均提前0.41 d/a;同时,除萨赫勒以外的各地区植被生长季长度普遍缩短,平均缩短0.88 d/a。植被物候期与气候因子的相关分析发现,荒漠草原过渡带植被物候变化受气候变化影响显著,且空间差异明显。在中高纬度地区,气温是限制植被活动的关键因子,温度升高可以促进生长季开始期的提前,而降水增加则会妨碍植被生长;在较低纬度地区,水分是影响植被活动的关键因素,高温造成的水分亏缺会导致植被生长季缩短。从植被物候期对各气候因子响应的时滞性来看,荒漠草原过渡带植被的物候期对气温变化的响应最迅速,对蒸散的响应存在一定的滞后性,而对降水的响应不存在时滞差异。 相似文献