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1.
An examination of the three major components of the energy balance has shown that subarctic vegetation cover markedly alters the relative importance of these components for the snowmelt. It has been found that the contribution of net radiation decreases as forest cover decreases while sensible and latent heat contributions to the snowmelt increase with decreasing forest cover. The decrease in the importance of net radiation with decreasing forest cover is due to the effect of the forest cover on albedo and the effects of the forest cover on the long-wave radiation component of the radiation balance. This situation seems to be typical for open canopy forests. The increase in importance of sensible and latent heat in the open is due to the increase in wind speed from the forest to open sites. 相似文献
2.
泾河上游流域实际蒸散量及其各组分的估算 总被引：7，自引：1，他引：6
利用分布式生态水文模型SWIM,基于泾河上游(泾川测站以上) 植被、土壤、气象和水文数据对研究区进行了水文过程的模拟,从而估算了流域的实际蒸散量及其各组分。结果表明：SWIM模型能够较好的模拟泾河上游流域的水文过程,模拟的流域多年(1997-2003 年) 平均实际蒸散量为443 mm,其中土壤蒸发量为259 mm,植被蒸腾量为157 mm,冠层截持量为27 mm。石质山区的森林覆盖区和非森林地的年蒸散总量在整个流域分别具有最大值和最小值,为484 mm和418 mm;黄土区实际蒸散量介于二者之间,平均为447 mm。森林覆盖地区土壤蒸发明显小于其它区域,而蒸腾和冠层截留明显大于其它区域。年内蒸散量主要集中在5-8 月份,占全年总蒸散量的60%,且冠层蒸散比例较大达63%。整个流域湿润年份较干旱年份蒸散量增加了78 mm,其中土壤蒸发增加最多,其次是冠层蒸腾,冠层截留蒸发最小。 相似文献
3.
利用SiB2 模型对中国东北地区农田、草地和森林3 种土地利用类型的地表能量平衡过程展开研究,分析不同土地利用类型对生物地球物理参数（反照率和粗糙度）、能量平衡（净辐射、潜热和显热）和气候（冠层温度）的影响。结果表明：①模型模拟的地表能量平衡与实测数据的年变化动态相似（R2>0.42）,差值保持在±30 W/m2,温度在±4 ℃。②利用相同气象数据模拟不同土地利用类型通过生物地球物理过程对地表能量平衡和气候的影响,发现森林吸收的净辐射最高且主要用于潜热分配,农田的净辐射最低且主要用于显热分配,草地净辐射和能量分配居中。③生态系统获得的净辐射主要受反照率的影响,净辐射分配受叶面积指数的调节。④冠层温度（℃）受反照率和净辐射在潜热和显热间分配的相对重要性的影响：年平均值为森林（7.7）>农田（7.64）>草地（6.67）。⑤降水对模拟结果有显著影响,是森林模拟差异的主要原因。在不同土地利用类型中,降水增加土壤水分,净辐射更多分配到潜热,较少分配到显热,降低冠层温度。 相似文献
4.
水资源在干旱区的经济社会发展中占据着举足轻重的地位,被利用的水资源通过蒸散发进入大气,定量估算区域的蒸散发对区域的水资源分配管理、旱情监测等具有一定的指导意义。应用SEBS模型估算了2015年5~9月艾比湖流域的蒸散发,按照流域的分水岭划分研究区范围,根据土地覆被类型将研究区划分为乔木林地、灌木林地、牧草地、耕地、水域及其他6大类,分析了流域内蒸散发的时间与空间变化以及不同土地覆被的蒸散发情况。结果表明：（1）整体而言,流域范围内日均蒸散量在生长季内呈单峰型分布,7月中旬达到顶峰,平均值为4.35 mm·d-1,最大值为5.63 mm·d-1,对气温的变化最敏感。（2）研究区蒸散发的高低分布与土地覆被类型分布存在高度一致性,日均蒸散量大小依次为：水域 > 耕地 > 牧草地 > 乔木林 > 其他 > 灌木林。（3）蒸散发在不同土地覆被具有不同的峰值分布,乔木林的峰值分别出现在1.20 mm和6.80 mm左右,灌木林的峰值分别出现在3.5 mm和6.00 mm左右,牧草地分别出现在4.00 mm和6.80 mm左右。耕地、水域的峰值分别在6.60 mm、7.20 mm左右。（4）SEBS模型在干旱区流域具有较高应用价值。 相似文献
5.
陕西咸阳人工林地土壤干层研究 总被引：20，自引：4，他引：16
根据咸阳庞西村苹果林地、梧桐林地和草地土壤含水量测定,研究了0~6m土壤含水量的变化和土壤干层特点与分布。结果显示, 咸阳人工林地从表层向下含水量呈现由高到低再到低的变化;10龄苹果林地2~4m深处土壤含水量平均为8.3%,12龄梧桐林2~4m深处土壤含水量平均为8.6%,均发育了明显的土壤干层;4龄苹果林下土层有干化显示,但无干层发育;草地土层含水量明显较苹果林地高,无土壤干化的显示。研究表明,土壤干层形成的具体原因一是降水量少决定的薄膜水带埋藏深度小,二是薄膜水的运移速度缓慢和含水量低。为保持人工林基本正常的生长和土壤水的正常运移,应避免严重的土壤干层出现。咸阳附近土壤干层的出现表明土壤干层在黄土高原广泛分布,该区的植被恢复首先应以疏林或森林草原为主,待土壤水分改善后再考虑恢复森林植被。 相似文献
6.
Influence of canopy and topographic position on soil moisture response to rainfall in a hilly catchment of Three Gorges Reservoir Area,China 总被引：2，自引：0，他引：2
Liu Muxing Wang Qiuyue Guo Li Yi Jun Lin Henry Zhu Qing Fan Bihang Zhang Hailin 《地理学报(英文版)》2020,30(6):949-968
Rainfall provides essential water resource for vegetation growth and acts as driving force for hydrologic process, bedrock weathering and nutrient cycle in the steep hilly catchment. But the effects of rainfall features, vegetation types, topography, and also their interactions on soil water movement and soil moisture dynamics are inadequately quantified. During the coupled wet and dry periods of the year 2018 to 2019, time-series soil moisture was monitored with 5-min interval resolution in a hilly catchment of the Three Gorges Reservoir Area in China. Three hillslopes covered with evergreen forest(EG), secondary deciduous forest mixed with shrubs(SDFS) and deforested pasture(DP) were selected, and two monitoring sites with five detected depths were established at upslope and downslope position, respectively. Several parameters expressing soil moisture response to rainfall event were evaluated, including wetting depth, cumulative rainfall amount and lag time before initial response, maximum increase of soil water storage, and transform ratio of rainwater to soil water. The results indicated that rainfall amount is the dominant rainfall variable controlling soil moisture response to rainfall event. No soil moisture response occurred when rainfall amounts was 8 mm, and all the deepest monitoring sensors detected soil moisture increase when total rainfall amounts was 30 mm. In the wet period, the cumulative rainfall amount to trigger surface soil moisture response in EG-up site was significantly higher than in other five sites. However, no significant difference in cumulative rainfall amount to trigger soil moisture response was observed among all study sites in dry period. Vegetation canopy interception reduced the transform ratio of rainwater to soil water, with a higher reduction in vegetation growth period than in other period. Also, interception of vegetation canopy resulted in a largeraccumulated rainfall amount and a longer lag time for initiating soil moisture response to rainfall. Generally, average cumulative rainfall amount for initiating soil moisture response during dry period of all sites(3.5–5.6 mm) were less than during wet period(5.7–19.7 mm). Forests captured more infiltration water compared with deforested pasture, showing the larger increments of both soil water storage for the whole soil profile and volumetric soil water content at 10 cm depth on two forest slopes. Topography dominated soil subsurface flow, proven by the evidences that less rainfall amount and less time was needed to trigger soil moisture response and also larger accumulated soil water storage increment in downslope site than in corresponding upslope site during heavy rainfall events. 相似文献
7.
山东南部景观生态特征研究 总被引：3，自引：0，他引：3
以地貌和基质为基本线索,以植被为标志,建立了山东南部的景观生态分类系统。该系统为二级分类系统,包括７个景观型、１７个景观亚型。以景观亚型或景观亚型的组合为基本制图单位,以１：１００万土壤图为基础底图,参考多种比例尺的卫星照片、植被图、土地利用图、地貌图等,编制了山东南部１：１００万景观生态类型图;在景观生态类型图上量算了各景观亚型的面积,并且分析了山东南部主要景观型的生态问题,据此提出了相应的生态对策。 相似文献
8.
黄土台塬区土地利用转移流及空间集聚特征分析 总被引：17，自引：1，他引：16
提出了土地利用转移流和土地利用活跃度的概念,基于Landsat 遥感影像数据,采用土地利用变化测度模型,以5 年和25 年两种时间尺度对黄土台塬区土地利用时空动态特征进行分析,并将密度制图法应用到土地利用变化的空间集聚特征识别中.研究表明：① 黄土台塬区耕地占绝对优势,后备耕地资源严重不足,林地、草地、水域比例较低,存在较大生态风险;② 耕地与建设用地、草地、林地之间的转移关系是黄土台塬区土地利用转移的关键关系,决定着台塬区土地利用变化特征;③ 1985-2010 年耕地转建设用地流高达26668.80 hm2,占土地转移流40.75%,草地转耕地流18923.90 hm2,占28.91%,建设占用耕地情况严重,耕地占补平衡主要通过挤占草地实现;④ 25 年以来,土地利用变化对水域扰动最大,其次为森林,草地第三;⑤ 土地利用变化存在阶段性,1990-2000 年土地利用变化速率高于其他时段;⑥不同时间尺度下土地利用变化的空间集聚特征不同,25 年尺度下城镇附近土地变化幅度较高,5 年尺度下土地利用变化热点区由台塬中部向东西边缘区推移. 相似文献
9.
岩溶山区不同植被群落土壤生态系统特性研究 总被引：14，自引：4，他引：10
自然植被演替成为次生植被、人工林或人工开垦利用后,岩溶山地土壤物理性能退化;沙化现象明显;坡耕地土壤长时间持水供水性能、抗旱性能降低;土壤种子库中草本种子比例大,木本植物种子少,土壤种子库退化更严重。研究区土壤有机质和全N受植被类型和土地利用强度影响明显,坡耕地土壤有机质较林草地系统低,退耕还林还草后,土壤有机质含量稳定增加。与自然植被相比,人工林、次生林系统土壤有机质含量仍较低。从弃耕地→灌草坡→次生林地的演替过程中,土壤种子库生态优势度呈降低趋势,物种丰富度和多样性增加。研究结果认为,岩溶生态系统土地退化的实质是土壤作为水库、养分库和土壤种子库功能的差异退化。 相似文献
10.
绿洲荒漠交界处波文比能量平衡法适用性的气候学分析 总被引：13，自引：0，他引：13
对广泛使用的计算蒸散和显热通量的气候学方法－波文比能量平衡法在绿洲荒漠交界处的适用性从气候学角度进行分析。结果表明,波文化－能量平衡法在干旱区绿洲的平衡层内是适用的,在平衡层外及荒漠上空却失效。因而,应用波文比能量平衡法估算绿洲上的蒸发与显热时,测点的位置是至关重要的。 相似文献
11.
苏打盐碱土地区不同土地利用类型的地表水分蒸渗特征 总被引：6，自引：0，他引：6
选择东北松嫩平原西部典型地区,采用FAO56方法和实际田间定期观测相结合,分析了当地旱田和碱斑地两种主要土地利用类型地表水分蒸散和入渗特征及其对土地盐碱化的影响。结果表明:对于玉米地这样相对蒸散量比较大的旱作农田来讲,水分亏缺和盐碱化主要发生在根层,而对表层土壤,即使在偏干旱年份,仍然有足够的水分入渗量来维持盐分平衡。碱斑地随着植被的破坏,总体上表层土壤蒸发和入渗量基本平衡,但是由于土壤水分蒸发过程中盐分浓度要比入渗过程中的盐分浓度大,表层土壤依然向盐碱化方向发展。采取适当的土地利用方式,建立耗水量与该地区降雨水平相适应的植被系统是控制区域土地盐碱化发展的关键。 相似文献
12.
通过对2013年春季中国科学院天山积雪与雪崩研究站区内阳坡无林地和阴坡不同开阔度森林内积雪深度、融雪速率以及常规气象的观测,分析了融雪期不同开阔度森林积雪的消融过程以及积雪表面能量平衡特征。结果表明:不同开阔度林冠下积雪深度具有相同的变化趋势,森林的林冠开阔度越大,林下积雪深度越大,林下积雪开始消融和完全消融的时间越晚,消融期也越长。森林积雪融雪开始和结束时间比阳坡无林地区晚20~30 d左右。融雪前期林冠开阔度越大,其林下融雪速率越小。融雪后期则森林开阔度越大,森林积雪的融雪速率越大。不同时期由于不同开阔度林冠下雪面能量收支以及雪层深度等物理特性的差异,从而使不同开阔度林冠下森林积雪融雪速率的相对大小,融雪速率最大值出现时间和日变化特征均不相同。晴天森林积雪的消融速率和日变化特征取决于净短波辐射和长波辐射变化特征。降水期间,其融雪速率的变化则主要受降水形式、降水量以及积雪深度等雪层特性的影响。 相似文献
13.
Valdemir Antoneli Edivaldo Lopes Thomaz Joo Ansio Bednarz 《Singapore journal of tropical geography》2019,40(1):34-49
The Brazilian faxinal is a traditional agrosilvopastoral system, which combines extensive grazing, subsistence cropping and low impact forest extraction, managed within a communal property system. Today it is at serious risk of disappearing due to increasing grazing pressure and logging activities that are leading to environmental problems such as forest fragmentation and soil degradation. The objectives of the study were to: a) evaluate soil physical degradation levels in different grazing areas within the faxinal system; and b) correlate soil degradation, fodder quantity and livestock dynamics in different pasture areas according to the household's location. Landscape mapping, vegetation surveys, and livestock grazing dynamics were assessed. In addition, soil physical parameters were evaluated for each land use (e.g., resistance, bulk density, porosity, moisture, and water infiltration rates). Results showed that livestock grazing and household locations are the main driving forces that lead to forest fragmentation. The household location creates three interrelated gradients in the communal grazing land: 1) soil physical degradation decreases from the pasture areas to araucaria forests; 2) fodder quantity decreases from pastures to araucaria forests; and 3) the livestock grazing intensity decreases from pastures to araucaria forests. In addition, some management practices to mitigate land degradation, including improvement of pastures, installation of removable troughs for drinking water in the upland areas and restriction of livestock from the riparian zone, have been proposed. 相似文献
14.
土地覆被变化过程中叶面积指数与降水量对地表能量平衡的贡献——基于SiB2的模拟结果 总被引：1，自引：0，他引：1
土地覆被变化过程中,叶面积指数（LAI）是地表能量平衡重要的影响因素,且与降水等多种因素存在交互作用。以2003 年中国东北地区农田、森林和草地三种覆被类型和三种LAI月变化过程为研究对象,着重分离出土地覆被变化过程中LAI对地表能量平衡的作用,认清覆被和LAI 变化对地表能量平衡的相对作用。利用SiB2 模型研究不同降水条件下土地覆被和LAI 变化对地表能量平衡的影响。结果表明：① 覆被变化对净辐射的影响最大,年均14.5W·m-2左右。② LAI 主要改变净辐射对潜热和显热的分配,对农田和草地而言,LAI 增加明显提高（减小）潜热（显热）分配比例;对森林而言,LAI对潜热和显热分配的影响较弱。③ 降水对净辐射的分配起重要作用,降水增加,潜热增加。④ 表层土壤水分受降水和LAI 调控,与潜热有相反的变化趋势。 相似文献
15.
16.
Shin Nagai Taro Nakai Taku M. Saitoh Robert C. Busey Hideki Kobayashi Rikie Suzuki Hiroyuki Muraoka Yongwon Kim 《Polar Science》2013,7(2):125-135
Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests. 相似文献
17.
元谋干热河谷区土地荒漠化研究 总被引：6，自引：0，他引：6
张建平 《云南地理环境研究》2000,12(1):1-8
干热河谷是我国西南地区特殊的生态类型,通过分析云南元谋干热河谷区土地荒漠的面积（海拔１３５０ｍ以下,荒漠化土地面积１００６．０２ｋｍ＾２,占该区总面积的７０．１５％）,表现特征（地形破碎,劣地广布,以肉质常绿灌丛为代表的类似荒漠植被,地表水分条件恶化,土壤贫瘠）及形成原因（自然原因：地质基础稳定性差,地貌类型多样,气候炎热干燥;人为原因：人口激增增加环境压力,垦荒,乱滥伐,过度放牧）,提出了土地荒 相似文献
18.
In Northeast Thailand, the climate change has resulted in erratic rainfall and tem- perature patterns. The region has experienced both periods of drought and seasonal floods with the increasing severity. This study investigated the seasonal variation of vegetation greenness based on the Normalized Difference Vegetation Index （NDVI） in major land cover types in the region. An assessment of the relationship between climate patterns and vegeta- tion conditions observed from NDVI was made. NDVI data were collected from year 2001 to 2009 using multi-temporal Terra MODIS Vegetation Indices Product （MOD13Q1）. NDVI pro- files were developed to measure vegetation dynamics and variation according to land cover types. Meteorological information, i.e. rainfall and temperature, for a 30 year time span from 1980 to 2009 was analyzed for their patterns. Furthermore, the data taken from the period of 2001-2009, were digitally encoded into GIS database and the spatial patterns of monthly rainfall and temperature maps were generated based on kriging technique. The results showed a decreasing trend in NDVI values for both deciduous and evergreen forests. The highest productivity and biomass were observed in dry evergreen forests and the lowest in paddy fields. Temperature was found to be increasing slightly from 1980 to 2009 while no significant trends in rainfall amounts were observed. In dry evergreen forest, NDVI was not correlated with rainfall but was significant negatively correlated with temperature. These re- sults indicated that the overall productivity in dry evergreen forest was affected by increasing temperatures. A vegetation greenness model was developed from correlations between NDVI and meteorological data using linear regression. The model could be used to observe the change in vegetation greenness and dynamics affected by temperature and rainfall. 相似文献
19.
以天山北麓三工河流域绿洲．荒漠交错带为研究对象,以可视化开发语言Visual Basic 6．0作为主要开发工具,结合Access数据库,在传统SPAC系统原理的基础上开发了绿洲．荒漠交错带水热传输可视化模拟系统。该系统具备系统管理、数据输入、数据处理、信息查询、模型计算、地下水预测、图形绘制、结果输出等功能。充分考虑到实时预测的实际工作要求,在系统开发的过程中,力求将本项目所研制的各种预测方案集成为一个可实时业务化运行的软件系统。通过该模拟系统可预测绿洲-荒漠交错带植被蒸腾量、地表蒸发量和植被的根系吸水速率以及土壤水热动态传输过程,为绿洲-荒漠交错带地下潜水-土壤-植被-大气连续体中数据的管理、地下水的预测和GSVAC水热传输动态的计算机模拟提供了强大的软件环境。 相似文献
20.
科尔沁沙地的土地利用与沙漠化 总被引：20，自引：12，他引：8
根据1985年和2000年的土地利用数据和从相同时期的TM影象上提取的土地沙漠化数据, 运用ARC/INFO软件和Access统计软件, 分析科尔沁沙地近20a来土地利用和沙漠化土地的构成及变化特点、土地利用与土地沙漠化之间的关系得出: 草地和耕地是土地利用的主要类型, 未利用地面积较大, 其他利用类型面积较小; 15a来, 耕地和林地增加幅度最大, 草地减少幅度最大, 土地利用转移的主要方向是草地变为耕地和林地。科尔沁沙地沙漠化土地比例大, 占一半左右, 以中度类型为主; 变化趋势是沙漠化面积增加, 程度减轻。在持续强度利用条件下, 面积广大的草地和耕地发生退化, 由潜在沙漠化土地发展为轻度和中度为主的沙漠化土地; 而土地利用方式变化所形成的沙漠化土地面积较小, 在新增沙漠化土地中的比例亦很小。所以, 草地、耕地等土地利用强度的增大是沙漠化土地面积扩大的最主要原因, 而土地利用方式的改变则能加快土地沙漠化的进程。 相似文献