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1.
《自然地理学》2013,34(6):519-533
In the Midwest, the oak savanna is a unique plant community located between the western prairies and northern forests, but, once the most common plant community in Wisconsin, it is now one of the region's rarest plant communities. To assess the success of varying intensities of management practices, standard dendrochronology and vegetation surveying methods were used to determine the age structure and species composition in oak savanna sites that varied from intensely managed to unmanaged. Size and age distributions revealed that the number of distinct cohorts of oaks increased in less managed sites. Seedlings and saplings were present in high frequencies in all sites; however, management practices such as fire applications that were too frequent apparently decreased oak survivorship, as did the competition in the closed canopies of the unmanaged sites. A fire frequency of 2-3 years eliminates competition, but a frequency of 4-6 years, typical of fire-adapted forest communities, allows for slower-growing species and younger oaks to survive, while still maintaining a low density. In these conditions, where growth rates vary in time, the use of dendrochronology is necessary to obtain an accurate canopy structure for fire-adapted forest communities. Quercus macrocarpa was dominant in the more managed sites, but shade-tolerant species were dominant in the unmanaged site. At present, the canopy composition in the managed sites represented an oak savanna assemblage; however, the unmanaged composition was shifting to a woodland assemblage. Thus, remnant oak savanna can be over- or under-managed, and unmanaged oak savanna can be overlooked as woodlands. 相似文献
2.
1982～2010年中国东北地区植被NPP时空格局及驱动因子分析 总被引：11，自引：1，他引：10
应用逐像元线性回归模型方法,整合应用MODIS和AVHRR NDVI数据集,构建1982~2010年覆盖东北地区的8 km空间分辨率的NDVI数据集,进而应用CASA模型估算得到东北地区29 a NPP数据集,模拟精度在75%以上。29 a平均的东北地区植被NPP总量为6.5×108tC/a。植被NPP的分布受植被类型、气候、地形因素的综合影响。NPP地域差异明显,山地区植被>平原区植被>高原区植被,变化最大的植被类型为草地植被。过去29 a间,植被NPP呈显著上升趋势(P<0.01)。气候变化和土地利用变化均是影响植被时空格局的重要因素。 相似文献
3.
Using geomorphological knowledge, spatial data and GIS methods, one can obtain phytogeomorphological site variables describing interactions between landforms and vegetation. We used 15 site variables derived from maps to explain forest site productivity in southern and central Finland expressed as dominant height of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) with ages of 30–110 years. These site variables were grouped into two: Group 1 with seven variables describing geographical conditions of sites including climate, and Group 2 with eight variables describing local morphometric and soil properties. We calculated slope and aspect from a 25 × 25 m DEM. The catchment area, calcium content in soil, length of the growing season, radiation index, sea index, lake index, past highest shoreline and total annual temperature sum with threshold + 5 °C were also obtained. Then we classified the landforms of 688 sample plots into four major types and 15 sub-types. We applied regression analysis to explain the tree height as a function of the tree age and the phytogeomorphological site variables. When the tree height was explained with the tree age and the Group 1 variables, the remaining standard error of the model was 16.6–17.9%. When the Group 2 variables were added to the analysis, the standard error decreased slightly. The most significant variables were the temperature sum, latitude coordinate and length of the growing season. Other significant variables were elevation, slope and aspect. The major landform types, sub-types and watershed area did not explain the tree height. Furthermore, if the forest site types determined in the field were included, the remaining standard error decreased by ca. 2%, showing the importance of field information. 相似文献
4.
火因子是生态系统中重要的干扰因素,对生态系统格局与过程有着深远的影响。采用人为放火的方法研究了草原化荒漠草本层片植物物种丰富度、地上部生物量、植物多度以及高度等群落学特征对火因子的响应。结果表明,火烧后两年（2008—2009年）,火烧样地单位面积中草本层片植物物种丰富度有所降低;植物多度多于对照样地,但无显著性差异（P>0.05）。火烧后当年,火烧样地中草本植物地上部生物量显著高于对照样地（P<0.05）,第2年地上部生物量无显著性差异（P>0.05）,说明火烧后当年有利于提高荒漠生态系统生物生产力,而第2年该效应消除。火烧后当年,研究区3种主要草本植物多根葱、无芒隐子草和茵陈蒿的高度受到了抑制,第2年其高度较对照样地又有所增长,但另一主要植物刺蓬则与其他3种植物反应相反,这可能与荒漠草本植物种不同生长特性有关。 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):251-270
The forest limits of south-east Norway have expanded to higher altitudes. Two main processes are believed to cause these changes: regrowth after abandonment of human utilisation and recent climate changes. The article aims at separating the effects of these two processes on the upper forest limits and recent forest expansion. Four datasets representing 161.5 km2 have been used: climate data, downscaled climate change scenario data, forest height growth, and four vegetation maps. The maps represent the years 1959 and 2001, potential natural vegetation (PNV), and a climate change scenario (CCS). The recent upper potential climatic and edaphic forest limit (UPCEFL) was used to define the potential for forest regrowth after the abandonment of human utilisation. Forest height growth and climate data were then used to analyse any supplementary effect of recent climate change. The projected future forest limits were based on the IPCC IS92a scenario for 2020–2049. The results show that raised forest limits and forest range expansion often attributed to recent climate change is rather the product of regrowth, a process that was climatically retarded from 1959 to 1995. For the period 1995–2006, the data indicate a preliminary effect of climate change escalating the regrowth and probably pushing the future forest limits to higher altitudes. 相似文献
8.
生态退耕对中国农田生产力的影响(英文) 总被引：1，自引：0，他引：1
The changes in cropland quantity and quality due to land use are critical concerns to national food security, particularly for China. Despite the significant ecological effects, the ecological restoration program (ERP), started from 1999, has evidently altered the spatial patterns of China’s cropland and agricultural productivity. Based on cropland dynamic data from 2000 to 2008 primarily derived from satellite images with a 30-m resolution and satellite-based net primary productivity models, we identified the impacts on agricultural productivity caused by ERP, including "Grain for Green" Program (GFGP) and "Reclaimed Cropland to Lake" (RCTL) Program. Our results indicated that the agricultural productivity lost with a rate of 132.67×104 t/a due to ERP, which accounted for 44.01% of the total loss rate caused by land use changes during 2000-2005. During 2005-2008, the loss rate due to ERP decreased to 77.18×104 t/a, which was equivalent to 58.17% of that in the first five years and 30.22% of the total loss rate caused by land use changes. The agricultural productivity loss from 2000-2008 caused by ERP was more attributed to GFGP (about 70%) than RCTL. Although ERP had a certain influence on cropland productivity during 2000-2008, its effect was still much less than that of urbanization; moreover, ERP was already converted from the project implementation phase to the consolidation phase. 相似文献
9.
祁连山青海云杉林动态监测样地群落特征 总被引：4，自引：0，他引：4
依据中国森林生态系统动态监测样地设置方法,参照国际森林生态学大样地建设技术规范,于2010年和2011年在祁连山自然保护区青海云杉（Picea crassifolia kom.）林内建立了10.2 hm2动态监测样地,定位调查了样地内19 927株DBH≥1 cm活立木木本植物,完成了第一次群落特征调查和分析。调查结果表明：①青海云杉群落成层现象明显,可划分为乔木层、灌木层、草本层和苔藓层4个层次。乔木层是群落的最主要层,整体而言其垂直高度结构复杂性要大于灌木层和草本层,苔藓层较为发达。②青海云杉径级结构呈明显的倒“J”形,个体集中在径级1~5 cm至21~25 cm,其占到总个体数目的91.42%,青海云杉更新良好。③青海云杉DBH≥1 cm对应的树高结构呈“单峰”形,高度主要集中在小于6 m,占到总个体数目的60.00%,高度偏小,小树较多,中树占有一定的比例,大树较少。同时,树高和胸径二者之间显著符合二次函数关系（p＜0.05）,反映了青海云杉群落生物学特征。④从空间分布格局来看,青海云杉表现出明显的聚集性分布格局。对不同年龄段青海云杉小树、中树和大树点格局分析表明,随着龄级的增大,种群的聚集程度减小,即由聚集分布变为随机分布,表现出明显的扩散趋势。青海云杉个体分布没有明显的空间异质性,而且2 534株大树随机分布在该样地,表明该群落未受大范围的人为干扰。 相似文献
10.
林分空间结构及其水源涵养功能关系一直是森林生态水文学研究的热点.我们在祁连山大野口流域选取林分空间结构、林冠截留和河川径流等监测样地,采用特征参数统计分析、多度分析和相关系数分析等方法,研究了林分空间结构因子及其水源涵养功能之间的关系.结果表明:(1)祁连山大野口流域49块样地的2 819株青海云杉(Picea crassifolia)的胸径、树高、冠长、冠幅、冠幅面积的分布曲线比正态分布平缓,树龄、胸径断面的分布曲线比正态分布剧烈;径级从1～5 cm到26～30 cm、高度级从2～4 m到18～20 m、冠长级从2～4 m到12～14 m、冠幅级从2～4 m到4～6 m,其多度分别为89.4%、94.4%、77.8%和82.7%.(2)林冠截留年总量和平均截留率分别为139.1 mm和35.28％;(3)从相关系数分析来看,海拔对树高影响较大,对冠长影响较小,与其他因子不相关;坡向对冠幅影响最大,对冠长、树高影响较小;坡度对这些因子几乎没有影响.径级与多度、冠长与多度均符合三次多项式关系;胸径与树高、冠长、冠幅、树龄符合线性多元回归函数;雨量级与林冠截留率呈反比.本文可为流域林分空间结构特征与水源涵养功能之间的机理研究提供基础数据和参考资料. 相似文献
11.
This article provides an analysis of a wetland site in southern Illinois from presettlement to the present. The study area is part of the Cache River‐Cypress Creek Wetland, which has international importance, as recognized by the Ramsar Convention on Wetlands. Land‐cover data for 1807, 1938, and 1993 were created and analyzed with a geographic information system (GIS). Land‐use change by topographic setting (uplands, transitional, and bottomlands) and soil productivity was quantified and studied. Interviews with local experts informed this analysis. Results illustrate the complexity of environmental change and its driving forces. First, notable forest and swamp acreage was converted to cropland between 1807 and 1938 and, to a lesser degree, from 1938 to 1993. Second, there were land‐use variations by topographic region. Between 1807 and 1938, the largest transformation occurred in the uplands, with substantial acreage converted from forest to cropland. Between 1938 and 1993, however, agriculture decreased in the upland areas as hilly areas reverted to forest cover. At the same time, agriculture expanded in the bottomlands as this land was drained for farming. Third, there are interesting patterns within these categories of land‐use change, as soil productivity is an indicator of what lands were taken out of cropland and converted back to grassland and forest. 相似文献
12.
Relationships between spatial and non-spatial preferences and place-based values in national forests
The management of multiple-use public lands such as national forests in the U.S. is controversial because of the wide range of potential uses and contested public values for these lands. Previous research on national forest values and management preferences examined these relationships non-spatially. The development of public participation GIS (PPGIS) and volunteered geographic information (VGI) systems provide new opportunities to assess spatial relationships between perceived national forest values and preferred uses. This research used empirical data collected from a PPGIS/VGI study for three national forests in California to examine spatial and non-spatial relationships between place-based forest values and preferred uses. The relationships suggest public participants translated some of their non-spatial forest values and preferences into behavioral choices when mapping place-specific values and preferred uses. The empirical relationships between place-based forest values and uses were generally consistent with previous survey research results. Positive, non-spatial attitudes toward extractive uses of national forests were correlated with participant mapping of economic values and related extractive uses, while nonmaterial forest attitudes were correlated with participant mapping of amenity values and conservation-related uses. Further, spatial preferences for extractive forest uses such as timber harvesting were mapped proximate to economic values, while nonmaterial spatial preferences were mapped proximate to amenity-related forest values. PPGIS offers the potential to translate philosophical and ideology-based national forest preferences into place-specific discourse about forest management activities where public accommodation may be more achievable. 相似文献
13.
《The Professional geographer》2013,65(1):127-140
Abstract This article provides an analysis of a wetland site in southern Illinois from presettlement to the present. The study area is part of the Cache River-Cypress Creek Wetland, which has international importance, as recognized by the Ramsar Convention on Wetlands. Land-cover data for 1807, 1938, and 1993 were created and analyzed with a geographic information system (GIS). Land-use change by topographic setting (uplands, transitional, and bottomlands) and soil productivity was quantified and studied. Interviews with local experts informed this analysis. Results illustrate the complexity of environmental change and its driving forces. First, notable forest and swamp acreage was converted to cropland between 1807 and 1938 and, to a lesser degree, from 1938 to 1993. Second, there were land-use variations by topographic region. Between 1807 and 1938, the largest transformation occurred in the uplands, with substantial acreage converted from forest to cropland. Between 1938 and 1993, however, agriculture decreased in the upland areas as hilly areas reverted to forest cover. At the same time, agriculture expanded in the bottomlands as this land was drained for farming. Third, there are interesting patterns within these categories of land-use change, as soil productivity is an indicator of what lands were taken out of cropland and converted back to grassland and forest. 相似文献
14.
我国落叶松林生产力的空间变化特征 总被引：1，自引：1，他引：1
落叶松林在我国有着广泛的分布。其空间差异也比较大。采用地统计学方法对我国落叶松林生产力的空间特征进行了分析。结果表明。落叶松种群和群落地理替代作用明显；落叶松林生产力空间异质性较大。其变化与空间尺度密切相关；地理位置、海拔高度等是影响落叶松林生产力的重要因素；在天然落叶松林的管理和保护以及人工落叶松林的发展上应考虑其空间特征。 相似文献
15.
基于新疆地区52个气象站点1959-2008年逐月气温、降水资料,利用Miami模型和Thornthwaite Memorial模型、线性趋势线、ArcGIS反距离权重插值等方法,对新疆草地生产潜力的时空变化特征进行分析。结果表明,近50 a来,新疆草地温度、降水、蒸散生产潜力均表现为显著增加,且四季和生长季各生产潜力也呈线性增加,夏季和生长季增幅最大,其次,草地生产潜力以及增幅均表现为北疆高于南疆,基本为由南向北递增,并和多年平均降水量变化一致。其中,水分条件是影响新疆草地生产潜力的主导因素。根据二元一次线性回归方程计算得出,年平均气温每升高/降低1 ℃,草地的年气候生产力增加/减少17.309 kg·hm-2·a-1,年降水量每增加/减少1 mm,草地的年气候生产力增加/减少24.392 kg·hm-2·a-1。 相似文献
16.
The planned construction of hundreds of hydroelectric dams in the Amazon basin has the potential to provide invaluable ‘clean’ energy resources for aiding in securing future regional energy needs and continued economic growth. These mega-structures, however, directly and indirectly interfere with natural ecosystem dynamics, and can cause noticeable tree loss. To improve our understanding of how hydroelectric dams affect the surrounding spatiotemporal patterns of forest disturbances, this case study integrated remote sensing spectral mixture analysis, GIS proximity analysis and statistical hypothesis testing to extract and evaluate spatially-explicit patterns of deforestation (clearing of entire forest patch) and forest degradation (reduced tree density) in the 80,000 km2 neighborhoods of the Brazil's Tucuruí Dam, the first large-scale hydroelectric project in the Amazon region, over a period of 25 years from 1988 to 2013. Results show that the average rates of deforestation were consistent during the first three time periods 1988–1995 (620 km2 per year), 1995–2001 (591 km2 per year), and 2001–2008 (660 km2 per year). However, such rate dramatically fell to half of historical levels after 2008, possibly reflecting the 2008 global economic crisis and enforcement of the Brazilian Law of Environmental Crimes. The rate of forest degradation was relatively stable from 1988 to 2013 and, on average, was 17.8% of the rate of deforestation. Deforestation and forest degradation were found to follow similar spatial patterns across the dam neighborhoods, upstream reaches or downstream reaches at the distances of 5 km–80 km, suggesting that small and large-scale forest disturbances may have been influencing each other in the vicinity of the dam. We further found that the neighborhoods of the Tucuruí Dam and the upstream region experienced similar degrees of canopy loss. Such loss was mainly attributed to the fast expansion of the Tucuruí town, and the intensive logging activities alongside major roads in the upstream reservoir region. In contrast, a significantly lower level of forest disturbance was discovered in the downstream region. 相似文献
17.
基于CBERS遥感数据的云南安宁“3．29”火灾面积评估 总被引：2，自引：0，他引：2
以中巴资源卫星（CBERS）多波段数据及纹理均匀性指标、图斑变异性指标和地形因子作为森林火灾灾后模式识别指标,提取了云南安宁“3．29”重大森林火灾火烧迹地地图以及受害指标,结合地面样地数据对过火区域的受害程度进行了等级划分。通过对灾前森林分布图和过火程度区划图的叠加分析,统计出了各类林地的受害面积。结果表明“3．29”火灾过火面积1695．4hm^2（25 430．29亩）,重度受害面积为518．6hm^2（7779．42亩）,中度受害面积为508．5hm^2（7627．36亩）,轻度受害积为668．2hm^2（10023．50亩）。地盘松过火面积最大,为796．3hm^2（11944．47亩）,其次为栎类灌木,过火746．4hm^2（11195．43亩）。利用卫星遥感图像的自动识别处理算法,既可识别火场、又可识别森林受害程度,可以替代地面对坡勾绘与目视解译的传统火场调查方法。 相似文献
18.
Evolution of disturbed oak woodlands: the case of Mexico City's western forest reserve 总被引：1，自引：0，他引：1
Arturo García-Romero 《The Geographical journal》2001,167(1):72-82
Mexico City is the largest city in population and area in the world. In the last 30 years it has expanded its area westwards to include the mountains of the Sierra de las Cruces. These mountains contain the nearest forest reserve for the citizens of Mexico City. Deforestation and severe ecological degradation resulting from the destruction of the natural environment; air, water and soil pollution; and hydrological and geomorphological imbalances, limit the capacity of these areas to support forest regeneration. This study focuses on the geo-ecology of the climax oak woodlands found in the Sierra de las Cruces. Based on morpho-structural evidence, bioclimatic type, degree of human intervention and general geo-ecological considerations, three territorial systems have been differentiated in which the oak woodlands exist in different climax facies: a) oak woodlands developed in very humid and cool environments located on low mountain slopes; b) disturbed oak woodlands developed in humid and cool environments located on high piedmonts; and c) highly disturbed oak woodlands developed in subhumid and temperate environments, located on low piedmonts. A comparative study of the content, structure and functional relationships of the secondary facies associated with these climax communities, allowed conclusions to be drawn on the way oak woodlands respond to human intervention, and the risky situations to which these communities are subjected, particularly the most sensitive facies that deserve immediate protection. 相似文献
19.
In previous studies the value of ecosystem services was evaluated microscopically by ecological indicators such as soil properties, biomass, carbon storage, oxygen release, water quality, and others. In this paper, the spatial heterogeneity of ecosystem services in Liuyang River basin was studied from the perspective of Geographic Information System (GIS) based spatial relationships by using a combination of geographic data and spatial analysis technologies. The Liuyang River basin was divided into grids with a resolution of 1km×1km. The weights of factors that affect the value of ecosystem services (such as topography, geological disasters, roads, scenic spots, vegetation coverage, and plant net primary productivity) were evaluated using the entropy method and analytic hierarchy process (AHP) in order to investigate the influence of natural and social factors on the value of ecosystem services in a quantitative manner. The results demonstrate that the value of ecosystem services is mainly affected by vegetation coverage, plant net primary productivity, and road network density. The value of ecosystem services grows with the increase in either vegetation coverage, plant net primary productivity, or road network density. Different types of land play different roles in ecosystem services. Cultivated land, grassland, and water each have significant supply and regulating functions while forest has significant regulating and supporting functions. The value of ecosystem services of cultivated land and water that are closely related to human activity is significantly influenced by spatial heterogeneity. In contrast, the effect of spatial heterogeneity on the value of ecosystem services of forest land and grassland that are located in mountains and hills, far away from the human accumulation zone, is insignificant. 相似文献
20.
Lucia Maria Seebach Peter Strobl Jesus San Miguel-Ayanz Annemarie Bastrup-Birk 《International journal of geographical information science》2013,27(11):1865-1884
Detailed and harmonized information on spatial forest distribution is an essential input for forest-related environmental assessments, in particular, for biomass and growing stock modeling. In the last years, several mapping approaches have been developed in order to provide such information for Europe in a harmonized way. Each of these maps exhibits particular properties and varies in accuracy. Yet, they are often used in parallel for different modeling purposes. A detailed spatial comparison seemed necessary in order to provide information on the advantages and limitations of each of these forest cover maps in order to facilitate their selection for modeling purposes. This article confronts the high-resolution forest cover map recently developed by the Joint Research Centre for the year 2000 (FMAP2000) with previously existing maps for the same time period: the CORINE Land Cover 2000 (CLC2000) and the Calibrated European Forest Map 1996 (CEFM1996). The spatial comparison of these three maps was carried out based on forest proportion maps of 1 km derived from the original maps. To characterize differences according to biogeographic regions, two criteria were used: detail of thematic content within each map and local spatial agreement. Concerning thematic content, CLC2000 displayed a surfeit of non-forested areas at the cost of low forest proportions, while FMAP2000 showed a more balanced distribution likely to preserve more detail in forest spatial pattern. Good spatial agreement was found for CLC2000 and FMAP2000 within about 70% of the study area, while only 50% agreement was found when compared with CEFM1996. The largest spatial differences between all maps were found in the Alpine and Mediterranean regions. Reasons for these might be different input data and classification techniques and, in particular, the calibration of CEFM1996 to reported national statistics. 相似文献