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1.
贵州省森林资源动态变化 总被引：7，自引：1，他引：7
依据贵州省林业调查规划院1979、1984、1990、1995、2000年5次森林资源连续清查资料,从森林资源面积、蓄积量、组成结构等方面总结了该省近20年间森林资源动态变化的详细资料,并对变化的原因进行了分析。结果表明,20世纪70年代末至80年代末,林业用地面积、天然林面积与蓄积量均呈下降趋势;其后,由于贵州省政府及林业部门的高度重视,实施一系列林业生态保护与可持续发展工程,如国家“长江防护林工程”、“珠江防护林工程”等,贵州森林资源自1990年以来持续稳定增长,促进了生态环境改善 相似文献
2.
在社会经济快速发展的珠江三角洲地区,人类活动日益强烈,森林生态系统在平衡人类影响中的作用日益显著,但人工森林结构与分布差异越来越成为影响森林生态系统功能发挥的瓶颈.研究发现:(1)潭江流域林业用地结构失衡,作为潭江上游的恩平有林地面积仅占23.99%,潭江下游江门市区仅占13.93%,而未成林地,恩平却高达41.66%,这种森林分布结构不利于上游水源涵养功能与下游生态补偿功能的发挥;(2)无林地地域差异较大,人工造林仍有很大的潜力,台山、恩平、开平及江门市区无林地分别占全市域无林地面积的49.96%、14 相似文献
3.
The forests of southeastern Africa are vulnerable to damage imposed by tropical cyclones operating in the South Indian Ocean. We undertook a geographical analysis to determine the relative vulnerability of forests given tropical cyclones recorded during the 1959–2008 storm seasons. From this analysis, eastern coastal forests of Madagascar seem to be the most vulnerable, although return intervals for severe storms vary along the eastern coast, and are shorter (about 10 years) through the central portion of the country. Therefore, the central lowland to upper montane rainforests on the eastern coast seem to be more vulnerable to damage from tropical cyclones than others in the area. While not as extensive, western coastal forests of Madagascar are also as vulnerable in part due to the recurvature of storms in the Mozambique Channel. Though the coastal forests of Mozambique are all nearly equal in terms of vulnerability, the return interval for severe storms to this area is highly variable. The inland Miombo forests of southeast Africa are less vulnerable to damage from tropical cyclones; however, portions of western Mozambique and Zimbabwe have experienced strong tropical storms in the last 50 years. A number of caveats and limitations associated with the data and analyses are noted. Given the broad scale of the study, the relative vulnerability and the return intervals for severe storms should be considered general representations of these phenomena for the southeastern African coast and the island of Madagascar. 相似文献
4.
Drought has become a problem that is universally faced by global terrestrial ecosystems. Northeast China is located in a region sensitive to global climate changes, and one of the main impacts of climate changes in Northeast China is manifested as drought in growing seasons. This study analyzes the spatio-temporal evolution law of the water use efficiency (WUE) of the main natural vegetation (i.e., cold-temperate coniferous forests, temperate pine-broad-leaved mixed forests, warm-temperate deciduous broad-leaved forests, and grasslands) in Northeast China based on public MODIS data products, including MCD12Q1, MOD15A2H, MOD16A2, and MOD17A3H, and meteorological data from 2002 to 2013. The influence of drought events on the WUE of different vegetation types and their response to drought events are also investigated. The study findings are as follows: (1) drought in Northeast China frequently occurs in the regions stretching from 114.55°E to 120.90°E, and the percentage of drought area among the forests is lower than that among the grasslands during these years; (2) the annual average WUE of the natural vegetation ranges from 0.82 to 1.08 C/kg-1H2O, and the WUE of forests (0.82 to 1.08 C/kg-1H2O) is universally higher than that of grasslands (0.84 to 0.99 C/kg-1H2O); (3) in 2008, the regions where the WUE in drought conditions is higher than that in normal water conditions account for 86.11% of the study area, and a significant linear positive correlation is found between the WUE in drought conditions and the WUE in normal water conditions, whereas the degree of drought does not influence the WUE of the natural vegetation in an obviously linear manner; and (4) the WUE for the cold-temperate coniferous forests and temperate pine-broad-leaved mixed forests with a high ET or low NPP is more likely to rise in drought conditions; the WUE for the grasslands with a low Evapotranspiration (ET), Net Primary Production (NPP), and Leaf Area Index (LAI) is more likely to rise in drought conditions; and the ET, NPP, and LAI have no significant influence on the WUE for the warm-temperate deciduous broad-leaved forests in drought conditions. This study contributes to improving the evaluation of the influence of drought on natural ecosystems. 相似文献
5.
Monitoring degradation in arid and semi-arid forests and woodlands: The case of the argan woodlands (Morocco) 总被引：1，自引：0，他引：1
Yann le Polain de Waroux 《Applied geography (Sevenoaks, England)》2012,32(2):777-786
Arid and semi-arid forests and woodlands (hereafter called «dryland forests»), in spite of their ecological and social importance, have received little attention in land change studies. Growing evidence shows that these forests have been receding at very high rates in many places, suggesting a need for a better understanding of the processes and causes of dryland forest degradation. Changes in the extent of dryland forests are debated in part because estimates of forest and woodland areas in drylands are uncertain. Causal explanations of the degradation tend to draw on the literature on desertification and tropical deforestation, and to emphasize either local or remote, and either social or biophysical drivers. This study contributes to a better understanding of dryland forest degradation as a basis for conservation policies. Firstly, we argue that monitoring arid and semi-arid forests and woodlands using area estimates may lead to an underestimation of the severity of change because tree density change often exceeds area change. Secondly, we argue that the analysis of degradation processes in these multifunctional landscapes should integrate both local and remote, and both social and biophysical factors. We use a case study of degradation in the argania woodlands in semi-arid to arid Southwest Morocco to test these two claims. We used gridded tree counts on aerial photographs and satellite images to estimate forest change between 1970 and 2007, and we tested several possible causes of change on the basis of original socio-economic field surveys and climatic and topographic data. We found that forest density declined by 44.5% during this period, a figure that is significantly underestimated if forest area change is used as a measure of degradation. Increasing aridity and, to a lesser extent, fuelwood extraction were related to forest decline. No effect of grazing by local livestock was found. 相似文献
6.
岷江上游大沟流域油松人工幼林生物量组成及其影响因素 总被引：3，自引：1，他引：2
为了揭示人工林不同层次的生物量组成关系及其影响因素,选择岷江上游大沟流域的油松人工林,调查分析了林分不同层次生物量组成及其关系,探讨了乔木密度、坡向、海拔对生物量的影响。发现:1)两种林龄油松人工林生物量分配基本一致,即,乔木层>灌木层>草本层;乔木各构件生物量大小顺序为:枝>干>叶>根>果/皮。同时指出,枝叶对下木层生物量的影响显著。2)乔木密度显著控制了林分生物量及其组成,在本调查范围内坡向的影响似乎不明显;海拔对22 a油松影响显著,而24 a的不显著;综合分析表明,本区域内,22 a油松保持在3 800株/hm2左右和24 a在3 500株/hm2左右时,有助于林分生物量的稳定与提高,促进生态系统功能的恢复。 相似文献
7.
Hari Prasad PANDEY 《资源与生态学报(英文版)》2021,12(1):1-10
全球近四分之三的森林正在遭受人为干扰,尼泊尔三分之二以上的森林受到不同类型的干扰。在社区森林中,当地社区在生计的各个方面都依赖于森林提供的生态系统服务,这些服务以各种方式干扰森林的自然条件和生态系统的功能。本研究在尼泊尔中部丘陵区的两个社区管理森林中,研究了对植物物种多样性、更新(幼苗和树苗)、生物量、土壤有机碳(SOC)和总碳密度的主要干扰因子。以树桩数、断苗、砍伐和放牧践踏作为主要人为干扰的衡量指标,从89个随机选取的250 m2的样地中收集了必要的数据,利用广义线性模型(GLM)对人为干扰的响应进行了分析。结果表明,森林砍伐对生物量和总碳密度平衡的影响最大。森林砍伐程度越高,森林碳储量越低。SOC对上述类型的人为干扰均无显著反应。木本物种丰富度和幼树数量随着树桩数量的增加而增加,说明中间干扰是有益的。然而,较高的砍伐强度降低了幼树密度。放牧/践踏是抑制幼苗生长的最显著干扰,在践踏强度较高的森林地区,幼苗和树苗数量较少。这些结果将为尼泊尔多目标森林管理以及如何降低其他地区类似社会经济环境中的人为干扰的影响提供指南。 相似文献
8.
七里海泻湖湿地演变过程及其生态环境效应分析 总被引：3，自引：0，他引：3
以河北省秦皇岛市昌黎县七里海泻湖湿地为研究区,选取1919～2005年间的4幅地形图和1987年以来的10景landsat TM(ETM)遥感影像为数据源,运用遥感和地理信息系统技术,研究了七里海泻湖湿地近百年的时空演变过程,分析了泻湖湿地演变的影响因素与生态环境效应.结果表明,近百年来,七里海泻湖面积发生明显变化,由1919年的711.1 hm2缩减为2005年的279.1 hm2;1919年泻湖周边沼泽湿地面积为2 263.3 hm2,2005年泻湖周边的沼泽湿地已经基本消失;1956年以前,泻湖湿地以自然演变为主,主要受雨量充沛、入湖河流径流量丰富的影响,泻湖水面面积呈逐年增加趋势,1956以后,受流域开发治理工程、围垦和水产养殖等人类活动的影响,泻湖及周边湿地水动力条件发生改变,泻湖周边天然湿地逐渐为人工湿地所代替,泻湖水面面积减小,淤积加重,湿地生态系统受到极大干扰,呈现出生物多样性降低、景观单一化、湿地效应减弱等生态环境恶化的特征. 相似文献
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10.
极端干旱地区绿洲小气候特征及其生态意义 总被引：1，自引：0，他引：1
1 Introduction Microclimate is one of the most important environmental factors for plant growth and development. Different plant communities create different microclimatic environments and different microclimatic environments support different biotic comm… 相似文献
11.
Mangrove forests have important ecological functions in protecting the environment. However, the mangrove wetlands have been largely lost because of intensified human activities in the study area. Remote sensing can be conveniently used for the inventory of mangrove forests because field investigation is very difficult. In this study, a knowledge-based system is developed to retrieve spatio-temporal dynamics of mangrove wetlands using multi-temporal remote sensing data. Radar remote sensing data are also used to provide complementary information for the quantitative analysis of mangrove wetlands. Radar remote sensing is able to penetrate mangrove forests and obtain the trunk information about mangrove structures. The integration of radar remote sensing with optical remote sensing can significantly improve the accuracies of classifying mangrove wetland types and estimating wetland biomass. 相似文献
12.
Water stored in deep loess soil is one of the most important resources regulating vegetation growth in the semi-arid area of the Loess Plateau, but planted shrub and forest often disrupt the natural water cycle and in turn influence plant growth. The purpose of this study was to examine the effects of main vegetation types on soil moisture and its inter- annual change. Soil moisture in 0–10 m depth of six vegetation types, i.e., crop, grass, planted shrub of caragana, planted forests of arborvitae, pine and the mixture of pine and arborvitae were measured in 2001, 2005 and 2006. Soil moisture in about 0–3 m of cropland and about 0–2 m of other vegetation types varied inter-annually dependent on annual precipitation, but was stable inter-annually below these depths. In 0–2 m, soil moisture of cropland was significantly greater than those of all other vegetation types, and there were no significant differences among other vegetation types. In 2–10 m, there was no significant moisture difference between cropland and grassland, but the soil moistures under both of them were significantly higher than those of planted shrub and forests. The planted shrub and forests had depleted soil moisture below 2 m to or near permanent wilting point, and there were no significant moisture differences among forest types. The soil moisture of caragana shrub was significantly lower than those of forests, but the absolute difference was very small. The results of this study implicated that the planted shrub and forests had depleted deep soil moisture to the lowest limits to which they could extract and they lived mainly on present year precipitation for transpiration. 相似文献
13.
极端干旱地区绿洲小气候特征及其生态意义 总被引：8，自引：0，他引：8
运用微气象学方法对极端干旱区荒漠绿洲小气候进行了观测,分析我国极端干旱区荒漠绿洲的微气象特征并与林地外进行了对比。同时讨论晴天、阴天和沙尘暴天气的PAR的差异．分析了产生这些差异的原因。结果表明荒漠绿洲具有改变太阳辐射、调节近地层地表及地下温度、缩小温差、降低风速、提高土壤及大气湿度等重要生态作用。绿洲内部的太阳总辐射比林冠层顶部减少49．3％-49．83％：生长季胡杨和柽柳林内的气温均低于林地外．胡杨林平均比林外低1．62℃,柽柳林比林外低0．83℃,而且森林覆盖率越高降温作用越明显：群落上层气温高于群落下层,气温随高度增加而增加;林内大气相对湿度均高于林地外．生长期,胡杨林内比林地外高8．5％,柽柳林高4．2％;胡杨林地平均风速为0．33m／s．比林地外低2．7m／s：柽柳林平均风速为0．72m／s,比林地外低2_3lm／s。在沙尘暴日,PAR明显小于阴天日和晴天日下的值．而ηQ非常大,且变化不稳定,该结论对研究大气层的稳定性有极其重要的意义。 相似文献
14.
珠江口红树林湿地演变与现状的遥感分析 总被引：1，自引：0，他引：1
1 Introduction Half of the mangrove wetlands in China are situated in Guangdong province (Wang and Chen, 1998). The province used to have various types of wild mangrove forests along its coastal areas. The rapid expansion of urban areas and the fast deve… 相似文献
15.
不同植被类型的土壤水分对黄土高原的影响 总被引：9，自引：0，他引：9
Water stored in deep loess soil is one of the most important resources regulating vegetation growth in the semi-arid area
of the Loess Plateau, but planted shrub and forest often disrupt the natural water cycle and in turn influence plant growth.
The purpose of this study was to examine the effects of main vegetation types on soil moisture and its inter-annual change.
Soil moisture in 0–10 m depth of six vegetation types, i.e., crop, grass, planted shrub of caragana, planted forests of arborvitae,
pine and the mixture of pine and arborvitae were measured in 2001, 2005 and 2006. Soil moisture in about 0–3 m of cropland
and about 0–2 m of other vegetation types varied inter-annually dependent on annual precipitation, but was stable inter-annually
below these depths. In 0–2 m, soil moisture of cropland was significantly greater than those of all other vegetation types,
and there were no significant differences among other vegetation types. In 2–10 m, there was no significant moisture difference
between cropland and grassland, but the soil moistures under both of them were significantly higher than those of planted
shrub and forests. The planted shrub and forests had depleted soil moisture below 2 m to or near permanent wilting point,
and there were no significant moisture differences among forest types. The soil moisture of caragana shrub was significantly
lower than those of forests, but the absolute difference was very small. The results of this study implicated that the planted
shrub and forests had depleted deep soil moisture to the lowest limits to which they could extract and they lived mainly on
present year precipitation for transpiration. 相似文献
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Stan Stevens 《The Geographical journal》2003,169(3):255-277
Over the past 50 years the Sherpa-inhabited Mt Everest region of Nepal has become a premier international mountaineering and trekking destination. Tourism development has brought prosperity to many Sherpas. It has also, however, had adverse impacts on regional forests and alpine vegetation because of the use of firewood by camping groups and inns and the felling of trees to construct inns and other tourist facilities. Concern that tourism was causing widespread deforestation helped catalyse the 1976 establishment of an inhabited protected area, Sagarmatha (Mt Everest) National Park, in the Khumbu region and spurred the implementation of a series of forest conservation and alternative energy development measures both within the national park and in a recently declared buffer zone in the adjacent Pharak region. This paper examines the changing pressures that tourism has placed on regional forests and alpine vegetation over the past half century and their role in regional vegetation change. This analysis is based primarily on detailed accounts of past and present forest use and change obtained during fieldwork conducted in all Khumbu and Pharak villages, along with corroborating evidence from early foreign visitors' accounts and photographs. Contrary to some early reports it now appears there has actually been little deforestation since 1950. The continuing use of firewood by inns, however, has contributed to the thinning of forests in some parts of the national park and to the depletion of shrub juniper in the most heavily visited alpine regions. There has been a greater impact on forests just outside the national park, which have been heavily thinned over an extensive area in order to provide timber to build inns within the national park. 相似文献
18.
2008年春季中国南方冰雪冻害林木物理折损典型样带分析 总被引：1，自引：0，他引：1
2008年春季我国南方发生了特大冰雪灾害,林木损害严重。选择江西省井冈山-吉泰盆地-于山山脉-武夷山支脉样带作为研究区,两次进行野外调查,结合收集的数据,进行综合分析,取得结论包括：（1）在研究样带内人工林的损毁程度为湿地松林〉马尾松林〉混交人工林〉杉木林,在受损样本中湿地松林的实际受损比例高达61．3％,其中不可自然恢复折损实际比例达43．2％,相对比例达70．4％,主要是因为湿地松是美国南部地区外来引进种,生长块、材质疏松,而且割脂活动较强;马尾松为乡土造林先锋树种,材质较为坚硬,但受割脂活动影响,在受损样本中实际受损受损比例也高达52．5％,其中不可自然恢复折损实际比例达31．8％,相对比例达60．9％;杉木是本地树种,实际受损比例46％,其中不可自然恢复受损实际仅14．9％,相对比例也仅32．5％,低于混交人工林。（2）调查样带自西向东,西部井冈山地区常绿阔叶林受损程度最轻,分布在700m左右的人工柳杉林受损严重,杉木林分布在700m以下的受损程度较轻,而分布在900m以上的则相对严重;中部吉泰盆地受损调查样点中,分布在低海拔的湿地松林和马尾松林,因割脂活动受损程度严重,杉木林受损最轻,长期封育的天然次生林落叶阔叶林,由于藤本植物的缠绕,导致大量冰挂积雪,受损十分严重;东部兴国和宁都县,分布在400m以下的人工飞播马尾松因个体小基本未受损,分布在400m以上的1960年代人工种植马尾松,因割脂活动,受损严重;而分布在500～900m的杉木林受损程度较轻。 相似文献
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20.
Combined analyses of pollen, seeds, woods, micro-charcoal and non-pollen palynomorphs from Stagno di Maccarese, an artificially
dried out coastal basin north of the Tiber delta now occupied by the Fiumicino Airport (Rome, Italy), document marked vegetation
and environmental changes during the last 8300 years. Between 8300 and 5400 cal. a BP dense mixed deciduous and evergreen
forests surrounded a eutrophic freshwater basin. An abrupt change around 5400 cal. a BP marks the transition to a marshy environment,
due to a lowering of the water table. An increase of cereals and micro-charcoals matches the presence of a nearby Eneolithic
settlement. Between 5100 and 2900 cal. a BP there is a remarkable expansion of riparian trees, indicating an increase of the
water level. Between 2900 and 2000 cal. a BP, a new development of marshlands points to a progressive lowering of the lake.
After 2000 cal. a BP, during the Roman exploitation of the area, an expansion of arboreal vegetation is recorded, characterized
by evergreen and deciduous oak-dominated forests, while an extensive chenopods marshland matches the presence of saltworks.
On the whole, the Stagno di Maccarese area appears very unstable, due to changes in lake level, introgression of marine water,
eutrophic phases, flood events, desiccations and openings of the forest vegetation. 相似文献