RELATIONSHIP OF ECO-ENVIONMENTAL CHANGE WITH NATURAL EROSION AND ARTIFICIALLY ACCELERATED EROSION     

Zheng Feili Tang Keli Zhang Keli Cha Xuan Bai Hongying Northwest Institute of Soil  Water Conservation  CAS  Ministry of Water Resources  Yangling  Shaanxi People''s Republic of China 《地理学报(英文版)》1997,(2)

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重庆市云阳县开发荒山资源,发展经济林木     

唐治诚  陈远喜  冉峰  王桂珍 《山地学报》1997,(4)

根据县内荒山资源特点,通过因地制宜,树立生态经济学观点,把开发荒山资源与保护生态环境密切结合,加以发展经济林木,促进了当地经济发展。  相似文献   

Variographic analysis of tropical forest cover from multi-scale remotely sensed imagery     

Sergio Colombo  Mario Chica-Olmo  Francisco Abarca  Hugh Eva 《ISPRS Journal of Photogrammetry and Remote Sensing》2004,58(5-6):330-341

Tropical forest mapping is one of the major environmental concerns at global and regional scales in which remote sensing techniques are firmly involved. This study examines the use of the variogram function to analyse forest cover fragmentation at different image scales. Two main aspects are considered here: (1) analysis of the spatial variability structure of the forest cover observed at three different scales using fine, medium and coarse spatial resolution images; and (2) the study of the relationship between rescaled images from the finest spatial resolution and those of the medium and coarse spatial resolutions. Both aspects are analysed using the variogram function as a basic tool to calculate and interpret the spatial variability of the forest cover. An example is presented for a Brazilian tropical forest zone using satellite images of different spatial resolutions acquired by Landsat TM (30 m), Resurs MSU (160 m) and ERS ATSR (1000 m). The results of this study contribute to establishing a suitable spatial resolution of remotely sensed data for tropical forest cover monitoring.  相似文献   

Fifty-thousand-year vegetation and climate history of Noel Kempff Mercado National Park, Bolivian Amazon     

Rachel E. Burbridge  Timothy J. Killeen 《Quaternary Research》2004,61(2):215-230

Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO₂ concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 ¹⁴C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 ¹⁴C yr B.P., coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2-3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.  相似文献   

川西亚高山三个森林群落的湿林冠蒸发速率     

杨万勤  王开运  肖玲 《山地学报》2004,22(5):598-605

于3个假说和林冠上方2m处的气象变量，采用Penman-Monteith组合模型估算了一个生长季节内川西亚高山林区分别以云杉(SF)、冷杉(FF)和白桦(BF)为优势树种的3个林分的湿林冠蒸发速率(Er)。研究结果表明，SF、FF和BF的湿林冠蒸发量(E)分别为44．51mm、88．51mm和57．8mm，分别占总降雨量的9．2％、16．6％和10．2％。与SF和BF相比，FF具有最高的月平均Er和蒸发比例。SF、FF和BF的平均Er分别为0．097mm／h(变化范围：0．028-0．487mm／h)、0．242mm／h(变化范围：0．068～0．711mm／h)和0．149mm／h(0．060～0．576mm／h)。最高和最低的月平均Er分别在6月(SF、FF和BF分别为0．120mm／h、0．317mm／h和0．169mm／h)和10月(SF、FF和BF分别为0．083mm／h、0．187mm／h和0．101mm／h)。8：00至16：00期间的平均点Er显著高于0：00至8：00以及16：00至0：00期间的平均Er。Er显著的日变化和月变化主要归因于林冠上方的太阳辐射、空气温度和相对湿度的变化。  相似文献   

Natural recovery from accelerated forest ditch and stream bank erosion five years after harvesting of plantation forest on Plynlimon,mid‐Wales     

Tim Stott 《地球表面变化过程与地形》2005,30(3):349-357

Erosion rates surveyed using 230 erosion pins on 24 occasions over eight years (1994–2001) on forested stream banks, tributaries and forest ditches in the 0·89 km² Nant Tanllwyth catchment, part of the Hafren Forest on Plynlimon, mid‐Wales, showed statistically significant increases of up to 40 mm a^?1 in mean erosion rates during the two‐year period in which environmentally sensitive plot‐scale timber harvesting operations took place (1996–97). In the four years following timber harvesting mean erosion rates at all sites recovered to levels that were lower than before the harvesting operations began. This is attributed to increased light levels, following canopy removal, allowing vegetation to colonize exposed banks. There was a statistically significant relationship (p < 0·05) between mean erosion rate in 2000–01 (four years after harvesting) and percentage vegetation cover at erosion monitoring sites in the clearfelled (south tributaries) area though the same relationship did not hold for sites on the mainstream banks or for sites on the north (mature forest) ditch sites. The implications of natural vegetation colonization for management of such streams are discussed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Soil respiration in tropical seasonal rain forest in Xishuangbanna, SW China     

SHA Liqing  ZHENG Zheng  TANG Jianwei  Wang Yinghong  ZHANG Yiping  CAO Min  WANG Rui  Liu Guangren  WANG Yuesi  SUN Yang 《中国科学D辑(英文版)》2005,48(Z1)

With the static opaque chamber and gas chromatography technique, from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna, SW China. In this study three treatments were applied, each with three replicates: A (bare soil), B (soil+litter), and C (soil+litter+seedling). The results showed that soil respiration varied seasonally, low from December 2003 to February 2004, and high from June to July 2004. The annual average values of CO2 efflux from soil respiration differed among the treatments at 1% level, with the rank of C (14642 mgCO2· m-2. h-1)＞B (12807 mgCO2· m-2. h-1)＞A (9532 mgCO2· m-2. h-1). Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna. There was a parabola relationship between soil respiration and soil moisture at 1% level. Soil respiration rates were higher when soil moisture ranged from 35% to 45%. There was an exponential relationship between soil respiration and soil temperature (at a depth of 5cm in mineral soil) at 1% level. The calculated Q1o values in this study,ranging from 2.03 to 2.36, were very near to those of tropical soil reported. The CO2 efflux in 2003was 5.34 kgCO2· m-2. a-1 from soil plus litter plus seedling, of them 3.48 kgCO2· m-2. a-1 from soil (accounting for 62.5%), 1.19 kgCO2· m-2. a-1 from litter (22.3%) and 0.67 kgCO2·m-2. a-1 from seedling (12.5%).  相似文献   

森林沼泽景观区中大比例尺化探找矿工作方法的研究--记大梁金矿的发现     

陈伟民  金浚  丁汝福 《矿产与地质》2005,19(6):665-668

大梁金矿是通过森林沼泽景观区开展1：50000和1：25000地球化学测量及综合地质工作而发现的,证明采用的森林沼泽景观中大比例尺化探方法是行之有效的.  相似文献   

DEFORESTATION IN NORTHEAST THAILAND, 1975–91: RESULTS OF A GENERAL STATISTICAL MODEL     

Gadsaraporn Wannitikul 《Singapore journal of tropical geography》2005,26(1):102-118

Using a general statistical model, this study attempts to characterise the trend of deforestation in the northeast region (Isan) of Thailand between 1975 and 1991, a period when the kingdom had sustained high rates of economic growth and steady increases in population. Using data obtained directly from government bodies on the 17 provinces comprising this heavily deforested region, the study examines the correlations between forest area and a set of six variables: population density, agricultural area, real per capita income, accumulated irrigated area, agricultural credit levels, and distance from Bangkok, the national political and economic centre. It also considers the effect of the two logging bans instituted in 1979 and since 1989. The study found a negative correlation between forest area and population density in particular, followed in ranking by agricultural credit, per capita income, the logging bans and distance from Bangkok. Viewed together with more recent data showing that rates of deforestation in the kingdom as a whole have slowed and appear to be stabilising, these results also suggest the beginnings in the 1990s of a forest transition – from an industrial to a post‐industrial stage in forest utilisation – in Thailand.  相似文献   

Cultivation and human impact at 6000 cal yr B.P. in tropical lowland forest at Niah, Sarawak, Malaysian Borneo     

C.O. Hunt  G. Rushworth 《Quaternary Research》2005,64(3):460-468

This paper describes palynological evidence for what appears to be comparatively large-scale human impact in the catchment of the Sungai Niah in the wet tropical lowland swamp forests of Sarawak, Malaysian Borneo close to the Great Cave of Niah. Pollen associated with cleared landscapes and rice cultivation is evident in the sedimentary record from before 6000 cal yr B.P. Human activity seems to have been associated with changes in sedimentary regime, with peat-dominated environments being replaced diachronously by clay-dominated deposition. This may reflect anthropogenic soil erosion in the catchment of the Sungai Niah.  相似文献