Biomass mapping using forest type and structure derived from Landsat TM imagery     

J.E. Luther  R.A. Fournier  D.E. Piercey  L. Guindon  R.J. Hall 《International Journal of Applied Earth Observation and Geoinformation》2006

A method for mapping forest biomass was developed and tested on a study area in western Newfoundland, Canada. The method, BIOmass from Cluster Labeling Using Structure and Type (BioCLUST), involves: (i) hyperclustering a Landsat TM image, (ii) automatically labeling the clusters with information about forest type and structure, and (iii) applying stand-level equations that estimate biomass as a function of height and crown closure within forest species-type classes. BioCLUST was validated with biomass values measured at geo-referenced field plots and mapped across the study area using an existing forest management photo-inventory. Root mean square error (RMSE) values ranged from 43 to 79 tonnes/ha, and were lowest for intermediate height classes when validated with field plots. Overall bias was negative at 10 tonnes/ha compared with a negative bias of 3 tonnes/ha estimated for the photo-inventory. Validation of the biomass map gave RMSE values of 37–47 tonnes/ha and overall landscape biomass estimates within 0.4% of biomass mapped by the photo-inventory. BioCLUST offers an alternative to other biomass mapping methods when scene-specific plot data are limited and a photo-inventory is available for a representative portion of a Landsat scene.  相似文献   

Effects of tides on a sloping shore: groundwater dynamics and propagation of the tidal wave     

A. Vandenbohede  L. Lebbe 《Hydrogeology Journal》2007,15(4):645-658

The influences of tides on a coastal environment with a sloping shore are investigated by means of field observations and groundwater flow modelling. The Belgian western coastal plain consists of a wide shore, dunes and polders where diurnal tides with large amplitude occur. The effects of tides on the groundwater flow are studied using the MOCDENS3D code. First, MOCDENS3D is validated to accurately simulate the propagation, attenuation and lag of a tidal wave in an aquifer. Then groundwater flow and influences of tides are modelled for a cross-section along the French–Belgian border. This gives an exhaustive insight into the spatial and temporal varying groundwater flow and propagation of the tidal wave in the aquifer. Simulation shows that there are two interfering flow cycles. The first is a shallow tidally fluctuating flow cycle on the shore due to the interaction of the gently sloping shore and the tidally oscillating sea level. The second is a deeper flow cycle from the dunes towards the sea. Further, it is indicated that the propagation and attenuation of the tidal wave follows a complex pattern with lateral as well as vertical components. The interaction between tides and shore topography also influences the salinity distribution.  相似文献   

基于LCA的森林景观的旅游生命力评价——以张家界市武陵源区为例     

陈端吕  董明辉  彭保发 《热带地理》2007,27(1):81-85

根据森林旅游资源具有生命周期的特点,引入环境评价中的生命周期评价方法与步骤,并利用生命周期矩阵的半定量方法,对森林景观进行生命力评价。结果表明:(1)各个景观所表现出的生命力,在森林景观自身的功能基础上,取决于生命周期的各个阶段的旅游魅力,生命力评价指数和常绿阔叶林景观的相关性,说明了常绿阔叶林景观的旅游魅力;(2)森林景观应按照年龄结构进行合理的空间格局配置,以提高旅游吸引力;(3)提高森林景观的旅游生命力,必须调整资源类型结构,尽量扩大高质量的森林景观种类比例,优化树种结构。  相似文献   

石林巴江流域近40年气温和降水变化的初步研究     

娄琼英  李玉辉 《云南地理环境研究》2007,19(4):110-114,138

利用数理统计方法分析了石林巴江流域中部近40年（1964-2001年）的气温和降雨量的年、季节和月变化。本区气温的增温速率是0．2℃／10a，与昆明市区增温率相近，低于同期全国增温速率；雨季（夏季）增温幅度大于旱季（冬季）。在过去40年中，年降雨量增加总量约为40mm，雨季降雨量略有降低，而旱季降雨量略有增强，全年第一次降雨强度和全年日最大降雨量也略有增加，但每年连续不降雨天数增加约1．9天。降雨量变化的波动性比气温变化的波动性强。气温、降雨量在1960s、1970s、1980s和1990s表现出不同的变化趋势。  相似文献   

Charcoal morphotypes in lake sediments from British Columbia (Canada): an assessment of their utility for the reconstruction of past fire and precipitation     

Mihaela D. Enache  Brian F. Cumming 《Journal of Paleolimnology》2007,38(3):347-363

Quantitative analysis of variations in morphological types of charcoal were undertaken in sediment cores from three lakes on the Interior Plateau (BC, Canada) over the period AD 1919–2000. Seven distinct morphological types of charcoal were identified based on particle shape and structural features and were compared with seasonal precipitation and recorded area burned within 20 km-radius of study lakes. Fragile-type charcoal fragments, termed type M, displayed significant relationships to recorded area burned in sediment cores from Prosser (r ² = 0.5; p = 0.0001) and Opatcho (r ² = 0.2; p = 0.02) lakes. However, nonsignificant correlations (p > 0.05) were found between total charcoal and area burned. Robust and highly elongated morphotypes C and F were correlated to recorded spring precipitation (r ² = 0.5; p = 0.002) in Opatcho Lake. Charcoal from a sediment core from Big Lake, the lake with the largest watershed, was significantly but inversely related to past fires (r ² = 0.44; p = 0.0003), suggesting important contributions from secondary transportation and deposition. Models were developed to infer relative area burned and precipitation for the study lakes. Our results suggest that charcoal morphotypes are related to the biogeoclimatic and lake watershed characteristics. This study also suggest that charcoal morphotypes can provide insights on past fire and climate, which was not possible based on traditional analysis of total charcoal.  相似文献   

辽宁本溪水洞地下暗河的补给源研究   总被引：1，自引：0，他引：1  

吴法伟  刘群昌  王宏伟 《地下水》2007,29(1):43-46

通过对辽宁本溪水洞区域水文地质条件、水文监测和示踪试验等资料的综合分析,对本溪水洞地下暗河的补给源及补给条件等进行了系统研究.  相似文献   

大兴安岭西北坡火烧迹地湿地格局变化及其影响因子研究   总被引：1，自引：0，他引：1       下载免费PDF全文

解伏菊  肖笃宁  李秀珍  胡远满  王绪高 《水科学进展》2007,18(2):175-181

选取大兴安岭1987年特大森林火灾主要过火区的图强林业局育英和奋斗两林场作为研究区,利用地理信息系统软件,对其火后湿地格局变化以及森林水文功能恢复状况进行了分析。结果显示,与过火前相比湿地面积增加了77.56%,且分布趋于集中;森林的平均水文调节能力已得到初步恢复,但具有较高调节能力的林地所占面积有所减少;森林的水文调节能力、地形因子以及火烧强度对湿地分布格局的变化均有明显影响。在森林水文调节功能下降地区、地势较低的谷地,坡度平缓的坡地以及火烧强度较大的地区,湿地面积增加明显。  相似文献   

Rainfall interception in three contrasting lowland rain forest types in Central Kalimantan, Indonesia   总被引：3，自引：0，他引：3  

R.R.E. Vernimmen  L.A. Bruijnzeel  A. Romdoni  J. Proctor   《Journal of Hydrology》2007,340(3-4):217-232

Rainfall interception was quantified and modeled for a Lowland Evergreen Rain Forest (LERF) and two Heath Forests (HF) of contrasting stature during a one-year period at a remote site in Central Kalimantan, Indonesia. Throughfall was measured using a roving gauge approach using 18–20 gauges per forest type. Throughfall was 82.8% of incident rainfall in the LERF vs. 89.1% in tall HF and 76.7% in stunted HF. Corresponding stemflow fractions were 0.8%, 1.3% and 2.0% of rainfall, respectively. Interception losses derived for the LERF (16.4%) and the tall HF (9.6%) were close to findings obtained for similar forest types elsewhere but the high interception loss for the stunted HF (21.3%) was unexpected. On the basis of canopy structural characteristics and wet canopy evaporation modeling it is concluded that throughfall in the stunted HF was underestimated and that the specific nature of the HF required a more intensive sampling arrangement. Throughfall sampling schemes in tropical forests, associated errors and hydrological implications are discussed.  相似文献   

What drives high flow events in the Swiss Alps? Recent developments in wavelet spectral analysis and their application to hydrology   总被引：2，自引：0，他引：2  

B. Schaefli  D. Maraun  M. Holschneider 《Advances in water resources》2007,30(12):2511-2525

Extreme hydrological events are often triggered by exceptional co-variations of the relevant hydrometeorological processes and in particular by exceptional co-oscillations at various temporal scales. Wavelet and cross wavelet spectral analysis offers promising time-scale resolved analysis methods to detect and analyze such exceptional co-oscillations. This paper presents the state-of-the-art methods of wavelet spectral analysis, discusses related subtleties, potential pitfalls and recently developed solutions to overcome them and shows how wavelet spectral analysis, if combined to a rigorous significance test, can lead to reliable new insights into hydrometeorological processes for real-world applications. The presented methods are applied to detect potentially flood triggering situations in a high Alpine catchment for which a recent re-estimation of design floods encountered significant problems simulating the observed high flows. For this case study, wavelet spectral analysis of precipitation, temperature and discharge offers a powerful tool to help detecting potentially flood producing meteorological situations and to distinguish between different types of floods with respect to the prevailing critical hydrometeorological conditions. This opens very new perspectives for the analysis of model performances focusing on the occurrence and non-occurrence of different types of high flow events. Based on the obtained results, the paper summarizes important recommendations for future applications of wavelet spectral analysis in hydrology.  相似文献   

What is a forest? Competing meanings and the politics of forest classification in Thung Yai Naresuan Wildlife Sanctuary, Thailand     

Theresa Wong  Claudio O. Delang 《Geoforum》2007,38(4):643-654

Based on a case study in a Thai forest reserve, this article compares two modes of ‘reading’ the forest - official and local forest classification systems - and discusses how they imply different ideas about the forest, and how these competing knowledges interact with the politics of forest governance. Forest classification conventions are shown to slip, as ‘facts’ about the forest, from their origins in extraction-oriented forestry to the realm of conservation. Through a comparison of conventional vegetation classifications used in the state’s governance of the Thung Yai Naresuan Wildlife Sanctuary in Thailand, with the classificatory systems of resident Pwo Karen communities, this paper examines the slippage of conventional classifications through various uses and the emphases placed by competing representations of the forest within the context of conservation politics in Thailand. It was found that conventional classifications continued to prioritise the silvicultural potential of trees within a conservation context, downplaying other notions of forests - such as their importance to livelihoods and as lived spaces - which are present in Karen classifications.  相似文献