Converting tropical rainforest to forest plantation in sabah,malaysia. Part II. Effects on nutrient dynamics and net losses in streamwater     

A. Malmer  H. Grip 《水文研究》1994,8(3):195-209

Streamwater chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, comparing the effects of different ways to establish forest plantations with Acacia mangium. At the start of the monitoring in 1985 three catchments were covered with selectively logged rain forest (W4-W6) and three with secondary vegetation after forest fire (W1-W3). The treatments were: (1) clearing of secondary vegetation, burning and planting (W1 and W2); (2) clear-felling, crawler tractor extraction, burning and planting (W5); and (3) clear-felling, manual extraction, no burning and planting (W4). W3 and W6, with no treatment, were monitored as control catchments. Reference monitoring at all streams was for two years and was followed by treatments which lasted for nine months before the full establishment of a new vegetation cover. This paper covers monitoring for a further 2.5 years. The soil types of the catchments were Orthic Acrisol in W3, Gleyic Podsol in W6 and a mix of both soil types in the other catchments. The effect of treatments on streamwater chemistry was clear at both base- and stormflows. Concentrations of major plant nutrients (N, P and K.) became positively correlated to streamflow during treatments. The response of leaching from slash at clear-felling was fast and larger from the clear-felling residues (W4 and W5) than the cleared secondary vegetation (W1 and W2). The intense response to burning was more marked. The stormflow period mean nutrient concentrations were approximately 10-fold for N and K and 10-100 fold for P after burning compared with baseflow mean concentrations over the same period. Significant differences in baseflow concentrations in treated streams generally lasted one year for most elements, but elevated concentrations were still detectable after three years. The first large pulse of leaching was related to mineralization after tree-felling and particularly burning. The longer lasting elevated concentrations in baseflow were associated with the loss of weathering products. The amounts of nutrients lost, calculated by regression analysis as the effect of treatment compared with control, were found to be higher with the degree of vegetation killed and with increased soil disturbance. Consequently, normal forestry practices, with crawler tractor extraction and burning before planting, created the largest leaching losses. The total calculated effect of losses in total N, P and K were (i) W1 + W2 0.5, 1.8, 83.9; (ii) W4 0.8, 0.8, 105.6; and (iii) W5 1.3, 1.3, 189.4 kg ha^?1 for the period of 33 months during and after treatment. With normal forestry practice using crawler tractors and with burning before planting (W5), the treatment-induced loss of K was equivalent to 86% of the content of easily decomposed parts of the biomass (leaves, twigs, fine roots and ground vegetation) of the old forest, or larger than K removed by harvest. Exhaustion effects of lowered leaching after repeated burning (forest fire and pre-planting fire) was observed for several elements, indicating possible nutrient deficiencies.  相似文献   

Luminescence dating and archaeology of Holocene fluvio-lacustrine sediments of Abu Tartur, Eastern Sahara     

O. Bubenzer  A. Hilgers  H. Riemer 《Quaternary Geochronology》2007,2(1-4):314-321

Endorheic basins, filled by a rhythmic stratification of fluvio-lacustrine sediments, are useful archives for studying the interaction of palaeoenvironment and prehistoric development. Archaeological evidence indicates an occupational maximum during the Early to Mid-Holocene humid phase that can be linked to geochronological dates. A wadi has cut these sediments and a wadi profile of about 6 m was sampled for luminescence dating.

Palaeodose estimates are based on single aliquot measurements of the sand-sized quartz fraction using the regenerative dose technique. The comparison of equivalent dose results from different aliquot sizes (<100 and >1000 grains) provides interesting insights into heterogeneous degrees of bleaching. Problems arising from substantial variations in environmental dose rates of such heterogeneous sediments are discussed.

The luminescence ages indicate two major phases of deposition, both of Holocene age. The lower 2 m of sediments were deposited about 9400 years ago. The sedimentation of the upper 2 m started about 7200 and terminated around 6300 years ago. Radiocarbon ages of charcoals contained in the upper part of the section disagree with that OSL dating. This discrepancy is explained by re-deposition of the charcoal fragments.  相似文献   

Himalayan Perceptions. Environmental Change and the Well Being of Mountain Peoples     

《The Professional geographer》2006,58(2):224-226

  相似文献   

中国北方近百年干湿变化与太平洋年代际振荡的关系   总被引：37，自引：7，他引：37  

马柱国  邵丽娟 《大气科学》2006,30(3):464-474

利用CRU(Climate Research Unit)1901～2002年全球0.5°×0.5°网格点月降水和月平均气温资料,利用一个能够用于检测地表干湿变化的湿润指数,对中国北方四个典型地区干湿演变特征及与北太平洋年代际振荡的关系进行了初步的分析.结果发现:降水和湿润指数在表征干湿变化的特征时有明显的差别,特别是在干旱和半干旱地区,增暖也是影响干湿变化的一个重要因素.相关分析表明,华北和西北东部的年干湿变化与同期太平洋年代际振荡(简称PDO)指数有密切的关系,PDO指数的正位相对应两个地区的干旱时段,负位相则对应两个地区的湿润时段,而新疆南部与PDO指数同期呈显著的正相关关系,即当PDO为正位相时,该地区为湿的时段,负位相对应干的时段.以100°E为界,北方的东部干湿变化与太平洋年代际振荡指数呈反相关,而西部则相反,与PDO呈正相关关系.  相似文献   

浙江丽水太山山地常绿阔叶林的群落特征   总被引：4，自引：0，他引：4  

朱圣潮  王昌腾  徐燕云 《山地学报》2006,24(2):209-214

通过样方调查,应用物种丰富度,物种多样性指数和群落均匀度等指标对分布在浙江丽水太山山地的常绿阔叶林群落类型进行了分析。结果表明,太山山地常绿阔叶林主要有3种类型(群系),即甜槠木荷林、褐叶青冈林、青冈石栎林。并对各群落类型的结构和物种组成进行了分析。在群落的垂直结构上,灌木层、乔木层、草本层的物种多样性依次降低,群落类型处于华东和华南区系的过渡带。群落生活型以中、小高位芽植物为主,群落叶的性质以单叶,革质和全缘的小叶为主。  相似文献   

退耕还林对黄土高原地区土壤有机碳影响预测   总被引：17，自引：0，他引：17  

彭文英  张科利  杨勤科 《地域研究与开发》2006,25(3):94-99

土壤碳是全球碳循环中的重要组成部分，土地利用方式的改变对土壤碳的源和汇具有很大的影响。黄土高原地区进行的大规模退耕还林必然会通过影响土壤有机碳含量对区域碳循环产生重要影响。通过野外调查采样分析，结合使用全国土壤普查及黄土高原地区其它土地资源数据资料，研究计算了黄土高原地区的土壤有机碳量，并对实施退耕还林后土壤碳储量变化进行了预测。黄土高原地区土壤有机碳含量较低，平均土壤有机碳密度为2．49kg／m^2，仅为全国平均土壤有机碳密度的23．65％，土壤有机碳总储量为1068Tg，只占全国总有机碳量的1.16％。实施退耕还林后，土壤有机碳储量将明显增加。分步优化实施退耕30年后，黄土高原土壤有机碳储量可增至1266．8Tg，有机碳储量总体可增长19．21％。土壤有机碳储量的增加，对区域气候变化及土壤和水环境都将产生影响.  相似文献   

Australia's Box–Ironbark Forests and Woodlands: saving the fragments of a threatened ecosystem     

Max Kelly 《The Australian geographer》2005,36(1):19-37

Australia's box–ironbark forests and woodlands once covered about 14 per cent of the State of Victoria on the riverine plains and foothills of the Great Dividing Range. But approximately 83 per cent of the total original habitat has been destroyed and what remains of this significant ecosystem is now highly fragmented and vulnerable to further degradation. Moreover, only 14 per cent of the area remaining is on public land. A 10 year campaign on the part of the environmental movement eventually succeeded in forcing the State government to conduct an independent inquiry into this ecosystem and make recommendations on future management. This paper outlines the innovative public participation process adopted by the Victorian State government and the outcomes of the inquiry. A subsequent compensation package for commercial operations disadvantaged by the proclamation of a series of new national parks is also discussed, as are the shortcomings of a process that can have little or no impact on what happens on private land.  相似文献   

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  

张金屯 《山地学报》2004,22(3):298-302

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   

腐殖酸与铅锌相互作用的实验地球化学   总被引：6，自引：0，他引：6  

卢家烂  傅家谟  刘金钟 《矿床地质》1995,14(4):362-368

腐殖酸是沉积有机质的成分。实验证明，腐殖酸对铅锌离子具有强烈的富集能力。通过替代反应初步确定了腐殖酸与Ｐｂ，Ｚｎ之间几种结合方式及各种结合方式占数据和比例；证实富非酸和胡敏酸与Ｐｂ＾２＋，Ｚｎ＾２＋之间形成了两大类络合物：一类其稳定常数小于ＥＤＴＡ－Ｐｂ（Ｚｎ）络合物；另一类稳定常数大于ＥＤＴＡ－Ｐｂ（Ｚｎ）络合物。  相似文献   

从1999年叶尔羌河和克孜河洪水看新疆河流水情变化趋势   总被引：3，自引：1，他引：3  

何慧 《沙漠与绿洲气象(新疆气象)》2001,24(6):18-20

1999年南疆西部的叶尔羌河发生了冰川湖大洪水，克孜河暴发了暴雨泥石流堵塞的特大溃坝洪水，给喀什地区造成很大灾害；同时随着全球气候变暖，新疆的暴雨洪水和冰川湖洪水以及融水与暴雨混合洪水发生频次明显增加，但总的干旱背景不会改变。  相似文献