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54个晋冀低山丘陵区人工和人工扰动植被表土花粉样品分析表明:花粉组合以草本植物花粉(74.5%)为主,乔木花粉含量低于20%。人类活动较强的农田以谷物禾本科、蒿属和藜科花粉为主,人类活动较弱的荒地以蒿属、藜科和杂草禾本科花粉为主。人类活动强度不同,指示种不同,孢粉浓度亦不同;农田指示种为谷物禾本科、葡萄科和胡桃科,孢粉浓度约4380粒/g;而蒿属、蓼科和蔷薇科则为荒地指示种,孢粉浓度约10983粒/g。农作物种植方式不同,谷物禾本科花粉含量不同,单一禾本科作物种植区谷物禾本科花粉含量(40.2%)高于多种作物混作区(18.8%)和荒地(3.8%)的含量。谷物禾本科含量的变化可以为利用化石花粉提取和检测人类活动信息提供依据,也可为利用地层中谷物禾本科花粉判断古代农业活动提供依据。  相似文献
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There are large tracts of wastelands in India, which have been lying almost barren for decades. Wasteland afforestation is found to be a financially viable and environmentally sound use of most of those lands. In addition, tree planting on wastelands is emerging as a potent tool for arresting the increasing misuse and over-exploitation of these lands and environmental degradation in India. This paper presents an overview of afforestation programmes in India undertaken by various agencies, then examines the prospects of increasing the pace of afforestation and identifies various policy and institutional issues that impede the pace of wastelands afforestation. This is done by adopting a two-pronged methodology comprising a review of literature available on the subject (a macro-perspective) and case studies (a micro-perspective). The results of this study show that there is inadequate investment in the forestry sector as a whole and there are several policy and institutional obstacles to promoting wastelands afforestation in India.  相似文献
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