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对平安县退耕还林选择树种进行了调查。结果表明:浅山地区选择的沙棘、白榆、柽柳、山杏、杨树、沙枣、油松、柠条和樟子松中,油松和樟子松不宜作为退耕地造林树种;脑山地区选择的云杉、红桦、白榆、沙棘和杨树中,白榆不宜作为退耕地造林树种;其他树种均可用作平安县退耕还林的造林树种。 相似文献
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黄土丘陵沟壑区人工林地的土壤抗蚀性评价 总被引:2,自引:0,他引:2
以延安、安塞、吴旗的人工刺槐林、柠条林为研究对象,选取同一地区的自然恢复草地和坡耕地为对照,通过对5个表征土壤抗蚀性的指标即>0.25 mm水稳性团粒含量、>0.5 mm水稳性团粒含量、平均重量直径、团聚状况和团聚度的比较分析,对人工刺槐林、人工柠条林相对于自然恢复草地和坡耕地改善土壤抗蚀性的效果进行了评价,同时分析了不同林龄人工林土壤抗蚀性的变化.研究表明,人工林地相对于坡耕地,显著提高了土壤抗蚀性,但不及自然恢复草地,尤其在安塞和吴旗表现更明显;随着林龄的增长,人工林地土壤抗蚀性能增强,并趋于稳定.并通过对样地的聚类分析,也得出与上述相似的结果.综合分析表明,封禁条件下的植被自然恢复是黄土丘陵沟壑区比较适宜的植被恢复方式和控制土壤侵蚀的有效措施. 相似文献
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M M HASOBA Ahmed 《干旱区科学》2020,12(4):609-617
Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots (1000 m2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height (DBH) ≥5.00 cm were identified and counted, and their DBH values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species (Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities. 相似文献
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干旱区杨树用材林土壤特性和林木生长对供水的响应 总被引:3,自引:1,他引:3
经过4年试验,结果表明,(1)供水对土壤水分调控作用明显,土壤各项含水指标均随供水量的增加而增加;(2)通过灌溉可改善土壤的三相比结构和土壤容重;灌溉对总孔隙度影响不明显;(3)灌溉对地下水位的影响显著,灌水前林地地下水埋深为3.46m,而灌水期内地下水埋深在2.36~2.87m之间,在7500m3/hm2.a灌溉定额以下时,不会造成土地次生盐渍化;(4)不同供水量对林木生长的效应是不同的,随灌溉量增加而造成不同程度的正增长;(5)人工林的蒸腾耗水量随供水量的增加而增加;(6)河套灌区杨树速生丰产林的合理灌溉量为7500m3/hm2.a。 相似文献
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Urban dwellers experience conflicting thoughts and feelings about urban woodlands; valued for their natural qualities, the relief they provide from the stress of modern urban living and the opportunities they afford for children's play and exploration. At the same time the seclusion inherent in this type of urban greenspace seems fraught with risk from crime, vandalism and abuse. Whilst many of these characteristics are well-researched, less is known about the differing perceptions of particular social groups. This study aimed to explore the ways in which age affects urban dwellers’ aspirations, values and fears concerning the woods, and woodland accessibility, focusing on the views of elderly people (aged over 65). This pilot study was based in Norfolk Heritage Park, an urban park containing a variety of woodland settings located in Sheffield, UK. The questionnaire survey (participantsn=97) revealed that although walking is the most popular leisure activity, most respondents did not visit urban parks as often as they would like, regardless of age. Whilst many of the meanings associated with urban woodland (“relaxation”, “peacefulness”, “seasonal change”, “scenery” and “education”) were shared amongst age groups, it seemed that the elderly respondents particularly valued the woods for their links with the past, and opportunities for immersion in the natural world. Some respondents from all age groups had fears about their personal security in the woodland, and the concerns of the elderly were heightened by their perceived frailty, reduced mobility and sense of vulnerability; this age group had a corresponding need for particular measures to alleviate these problems. The study provides preliminary evidence for the idea that adults of different ages have differing perceptions and requirements in relation to urban woodlands. Due to the small sample size and other methodological issues, further research is needed to confirm and develop the findings. 相似文献