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排序方式: 共有124条查询结果,搜索用时 93 毫秒
1.
为了了解抚育间伐对燕山北部山区山杨林物种多样性的影响,对山杨林抚育间伐前后的物种多样性进行了调查和分析,结果表明:抚育后林地草本植物的物种多样性高于未抚育林地,抚育间伐林地草本植物的Patrick指数、Margarlef指数、Simpson指数和Shannon-Wiener指数分别为35.0、6.13、0.89和2.76,未抚育样地分别为29.0、4.90、0.32和1.91;抚育林地灌木的Patrick指数、Margarlef指数、Simpson指数和Shannon-Wiener指数分别为9.0、1.41、0.43和0.98,未抚育林地则分别为8.0、1.48、0.68和1.51,除Patrick指数外,抚育林地的其他多样性指数都低于未抚育林地;抚育间伐使乔木层优势种的优势更为明显。由此得出结论,抚育间伐对山杨林的物种多样性有明显影响,但草本、灌木与乔木对抚育间伐的响应有所不同。 相似文献
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Nelmarie Saayman Craig Morris Hannes Botha 《African Journal of Range and Forage Science》2016,33(4):225-233
The Succulent Karoo, one of two arid biodiversity hotspots in the world, is known for its high plant species richness, but little is known about the influence of topography and how it mediates the potentially deleterious effects of grazing. Changes in vegetation species composition, cover and species diversity were examined along piosphere gradients on northerly slopes, bottomlands and low-lying plains on 45 farms. Landscapes differed in the plant speciesand life-form composition, species richness and cover, with the more species-rich, heterogeneous grassy northerly slopes distinct from the plains and bottomlands, which were dominated by Pteronia pallens, Psilocaulon junceum and Drosanthenum spp. with more annual and ephemeral species. Overall, species richness declined linearly with decreasing rangeland condition. A weak grazing effect was detected only on the north-facing slopes, where shrubs and grass decreased with intense grazing. Years of overgrazing have resulted in the widespread dominance of P. pallens, especially on the plains and bottomlands, rendering them insensitive to grazing. The current condition of the northern slopes should be maintained and managed such that palatable species can spread to more degraded areas of the landscape. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(3-4):363-375
Abstract The study of plant diversity and its role in ecosystem functioning is becoming a central issue in ecology. The relationships between carbon storage and tree diversity of natural forest at small scale are still unclear. This research investigated these relationships in an old‐growth forest at Changbai Mountain, Northeast China. It was found that at small scale, tree carbon storage generally increases with increasing tree species richness, but for stands with same species richness, tree carbon storage varies dramatically. At the small scale, tree species evenness has a significantly linear relationship with nature logarithm of total tree carbon storage. The stand carbon storage of trees is mainly controlled by stand tree composition. Fraxinus mandshurica, Pinus koraiensis, Quercus mongolica, Tilia amurensis, and Acer mono contribute more than 85% of stand carbon storage of trees. Stands with similar tree composition at small scale have different soil organic carbon storage and nutrient contents. Tree species evenness has great impact on soil N content at the soil horizon less than 30 cm deep, but its impacts on C/N, P, K, and S contents are small. Tree density has a negative linear relationship with soil organic C and C∶N ratio at the soil horizon is less than 30 cm deep. The implication of our findings here for carbon sequestration in the Kyoto Protocol is also discussed. 相似文献
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本文主要调查了2019年5—8月太行山猕猴国家级自然保护区天坛山管护区内乔木在700~1 700 m海拔区间的垂直变化趋势。结果表明:在海拔700~1 700 m范围内,共有乔木38种,属于15科23属,其中壳斗科的栎属占据绝对优势;乔木物种数量随海拔变化具有明显的不规律性,但总体趋势维持稳定;乔木在总体海拔区段内多样性指数为H′=1.00±0.39,随海拔的升高呈不规则分布;乔木的整体均匀度指数E=0.57±0.15,在海拔区段内具有多样的变化。乔木物种多样性指数与均匀度指数之间具有显著的正相关关系。 相似文献
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策勒沙漠-绿洲过渡带土壤种子库的基本特征 总被引:2,自引:0,他引:2
通过室外萌发法对策勒沙漠-绿洲过渡带土壤种子库的研究发现:该区域土壤中活性种子从总储量上来看较为丰富,其中有12种植物,分属8科,但各植物种的种子数量分配极不均匀,仅有多枝柽柳的种子数量丰富,其它植物种的土壤种子储量相对匮乏,甚至严重匮乏;种子库的生活型组成以多年生草本占优(53.85%),一年生草本植物次之(30.77%);不同群落与地貌类型的种子库间保持着较高的相似性。 相似文献
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甘肃文县珙桐群落的组成结构数量特征 总被引:10,自引:2,他引:10
焦健 《甘肃农业大学学报》1995,30(2):189-193
甘肃文县为珙桐分布的北部边缘地带。对其群落的组成结构、数量特征研究分析认为,在沿摩天岭北坡自东向西的不同地段,水热条件优越程度下降,群落组成及优势种有所差异,群落多样性指数依次减小,分别为3.8830,3.3588,3.3545,生态优势度有升高的趋势,分别为0.0889,0.1139,0.1486,群落稳定性依次下降。中部地段的珙桐群落均匀度偏高,可能是人为活动干扰所致。 相似文献
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