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Sichuan Agricultural University (2009)

Properties of Soil in the Mountain Forests-the Arid Valley Ecotone in the upper Reach of Minjiang River

Zhao Qin

Titre : Properties of Soil in the Mountain Forests-the Arid Valley Ecotone in the upper Reach of Minjiang River

Auteur : Zhao Qin

Grade : Master’s Theses 2009

Université : Sichuan Agricultural University

Mountain forests of the upper reaches of Minjiang River Li County - arid valley Transitional Zone of returning farmland to forest soil as the object of study, according to the the altitude division of a typical arid valley lot, ecotone and mountain forest segment, respectively, were selected in each lot on behalf of vegetation types, to carry out a vegetation survey and soil sampling and analysis to investigate the variation of soil physical and chemical properties under different vegetation different environmental factors and changes in the law, to explore the mountain forest - arid valley ecotone vegetation restoration and management adjustment mechanism, enrich staggered with ecological theory of evolution, the mountain forest - the arid valley vegetation restoration and complex ecosystem management to provide a theoretical basis. The main results of the study are as follows : ① study area, different vegetation types in soil bulk density between 0.96 1.65 -3 , and increases with depth ; porosity of soil surface is better than the lower. The topsoil pH value at low altitude wasteland Minjiang Berlin at the highest, decreases with increasing altitude. Sub-surface soil pH trends (10 20cm) higher than the upper layer (0 to 10cm). Soil mechanical composition with grain size d <0.25mm and 0.25 0.5mm main variability of soil physical properties of the surface is greater than the lower variability, mainly due to the soil moisture content change and human activities. ② sticky capsules in the study area (<0.002mm) the powder capsules grade (0.02-0.002mm) content is generally higher, and increase vegetation cover to increase its content was increasing with the elevation gradient. Fine sand (0.25-0.02mm) content of the second, but its content increased with the elevation gradient and the increase of vegetation cover and reduce the level. (3) With the increased altitude and vegetation restoration, soil total nitrogen, total phosphorus, phosphorus, total potassium, available potassium and organic matter content significantly increased, indicating that the factors of soil moisture and vegetation of the study area is the main factor to affect soil nutrient status. In addition to soil organic matter, soil nutrient content and soil bulk density was significantly negative correlation between higher soil bulk density, the more soil compaction, soil nutrient content is lower. Vegetation recovery after each season soil organic matter, total nitrogen, total phosphorus, available phosphorus, total potassium, available potassium, the stand soil nutrients content in autumn> winter> spring> summer. That vegetation restoration can significantly improve the soil, increase soil nutrient content. Beech, birch secondary forest vegetation restoration type transitional zone on the edge of the natural recovery of the highest nutrient content, staggered taken off the edge of the artificial to restore forest nutrient content, followed by the arid valley segment Minjiang Berlin wasteland lowest nutrient content. ④ ecotone Mountain forests and plantations steep soil nutrient status than the the arid valley segment, indicating that the local natural environment conditions relative to the superior valley lower part, afforestation and can quickly take the ban measures to reduce grazing disturbance, vegetation recovery. Therefore, in the process of vegetation restoration should consider the impact of altitude on the distribution of soil nutrients. Along ecotone gradually down to restore the forest, the forest line down, and ultimately achieve the purpose of recovery of vegetation in arid valley is arid valley vegetation restoration an effective way to promote the restoration of vegetation in the arid valley area. The fractal dimension of each stand ⑤ soil microaggregate size : secondary forest> shrub> Robinia pseudoacacia broadleaved mixed forest> mixed coniferous the> CUPRESSUS> wasteland ; 2> wasteland. In the vertical direction, the aggregates fractal dimension PFD secondary forests> ecotone arid valley segment, you can see the mountain forest / arid valley vegetation restoration situation better than the low-altitude high-altitude, arid valley vegetation recovery gradually advancing from top to bottom, to improve the effectiveness of vegetation recovery provides a theoretical basis. Decision fractal dimension number of soil fine particles of the content, vegetation restoration, leaching lake argillic role to strengthen, and with the large number of litter restitution and vegetation Erosion and Dust Suppression of intercepted effects, soil fine particles of substances increase, Soil fractal dimension increases, better soil fertility and structure, the fractal dimension can reflect the extent of recovery in the arid valley vegetation. Ecotone PFD shrubs> locust forest> broad-leaved forest> mixed coniferous shrubbery to reduce the effects of interference better than other vegetation types, indicating that in the mountain forest / dry valley of vegetation restoration in Closure should be to ensure that one of the important measures of vegetation restoration effect.

Mots clés : Mountain forest - arid valley ecotone Vegetation restoration Soil physical and chemical properties Fractal dimension

Présentation (Dissertation topics)

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