Soil Health Characteristics And Assessment Of Plantations In Rocky Mountain Area Of Northern China

Healthy soil is fundamental for cultivating and protecting healthy forest, and it is of great importance to study forest soil health status for the maintenance and sustainable management of forest health. The pure plantation of Chinese pine (Pinus tabulaeformis Carr.), mixed plantation of larch (Larix principis-rupprechtii) and birch (Betula platyphylla suk.), mixed plantation of Chinese pine (Pinus tabulaeformis Carr) and larch (Larix principis-rupprechtii), pure plantation of larch (Larix principis-rupprechtii) with four densities (740,1480,2000and2170stem·hm-2) and pure plantation of Chinese pine (Pinus tabulaeformis Carr.) with six densities (540,650,1084,1104,1408,1860stem-hm-2) after thinning in Mulan paddock, Hebei Province were selected for the determination and comparison of soil physical, chemical and microbial properties in different forest stands with descriptive statistical analysis, correlation analysis and analysis of variance. Soil health of these forest stands was further assessed with principal component analysis. The results were showed as the followings:1) Types of forest stands had significant effects on soil physical, chemical and biological properties. With the increase of soil depth, soil bulk density and soil pH increased, soil water content, nutrients content, microbial quantity and soil enzyme activities decreased, but with different variation degrees in different forest stands.2) The variations of nutrients were not consistent when at different stand density. When the stand density of pure plantation of larch (Larix principis-rupprechtii) and pure plantation of Chinese pine (Pinus tabulaeformis Carr.) was2170and1104trees·hm-2, respectively, soil total N, total P and rapidly available K contents were in relatively higher levels in the soil depth of0-60cm, but higher contents of total K and available P of pure plantation of larch (Larix principis-rupprechtii) were only found in the depth of0-20cm, which were18.26g·kg-1and25.11 mg·kg-1. Soil average total N, P, K and available P, K in the depth of0-60cm of pure plantation of Chinese pine(Pinus tabulaeformis Carr.) reached the maximum values of1.38g·kg-1,0.34g·kg-132.75g·kg-1,33.10mg·kg-1and118.85mg·kg-1, respectively.3) The SOC content and density were characteristic of significantly vertically descendingwith the increase of soil depth. They had very significant or significant positive correlations with total N, total P and rapidly available K contents. When the stand density increased to2170trees-hm-2, the SOC content and density of pure plantation of larch (Larix principis-rupprechtii) reached the maximum,25.45g·kg-1and15.68kg·m-2, respectively. The SOC content and density of pure plantation of Chinese pine (Pinus tabulaeformis Carr.) were not consistent when the stand density increased from540stem·hm-2to1860trees·hm-2, and they ranged from10.56to21.21g·kg-1and from5.48to11.70kg·m-2, respectively. The stand density of pure plantation of larch (Larix principis-rupprechtii) and pure plantation of Chinese pine (Pinus tabulaeformis Carr.) were suggested to be about2170and1104stem·hm-2, respectively for the soil carbon sequestration.4) There existed close correlations between soil properties. Soil organic matter, total N, rapidly available K and the quantity of bacteria had significant or very significant negative correlations with soil bulk density, but very significant positive correlations with soil water content. The correlations between soil nutrients content were significant positive, but with varied degrees. Correlations were also found between soil microbial quantity and soil pH and soil nutrients content. There existed very significant or significant correlations between soil enzyme activitites and soil nutrients content as well as soil microbial quantity.5) The soil health assessment with principal component analysis showed that soil health in the depth of0-60cm was in the decreasing order of mixed plantation of larch (Larix principis-rupprechtii) and birch (Betula platyphylla suk.)>mixed plantation of Chinese pine (Pinus tabulaeformis Carr.) and larch (Larix principis-rupprechtii)>pure plantation of larch (Larix principis-rupprechtii)>pure plantation of Chinese pine (Pinus tabulaeformis Carr.), and Ⅻ(1104trees·hm-2)>Ⅺ(1084trees·hm-2)>ⅩⅣ(1860trees·hm-2)> Ⅸ(540trees·hm-2)> Ⅹ (650trees·hm-2)>ⅩⅢ(1408trees·hm-2) as for pure plantation of Chinese pine (Pinus tabulaeformis Carr.).