Study On The Relationship Between Soil Properties And Tree Growth In Schima Superba Secondary Forests

This paper belongs to the forestry public industry scientific research project "Forest thinning and efficient use technology research on southern collective secondary forest (Project number:201004032)". In this article, take Schima superba secondary forest farm of Qingshigang, Yanling County, Hunan province as the research object. Analyze the soil physic-chemical properties, characteristics of forest seeding and dominant tree growth and and forest growth and soil property correlations.(1)Soil characteristics in the study area:Soil physic-chemical properties change over the depth of0～60cm soil layers in the study area. Water content and pH, the content of hydrolyzable nitrogen, organic carbon, total nitrogen and total phosphorus are reduced by1.62%,0.03,32.61g/kg,6.96g/kg,0.51g/kg and0.02g/kg with the increase of soil layer. The coefficient of variation of soil pH is5.32%, which belongs to the small variation. The coefficient of variation of soil water content is14.09%, belonging to moderate variability. The coefficient of variation of the other soil nutrients were all above35%.They are belong to the highly variation, and the degree of variation from high to low is:total potassium (72.26%), organic matter (68.96%) total nitrogen (66.96%), total phosphorus (47.06%), hydrolysable nitrogen (37.16%). Soil nutrients had obvious spatial heterogeneity, from the top to the foot of the hill and along horizontal direction distribution are obviously different. The organic matter, total nitrogen, hydrolyzable nitrogen and total phosphorus were abundant in at the rich vegetation, lying flat at foot of the hill. Hydrolyzable nitrogen and phosphorus contour lines are parallel to the contour of the mountain. Organic matter and total nitrogen affected by human disturbance, the distribution bits and pieces.The distribution of nitrogen distribution and hydrolysis pH value are just the opposite, pH value is high at the peak, low at the foot.(2)Study on forest growth:Schima superba forest seedling, dominant height growth and natural regeneration status are obviously different in each sample. By calculating the natural regeneration, natural regeneration status of each stand from poor to good order:Sample1(0.46)<sample2(0.52)<sample3(0.64)<samples4(0.68)<sample5(0.69)<sample6(0.69)<sample7(0.74)<sample8(0.88). Seedling growth of sample6and sample8were the best. The average height of seeding in sample4and sample5, had the most total number and medium growth level. Also found that the seedlings growing in good condition were not only had the biggest natural regeneration, but also mixed with coniferous tree species. Dominant height from high to low:sample7>sample8>sample3>sample5> sample6> sample4> sample1> sample2. Sample1and sample3had the maximum tree density and the lowest average DBH of dominant tree. Located at the foot of the sample3, sample7and sample8are in good growth, and the dominant height was significantly higher than other samples’.(3) Correlation analysis between tree growth and soil properties:The growth process of seedling, soil bulk density is not good to the growth and natural regeneration, but in a certain range, samples with greater density soil bulk had the higher dominant height. The pH in the certain scope is not conductive to seeding and tree growth, but also good to natural regeneration. Hydrolyzable nitrogen, organic matter, total N, total P were positive related to the number of seeding, seeding percentage, seedling ground diameter, seeding height, natural regeneration and tree growth. The correlation between seeding height, dominant height and soil characteristics were were more closer. Correlation of natural regeneration and soil physicochemical properties from strong to weak as follows:soil water content, organic carbon, total N, hydrolytic nitrogen and total P. From the result of the principal component analysis, moisture content, organic carbon and total N are the key factors to decide the natural regeneration of Schima superba forest. The nutrient requirements of forest in middle soil nutrient were more than the surface and deep soil layers. Relativity between dominant height and soil characteristics of phase was stronger than the relativity between dominant tree DBH and soil characteristics. This shows that, soil properties can significantly affect the growth of tree height. Correlation between height and soil characteristics is stronger than the correlation between tree DBH and soil characteristics. This shows that, soil properties can significantly affect the growth of tree height.