Study On Degradation Characteristics And The Improvement Of Soil In Covered Phyllostachys Praecox F.prevernalis Forest

Phyllostachys praecox f. prevernalis, with early shooting emergence, high output and tasty shooting, is an excellent monopodial bamboo for shoot. Early shooting emergence technique with organic covered obtain enormous economic benefits in P. praecox forest in 1990s. But forest degeneration is changing serious and influences the sustainable development with the number of covered year increasing. In this paper, evaluation of degeneration degree, characteristics of forest structure soil and improvement of soil were studied in degenerated P. praecox forest, which proposed scientific basis for remediation. The main results were listed as:(1) 16 factors, including above ground forest structure and shoot output of covered P. praecox forest, were analyzed using PCA (principal component analysis). The results showed that cumulative contribution of the first 5 principal components was 82.135%, composed mainly by density, DBH of 1-2a bamboo, shoot output and age structure, which could represent mostly information of 16 factors. 4 degrees, severe (Ⅰ,Ⅱ), moderate (Ⅲ), light (Ⅳ) degraded forest and non-degraded (Ⅴ) forest, were partitioned through integrate score of each principal component from load equation, and it was found that the degraded forests took account for 80% of whole plots in study area.(2) As the degradation degree increasing, density of standing bamboo and age structure didn't showed significantly difference, DBH (diameter at breast height) decreased, and 3a>2a>1a, meanwhile height under branch increased, the relationship between DBH and height under branch decreased. Uniformity decreased and individual differences became heavy, evenness decreased first and increased afterward, and micro habitat became assemble.(3) With the degradation degree increasing, soil bulk density decreased, capillary porosity firstly increased then decreased, and moderate degraded forest was the inflexion, non-capillary porosity, total soil porosity, capillary/total soil porosity and non-capillary/total soil porosity changed less. Soil maximum moisture capacity, capillary moisture capacity increased, the change of soil minimum moisture capacity was same as capillary porosity, and moderate degradation forest was the inflexion, too. The soil mechanical composition did not show obviously law. Furthermore, weak correlations were found between each soil physical index. (4) As the increasing of degradation, soil pH decreased gradually, the content of soil exchangeable H+, Al3+, and total exchangeable acidity increased, soil exchangeable H+, Al3+ changed suddenly at moderate degeneration, and total exchangeable acidity at light degraded forest. Although cation exchange capacity had no differences, the content of exchangeable Ca2+ increased firstly, and decreased then, it was maximum in moderate-degraded forest, and exchangeable Mg2+ decreased gradually.For soil nutrition, Organic matter and phenolic acids increased significantly, total N, available N increased and later deceased, and the flexion was in light degradation forest. Available N, total P and total K contents had no obviously variation, available K content in degraded forest were lower significantly than non-degraded forest. Soil C/N, N/P increased, and N/K, P/K increased firstly and decreased then. Meanwhile, weak correlation was also found between each soil chemical index.(5) The activity of soil catalase, polyphenol oxidase showed relative stable in different degraded forest, but peroxidase in non-degraded forest was higher than degraded forest, and soil urease showed contrary sequence to peroxidase.(6) Liming and guest soil plough were employed to recover degeneration bamboo forest. Shoot output, DBH and height under branch increased obviously. It was best for improve effects of application 1125 kg·hm-2 liming and adding 10 cm gust soil in moderate degeneration forest, and it was better to tillage deeply after shooting emergence at summer.