Study On The Effect Of Use Of Fire In Silvieultureon Soil Chemical Property Of Needle Leaf Forest Land

Cunninghamia lanceolata (Lamb.) Hook, and Pinus elliottii are the widely-use and growing fast tree species in southern China, which distributed in a large area of Jiangxi province. Forest fires occurred frequently in Coniferous forests. So prescribed burning is an efficient method used to reduce forest fuel loads, which can reduce forest fire and spreading. And also it can prompt a cycle and redistribution of forest land nutrient. This has important guiding significance for maintain the ecological balance and nutrient management of forest land.The standard plot of the prescribed burning is 1 hm2, which located at the coniferous forest land in Xinjian county of Jiangxi province. There was once prescribed burning every two months in plot. The burning time was set to 30min,60min,90min,120min and CK 5 treatment, repeated three times each burning. And a year later, unified sampling. The sampling depth is set to 0-5cm,5-10cm,10-20cm three levels. Through the analysis of indoor determination of soil sample chemical composition, we obtained the following results:(1) In processing of 30min combustion, the soil PH in depth between 0 cm to 5 cm increased 1.05, other treatments did not change significantly one year later;(2) In processing of 60min combustion, the soil organic matter in depth between 5 cm to 10 cm increased by 39.4%. That in depth of 0-5 cm increased by 38.5% for 90min burning, in depth of 5-10 cm,10-20 cm increased by 32.1%,38.5% respectively for 120min burning;(3) The 0-5cm soil nitrogen increased 34.9%,13.5% for burning 30min and 60min. And in depth of 0-5cm,5-10cm increased by 23.2%,4.4% respectively, but that in depth of 10-20cm on the decline.(4) Burning for 30 minutes, the soil available K in the depth of 0-5cm,5-10cm, and 10-20cm increased by 40.7%,32.8% and 57.2%, respectively. That in the depth of 0-5cm,5-10cm, increase 51.5%,45.6%, respectively, burning 60min. And in the treatment of burning 90min, the soil available K in the depth of 0-5cm,5-10cm and 10-20cm, increased by 35.3%,51.7% and 9.1% respectively. In burning 120min, that of 0-5cm increase 30.8%,5-10cm increased 36.8%, but 10-20cm drop;(5) The soil available P in the depth of 0-5cm,5-10cm,10-20cm in creased by 30.5%,53.3%, and 2% burning for 30 minutes. Burning for 60min, that in the depth of 0-5cm,5-10cm,10-20cm increase by 12.6%,38.2%, and 11.8%. In the treatment of 90min’ burning, the soil available P in the depth of 5-10cm increase by 38.4%, and in the 120min’ burning, that in 0-5cm,5-10cm,10-20cm increase by increased by 32.8%,42.9%,and 23.9% respectively.(6) The soil total nitrogen in the depth of 0-5cm,5-10cm,10-20cm in creased by 10.6%,4.9%, and 27.1% burning for 30 minutes. In the depth of 0-5cm,10-20cm, the soil total nitrogen increased by 32.7%,18.6% for 60min’ burning. The soil total nitrogen in the depth of 0-5cm,10-20cm increased by 27.9% 37.1%, respectively in the treatment of 90min’ burning. And in the 120min’ burning, that in 0-5cm,10-20cm increase by 27.9%, and 37.1% respectively.There are no obviously relation of changes in the chemical component by prescribed burning with the number of combustion, but have a closely relation with the burning time. And the above six soil nutrients increased in the treatment of 120min burning, especially in the depth of 0-10cm.