Abstract:

During the past decades, large scale natural forests had been converted to fast growing and high yield commercial plantations to meet the demands for timber, fuel material, and other forest products. Some silvicultural measures, such as planting pure stands, clear cutting and slash burning, were widely applied during this conversion. Yield decline and land deterioration in such disturbed ecosystems had become serious. In this context, the ecological comparisons between natural forests and plantations have special implications for sustainable management. Coarse woody debris (CWD) as an important pool of carbon and nutrients also plays a substantial role in several ecological processes in forest ecosystems. However, few studies on CWD have been conducted in natural and planted forests under same climatic and edaphic conditions in subtropical China.The standing crop and seasonal dynamics of CWD, its carbon and nutrient stocks were studied in a natural forest of Castanopsis kawakamii (NF) and adjacent plantations of C. kawakamii (CK) and Chinese Fir( Cunninghamia lanceolata, CF) in Sanming, Fujian, China. CWD masses were 1.32 t·hm^-2 in the NF, 0.46 t·hm^-2 in the CK and 0.23 t·hm^-2 in the CF respectively. The standing crop of CWD in three forests showed similar seasonal trend as follows: summer > winter > autumn > spring. Carbon storage in CWD of the NF was 0.78 t·hm^-2, being 4.11 times and 7.09 times as much as that of the CK and the CF, respectively. Significant difference in C stocks of CWD was found between NF and CK (or CF) ( P<0.05). Nutrient storage in CWD ranged from 14.16 kg·hm^-2 in the NF to 0.95 kg·hm^-2 in the CF. The amounts of N, P, K, Ca and Mg storage were the highest in CWD of the NF. The results of this study demonstrate that the natural forest has a greater capability for maintaining site productivity than plantations due to higher CWD mass coupled with greater carbon and nutrient pools. Therefore, conservation of the natural forest is recommended as a practical measure in forest management to realize sustainable development of forestry in mountainous areas of southern China.

Key words: coarse woody debris, carbon pool, nutrient pool, Castanopsis kawakamii, Cunninghamia lanceolata, natural forest, plantation