格氏栲天然林与人工林枯枝落叶层碳库及养分库

Carbon and nutrient pools of forest floor in native forest and monoculture plantations in subtropical China

通过对福建三明格氏栲天然林及在其采伐迹地上营造的 33年生格氏栲人工林和杉木人工林枯枝落叶层现存量与季节动态、C库及养分库的研究表明 ,格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层现存量分别为 8.99t· hm- 2 、7.5 6t· hm- 2 和 4 .81t· hm- 2 ;枯枝落叶层中叶占现存量的比例分别为 6 4 .96 %、6 1.38%和 38.0 5 % ,枝占比例分别为 31.5 9%、37.83%和 4 2 .6 2 %。格氏栲天然林与人工林枯枝落叶层现存量最大值均出现在春季 ,而杉木人工林枯枝落叶层现存量最大值出现在夏季。格氏栲天然林枯枝落叶层 C贮量为 4 .0 2 t· hm- 2 ,分别是格氏栲人工林和杉木人工林的 1.2 2倍和 1.77倍 ;格氏栲天然林和人工林枯枝落叶层 C库与杉木人工林的差异均达到显著水平 (P<0 .0 5 )。格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层养分贮量分别为 138.4 2 kg· hm- 2 、113.5 6 kg· hm- 2 和 72 .39kg· hm- 2 ;除 Mg外 ,格氏栲天然林枯枝落叶层中各种养分贮量均最高。与人工林相比 ,天然林枯枝落叶层现存量、C和养分贮量均最大。枯枝落叶层对林地长期生产力维持具有重要作用。

In the last decades, large-scale native forests have been converted to fast-growing and high yield commercial forest 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, are widely applied during this conversion. Yield decline and land deterioration in such disturbed ecosystem has become serious. In this context, the ecological comparisons between native forests and monoculture plantations are necessary in providing the implications for sustainable management. The forest floor is not only storage pools of carbon and nutrient but a central, functional component of forest ecosystems. However, few studies on forest floor have been conducted in natural and planted forests under same climatic and edaphic conditions in subtropical China. The standing crop and seasonal dynamics of forest floor, its carbon and nutrient stocks were studied in a natural forest of Castanopsis kawakamii (NF) and adjacent monoculture plantations of C. kawakamii (CK) and Chinese fir (Cunninghamia lanceolata, CF) in Sanming, Fujian, China. Forest floor masses were 8.99 t·hm^(-2) in the NF, 7.56 t·hm^(-2) in the CK and 4.81 t·hm^(-2) in the CF respectively; of the total amount, leaves constituted 64.96%, 61.38% and 38.05% respectively, twigs constituted 31.59%, 37.83% and 42.62% respectively. The standing crop of forest floor in the NF and CK showed similar seasonal trend with the maximal value in spring. While for the CF, the forest floor mass peak occurred in summer. Carbon storage in forest floor of the NF was 4.02 t·hm^(-2), being 1.22 times and 1.77 times as much as that of the CK and the CF, respectively. Significant difference of stocks of forest floor C was found between NF( or CK ) and CF(P<0.05). Nutrient storage in forest floors ranged from 138.42 kg·hm^(-2) in the NF to 72.39 kg·hm^(-2) in the CF. Except for the highest Mg stock in the forest floor of the CK, the amounts of N, P, K and Ca storage were the highest in the forest floor of the NF. The results of this study demonstrate that the natural forest has a greater capability for maintaining site productivity than monoculture plantations due to higher forest floor 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.