不同造林密度下杉木人工林的氮储量与分配格局

Nitrogen storage and distribution pattern of Cunninghamia lanceolata plantations with different afforestation densities

[目的]探明杉木人工林氮储量及其分配格局与造林密度的关系。[方法]以不同造林密度(1800、3000、4500株·hm^-2)杉木人工林为研究对象,探讨其乔木层地上部分、林下植被层、枯枝落叶层和根系氮储量及分配特征。[结果]杉木人工林乔木层和枯枝落叶层氮储量随着造林密度的增大而提高,而林下植被层和根系氮储量则随造林密度的增大呈先升后降的趋势。乔木层地上部分是杉木人工林氮储量的主体,造林密度为1800和3000株·hm^-2的杉木人工林氮储量表现为:乔木层地上部分>根系>林下植被层>枯枝落叶层;4500株·hm^-2林分则表现为:乔木层地上部分>根系>枯枝落叶层>林下植被层。氮储量在乔木层各器官以及各径级根系中的分配相对分散,没有明显的主体。造林密度对乔木层宿存叶和宿存枝氮储量分配格局具有重要影响,但对乔木层其他器官和各径级根系氮储量分配格局的影响不明显。[结论]在一定造林密度范围内,杉木人工林乔木层地上部分和枯枝落叶层氮储量随造林密度的增大而提高,而林下植被层和根系氮储量随造林密度的增大呈先升后降的趋势。

[Purpose]To explore the relationship between nitrogen storage and distribution patterns of Cunninghamia lanceolata plantations and afforestation densities.[Method]The nitrogen storage and distribution characteristics of aboveground wood layer,under forest vegetation layer,litter layer,and root system each component in C.lanceolata plantations in different afforestation densities(1800,3000,or 4500 plants·hm^-2)were studied.[Result]The nitrogen storage of the aboveground wood layer and litter layer of C.lanceolata plantations increased with the increase of afforestation density,while a first increased then decreased tendency were observed in forest vegetation layer and root system of C.lanceolata plantations.The aboveground wood layer was the main body of nitrogen storage of the C.lanceolata plantations.The amount of nitrogen storage in the C.lanceolata plantations with an afforestation density of 1800 or 3000 plants·hm^-2 followed the order as:aboveground wood layer>root system>under forest vegetation layer>litter layer;while with an afforestation density of 4500 plants·hm^-2,it followed an order as:aboveground wood layer>root system>litter layer>under forest vegetation layer.The distribution of nitrogen storage was relatively scattered among different organs of the tree layer and in the roots of different diameters without any obvious main storage body.Moreover,the afforestation densities had a significant influence on the distribution patterns of nitrogen storage in dead branches and leaves of the living tree layer,but no obvious influence on the distribution pattern of stored nitrogen in other organs of the tree layer and roots of different diameters.[Conclusion]With a certain range of afforestation density,the nitrogen reserve of the aboveground wood layer and the litter layer of C.lanceolata plantation increased with the increase of afforestation density,while it showed a first rise and then decline trend with increasing afforestation density in the under forest vegetation layer and the root system.