杨树刺槐混交林细根养分动态研究

Study on Fine-Root Nutrient Dynamics in the Mixed Plantation of Poplar and Black Locust

对两树种细根在北京市潮白河沿河沙地加拿大杨 (2 7a生 )刺槐 (2 2a生 )混交林中的分解情况进行了研究 ,从细根养分循环角度探索了两树种混交协调生长的机理。结果表明 :(1)加拿大杨和刺槐林木细根的分解特点不同 ,杨树细根在分解前期的N、Ca、Mg元素浓度逐渐升高 ,P、K元素浓度则逐渐降低。刺槐细根分解过程中N、P、K元素浓度逐渐降低 ,杨树刺槐混交林细根混合分解中各元素含量变化介于两树种细根单独分解之间 ;(2 )细根的N、K、Mg年归还量以刺槐纯根最大 ,两树种混根次之 ,杨树纯根最小 ;(3)混交林中N素归还量的增加有利于改善杨树的N素状况 ,杨树细根的P素归还量大于刺槐细根 ,有利于改善刺槐的P素营养 ,混交林杨树与刺槐在细根N。

The mixed plantation of poplar (Populus spp.) and Black Locust (Robinia pseudoacacia) is one of the typical mixed stands with nitrogen-fixing and nonnitrogen-fixing species. The interaction between two species in the mixed stand is harmonious and its productivity is high, so this kind of mixed plantations has become the very successful pattern on poor sandy sites in north of China. In this paper, fine-root decomposition of two species was studied in the mixed plantation of Canadian Poplar(P. canadansis)(27 a) and Black Locust (22 a) on sandy sites along the Chaobai River in Beijing. Mechanism of harmonious interaction between two species was found out in the view of the nutrient recycle of fine-roots. The result shows: (1) fine-root decomposition of Canadian poplar and black locust trees was different. The concentration of N, Ca and Mg was gradually increased and P, K was gradually decreased in poplar fine roots during the early period of decomposition. The concentration of N, P and K was gradually decreased in Black Locust fine roots during decomposition. The nutrient decomposition speed of mixed fine roots of two species during decomposition was between speeds of two pure samples. (2) the return amount of N, K and Mg in 1 a Black Locust fine roots was the biggest, mixed fine roots was the second and poplar fine roots was the smallest. (3) the increased N return amount of mixed fine roots could improve N nutrient condition of poplar trees. P return amount of poplar fine roots was more than Black Locust, which could improve the P nutrient condition of Black Locust trees. The interaction of mutual supplement of N and P nutrient recycle of fine roots between tree species was formed.