对日本冲绳岛北部相同土壤条件下的琉球松纯林及其混交林的土壤氮素及有机碳素、地表凋落物量、枯枝落叶量以及土壤氮素矿化速率进行了比较研究.结果表明,琉球松纯林的地表凋落物层氮、碳平均贮量分别为133 kg*hm-2和7 199 kg*hm-2,混交林则分别为105 kg*hm-2和6 143 kg*hm-2.然而,混交林地表10 cm矿质土层的氮、碳贮量则显著高于纯林,氮素比纯林多493 kg*hm-2,碳素多5 554 kg*hm-2.在30 d的实验室培养实验中,混交林表层土壤的氮素矿化速率高于纯林18%;而且,混交林的落叶和土壤的碳氮比值亦明显低于松纯林.混交林土壤的年平均矿化氮素(NH4++ NO3-)浓度高于纯林22%.与松纯林相比,混交林通过枯枝落叶年平均氮素归还量多43.7 kg*hm-2,碳素归还量多1 655 kg*hm-2.混交林具有较高的氮素归还量,主要是混交林的针叶含氮含量较高以及大量的高含氮量的阔叶落叶所致.上述结果充分说明针阔混交导致了林分氮素循环的变化.%Total nitrogen (N) and organic carbon (C) in soil, forest floor and litterfall, and N mineralization rates were compared between pure and mixed Pinus luchuensis plantations on similar soils in the northern Okinawa Island, Japan. Mean accumulations of N and organic C on the forest floor were 133 kg*hm-2 and 7 199 kg*hm-2 for the pure pine stand, 105 kg*hm-2 and 6 143 kg*hm-2 for the mixed stands. However, in the surface 10 cm mineral soil, the mixed stands had an average of 493 kg*hm-2 and 5 554 kg*hm-2 more than the pure pine stand (p＜0.001). Amount of N mineralized from soil during 30-day incubation was 18 % greater in the mixed stands than in the pure stand (p＜0.01). Average seasonal soil mineralizable N (NH4++NO3-) concentration was 22% greater in the mixed stands than in the pure pine stand (p＜0.01). The mixed stands returned an average of 43.7 kg*hm-2a-1 (about 70%) and 1 655 kg*hm-2a-1 (about 39%) in litterfall more than the pure stand did. The greater litterfall N input in the mixed stands was due to higher concentration in the pine needle litter and the presence of high-N broadleaf litter as well. The results from this study suggest that conifers have different N cycling when mixed with broad-leaved trees from when in pure stand.
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