滨海沙地尾巨桉人工林凋落物及碳氮养分归还

对滨海沙地10年生尾巨桉人工林凋落物数量及其碳氮归还量进行为期1年的定位监测.结果表明：尾巨桉人工林年凋落量为6 739.92 kg/（hm2·a）,叶是凋落物的主要形式;凋落物量具有明显的季节动态,表现为“双峰”型,即5月和7月出现2次高峰;凋落物各组分碳含量差异不明显,介于45％～50％;凋落叶的氮含量是皮和枝的2倍多,氮含量大小排序为碎屑＞叶＞果＞枝＞皮.碳氮元素养分年归还量为3 325.86 kg/（hm2·a）,其中：碳归还量为3 267.48 kg/（hm2·a）,氮归还量为58.39 kg/（hm2·a）;C/N值为55.96,高于同试验区其他树种,大小排序为皮＞枝＞果＞叶＞碎屑.

Carbon and Nitrogen Return by Litter of an Eucalyptus urophylla × E.grandis Plantation in Sandy Coastal Plain Area

A one-year-long field study was conducted to measure litteffall quantity and its carbon and nitrogen return of an 10-year-old Eucalyptus urophylla × E.grandis plantation on a sandy coastal plain soil in southeast Fujian Province,China.The annual litter production of the studied plantation was 6 739.92 kg/（hm2 · a）,of which leaf litter was the main component.The quantity of the litterfall dynamically changed along the seasons,expressing ＂double peaks＂ individually in May and July of the year.The carbon content of litter components varied from 45%to 50% and there was no distinct difference in carbon content among the components.Whereas the nitrogen content in the leaf litter was 2-3 times higher than that of in bark and twig litter,which was in the order as miscellaneous 〉leaves 〉 fruits 〉 twigs 〉 bark.The total annual return of carbon and nitrogen from litterfall was 3 325.86 kg/（hm2 · a）,of which 3 267.48 kg/（hm2 · a） was carbon return and 53.89 kg/（hm2 · a） was nitrogen return.C/N ratio of the litterfall was 55.96,which was higher than that of other tree species in this trial site,and the ratio among the components followed the order as bark 〉 twigs 〉 fruits 〉 leaves 〉 miscellaneous.