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杉木枯死枝叶由于长期宿存于树冠,不易脱落,且生物量大,其分解和养分释放对杉木人工林营养循环具有重要意义。用比叶质量法估算了我国亚热带地区福建南平17年生杉木树冠层不同高度宿存叶片的分解程度,测定了碳氮含量、碳氮稳定性同位素及有机碳化学组成。结果表明:杉木宿存叶片的比叶质量呈现出由上向下逐渐减小的趋势,树冠8~10 m处宿存叶片的比叶质量(26.02 mg·cm-2)显著大于刚死杉木叶片的比叶质量(23.12 mg·cm-2)和6~8 m处宿存叶片的比叶质量(15.39 mg·cm-2),而0~2、2~4和4~6 m这3层宿存叶片的比叶质量无显著差异。刚死杉木叶的碳含量(50.67%)和氮含量(0.75%)显著低于不同高度宿存叶片的碳氮含量,而不同高度宿存叶片的碳氮含量和碳氮比均无显著差异。刚死杉木叶片的碳氮比(67.58)显著高于不同高度宿存叶片的碳氮比。当杉木宿存叶片的C/N为45.91±0.45时开始净氮释放。刚死杉木叶片和8~10 m高度处宿存叶片δ15N值显著高于其他高度宿存叶片,而其他高度宿存叶片的δ15N含量无显著差异。不同高度杉木宿存叶片的δ13C无显著差异。杉木宿存叶片中多糖碳和乙缩醛碳首先被分解,而烷基碳、芳碳、酚碳和羧基碳的分解速度比多糖碳和乙缩醛碳的慢。
Due to long-standing dormant branches and leaves in the canopy of Cunninghamia lanceolata, it is not easy to fall off, and the biomass is large. The decomposition and nutrient release of Cunninghamia lanceolata are important to the nutrient cycle of Cunninghamia lanceolata plantation. The specific leaf mass method was used to estimate the decomposition degree of the leaves of 17-year-old Chinese fir canopies at different heights in the subtropical area of China. The contents of carbon and nitrogen, carbon and nitrogen stable isotopes and organic carbon were determined. The results showed that the specific leaf mass of Chinese fir deciduous leaves tended to decrease gradually from top to bottom. The specific leaf mass (26.02 mg · cm-2) of the preserved leaves at the 8-10 m crown was significantly greater than that of the newly-fir fir leaves The specific leaf mass (23.12 mg · cm-2) and the specific leaf mass (15.39 mg · cm-2) at 6 ~ 8 m, while that of 0 ~ 2, 4 ~ 4 and 4 ~ 6 m Stored leaf leaves than the quality of no significant difference. The carbon content (50.67%) and nitrogen content (0.75%) of freshly-dead Chinese fir leaf were significantly lower than those of the different height of the leaves, while the carbon and nitrogen contents and carbon / nitrogen ratio of the leaves of different height did not differ significantly. The C / N ratio (67.58) of newly-fir-fir leaves was significantly higher than that of the leaves of different height. Net nitrogen release started when the C / N ratio of Chinese fir leaves was 45.91 ± 0.45. The δ15N values of freshly-dead Chinese fir leaves and the persistent leaves at 8-10 m were significantly higher than those of other highly-preserved leaves, while the δ15N contents of other highly-preserved leaves showed no significant difference. There was no significant difference of δ13C in the leaves of Chinese fir in different heights. The polysaccharide carbon and acetal carbon in the leaves of Chinese fir were first decomposed, whereas the decomposition rate of alkyl carbon, aromatic carbon, phenolic carbon and carboxyl carbon was slower than that of polysaccharides carbon and acetal carbon.