盐度对秋茄凋落叶分解过程中物质与能量动态的影响

Influences of salinity on mass and energy dynamics during decomposition of Kandelia candel leaf litter

在室内人工模拟潮汐,研究了4种盐度(0、10‰、25‰和35‰,分别代表淡水、低盐、中盐和高盐)下秋茄(Kandelia candel)凋落叶分解过程中物质与能量动态的差异。结果表明,高盐处理下的失重率和平均分解速率显著低于淡水和低盐处理,而高盐下的半分解理论值则高于其他处理;盐度对分解过程中的残叶氮磷变化动态有显著影响,其中,残叶氮的释放速率在实验后期会随着盐度的升高而上升,高盐度下残叶总氮含量显著低于低盐或淡水处理;而在分解第1周,淡水或低盐处理能加速磷的释放,但中高盐度残叶中总磷含量最终会低于淡水和低盐处理;盐度同样能对残叶热值产生显著影响,淡水和低盐处理下的碎屑热值要显著高于高盐处理下的残叶热值,但不同盐度下分解的能量损失差异不显著。

Aims Our objective is to investigate the impact of salinity on decomposition of Kandelia candel leaf litter. Methods Four laboratory treatments with different salinities （0, 10‰, 25‰ and 35‰ salinity, representing fresh water and low, medium and high salinity treatments, respectively） were set up to simulate tidal conditions for leaf litter decomposition. We analyzed dry weight, nitrogen （N） and phosphorus （P） contents, their release rates and energy loss of leaf litter at different decomposition stages under these four treatments. Important findings Percentage weight loss and mean rate of decomposition （MRD） in high salinity treatment were significantly lower than in fresh water and low salinity treatments. Theoretical time required for 50% loss of dry weight of leaf litter was highest in high salinity treatment. Salinity significantly affected the dynamic variation of N and P in leaf detritus. The N release rate of leaf detritus tended to increase with higher salinity, resulting in lowest N content in the high salinity treatment. During the first week, fresh water and the low salinity treatment were found to accelerate the release of P, but P content was lower under medium and high salinity than other treatments. The caloric values of leaf detritus were significantly higher in fresh water and low salinity treatments than in the high salinity treatment; however, no significant difference was found in percentage energy loss during decomposition under different salinities.