热带、亚热带典型森林-土壤系统植硅体碳演变规律

分别选取中国亚热带毛竹林、马尾松林、青冈林、杉木林和热带青梅林、芭蕉林、橡胶林、马占相思林8种森林类型,采集其鲜叶、凋落叶以及0～10和10～30 cm土层土壤,通过微波消解法提取其中的植硅体,并采用碱溶法测定植硅体中碳含量.结果表明: 4种亚热带森林类型鲜叶、凋落叶和0～10 cm土层中植硅体碳含量均以马尾松林(230.24、229.17、20.87 g·kg^-1)最高,毛竹林(30.55、37.37、3.38 g·kg^-1)最低,10～30 cm土层则以青冈林(18.54 g·kg^-1)最高,毛竹林(2.90 g·kg^-1)最低.热带森林鲜叶中植硅体碳含量以马占相思林(377.66 g·kg^-1)最高,青梅林(46.83 g·kg^-1)最低,凋落叶中则是橡胶林(218.23 g·kg^-1)最高,芭蕉林(27.66 g·kg^-1)最低,而0～10和10～30 cm土层土壤中均以马占相思林(23.84、24.90 g·kg^-1)最高,芭蕉林(3.89、3.93 g·kg^-1)最低.与0～10 cm表层土相比,杉木林、青冈林、马尾松林、毛竹林、橡胶林、马占相思林、芭蕉林和青梅林鲜叶植硅体碳含量分别下降97.4%、94.9%、90.9%、88.9%、95.9%、93.7%、93.3%和63.7%.青冈林、芭蕉林和马占相思林鲜叶植硅体碳含量显著高于凋落叶,而毛竹林、马尾松林、杉木林、青梅林和橡胶林之间无显著差异.8种森林类型土壤植硅体碳含量均显著低于鲜叶和凋落叶,表明植硅体在通过凋落物释放到土壤的过程中是不稳定的.

Evolution pattern of phytolith-occluded carbon in typical forest-soil ecosystems in tropics and subtropics,China

Samples of fresh leaves and leaf litter, as well as soils taken from 0-10 and 10-30 cm layers, were collected in four types of typical forest ecosystems both in subtropical (Phyllostachys pubescens, Pinus massoniana, Cycloba lanopsisglauca, and Cunninghamia lanceolata stands) and in tropical climates (Vatica mangachapoi, Musa basjoo, Heveabrasiliensis, and Acacia mangium stands) for measurement of PhytOC (phytolith-occluded organic carbon) contents. The phytoliths in both leaves and soil samples were extracted by a microwave digestion method and their PhytOC contents were determined by alkali dissolution-spectrophotometry method. It was found that, among the four types of subtropical forests, the PhytOC contents of leaves, litter and 0-10 cm soil layer were the highest in P. massoniana stand (230.24, 229.17 and 20.87 g·kg^-1), the lowest in P. pubescens stand (30.55, 37.37, and 3.38 g·kg^-1), and the PhytOC content of the 10-30 cm soil layer was the highest in C. glauca stand (18.54 g·kg^-1), and the lowest in P. pubescens stand (2.90 g·kg^-1). For the four tropical forests, A. mangium stand (377.66 g·kg^-1) and V. mangachapoi stand (46.83 g·kg^-1), respectively, deposited the highest and lowest contents of PhytOC in the leaves, while the highest and lowest contents of PhytOC in the litter were observed in H. brasiliensis stand (218.23 g·kg^-1) and M. basjoo stand (27.66 g·kg^-1), respectively. Also among the tropical forests, the highest PhytOC contents in the 0-10 cm and 10-30 cm soil layers were observed in A. mangium stand (23.84 and 24.90 g·kg^-1), while the lowest values occurred in M. basjoo stand (3.89 and 3.93 g·kg^-1). The PhytOC contents in transitioning from leaves to soils (0-10 cm layers) decreased by 97.4% for C. lanceolata, 94.9% for C. glauca, 90.9% for P. massoniana, and 88.9% for P. pubescens in the subtropics, and by 95.9% for H. brasiliensis, 93.7% for A. mangium, 93.3% for M. basjoo, 63.7% for V. mangachapoi in the tropics. There was no significant difference in PhytOC contents between leaves and litter for the following five forest types: P. pubescens, P. massoniana, C. lanceolata, V. mangachapoi and H. brasiliensis. However, significantly higher PhytOC contents in leaves than in litters were measured in C. glauca, M. basjoo, and A. mangium. The findings that significantly lower PhytOC contents occurred in soils than in fresh leaves and leaf litter regardless of type of forest ecosystem suggested that phytolith was not stable during the pathway from plants to soil via the forest litter.