川西亚高山林线过渡带及邻近植被土壤性质

研究了川西亚高山林线过渡带及邻近植被上缘流石滩草甸与下缘冷杉林残积母质土壤物理、化学和生物学特性.结果表明:从流石滩草甸→林线过渡带→冷杉林,土层逐渐增厚,表层土壤(0～30 cm)粉粒、粘粒、物理性粘粒含量、团聚度、结构系数和自然含水量逐渐增高,砂粒含量逐渐降低,阳离子交换量(CEC)、交换性盐基含量、盐基饱和度以及水解性酸含量逐渐增高,pH值逐渐降低,有机质及养分库全P、全K、有效N、有效P和速效K含量逐渐增高,土壤物理结构和化学性质逐步有所改善,但亚高山林线过渡带区域残积母质土壤成土过程缓慢.林线过渡带表层土壤细菌、真菌、放线菌及微生物总量,土壤脲酶、蔗糖酶、酸性磷酸酶、中性磷酸酶、多酚氧化酶及过氧化氢酶活性高于邻近植被上缘流石滩草甸与下缘冷杉林,体现了作为生态交错带,林线过渡带比邻近植被土壤具有相对较强的生物学活性.

The soil properties of the subalpine timberline ecotone and adjacent vegetations in Western Sichuan

The upper or alpine timberline(AT) can be either a transitional zone or an abrupt border between continuous forest and herb, shrub and high mountain cushion communities. At present, Although there have been more reports on their positions and dynamics which may be controlled by limitations imposed by abiotic environmental conditions such as low temperature, aridity, wind and snow on the production of viable pollen, viable seeds, seed germination and the survival of saplings and adults, but there is lack of information to understand the effects each other between changing vegetations and their soil properties in this geographical region. Therefore, in a short distance, the physical, chemical and biological properties of the soil mainly taken place in residual deposits in subalpine timberline ecotone, scree meadow and fir forest, were investigated in Wanglang National Nature Reserve in this paper. The results show that from scree meadow to timberline ecotone then to fir forest, with the changement of vegetation some physical structure parameters such as the content of scree, silt, clay and physical clay, aggregate degree, structure coefficient, and some chemical parameters such as the content of soil water, hydrolyzed acid, organic matter, total P, total K, available N, available P and soluble K, exchangeable base content, cation exchangeable capacity content, base saturation percentage and so on in the topsoil(0-30 cm) all were increasing slowly, showing that the soil physical structure and chemical properties were improved but developing slowly on the residual deposits. Furthermore, in the topsoil of the subalpine timberline ecotone, the microbe quantities of bacteria, fungi and actinomyces, enzymatic activities of acid phosphatases, neutra phosphatase, urease, invertase, catalase and polyphenol oxidase were highest among three vegetations, implying that as a ecotone, the soil biological and chemical activities in subalpine timberline ecotone were more active than them in the adjacent vegetations.