关键词: 树干液流, 毛红椿, 人工林, 坡位, 环境因子

Abstract: Exogenous sulfur input is one of the most important factors that acidify grassland soils, which may inhibit mineralization of soil organic matter and facilitate organic carbon accumulation, but may contribute to the decomposition of carbonates in calcareous soils. Sulfur inputs enhance the availability of nitrogen and micronutrients (iron, manganese, copper, zinc and boron), decrease the availability of molybdenum, accelerate the leaching of exchangeable base cations, and reduce the availability of calcium, magnesium and potassium. Sulfur inputs increase the availability of phosphorus in calcareous and neutral soils, but decrease it in acid or strong acid soils. Exogenous sulfur inputs can improve the synergetic uptake of nitrogen and phosphorus by plants, and generally increase plant uptake of metallic micronutrients. Soil acidification induced by sulfur inputs might lead to plant manganese toxicity, which could increase plant manganese uptake but inhibit plant iron uptake. High inputs of exogenous sulfur and soil acidification can decline aboveground productivity and plant species diversity in grasslands. Low dose of sulfur input tends to improve aboveground productivity, but its effects on plant species diversity and community stability remain unclear.

Key words: environmental factors., Toona ciliata var. pubescens, plantation, sap flow, slope position