甘肃兴隆山森林演替过程中的土壤理化性质

在森林群落恢复演替过程中,由于森林类型及其所处立地环境不同,森林与土壤相互作用过程具有复杂性。以甘肃兴隆山6种森林类型(青杄林、青杄-白桦林、山杨-白桦林、灌丛林、落叶松林和油松林)0—60 cm土壤层为研究对象,探讨森林恢复演替过程中土壤理化性质的变化规律,旨在为该区域退化森林生态系统恢复与重建提供依据。结果表明:1)在土壤剖面上,兴隆山森林土壤容重随深度的增加而逐渐增大,总孔隙度、毛管孔隙度、自然含水量、最大持水量、毛管持水量、田间持水量均随深度的增加而减小;pH值差异不显著,无明显变化规律;土壤有机质、全N、水解N、有效P、速效K均随深度的增加而变小,表聚效应明显;全P差异不显著,呈"圆柱体"分布模式;2)在森林恢复演替过程中,天然林容重、孔隙度、持水能力、渗透性明显好于人工林,随森林正向演替的进行,天然林容重不断减少,孔隙度明显改善,通透性能不断增强,而人工林土壤物理性质出现明显退化现象;天然林pH值在演替方向上并未表现出酸化现象;天然林土壤有机质、全N、水解N、有效P和速效K变化规律不明显,但总的变化趋势为先增加后减小;3)有机质与全N、水解N、最大持水量、毛管持水量、田间持水量呈显著正相关,而与容重呈显著负相关;全N与水解N呈显著正相关;土壤有机质在改善土壤理化性质和促进养分循环方面具有重要作用,已成为植被恢复过程中土壤变化的一个重要标志。

Soil physical and chemical properties in forest succession process in Xinglong Mountain of Gansu

The interactions between forest and soil are complex in the process of forest community succession and recovery due to the difference in forest types and site environment conditions. In this study, we selected the Xinglong Mountain located in Gansu province as study area to quantify the response of soil properties to the forest succession and recovery processes. Soil physical and chemical properties in depth of 0-60 cm layers under 6 main forest covers including Picea wilosonii pure forest, Larix principis-rupprechtii pure forest, Pinus tabulaeformis pure forest, Picea wilosonii and Betula platyphlla mixed forest, Populus davidiana and Betula platyphlla mixed forest, Cotonester multiglorus and Rosa xanthina mixed shrubs were analyzed, based on field sampling and laboratory test. The results showed that: (1) The value of bulk density in forest soil of Xinglong Mountain increased with the increasing of soil depth in the 0-60cm soil layers, while the soil physical properties including the soil porosity, capillary porosity, soil water content, field maximum water capacity, capillary water capacity and field capacity were all decreasing with the increasing of soil depth in these layers. However, no significant difference of pH value was detected in the 0-60 cm soil profile. The value of soil chemical properties containing the soil organic matter, total nitrogen (TN), hydrolysable nitrogen (HN), available phosphorus (AP) and available potassium (AK) decreased with the increasing of soil depth. Profile distribution characteristics of soil chemical properties showed obvious accumulation effect in the top soil layers. However, no significant difference of total phosphorus (TP) had been found in the top and deeper soil layers. The profile distribution of total phosphorus appeared a "cylinder" distribution pattern. (2) The bulk density, soil porosity, soil water holding capacity and soil penetrability in natural forest were obviously better than that in artificial forest during the processes of forest succession and restoration. The bulk density in natural forest was gradually degrading, but the soil porosity and soil perviousness were enhancing with the positive succession of natural forest community. Nonetheless, compared with the dynamics of soil properties in natural forest, the soil physical properties in artificial forest presented an obviously degeneration in the entire soil profile. No obvious acidification phenomenon was detected during the succession of natural forest by pH value test. Furthermore, no obvious change in soil chemical properties including soil organic matter, total nitrogen, hydrolysable nitrogen, available phosphorus and available potassium had been found during this process. Generally, the trend of soil chemical properties in natural forest was that the value increased in early stage but decreased in latter period. (3) The observation in this study showed a significant positive correlation between soil organic matter and total nitrogen, hydrolysable nitrogen, field maximum water capacity, capillary water capacity and field capacity. The correlation analysis showed the total nitrogen also had a significant positive correlation with hydrolysable nitrogen, the soil organic matter on the other hand showed a significant negative correlation with soil bulk density. These findings indicated that the soil organic matter played an important role in improving soil physical and chemical properties as well as promoting the soil nutrient cycling. For practice, the soil organic matter can be employed as an indicator of soil properties change during the process of vegetation restoration. The results of this study can provide scientific guidance for the restoration of degenerated forest ecosystem in this area.