【作者】 李恩香；

【导师】 蒋忠诚； 李先琨；

【作者基本信息】 广西师范大学 ， 生态学， 2002， 硕士

【摘要】 生态系统退化问题是阻碍国民经济发展的重大问题。在岩溶分布广泛的广西，生态系统退化问题更加严重，如何进行岩溶区生态系统的恢复和重建，成为广西当前的重大课题。要恢复和重建我区退化的生态系统，必须明确岩溶植被演替的规律及动力机制。目前对岩溶植被演替过程中生态因子的研究较少，一些规律还没有查清，不利于进行有关方面的决策。本研究通过对广西的热带、南亚热带、中亚热带等多种岩溶植被类型，不同演替阶段群落的主要土壤因子、群落小气候、岩溶水及岩溶动力条件的调查，力图对岩溶植被演替的一些规律进行初步探讨。研究表明，植被正向演替可增加对土壤中有机物质的输入，但因不同植被输入方式和利用能力不同，使土壤物质出现剖面异性。随植被改善，土壤中有机C、N和有效N的含量增加，但演替后期其B层也会出现较低值；土壤pH值随正向演替而降低；但当Ca、Mg含量明显增高时，也会出现升高的趋势；土壤中P和有效P的含量随植被演替的变化不明显；K和有效K的含量随正向演替有下降的趋势；因脱钙和钙积在土壤中反复进行，Ca含量变化复杂，Mg的变化与Ca呈负相关。演替初期土壤的孔隙度和含水量增加，容重降低；而演替后期，较深层的土壤孔隙度和含水量有下降趋势。土壤CO2因影响因素多而变化复杂。土壤理化性状是各种因素综合影响的结果，植被引起土壤理化性状的变化是明显的，但空间的异质性增加了变化的复杂性，甚至可将植被引起的变化掩盖住。随植被的改善，群落内光照强度、气温、土温均明显降低，日变幅减小；而群落内空气的相对湿度明显升高，变幅减小。裸岩阶段光照最强，气温、土温最高，相对湿度最低，变化最剧烈；顶极群落内光照最弱，气温土温最低，相对湿度最大，变幅小，最稳定。随植被的改善，群落朝向阴、湿、冷和稳定的方向发展，具有了更大的调节能力，为其它生物及人类的生存提供了一个舒适的空间；也为中生性树种的生存，即为群落的进一步演替创造了条件。植被的改善可以增强对岩溶水的调蓄能力，减少降雨引起水土的流失，使岩溶泉水的流量动态变稳定。这对于岩溶山区，解决居民的饮水，甚至农业用水的问题都具有重要意义。说明植被恢复是生态系统恢复的前提和关键。植被的改变<WP=5>也在水化学中体现出来，随植被正向演替水中pH值与土壤pH值一样呈降低趋势；植被正向演替使水中溶解的物质大大增加，便于植物对营养物质的利用，加速了物质在不同圈层间的循环；植被改善使水的侵蚀能力增强，加速了成土作用。土壤中岩石试片的溶蚀率随正向演替而增加，并与土壤CO2、有机C和N含量呈正相关，与pH值，Ca、Mg含量呈负相关。演替进展还可促进土壤的潜蚀作用。随植被的改善，群落产生了更多的有机物质，有机物的分解产生了更多的CO2和有机酸，降低了pH值，促进了Ca、Mg等物质的循环，改善了岩溶动力条件，促进了岩溶区土壤的形成。以上生态因子的变化是许多因素综合作用的结果，时间、气候、地质条件等因素，都会引起生态因子错综复杂的变化，所以许多问题值得进一步深入探讨和研究。但可以得出一个基本的结论：广西岩溶植被的退化和石漠化也引起其它生态因子恶化，要从根本上改善岩溶生态环境，必须进行岩溶植被的恢复和重建，这是岩溶生态系统良性循环的关键所在。更多还原

【Abstract】 The deterioration of ecosystem in karst areas in Guangxi is very serious, which hinders local economic development and environmental improvement, and becomes one of key problems in the province. How to reconstruct the ecosystem is also one of the major projects in Guangxi today. It is necessary to understand the law and mechanism of the succession of karst vegetation. Moreover, we should study the eco-factors in different vegetations in the process of succession. It is available to look for the best way for the rehabilitation of vegetation in karst areas. So far, few studies on the eco-factors have been conducted from the perspective of vegetation succession. In this paper, the main types of karst vegetation in Guangxi, including that of tropical, south sub-tropical, and central sub-tropical are studied. Some characteristics of the major factors, including the soil, the microclimates, the karst water in karst springs and the karst dynamic conditions, are discussed.The research shows: soil organic C, total N and available N increase as succession proceeds, but the tendency is different with the depth. It is significant in layer A, slight in layer B and may even decrease in anaphase. While soil pH value, total K, and available K decrease, but no noticeable trend was found in the case of soil P and available P during the succession. Soil pH value can also increase when soil Ca and Mg increase along the succession series. Because Ca in the soil can be lost and accumulated by the plant, the changes of soil Ca and Mg are complex. The soil CO2 is more complex due to various factors. Progressive succession can improve the physical characteristics of upper layer of the soil: reduce soil bulk density raise soil porosity and water content; but may raise soil bulk density and reduce soil porosity in the lower layer. Although the changes of the chemical and physical characteristics of soil caused by vegetations are obvious during the succession process, they can be affected, positively or negatively, by various factors, such as the habitat heterogeneity.<WP=7>Light intensity, air and soil temperatures decrease while relative humidity increases, and the daily fluctuations become less significant, As succession advances. So the microclimate evolves into a darker, colder, and damper condition and the decrease in fluctuation of the microclimate leads to a more stable environment. In the bare rock stage, the light intensity, air and soil temperatures are the highest, while the relative humidity is the lowest, and the microclimates change violently. It is not suitable for life at this stage. While the light intensity, air and soil temperatures are the lowest, relative humidity at its highest, and the fluctuations are the slightest in the climax community stage. It has stronger ability to regulate the environment and is more suitable for life.With the vegetation advanced, the ability to regulate the karst water gets stronger. And the forest at climax community stage can keep the epikarst spring stable and make it ever-flowing. It is of great importance to solving the problem of water shortage, shortage of drinking water and even water for irrigation, in karst mountain areas. It suggests that the recovery of vegetation is the premise to the restoration and reconstruction of the degraded ecosystem. The chemical characteristics of karst water also change along the succession series. Water pH value decreases just like that of the soil, and the solutes in water increase significantly. The nutriments become easier for the plant to absorb. And it accelerates the cycle of material and the process of soil formation. The dissolution intensity of limestone tablets in soil increases as the vegetation improves; and shows positive correlation to soil CO2 concentration, the amount of soil organic C and N; negative correlation to the amount of Ca、Mg in soil. The succession accelerates the dissolution intensity of limestone tablets in lower layer of soil more greatly than the upper layer. It suggests that better vegetation can produce更多还原