粤北岩溶区土壤酸化的空间分异特征研究

为了解粤北岩溶区土壤酸化的空间分异特征，选择华南酸雨区的岩溶槽谷地貌和峰丛洼地地貌土壤为研究对象，对土壤pH数据进行空间插值预测，采用参数最优地理探测器分析岩溶槽谷地貌与峰丛洼地地貌中土壤酸化的空间特征及关键驱动力。结果表明:（1）区内土壤pH范围为4.62~8.19，主要以弱酸性（5.5≤pH <6.5）和酸性（4.5≤pH<5.5）为主。在不同地貌类型中，pH<6.5的土壤样品占比顺序为:岩溶槽谷（61.0%）< 峰丛洼地（69.2%）<非岩溶区（75.0%）；（2）岩溶区小生境复杂多样，在酸雨影响下，成土母质可能是研究区内控制土壤pH的关键因子，而土壤pH空间分异格局可能是多因子共同作用的结果；（3）坡度对土壤pH空间分异的影响仅次于成土母质，表现为土壤pH随坡度的增加而升高，且其与成土母质的交互作用对研究区内土壤pH空间分异的解释力最大。区内土壤酸化防治建议:（1）根据成土母质和坡度因子进行分区分类，并在岩溶槽谷和非岩溶区内设定土壤酸化重点监测区，进行精准防治；（2）除了对酸雨的防控外，还应该重视诸如氮肥使用、工业和矿业活动等外源性因素对土壤的影响。 

Spatial variation of soil acidification in the karst area of northern Guangdong: A case in peak cluster depression and karst trough valley landforms

The process of soil acidification is very slow under the natural conditions, which generally takes decades or even hundreds of years. However, since the Industrial Revolution, human activities have greatly accelerated the process of soil acidification. The effect of acid rain is one of the main reasons for the process. The problems caused by soil acidification, such as barren soil, soil quality decline, enhanced heavy metal activities and others will affect soil microbial activities and the growth of plants, and then affect the quality of ecological environment in the whole region, hence threating the food safety and human health. Soil acidification has become an important ecological and environmental problem that has to be faced in the agriculture development of south China. Therefore, distribution of soil pH is the key to control measures for soil acidification in karst areas. In order to study the spatial variation of soil acidification in karst areas, an investigation was conducted to assess the status of soil pH in the karst trough landform and cluster-peak depression landform in northern Guangdong located in the acid rain area of south China. Methods such as normalized vegetation index (NDVI), normalized moisture index (NDWI), normalized building index (NDBI), slope aspect and gradient were used to analyze the driving mechanism of soil pH heterogeneity in cluster-peak depression and karst trough valley. The research questions are listed as follows, (1) What are the characteristics of spatial variation of soil pH in different karst landforms and what are the main influencing factors of the variation? (2) What are the driving factors and interactive effects of soil acidification in karst areas? The results show that pH values of the total soil samples range from 4.62 to 8.19 with the mean of 6.29±0.92 and the variance of 0.85; the soil pH values in karst trough valley range from 4.62 to 8.19 with the mean of 6.38±0.95 and the variance of 0.91; the pH values in cluster-peak depression range from 5.29 to 8.03 with the mean of 6.31±0.90 and the variance of 0.81; the pH values in non-karst area range from 4.71 to 7.55 with the mean of 5.99±0.92 and the variance of 0.73. Generally speaking, the average soil pH of total samples shows weak acidity, and no soil samples with strong acidity (pH<4.5) are detected, but alkaline soil samples (pH≥7.5) in some landforms are detected. The results indicate a substantial impact of acid rain on the soil pH of karst areas and the risk of soil acidification. According to the distribution frequency of soil pH values, the soil pH in the whole study area is mainly weakly acid and acid. The pH values (<6.5) of soil samples in different landforms are ranked as follows, karst trough valley (61.0%) Through the analysis of the spatial characteristics of soil pH, the variation of the mean value of soil pH presents the following rules, (1) Distribution of the soil pH shows that soil parent materials directly affect the process of soil acidification. Under the conditions of different soil parent materials, the mean values of soil pH are ranked as, non-carbonategrassland>cultivated land, indicating that the land use type, in some degree, is influential in the spatial variation of soil pH. The karst environment is very complex. With the effect of acid rain, the soil parent materias, which may be the key factor to control the soil pH in the study area, directly affect the process of soil acidification. But distribution of soil pH spatial variation may be caused by multiple factors. In general, soil pH values in the study area show an increase with the rise of gradient. The influence of gradient on soil pH spatial variation is followed by that of soil parent materials. The interactive effect of gradient and soil parent materials shows great explanatory power for the spatial variation of soil pH in the study area. Therefore, soil acidification control is advisably to be carried out in northern Guangdong, and the gradient factor should be taken as one of the indicators. Besides the influence of acid rain, other exogenous factors such as nitrogen fertilizer, and industrial and mining activities, should also be paid attention to. With the integration of geostatistics, the geodetector is used to further analyze the driving factors of soil pH spatial variation and their interactive effects in the karst area in north Guangdong, based on the forecast of soil pH kriging spatial interpolation. However, the effect of rocky desertification and the scaling effects of different sizes of spatial statistical units on the geodetector model have not been fully explored. These limitations will be overcome in the future research.