| Soil total nutrients, available nutrients, pH and conductivity are all important soil chemical factors, and they are significant indexes of soil fertility and directly affect the release of nutrients, nutrients availability and the capacity of fertilizer conservation of soil. Taking the soil in the core area of moso forest in Shunan Bamboo-sea, Yibin, Sichuan, as study project, using methods of kilometer grid distribution points, statistics and geostatistics, the space distribution features of soil organic matter (SOM), total nitrogen (TN), rapidly available potassium (RAK), available phosphorus (AP), alkali-hydrolyzale nitrogen (AHN), pH and conductivity were investigated. On this basis, the quality of soil chemical fertility in this area was evaluated, and quality grade figures were also painted, aiming to provide reference for local management of moso bamboo and soil improvement. The present study may be of great significance for the fast and healthy development of ecological bamboo forest tourism in the meaning of theory and practice. The main results of this study are listed as follows:(1) Through statistical analysis, the same indicator was found to has the same degree of variation in different soil layers, with a maximum variable coefficient value of less than 5%, which indicated that the degree of variation is not affected by soil depth. Except for pH which has a weak variation, all the other chemical indexes were characterized by moderate intensity variations, with a variable coefficient range from 10 to 100%. The mean value suggested that, apart from pH and RAK, the contents of all the chemical indexes were higher in the soil layer of 0-20 cm than those of 20-40 cm, which revealed that soil nutrients has a trend of decrease with the increase of soil depth. The upper layer (0-20 cm) and the lower layer (20-40) has a similar pH, with a value of 4.78 and 7.95, respectively. This results suggested that the soil of the study site was acid, and relatively steady in the 0-40 cm layer. As to distribution pattern, AP in 0-40 cm and AHN in 20-40 cm have logarithmic normal distributions, and all other indexes have normal distributions.(2) Via semivariance analysis, the spatial correlation degrees of a specific chemical index in differing soil layers were found to be similar. The block ratio of pH was greater than 25%, with a medium spatial correlation. The block ratios of other indexes were lower than 25%, indicating that they have significant spatial correlation, and they were mainly affected by structural factors. From the view of codomain, both of which were higher than sample distance, ranging from 106.31 to 1952.56 m, which indicated that the used method of kilometer grid distribution points in the present study is reasonable. The theoretical semi-variance function models of a specific index in different soil layers were the same from the point of fitting model.(3) In the same soil layer, the spatial distribution patterns of SOM, TN and AHN were similar, with a pattern of clustered distribution. Their trend of regional distributions were not obvious, approximately showing a pattern of lower in west, and higher from centra to east. The relatively high value range was in part of central and northeast area. The spatial distribution pattern of AP in the two soil layer varied, and regional distributions were neither obvious, mainly showing a clustered distribution pattern. Spatial distribution pattern of pH in 0-20 and 20-40 cm soil layers were similar, with a interlaced distribution pattern of block and belt shape. The pattern displayed a trend of pH value decrease from west to east. Similarly, the spatial distribution of conductivity varied in the two soil layers, mainly displayed a clustered distribution, and debunching distribution in 0-20 cm layer.(4) The soil chemical fertility was calsified into five classed in the study site, and the area of these classes was class â…¢> class â…¡> class â…£> class â… > class â…¤. The study suggested that half of the investigated area with moso bamboo forest has relatively high productivity. Spacial distribution of soil fertility in the study site is mainly clustered distribution, the soil fertility classes in central and northeast are relatively high, while those in west and southeast relatively low which may be mostly attributed to the anthropic factors. To improve the soil fertility, ways of operation and management should be improved, with reasonable exploration and planning, suitable fertilization and control measures, such as P and K for fertilization, facilitating passenger flow in peak tourist seasons, etc. |
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