Effects of tropical rainforest conversion to rubber plantation on soil quality in Hainan Island, China
Abstract. Land-use changes can alter soil properties and thus affect soil quality. Our understanding of how forest conversion (from tropical rainforest to rubber plantations) affects soil properties and soil quality is limited. An ideal testing ground for analyzing such land-use change and its impacts is Hainan Island, the largest tropical island in China. Based on 21 soil physicochemical and biological properties, a soil quality index (SQI) employed principal component analysis to assess soil quality changes from the conversion of tropical rainforests to rubber plantations. The results showed that (i) soil available potassium, available phosphorus, microbial biomass carbon, cellulose decomposition, acid phosphatase, and urease were vital soil properties for soil quality assessment on Hainan Island. (ii) The SQI of rubber plantations decreased by 26.48 % compared to tropical rainforests, while four investigated soil properties (soil pH, total phosphorus, cellulose decomposition, and actinomyces) increased. (iii) The SQI of both the tropical rainforests and rubber plantations showed significant spatial differences, which, under tropical rainforests, was more sensitive to seasonal changes than those under rubber plantations. (iv) Structural equation modeling suggested that forest conversion directly impacted soil quality and, indirectly impacted soil qualities' spatial variation by their interaction with soil types and geographical positions. Overall, though the conversion of tropical rainforest to rubber plantation did not decrease all soil properties, the tropical rainforest with its high soil quality should be protected.
Rui Sun et al.
Rui Sun et al.
Rui Sun et al.
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The manuscript “Effects of tropical rainforest conversion to rubber plantation on soil quality in Hainan Island, China” aims at assessing the impact of rainforest conversion to rubber plantations on soil quality by comparing changes in a soil quality index (SQI) based on 21 soil chemical and biological parameters.
The comparison would require either i) a diachronic approach in which the same sites would be investigated before and after conversion or ii) a synchronic (space-for-time) approach by comparing forest and rubber sites for which differences in pedo-climatic conditions and land-use history have been controlled for to avoid any confounding variables. This study chose the second approach but the design does not to control for confounding variables. This can be read in Table 1 (as well as seen in Figure 1). Plot are not paired by land-use and the selection is not made random, stratified or any selection other approach. Forest plots are at much higher altitude and on different soil type than rubber plantations.
Consequently, differences in SQI cannot be assigned solely to land-use changes and might arise from other differences in pedoclimatic conditions, for instance. Since the design is not appropriate for the aim of the manuscript, I do not advise for its publication.