TROPICAL GEOGRAPHY ›› 2019, Vol. 39 ›› Issue (1): 144-152.doi: 10.13284/j.cnki.rddl.003099

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Effects of Land Use Patterns on Soil Organic Carbon and Easily Oxidized Organic Carbon in the Eastern Part of Hainan Island

Zhao Zhizhong, Li Yan, Zhao Zeyang, Xing Yaoli and Liu Yuyan   

  1. (College of Geography and Environmental Science, Hainan Normal University, Haikou 571158, China)
  • Received:2018-08-15 Revised:2018-11-15 Online:2019-01-05 Published:2019-01-05

Abstract: Hainan Island is located in the southernmost region of China. In recent decades, with the rapid economic development of Hainan Province, the intensity of human activities has gradually increased and the land use mode in the region has changed greatly. Changes in land use patterns have exacerbated the corresponding changes and release of soil organic carbon (SOC) in Hainan Island. The distribution characteristics of SOC and readily oxidized carbon (ROC) in four land use patterns (paddy field, abandoned land, orchard land, rubber forest land) in the eastern part of Hainan Island were investigated. The results show that land use patterns had significant effects on the distribution of SOC and ROC via the influence of vegetation litter, root system, tillage method, fertilization, and harvesting. The SOC content in the profile of 30 cm of soil in the eastern part of Hainan Island is 0.79~0.97 g/kg, the average value is 10.09 ±1.02 g/kg, and the coefficient of variation is 0.88 g/kg. For soil profiles of 0~30 cm, there are differences in the SOC and ROC content for different land use patterns. Considering the entire soil profile (0~30 cm), the distribution characteristics of the SOC content for the four land use patterns are as follows: paddy field > abandoned land > orchard land > rubber forest land, and the apparent accumulation of SOC is evident for different land use patterns. As the soil layer increases, the content of the SOC gradually decreases. Under different land use patterns, the content of the ROC in soil is as follows: abandoned land > paddy field > orchard land > rubber forest land. The content of the ROC in the paddy field, orchard land, and rubber forest soil gradually decrease with an increase of the soil depth. However, the abandoned land exhibit an initial decrease followed by an increase in the ROC content. The distribution ratio of soil ROC in the eastern part of Hainan Island is between 41% and 94%, which is higher than the results obtained from previous studies. This is because the study area is associated with a tropical monsoon climate, suitable water and heat conditions, and larger plant biomass. Moreover, sufficient exogenous SOC input is provided for the soil. In addition, the number, activity, plant metabolic rate and litter decomposition of soil microbes are accelerated, resulting in more root biomass and exudates. This promotes the decomposition and transformation of SOC, which is beneficial to the accumulation of soil ROC. In the 0 ~ 30 cm soil profile, the SOC content of paddy field is the highest, but the distribution ratio of ROC is the lowest. The prolonged flooded environment of paddy fields is favorable to the accumulation of SOC and the activity of this organic carbon is lower. As a result, soil stability and maturity are higher than for other land use methods. Correlation analysis show that the SOC and ROC content of the paddy field, abandoned land and rubber forest land, has a significant positive correlation with ROC content. Moreover, SOC content in orchard soil has a significant positive correlation with ROC content under different land use patterns.

Key words: land use types, soil organic carbon, readily oxidized carbon, East Hainan Island