Introduction of a leguminous shrub to a rubber plantation changed the soil carbon and nitrogen fractions and ameliorated soil environments

Chang-An Liu,Yan-Ming Zhang,Kadambot H M Siddique,Jian-Wei Tang,Yu Nie

doi:10.1038/s41598-018-35762-0

Abstract

The conversion of monoculture rubber (Hevea brasiliensis) plantations into rubber-based agroforestry systems has become a common trend in forestry management in the past few decades. Rubber–Flemingia macrophylla (a leguminous shrub) systems are popular in southwestern China’s Xishuangbanna region. The biogeochemical cycles of soil carbon and nitrogen in forests are mainly affected by their fractions. This study investigated the effect of introducing Flemingia macrophylla to rubber plantations of different ages on soil carbon and nitrogen fractions. The experimental treatments included R1 (young rubber plantation), RF1 (young rubber–Flemingia macrophylla system), R2 (mature rubber plantation) and RF2 (mature rubber–Flemingia macrophylla system). The results showed that the introduction of Flemingia macrophylla to rubber plantations of different ages significantly changed soil carbon and nitrogen fractions, improved soil labile organic carbon and nitrogen contents, and ameliorated soil environments. The average soil microbial biomass organic carbon, nitrogen and nitrate-nitrogen in the 0–10 cm soil layer during the experimental period was 38.9%, 55.5%, and 214.7% higher in RF1 than R1, respectively, and 22.1%, 22.2%, and 652.2% higher in RF2 than R2, respectively. Therefore, Flemingia macrophylla can be used as an alternative interplanted tree species within rubber plantations in similar environments of southeastern Asia.

Highlights

Monoculture rubber (Hevea brasiliensis) plantations have rapidly expanded in the last few decades in southeastern Asia[1,2]
The soil organic carbon (SOC) content in the 0–10 or 10–30 cm soil layers did not differ between the plantation treatments (R1, R2, RF1, RF2) for the duration of the study (April 2014 to January 2017) (Table 1)
In the 10–30 cm soil layer, the introduction of Flemingia macrophylla to the rubber plantations had no significant effect on water-soluble organic carbon (WSOC) content

Summary

Introduction

Monoculture rubber (Hevea brasiliensis) plantations have rapidly expanded in the last few decades in southeastern Asia[1,2]. Rapid growth in the Chinese economy has increased demand for natural rubber In response to this demand, the natural tropical forests of southwestern China’s Xishuangbanna region were deforested and replaced with more than 470,000 ha of rubber plantations, which equates to more than 24% of the total land area of the region[4]. Rubber plantations have lower mean CH4 uptake rates than secondary and tropical forests[22] These transformations and biogeochemical cycles of soil carbon and nitrogen are mainly affected by their fractions[23,24,25,26,27] that play essential roles in the turnover of nutrients in soil, including water-soluble organic carbon (WSOC), light fraction of organic C (LFOC), microbial biomass organic C (MBC), ammonium N (AN), nitrate N (NN), light fraction of organic N (LFON), and microbial biomass organic N (MBN). Little is known about the effect of these systems on soil carbon and nitrogen fractions

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