Litter removal and nitrogen deposition alter soil microbial community composition and diversity in a typical rubber (Hevea brasiliensis) plantation of Hainan, China

Abstract

Litter manipulation and nitrogen (N) deposition modify the soil microbial communities owing to the modifications in carbon input and soil nutrient availability. However, the mechanism behind the effects of litter removal (LR), N deposition, and their interactions on the diversity, richness and composition of soil microbial communities in tropical rubber (Hevea brasiliensis) plantation of China remains to be studied. To fill this research gap, we established a simulation field experiment to remove the rubber litter under the different anthropogenic inputs of N in Hainan island in 2019. The experiment included eight treatments: no N deposition (CK), low-N deposition (LN, 5 g N m⁻² yr⁻¹), medium-N deposition (MN, 10 g N m⁻² yr⁻¹) and high-N deposition (HN, 20 g N m⁻² yr⁻¹) with the LR and litter left intact (LI), respectively. Soil samples were collected from the top 0–10 cm layer, and the high-throughput sequencing was conducted to quantify the soil community structure and diversity of bacteria and fungi. Overall, HN treatment considerably diminished the bacterial Shannon index by 7.3 % but elevated the fungal Chao1 index by 18.6 % in the LI soil. Moreover, LR markedly decreased bacterial Chao1 index by 4.2 %, Shannon index by 6.3 %, and fungal Chao1 index by 20.0 % under MN treatment and those of fungi under HN deposition. Structural equation model indicated that increased NO₃⁻-N concentration reduced bacterial Shannon index driven by LR and elevated N deposition, while the LR boosted the activity of cellulase, which resulted in a decrease in fungal Chao1 index. PCoA analysis indicated that N deposition altered the bacterial communities more substantially than fungal communities, whereas LR led to distinct shifts in the bacterial and fungal communities. Furthermore, redundancy analysis indicated that alterations in soil NO₃⁻-N and light fraction organic carbon (LFOC) were the primary factors influencing soil bacterial and fungal community compositions, respectively, which were driven by N deposition and litter manipulation. Conclusively, N deposition strengthened the adverse impact of litter removal on the soil microbial community, which in turn adversely affects the sustainable development of rubber forest ecosystems. These findings suggested that maintaining adequate litter cover and N inputs is essential for rubber plantation management, as it has a positive synergistic effect on the diversity and composition of soil microbial communities.