Land use change is one of the greatest threats to soil biodiversity and ecological functions. Tropical deforestation for the establishment of monoculture cash tree plantations poses the greatest threats to biodiversity. However, how such a transition affects soil carbon (C) and nitrogen (N) dynamics driven by fungal communities at the aggregate level remains unclear. 

In a study published in Science of The Total Environment, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) assessed the impact of tropical land use change on soil fungal functional guilds and the effects on soil C and N cycling processes at the aggregate level. 

The researchers determined C and N fractions, fungal communities, enzymatic activities and chemical properties within three soil aggregates in a natural forest, 12- and 24-year-old rubber monocultures and corresponding agroforestry systems in Xishuangbanna, SW China.  

They found that the varying effects of land use change on soil C and N dynamics mediated by fungal functional guilds across aggregate sizes. The C and N pools in all aggregates were generally reduced when tropical forests were converted to rubber monocultures. The microbial biomass C and N decreased in agroforestry systems. 

Carbon- and N-degrading enzyme activities responded differently to forest conversion and were enhanced in agroforestry systems. As the soil aggregate size decreased, the levels of C and N pools and their related enzyme activities increased.  

Moreover, pathogenic fungi increased at the expense of saprotrophic and symbiotic fungi when forest was converted. The soil aggregate size affected the fungal diversity rather than composition, with the highest diversity in microaggregates. C and N pools within aggregates were variedly affected by fungal functional guilds, mainly driven by soil pH, regardless of land use type. According to the researchers, all the differences were attributed to changes in species diversity, soil properties and involved agroforestry management. 

"Our study provides an important insight into the early establishment of agroforestry systems in tropical cash tree plantations due to the greater advantages in nutrient cycling and pathogen control,” said LIU Chenggang of XTBG. 

Contact 

LIU Chenggang Ph.D 

Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China                        

E-mail:  liuchengang@xtbg.ac.cn      

Published: 5 August 2023