Enhancement of soil carbon and nitrogen stocks by abiotic and microbial pathways in three rubber‐based agroforestry systems in Southwest China

Abstract

AbstractAgroforestry systems are considered promising alternatives to rubber tree (Hevea brasiliensis) monocultures, but information is limited on the effects of rubber‐based agroforestry systems on soil organic carbon (SOC) and total nitrogen (TN) storage. The current study, which was conducted in Xishuangbanna, China, compared four intercropping treatments, including rubber monoculture and the follow three agroforestry treatments: intercropping withCamellia sinensis,Coffea liberica, orTheobroma cacao. Soil physicochemical properties and copy numbers ofcbbLandnosZgenes (which indicate the abundance of bacteria that function in C and N cycling) were analyzed. The results showed thatCoffea libericaintercropping facilitated SOC and TN contents and enhanced SOC and TN stocks by 36.5 and 33.2% relative to rubber monoculture at 0–10 cm soil layer, respectively. Structural equation modeling showed that the effects of intercropping oncbbLandnosZcopy numbers were mainly explained by soil pH and bulk density (r2= .37 and .35, respectively), that the abundance ofcbbLand SOC content directly affected SOC storage (r2= .46), and that the abundance ofnosZand TN content directly affected TN storage (r2= .22). Our results indicate that the use ofC.libericaas intercrops should contribute to retard soil degradation and to implement sustainable land management in rubber monocultures. Combining the abiotic and microbial pathways, we suggest that the enhancement of C and N sequestration withC.libericaunder rubber monoculture can be probably attributed to the increased input of litter and roots and to the stimulation of the microorganisms that regulate C and N cycles.