Impact of rubber tree plantations on soil functional biodiversity and soil organic carbonwca2014-2447 Alain D. Brauman 1 2,*Frederic Gay 3 4Monrawee Monrawee 5 6Marin Lafaye De Micheaux 2Tiphaine Chevalier 7Chayawat Chompunut 8Henri Robain 1 9Choosai Chutinan 10David Sebag 11 12Nopmanee Suvannang 5 13 1LMI LUSES, 2UMR ECO&SOLS, IRD, 3HRPP, 4UMR ECO&SOLS, CIRAD, 5LMI LUSES, 6Soil Biotechnology, LDD, Bangkok, Thailand, 7UMR ECO&SOLS, IRD, Montpellier, France, 8DORAS, Kasetsart University, 9UMR BIOEMCO, IRD, Bangkok, 10Department of Plant Science and Agricultural Resources, Khonkaen University, Khon Kaen, Thailand, 11UMR M2C, IRD, Ngaoundéré, Cameroon, 12UMR HSM, IRD, Montpellier, France, 13Office of Soil Science, LDD, Bangkok, Thailand
The Mekong sub-region faces an exceptional expansion of rubber tree plantations, which represent a potential problem in terms of soil sustainability. However, in comparison with intensive annual cropping, rubber tree plantation could also have a positive impact on soil functioning but data concerning its influence on soil environment remains scarce. To address this question, we investigated the impact of rubber tree plantations on soil organic carbon (SOC) and soil biological diversity (soil fauna and microorganisms) related to main soil functions such as OM mineralization and nutrient cycling. All the biologic and physical-chemical parameters were measured from the same sampling set along a rubber tree chronosequence in the eastern province of Thailand, and compared to the former crop cultivated (cassava). Compared to cassava field, most of the variables measured (SOC, soil respiration, microbial activities and density, fauna density and diversity) showed significantly higher level only in the old rubber plantations (23-25 years). However, the shift from cassava to young rubber plantations (< 7 years old) resulted first in a depletion of all these parameters. The soil ecosystem started to recover from the land use change after the closing of the canopy of the plantation. At this stage, aboveground and belowground litter started to accumulate significantly in the system. Interestingly, soil fauna structure varied according to plantation age, while bacterial structure depended more on land use change (cassava vs. rubber). These increasing biological activities seemed to participate to a significant change in OM quality (Rock Eval results). These results suggest that planting rubber trees could be a better alternative than cassava crops in terms of soil sustainability. This first study needs to be generalized through an extension towards other crop systems and soil types.