Search

After a Rubber plantation cycle (25 to 40 years), the greatest risk of soil degradation occurred during the replanting period which extends from the clear cutting of an old plantation to the planting of young rubber trees. During this period, the soil is subject to numerous disturbances mainly related to (1) the opening up of the environment following clear cutting (2) the export of organic matter with machines and (3) the practice of deep subsoiling by heavy machinery. These practices may affect directly or indirectly biodiversity and the delivery of soil functions (Missanjo and Kamanga-Thole 2014).To mitigate soil degradation after one or more plantation cycles, some agricultural practices are commonly used, such as the implementation of a cover crop in the inter-rows at planting (Gao et al. 2017; Liu et al. 2018). Another alternative to restore soil functions is to leave the logging residues (i.e. trunk, branches, leaves and roots of the logged plantation) on the plot, given the high amount of carbon and nutrients accumulated in the tree at the clear-cut stage (Perron et al. 2021). The positive impact of crop residues has been demonstrated on soil fauna resilience (Lassauce et al. 2012; Carron et al. 2015), soil organic carbon and nutrients (Alam et al. 2018). However, so far, this agroecological practice has never been tested in rubber plantations and the effect of the restitution of logging residues on soil functioning has never been addressed.We set up a field experiment after logging of the previous old RP in two industrial rubber plantations in Ivory Coast with contrasting soil types. In each RP, different type of logging residues and legume were added after clear cutting to determine their respective impact on the resilience of soil biodiversity. We hypothesized that (i) the input of logging residues and legumes after a clear-cutting will promote the resilience of soil biodiversity (microbial, nematode and macrofauna) (ii) soil types will affect the level of resistance and resilience of the soil biodiversity.In both sites, we observed a significant loss of soil biodiversity, 6 months after clear-cutting and land preparation. The negative impact of mechanical disturbance on the dynamics of soil biodiversity has been revealed by lower abundance, richness, beta diversity, ecological indexes and co-occurrence networks. For example, soil macrofauna density significantly dropped by 36.04 and 93.65% at sandy and clay site respectively. Macrofauna diversity decreased significantly by 60.6% at sandy site and 91.39% at clay site. Practices with logging residues contributed to higher resilience of macrofauna density (~ 360% in clay site and 300% in sandy site) and diversity (134–154% in clay site and 58-73% in sandy site) than practice without residues (75–97% in clay site and 35-38% in sandy site). The application of logging residues and legume was the most efficient practice to promote soil biodiversity and to mitigate the negative impact of clear-cutting in rubber monocultures after a 40 years’ rotation. Key words: Soil biodiversity, Rubber plantation, Restoration, Logging residues

Our planet is marked by significant climatic variations, particularly with the warming of temperatures and the variation in rainfall. In sub-Saharan Africa, the impacts of climate change are more pronounced because agriculture is highly dependent on climate, hence its vulnerability to climate variability (Vanluwe et al., 2011). In the context of changing environmental conditions, the use of innovative agricultural practices to contribute to plant adaptation is necessary to support food security challenges. Agroecological practices to improve crop yields and sustainable soil fertility management. Soil is the main reservoir of biodiversity as it hosts a very high diversity of interacting living species, which can be distinguished according to their size, macrofauna, mesofauna and microorganisms that constitute a particularly important component of soil (Brady and Weil, 2002), particularly for the provision of ecosystem services to humans. This work is therefore interested in studying the contribution of arbuscular mycorrhizal fungi (AMF) to the growth of millet (Pennisetum glaucum) under warmer temperature conditions and the behaviour of microbial community in soil of millet growing.Millet is grown in a plant climate chamber and inoculated with a selected mycorrhizal strain. These millet growing conditions were carried out in two different temperatures: 32°C (normal temperature) and 37°C (warmer temperature).The results showed that in conditions of warmer temperature the inoculation induced a significant vegetative growth of millet even with a low intensity of mycorrhization and so it improves microbial nutrient mineralization mediate vegetation growth.In soil of millet growing, a significant increase in microbial biomass with 42.7 in warmer temperature condition compared to control temperature 16.7. Results of DGGE shows also a soil abundance and SMB diversity of the total fungal community was noted under warmer temperature condition.This study showed that climate variation may affect soil symbiosis but not the potential for promoting plant growth of fungi. The use of arbuscular mycorrhizal fungi on the one hand as a biofertilizer can be an alternative in the context of reducing chemical inputs in agriculture and developing ecologically intensive agriculture (EIA) and on the other hand an adaptive practice to apprehend the predicted climate changes.