Intensive tropical land use massively shifts soil fungal communities.

Soil fungi are key players in nutrient cycles as decomposers, mutualists and pathogens, but the impact of tropical rain forest transformation into rubber or oil palm plantations on fungal community structures and their ecological functions are unknown. We hypothesized that increasing land use intensity and habitat loss due to the replacement of the hyperdiverse forest flora by nonendemic cash crops drives a drastic loss of diversity of soil fungal taxa and impairs the ecological soil functions. Unexpectedly, rain forest conversion was not associated with strong diversity loss but with massive shifts in soil fungal community composition. Fungal communities clustered according to land use system and loss of plant species. Network analysis revealed characteristic fungal genera significantly associated with different land use systems. Shifts in soil fungal community structure were particularly distinct among different trophic groups, with substantial decreases in symbiotrophic fungi and increases in saprotrophic and pathotrophic fungi in oil palm and rubber plantations in comparison with rain forests. In conclusion, conversion of rain forests and current land use systems restructure soil fungal communities towards enhanced pathogen pressure and, thus, threaten ecosystem health functions.

Degradation of Root Community Traits as Indicator for Transformation of Tropical Lowland Rain Forests into Oil Palm and Rubber Plantations.

Conversion of tropical forests into intensely managed plantations is a threat to ecosystem functions. On Sumatra, Indonesia, oil palm (Elaeis guineensis) plantations are rapidly expanding, displacing rain forests and extensively used rubber (Hevea brasiliensis) agro-forests. Here, we tested the influence of land use systems on root traits including chemical traits (carbon, nitrogen, mineral nutrients, potentially toxic elements [aluminium, iron] and performance traits (root mass, vitality, mycorrhizal colonization). Traits were measured as root community-weighed traits (RCWTs) in lowland rain forests, in rubber agro-forests mixed with rain forest trees, in rubber and oil palm plantations in two landscapes (Bukit Duabelas and Harapan, Sumatra). We hypothesized that RCWTs vary with land use system indicating increasing transformation intensity and loss of ecosystem functions. The main factors found to be related to increasing transformation intensity were declining root vitality and root sulfur, nitrogen, carbon, manganese concentrations and increasing root aluminium and iron concentrations as well as increasing spore densities of arbuscular mycorrhizas. Mycorrhizal abundance was high for arbuscular and low for ectomycorrhizas and unrelated to changes in RCWTs. The decline in RCWTs showed significant correlations with soil nitrogen, soil pH and litter carbon. Thus, our study uncovered a relationship between deteriorating root community traits and loss of ecosystem functionality and showed that increasing transformation intensity resulted in decreasing root nutrition and health. Based on these results we suggest that land management that improves root vitality may enhance the ecological functions of intense tropical production systems.

Diversity of Arbuscular Mycorrhizal Fungi in the Growth Habitat of Kayu Kuku (Pericopsis mooniana Thw.) In Southeast Sulawesi.

Arbuscular Mycorrhizal Fungi (AMF) are categorized as fungi which have symbioses with terrestrial plants and are distributed in various habitat types. The objectives of this research were to investigate the diversity of AMF in stands of kayu kuku (Pericopsis mooniana Thw.) in Southeast Sulawesi. Collection of samples of soil and root were conducted in six locations. Isolation of spores used the method of wet sieving and decanting, whereas AMF identification was conducted by observing morphology of AMF spores. Parameters of AMF diversity, namely species richness, diversity index, dominance index, evenness index and colonization were studied using method of infected root length. Research results showed that location differences affected significantly the spore density and parameters of AMF diversity, except colonization of AMF (p < 0.116). Location around the Governor office showed the highest number of spores (208.6 spores/100 g of soil). Soil chemical properties, such as C, N, P and heavy metal contributed towards AMF spore density and diversity. Soil C and N correlated negatively with spore density. In terms of location, Glomeraceae constituted the genera with the largest number of species and possessed wide distribution in all research locations. In general, natural forest has higher AMF diversity index (Shannon-Weiner diversity index-H'), evenness (E) and species richness (S) as compared with location of PT. Vale Indonesia Tbk.