![]() ![]() By grazing on bacteria, protists release nutrients fixed in bacterial biomass, thereby increasing mineralization of carbon and nitrogen. Bacteria are grazed by other organisms, most importantly soil protists and nematodes. Fungi and bacteria are thus particularly influential and constitute the base of soil food webs. A particularly wide spectrum of these biochemical transformations are carried out by saprotrophic soil microorganisms. These interactions drive the major functions of terrestrial ecosystems, such as nutrient mineralization and plant productivity. The belowground decomposer food web systems are composed of microorganisms, micro-, meso- and macrofauna, interacting with each other and the environment in a complex network. This applies, in particular, to the functioning of the highly diverse belowground system. However, despite the large-scale conversion of rainforests worldwide, little is known about the biodiversity and ecological functioning of the land uses replacing lowland rainforest. ![]() On Sumatra, for example, 12 million ha of forest have been converted over the past 30 years, predominantly into oil palm and rubber plantations. Nevertheless, tropical forest conversion is increasing rapidly, particularly in South East Asia. Tropical forests have very high biodiversity so there is particular and increasing concern about their conversion into agricultural and plantation systems. The biodiversity of natural ecosystems is indispensable for providing ecosystem functions, but is threatened by anthropogenic activities such as the conversion of forests into agricultural production systems. Overall, the lower species richness, density and biomass in plantations than in rainforest, and the changes in the functional composition of the testate amoebae community, indicate detrimental effects of rainforest conversion on the structure and functioning of microbial food webs. This difference suggests that rainforest conversion changes biogenic silicon pools and increases silicon losses. ![]() In addition, the relative density of species with siliceous shells was >50% lower in the litter layer of oil palm and rubber compared to rainforest and jungle rubber. This was particularly so in oil palm plantations. In contrast, plantations had a low density of high trophic level species indicating losses of functions. Similar abundances of species of high and low trophic level in rainforest suggest that trophic interactions are more balanced, with a high number of functionally redundant species, than in rubber and oil palm. Living testate amoebae species richness, density and biomass were all lower in replacement land uses than in rainforest, with the impact being more pronounced in litter than in soil. We investigated the effects of conversion of rainforest into jungle rubber, intensive rubber and oil palm plantations on testate amoebae, diverse and functionally important protists in litter and soil. Large areas of tropical rainforest are being converted to agricultural and plantation land uses, but little is known of biodiversity and ecological functioning under these replacement land uses. ![]()
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