Impact of tropical lowland rainforest conversion into rubber and oil palm plantations on soil microbial communities

Abstract

Focusing on Sumatra, a hotspot of tropical lowland rainforest transformation, we investigated effects of the conversion of rainforests into rubber agroforests (Bjungle rubber^), intensive rubber, and oil palm plantations on the communities of litter and soil microorganisms and identified factors responsible for these changes. Litter basal respiration, microbial biomass, total bacterial phospholipid fatty acids (PLFAs), and fungal PLFAs did not vary significantly with rainforest conversion. In litter of converted ecosystems, the concentration of certain PLFAs including the Gram-negative bacteria marker PLFA cy17:0 and the Gram-positive bacteria marker PLFA i17:0 was reduced as compared to rainforest, whereas the concentration of the arbuscular mycorrhizal fungi (AMF) marker neutral lipid fatty acid (NLFA) 16:1ω5c increased. As indicated by redundancy analysis, litter pH and carbon concentration explained most of the variation in litter microbial community composition. In soil, microbial biomass did not vary significantly with rainforest conversion, whereas basal respiration declined. Total PLFAs and especially that of Gram-negative bacteria decreased, whereas PLFA i17:0 increased with rainforest conversion. The concentration of fungal PLFAs increased with rainforest conversion, whereas NLFA 16:1ω5c did not change significantly. Redundancy analysis indicated that soil pH explained most of the variation in soil microbial community composition. Overall, the data suggest that conversion of rainforests into production systems results in more pronounced changes in microbial community composition in soil as compared to litter. In particular, the response of fungi and bacteria was more pronounced in soil, while the response of AMF was more pronounced in litter. Notably, only certain bacterial markers but not those of saprotrophic fungi and AMF were detrimentally affected by rainforest conversion.

Conversion of rainforest to oil palm and rubber plantations alters energy channels in soil food webs

“…In line with the study of Krashevska et al (2015), we found the abundance of nonspecific bacterial biomarker FAs to be highest in oil palm plantations while the abundance of specific bacterial biomarker FAs decreased. Based on metagenomics, Schneider et al (2015) also found certain bacteria taxa to be more abundant in oil palm plantations as compared to rainforest.…”

“…Investigating the same study sites, Krashevska et al (2015) found the AMF biomarker NLFA in litter to be lowest in rainforest litter and not to differ significantly between land-use systems in soil, whereas we found the proportion of AMF biomarker NLFAs in soil fauna to be highest in rainforest. Investigating the same study sites, Krashevska et al (2015) found the AMF biomarker NLFA in litter to be lowest in rainforest litter and not to differ significantly between land-use systems in soil, whereas we found the proportion of AMF biomarker NLFAs in soil fauna to be highest in rainforest.…”

“…Further, based on results of previous studies (Klarner et al, 2017;Krashevska et al, 2015), which indicated reduced feeding on bacteria and increased feeding on plants with conversion of rainforest into oil palm plantations, we hypothesized (b) that rainforest conversion strengthens the plant-based energy channel and reduces the bacterial energy channel in soil food webs of plantation systems. We hypothesized that (a) different groups of meso-and macrofauna are linked to different basal resources with mesofauna detritivores, that is, Collembola and Oribatida, being closely associated with the fungal energy channel, and macrofauna detritivores such as Lumbricina and Diplopoda being more closely associated with the bacterial and plant energy channel.…”

“…Rainforest conversion strongly affects environmental processes, including soil organic carbon pools and soil erosion (Guillaume, Damris, & Kuzyakov, 2015), primary production of trees (Kotowska, Leuschner, Triadiati, Meriem, & Hertel, 2015), carbon dioxide and methane fluxes (Hassler et al, 2015), as well as nitrogen cycling and soil fertility (Allen, Corre, Tjoa, & Veldkamp, 2015). It has been shown that rainforest conversion strongly affects biomass, vitality, and mycorrhizal colonization of roots (Sahner et al, 2015), biodiversity and abundance of microorganisms (Krashevska, Klarner, Widyastuti, Maraun, & Scheu, 2015;Schneider et al, 2015) and trophic-guild composition of litter-dwelling fauna (Barnes et al, 2014;Klarner et al, 2017). It has been shown that rainforest conversion strongly affects biomass, vitality, and mycorrhizal colonization of roots (Sahner et al, 2015), biodiversity and abundance of microorganisms (Krashevska, Klarner, Widyastuti, Maraun, & Scheu, 2015;Schneider et al, 2015) and trophic-guild composition of litter-dwelling fauna (Barnes et al, 2014;Klarner et al, 2017).…”

Minimum forest cover required for sustainable water flow regulation of a watershed: a case study in Jambi Province, Indonesia

“…Although oil palm is of economic value to farmers and the local regions in which it is grown, it has received environmental and social criticism, often being held responsible for deforestation (Wicke et al, 2011;Vijay et al, 2016;Gatto et al, 2017), biodiversity loss (Fitzherbert et al, 2008;Koh and Wilcove, 2008;Wilcove and Koh, 2010;Carlson et al, 2012;Krashevska et al, 2015), decreased soil carbon stocks (Guillaume et al, 2015Pransiska et al, 2016), and increased greenhouse gas emissions (Allen et al, 2015;Hassler et al, 2017). Similarly, rubber plantations have environmental impacts such as reducing the soil infiltration capacity, accelerating soil erosion, increasing stream sediment loads (Ziegler et al, 2009;Tarigan et al, 2016b), and decreasing soil carbon stocks (Ziegler et al, 2011).…”