Sri Rahayu Utami

Macroecology of methane-oxidizing bacteria: the β-diversity of pmoA genotypes in tropical and subtropical rice paddies

Studies addressing microbial biogeography haveincreased during the past decade, but research onmicrobial distribution patterns is still in its infancies,and many aspects are only poorly understood. Here,we compared the methanotroph community in paddysoils sampled in Indonesia, Vietnam, China and Italy,focusing on the distance–decay relationship.We usedthe pmoA gene as marker for methanotroph diversityin terminal restriction fragment length polymorphism,microarray and pyrosequencing approaches. Wecould observe a significant increase of β-diversity with geographical distance across continents (12 000 km).Measured environmental parameters explained only asmall amount of data variation, and we found no evidencefor dispersal limitation. Thus, we propose historicalcontingencies being responsible for theobserved patterns. Furthermore, we performed anin-depth analysis of type II methanotroph pmoA distributionat the sequence level. We used ordinationanalysis to project sequence dissimilarities into athree-dimensional space (multidimensional scaling).The ordination suggests that type II methanotrophs inpaddy fields can be divided into five major groups.However, these groups were found to be distributed inall soils independent of the geographic origin. Byincluding tropical field sites (Indonesia and Vietnam)into the analysis, we further observed the firstpaddy fields harbouring a methanotroph communitydepleted in type II methanotrophs.

Partial Nutrient Budget from Lowland Forests Converted to Oil Palm and Rubber Plantations in Sumatra, Indonesia

Forest conversion to agricultural land may affect nutrient budget due to different soil management intensity. Our study aimed to assess partial nutrient budget from forest converted to rubber and oil palm plantations in Jambi Province, Sumatra, Indonesia. The research investigated four land uses: lowland forest and jungle rubber (as reference) and the converted land uses of rubber and oil palm plantations in loam and clay Acrisol soil landscapes, with four replicates in each site, except in oil palm plantation with three replicates. Partial nutrient budgets were quantified from nutrient input (bulk precipitation and fertilizers) and output (leaching and harvest) for N, P, K, Ca, Mg and Na. Annual leaching fluxes were the main output pathways for N, P and base cations in the reference land uses, except for P in jungle rubber sites where the major output pathway was harvest export. The high nutrient output through leaching losses and harvest export resulted in the lowest annual partial budgets of Ca and Mg in oil palm plantations than in the other land uses in both landscapes. Proper soil management is needed to minimize the net negatives balances and their effect on sustainability of oil palm plantations.