title: Conversion of tropical lowland forest reduces nutrient return through litterfall, and alters nutrient use efficiency and seasonality of net primary production.
abstract: Tropical landscapes are not only rapidly transformed by ongoing land-use change, but are additionally confronted by increasing seasonal climate variation. There is an increasing demand for studies analyzing the effects and feedbacks on ecosystem functioning of large-scale conversions of tropical natural forest into intensively managed cash crop agriculture. We analyzed the seasonality of aboveground litterfall, fine root litter production, and aboveground woody biomass production (ANPP(woody)) in natural lowland forests, rubber agroforests under natural tree cover ("jungle rubber"), rubber and oil palm monocultures along a forest-to-agriculture transformation gradient in Sumatra. We hypothesized that the temporal fluctuation of litter production increases with increasing land-use intensity, while the associated nutrient fluxes and nutrient use efficiency (NUE) decrease. Indeed, the seasonal variation of aboveground litter production and ANPP(woody) increased from the natural forest to the plantations, while aboveground litterfall generally decreased. Nutrient return through aboveground litter was mostly highest in the natural forest; however, it was significantly lower only in rubber plantations. NUE of N, P and K was lowest in the oil palm plantations, with natural forest and the rubber systems showing comparably high values. Root litter production was generally lower than leaf litter production in all systems, while the root-to-leaf ratio of litter C flux increased along the land-use intensity gradient. Our results suggest that nutrient and C cycles are more directly affected by climate seasonality in species-poor agricultural systems than in species-rich forests, and therefore might be more susceptible to inter-annual climate fluctuation and climate change.
authors.affiliation: Department of Plant Ecology and Ecosystems Research, Albrecht von Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany. mkotows@gwdg.de.
authors.forename: Martyna M
authors.initials: MM
authors.lastname: Kotowska
authors.affiliation: Department of Plant Ecology and Ecosystems Research, Albrecht von Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Leuschner
authors.affiliation: Department of Biology, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University, Bogor, Indonesia.
authors.forename: Triadiati
authors.initials: T
authors.lastname: Triadiati
authors.affiliation: Department of Plant Ecology and Ecosystems Research, Albrecht von Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Hertel
mesh_terms: D000383:Agriculture; D018533:Biomass; D057486:Carbon Cycle; D057231:Climate Change; D018556:Crops, Agricultural / Q000254:growth & development / Q000378:metabolism; D065928:Forests; D009584:Nitrogen / Q000378:metabolism; D058458:Nitrogen Cycle; D010758:Phosphorus / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry*; D018517:Plant Roots; D011188:Potassium / Q000378:metabolism; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D014197:Trees; D014329:Tropical Climate; D014934:Wood
chemical_list: D012987:Soil; D010758:Phosphorus; D009584:Nitrogen; D011188:Potassium
keywords: Land-use change; Leaf litter; Nutrient cycling; Oil palm plantation; Root litter; Rubber plantation; Stem growth