A7 Changes in soil internal N cycle and trace gas fluxes under elevated nutrient input

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PI(s) for this project:

Prof. Dr. Edzo Veldkamp
Prof. Dr. Heinz Flessa

Project abstract: Changes in soil internal N cycle and trace gas fluxes under elevated nutrient input

Project description: Although projections are that N deposition will increase strongly in the tropics, its effects on tropical forests are still largely descriptive. In the proposed project we plan to continue on-going measurements of soil-atmosphere fluxes of N2O, NO, CH4 and CO2 (NUMEX experiment). Our early results suggest that after the first year of flux measurements there are already substantial changes in the microbial processes nitrification and denitrification. Furthermore there are indications that N cycling rates have increased in plots that receive N addition at moderate rates. We plan to conduct measurements using 15N pool dilution and a 15N pulse chase experiment to assess quantitatively how microbial N cycling has changed in forest soils and to translate the short-term N fluxes to long-term fates of NH4 + and NO3 - in forest soils exposed to chronic N addition. Another focus will be potential feedbacks of N deposition on the soil carbon cycling by measuring heterotrophic CO2 respiration. During the first phase, our group discovered in cooperation with A5 that tank bromeliads are a substantial source of Methane. We plan a series of measurement to determine the size of these CH4 emissions from different elevations.

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Keywords

aboveground biomass Agroforestry air temperature altitudinal gradient AM fungi Andes Biodiversity biodiversity Biodiversity conservation boosted regression trees C source limitation calcium carbon stocks climate climate change clouds conservation payments database design DOC DOI ECSF Ecuador environmental gradients fire history foliar N forest forest and open land forest line generalized linear models grassland Holocene hydrochemistry hydrological processes information management system insect herbivores isotopes Lagunas Natosas land-use change landslide Late Glacial leaf dark respiration light-saturated net photosynthesis mean transit time mean–variance metadatabase microcatchment 2 mineral N model comparison Modern Oldfield trap Modern pollen rain mountain forest native species Newsletter nitrate nitrogen nutrient limitation nutrient manipulation Palaeoecology palynology Pampa parameters estimation Paramo pH phosphorus phosphorus availability Pilodyn wood tester Piperaceae Pleistocene Poaceae pollen pollen analysis pollen grain morphology Páramo Q2 rainwater chemistry realistic forcing reforestation regionalization research group Setaria sphacelata simulation model soil N availability soil nutrients soil organic matter South America South Ecuador species richness estimate statistical modeling stochastic dominance sulphur temporal trends thermal structure tracer tree growth tree seeds tropical lowland forests tropical montane forest tropical soils weighted model ensembles wood production