3 research outputs found
Impact of litter removal and seasonality on soil greenhouse gas fluxes and nutrient cycling in an Austrian beech forest
Die VerĂ€nderung des globalen Klimas kann bewirken, dass Waldökosysteme und deren Boden-TreibhausgasflĂŒsse verĂ€ndert werden. Ebenso können sich NĂ€hrstoffkreislĂ€ufe verschieben, was den Austausch von NĂ€hrstoffen zwischen Waldboden, Streuschicht, AtmosphĂ€re und der Pflanzengesellschaft verĂ€ndert. Ziel dieser Arbeit war es, den Einfluss der Laubstreu auf die Treibhausgase sowie NĂ€hrstoffkreislĂ€ufe aufzuzeigen. Die vorliegende Masterarbeit wurde im BOKU Lehrforst Rosalia in Niederösterreich auf einem reinen Buchenbestand durchgefĂŒhrt. Von Juni bis November 2012 wurden wöchentlich Treibhausgasmessungen (CO2, CH4 und N2O) mit statischen Gasmesskammern durchgefĂŒhrt. DafĂŒr wurden insgesamt 12 Kammerpaare installiert. Ein Paar setzt sich aus einer KontrollflĂ€che und einer FlĂ€che ohne Laub zusammen. Bei der FlĂ€che ohne Laub wurde eine schwarze Gartenfolie als Laubsubstitut aufgelegt. Die NĂ€hrstoffzufuhr vom Laub in den Mineralboden sollte somit verhindert werden. Auch sollte die Bodentemperatur sowie die -feuchte mit der Folie unverĂ€ndert bleiben. ZusĂ€tzlich wurden monatlich Bodenproben entnommen, die auf ihren pH-Wert, Gesamt- Kohlenstoff (C) und Stickstoff (N), NO3-, NH4+, PO43-, DOC/TN und mikrobielle Parameter wie die Glukose-VerfĂŒgbarkeit, den mikrobiellen C und N und die mikrobielle Atmung untersucht wurden. Zu Beginn und zu Ende der Messperiode wurden zudem Bodenprofile genommen, um die vertikale Kohlenstoff- und Stickstoffverteilung zu bestimmen. Bei der FlĂ€che ohne Laub kam es zu einer Reduktion der CO2-Emissionen um rund 35%. Höhere Bodentemperaturen im Sommer hatten einen positiven Effekt auf die CO2-Emissionen auf beiden FlĂ€chen. Der Q10-Faktor wies jedoch im Sommer eine höhere TemperatursensibilitĂ€t der CO2-Emissionen auf der FlĂ€che ohne Laub auf. Die FlĂ€che ohne Laub nahm mehr CH4 aus der AtmosphĂ€re auf. AuĂerdem zeigten die FlĂ€chen ohne Laub kaum signifikanten EinflĂŒsse auf die NĂ€hrstoffkreislĂ€ufe nach Entfernung der Streuschicht.Climate change is expected to cause the alteration of forest ecosystems, which may result in shifts in soil GHG fluxes. In addition soil nutrient cycling may be affected as well as the exchange of nutrients between soil, forest floor, atmosphere and the tree community. The presented study aims to demonstrate the influence of the litter layer on soil-greenhouse gas emissions and nutrient cycling. This Masters thesis was conducted in a pure beech transect in the BOKU Forest Demonstration Center Rosalia, Lower Austria. Soil CO2, CH4 and N2O emissions were determined through weekly manual gas sampling from static headspace chambers from July to November 2012. Twelve pairs of gas measurement chambers were installed. Each pair consisted of two treatments: a control treatment and a no-litter treatment where the litter layer had been removed and replaced by a black garden foil, thereby stopping nutrient input from the litter into the soil, without changing soil moisture and temperature. In addition, monthly soil samples were taken adjacent to the chambers and analyzed to determine pH, total C, total N, NO3-, NH4+, PO43-, DOC/TN ,and microbial parameters such as microbial biomass C and N, glucose and respiration. Further, in the beginning and at the end of the measuring period, soil profile samples were collected to determine the distribution of C and N in the soil profile. The removal of the litter layer strongly reduced soil CO2 emissions on the no-litter treatment (by 35% on average). Other climatic factors such as increased soil temperature had a positive effect on CO2 emissions. The temperature sensitivity factor Q10 showed a higher sensitivity in the no-litter treatment, especially during summertime. The litter removal caused an increased CH4 uptake. Soil nutrient cycling was less disturbed by the litter removal than assumed. No significant differences in nutrient concentrations were found between the two treatments.eingereicht von Lukas KranzingerZsfassung in dt. SpracheWien, Univ. fĂŒr Bodenkultur, Masterarb., 2014(VLID)108273
Contribution of litter layer to soil greenhouse gas emissions in a temperate beech forest
Background and aims
The litter layer is a major source of CO2, and it also influences soil-atmosphere exchange of N2O and CH4. So far, it is not clear how much of soil greenhouse gas (GHG) emission derives from the litter layer itself or is litter-induced. The present study investigates how the litter layer controls soil GHG fluxes and microbial decomposer communities in a temperate beech forest.
Methods
We removed the litter layer in an Austrian beech forest and studied responses of soil CO2, CH4 and N2O fluxes and the microbial community via phospholipid fatty acids (PLFA). Soil GHG fluxes were determined with static chambers on 22 occasions from July 2012 to February 2013, and soil samples collected at 8 sampling events.
Results
Litter removal reduced CO2 emissions by 30 % and increased temperature sensitivity (Q10) of CO2 fluxes. Diffusion of CH4 into soil was facilitated by litter removal and CH4 uptake increased by 16 %. This effect was strongest in autumn and winter when soil moisture was high. Soils without litter turned from net N2O sources to slight N2O sinks because N2O emissions peaked after rain events in summer and autumn, which was not the case in litter-removal plots. Microbial composition was only transiently affected by litter removal but strongly influenced by seasonality.
Conclusions
Litter layers must be considered in calculating forest GHG budgets, and their influence on temperature sensitivity of soil GHG fluxes taken into account for future climate scenarios.(VLID)134431