Krüger et al. 2013. Greenhouse gas emission peaks following natural rewetting of two wetlands in the southern Ukhahlamba-Drakensberg Park, South Africa

Krüger, J.P., Beckedahl, H., Gerold, G., Jungkunst, H.F., Greenhouse gas emission peaks following natural rewetting of two wetlands in the southern Ukhahlamba-Drakensberg Park, South Africa. South African Geographical Journal, DOI:10.1080/03736245.2013.847798

Abstract

The global importance of wetlands in the carbon and nitrogen cycles is well documented, but the specific greenhouse gas characteristics of South African wetlands are less well known. These wetlands most likely differ from more prominent wetlands from continuously humid climate zone (boreal, temperate and tropics). Particular wetlands in the southern Drakensberg are adapted to the seasonal drying during the winter months. Greenhouse gas emissions were measured during natural rewetting at two wetlands. A rapid reaction and significant positive correlation between greenhouse gas fluxes and ground water level were determined. Methane emissions were observed after two days of rewetting at one of the wetlands, and nitrous oxide emissions started within a day of rewetting at the other wetland. The high nitrous oxide emissions may be caused by the recent winter burning of vegetation, which most likely resulted in a greater availability of nitrogen in the soil. High nitrous oxide emissions following natural rewetting (the annual cyclical process in these wetlands) could contribute significantly to the local greenhouse gas budget. Hence, besides the methane emissions, the nitrous oxide emissions of wetlands in southern Africa should be taken into account.

Yohannes Y et al. 2013. Forest Management Influence on the Carbon Flux of Cupressus lusitanica Plantation in the Munessa Forest, Ethiopia

Yohannes Y, Shibistova O, Asaye Z, Guggenberger G (2013) Forest Management Influence on the Carbon Flux of Cupressus lusitanica Plantation in the Munessa Forest, Ethiopia. Forest Res 2:111. doi: 10.4172/2168-9776.1000111

Abstract

The effect of plantation forests on the global carbon balance is controversially discussed in recent times. As soil respiration is a decisive component in the carbon exchange between terrestrial ecosystems and atmosphere, effects of forest management measures (e.g. thinning) in the context of driving parameters of soil CO2 efflux is a key issue in optimizing carbon friendly land management. In the present study, we report the effects of thinning, soil temperature and soil moisture, and biotic parameters on soil CO2 efflux rate. Soil CO2 efflux was measured by using an Infrared Gas Analyzer. We selected thinned and un-thinned stands within six years old Cupressus lusitanica plantation forest. Soil respiration rate ranged from 1.47 to 6.92 μmol m-2s-1 (thinned) and 1.31 to 5.20 μmol m-2s-1 (control stand). Generally higher soil respiration rates were measured during wet than in dry season. Seasonal variability of soil CO2 efflux was significantly (p<0.05) correlated with soil moisture, but poorly correlated with soil temperature. Soil respiration increased with increasing soil moisture and reached maximum at 31% but after this threshold it start to decline. In general, soil CO2 efflux rate in the first and second year after thinning was 24% and 14% higher in the  thinned stand. Increased soil temperature at the thinned stand contributed minor to the larger soil CO2 efflux, the more important reason appeared to be the trees’ direct response. Higher fine root production together with larger microbial concentrations representing different groups infers a higher autotrophic respiration by roots and associated mycorrhizal fungi as well as by heterotrophic respiration. Despite the higher CO2 losses with soil respiration, the organic C and total N concentrations in soil rather tended to increase, indicating higher organic matter input to soil at the thinned stand.