Gerschlauer et al. 2014. Greenhouse gas exchange in tropical mountain ecosystems in Tanzania. EGU General Assembly 2014, held 27 April - 2 May, 2014 in Vienna, Austria
Tropical mountain ecosystems with their mostly immense biodiversity are
important regions for natural resources but also for agricultural
production. Their supportive ecosystem processes are particularly
vulnerable to the combined impacts of global warming and the conversion
of natural to human-modified landscapes. Data of impacts of climate and
land use change on soil-atmosphere interactions due to GHG (CO2, CH4,
and N2O) exchange from these ecosystems are still scarce, in particular
for Africa. Tropical forest soils are underestimated as sinks for
atmospheric CH4 with regard to worldwide GHG budgets (Werner et al.
2007, J GEOPHYS RES Vol. 112). Even though these soils are an important
source for the atmospheric N2O budget, N2O emissions from tropical
forest ecosystems are still poorly characterized (Castaldi et al. 2013,
Biogeosciences 10). To obtain an insight of GHG balances of selected
ecosystems soil-atmosphere exchange of N2O, CH4 and CO2 was investigated
along the southern slope of Mt. Kilimanjaro, Tanzania. We will present
results for tropical forests in three different altitudes (lower
montane, Ocotea, and Podocarpus forest), home garden (extensive
agro-forestry), and coffee plantation (intensive agro-forestry).
Therefore we used a combined approach consisting of a laboratory
parameterization experiment (3 temperature and 2 moisture levels) and in
situ static chamber measurements for GHG exchange. Field measurements
were conducted during different hygric seasons throughout two years.
Seasonal variation of temperature and especially of soil moisture across
the different ecosystems resulted in distinct differences in GHG
exchange. In addition environmental parameters like soil bulk density
and substrate availability varying in space strongly influenced the GHG
fluxes within sites. The results from parameterization experiments and
in situ measurements show that natural forest ecosystems and extensive
land use had higher uptakes of CH4. For the investigated forest
ecosystems we found considerable differences in soil sink strength for
CH4. N2O emissions were highest in natural forest ecosystems even though
N input in the intensively managed system was considerably higher.
Highest N2O efflux rates were identified in the region of highest mean
annual precipitation. CO2 emissions reduced from managed to natural
ecosystems. In general an increase in temperature as well as in soil
moisture caused higher GHG fluxes throughout all investigated natural
and managed ecosystems. With increasing altitude of the investigated
forests GHG emissions reduced overall.