1 research outputs found
Comparison of methane, nitrous oxide fluxes and CO2 respiration rates from a Mediterranean cork oak ecosystem and improved pasture
Background and aims: During the recent decades, cork
oak (Q. suber) mortality has been increasing in Mediterranean
oak woodland endangering the economical and environmental
sustainability of the “montado” ecosystem.
This fact in combination with climate change and conversion
of forestland to pasture may significantly affect the
soil-atmosphere greenhouse gases (GHGs) exchange. Our
study evaluates the impact of oak trees as compared to
pasture on net ecosystem GHG (CH4, N2O, and CO2)
exchange as well as the main environmental factors
influencing this exchange.
Methods: We used field chamber measurements for the
collection of GHGs under three different conditions: 1)
open area (OA), 2) under tree canopy area (UC) and 3)
improved pasture (IP). Experiments were done under typical
Mediterranean climate at central Portugal in 2010 and
2011.
Results: The UC had higher nitrification potential, soil
C/N ratio, electrical conductivity, litter input and soil organic
matter (SOM) than OA and IP. SOM positively
correlated with soil CH4 and N2O fluxes but not with soil
CO2 respiration rates. Soil water content (SWC) drives
both CH4 and N2O fluxes. Under certain conditions, when
SWC reached a threshold (7 % for CH4 and 3 % for N2O)
the result was net uptake and that net uptake increased with
SWC. This was the case for the UC and OA. Conversely,
for the IP soil water content above 4 % promoted net CH4
release.
Conclusions: Our results show that cork oak influences
soil properties and consequently GHGs fluxes. In the UC
the input of litter for SOM together with soil moisture,
favoured microbiological activity and related GHGs
fluxes. Soil temperature is a secondary factor in the studied
conditions. Our results also emphasized the potential impact
posed by decreased cork oak tree density in the
functioning of the “montado” ecosystem.
Keywords Evergreen oak . Greenhouse gases