Partitioning of soil respiration in a beech forest using a trenching experiment.

Total soil respiration (RTOT) has two components; heterotrophic (RH) and autotrophic (RA) respiration. We aim to partition the components of RTOT in a beech (Fagus sylvatica L.) forest using a trenching experiment. The study plots were set up in December 2009. Four plots were surrounded by trenches and four other plots were left untrenched. Measurements of CO2 were measured using a closed system chamber attached to a portable infrared gas analyser. Soil temperature and soil moisture content at 5 cm depth were also measured at each plot. Total soil respiration was measured in untrenched plots and RH in plots that were trenched. Soil respiration showed a clear seasonal trend with high levels recorded during the summer and low levels in winter and early spring. Total soil respiration and RH were related individually to soil temperature using exponential relationships and the relationship with soil moisture content was described using a peak relationship, these were found to be key factors affecting soil respiration. The Q10 value for total soil respiration was calculated to be 1.7 and Q10 value of 1.5 was calculated for heterotrophic respiration. A sudden increase in soil moisture after a dry period led to high CO2 levels. There was significant difference found between soil respiration rates in the untrenched and trenched plots (p < 0.05), however the contribution of RA and RH to RTOT varied at certain times of the year, it was found that during a period that included the summer months RH and RA represented 89 % and 11 % of RTOT, respectively and in the period between these days the contribution of RH and RA to RTOT was 64 % and 36 % respectively. Trenching can give accurate estimates of the two main components of soil respiration, if direct effects of the methods are accounted for.