Annual variation in soil respiration and its components in a coppice oak forest in Central Italy

Abstract

In order to investigate the annual variation of soil respiration and its components in relation to seasonal changes in soil temperature and soil moisture in a Mediterranean mixed oak forest ecosystem, we set up a series of experimental treatments in May 1999 where litter (no litter), roots (no roots, by trenching) or both were excluded from plots of 4 m2. Subsequently, we measured soil respiration, soil temperature and soil moisture in each plot over a year after the forest was coppiced. The treatments did not significantly affect soil temperature or soil moisture measured over 0–10 cm depth. Soil respiration varied markedly during the year with high rates in spring and autumn and low rates in summer, coinciding with summer drought, and in winter, with the lowest temperatures. Very high respiration rates, however, were observed during the summer immediately after rainfall events. The mean annual rate of soil respiration was 2.9 µmol m−2 s−1, ranging from 1.35 to 7.03 µmol m−2 s−1. Soil respiration was highly correlated with temperature during winter and during spring and autumn whenever volumetric soil water content was above 20%. Below this threshold value, there was no correlation between soil respiration and soil temperature, but soil moisture was a good predictor of soil respiration. A simple empirical model that predicted soil respiration during the year, using both soil temperature and soil moisture accounted for more than 91% of the observed annual variation in soil respiration. All the components of soil respiration followed a similar seasonal trend and were affected by summer drought. The Q10 value for soil respiration was 2.32, which is in agreement with other studies in forest ecosystems. However, we found a Q10 value for root respiration of 2.20, which is lower than recent values reported for forest sites. The fact that the seasonal variation in root growth with temperature in Mediterranean ecosystems differs from that in temperate regions may explain this difference. In temperate regions, increases in size of root populations during the growing season, coinciding with high temperatures, may yield higher apparent Q10 values than in Mediterranean regions where root growth is suppressed by summer drought. The decomposition of organic matter and belowground litter were the major components of soil respiration, accounting for almost 55% of the total soil respiration flux. This proportion is higher than has been reported for mature boreal and temperate forest and is probably the result of a short‐term C loss following recent logging at the site. The relationship proposed for soil respiration with soil temperature and soil moisture is useful for understanding and predicting potential changes in Mediterranean forest ecosystems in response to forest management and climate change.

Partitioning sources of soil‐respired CO2 and their seasonal variation using a unique radiocarbon tracer

“…In contrast to other studies (Epron et al, 2001;Hö gberg et al, 2001;Rey et al, 2002), we did not observe marked temporal variation in root respiration fluxes with the exception of the increase in September 2003 (Fig. 4).…”

“…(Edwards & Harris, 1977). Rey et al (2002) reported an annual contribution from root respiration of 23% although previous disturbance at the site were thought to be the cause of this low estimate. It is important to note that in our study, times of highest relative contributions (FRR) were not necessarily times of high root respiration fluxes and thus both quantities should be reported.…”

“…Another trenching experiment at a smaller scale in a Mediterranean forest (Quercus spp. ), indicated an annual contribution of 23%, but other factors such as enhanced decomposition in trenched plots and recent logging of the site could have affected the results (Rey et al, 2002). The reporting of root respiration as a percentage of total respiration rather than an absolute quantity may be masking differences in root inventory, allocation, and total soil respiration among sites.…”

A study of soil-dynamics based on a simulated drought in an alpine meadow on the Tibetan Plateau

“…This suggests that extreme drought will alter not only the microbial biomass, but also the community composition for the alternation of microbial C: N. The enhanced ratio of MBC and MBN as showed dominated the fungal with growth deriving more nitrogen nutrient. Various studies have suggested that soil respiration is related to the soil moisture content and soil temperature, and soil respiration will show different sensitivities to soil temperature (Kirschbaum 1995;Rey et al 2002). In our study, the decreased water content weakened the soil respiration significantly.…”

A new approach to trenching experiments for measuring root–rhizosphere respiration in a lowland tropical forest

“…Root respiration is strongly influenced by aboveground assimilation and growth (Horwath et al, 1994;Robinson and Scrimgeour, 1995). The heterotrophic component of soil respiration is strongly influenced by substrate availability (Raich and Tufekcioglu, 2000;Vasconcelos et al, 2004), which is closely related to aboveground litterfall on a global scale (Raich and Nadelhoffer, 1989;Davidson et al, 2002), and is thus also ultimately driven by aboveground growth and production (Rey et al, 2002). Recently, a microcosm study showed that increased litter inputs under elevated CO 2 would greatly increase microbial respiration in the soil (Liu et al, 2008) and FACE experiments have shown large increases in root respiration, which may be related to increased root biomass or higher specific root respiration rates (Andrews et al, 1999;King et al, 2001;Pregitzer et al, 2008).…”