Spatial variations in the stem CO2 efflux rate of Abies fabri and the response to temperature in the Gongga Mountains
As an important component of carbon budgets and net ecosystem CO2exchange in forest ecosystems,stem CO2 efflux rate (Es) plays a crucial role in the global carbon balance.Investigation of spatial variations and the response of Es to temperature,are essential for improving the accuracy of Es estimates at individual and community levels.In this study,the horizontally oriented soil chamber (HOSC) technique was applied to measure the CO2 released by stems.We measured Es in situ in the Abies fabri forest on Gongga Mountain using IRGA with a Li-6400-09 from September to December 2014.Our objectives were to examine the spatial variations in Es of A.fabri and to explore the response of Es to stem temperature (Tstem).Two representative trees in an immature A.fabri forest stand were selected.An opaque PVC collar (10.7cm inside diameter and 5cm high) was cut to match the approximate curvature of the stem with the other end being cut flat.Then the custom-built PVC collar was fastened to the south of the stem at a height of 0.3,1.3 and 2.3m and to the north at a height of 1.3m,with 100％ silicone sealant 24h before the measurement was made.Loose bark and moss were carefully removed from the stem surface curved by the PVC collar using a hairbrush without damaging the underlying cambium before installing the PVC collars.Measurements were made over three cycles at each sampling point,every 2h from 8:00 to 18:00 in the same day of every month.The A.fabri stem Es and Tstem showed an apparent spatial pattern.The Tstem at different heights ranked as follows:0.3＞ 1.3＞2.3m with maximum Es appearing at 1.3m.The Es and Tstem on the south face of the stem were higher than that on the north.The monthly averages Es of the growing season (September and October) and the non-growing season (November and December) was 0.51-0.99 and 0.14-0.22μmol m-2 s-1,respectively.The trend in A.fabri stem Es was consistent with Tstem with a significantly exponential relationship observed.The temperature coefficient (Q10) during the nongrowing season (4.6-6.8) was much higher than that in the growing season (1.9-3.0).It was concluded that spatial variations of Es and Q10 should be considered when estimating individual and community stem Es.
Abies fabristem CO2 efflux ratespatial variationstemperature sensitive coefficient (Q10)
国家科技期刊平台
NSTL
万方数据
维普
