1. Respiration of downed logs in pine and oak forests in the Qinling Mountains, China.
- Author
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Yuan, Jie, Cheng, Fei, Zhu, Xian, Li, Jingxia, and Zhang, Shuoxin
- Subjects
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OAK , *FORESTS & forestry , *PINE , *GAS analysis - Abstract
Abstract Approximately 70% of the carbon (C) stored in logs is released into the atmosphere, representing an important source of CO 2 lost from terrestrial ecosystems. Log respiration (R log) has gained attention as a core issue in global C cycle research. In forest ecosystems that contain many logs, the R log flux can convert forests from C sinks into C sources; thus, R log should be considered in relevant research to avoid underestimating the CO 2 losses in the forest C cycle. Limited information is available regarding R log from natural forests, and many uncertainties remain about the magnitude of R log. In our study, R log was measured in situ by infrared gas analysis in Pinus armandi and Quercus aliena var. acuteserrata forests in the Qinling Mountains, China. The objectives of this study were (1) to reveal the seasonal variation patterns of R log ; (2) to systematically analyze the relationships between R log and various factors, including the tree species, decay class, temperature, water content, and chemical composition; and (3) to estimate the annual R log flux in P. armandi and Q. aliena var. acuteserrata forests in the Qinling Mountains, China. This study presents a full year time series of R log measurements for 30 logs (3 replicate logs × 5 decay classes × 2 tree species). The R log measurements were repeated 468 times for each log from May 2014 to April 2015. The log temperature (T log), air temperature (T A), soil temperature (T S) at a depth of 10 cm, and log water content (W log) were measured simultaneously with R log. Moreover, the log density (D log) and chemical composition (C, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)) were determined. Our results showed significant seasonal variation in R log for both species, which corresponded to variations in T log during the study period. The annual mean R log of Q. aliena var. acuteserrata (1.69 ± 1.60 μmol m−2·s-1) was higher than that of P. armandi (1.55 ± 1.43 μmol m−2·s−1), but the difference was not significant (P = 0.61). The decay classes, T log , W log , and the N, P, Ca, and Mg concentrations were positively correlated with R log. Moreover, the K concentration was negatively correlated with R log , and the C concentration in logs was not correlated with R log. The total annual R log flux did not differ significantly between the P. armandi (67.25 ± 7.28 g C·m−2·y−1) and Q. aliena var. acuteserrata (74.69 ± 9.31 g C·m−2·y−1) forests (P = 0.26). These results provide insight into the factors responsible for seasonal changes in R log and can improve estimates of the annual R log flux in natural forests. Highlights • Respiration from logs (R log) was affected by the chemical composition of the logs. • R log increased as the N, P, Ca and Mg concentrations increased. • R log declined as the K concentration increased. • R log was affected by the log decay class, temperature and moisture level. • There were significant seasonal variations in log respiration and temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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