| Soil respiration(Rs) in forest ecosystems is an important ecological process in carbon cycling. It is also a hot research issue in regional carbon budget and global change, which is closely related with international negotiations on climate change mitigation, and the execution of international carbon trade. Therefore, accurate investigation of soil respiration and the regulating factors is current hot issue in the study of global change. In this study, we selected three natural secondary pinus yunnanensis(e.g.young(15 years), mid-aged(30 years), mature forest(45 years)), and one mid-aged artificial forest(20 years) in the Mopan Mountain National Forest Park in Yunnan Province. LI-6400-09 soil respiration chamber connected to a portable infrared gas analyzer was employed to measure variations of Rs rates Soil physical and chemical characters(e.gsoil temperature, soil moisture, p H, C, N and P) were investigated by conventional methods. The study aims to understand the dynamic characteristics of Rs and its main influence factors. The results can provide data support in assessing the potential for carbon sequestration and soil carbon cycling in pinus yunnanensis forests. The results showed:(1)There were significant variations for the Rs rates in natural and artificial forests of pinus yunnanensis.Rs showed a similar pattern with a single peak occurred in the wet season and a depression in the dry season. The Rs ranged from 0.88~3.08 μmol CO2m-2s-1 in natural young forest, 1.58~4.23μmol CO2·m-2·s-1 in natural mid-aged forest and 1.09 ~ 3.69μmol CO2·m-2·s-1 in natural mature forest, respectively. Rs rates in different natural forest stand age were middle-aged forest> mature forest >young forest. Moreover, Rs in the artificial forest(1.13 to 3.34 μmolm-2·s-1) was significantly lower than that in the natural forest(1.58 to 4.23 μmolm-2·s-1) due to the differences in community characteristics of ground vegetation and soil nutrient content, etc.(2)Soil temperature and soil moisture were the most influential environmental factors controlling Rs. Significant relationships were found between Rs and soil moisture at 0-5cm and 5-10 cm depth in natural and artificial forests, which could be responsible for seasonal variation of Rs about 32.3%-81.5% in the four sites. The contribution of soil temperature to Rs was significantly lower than that of soil moisture. Although significant relationships were found between Rs and soil temperature in each site, except for the mid-age forest, soil temperature could only explain 29.5%~57.6% of variation in Rs. The equation of interactions had much more predicative power than that using temperature and water as single independent variables, soil temperature and soil moisture together could explain 80.8%-93.0% Rs in Pinus yunnanensis.(3)There were significant difference in the effects of soil physical and chemical indicators on seasonal dynamics of Rs. The correlation analysis showed that Rs was no significant correlated with soil organic matter, and significantly correlated with total N was only found in mid-age forest(R2=0.712,P<0.05).However, Rs was significantly correlated with soil hydrolysable N in the mid-age forest, mature forest and artificial forest(P<0.05), and the correlation coefficients were 0.763,0.695,0.743, respectively. The significant impact of C/N on Rs was negative(p<0.01),and the correlation coefficients were-0.812~-0.929.The effect of total P on Rs was positive(p<0.05)and the correlation coefficients were 0.848~0.897.The p H were positively correlated with Rs(P<0.05) with the correlation coefficient of0.612~0.733 in each site, except for the mid-age forest(p>0.05). |
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