| Soil respiration is an integrated result of the belowground processes, including soil organic matter, plant roots, soil microbes, and detritus, it has been widely used to evaluate the effects of disturbance on soil carbon pools. Hence, it is necessary to measure soil respiration in order to determine the effects of forest management activities on forest ecosystem functions.Chinese fir (Cunninghamia lanceolata) is one of the most important plantation tree species in China in terms of planting area, yield and timber usage. In recent decades, a great deal of pure Chinese fir stands were established in the southern part of China for an anticipated high economic refund. The system of successive plantation of Chinese fir, which is set up after clear-cutting, slash burning and soil preparation before planting, is a traditional silviculture practice in South China. However, timber harvest and slash burning can cause substantial loss and redistribution of organic matter. But, there is little research on how different regeneration patterns affect soil respiration in Chinese fir ecosystem. The aim of this study is to investigate in detail the effects of regeneration patterns on soil respiration and its components after a 40 year-old Chinese fir plantation located in the Nanping State Forestry Centre in Fujian Province has been clearcut. This study will help to set up a guideline for forest management. Three regeneration patterns are burning regeneration (BR), natural regeneration (NR) and artificial regeneration (AR) and nearby uncut Chinese fir stand used as a control (CR). Major conclusions were summarized as follows:(1) Diurnal variation of soil respiration was different in summer and winter. The daily change of soil respiration rate in summer could be expressed as an unimodal distribution pattern in BR, NR and AR, but they did not have obvious change in winter, which was similar to the variation of soil temperature. The peak value was found at 13:00-17:00 and the minimum value at 1:00-7:00.(2) The monthly variation of soil respiration was also obvious and it was similar to the variation of soil temperature. During the study period, the range of annual soil respiration rate in CR, BR, NR and AR were 0.79-3.07, 0.62-3.53, 0.67-3.19 and 0.63-2.95μmol·m-2·s-1, respectively. There was no significant difference in total soil respiration and respiration of mineral soil among CR, BR, NR and AR(P<0.05), but significant difference in root respiration rate was found between NR and AR, between NRand CR(P<0.05).(3) Relationships between soil respiration and soil environmental variables wereexamined via a regression analysis. An exponential regression of each CO2 measurement against the corresponding soil temperature at 5 cm was significant (P < 0.05) except for root respiration in BR. A linear regression of soil respiration rate on soil moisture content was not significant for all plots (P > 0.05). The multiple regression model explained 95%, 81%, 86% and 93% of variations in total soil respiration, 90%, 89%, 78% and 88% of variations in the mineral soil respiration, and 61%, 29%, 71% and 46% of variations in the root respiration in the CR, BR, NR and AR respectively. The Q10 values determined from the multiple regression model were from 1.60 to 2.01 for soil respiration, from 1.54 to 2.08 for mineral soil respiration and from 1.62 to 2.05 for root respiration.(4) Both water-soluble organic C and light fraction organic C were correlated with soil respiration. The strong correlation between soil respiration rate and necromass at 20 cm soil depth was observed (P<0.05). No significant correlation was found between soil respiration rate and soil organic C, total N and microbial biomass C.(5) Cumulative soil respiration in CR, BR, NR and AR was 7.20, 6.97, 7.39 and 6.10 tC·hm-2·a-1, respectively. Mineral soil respiration accounted for 79.1%, 71.0%, 64.3% and 79.0% of the total soil efflux, while the root respiration accounted for 20.9%, 29.0%, 35.7% and 21.0% in CR, BR, NR and AR respectively.
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