| Global warming has become one of the primary environmental problems which human being have been facing, and has become the core concern of public and science. As one of the important gases of greenhouse, terrestrial ecosystem CO2fluxes plays an important role in maintaining the balance of the global carbon cycle. The forest ecosystem, being the most important terrestrial ecosystems, is not only rich in biodiversity, but also an important carbon pool. However, with the development of the society and economy, the forest ecosystem has been constantly destroyed, which leading to the continuing degradation of system functions; On the other hand, the national governments and public has been commit themselves to restore damaged ecosystems by means of natural and artificial forces.presently,study on forest carbon cycle is mainly concentrated on the virgin forest, lacking of awareness on secondary forest formed by human interference and plantation carbon cycle process, especially as the process of soil respiration of forest ecosystem carbon emissions.Subtropical evergreen broad-leaved forests has2.5million km2in China, be rich in biodiversity, structure complex and diverse,it’s important for us to improve social economic and protect the ecological environment. However, due to the long-term interference by human, forest’s degradation is extremely serious, and the function of ecosystems have been seriously damaged. Afforestation of large-scale area began from the late1980s in the region, forest coverage rate rising, vegetation condition has also been restored, but more forest disturbance from human because the forest management activities intensified. As a result, forest disturbance and recovery appeared, ultimately, there are a lot of uncertainty when estimate the carbon source and sink in subtropical area.121-hm2plots which included four forest types with different human disturbances were established in2009in Gutianshan, and there were three1-hm2plots for each type of the forests. The four type included an old growth forest (OF, almost no human disturbance), two secondary forests (SF1, a secondary forest restored from a clear cutting forest in about50years ago; SF2, a secondary forest experienced clear cutting about50years ago and selective cutting about20years ago), and a plantation (AF, planted about20years ago). Our objectives were to study the soil respiration in subtropical evergreen board-leaved forests with different human disturbances.From our research we get the soil respiration werel.05、1.13、1.26and0.84μmol·m-2·d-1in OF, SF1, SF2and AF plots, respectively. Soil respiration rate of plantation was significantly lower than those of other three forest types. On the diurnal scale, there were no significant variations in soil respiration rates of four forest types. Our results indicated that the rate of soil respiration measured in anytime during the whole day can be used to predicted daily accumulated soil carbon release. Significantly positive relationships were found between soil respiration and surface soil temperature (R square ranged from0.93-0.99) in four forest types. There were not significant relationships between soil respiration and soil water content. The Q10of old growth forest and plantation were significantly higher than those of other two forest types. Such of these results showed that soil respiration rate of plantation with the strongest interfered intensity was reduced significantly. The secondary forests’soil respiration was consistent with old growth forest. Soil temperature was the most important driving factor of soil respiration in our research.All the above conclusions implied that different human disturbance placed different influence on the soil respiration of the forest types. It will be very important for estimating their role in regional carbon cycles, in addition, the conclusion that there was no significant variations in soil respiration rates is of great importance in guiding further study on diurnal soil respiration. |
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