Carbon Loss From Coarse Woody Debris Of Secondary Larix Kaempferi Forest In Dalaoling National Wilderness Preservation System And Its Influencing Factors

Coarse woody debris(CWD)is one of the C pools in forest ecosystem,which plays an important ecological role in the material cycle of forest ecosystem,it is important for us to understand the role of CWD in the global carbon cycle.In this paper,the density and the C,N,P contents of CWD of different decay grades in the secondary Larix gmelinii forests at different altitudes in Dalaoling area were investigated and sampled,the reserves and the C storage characteristics of CWD of secondary Larix gmelinii forest in this area were analyzed.The CWD respiration rate of different decay grades in the secondary Larix gmelinii forest was measured by LI-8100 A portable soil respirator every month,the annual C flux of CWD in this region is estimated.At the same time,the experiment of CWD leaching was designed,and the CWD of different decay grades was placed in the open space under the forest,and the CWD was leached by natural rainfall,the leachate and blank rainwater collected were sampled and measured monthly to analyze the change of C,N,P in CWD caused by leachate.The main results were as follows:(1)The average reserves of CWD in the investigated area is 46.81±8.16 t/hm2.Log was the main type of CWD in this area.Among all CWD,Decay Class I has the largest reserves.As for characteristic of CWD diameter class,10-20 cm has the greatest reserves.The difference of CWD reserves between different altitudes is not significant.(2)The average C content of CWD in this study was 475.60 g/kg,which showed a trend of decreasing with the increase of decay class.N was enriched with the increase of decay class of CWD.The P content of CWD decreased slightly with the increase of decay class.The C,N and P of CWD with different decay grades were significantly different.The average C,N and P storage of CWD respectively were 22.67±3.99 t/hm2,327.98±58.85 kg/hm2 and 29.48±7.25 kg/hm2.(3)Environmental factors have a significant impact on the CWD reserve distribution characteristics,especially the CWD type and decay grade characteristics.Stand density is the most important environmental factor.Stand density and canopy density are positively correlated with CWD reserve distribution.The slope aspect,altitude and soil depth were negatively correlated with the reserve distribution of CWD.(4)There is a release of C in the process of leaching CWD,and the adsorption of N and P by CWD is possible.The change of C,N and P of CWD increased with the increase of decay grade,but the difference was not significant.(5)The respiratory rate of CWD in a typical secondary Larix kaempferi forest in Dalaoling area showed a single peak in August.The respiration rate of CWD increased first and then decreased with the increase of decay grade.The respiration rate of CWD was positively correlated with air temperature and humidity,and CWD was more affected by air temperature.The estimated annual CWD carbon flux of the secondary Larix kaempferi forest was 35.39±7.36 g C·m-2·a-1.