| The present paper we present a study of a Chinese arborvitae plantation in the northern of Beijing7years after thinning treatments. We aimed to quantify the effects of silviculture thinning on distribution of trees, undergrowth, and soil carbon pools, and to evaluate the impact on carbon fluxes in litterfall, soil and stem. These findings from our study are expected to contribute to the knowledge base needed for enhanced forest carbon sequestration through improved management strategies. At22years old, the oriental density plots were about5900trees per hectare, and then these forests respectively reduced4100,3500and2900trees per hectare in three replicates. The result showed:(1) There is a significant difference between plots7years after thinning treatment. The total biomass in the N4100was about1.25times than in the control plots, while measurement of N3500^N2900plots was about87.41%、78.36%o The biomass of wood, foliage and root were similar to the total biomass in different treatments. The response of shrub biomass to thinning was different from that of trees biomass, which was affected significantly by the thinning treatment. The thinning prescriptions considered in this study appeared to have resulted in a considerable increase in undergrowth biomass.(2) Biomass of fine root in the N4100, N3500and N2900plots increased respectively0.0030、0.0010、0.0004t C ha-1compared with the control plots. Additionally, we observed that there were a significant difference between the control plots and the N4100plots.(3) The forest detritus in the N4100、N3500、N2900compared with the control plots increased averagely5.48、6.46、13.77t C ha-1because of the much differences in forest biomass from the forest floor. We also found the stumps biomass have relationship with thinning numbers rather than the thinning intensities.(4) Thinning treatments have a significant effect on soil carbon stocks, and the difference between N4100forest and control was largest. For each forest investigated, soil bulk density increased with development of soil depth, while soil organic matter was opposite.(5) Annual biomass accumulation measured in the N4100、N3500and N2900plots respectively was increased4.99、3.65、2.93t C ha-1yr-1compared with the control plots. And the significant differences could be found between the control plots and the light plots.(6) Thinning treatments have a significant effect on respiration fluxes from soil, heterotrophic, root and litterfall which have negative relationship with the thinning intensities. Compared with the control plots, plots from the N4100, N3500and N2900respectively increased73%,45%,31%in the soil respiration, increased101%,75%,37%in the heterotrophic respiration, increased91%,61%,37%in the root respiration, increased215%,99%,35%in the litterfall respiration. Soil respiration has a positive correlation with the soil temperature (0-5cm and5-10cm) and soil water content (0-10cm and10-20cm). We found that the highest value in the April and the lowest value in soil respiration during the growing time in2010and2011.(7) Thinning treatments have a significant effect on stem respiration fluxes, which have positive relationship with the thinning intensities. Compared with the control plots, plots from the N4100, N3500and N2900respectively increased31%,53%,65%in the stem respiration. We found that the highest value in the April and the lowest value in soil respiration during the growing time in2011.(8) In the mountain area of Beijing, NPP measured in N4100, N3500and N2900plots in Chinese arborvitae plantation were2.28-,1.86-and1.73-fold higher than in the control plots. Similar measurements in the control plots was about0.43,0.54,0.56, compared with the N4100, N3500and N2900plots. Among the treatment, heterotrophic respiration/NEP appeared conserved16%-19%.(9)7years after thinning treatments, Chinese arborvitae plantation in mountain area of Beijing (original density with5900trees per hectare) appled to4100trees per hectare. |
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