基于PnET-CN模型的亚热带人工针叶林生产力与固碳潜力模拟研究

A generalized, lumped-parameter ecological model PnET-CN was calibrated and validated for a subtropical coniferous plantation in southem China. PnET-CN model describes the biogeochemical cycles of carbon(C)and nitrogen(N)and can assist in estimating carbon sequestration potential. For validation of PnET-CN, data from coniferous forest plantations in southern China was used. Simulated daily gross primary productivity(GPP)from 2005 to 2007 agreed well with observations(R2=0.56, S.D.=0.009). Simulations of monthly soil res-piration(R3)from 2005-2007 agreed well with R8 observations(R2=0.67, S.D. =0.03). Simu-lated annual net primary productivity(NPP)from 1998-2006 was 803±33 gCm-2a-1, about 4% higher than NPP observation(752±51 gCm-2a-1). Simulations of annual NEP from 2005-2007 only overestimate 9 gCm-2a-1(4%), 4 gCm-2a-1(1%)and 34 gCm-2a-1(8%)compared to NEP observations, respectively. Simulated annual foliar N concentration(FolNCon)(1.09%)is 10% lower than observed monthly FolNCon(0.87%-1.58%). Simulated annual N leaching(0.26 gNm-2)is about 10% lower than leaching observation(0.29 gNm-2). PnET-CN model valida-tion indicates that PnET-CN is capable to simulate daily GPP, annual NPP, annual NEP, monthly R,, annual FolNCon and annual nitrate N leaching for subtropical coniferous planta-tions in southem China. The results obtained from the validation test revealed that PnET-CN model can be used to simulate carbon sequestration of planted coniferous forests in southern China to a high level of precision. Sensitivity analysis suggests that great care should be taken in developing generalizations as to how forests will respond to a changing climate. PnET-CN performed satisfactorily in comparison to other models that have already been calibrated and validated in coniferous planted subtropical forests in China. Based on PnET-CN validation and its comparison to other models, future improvement of PnET-CN should focus on seasonal foliar N dynamics and the effects of water stress on autotrophic respirations in subtropical coniferous plantations in southern China.     

中国亚热带地区造林对土壤碳周转的影响

Afforestation in China's subtropics plays an important role in sequestering CO2 from the atmosphere and in storage of soil carbon (C). Compared with natural forests, plantation forests have lower soil organic carbon (SOC) content and great potential to store more C. To better evaluate the effects of afforestation on soil C turnover, we investigated SOC and its stable C isotope (δ13C) composition in three planted forests at Qianyanzhou Ecological Experimental Station in southern China. Litter and soil samples were collected and analyzed for total organic C, δ13C and total nitrogen. Similarly to the vertical distribution of SOC in natural forests, SOC concentrations decrease exponentially with depth. The land cover type (grassland) before plantation had a significant influence on the vertical distribution of SOC. The SOC δ13C composition of the upper soil layer of two plantation forests has been mainly affected by the grass biomass 13C composition. Soil profiles with a change in photosynthetic pathway had a more complex 13C isotope composition distribution. During the 20 years after plantation establishment, the soil organic matter sources influenced both the δ13C distribution with depth, and C replacement. The upper soil layer SOC turnover in masson pine (a mean 34% of replacement in the 10 cm after 20 years) was more than twice as fast as that of slash pine (16% of replacement) under subtropical conditions. The results demonstrate that masson pine and slash pine plantations cannot rapidly sequester SOC into long-term storage pools in subtropical China.     

变形观测在藤州中学滑坡治理工程中的应用

结合工程实例,介绍工程测量在藤州中学滑坡治理工程施工中的应用,对地质滑坡进行变形观测,为滑坡治理工程施工提供科学的数据和施工指导,同时为滑坡运行状态的稳定性提供依据。     

地质滑坡变形监测方法探讨

结合工程实例,介绍了变形监测在藤州中学滑坡治理工程中的应用。实践证明,对地质滑坡进行变形观测,可为滑坡治理工程施工提供科学的数据和施工指导,同时也为滑坡运行状态的稳定性提供依据。