季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲(26.7°N,115.1°E)人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO(Ecological Assimilation of Land and Climate Observation)模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方(R2)及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬(发生较严重干旱胁迫)较2004年同期(干旱程度轻)相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%~60%。模拟与观测结果均表明,2003年7月下旬每天正午的波文比大都介于1~2.2,而2004年同期正午的波文比则介于0.2~0.6。EALCO模型通过Ball模型将植物碳水过程耦合在一起,从而可以很好的模拟植物的气孔行为,进而准确的模拟植物水热过程对干旱的响应。土壤水分匮乏对冠层导度的限制是2003年干旱期间冠层潜热通量模拟值下降的根本原因。
Using water erosion data from three national soil erosion remote-sensing surveys (the first:1985-1986; the second:1995-1996; the third: 2000-2001) and carbon density data from the second national soil survey (19...
详细信息
Using water erosion data from three national soil erosion remote-sensing surveys (the first:1985-1986; the second:1995-1996; the third: 2000-2001) and carbon density data from the second national soil survey (1979-1992), we computed soil carbon removal caused by water erosion, and analyzed its spatial distribution and temporal dynamics in China. Results revealed that the total removal of soil carbon caused by water erosion was about 74.61 Tg C y^-1 , of which 51.49 Tg C y^-1 was organic carbon, and 23.12 Tg C y^-1 was inorganic carbon. The main erosion level of the whole is moderate erosion. Among the seven erosion regions, the Southwest Karst Region had the most significant removal of soil organic carbon, which was 26.48% of the total and mainly due to its moderate erosion. In contrast, about 67.62% of the soil inorganic carbon removal occurred in the Loess Plateau Region, which mainly due to its highly intense and intense erosion. As a whole, the removals of soil carbon caused by water erosion represented a decreasing trend among the three national soil erosion remote-sensing surveys. Between the first and the second survey, soil carbon removal decreased by 11.66 Tg C y^-1 , of which 81.93% was organic carbon. Compared with that in the second survey, soil carbon removal decreased by 1.65 Tg C y^-1 in the third survey, of which 1.514 Tg C y^-1 was organic carbon, and 0.134 Tg C y^-1 was inorganic carbon.
To investigate forest carbon sequestration and its role in addressing global climatic change, it is important to assess carbon emissions caused by major disturbances from forest ecosystems to the atmosphere. Based on ...
详细信息
To investigate forest carbon sequestration and its role in addressing global climatic change, it is important to assess carbon emissions caused by major disturbances from forest ecosystems to the atmosphere. Based on forestry statistics on the occurrence of each disturbance and acceptable assumptions on the process and proportion of biomass carbon transferred to other pools due to each disturbance, this paper estimates the direct carbon emission from Chinese forest vegetation caused by three major disturbances, that is, wood harvesting, fire, and DPR, from 1990 to 2009. Results showed that over the past two decades, Chinese forests have been disturbed rather intensively by wood harvesting, fires, and DPR, with clear upward occurrence trends of the three disturbances in the early 21 st century. As a result, the average annual carbon emissions caused by wood harvesting, fires, and DPR were 34.25 Tg, 1.61 Tg, and 4.29 Tg, respectively, during 1990–2009. The aggregate annual carbon emission due to these three major disturbances was 40.15 Tg during 1990–2009, which was 30.79 Tg during 1990–1999 and 49.51 Tg during 2000–2009. According to the analysis of carbon emissions from different forest regions, there were obvious regional characteristics of the average annual carbon emission caused by each disturbance. However, it was difficult to identify clear cause and effect relationships among disturbances to explain the spatial variation of carbon emissions from forest vegetation in China. Disturbances have significant influences on carbon balance of forest ecosystems in China. This finding suggests the opportunities for increasing forest carbon sequestration by disturbance-aimed sustainable long-term management of forest resources, as well as the necessity of considering the role of major disturbances in carbon budget models for forest ecosystems or terrestrial ecosystems.
暂无评论