As dominant biomes,forests play an important and indispensable role in adjusting the global carbon balance under climate change.Therefore,there are scientific and political implications in investigating the carbon budget of forest ecosystems and its response to climate change.Here we synthesized the most recent research progresses on the carbon cycle in terrestrial ecosystems,and applied an individual-based forest ecosystem carbon budget model for China(FORCCHN) to simulate the dynamics of the carbon fluxes of forest ecosystems in the northeastern China.The FORCCHN model was further improved and applied through adding variables and modules of precipitation(rainfall and snowfall) interception by tree crown,understory plants and litter.The results showed that the optimized FORCCHN model had a good performance in simulating the carbon budget of forest ecosystems in the northeastern China.From 1981 to 2002,the forests played a positive role in absorbing carbon dioxide.However,the capability of forest carbon sequestration had been gradually declining during the the same period.As for the average spatial distri-bution of net carbon budget,a majority of the regions were carbon sinks.Several scattered areas in the Heilongjiang Province and the Liaoning Province were identified as carbon sources.The net carbon budget was apparently more sensitive to an increase of air temperature than change of precipitation.
选取耕地面积居世界第二位的印度作为研究区域,利用中国自主研发的区域气候模式(RIEMS2.0)和土地利用变化资料,进行潜在植被和雨养农田的长时间积分模拟对比试验,分析了印度农田扩张对区域气候的影响及其机制。结果表明:农田扩张使得印度区域平均气温升高0.1℃,平均降水强度减少0.1 mm·d^(-1),总降水量减少12.8%;农田扩张的气候效应存在明显区域差异和季节差异,在副热带湿润区气温增加0.5~1.0℃,在干旱和半干旱区气温增加0.3~0.5℃,在热带地区气温则下降;农田扩张使得季风前期和冬季气温分别增加0.5℃和0.2℃;季风后期气温降低0.5℃,季风季节气温没有明显变化;在副热带湿润区、干旱和半干旱区降水明显减少,干旱季节特别是季风前期降水减少最为显著,达到0.3 mm·d^(-1);印度农田扩张使得年平均感热通量增加、潜热通量减少,其中植被的蒸散作用引起的潜热通量的变化,尤其是季风前期潜热通量明显减少,是区域气温升高、降水减少的重要原因;农田扩张使得印度大陆上空(850 h Pa高度)受较弱的辐散环流控制,辐散下沉气流是造成当地气温升高、降水减少的又一原因。
Driven by the global model,Beijing Climate Center Climate System Model version 1.1(BCC_CSM1.1),climate change over China in the 21st century is simulated by a regional climate model(RegCM4.0)under the new emission scenarios of the Representative Concentration Pathways—RCP4.5 and RCP8.5.This is based on a period of transient simulations from 1950 to2099,with a grid spacing of 50 km.The present paper focuses on the annual mean temperature and precipitation in China over this period,with emphasis on their future changes.Validation of model performance reveals marked improvement of the RegCM4.0 model in reproducing present day temperature and precipitation relative to the driving BCC_CSM1.1 model.Significant warming is simulated by both BCC_CSM1.1 and RegCM4.0,however,spatial distribution and magnitude differ between the simulations.The high emission scenario RCP8.5 results in greater warming compared to RCP4.5.The two models project different precipitation changes,characterized by a general increase in the BCC_CSM1.1,and broader areas with decrease in the RegCM4.0 simulations.
