Carbon Dynamics in Woody Biomass of Forest Ecosystem in China with Forest Management Practices under Future Climate Change and Rising CO_2 Concentration

It is critical to study how different forest management practices affect forest carbon sequestration under global climate change regime.Previous researches focused on the stand-level forest carbon sequestration with rare investigation of forest carbon stocks influenced by forest management practices and climate change at regional scale.In this study,a general integrative approach was used to simulate spatial and temporal variations of woody biomass and harvested biomass of forest in China during the 21st century under different scenarios of climate and CO2 concentration changes and management tasks by coupling Integrated Terrestrial Ecosystem Carbon budget(InTEC) model with Global Forest Model(G4M).The results showed that forest management practices have more predominant effects on forest stem stocking biomass than climate and CO2 concentration change.Meanwhile,the concurrent future changes in climate and CO2 concentration will enhance the amounts of stem stocking biomass in forests of China by 12%–23% during 2001–2100 relative to that with climate change only.The task for maximizing stem stocking biomass will dramatically enhance the stem stocking biomass from 2001–2100,while the task for maximum average increment will result in an increment of stem stocking biomass before 2050 then decline.The difference of woody biomass responding to forest management tasks was owing to the current age structure of forests in China.Meanwhile,the sensitivity of long-term woody biomass to management practices for different forest types(coniferous forest,mixed forest and deciduous forest) under changing climate and CO2 concentration was also analyzed.In addition,longer rotation length under future climate change and rising CO2 concentration scenario will dramatically increase the woody biomass of China during 2001–2100.Therefore,our estimation indicated that taking the role of forest management in the carbon cycle into the consideration at regional or national level is very important to project the forest carbon sequestration under future climate change and rising atmospheric CO2 concentration.

Mapping Cropland in Ethiopia Using Crowdsourcing

The spatial distribution of cropland is an important input to many applications including food security monitoring and economic land use modeling. Global land cover maps derived from remote sensing are one source of cropland but they are currently not accurate enough in the cropland domain to meet the needs of the user community. Moreover, when compared with one another, these land cover products show large areas of spatial disagreement, which makes the choice very difficult regarding which land cover product to use. This paper takes an entirely different approach to mapping cropland, using crowdsourcing of Google Earth imagery via tools in Geo-Wiki. Using sample data generated by a crowdsourcing campaign for the collection of the degree of cultivation and settlement in Ethiopia, a cropland map was created using simple inverse distance weighted interpolation. The map was validated using data from the GOFC-GOLD validation portal and an independent crowdsourced dataset from Geo-Wiki. The results show that the crowdsourced cropland map for Ethiopia has a higher overall accuracy than the individual global land cover products for this country. Such an approach has great potential for mapping cropland in other countries where such data do not currently exist. Not only is the approach inexpensive but the data can be collected over a very short period of time using an existing network of volunteers.

基于模型模拟的中国秸秆还田固碳潜力空间格局分析（英文）

农作物秸秆还田作为农田土壤和养分管理的推荐做法之一,对于土壤有机碳(SOC)固定和CO_2减排具有重要意义。本研究利用环境政策综合气候模型(EPIC)模拟了4种作物秸秆还田情形下2001年至2010年中国农田表层土壤有机碳变化及其空间格局。模拟结果显示,秸秆完全移除(CR0%)下的土壤有机碳损失为28.89 Tg yr^(–1),当前30%的秸秆还田(CR30%)能够减缓22.38 Tg C yr^(–1)的碳损失。若秸秆还田率从30%提高至50%(CR50%)乃至75%(CR75%),中国农田表层土壤将变为净碳汇。中国农田表层土壤固碳潜力在CR50%和CR75%情形下分别可达25.53 Tg C yr^(–1)和52.85 Tg C yr^(–1),且在不同农业区存在空间异质性。单位面积土壤固碳潜力在西北和华北地区最高,而华东最低。华北地区具有最高的区域固碳潜力。在这十年间,CR50%和CR75%情形下增加的土壤表层有机碳相当于减少了1.4%和2.9%的中国CO_2排放总量。总之,我们建议鼓励我国农民将原本直接焚烧或用作家用燃料的秸秆返还田间以改善土壤性质和减缓大气CO_2增加,尤其是华北地区更应推行这一举措。