Grain For Green Program Research Articles

Effects of ecological engineering on water balance under two different vegetation scenarios in the Qilian Mountain, northwestern China

Abstract Study region The Qilian Mountain, northwestern China. Study focus Land degradation is a global eco-environmental issue. To minimize soil erosion and land degradation, China has implemented several ecological engineering such as “Grain for Green” program (GFG) since 1999. Relationship between vegetation and water budgets in catchments has been widely studied, however very few studies addressed the effects of eco-environmental restoration on water balance in mountain areas, especially with a focus on soil moisture content. Therefore SWAT model was used to quantify the effects of ecological engineering actions (taken place in 2005) on water balance in Qilian Mountain. New hydrological insights for the region After the ecological engineering, water yield and soil water content experienced an increment of 32%, and 46%. The opposite trend was monitored in runoff and evapotranspiration, which decreased by 48% and 4%, respectively. Therefore ecosystem restoration have increased soil water retention capacity, a greater proportion of precipitation reaching the catchment is absorbed by the soil rather than flowing out of the region as runoff. Therefore trade-offs between environmental sustainability and water resources security should be carefully addressed in arid region that experienced severe water shortages.

Land cover and landscape changes in Shaanxi Province during China’s Grain for Green Program (2000–2010)

This study examines landscape changes in the context of China's national Grain for Green (GFG) policy, one of the world's largest "payment for environmental/ecosystem services" (PES) programs. We explored landscape structures and dynamics between 2000 and 2010 in Shaanxi Province, the Chinese province with the greatest amount of cropland conversion and reforestation in recent decades. We used Landsat Thematic Mapper (TM)-derived data and landscape metrics for six land cover classes to determine (1) the major land cover changes during enforcement of the policy, (2) the spatial and temporal variations in these changes, and (3) the effects of land cover changes on landscape structure and dynamics. The results suggested that provincial-level land cover changes modestly reflected the goals of the GFG. Over the 10-year study period, the forest and grassland coverages expanded from 95,737.9 to 97,017.4km(2) and from 37,235.9 to 40,613.1km(2), respectively, while the cropland coverage decreased from 59,222.8 to 54,007.6km(2). The conversion direction differed regionally: the targeted croplands in Shanbei, namely, types III and IV, were mainly transformed into grassland while those in Shannan were mainly transformed into forestland. Reforestation was associated with increased inter-landscape aggregation and connection. Despite this large-scale reforestation trend, we found notable and significant differences in the land cover changes at the subprovincial level.

Policy shifts influence the functional changes of the CNH systems on the Mongolian plateau

By applying the concept of the coupled natural and human system (CNH), we compared spatiotemporal changes in livestock (LSK), land cover, and ecosystem production to understand the relative roles that natural and social driving forces have on CNH dynamics on the Mongolia plateau. We used socioeconomic and physical data at prefecture level for Inner Mongolia and Mongolia from 1981 through 2010 to represent changes in net primary productivity (NPP), enhanced vegetation index (EVI), precipitation, annual average temperature, LSK, livestock density (LSKD), land cover change (LCC), gross domestic production (GDP), and population (POP). The ratios such as LSK:NPP, LSKD: EVI, LSKD:albedo, LSK:POP, and LSK:GDP were examined and compared between Inner Mongolia and Mongolia, and structural equation modeling (SEM) was applied to quantify the complex interactions. Substantial differences in LSK, POP, and economic development were found among the biomes and between Inner Mongolia and Mongolia. When various indicators for policy shifts—such as the World Trade Organization (WTO) for China, the Third Campaign to Reclaim Abandoned Agriculture Lands (ATAR-3), and the Grain for Green Program for China (GFG)—were added into our SEM, the results showed significant change in the strength of the above relationships. After China joined the WTO, the relationships in Inner Mongolia between LSKD:LCC and LSKD:NPP were immensely strengthened, whereas relationships in NPP:LCC were weakened. In Mongolia, the ATAR-3 program first appeared to be an insignificant policy, but the Collapse of the Soviet Union enhanced the correlation between LSKD:LCC, weakened the connection of LCC:NPP, and did not affect LSKD:NPP. We conclude that human influences on the Mongolian CNH system exceeded those of the biophysical changes, but that the significance varies in time and per biome, as well as between Inner Mongolia and Mongolia.

Drivers of changes in ecosystem service values in Ganjiang upstream watershed

Land use change and land-cover can influence ecological functions and ecosystem services. Based on Xie's coefficient of ecosystem service value, land use change in Ganjing upstream watershed from the year 1990 to 2010 and the ecosystem service value caused by the land use change were quantitatively analyzed. Based on the statistical data and relevant research results, a gray correlation degree analysis was done between ecosystem services value (ESV) and its seven potential impact factors, i.e. Grain for Green program, population, gross domestic product (GDP), urbanization level, investment in fixed assets, the proportion of secondary industry and tertiary industry proportion. The boosted regression tree method was used to identify the driving factors for the changes of ESV during 1990–2010, 1990–1995, 1995–2000, 2000–2005 and 2005–2010 periods. The results showed that: (1) all seven indexes can affect the changes of ESV in Ganjiang upstream watershed during the study periods, (2) during 1990–2010 and from 2000 to 2005, the Grain for Green program is the most important factor influencing the ESV. The proportions of tertiary industry and GDP are the main factors influencing the ESV, whereas from 2000 to 2005 the main influential factor is GDP.

Effects of Grassland Conversion From Cropland on Soil Respiration on the Semi‐Arid Loess Plateau, China

Soil respiration is considered to be the second largest terrestrial carbon flux, and is influenced by land use changes. The impact of a cropland to grassland program on soil respiration was quantified. It tried to identify the dominant factors driving soil respiration along the restoration project of “Grain for Green Program” on the semiarid Loess Plateau, China. Soil respiration and different abiotic and biotic factors were measured for cropland and grasslands after five, 15, and 30 years of natural restoration. Soil respiration (g C m−2 d−1) was significantly greater for grassland with litter left that had been restored for 15 years than for cropland and grassland (five years), but did not significantly change from 15 to 30 years. Soil temperature and litter were the main factors affecting soil respiration along the restoration chronosequence. The contribution of litter to soil respiration after 15 years restoration was about 12%. The temperature sensitivity of the soil respiration ranged from 1.30 in the wheat land to 2.44 in the 30 years restoration grassland with litter left, and it increased with litter removed in the grasslands. Our findings suggest that grasslands after 15‐year natural restoration must be utilized properly to balance changes in soil respiration with the soil organic carbon accumulation during the cropland to grassland restoration process.

Biomass accumulation and carbon sequestration in an age-sequence of Zanthoxylum bungeanum plantations under the Grain for Green Program in karst regions, Guizhou province

Ensuring ecological security in the environmental degradation has always been a top priority in China. Under the Grain for Green Program (GGP), millions of hectares of farmland in the karst region of Guizhou province have been converted into Zanthoxylum bungeanum plantations in order to arrest and reverse “rocky desertification”. The aim of this study was to estimate biomass increment and carbon accumulation in four different aged (1-, 4-, 7- and 10-year-old) Z. bungeanum stands, as well as the distribution of carbon stock among the various biomass components and soil depths. The total plant biomass measured for the four stands of different ages was 0.05, 6.76, 12.22, and 16.71Mgha−1, respectively. Compared with other plant species in the region, Z. bungeanum plantations has a larger capacity for accumulating biomass. The C content in components of Z. bungeanum tree ranged from 40.47% to 48.64% with the mean value of 44.67%. The use of the standard coefficient (50%) in converting biomass into C storage results in 10% overestimation. Soil organic carbon (SOC) storage at the top soil (0–30cm) increased from 75.22MgCha−1 in 1-year-old stand to 80.06MgCha−1 in 10-year-old stand, and decreased with increasing soil depth for each stand age. Total ecosystem C storage increased with plantation age, averaging 75.24, 79.79, 84.43, and 87.62MgCha−1, respectively, of which more than 90% was stored in the soil. Our study suggests that the protection of SOC in surface soils during plantation management practices plays a crucial role in improving the C sequestration. Data of plantation area and annual biomass C accumulation rate (under the GGP in Guizhou province) indicate a net C sink of 6.35×106Mg in 2010, corresponding to a 4.92% compensation of C emission from energy consumption in that year. Besides increasing C storage over time, the large-scale planting of Z. bungeanum has the potential of restoring severely degraded soils in the karst region of SW China.

Aridity trend and response to vegetation restoration in the loess hilly region of northern Shaanxi Province

Detecting variation trend in dry-wet conditions can provide information for developing strategic measures to mitigate the impacts of global warming, particularly in dry regions. Taking the hilly region of northern Shaanxi on the Loess Plateau as a case area, this study analyzed the trend of aridity variation during 1981–2012, and explored the effect of vegetation restoration promoted by the Grain-for-Green (GFG) program implemented in 1999. The results indicated that the aridity in the region was non-significantly increased by 0.88% per year during 1981–2012, showing a drying trend. This drying trend and amplitude were changed by the influence of vegetation restoration promoted by the GFG program, based on two findings. The first one was that the aridity variation tended to increase during 1981–1999 while it turned to decrease during 2000–2012, with the regional mean relative change rate changed from 2.45% to −1.06%. This distinction was more remarkable in the loess gully region, where the vegetation was improved more obviously. The second one was that the mean vegetation coverage as indicated by EVI increased by 0.90% to 4.32% per year at county level, while the aridity decreased by 0.14% to 2.32% per year during 2000–2012. The regression analysis using the mean county data indicated that the change rate of aridity was negatively related to that of EVI with the coefficient of determination (R2) of 0.56, illustrating that around half of the aridity decline was explained by the EVI change. The mechanism of this effect was complicated, but it was found that the wind speed decline induced by the vegetation improvement could be an important contributor. It is concluded that the region became drier during 1981–2012, but the eco-restoration reduced the drying speed. However, this conclusion is involved in uncertainties, and further study based on experiments is needed to confirm the effect of the GFG-promoted vegetation restoration.

Satellite evidence for significant biophysical consequences of the “Grain for Green” Program on the Loess Plateau in China

AbstractAfforestation has been implemented worldwide as regional and national policies to address environmental problems and to improve ecosystem services. China's central government launched the “Grain for Green” Program (GGP) in 1999 to increase forest cover and to control soil erosion by converting agricultural lands on steep slopes to forests and grasslands. Here a variety of satellite data products from the Moderate Resolution Imaging Spectroradiometer were used to assess the biophysical consequences of the GGP for the Loess Plateau, the pilot region of the program. The average tree cover of the plateau substantially increased because of the GGP, with a relative increase of 41.0%. The GGP led to significant increases in enhanced vegetation index (EVI), leaf area index, and the fraction of photosynthetically active radiation absorbed by canopies. The increase in forest productivity as approximated by EVI was not driven by elevated air temperature, changing precipitation, or rising atmospheric carbon dioxide concentrations. Moreover, the afforestation significantly reduced surface albedo, leading to a positive radiative forcing and a warming effect on the climate. The GGP also led to a significant decline in daytime land surface temperature and exerted a cooling effect on the climate. The GGP therefore has significant biophysical consequences by altering carbon cycling, hydrologic processes, and surface energy exchange and has significant feedbacks to the regional climate. The net radiative forcing on the climate depends on the offsetting of the negative forcing from carbon sequestration and higher evapotranspiration and the positive forcing from lower albedo.

Aeolian desertification and its control in Northern China

Aeolian desertification is a kind of land degradation through wind erosion resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in Northern China. To compare the results of remote sensing data in the late 1950s, 1975, 1987, 2000 and 2010, we can summarize that the expansion of aeolian desertified land in Northern China has been accelerated for 5 decades, as its annual expanded rate was 1,560 km2 during the late 1950s and 1975, 2,100 km2 between 1975 and 1988, 3,600 km2 from 1988 to 2000, and -1,375 km2 from 2000 to 2010. The desertified land kept expanding before 2000 and began to get rehabilitated since 2000. The impact of human activity on the aeolian desertification process is much more active than that from natural process which mainly incarnates on land use change (from rangeland to farmland) and increased land use intensity (over-cultivation, over-grassing, and over-fuelwood collection). The natural vegetation cover destroyed by the human activities has accelerated the development of aeolian desertification. China has made great progresses in understanding and combating aeolian desertification through decades of effort and there were many projects carried out for the prevention and control purpose. The National Project of Grain for Green Program is the most important one with 1060 counties of 22 provinces involved. The objective is to withdraw 3.67 million ha of dry land farming and degraded steppe, and 5.13 million ha of aeolian desertified land suited to reforestation and re-vegetation will be rehabilitated. There are about 8 million ha of lands suffering from aeolian desertification will be brought under control in the next ten years and 26.67 million ha of windbreaks will be planted. The total investment from the central government is estimated to be 75 billion RMB (11 billion USD).

Influencing Factors of Information Channels Adoption of Forest Farmers on Grain for Green Program in Western China

Forestry ecological projects have a huge impact on the living standard of forest farmers. Thus, information channels forest farmers choose to know about the information of these projects have great importance. The purpose of this study is to find out the main factors that influencing the adoption of these information channels of forest farmers in Western China. Rough set theory is used to solve the problem of main factors reduction. The result shows that total income from working outside, income of forestry, income of agriculture, forestry reforestation subsidy, non-commercial forest subsidy, forest seed subsidy, living expenditure and forest areas are the main factors that influencing the adoption of different channels.

Streamflow regimes of the Yanhe River under climate and land use change, Loess Plateau, China

Soil and water conservation measures including terracing, afforestation, construction of sediment-trapping dams, and the ‘Grain for Green Program’ have been extensively implemented in the Yanhe River watershed, of the Loess Plateau, China, over the last six decades, and have resulted in large-scale land use and land cover changes. This study examined the trends and shifts in streamflow regime over the period of 1953–2010 and relates them to changes in land use and soil and water conservation and to the climatic factors of precipitation and air temperature. The non-parametric Mann–Kendall test and the Pettitt test were used to identify trends and shifts in streamflow and base flow. A method based on precipitation and potential evaporation was used to evaluate the impacts of climate variability and changes in non-climate factors changes on annual streamflow. A significant decrease (p = 0.01) in annual streamflow was observed related to a significant change point in 1996, mostly because of significant decreases in streamflow (p = 0.01) in the July to September periods in subsequent years. The annual base flow showed no significant trend from 1953 to 2010 and no change point year, mostly because there were no significant seasonal trends, except for significant decreases (p = 0.05) in the July to September periods. There was no significant trend for precipitation over the studied time period, and no change point was detected. The air temperature showed a significant increasing trend (p < 0.01), and 1986 (p < 0.01) was the change point year. The climate variability, as measured by precipitation and temperature, and non-climate factors including land use changes and soil and water conservation were estimated to have contributed almost equally to the reduction in annual streamflow. Soil and water conservation practices, including biological measures (e.g. revegetation, planting trees and grass) and engineering measures (such as fish-scale pits, horizontal trenches, and sediment-trapping dams) play an important role in reduction of the conversion of rainfall to run-off. Copyright © 2014 John Wiley & Sons, Ltd.

Historical sediment record of 137Cs, δ-HCH, and δ 13C reflects the impact of land use on soil erosion

This paper reports the concentrations of Cs-137, hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethanes (DDT) and its main degradation products, delta C-3, and organic carbon in pond sediments (0-210 cm, sectioned by 2-20 cm interval) and surface soils (the 0-3 cm horizon) collected in 2010 from Chenjia catchment, which is located in Yanting county in the hilly central Sichuan of China. alpha-, beta-, and gamma-HCH, DDT, and DDD were not detected throughout the sediment profile. Trace concentrations of delta-HCH (0.89-29.31 ng g(-1)) and p,p'-DDE (1.85-6.02 ng g(-1)) were detected only in top 40 cm sediment. The Cs-137 fallout peak in 1963 (corresponding to the 55-60 cm depth), the sedimentary signature left by the last year of HCH use in 1989 (an additional indicator at 20-25 cm), and the obvious original channel bed prior to the construction of the pond in 1956 were used as temporal markers to estimate changes in average sedimentation rate between different periods due to changes in land use. Continuous, marked decrease in average sedimentation rate (i.e., 3.79, 1.35 and 1.07 cm year(-1) in 1956-1963, 1963-1989, and 1989-2010, respectively) over time was observed, probably due to the reforestation, abandoning of steep sloping farmland for afforestation and natural re-vegetation (implementation of the Grain for Green Program), and the conversion of part of gently sloping farmland terraces to orchard land since the 1980s, especially since the 1990s. This was corroborated by the observed decrease (more negative) in delta C-13 of sediment towards the surface, which indicates increased relative contribution of eroded soil particles coming from slopes with increased tree cover in sediment source area. Combined use of Cs-137, delta-HCH, and delta C-13 record in sediments has been demonstrated to be a powerful approach to reconstruction of response in sedimentation rate to historical land use changes.

Rural households' willingness to participate in the Grain for Green program again: A case study of Zhungeer, China

The Grain for Green program (GGP) is one of the most ambitious forestry projects in China. The GGP uses a public payment scheme to propel the participation of rural households in order to make the program acceptable and sustainable. The modification of the GGP for its long-term effectiveness has raised interest from researchers. However, few researchers have realized the role that rural households play in adjusting the GGP. By building an econometric model, we found that the decision making of rural households is optimal when the sum of the marginal benefit from residual farmland and the marginal benefit from agricultural labor time equals the sum of the subsidies for retired farmland, benefits from the increased forest/grassland and the opportunity cost rate of the rural household engaged in agricultural labor divided by agricultural labor efficiency. The results derived by a Logit regression method indicate that the economic benefit and non-monetary values stimulate households' willingness to participate, and households' attitudes have significant effects on their willingness. Our attempt to comprehensively explore the influencing factors concerning households' attitudes, the environment benefits and benefits from the GGP proves to be promising as a reference for future studies and for decision making regarding GGP.

Chinese Grain for Green Program led to highly increased soil organic carbon levels: A meta-analysis

The Grain for Green Program (GGP), initiated in 1999, is the largest ecological restoration project in central and western China. Here, for the first time, we performed a meta-analysis and found that the GGP largely increased the soil organic carbon (SOC). The SOC was increased by 48.1%, 25.4%, and 25.5% at soil depths of 0–20 cm, 20–40 cm, and 40–60 cm, respectively. Moreover, this carbon accumulation has significantly increased over time since GGP implementation. The carbon accumulation showed a significantly more active response to the GGP in the top 20 cm of soil than in the deeper soil layers. Conversion of cropland to forest could lead to significantly greater SOC accumulation than would the conversion of cropland to grassland. Conversion from cropland to woodland could lead to greater SOC accumulation than would the conversion to either shrubland or orchard. Our results suggest that the GGP implementation caused SOC to accumulate and that there remains a large potential for further accumulation of carbon in the soil, which will help to mitigate climate change in the near future.

The tradeoff and synergy between ecosystem services in the Grain-for-Green areas in Northern Shaanxi, China

As an important part of the strategy of Western development, the Grain-for-Green Program (GFGP) was initiated to protect the environment and mitigate disasters. Ecosystem services and their dynamics are considered emerging features of ecological quality and the change in direction by many scholars and practitioners. Extending from ecosystem services (ESs) modeling, we propose a simple and feasible framework for quantitatively assessing the benefits and equilibrium of the consequences of the GFGP. Our starting evaluation shows that ESs has changed dramatically in the GFGP area. By fitting pair-wise ESs’ spatial concordances at the grid-cell level, we have revealed the tradeoffs between provisioning and regulating services and the synergies between the regulating services. The analysis of the variability of the relationship between ESs on different land cover types clearly identifies the vegetation that has produced exceptionally strong ESs. Our findings suggest that quantifying the interactions between ESs may improve the ecosystem-based management practices and support policy-making to address the challenges of the sustainable use of natural resources. The framework designed for regional-scale analysis can help in clearly understanding the interrelations of ESs and make natural resources related decisions more effective and efficient, although this framework still needs to move beyond these fundamental and illustrative analyses to more fully explain the synergies and tradeoffs.

Changes in land use and agricultural production structure before and after the implementation of grain for green program in Western China — taking two typical counties as examples

Soil erosion becomes a serious environmental problem in the world, especially in western China. An effective management practice called the Grain for Green Program (GGP), which was launched in 1999, aims to reduce soil and water loss and alleviate the ecological environment problem in western China. Two typical counties in western China, the Zhongxian (in Chongqing Municipality) and Ansai (in Shaanxi Province) were chosen to evaluate the dynamic changes of land use and agricultural production structure before and after the implementation of the Program in this paper. The results showed that the cultivated land area was reduced by 7.08% from 1989 to 2003. The cultivated land per person was decreased by 8.42% during 1999-2003. Moreover, the stability index of the secondary sector of the economy was increased from 0.91 in the period 1990-1999 to 0.94 in the following ten years. In addition, the stability index of tertiary economic sector increased from 0.88 to 0.92 in Zhongxian county. Meanwhile, the cultivated land area was reduced by 15.48% from 1990 to 1999. The soil erosion modulus was decreased by 33.33% from 1999 to 2006. Also, the stability index of secondary and tertiary economic sectors was 0.86 in the period 1998-2002. However, it decreased by 77% during 2002 to 2007 in Ansai County. These results imply that the Grain for Green Program had different impact on the two regions. Several effective strategies of soil and water conservation have been carried out to ameliorate the sustainable development of ecological environment and economy in these two counties of western China.

Effects of the implementation of ecological restoration policies on soil organic carbon storage in a discontinuous soil region

Estimating soil organic carbon (SOC) storage for soils with discontinuous distribution in the karst regions of southwest China poses a challenge due to the predominant carbonate bedrock. In addition, it is not clear how effective the ecological restoration and reconstruction policies, which have been conducted in this region since the 1990s, have been in terms of SOC sequestration. In this study, we explored the ability of an empirical model and validated it using field survey data to predict the coverage of discontinuous distribution soil in a karst region in southwest China. Employing the soil coverage map, survey data of SOC at a soil depth of 0–15 cm, and three land use/cover maps in 1990, 2004, and 2011, we estimated the changes of SOC storages in the study area. Results showed that the land use/cover changes induced by the implementation of ecological restoration policies promoted SOC storage in the karst region. The SOC storage increased from 2.34 Tg to 3.01 Tg and soil organic carbon density increased from 2.72 kg/m2 to 3.50 kg/m2 over the study period. The mountain closure policy, Grain for Green program, and migration program currently implemented in the karst region have contributed to a decline in the rate of SOC decomposition and the reduction of soil disturbance, which resulted in carbon sequestration in the global carbon cycle while also improving the ecologically fragile karst environment. SOC storage may have been overestimated by almost twofold while ignoring the discontinuous distribution features of soil cover in the karst region. However, along with an increase in both population and agricultural activities, SOC storage in the nonkarst area declined from 1990 to 2011. With the ecological restoration occurring in the karst area, losses of SOC induced by increased farming activities in the nonkarst area should not be ignored.

西南地区退耕还林工程主要林分50年碳汇潜力

为评估西南地区退耕还林工程主要林分未来50a碳汇潜力，调查收集该地区2011年以前退耕还林工程主要造林树种及其造林面积等相关数据资料，利用国家森林资源清查资料中人工林历史数据建立生长模型，结合文献调研获得的相关林分碳计量参数，预测出本区域退耕还林工程7种主要林分碳储量和年碳储量未来变化。结果表明：西南地区退耕还林工程主要林分总碳储量在2020、2030、2040、2050和2060年分别为52.98、73.88-80.57、73.62-102.16、88.41-115.17和77.15-123.36TgC，年总碳储量则分别为3.15、-1.11-2.45、-3.92-1.95、2.08-0.96和0.25-0.73TgC，到2060年华山松、马尾松、柳杉、杉木、柏树、杨树和桉树7种林分碳汇潜力在无采伐情景下分别达到：13.01、15.01、13.44、24.13、28.05、15.63和14.09TgC，可对本地区森林碳汇功能产生明显影响。;Vegetation growth, through photosynthesis, takes up carbon dioxide from the atmosphere and converts to organic carbon into biomass thereby forms a carbon sink. Research on carbon sequestration potential of forests has become a key content to slow down global warming by forestry. To assess carbon sequestration potential in stands under the Grain for Green Program (GGP) in Southwest China, the carbon storages and their annual changes in the GGP-stands in the region were estimated based on: (1) collected data on annual planted area of each tree species under the GGP in Southwest China from 1999 to 2010; (2) empirical growth curves developed for each species of the GGP-stands using growth data about plantation from the National Forest Inventory; (3) parameters associated with stand such as wood density, biomass expansion factor, carbon fraction, the change rate in soil organic carbon content. Two scenarios for forest management option were schemed: scenario A for no harvesting and scenario B for logging at the time of maturity followed by replanting. The results showed that there are seven tree species with over 100,000 hm²of planted area in Southwest- China throughout the recent goal period of strategic planning for the GGP, and their total acreage account for 40.7% of that of all species of the GGP-stands. The expected carbon stocks in these major stands under the Grain for Green Project in Southwest China are52.98TgC, 73.88-80.57TgC, 73.63-102.16TgC, 88.41-115.17TgC and 77.15-123.36TgC(T=10¹²) by the year of 2020, 2030, 2040, 2050 and 2060, and the estimated relevant annual carbon stock changes are 3.15TgC, -1.11-2.45TgC, -3.92-1.95TgC, 2.08-0.96TgC and 0.25-0.73TgC, respectively. In 2060, the carbon stocks in forests of <em>Pinus armandii</em>, <em>Pinus massoniara</em>,<em> Cryptomeria fortunei</em>,<em> Cunninghamia laceolata</em>,<em> Cupressus </em>spp., <em>Populus deltoides</em> and <em>Eucalyptus</em> spp.under the Grain for Green Project in Southwest China will be 13.01TgC, 15.01TgC, 13.44TgC, 24.13TgC, 28.05TgC, 15.63TgC和14.09TgC, respectively, indicating a significant contribute to forest carbon sinks in this region. The <em>Cupressus </em>spp. species play a leading role in carbon sequestration potential in stands under the Grain for Green Project due to highest area proportion in Sichuan province, Chongqing municipality and even Southwest China. The <em>Cryptomeria fortune</em> and<em> Cunninghamia laceolata</em> species play a leading role in Guizhou province; the <em>Eucalyptus</em> spp. and <em>Pinus armandii</em> species in Yunnan province; the <em>Populus deltoides</em> species in Tibet autonomous region.

The creation of farmland by gully filling on the Loess Plateau: a double-edged sword

T “Grain for Green Program” (GGP) is the largest and most acclaimed ecological program since the founding of the People’s Republic of China in 1949. The program is intended to increase vegetation cover, combat land desertification, and improve the eco-environment. The Loess Plateau is experiencing the most extensive soil erosion in China and is the top-priority area for implementation of the GGP. Based on rigorous scientific research, Loess Plateau croplands that have a slope greater than 15° are the target areas for the GGP and include an area of 2.52 million ha. Based on a per capita arable land demand of 1.5 mu (0.1 ha), the potential area for GGP implementation is limited to 2.36 million ha. However, 4.83 million ha of cropland have been converted to forest and grassland on the Loess Plateau between 2000 and 2008, which is double the limitation area for GGP. Although the GGP on the Loess Plateau has been met with a chorus of praise for its successes, which include increased vegetation cover, decreased soil erosion, and an improved eco-environment, the program has also resulted in socioeconomic problems, such as a substantial decrease in farmland and a critical grain shortage. Currently, balancing the population’s needs, grain supply needs, and environmental needs requires greater consideration. In recent years, Chinese scientists and government officials have noticed problems induced by the large-scale implementation of the GGP on the Loess Plateau. Shaanxi province, a province in northern China that includes 12.68% of the Loess Plateau area, developed a program titled “Plan for filling gullies to create farmland on the Loess Plateau” in 2010. The project aims to create 4.0 million ha of farmland in gully channels between 2011 and 2020, and the total investment has reached 30 billion Renminbi. Currently, the project is performing experiments in Yan’an city, the so-called Red Capital of China. Briefly, the approach of filling gullies to create farmland involves removing soil from the surrounding hills and using this material to fill gully channels. The flat fields created in the channels are used for cultivation and ultimately increase the farmland area within the Loess Plateau. Although the gully filling project has received support from the Chinese central government and recently Liu et al. analyzed its benefits, the project is controversial among Chinese geological, ecological, and environmental scientists. The focus of this controversy includes four aspects. First, the feasibility of the gully filling project has been questioned. The gullies of the Loess Plateau are generally deep, with depths of 100−300 m; filling soils in the deep channels and building dams to retain the sediments require huge amount of work, and therefore many geo-engineering scientists doubt the feasibility of the project construction. Second, it is possible that gully filling will lead to more significant disasters. The Loess Plateau is formed by Quaternary loessial dust deposits that are poorly structured and highly susceptible to erosion by water; thus, gully filling can increase the frequency of significant disasters, such as dam breaks and landslides. Third, gully filling projects require significant investments, and it is unclear whether the investment for filling gullies can be balanced by the income from farming the cropland created by the project. Fourth, it has been questioned whether gully filling will damage the environment and result in more extensive soil erosion; the filling of gullies requires the excavation of soil from the surrounding hills and will likely damage the vegetation and stability of hill slopes. I believe that gully filling to create farmland on the Loess Plateau is a double-edged sword. The Loess Plateau is now facing the dilemma of GGP expansion and grain shortage. The filling of gullies to create farmland might serve as an important measure to solve certain problems. However, gully filling is likely to create many types of environmental problems, such as geological disasters, ecosystem disruption, and soil erosion. At present, we must find a balance between the positive and negative impacts, eliminate the negative effects as much as possible, and evaluate case studies to improve the gully filling project.

Changes in some soil properties induced by re-conversion of cropland into grassland in the semiarid steppe zone of Inner Mongolia, China

“Grain for Green Program” (GGP), i.e., re-conversion of cropland into forest or grassland, initiated by Chinese government has a profound impact on mitigating environmental degradation. The objectives of this study were to assess the changes of some soil properties during the processes of re-conversion from cropland to grassland over time in the semiarid steppe region of north China. Two sites with different ages of re-conversion were selected for measurements of organic matter (SOM), total nitrogen (TN) and phosphorus (TP), bulk density (BD) and grain size distribution. Saturated hydraulic conductivity was determined by the constant hydraulic head method and unsaturated hydraulic conductivity by disc infiltrometer at tensions of 30, 60 and 150 mm. Soil water content was measured using the gravimetric method. Wetting front depths in the soil after rainfall were also recorded at the study sites. Natural grasslands had higher belowground biomass than re-converted grasslands. Re-converted grasslands had lower SOM and TN at depths of 0–20 cm and higher saturated hydraulic conductivity at depths of 0–10 cm than natural grassland. The natural grassland soils had higher soil water contents in the surface soil (0–20 cm) and lower soil water contents at deeper depths than re-converted grassland soils. Soil aggregate stability reached the natural steppe level 12 years after re-conversion. The recovery of soil properties after GGP appeared to be slow, and these properties did not return to natural grassland status before cultivation after 12 years of re-conversion.