This paper introduces the second phase of the Grain for Green. The first phase ran from 1999 to 2014, and the second phase started in 2015. The second phase of the GfG (GfG/2) addresses some problems ...of the first phase (GfG/1), in particular the lack of income for the farmers, as well as some changes to the rural areas, in particular the small number of remaining farmers. The paper describes how the GfG/2 (unlike the GfG/1) encourages farmers to organize themselves in cooperatives, or work with investors, and grow fruit trees to generate sustainable incomes. The paper also describes the constraints that prevent the smooth implementation of the GfG/2, in particular the insufficient financial support, the fact that some of the land that should be converted is “essential farmland”, and the small and scattered pieces of farmland. The paper argues that in spite of this, the program is likely to succeed, and help farmers generate sustainable incomes. The paper is based in four periods of fieldwork in Chongqing Municipality, Shaanxi Province, and Yunnan Province and extensive interviews of farmers and government officers.
Afforestation contributes to soil organic carbon (SOC) sequestration and the restoration of degraded soil. However, the changes in SOC stock following afforestation on sloping land are poorly ...understood. Here we conduct a quantitative review that synthesizes 239 observations from 31 studies to evaluate the effects of slope gradients on the changes in SOC stock in three soil layers (0–20 cm, 20–40 cm and 40–60 cm) following afforestation, considering previous land cover (cropland and grassland) and tree type (broadleaf and conifer). In the topsoil layer, slope gradient has a significant effect on the changes in SOC stock: slope gradient positively relates to SOC stock change and significantly predicts the SOC stock change after controlling for temperature, precipitation, stand age, and initial SOC stock. Soil gradient explains 12.5% of the variance. We find a significant decrease in SOC stock after the afforestation of gentle slopes with a gradient lower than 10% but a significant increase in SOC stock on slopes with a gradient higher than 30%. Afforestation on sloping cropland results in an increase in SOC stock, especially in the upper soil, while afforestation on grassland results in an increase in SOC stocks only on very steep slopes (gradient >60%). Tree type has a limited effect on changes in SOC after afforestation on sloping land. However, conifers show a greater SOC sequestration potential in deeper soils and on steep slopes with a gradient higher than 60%, while broadleaf trees sequester more SOC in topsoil and on slopes with a gradient of 30–60%. The present study suggests that to increase SOC sequestration, priority should be given to afforestation with conifers on steep cropland.
•Afforestation of steep slopes sequesters more SOC than afforestation of gentle slopes.•Afforestation on sloping cropland significantly increases SOC stock in upper soil.•Afforestation on sloping grassland decreases SOC stock except for very steep slopes.•Tree type has a limited effect on changes in SOC after afforestation on sloping land.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Aims
With the wide application of
7
Be (Beryllium-7) in soil erosion investigations, retention and interception of
7
Be by vegetation plays an important role in documenting soil
7
Be redistribution, ...with a large impact on the interpretation of
7
Be measurements. However, the dynamic and temporal changes in plants and the relationship with soil
7
Be concentration remain unclear, and the significance of dead plants in
7
Be interception is under-researched.
Methods
The samples of single plants (6 different species), compositive plants (including living and dead plants), along with soil reference on the Loess Plateau were collected individually to analyze the variations of
7
Be concentration during the growth period from 2010 to 2012.
Results
The accumulation of
7
Be per mass is significantly higher in leaves than stems. The
7
Be activity per mass and per area in living plants with seasonal trends ranged from 173.9 to 703.1 Bq kg
–1
and 21.5 to 190.1 Bq m
–2
, respectively, and in dead plants ranged from 381.8 to 964.5 Bq kg
–1
and 30.4 to 285.7 Bq m
–2
. Precipitation accounted for the largest contribution to the accumulation of
7
Be in plants, followed by plant growth, species and parts. Plants accounted for
7
Be interception on slope up to 66% (living plants accounted for 7% ~ 31% and dead plants accounted for 6% ~ 44%). The interception of living plants is low at first, then increases with the accumulation of rainfall and biomass together.
Conclusions
Our results highlight that
7
Be in plants (especially for the dead plants) is of great significance for
7
Be in soil on the slope, and is controlled by precipitation, growth status and plant characteristics. The reference information obtained in this work will contribute to improving the accuracy of
7
Be tracing technology, and broadening its scope.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This study identifies historical extreme events and analyzes their impacts on social vulnerability, stability, and resilience in ancient China. We reconstructed extreme event sequences, simulated ...social resilience response using our proposed Cascade Catastrophe-Resilience Dynamic Model, and discussed interaction of social vulnerability and stability. We found the following conclusions. First, historical extreme events had cyclic and periodic fluctuations, and usually led to cascade disasters. Cascade disasters enhanced risk and greatly reduced societal stability, while three types of disaster chains were observed: climatic extremes (flood/drought)-famines-wars (uprising/invasions)-epidemic plagues; climatic extremes (flood/drought)-famines -migrations; and droughts-locust plagues-famines. A climate extreme-earthquake chain was also recorded although the mechanism remains unknown. Second, extreme events were synchronous with dynastic changes, although strong social resilience enhanced the opportunity for dynastic survival and modified the stochastic magnitude–frequency relationship between extreme events and social vulnerability. The high frequency of extreme events is consistent with high hazard indices, declining population, high levels of social vulnerability, and low levels of social stability and resilience. However, the strong correlation between high levels of social vulnerability and high frequency of extreme events occurred at the end of dynasties but not when dynasties were thriving. Third, quick response to disasters, efficient disaster relief systems, and sufficient food supplies were essential parts of social resilience to disasters. Extreme events play important roles in shaping agricultural production, and thus food supply. Population fluctuation and migration, economic center shifts, and social and economic structure changes contributed to cascade disasters, which often led to societal instability throughout Chinese history.
Full text
Available for:
CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
China is the most populated country in the world, but has relatively little fertile land, and even less water. Maintaining the quality of its agricultural land is of paramount importance if China ...wants to feed its very large and growing population. Yet, China is one of the countries with the largest amount of polluted soil. This paper looks at the causes and distribution of soil pollution in China. It first looks at the amount of organic and inorganic soil pollutants and their geographic distribution. It then looks at the causes of soil pollution, making the distinction between agricultural activities, industrial activities, and urbanization. Pollution from agricultural activities stems primarily from the excessive amounts of pesticides and fertilizers used on farmland, and is mainly located in the south, where most of the food is produced. Pollution from industrial activities is due to airborne industrial pollutants that fall on to the land, and is mainly located in the west of the country, where most manufacturing activities take place. Pollution from urbanization is mainly due to the very large amount of solid, liquid and gaseous waste generated in a small area with insufficient treatment facilities, and exhaust fumes from vehicles, and is located around the largest cities, or roads. The result is that one fifth of China’s farmland is polluted, and an area the size of Taiwan is so polluted that farming should not be allowed there at all.
Aims
Any grouping of tree species concerned with SOC sequestration should include trees that are as homogeneous as possible in their carbon sequestration. We propose a classification of tree species ...into deciduous broadleaf, evergreen broadleaf, deciduous conifer and evergreen conifer and assess the validity of such classification.
Methods
We conducted a quantitative review of 264 observations from 90 papers. One-way analysis of variance and hierarchical multiple regression were performed to test the homogeneity within the tree types and the extent to which the tree classifications could affect the SOC stock change, after controlling for temperature, precipitation, stand age, initial SOC stock and previous land use.
Results
There is less variation in the SOC sequestration rates of tree types if they are grouped as deciduous broadleaf, evergreen broadleaf and evergreen conifer rather than evergreen and deciduous, or broadleaf and conifer. Evergreen broadleaf accumulates SOC at the fastest rate (0.73 Mg ha
−1
yr
−1
), compared to deciduous broadleaf (0.42 Mg ha
−1
yr
−1
) and evergreen conifer (0.48 Mg ha
−1
yr
−1
). The proposed classification may help researchers to better estimate the changes in SOC stocks after afforestation with various tree species, when direct measurements are not available.
Conclusions
Our proposed classification of tree species is more accurate than the more commonly used groups of deciduous and evergreen or broadleaf and conifers.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Key message
Different tree species have dissimilar capacities to sequester soil organic carbon (SOC). Deciduous broadleaved trees show the most stable increase in SOC stock after afforestation than ...other tree species, while sempervirent conifer trees show the lowest rate of SOC stock change. Sempervirent broadleaved trees show the greatest increase in SOC stock 20 years after afforestation.
Context
The rate at which soil organic carbon (SOC) stock changes after afforestation varies considerably with the tree species. A better understanding of the role of tree species in SOC change dynamic is needed to evaluate the SOC sequestration potential of afforestation programs.
Aims
The aim of this paper is to identify the dissimilar rates at which different tree species sequester SOC, following afforestation.
Methods
We complete a meta-analysis with 544 data points from 261 sites in 90 papers. We group tree species into decidious broadleved, sempervirent broadleaved and sempervirent conifer. We use standardization and/or extrapolation methods to standardize soil depths. Statistical analysis test the main effects of tree species and their interactions with previous land use and plantation age on SOC stock change after afforestation.
Results
Deciduous broadleaved trees show a stable increase in SOC stock, and are especially suited for afforestation of grassland or soils with high initial SOC. Sempervirent broadleaved afforestation results in loss of SOC stock in young stands, but greater SOC stock in mature stands. Sempervirent conifer trees show the lowest rate of SOC stock change, but are suitable for nutrient-poor soil.
Conclusion
The results emphasize the importance of considering tree species when estimating SOC stock change, in particular when carbon sequestration is an objective of afforestation programs.
Full text
Available for:
FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Quantifying the relative influences of anthropogenic activities and climate change on soil erosion and deposition during the Holocene, when both forces have been interacting is a complex problem. ...Analysis of long-term patterns in soil erosion and lake deposition in a basin can provide the basis for untangling the complexities of climate and anthropogenic forcings. In this paper, sedimentary sequences from Xingyun Lake are compared with simulated soil erosion rates in the basin to explore the relationship between river basin soil erosion and lake deposition during the Holocene in Yunnan, China. Modern soil erosion rates are calculated using RUSLE, while Holocene soil erosion rates are estimated using modern rates with reconstructed precipitation and vegetation cover sequences. Through this investigation, we found the following results. First, Holocene vegetation in the lake basin was mainly affected by climate change, and the vegetation experienced the same pattern of changes as the climate. Soil erosion and lake deposition rates, along with changes to vegetation cover, were synchronous with precipitation trends during the Holocene. Second, soil erosion and lake deposition have been exacerbated by human activities, such as deforestation and land reclamation in the Xingyun Lake basin. Finally, this study provides new insights into the effects by anthropogenic impacts and climate forcing on the processes of soil erosion and lake deposition on the millennium scale.
Full text
Available for:
NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
•A 3D hydrodynamic model of Lake Fuxian was established by EFDC.•The stratification and thermocline of the deep lake were mainly investigated in this study.•Thermocline spatiotemporal features are ...intensely affected by the meteorological conditions and hydrodynamic process.•Horizontal divergence and convergence caused by vertical circulation lead to inhomogeneity of the thermocline.
This study aims to provide a comprehensive numerical solution and quantitative analysis of the thermal stratification and circulation in Fuxian Lake, the largest freshwater deep lake in China, utilizing a high-fidelity Environmental Fluid Dynamics Code (EFDC) to build a three-dimensional hydrodynamic model. Simulation results reveal that meteorological conditions and hydrodynamic processes notably influence the spatiotemporal characteristics of the thermocline, with wind and temperature disparities primarily impacting water flow. Maximum water temperature (24.3 °C) and thermocline intensity (0.31 °C/m) typically occur in September. Vertical circulation, driven by wind-induced horizontal divergence and convergence of lake currents, often induces uneven vertical movements, leading to thermocline irregularities. This study also assesses the sensitivity of Fuxian Lake to temperature changes, showcasing the efficacy of EFDC model in accurately reproducing observed spatiotemporal variations. This research not only establishes a foundation for integrating the EFDC model with water quality models but also presents an effective approach for studying hydrodynamics and thermal stratification processes in other deep-water lakes, thereby facilitating lake management and ecological restoration endeavors.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Forests have a huge potential to produce timber and sequester carbon in a joint process. Thus, afforestation projects have been widely undertaken across countries to achieve poverty alleviation and ...environment protection goals, specifically in reducing atmospheric carbon dioxide. Our study determines the optimal rotation periods of afforestation projects with three different tree species (Chinese fir, Eucalyptus, and Poplar) in various Chinese regions. Applying a modified Hartman rotation model, our results show that the optimal rotation period increases for all examined species, when considering the joint production of timber and carbon sequestration. However, they also indicate that carbon accounting regimes have a significant impact on the optimum rotation as well as on the revenue calculations. We distinguish between temporary (tCER) and long-term (lCER) Certified Emission Reductions. The present value of lCER revenues is three to four times higher than those generated by tCER for the same plantation in the initial 5 to 10 years. In contrast, when the project period extends to 30 years, the present value of lCER revenues is at least two times lower than the present value of tCERs. Therefore, forest managers have an incentive to apply tCER accounting to finance slow-growing plantations, and lCER for fast-growing ones. We conduct a sensitivity analysis with respect to changes in discount rates and carbon prices. While the optimal decision for Chinese fir is highly sensitive to changes in both variables under tCER accounting, the results concerning Eucalyptus are most sensitive under the lCER accounting regime. In contrast, carbon revenues have a minimal impact on the optimal rotation of Poplar plantations, no matter which regime is applied. Our findings can contribute to the efficient and sustainable management of carbon sequestration projects, while the methodology can also be applied to other regions in the developing world.
•Carbon accounting regimes have a significant impact on the optimum rotation period.•Managers have an incentive to apply tCER accounting to finance slow-growing trees.•Managers have an incentive to apply lCER accounting to finance fast-growing trees.•Sensitivity analysis of the optimal decision differs with carbon accounting regimes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
PDF
