Wolfberry Plantation Carbon Benefits On Saline Land In Jingtai, Gansu

Since 1880, anthropogenic activities have led to an increase in atmospheric concentration of CO2 from 280 ppm in the pre-industrial times to almost 400ppm at present, which is still increasing at a rate of 2.2 ppm yr1. This anthropogenic enrichment of GHGs in the atmosphere and the cumulative radiative forcing of all GHGs have led to an increase in the average global surface temperature of 0.8℃ since the late 19th century, which may increase by an additional 3-7 ℃ by 2100 under business as usual scenario. The warming rate since 1976 is 0.17℃/decade, which is in excess of the 0.1℃/decade limit beyond which the ecosystems cannot adjust. Consequently, the land-surface precipitation continues to increase at the rate of 0.5 to 1%/decade in much of the Northern Hemisphere especially in mid and high latitudes, and decrease in subtropical land areas at the rate of 0.3%/decade. Some effects of global warming include the reduction in the terrestrial and arctic glacier and ice cap, rise in sea level, decline in crop yield, reduction in ecosystem services, increase in frequency of extreme events especially drought, loss of in biodiversity (IPCC,2007b)because of pole-ward shift of principal biomes, and increase in global hunger and food insecurity etc.The largest global emission source comes from fossil fuel. Land use and land use change is the second greatest contributor to increasing, accounting for about 30% of total net emissions. The majority of these land use emissions are associated with deforestation and land conversion, mainly in the tropics. Global climate change is of special concern worldwide. There is a strong interest in stabilizing the atmospheric elevation of CO2 and other GHGs to mitigate the risk of global warming. At present there are basically two strategies for tackling the issue of climate change:mitigation of GHGs and adaptation to impacts.Terrestrial carbon sequestration is a win-win strategy, cost effective, and offering multiple benefits. Carbon sequestration through forestry and agriculture is a main component of terrestrial carbon sequestration and technical options are available in most eco-regions of the world. It plays an important role in mitigating negative effects of climate change and draws more and more attention globally. There is a strong interest in considering forestry and agriculture options as a part of some countries strategies to reduce GHG emissions.Cash trees, protective forests and agro-forestry are an integral part of China’s forestry as well as main land use types and play an important role in the global C cycle. The cash tree plantation makes up 1.15% of total land area, being an essential measure to improve ecology, restructure agriculture, and boost rural economy. It can augment farmers’income, enhance biomass C as well as soil C accumulation. However China has very limited efforts in research on distribution, budget, sequestration capacity of cash trees. This study focused on carbon benefits of wolfberry plantations with measurements and the CBP model, and analyzed factors constraining carbon sequestration with the DPSIR model and conducted cost benefit analysis for adoption or no-adoption of wolfberry planting. Main findings are as follows:1. Soil respiration rates of 5a,8a and barren saline land showed the same trend of single peak curves with a gentle changing process.5a reached the peak in July and the lowest ebb in January while 8a came to the highest point in August and the lowest point in January. Yet barren land had a more gentle changing annual respiration rate with the maximum value occurring in April and the minimum in January. In the non-growing season, the respiration rate of barren land was higher than those of 5a and 8a whereas they presented an order:5a> 8a> barren land in the growing season.2. Daily soil respirations of barren saline land,5a and 8a wolfberry plantations presented a single peak curve and double peak curve respectively in growing seasons. The daily respiration rates showed a order:5a>8a>saline land. Top layer soil moisture contents more significantly affected soil respiration than deep soil moisture. Soil respiration had a significant positive correlation with soil organic matter and N contents whereas total salt contents and EC of soil presented an obvious negative correlation with soil respiration.3. The soil organic carbon (SOC), active SOC, and non-active SOC contents of secondary saline land after planting wolfberry increased markedly; so did the activity of the C pool and index of the C pool activity. The C pool index and its management index also had a significant increase, implying improvements in soil quality.With the increase of wolfberry plantation age, the total SOC, non-active SOC, and C pool index were constantly increasing while the active SOC, C pool management index had a clear increase in early stage, and 5-8a later a decline which may relate to plant aging, pruning and inputs to soil. Human activity has considerable impacts to the SOC pool of wolfberry plantation.4. Wolfberry planting on the saline land increased above ground biomass C storage and root C as well. The biomass C of the wolfberry plantation was distributed mainly aboveground (over 65%). Wolfberry planting had raised C contents of all soil layers of the plantations with C stock contents in 1 m depth of 5,8 and 11 year old plantations being 36.4%,37.3%, and 43.3% higher than the saline land. Soil C pool was dominant in the ecosystem, accounting for over 90% o the total. C outputs of the system included fruit and pruning etc. The output of wolfberry fruits was dominated by total C, making up 92.3% of the total fruit mass while the export of pruning was largely C (97.8% of the total).5. Degraded soil has huge potential in C sequestration. Suitable cash tree planting will have multiple benefits, improving the soil and sequester C in the soil and the biomass. Results from the CBP model simulation show that wolfberry plantation and saline land both had positive impacts on C sequestration over a 10 year period of time. The C sequestration rate of barren saline land was 4.1 Mg CO2e yr1ha-1 while that of wolfberry plantation was 12.9 Mg CO2e yr-1ha-1, including 6.2 Mg CO2e yr-1ha-1 in soil C and 7.3 Mg CO2e yr-1ha-1 in biomass. The N2O emission rate caused by N fertilizer in Jingtai was 0.56 Mg CO2e yr-1ha-1. The carbon benefit from wolfberry planfing in Jingtai was-8.81Mg CO2e yr-1ha-1. Based on estimation by the CBP tool, the potential in C sequestration of wolfberry plantation was 215,004 Mg CO2e y4-1ha-1 in 2012. The potential for C fixation by wolfberry is stepping up with a constant increase in its planting area and in combination with other cash tree development, cash tree planting has a huge potential in carbon emission reductions.The DPSIR frame consists of driver, pressure, state, impact and response. In the context of wolfberry planting, to increase more income and bring more arable land under cultivation aremain drivers. Pressure comes from fertilization and irrigation. The wolfberry plantation is in the state of C sequestration. Social responses include policy incentives, improvement of current irrigation system, offering easy access to credit to farmers, institutionalizing training, enhancing technical extension, reforming current water pricing system, improving irrigation technology, manure crops, reinforcing professional association and cooperatives, and enhancing local processing capacity.CBA analysis showed that wolfberry planting had a net present value of US$ 31,310 ha-1, a 65% of internal rate of return and a 3.4 year recovery period for investment. Wolfberry planting reveals not only good economic return, but improving saline land use and sequestering C, a win-win strategy. It also has some external benefits. If current policy and market continue wolfberry planting would continuously offer economic and ecological wellbeing.