Management Strategies and Their Evaluation for Carbon Sequestration in Cropland

In order to deal with the global change and to reduce emission of greenhouse gas, a number of countries have strengthened studies on carbon sequestration in cropland. Carbon sequestration in cropland is not only an important component for the global carbon stock, but also is the most active part to sequestrate the carbon in soil from atmosphere. In this sense, it is of necessity and significance to strengthen the study on management of carbon sequestration in cropland. Based on the main factors affecting carbon cycle in agro-ecosystems, this paper summarizes the relevant management measures to strengthen the capacity of reducing emission of carbon and increasing the carbon sequestration in cropland, and evaluates the effects of these measures after being implemented at a regional extent.

Water-use efficiency in response to simulated increasing precipitation in a temperate desert ecosystem of Xinjiang, China

Water-use efficiency（WUE） is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes： increasing by 33.9% in the wet year（i.e., the normal precipitation years）and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.

Assessment of carbon sink potential and methane reduction scenarios of marine macroalgae(Gracilaria)cultivation

Marine macroalgae cultivation is an important part of the effort to address climate change through carbon sinks.Gracilaria,especially Gracilaria lemaneiformis and Gracilaria lichenoides are the major macroalgae cultivated in China.This study proposes a method to assess the net carbon sink of marine macroalgae(Gracilaria)cultivation.First,the net carbon sink of Gracilaria cultivation in China is calculated based on the yield of annual cultivated Gracilaria recorded in China Fishery Statistical Yearbook from 2011 to 2020.Next,we predict the net carbon sink trend of Gracilaria cultivation from 2021 to 2030 using the autoregressive integrated moving average model(ARIMA).Finally,the potential carbon sink increase and methane reduction related to Gracilaria cultivation in China is explored through a scenario analysis.We find that the net carbon sink of Gracilaria cultivation in China was about 32.1-92.4 kilotons per year from 2011 to 2020,and shows a great annual growth trend.Moreover,the predicted net carbon sink of Gracilaria cultivation would increase to 77.8-191.4 kilotons per year from 2021 to2030,thereby could contribute considerably in the achievement of China's carbon peak goal.Under a scenario of producing ruminant green feed with additional Gracilaria cultivation,each ton of macroalgae is predicted to reduce carbon emission(i.e.,methane)by 0.33-0.68 tons.Thus,marine macroalgae cultivation might form a synergistic chain of"carbon sink increase-water purification-economy-methane reduction".This study proposes a synergistic new model that operates through marine macroalgae cultivation,economic aquaculture,and green feed production.

Processes of coastal ecosystem carbon sequestration and approaches for increasing carbon sink

The oceans are the largest carbon pools on Earth, and play the role of a "buffer" in climate change. Blue carbon, the carbon(mainly organic carbon) captured by marine ecosystems, is one of the important mechanisms of marine carbon storage.Blue carbon was initially recognized only in the form of visible coastal plant carbon sequestration. In fact, microorganisms(phytoplankton, bacteria, archaea, viruses, and protozoa), which did not receive much attention in the past, account for more than 90% of the total marine biomass and are the main contributors to blue carbon. Chinese coastal seas, equivalent to 1/3 of China's total land area, have a huge carbon sink potential needing urgently research and development. In this paper, we focus on the processes and mechanisms of coastal ocean's carbon sequestration and the approaches for increasing that sequestration. We discuss the structures of coastal ecosystems, the processes of carbon cycle, and the mechanisms of carbon sequestration. Using the evolution of coastal ocean's carbon sinks in sedimentary records over geologic times, we also discuss the possible effects of natural processes and anthropogenic activities on marine carbon sinks. Finally, we discuss the prospect of using carbon sequestration engineering for increasing coastal ocean's carbon storage capacity.