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China has become the largest carbon-emitting country in the world since 2007. To achieve national environmental goals by 2030, the carbon emissions per unit of gross domestic product (GDP) will need to fall to 60-65% of 2005 levels. Such a dramatic decrease presents a challenge for a nation in adjusting its energy source and usage, but via monitoring of reductions, greater understanding can be gained of how carbon emitters are responding to national goals. We analyzed the change in carbon emissions from China's fossil energy consumption from population, per capita GDP, energy efficiency improvements and energy structure using a Kaya identity model and Logarithmic Mean Divisia Index (LMDI) factor decomposition method from 2006 to 2018. Results suggest that trends in carbon emissions from 2006 to 2018 can be broken down into four periods: a rapid increase period during 2006-2011, a slowdown increase period during 2011-2014, a consecutive decline period during 2014-2016 and a rebound during 2017-2018. Trends in carbon emissions were greatly affected by per capita GDP and energy efficiency. While per capita GDP increased carbon emissions, energy efficiency had a countering effect on carbon emissions. Our results suggests that China's measures in the past decade to reduce carbon emissions (i.e. carrying out carbon emissions trading on a fixed basis, readjusting the economic structure, optimizing the energy structure, improving energy efficiency and increasing forest carbon sinks) have helped to reduce carbon emissions. However, China should continue to actively respond to climate change while striving to achieve of economic sustainable development and social progress.

To avoid competition with food crops, biofuel feedstocks may need to be produced on economically marginal lands where yields are limited and replacement of existing vegetation will reduce soil C, foregoing some CO2 emission savings. Therefore, our first goal was to determine whether biochar application to marginal lands could improve switchgrass yield while sequestering sufficient soil C to eliminate the negative impact of cultivation. Because it may be difficult to obtain large quantities of biochar, our second goal was to compare small, incremental and large, all-at-once biochar applications. Our third goal was to determine whether biochar had any negative effects on earthworms, mycorrhizal fungi, soil bacteria, soil fungi, and soil enzyme activity. We grew switchgrass at two sites with poorly drained soils and two sites with excessively drained soils. Irrespective of site, biochar significantly increased yield when we rototilled in the entire amount before planting but not when we applied it incrementally between crop rows using a chisel plow. Biochar increased soil C stocks, in some cases increasing it beyond that found in soils of intact marginal land vegetation. Nevertheless, mixing biochar with soil had little or no impact on earthworm activity, mycorrhizal colonization, soil bacterial and fungal communities, and soil enzyme activities. We conclude that biochar may be part of an effective strategy for producing switchgrass on marginal lands, but the choice of application method depends on the relative importance of several considerations including biochar availability, switchgrass yield, C sequestration, soil erosion, and ease of application.

Riparian wetlands are well known for providing the important ecosystem service of carbon storage. However, changes in land-use regimes surrounding riparian wetlands have been shown to result in alterations to the wetland plant community. These plant community changes have the potential to alter litter quality, decomposition rates, and ultimately the capacity of riparian wetlands to store carbon. To determine the effects of plant community shifts associated with disturbance on decomposition and carbon inputs, we performed a yearlong decomposition experiment using in situ herbaceous material, leaf litter, and control litter and examined biomass inputs in six headwater riparian wetlands in central Pennsylvania. Two sites were classified as Hemlock-Mixed Hardwood Palustrine Forest, two were classified as Broadleaf Palustrine Forest, and two were classified as Reed Canary Grass-Floodplain Grassland (Zimmerman et al. 2012). Plant matter with greater initial percent C, percent lignin, and lignin:N ratios decomposed more slowly while plant matter with greater initial cellulose decomposed more quickly. However, no significant differences were found between plant community types in decomposition rate or amount of carbon remaining at the end of the experiment, indicating that the differences in plant community type did not have a large impact on decomposition in riparian wetlands. This work has important implications for studies that examine the decomposition dynamics of a few select species, as they may not capture the decomposition dynamics of the plant community and thus extrapolating results from these studies to the larger ecosystem may be inappropriate.

Aggressive species competition by Typha latifolia in wetland systems on marl-derived soils may threaten the unique vegetation in these areas. We examined historic water and land use, soil chemistry, soil genesis, and topography in a wetland (Harewood Marsh) that is under encroachment by T. latifolia. An earthen road that bisects the wetland and active pastures in and around the wetland were also considered in the study due to their potential influence on wetland hydrology and nutrient inputs. Historic land uses and trends in surface water patterns were determined via aerial photography. In addition local landowners and city officials were contacted for information about historic water use in the area around the marsh. Soils were augered and sampled in seven locations in the wetland, and at each auger site, vegetation was described. Six wells were installed near the earthen road and weekly water depth measurements were taken from January 2002 to January 2003. In February 2002, 10 A-horizon soil samples (per transect) were taken from three 150-m transects that spanned areas with and without T. latifolia. Results indicate that T. latifolia encroachment is facilitated by a rising water table (the result of the termination of a local municipal water supply source) and N and P inputs, most likely from cattle grazing on the wetland. An increase in the numbers of rare plant species associated with marl wetland habitats appears to have also occurred and is believed partly due to current wetter conditions. Our study provides insight into the dynamics of T. latifolia encroachment in a unique marl wetland habitat and demonstrates how local factors controlling nutrient and hydrologic dynamics can have significant effects on changes in plant community composition.