The effects of biochar derived from feedstock with different Si and Al concentration on soil N2O and CO2 emissions.

Desilicification and allitization is important characteristic of acidic soil. While decrease in soil silicon (Si) may generate Si limitation, the increase of aluminum (Al) will aggravate soil acidification. Biochar has been used in acid soil improvement, which could mitigate nitrous oxide (N2O) emissions and alter soil Si and Al concentration. However, the effect of biochar with different Si and Al concentration on greenhouse gas emissions remains unclear. We evaluated the effects of biochar derived from feedstock with different Si (moso bamboo leaves, BL; rice straw, RS) and Al (Camellia oleifera fruit shell, CFS; C. oleifera leaves, CL) concentration on greenhouse gas emissions and soil acidification. Microbial functional gene abundance associated with N2O emissions were measured to further explore the response of microbiological community. The results showed that BL, RS, CFS and CL significantly increased soil pH (by 19.2%, 16.7%, 18.7% and 24.9%, respectively), decreased soil exchangeable acid and exchangeable Al content, and reduced N2O emission rate of soil with nitrogen (N) (by 14.2%, 27.3%, 25.6% and 38.7%, respectively), which correlated with increase in soil nosZ abundance. BL, RS, CFS and CL increased soil nirK (by 325.6%, 66.7%, 155.8%, and 253.2%, respectively) and nosZ (by 198.6%, 174.1%, 72.2%, and 152.0%, respectively) abundance with N. Structural equation model showed that Si input via biochar application directly reduced N2O emissions, and soil acid-extractable Si is inversely proportional to N2O emission rate. In addition, Si input reduced carbon dioxide (CO2) emissions via indirect effects. Al input via biochar addition indirectly affected N2O and CO2 emissions through mainly indirect effects on other soil factors. In intensive management and production activities, Si-rich biochar can be considered instead of sole addition as fertilizer, which will be beneficial to the sustainable development of agricultural and forestry production in acid soil areas, and mitigation of global change.

Effects of Biofuel Crop Switchgrass (Panicum virgatum) Cultivation on Soil Carbon Sequestration and Greenhouse Gas Emissions: A Review.

Under the macroenvironmental background of global warming, all countries are working to limit climate change. Internationally, biofuel plants are considered to have great potential in carbon neutralization. Several countries have begun using biofuel crops as energy sources to neutralize carbon emissions. Switchgrass (Panicum virgatum) is considered a resource-efficient low-input crop that produces bioenergy. In this paper, we reviewed the effects of switchgrass cultivation on carbon sequestration and greenhouse gas (GHG) emissions. Moreover, the future application and research of switchgrass are discussed and prospected. Switchgrass has huge aboveground and underground biomass, manifesting its huge carbon sequestration potential. The net change of soil surface 30 cm soil organic carbon in 15 years is predicted to be 6.49 Mg ha-1, significantly higher than that of other crops. In addition, its net ecosystem CO2 exchange is about -485 to -118 g C m-2 yr-1, which greatly affects the annual CO2 flux of the cultivation environment. Nitrogen (N) fertilizer is the main source of N2O emission in the switchgrass field. Nitrogen addition increases the yield of switchgrass and also increases the N2O flux of switchgrass soil. It is necessary to formulate the most appropriate N fertilizer application strategy. CH4 emissions are also an important indicator of carbon debt. The effects of switchgrass cultivation on CH4 emissions may be significant but are often ignored. Future studies on GHG emissions by switchgrass should also focus on CH4. In conclusion, as a biofuel crop, switchgrass can well balance the effects of climate change. It is necessary to conduct studies of switchgrass globally with the long-term dimension of climate change effects.

Nitrogen and Biochar Addition Affected Plant Traits and Nitrous Oxide Emission From Cinnamomum camphora.

Atmospheric nitrous oxide (N2O) increase contributes substantially to global climate change due to its large global warming potential. Soil N2O emissions have been widely studied, but plants have so far been ignored, even though they are known as an important source of N2O. The specific objectives of this study are to (1) reveal the effects of nitrogen and biochar addition on plant functional traits and N2O emission of Cinnamomum camphora seedlings; (2) find out the possible leaf traits affecting plant N2O emissions. The effects of nitrogen and biochar on plant functional traits and N2O emissions from plants using C. camphora seedlings were investigated. Plant N2O emissions, growth, each organ biomass, each organ nutrient allocation, gas exchange parameters, and chlorophyll fluorescence parameters of C. camphora seedlings were measured. Further investigation of the relationships between plant N2O emission and leaf traits was performed by simple linear regression analysis, principal component analysis (PCA), and structural equation model (SEM). It was found that nitrogen addition profoundly increased cumulative plant N2O emissions (+109.25%), which contributed substantially to the atmosphere's N2O budget in forest ecosystems. Plant N2O emissions had a strong correlation to leaf traits (leaf TN, P n , G s , C i , Tr, WUE L , α, ETR max, I k , Fv/Fm, Y(II), and SPAD). Structural equation modelling revealed that leaf TN, leaf TP, P n , C i , Tr, WUE L , α, ETR max, and I k were key traits regulating the effects of plants on N2O emissions. These results provide a direction for understanding the mechanism of N2O emission from plants and provide a theoretical basis for formulating corresponding emission reduction schemes.

Effects of spent mushroom substrate-derived biochar on soil CO2 and N2O emissions depend on pyrolysis temperature.

Edible mushroom cultivation is an important industry in intensively managed forest understories. However, proper disposal of spent mushroom substrate (SMS) presents a challenge to its sustainable development. Biochar derived from SMS could be used to improve soil quality while providing a solution for SMS disposal. But SMS biochar pyrolyzed at different temperatures may alter carbon dioxide (CO2) and nitrous oxide (N2O) emissions associated with global warming, especially under the context of nitrogen (N) addition and warming. We conducted a factorial incubation study to examine greenhouse gas emissions and N transformations in moso bamboo forest soil amended with SMS-biochar (control vs. pyrolyzed at 300, 450 or 600 °C) in different N-addition (0 or 100 mg N kg-1 soil) and temperature (20, 25 or 30 °C) treatments. Pyrolysis temperature affected pH, C and N of SMS-biochars. N-transformations depended on the interaction of pyrolysis temperature, N-addition, and incubation temperature but were generally lower with 450 °C biochar addition. Soil N2O emissions increased with N-addition and they were more sensitive to incubation temperatures without biochar. Soil CO2 emissions increased with incubation temperature or biochar pyrolyzed at lower temperatures. Pyrolysis temperature might have regulated the effects of SMS-derived biochar on N2O emissions via changes in dissolved C, N, pH and associated changes in soil microbial community compositions. Because of the importance of sustainable development of this understory industry, amending soils with biochar produced at higher temperatures may be the best strategy for both the disposal of SMS and the mitigation of greenhouse gas emissions.