Research Highlights: Intensive nitrogen (N) application for agricultural purposes has substantially increased soil nitrous oxide (N₂O) emissions. Agricultural soil has great potential in the reduction of N₂O emissions, and applications of biochar and nitrification inhibitors may be useful for mitigating agricultural soil N₂O emissions. Background and Objectives: Camellia oleifera Abel. is an important woody oil plant in China. However, intensive N input in C. oleifera silviculture has increased the risk of soil N₂O emissions. As an important greenhouse gas, N₂O is characterized by a global warming potential at a 100-year scale that is 265 times that of carbon dioxide. Thus, mitigation of soil N₂O emissions, especially fertilized soils, will be crucial for reducing climate change. Materials and Methods: Here, we conducted an in situ study over 12 months to examine the effects of C. oleifera fruit shell-derived biochar and dicyandiamide (DCD) on soil N₂O emissions from a C. oleifera field with intensive N application. Results: A three-fold increase of cumulative soil N₂O emissions was observed following N application. Cumulative N₂O emissions from the field with N fertilization were reduced by 36% and 44% with biochar and DCD, respectively. While N₂O emissions were slightly deceased by biochar, the decrease was comparable to that by DCD. Conclusions: Results indicated that biochar may mitigate soil N₂O emissions substantially and similarly to DCD under specific conditions. This result should be examined by prolonged and multi-site studies before it can be generalized to broader scales.

Moso bamboo expansion is common across the world. The expansion of moso bamboo into adjacent forests altered plant and soil characteristics. While the community structure of soil fungi and bacteria plays an important role in maintaining the function of forest ecosystems, changes in microbial community compositions remain unclear, limiting our understanding of ecological process changes following moso bamboo expansion. To explore changes in the community structure of soil fungi and bacteria in Japanese cedar plantations experiencing expansion of moso bamboo, Illumina NovaSeq high-throughput sequencing technology was used to elucidate changes in soil microbial communities as well as alteration in litter and soil chemical characteristics. The results showed that moso bamboo expansion decreased content of soil organic carbon, total nitrogen, litter carbon, and the carbon to nitrogen ratio as well as the number of bacterial operational taxonomic units (OTUs) at the genus level, the α-diversity Simple index, and the abundance of Acidobacteria, Chloroflexi, and Gemmatimonadetes. Moso bamboo expansion also increased soil NH₄⁺-N, pH, while it decreased fungi OTUs at the phyla, class, order, family, and genus level. The expansion of moso bamboo into Japanese cedar substantially altered soil fungal and bacterial community structure, which might have implications for changes in the ecosystem element-cycling process. In the forest ecosystem and expansion management of moso bamboo, the types and different expansion stages of moso bamboo should be paid attention to, in the assessment of ecological effects and soil microbial structure.

Research Highlights: This study identifies the effect of nitrogen (N) and phosphorus (P) addition on stoichiometry correlations between understory plants and soil in subtropical Chinese fir plantations. Background and Objectives: Nitrogen and P are two nutrients limiting forest ecosystem production. To obtain more wood production, N and P are usually applied in plantation management. Changes in soil N and P will generally alter the stoichiometric characteristics of understory plants, which control carbon (C) and nutrient cycles between plants and soil. However, different correlations between plant and soil stoichiometry among functional groups of understory plants have not been investigated, which also impacted element cycling between plants and soil. Materials and Methods: Subtropical Chinese fir plantations were selected for N (100 kg ha⁻¹ year⁻¹) and P (50 kg ha⁻¹ year⁻¹) addition study. We collected fresh litter and the corresponding soil of four understory plants (Lophatherum gracile Brongn., Woodwardia japonica (L.f.) Sm., Dryopteris atrata (Kunze) Ching and Dicranopteris dichotoma (Thunb.) Berhn.) for study of C, N, and P stoichiometric ratios. Results: Nitrogen and P addition affected C, N, and P concentrations and stoichiometric ratios in litter and soil as well as correlations between litter and soil stoichiometric ratios. Understory plant species with different functional types impacted the correlations between plants and soil in C, N, and P stoichiometric ratios, especially correlations between litter C and soil C and N. Conclusions: Changes in soil N and P affect the stoichiometric ratios of understory plants. Functional groups impacted the correlation in C, N, and P stoichiometric ratios between plants and soil, indicating functional groups varied in their impacts on element cycling between plants and soil in plantations with exogenous nutrient addition, which should be considered in future management of plantations with intensive fertilization practice.

Research Highlights: This study examined the effect of mixing fine roots of Japanese cedar with moso bamboo on soil carbon dioxide (CO₂) emissions with nitrogen (N) addition treatment. Background and Objectives: Moso bamboo expansion into adjacent forests and N deposition are common in subtropical China. The effects of litter input on soil CO₂ emissions, especially fine root litter input, are crucial to evaluate contribution of moso bamboo expansion on greenhouse gas emissions. Materials and Methods: An in situ study over 12 months was conducted to examine mixing fine roots of Japanese cedar with moso bamboo on soil CO₂ emissions with simulated N deposition. Results: Fine root litter input of Japanese cedar and moso bamboo both impacted soil CO₂ emission rates, with mixed litter, positively impact soil CO₂ emission rate with N addition treatment. Moso bamboo fine root litter input decreased the sensitivity of soil CO₂ emission rate to soil temperature. Conclusions: The encroachment of moso bamboo into adjacent forests might benefit soil C sequestration under warming climate, which will also benefit the mitigation of global climate change.

Nitrogen (N) is a key factor for any ecosystem and has been found limited for biomass production. More N in forest ecosystem and their efficient utilization will contribute to the maximization in their growth, competition, and reproduction. Invasive plants capture and utilize more N than native plants and accelerate N cycles through altering the structure and community of soil microbes and the litter decomposition rates, under microclimate conditions, resulting in an increase of N availability. All these factors are promoting the invasiveness of plants and cause further ecological and economic damage and decline in native biodiversity. Plant invasions affect soil microbial community, soil physiochemical properties, and litter decomposition rates, promoting N cycle and releasing more nitrous oxide (N2O) into the atmosphere, further facilitating global warming, causing changes in the geographic ranges of some invasive species. Also, a better understanding of the mechanism, affecting factors, impacts, and control of the invasive species will lead to proper forest management. Proper and effective management will ensure the control of invasive species which includes invasive plant inventory, early deduction and rapid response, management plan and implication, and government support.