The terrestrial ecosystem in China mitigates 21%-45% of the national contemporary fossil fuel CO2 emissions every year. Maintaining and strengthening the land carbon sink is essential for reaching China\'s target of carbon neutrality. However, this sink is subject to large uncertainties due to the joint impacts of climate change, air pollution, and human activities. Here, we explore the potential of strengthening land carbon sink in China through anthropogenic interventions, including forestation, ozone reduction, and litter removal, taking advantage of a well-validated dynamic vegetation model and meteorological forcings from 16 climate models. Without anthropogenic interventions, considering Shared Socioeconomic Pathways (SSP) scenarios, the land sink is projected to be 0.26-0.56 Pg C a-1 at 2060, to which climate change contributes 0.06-0.13 Pg C a-1 and CO2 fertilization contributes 0.08-0.44 Pg C a-1 with the stronger effects for higher emission scenarios. With anthropogenic interventions, under a close-to-neutral emission scenario (SSP1-2.6), the land sink becomes 0.47-0.57 Pg C a-1 at 2060, including the contributions of 0.12 Pg C a-1 by conservative forestation, 0.07 Pg C a-1 by ozone pollution control, and 0.06-0.16 Pg C a-1 by 20% litter removal over planted forest. This sink can mitigate 90%-110% of the residue anthropogenic carbon emissions in 2060, providing a solid foundation for the carbon neutrality in China.

The progressive increase of marine macro-litter on the bottom of the Mediterranean Sea is an urgent problem that needs accurate information and guidance to identify those areas most at risk of accumulation. In the absence of dedicated monitoring programs, an important source of opportunistic data is fishery-independent monitoring campaigns of demersal resources. These data have long been used but not yet extensively. In this paper, MEDiterranean International Trawl Survey (MEDITS) data was supplemented with 18 layers of information related to major environmental (e.g. depth, sea water and wind velocity, sea waves) and anthropogenic (e.g. river inputs, shipping lanes, urban areas and ports, fishing effort) forcings that influence seafloor macro-litter distribution. The Random Forest (RF), a machine learning approach, was applied to: i) model the distribution of several litter categories at a high spatial resolution (i.e. 1 km2); ii) identify major accumulation hot spots and their temporal trends. Results indicate that RF is a very effective approach to model the distribution of marine macro-litter and provides a consistent picture of the heterogeneous distribution of different macro-litter categories. The most critical situation in the study area was observed in the north-eastern part of the western basin. In addition, the combined analysis of weight and density data identified a tendency for lighter items to accumulate in areas (such as the northern part of the Tyrrhenian Sea) with more stagnant currents. This approach, based on georeferenced information widely available in public databases, seems a natural candidate to be applied in other basins as a support and complement tool to field monitoring activities and strategies for protection and remediation of the most impacted areas.

Litter plays a crucial role in phosphorus (P) cycling, and its role in forest ecosystems may vary with different treatments and forest types. In this study, we investigated soil P fraction responses to litter removal in different forest types and how forest conversion affects the acquisition pathway of bioavailable P through an in situ controlled litter experiment. The results showed that the soil P content increased with the conversion of primary to secondary forest, which may be mostly related to the differences in nutrients and species richness between the two forest types. In addition, the main source of bioavailable P in primary forests was active organic P, while mineral P was the main bioavailable P source in secondary forests. Moreover, the three-year litter removal treatment significantly decreased the primary forest soil P fraction content while significantly increasing the secondary forest bioavailable P content. The main driving factors of the soil P fraction are also different between the two forest types, with AP activity and SOC as the major factors in the primary forest and pH as the main factor in the secondary forest.

Litter comprises a major nutrient source when decomposed via soil microbes and functions as subtract that limits gas exchange between soil and atmosphere, thereby restricting methane (CH4) uptake in soils. However, the impact and inherent mechanism of litter and its decomposition on CH4 uptake in soils remains unknown in forest. Therefore, to declare the mechanisms of litter input and decomposition effect on the soil CH4 flux in forest, this study performed a litter-removal experiment in a tropical rainforest, and investigated the effects of litter input and decomposition on the CH4 flux among forest ecosystems through a literature review. Cumulative annual CH4 flux was -3.30 kg CH4-C ha-1 y-1. The litter layer decreased annual accumulated CH4 uptake by 8% which greater in the rainy season than the dry season in the tropical rainforest. Litter decomposition and the input of carbon and nitrogen in litter biomass reduced CH4 uptake significantly and the difference in CH4 flux between treatment with litter and without litter was negatively associated with N derived from litter input. Based on the literature review about litter effect on soil CH4 around world forests, the effect of litter dynamics on CH4 uptake was regulated by litter-derived nitrogen input and the amount soil inorganic nitrogen content. Our results suggest that nitrogen input via litter decomposition, which increased with temperature, caused a decline in CH4 uptake by forest soils, which could weaken the contribution of the forest in mitigating global warming.

While the importance of conservation mowing for mesic grasslands is generally accepted, its use for fens and fen grasslands interspersed within agricultural land is still controversial. Although fens may persist naturally, ongoing environmental changes increase productivity and accelerate succession. These processes can be mitigated through conservation management with appropriate settings. However, long-term management experiments are challenging and provide only locally valid results. Here, we analysed vegetation data (bryophytes and vascular plants) from seven management experiments (spanning 3-20 years) conducted in Central European poor, moderately-rich, and calcareous spring fens (Czech Republic, Slovakia). Two of these experiments examined the effects of restoration of abandoned fens, while five experiments examined changes in mowing regimes in managed fens (cessation, intensification, delay to autumn, and litter removal). Data were analysed using unidimensional and multidimensional methods separately for the initial, extended, and entire period. Mowing had a statistically significant effect on species composition except for the shortest (3-year) experiment. Litter removal did not compensate for mowing. Mowing twice or delayed mowing significantly affected the species composition of calcareous fens. In all cases, cessation of mowing significantly reduced the richness of species, especially those of conservation importance. In contrast, any mowing of abandoned fens increased species richness. The effects of mowing intensification or cessation on species richness and composition of a restored calcareous fen were evident in the first 2-3 years. Other effects were initially weak or nonsignificant but later became stronger, such as mowing delay and restoration removal of litter, which became significant only after nearly 20 years. We found that cessation or restoration of mowing usually triggers a rapid vegetation change, whereas it can take decades to detect the response caused by changes in mowing timing. Importantly, mowing can stabilise or even restore vegetation of fen ecosystems that have been weakened by their fragmentation in the temperate agricultural landscapes.

Marine litter is an ever-increasing problem that demands immediate reduction plans and mitigation actions that should act synergically to efficiently meet ambitious goals. Since the seafloor has been recognized as the major sink for marine debris, the study of litter accumulation dynamics represent a fundamental tool to evaluate possible removal actions. We analysed a 7 years (2013-2019) standardized data series collected along Sardinian fishing grounds through MEDiterranean International Trawl Survey, for which estimates of density and weight of seafloor macro-litter were calculated for over 707 hauls. Results show the absence of any temporal trend in seafloor macro-litter density and weight, but rather indicate a spatial and bathymetric segregation of different litter categories. Our data showed how different sources and physical features of macro-litter items (i.e., plastic and fishing gear, rubber, glass, metals, and cloth) led to spatially segregated accumulation hotspots. We also point out here how the identification of seafloor macro-litter hotspots using aggregated data that include plastic items could obscure the identification of other segregated but yet relevant hotspots of other macro-litter categories accumulated in the marine environment. These hotspots often occurred at shallower depths and closer to coastlines, thus representing potential spots where eventual future litter removal action could be prioritized.

Marine litter is an ever-increasing problem that demands immediate reduction plans and mitigation actions that should act synergically to efficiently meet ambitious goals. Since the seafloor has been recognized as the major sink for marine debris, the study of litter accumulation dynamics represents a fundamental tool to evaluate future removal actions. We analysed a 7 years (2013-2019) standardized data series collected along Sardinian fishing grounds through MEDiterranean International Trawl Survey, for which estimates of density and weight of seafloor macro-litter were calculated over 707 hauls. Results show the absence of any temporal trend in seafloor macro-litter density and weight, but rather indicate a spatial and bathymetric segregation of different litter categories. Our data showed how different sources and physical features of macro-litter items (i.e., plastic and fishing gears, rubber, glass, metal and textile) led to spatially segregated accumulation hotspots. These hotspots often occurred at shallower depths and closer to coastlines, representing spots where future litter removal action could be prioritized. We also point out here how the identification of seafloor macro-litter hotspots using aggregated data that include plastic items could indeed hide the identification of hotspots of other less abundant but yet detrimental macro-litter categories accumulated in the marine environment.

Question: Litter (dead leaves or stems) affects production by conserving soil moisture. However, that role is not clear for grasslands where most precipitation falls during the growing season when the demand for water is high. Our question was: Does litter affect forage production in such an environment? Location: Typical steppe, Inner Mongolia. Methods: We examined the role of plant litter in two experiments where litter was either removed or added in a protected or heavily grazed site, respectively, in autumn and in spring in a split plot design. The treatments (control, moderate and heavy litter application) were applied once in five replications but repeated at new locations in each of 3 years. This was done to examine only the direct effect of litter on annual net primary production and selected plant characteristics and not potential secondary effects. We also measured soil moisture and soil temperature. Results: Removing litter caused a reduction in the amount of grass (Leymus chinensis) that was produced, but litter addition caused an inconsistent effect among years, with moderate applications producing the most positive effects. Litter removal resulted in shorter and less dense plants of L. chinensis and Carex duriuscula, while heavy litter addition in autumn reduced plant height of both Cleistogenes squarrosa and C. duriuscula. Conclusions: Litter was effective for enhancing soil moisture status and reducing soil heat units in the typical steppe of Inner Mongolia. Therefore, litter mass may serve as an index of grassland health in such environments.

We conducted detritus input and removal treatment (DIRT) to examine the effects of shifting above- and belowground carbon (C) inputs on soil microbial biomass, community composition and function in subtropical Pinus elliottii, Eucalyptus urophylla × Eucalyptus grandis, Acacia aulacocarpa and Casuarina equisetifolia coastal sandy plain forests, and the treatments included: root trenching, litter removal and control. Up to September 2015, one year after the experiment began, we collected the 0-10 cm soil samples from each plot. Phospholipid fatty acid (PLFA) analysis was used to characterize the microbial community composition, and micro-hole enzymatic detection technology was utilized to determine the activity of six kinds of soil enzymes. Results showed that changes in microbial biomass induced by the C input manipulations differed among tree species, and mainly affected by litter and root qualily. In E. urophylla × E. grandis stands, root trenching significantly decreased the contents of total PLFAs, Gram-positive bacteria, Gram-negative bacteria, fungi and actinomycetes by 31%, 30%, 32%, 36% and 26%, respectively. Litter removal reduced the contents of Gram-positive bacteria, fungi and actinomycetes by 24%, 27% and 24%, respectively. However, C input manipulations had no significant effect on soil microbial biomassunder other three plantations. According to the effect of C input manipulations on soil microbial community structure, litter and root exclusion decreased fungi abundance and increased actinomycetes abundance. Different treatments under different plantations resulted in various soil enzyme activities. Litter removal significantly decreased the activities of cellobiohydrolase, β-glucosidase, acid phosphatase and N-acetyl-β-d-glucosaminidase of P. elliottii, A. aulacocarpa and C. equisetifolia, root exclusion only decreased and increased the activities of β-glucosidase in P. elliottii and A. aulacocarpa forest soils, respectively. Litter removal also decreased the activities of polyphenol oxidase (PPO) and peroxidase (PER) in P. elliottii and C. equisetifolia forest soils, while root trenching had no significant effect on the activities of PPO and PER under all plantations. The properties of litter and root were the important factors in determining the soil microbial community and enzyme activity, and the change of soil microenvironment, such as temperature and moisture, caused by C input manipulations was also the important driver for the change of soil microbial property.
通过在亚热带滨海防护林湿地松、尾巨桉、纹荚相思和木麻黄人工林中设置去除凋落物、去除根系和对照处理,分析改变地上、地下碳输入对沙地人工林土壤微生物生物量、群落结构和功能的影响.2015年9月,在处理设置一年后采集各处理样方0～10 cm土壤样品,分别采用磷脂脂肪酸分析方法和微孔板酶检测技术对土壤样品的微生物群落组成和6种酶活性进行测定.结果表明: 碳输入处理对土壤微生物生物量的影响因树种而异,并主要取决于凋落物和根系的质量.在尾巨桉林中,去除根系使得脂肪酸总量、革兰氏阳性细菌、革兰氏阴性细菌、真菌和放线菌生物量分别显著减少了31%、30%、32%、36%和26%,去除凋落物使得革兰氏阳性细菌、真菌和放线菌生物量显著减少了24%、27%和24%,而其他树种处理对微生物生物量无显著影响.碳输入处理对土壤微生物群落结构的影响主要表现为真菌丰度下降而放线菌丰度上升.不同树种的土壤酶活性对处理的响应表现不一致:湿地松、纹荚相思和木麻黄林分去除凋落物显著降低土壤中纤维素水解酶、β-葡萄糖苷酶、酸性磷酸酶和乙酰氨基葡萄糖苷酶活性,去除根系仅分别降低和提高了湿地松和纹荚相思林β-葡萄糖苷酶的活性;湿地松、木麻黄人工林去除凋落物显著降低了多酚氧化酶和过氧化物酶活性;去除根系对所有树种土壤氧化酶活性影响不显著.不同树种的凋落物、根系特性是影响土壤微生物群落组成和酶活性的重要因子,碳输入处理造成的土壤温度、水分等微环境的改变也是土壤微生物性质变化的重要驱动力.

Owing to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident a vast amount of radiocesium was released polluting the land. Afterwards, a variety of decontamination practices has been done, reducing the ambient dose rates. In this study we evaluated the effectiveness of eight forest decontamination practices by means of monitoring the radiocesium (137Cs) concentration in soil and leaf samples, and the daily discharge rates in ten plots during 27 months (May 2013-July 2015). A forest plantation located 16 km southwest to the FDNPP and within the exclusion area was selected. Radiocesium concentrations were analysed using a germanium gamma ray detector. The differences in radiocesium activities between the different plots were statistically significant (p < 0.05) and four homogeneous groups were distinguished. Tree thinning and litter removal greatly reduced the radioactivity and the two plots devoted to these practices presented the highest discharge rates of 137Cs (Th + LR; 350-380 Bq/m2 day), followed by the two Th plots (163-174 Bq/m2 day). The clearcutting with LR and the LR plots (104 and 92 Bq/m2 day) also had higher rates than those rates in the control plots (51 Bq/m2 day). We only observed low rates in the two plots with matting (19-25 Bq/m2 day). The temporal variability was explained by (i) the different rainfall depths registered during the measurement intervals (accumulated precipitation from 14 to 361 mm); and (ii) the fluctuations of the total surface coverage. The decrease trend in radiocesium concentration was high in 2013, moderate in 2014 and low in 2015 owing to the vegetation recovery after the countermeasures, thus reducing the possibility of the second pollution of the neighbouring areas. The average proportions of contribution of 137Cs discharge by soil and leaf fraction were 96.6% and 3.4%.