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Societal Impact Statement: Increasing atmospheric nitrogen (N) deposition represents a major global change factor, but its long‐term effect on tree growth and carbon (C) sequestration remains uncertain. Our manipulation experiment and meta‐analysis reveal that N deposition in temperate and boreal forests promoted tree growth and the allocation of more C into wood than into leaves in China and worldwide. Thus, N deposition may increase forest C sequestration through enhanced wood production and distribution of C into stable sinks. In the context of achieving "Carbon Neutrality," understanding how N deposition affect long‐term forest C sinks will help us with mitigation strategies under climate change. Summary: Increased nitrogen (N) deposition is driving many temperate and boreal forests in the Northern Hemisphere towards N saturation. However, it is uncertain how long‐term N deposition affects tree growth and carbon (C) allocation in these forests.To investigate this, we treated temperate larch and mixed forests in northeastern China with N additions for 8 years. In addition, we collected data from 25 N‐addition experiments in temperate and boreal forests worldwide to reveal the overall effects of N on tree growth and C allocation.Nitrogen additions significantly promoted total biomass increment by 24% in both study forests, with on average additional 8 kg C per kg N gain into woody biomass over the study period. Nitrogen additions increased the ratio of woody biomass increment to foliage litterfall production in the larch forest (by 34%). Literature data analysis also revealed greater N promotion on wood (24%) over foliage (9%) production. However, the positive effect on foliage diminished over time.These results combined imply that N deposition may promote tree growth in temperate and boreal regions and drive proportionally more photosynthate allocation into wood than leaves, thus may enhance forest C sequestration in the long run. [ABSTRACT FROM AUTHOR]

Greenwashing is an obstacle to the sustainable development of society, but the current governance of greenwashing is still a "common" governance, not a "collaborative" governance. Accordingly, this study focuses on the three stakeholders of greenwashing governance: company, media and government. Using a sample of listed companies that have published social responsibility reports from 2014 to 2018, this study analyzes the influence mechanism of media reports on greenwashing and discusses the moderating role of government regulation and mediating role of internal supervision. This study finds that internal supervision plays a hiding role in the process of media reports reducing greenwashing, but government regulation has a weakening effect on this hiding effect, showing a "common" governance. Simultaneously, this "common" governance is heterogeneous across time (i.e., corporate life cycle), space (i.e., spatial spillovers) and environment (i.e., the uncertainty of corporate external policies). However, when the cooperation between the government and the media is strengthened, the hiding behavior of the companies is suppressed and the performance of greenwashing governance is improved, so that "collaborative" governance is achieved. Against this backdrop, this study provides a macro‐to‐micro governance policy framework for corporate greenwashing from the four dimensions of strategy, systems, tools, and information to achieve "collaborative" governance. This study enriches the research on the corporate greenwashing governance and has practical implications for the government, media and other stakeholders. [ABSTRACT FROM AUTHOR]

Emissions of dinitrogen (N2) and nitrous oxide (N2O) from soil are important components of the global nitrogen cycle. Soil N2O emissions from terrestrial ecosystems have been well studied. However, patterns and mechanisms of N2 emissions remain unclear due to the technical difficulty in measuring N2 production. In this study, an in situ 15N labeling method was employed to determine soil N2 and N2O emission rates from the lower, middle, and upper slopes, which correspond to different moisture conditions, in a temperate forest in Northeast China. We found that N2 emissions varied from 85 to 3442 μg N m−2 h−1 across the slopes and were dominated by denitrification. The emissions of bulk N2O (22 to 258 μg N m−2 h−1) and denitrification-derived N2O (14 to 246 μg N m−2 h−1) were significantly lower than N2 emissions from their corresponding slope positions. Both N2 and N2O emissions significantly increased when soils become wetter. The ratios of N2O/(N2O + N2) were significantly higher at the upper and middle slopes (0.22 and 0.20, respectively) compared with those at the lower slope (0.08 ± 0.01). At the catchment scale, N2 accounted for 85% of the total gaseous N losses (N2O + N2). Our study shows that soil moisture drives the patterns of N2 and N2O emissions and field quantification of N2O/(N2O + N2) ratio should further consider the effect of slope position of forest ecosystems to estimate total soil gaseous N losses. [ABSTRACT FROM AUTHOR]

Background: Forest succession is an important ecological process and has been studied for more than a century. However, changes in nitrogen (N) availability during succession remain unclear as they may lead to either N saturation or N limitation. Here, we propose a conceptual model to illustrate changes in N availability during four stages of secondary succession using the natural abundance of 15N in plant leaves (foliar δ15N). We predicted that N availability would decline in the early stages of succession and then increase in late stages, coinciding with the changes in foliar δ15N, with the inflection point varying in different climate zones. Data on foliar δ15N from 16 succession sequences were synthesized to explore changes in N availability during forest succession. Results: The compiled data were consistent with the proposed conceptual model. Foliar δ15N in boreal and temperate forests decreased significantly in the first two stages of succession (estimated to last at least 66 years in temperate forests), at a rate of 0.18‰ and 0.38‰ per decade, respectively, and decreased slightly in tropical forests in the first 23 years. Foliar δ15N is projected to increase in later stages in all forests, which is supported by observations in both temperate and tropical forests. The inflection points of N availability when N limitation peaked during succession were different in different climate zones, implying different ecosystem N turnovers. Conclusions: Our study reconciles the controversies regarding changes in N availability during forest secondary succession. Our findings are also useful for predicting the recovery of N and carbon accumulation during succession. Nonetheless, studies on forest secondary succession using foliar δ15N have thus far been limited, and more research should be conducted to further verify the conceptual model proposed here. [ABSTRACT FROM AUTHOR]

Assessment of nitrogen (N) saturation of forests is critical to the evaluation of the manner in which ecosystems will respond to current and future global changes such as N deposition. However, quantifying N saturation remains a challenge. We developed a conceptual model of N saturation stages in forest ecosystems based on (1) a hypothetical relative rate of ammonification, nitrification, and denitrification, (2) concentrations of ammonium and nitrate in the soil, and (3) 15N enrichment pattern of bulk soil N, ammonium, and nitrate in the soil profile. We tested the hypotheses using data from forests located at five sites across eastern Asia. The fraction of nitrate in total inorganic N indicated that the sites represent an N saturation gradient with one boreal forest at stage 1 (least saturated), three temperate forests at stage 2, and one tropical forest at stage 3 (most saturated). The δ15N of bulk soil N increased from topsoil to subsoil more sharply at N‐limited sites than at the N‐rich sites along the N deposition gradient. We also found distinct 15N enrichment patterns of bulk soil N, ammonium, and nitrate in the soil profile across the study sites. At stage 1, nitrate was more 15N‐depleted than ammonium only in the organic soil horizon, indicating limited nitrification, while the 15N depletion of nitrate to ammonium was observed in the deeper mineral soil at stages 2 and 3. Furthermore, ammonium was more 15N‐depleted than bulk soil N at stages 1 and 2 but more 15N‐enriched than bulk soil N at stage 3. Our study suggests that soil profile patterns of δ15N of bulk soil N, ammonium, and nitrate provide information about the relative rates of mineralization, nitrification, and denitrification and thus can be an additional measure of N saturation of forest ecosystems across broad environmental gradients. [ABSTRACT FROM AUTHOR]

ABSTRACT. A 5-month simulated deposition study was conducted in Binghamton, NY to evaluate the impacts of traffic-related pollutants on soil nitrogen (N) transformations in a roadside environment. Nitrate, salt, and [...]

Summary: Conifers are considered to prefer to take up ammonium (NH4+) over nitrate (NO3−). However, this conclusion is mainly based on hydroponic experiments that separate roots from soils. It remains unclear to what extent mature conifers can use nitrate compared to ammonium under field conditions where both roots and soil microbes compete for nitrogen (N).We conducted an in situ whole mature tree nitrogen‐15 (15N) labeling experiment (15NH4+ vs 15NO3−) over 15 d to quantify ammonium and nitrate uptake and assimilation rates in four 40‐yr‐old monoculture coniferous plantations (Pinus koraiensis, Pinus sylvestris, Picea koraiensis and Larix olgensis, respectively).For the whole tree, 15NO3− contributed 39% to 90% to total 15N tracer uptake among four plantations during the study period. At day 3, the 15NO3− accounted for 77%, 64%, 62% and 59% by Larix olgensis, Pinus koraiensis, Pinus sylvestris and Picea koraiensis, respectively.Our study indicates that mature coniferous trees assimilated nitrate as efficiently as ammonium from soils even at low soil nitrate concentration, in contrast to the results from hydroponic experiments showing that ammonium uptake dominated over nitrate. This implies that mature conifers can adapt to increasing availability of nitrate in soil, for example, under the context of globalization of N deposition and global warming. [ABSTRACT FROM AUTHOR]