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Nitrogen (N) saturation occurs when N inputs exceed the total N demand by plants and microbial organisms in forest ecosystems. Long-term observations, N deposition gradient investigations, N addition experiments, and model simulations can provide insights in thresholds for N saturation using various indicators. Here we give an overview of N saturation indicators and their thresholds for soil, trees (growth and nitrogen nutrition) and stream water as well as related N deposition thresholds for forest N saturation. A synthesis of literature suggests that in boreal forests, the threshold of N deposition for N saturation was 5-10kgNha−1 yr−1 based on the occurrence of N leaching. In temperate forests, the threshold of N deposition for N saturation was estimated to be 5-46kgNha−1 yr−1, 5-30kgNha−1 yr−1 and 8-15kgNha−1 yr−1 based on soil, tree and stream water indicators, respectively. In subtropical coniferous forests, the thresholds of N deposition for N saturation based on soil, tree and stream water indicators ranged from 30 to 70kgNha−1 yr−1, 26 to 36kgNha−1 yr−1, and 7 to 10kgNha−1 yr−1, respectively. However, the thresholds of N deposition for N saturation were less well quantified in other forest ecosystems. Furthermore, we briefly reviewed critical loads of N deposition for biodiversity, a forewarning threshold associated with the first appearance of negative effects. Critical loads of N deposition were generally lower than the thresholds for N saturation. Empirical critical loads based on responses of plant species diversity, showed higher values in temperate forests (10-15kgNha−1 yr−1) than in boreal forests (5-10kgNha−1 yr−1). However, estimates of empirical critical N loads for subtropical and tropical forests are lacking in literature. Future research efforts are needed to better evaluate the saturation thresholds of N deposition and critical N loads in various forest ecosystems to inform policies for N emission reduction and forest management.

Meng Zhang,1,* Wenyi Lu,2,* Danni Xie,1 Jiaxi Wang,1 Xia Xiao,2 Yedi Pu,2 Juanxia Meng,2 Hairong Lyu,2 Mingfeng Zhao2 1First Center Clinic College of Tianjin Medical University, Tianjin, 300192, People’s Republic of China; 2Department of Hematology, Tianjin First Central Hospital, Tianjin, 300192, People’s Republic of China*These authors contributed equally to this workCorrespondence: Mingfeng Zhao; Hairong Lyu, Department of Hematology, Tianjin First Central Hospital, Tianjin, 300192, People’s Republic of China, Email mingfengzhao@sina.com; 18802235939@163.comBackground: Metagenomic next-generation sequencing (mNGS) is a fast, sensitive and accurate diagnostic method for pathogens detection. However, reports on the application of mNGS in mucormycosis remain scarce.Methods: From January 2019 to December 2021, we recruited 13 patients with hematological malignancies who were suspected of mucormycosis and completed mNGS in D20. Then we retrospectively analyze the clinical data, diagnosis, therapeutic process, and outcomes. In order to evaluate the diagnostic value of mNGS in hematological malignancies patients with suspected mucormycosis.Results: All patients had high risk factors of Invasive Fungal Disease, including hematopoietic stem cell transplantation, immunosuppression, glucocorticoids, etc. The clinical presentations were pulmonary (n=9), rhino-orbito-cerebral (n=4). But the manifestations were nonspecific. All enrolled patients completed mNGS. And most (8/13, 61.54%) of the samples were from blood. Fungi can be detected in all specimens, including Rhizopus (n=7), Rhizomucor (n=4) and Mucor (n=2). In addition, 7/13 (53.85%) specimens were detected bacteria at the same time and virus were detected in 5/13 (38.46%). Histopathological examination was completed in 5 patients, 3 of which were completely consistent with the results of mNGS. After treatment, 6 patients were cured, while the other 7 patients died.Conclusion: mNGS may be a