Soil erosion is a severe environmental problem on the Loess Plateau, China. Vegetation restoration is the most efficient method to control soil erosion and introducing late-successional plant species may accelerate natural succession. However, the progress is affected by soil conditions and the appropriate thresholds of soil condition for seed addition are needed. Our objectives were to identify the vegetation types, examine the key soil factors affecting the vegetation variation, and determine the thresholds of the soil factors for each vegetation type. Five vegetation types in secondary succession were identified: association (assoc.) Artemisia scoparia assoc. Bothriochloa ischaemum assoc. Artemisia gmelinii Artemisia giraldii assoc. Ostryopsis davidiana Rubus parvifolius L., Syringa oblate and assoc. Sophora viciifolia Years since abandonment (YEAR), alkali-hydrolysable nitrogen (AHN), soil water content (SW), and total phosphorus (TP) were the key factors used to discriminate among vegetation types. Assoc. A. scoparia developed in croplands that had been abandoned for less than 11 years. Assoc. B. ischaemum developed in croplands abandoned for more than 11 years with lower soil nutrient levels (0.30 ≤ TP ≤ 0.646 g kg−1 and 16.72 ≤ AHN ≤ 32.62 mg kg−1). Assoc. A. gmelinii + A. giraldii always required greater TP (0.646 ≤ TP ≤ 0.79 g kg−1) to develop. When soil water content was lower (6.6 ≤ SW ≤ 8.4%), the assoc. S. viciifolia developed; otherwise, other associations, such as assoc. O. davidiana, developed. These soil thresholds can be used as references for guiding restoration, such as specifying proper soil conditions for seed sowing.
Interleukin-37 (IL-37), a novel member of the IL-1 family, plays fundamental immunosuppressive roles by broadly reducing both innate inflammation and acquired immunity, but whether it is involved in the pathogenesis of tuberculosis (TB) has not been clearly elucidated. In this study, single nucleotide polymorphism (SNP) analysis demonstrated an association of the genetic variant rs3811047 of IL-37 with TB susceptibility. In line with previous report, a significant elevated IL-37 abundance in the sera and increased expression of IL-37 protein in the peripheral blood mononuclear cells (PBMC) were observed in TB patients in comparison to healthy controls. Moreover, release of IL-37 were detected in either macrophages infected with Mycobacterium tuberculosis (Mtb) or the lung of BCG-infected mice, concurrent with reduced production of proinflammatory cytokines including IL-6 and TNF-α. Furthermore, in contrast to wild-type mice, BCG-infected IL-37-Tg mice manifested with reduced mycobacterial burden and tissue damage in the lung, accompanied by higher frequency of Th1 cell and less frequencies of regulatory T cells and Th17 cells in the spleen. Taken together, our findings demonstrated that IL-37 conferred resistance to Mtb infection possibly involving suppressing detrimental inflammation and modulating T cell responses. These findings implicated that IL-37 may be employed as a new molecular target for the therapy and diagnosis of TB.
Abstract Vegetation succession depends on the availability of suitable propagules in the soils, and an understanding of soil seed banks is important for effective vegetation restoration of abandoned croplands. Aims of this study were to identify characteristics of soil seed bank, relationship with standing vegetation, and potential significance of soil seed bank for vegetation restoration in abandoned croplands on the hilly-gullied Loess Plateau. Results of field survey, germination, and correspondence analysis showed that density of soil seed bank ranged from almost 900 through almost 6470 seeds m−2 at 0–5 cm depth and almost 120 through almost 2470 seeds m−2 at 5–10 cm depth, with species richness of 7–14. Early successional species dominated soil seed bank, while later successional species occurred only at low densities. Similarity between soil seed bank and standing vegetation was low (with an average of 0.261). Most important variables contributing to the variation of the standing vegetaion included soil water, extractable P, soil seed bank density, and aspect. Soil seed bank alone explained 32% of vegetation community variation. Potential for vegetation restoration from soil seed banks is limited, and it is recommended to transplant some later successional species into abandoned croplands to accelerate succession. Keywords: community similaritycorrespondence analysisseed germination methodsoil erosion We thank the NSFC projects (40771126; 40571094; 40271074) for funding this research, the assistance of Ansai Ecological Experimental Station of Soil and Water Conservation, CAS. We are also grateful to X. H. Ma, Z. G. Zhang, L. R. Xu, H. Y. Zou, and J. M. Cheng for field survey and experiment suggestions. We would like to thank the three anonymous reviewers for constructive comments. Notes SW0-5, soil water content in 0–500 cm layers; SW2-5, soil water content in 200–500 cm layers; SOM, soil organic matter. CV, Coefficient of variation; SE, Standard Error. Frequency of seeds (%) in the soil seed bank is based on presence in 144 sampling points and in vegetation is based on 72 sampling points; Seed density is the range of the mean value (6 sub-samples) in the plots in which it occurred. CVA, Canonical Variate Analysis; PCVA, Partial Canonical Variate Analysis; ∗P < 0.05; ∗∗P < 0.01; the inertia of CVA is 3.000; "/", "partialling out" the following variable. Bs, species forming a persistent seed bank; V, possessing lateral vegetative spread; VBs, species characterized by Bs and V; W, producing numerous widely dispersed seeds.
Water flushing was applied to different land use plots on Loess slopes to examine the effect of land use changes on flow hydraulics and the transport of soil surface solutes in erosion. The runoff and movement of sediment and soil solutes were analyzed in relation to land use and scouring flow. Flow experiments were conducted with five land use treatments: abandoned land (Salsola ruthenica), alfalfa land (Medicago sativa), corn land, scrub land (Caragana intermedia), and bare land. The results show that at the same scouring time, the cumulative sediment yields with different land use types are: bare land > corn land > Caragana intermedia land > abandoned land > alfalfa land. The unit sediment loads are similar to this modulus of the cumulative sediment yields. The pre-experimental water contents of the soil profile exerted a greater effect on the content of soil moisture and its distribution on the slope than that of the antecedent solute contents in the field experiment conditions for different land use types. The land use types also affected the surface transport of soil solute. The bromide concentrations in runoff were in the order of: bare land > corn land > alfalfa land > Caragana intermedia land > abandoned land. The nitrate concentrations in runoff with different land use types had no obvious orderliness. However, the nitrate concentration was lineally related to the bromide concentration, as expressed by CNO3−=3.01CBr−+28.35 (R2=0.90).
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