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Vegetation disturbance during infrastructure construction can cause serious ecological problems, especially in fragile environments. The Northern Shaanxi Loess Plateau is an oil industry base in China with a fragile ecosystem. Vegetation restoration on the disturbance area can effectively control soil erosion and ensure the safety of oil pipelines. In the linear disturbance area, surrounding vegetation traits and topography may play an important role in vegetation restoration by influencing propagules and recruitment microsites. This study aimed to reveal the influence of vegetation type and topography on vegetation restoration in the disturbance area along the oil pipeline. The results showed that 89 species were recorded, and they belonged to 30 families and 74 genera. These species were mainly native herbaceous plants, especially perennial herbs. The species number and species diversity index in the disturbance area had a positive relationship with the undisturbed area. The lateral undisturbed vegetation type and species reproductive strategies influenced the vegetation restoration in the disturbance area. The species that produce a large number of seeds or regenerate by rhizome recolonized quickly in the disturbance area. However, the shrubs and arbor species that need seeds for recruitment will take a long time for restoration. The topographic factor had an obvious influence on the vegetation restoration and species diversity in the disturbance areas. On the sunny and steep slopes, vegetation restoration was difficult and slow, and artificial measures were needed to control soil erosion and maintain soil moisture to help seedling recruitment and survival. [ABSTRACT FROM AUTHOR]

Extracellular enzymes are the major mediators of plant residue and organic matter decomposition in soil, frequently associated with microbial metabolic processes and the biochemical cycling of nutrients in soil ecosystems. However, the dynamic trends and driving factors of extracellular enzymes and their stoichiometry during plant residue transformation remain to be further studied. Here, we investigated the dynamics of extracellular enzymes and enzymatic stoichiometry in the "litter-soil" transformation interface soil (TIS) layer, an essential occurrence layer for microbially-mediated C transformation. The results indicated an unbalanced relationship between substrate resource supply and microbial metabolic demand. Microbial metabolism was limited by C (C/N-acquiring enzymes > 1) and P (N/P-acquiring enzymes < 1) throughout the observed stages of plant residue transformation. The initially higher extracellular enzyme activity reflected the availability of the active components (dissolved carbon (DC), nitrogen (DN), microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP)) in the substrate and the higher intensity of microbial metabolism. With the transformation of plant residues, the active fraction ceased to be the predominant microbial C source, forcing the secretion of C-acquiring enzymes and N-acquiring enzymes to obtain C sources and N nutrients from refractory substrates. Moreover, C/N-acquiring enzymes decreased, while C/P-acquiring enzymes and N/P-acquiring enzymes subsequently increased, which suggested that the microbial demand for N gradually increased and for P relatively decreased. Soil microorganisms can be forced into dormancy or intracellular mineralization due to the lack of substrate resources, so microbial biomass and extracellular enzyme activities decreased significantly compared to initial values. In summary, the results indicated that soil nutrients indirectly contribute to extracellular enzymes and their stoichiometry by affecting microbial activities. Furthermore, extracellular enzymes and their stoichiometry were more sensitive to the response of soil microbial biomass carbon. [ABSTRACT FROM AUTHOR]

Due to the atmospheric nuclear weapon tests carried out, terrestrial environments have been extensively contaminated by global fallout of plutonium (Pu) worldwide. The 249+240Pu inventories in soil profiles from undisturbed and flat forest or grasslands (reference sites) mainly from Europe and Asia are considered as important background for evaluating soil erosion. Thus, we conducted a literature survey over an area extending from 2.6°W to 148.9°E and from 53.2°S to 76.6°N, with the purpose of analyzing the spatial distribution of 239+240Pu inventories and possible controlling factors. The aim of this work was to derive an empirical model of 239+240Pu inventory based on currently available 239+240Pu data, precipitation and latitude. The results show that, in general, the latitudinal distribution of 239+240Pu inventory was consistent with the UNSCEAR reports. However, the 239+240Pu inventories are higher than the UNSCEAR data, especially in the Northern Hemisphere. In addition, close relationships (at the 0.01 significance level) were identified between 239+240Pu inventories and annual precipitation and latitude. An empirical formula was therefore developed to estimate 239+240Pu inventories in soils based on latitude and precipitation data. However, future research may require more data of measured 239+240Pu inventories in soil profiles that can be used to compare, validate and improve upon the accuracy of the inferred empirical equation. [ABSTRACT FROM AUTHOR]