Topography of mutational signatures in human cancer

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Variation of seasonal litterfall in subtropical montane cloud forests to typhoon severity and environmental factors

Forest litterfall is pivotal for biogeochemical cycles and for assessing the impacts of perturbations on ecosystems. Typhoon occurrence is the primary mechanism for producing litterfall; Taiwan is situated in one of the most frequently disturbed regions. However, no typhoons were recorded in 2018, only occurring three times since 1911. This rare occasion, along with the regular (2017) and extreme typhoon (2016) years, provides an opportunity to investigate the responses of typhoon-prone forest ecosystems to a future climate scenario: Elevated temperatures amplify the intensity but reduce the frequency of typhoons. We compared three years (2016–2018) of summer typhoon season (July–October) mean monthly litterfall (MML) in the subtropical montane cloud forests of northeastern Taiwan, and investigated the relationships between MML/typhoon-induced MML (ΔMML) and 17 biophysical, bioclimatic and topographic attributes. More MML was produced in 2016, caused by strong winds and heavy rainfall. However, there was no statistical difference between 2017 and 2018 since forests may also produce substantial amounts of litterfall in summer without typhoons. The relationship between ΔMML and 17 variables was relatively insensitive to typhoon severity. Variables associated with succession and forest management were crucial for modeling MML in the presence of typhoons, but none of them were pivotal for MML without typhoons. The mean air temperature and elevation (related to forest productivity) were crucial for MML without typhoons; surface curvature may form shelters to prevent extreme typhoon with reduced MML. These outcomes may shed light on future ecosystem dynamics in typhoon-prone forests under a changing climate. Abstract in Mandarin is available with online material.     

The evolution of hummock–depression micro‐topography in an alpine marshy wetland in Sanjiangyuan as inferred from vegetation and soil characteristics

The hummock–depression micro‐topography characteristics of the alpine marshy wetland in Sanjiangyuan are indicative of wetland degradation and the process by which healthy wetlands are transformed into flat grasslands. The aim of the present study was to examine changes in plant community structure and soil characteristics in a hummock–depression micro‐topography along a degradation gradient. We observed that: (a) the height and cover of dominant hydrophytes decreased gradually with an increase in degradation severity, leading to replacement by xerophytes; (b) with the transition from healthy to degraded wetlands, hummocks became sparser, shorter, and broader and became merged with nearby depressions; water reserves in the depressions shifted from perennial to seasonal, until they dried out completely; and (c) soil moisture content, porosity, hardness, and organic matter gradually decreased by 30.61%, 19.06%, 37.04%, and 73.27%, respectively, in hummocks and by 33.25%, 8.19%, 47.72%, and 76.79%, respectively, in depressions. Soil bulk density, soil electrical conductivity, and soil dry weight increased by 31%, 83.33%, and 105.44%, respectively, in hummocks, but by only 11.93%, 7.14%, and 97.72%, respectively, in depressions. The results show that hummock soils in healthy wetlands have strong water absorption properties, through which plant roots can penetrate easily. Wetland degradation reduces the water absorption capacity of hummock soil and soil saturation capacity of depressions, thus enhancing soil erosion potential and susceptibility to external factors. Soil moisture is a key environmental factor influencing wetland degradation, and grazing accelerates the process. Based on the changes observed in hummock morphology, vegetation, and soil properties along a degradation gradient, a conceptual model is proposed to illustrate the process of gradual degradation of marshy wetlands from healthy to transitional wetlands and finally to a degenerated state. Thus, our research provides insights into the degradation process of the alpine marshy wetland ecosystem in Sanjiangyuan.     

Influence of nanophase titania topography on bacterial attachment and metabolism

Surfaces with nanophase compared to conventional (or nanometer smooth) topographies are known to have different properties of area, charge, and reactivity. Previously published research indicates that the attachment of certain bacteria (such as Pseudomonas fluorescens 5RL) is higher on surfaces with nanophase compared to conventional topographies, however, their effect on bacterial metabolism is unclear. Results presented here show that the adhesion of Pseudomonas fluorescens 5RL and Pseudomonas putida TVA8 was higher on nanophase than conventional titania. Importantly, in terms of metabolism, bacteria attached to the nanophase surfaces had higher bioluminescence rates than on the conventional surfaces under all nutrient conditions. Thus, the results from this study show greater select bacterial metabolism on nanometer than conventional topographies, critical results with strong consequences for the design of improved biosensors for bacteria detection.     

Relative contributions of biotic and abiotic factors to the spatial variation of litter stock in a mature subtropical forest

Aims Dead plant material (i.e. litter) is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems. The storage of litter is jointly determined by its production from plants and decomposition in a given environment. However, only few studies have explored the relative importance of environmental (i.e. abiotic) and plant (i.e. biotic) factors in driving the spatial variation of litter mass. The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest.     

Variation in density of cattle-visiting muscid flies between Danish inland pastures

Abstract. The density of cattle-visiting flies (Muscidae) and the load of black-flies (Simulium spp.) were estimated in twelve and eighteen inland pastures in Denmark in 1984 and 1985 respectively. No differences in the geographical distribution pattern of the predominant cattle-visiting Muscidae were recorded, whilst the relative abundance and density of the species and the total fly-load varied considerably between pastures. In most cases the mean loads of Haema-tobia irritans (L.) and Hydrotaea irritans (Fall.) on heifers varied significantly in relation to site topography and shelter. These crude site variables explained 65–98% of the variation in densities of horn flies and sheep head flies observed between pastures. Highest densities of Hydrotaea irritans were primarily associated with permanent, low-lying, fairly sheltered grassland sites, whereas the density was low in temporary, dry, wind-exposed pastures. A comparable relationship was found for Haematobia irritans. With Haematobosca stimulans (Mg.) and Morellia spp. no relation between grassland environment and fly density was detected.