Urban environments are vulnerable to the introduction of non-native species and sometimes contribute to their invasion success. Knowing how urban landscape features affect the population dynamics of exotic species is therefore essential to understand and manage these species. The spotted-wing drosophila, Drosophila suzukii, is a highly polyphagous fruit fly that has become a very problematic invasive species over the last decade. Because of its important damage on fruit production, D. suzukii populations have mainly been studied in agricultural areas, while their dynamics in urban landscape remain poorly explored. The objective of this study was to investigate the role of urban environment in the invasion success of D. suzukii by identifying local and landscape factors driving the abundance of the fly along seasons and urbanization gradients. To achieve this, 526 insect traps were randomly set in four different habitats (urban forest, park, riverside and town centre) along an urbanization gradient in the city of Amiens (France), between September 2018 and August 2019. The influence of landscape and local environmental variables on Drosophilidae species diversity and composition was examined using GLM and multivariate analyses. We found that Drosophilidae species richness and abundance were negatively impacted by urbanization. The Drosophilidae community was dominated by D. subobscura and D. suzukii, but their relative abundance varied with seasons. Drosophila suzukii used urban forest during winter and also during heat waves in summer. The fly was still active in this habitat in winter when the ground was covered with snow. The cover of brambles, shrubs, soil litter and dead wood debris were identified as valuable ecological indicators of the presence of D. suzukii. We highlight the role of the different components of urban environment in the ecology of D. suzukii, particularly with regard to its winter survival. These results could serve for designing management strategies in urban habitats in order to reduce the invasion success of D. suzukii.
Permafrost degradation profoundly affects carbon storage in alpine ecosystems, and the response characteristics of carbon sequestration are likely to differ at the different stages of permafrost degradation. Furthermore, the sensitivity of different stages of permafrost degradation to climate change is likely to vary. However, related research is lacking so far on the Qinghai-Tibetan Plateau (QTP). To investigate these issues, the Shule River headwaters on the northeastern margin of the QTP was selected. We applied InVEST and Noah-MP land surface models in combination with remote sensing and field survey data to reveal the dynamics of different carbon (vegetation carbon, soil organic carbon (SOC), and ecosystem carbon) pools from 2001 to 2020. A space-for-time analysis was used to explore the response characteristics of carbon sequestration along a gradient of permafrost degradation, ranging from lightly degraded permafrost (H-SP) to severely degraded permafrost (U-EUP), and to analyze the sensitivity of the permafrost degradation gradient to climate change. Our results showed that: (1) the sensitivity of mean annual ground temperature (MAGT) to climatic variables in the U-EUP was stronger than that in the H-SP and S-TP, respectively; (2) rising MAGT led to permafrost degradation, but increasing annual precipitation promoted permafrost conservation; (3) vegetation carbon, SOC, and ecosystem carbon had similar spatial distribution patterns, with their storage decreasing from the mountain area to the valley; (4) alpine ecosystems acted as carbon sinks with the rate of 0.34 Mg ‧ha 1 ‧a 1 during 2001-2020, of which vegetation carbon and SOC accumulations accounted for 10.65 % and 89.35 %, respectively; and (5) the effects of permafrost degradation from H-SP to U-EUP on carbon density changed from promotion to inhibition.
The effect of black carbon (BC) on climate forcing is potentially important, but its estimates have large uncertainties due to a lack of sufficient observational data. The BC mass concentration in the southeastern US was measured at a regionally representative site, Mount Gibbes (35.78 degreesN, 82.29 degreesW, 2006 m MSL). The air mass origin was determined using 48-h back trajectories obtained from the hybrid single-particle Lagrangian integrated trajectory model. The highest average concentration is seen in polluted continental air masses and the lowest in marine air masses. During the winter, the overall average BC value was 74.1 ng m(-3), whereas the overall summer mean BC value is higher by a factor of 3. The main reason for the seasonal difference may be enhanced thermal convection during summer, which increases transport of air pollutants From the planetary boundary layer of the surrounding urban area to this rural site. In the spring of 1998. abnormally high BC concentrations from the continental sector were measured. These concentrations were originating from a biomass burning plume in Mexico. This was confirmed by the observations of the Earth probe total ozone mapping spectrometer. The BC average concentrations of air masses transported from the polluted continental sector during summer are low on Sunday to Tuesday with a minimum value of 256 ng m(-3) occurring on Monday, and high on Wednesday to Friday with a maximum value of 379 ng m(-3) occurring on Friday. The net aerosol radiative forcing (scattering effects plus absorption effects) per unit vertical depth at 2006 m MSL is calculated to be - 1.38 x 10(-3) W m(-3) for the southeastern US. The magnitude of direct radiative forcing by aerosol scattering is reduced by 15 +/- 7% due to the BC absorption. (C) 2001 Elsevier Science Ltd. All rights reserved.