EFFECTS OF DISTURBANCE TYPE ON SOIL SEED BANKS IN A DEBRIS-FLOW PRONE DRY VALLEY OF NORTHERN YUNNAN
Soil seed banks of different ecosystems subject to different disturbances were studied in a dry valley prone to debris flow in Northern Yunnan. It was found that variation in the type of disturbance had a strong effect on the density and composition of the soil seed bank. Restoration with a Leucaena glauca plantation(with over 6 years free of disturbance from humans or domestic animals) increased the seed bank density and the dominant species changed from aridity-tolerant to shade-tolerant species. Seed bank density and the variety of species was reduced in an annually cut Coriaria sinica plantation, though the composition of the seed bank remained constant. Landslides and soil erosion had a negative effect on seed bank density and species types as many seeds were removed from the soil. Debris flow created the greatest disturbance as it destroying both the soil surface and seed bank.
Organic bulk heterojunction solar cells suffer from a huge, nonmonotonic loss of open-circuit voltage ${V}_{o\phantom{\rule{0}{0ex}}c}$ at low temperatures, which thwarts their practical application. The authors incorporate energetic disorder into a drift-diffusion model to study the ${V}_{o\phantom{\rule{0}{0ex}}c}-T$ relations under various working conditions. In reproducing the empirical observations, they find that disorder-suppressed carrier mobility is the culprit. This work provides a comprehensive picture from the charge-dynamics perspective that will facilitate the engineering of this emerging class of devices.