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Abstract Investigations into the photosynthetic response of urban trees on paved land under drought stress would help to improve the management of trees under rapid urbanization and climate change. An experiment was designed to grow two common greening tree saplings, ash (Fraxinus chinensis Roxb.) and ginkgo (Ginkgo biloba L.), in environments of both land pavement and drought. The results showed that (1) land pavement increased surface and air temperatures and decreased air humidity as well as net photosynthetic rate (P n) and photosynthetic capacity (A max) of ginkgo significantly; (2) drought significantly decreased P n , A max and maximum net photosynthetic rate (P nmax) as well as other photosynthetic parameters of both ash and ginkgo; (3) the negative effects of the combination of land pavement and drought on photosynthetic parameters were more significant than the effects of drought treatment for both ash and ginkgo. This implies that urban trees, especially those growing on land pavements, will confront harsher environments and a greater decline of photosynthesis under the severe and more frequent droughts predicted in the future. Overall, ash showed more tolerance to land pavement and drought than ginkgo, indicating that the selection of tolerant tree species is important for urban planting. Graphical abstract Unlabelled Image Highlights • Land pavement inhibited photosynthesis of ginkgo significantly. • Drought significantly decreased photosynthesis of both ash and ginkgo. • Greater inhibition of land pavement on photosynthesis of urban trees under drought • Studying photosynthesis processes helps to explain non-stomatal regulation of tree. [ABSTRACT FROM AUTHOR]

As the main solid waste disposal method in China, landfill sites are considerable sources of methane (CH 4) and carbon dioxide (CO 2). This study characterized the seasonal variation of CH 4 and CO 2 effluxes at a large and well-managed final covered landfill site in China. A three-year monitoring program was conducted. There were two different seasonal variation patterns for hotspot and non-hotspot' CH 4 and CO 2 effluxes. For non-hotspots, the CH 4 and CO 2 effluxes' seasonal variations were mainly affected by the seasonal change of the landfill's cover soil respiration activity, particularly the CH 4 oxidation capability. CH 4 had a higher efflux in winter; in other seasons, the CH 4 efflux fluctuated around 0; the CO 2 effluxes were (1) increased in spring and peaked in summer or early autumn; (2) then, they decreased to a minimum value in late autumn or early winter; and (3) fluctuated with the CH 4 efflux in winter. The CH 4 emissions in winter account for 60.4–84.4% of the all year outputs. For the hotspots', the CH 4 and CO 2 effluxes seasonal variations were mainly determined by the seasonal change of the landfill cover's soil gas permeability. The ratio of CH 4 emissions in winter to the all year outputs range from 17.4 to 68.7%. Unlabelled Image • Two different seasonal patterns for hotspots and non-hotspots CH 4 and CO 2 effluxes • CH 4 emissions of non-hotspots in winter account for 60 to 84% of all year outputs • CH 4 emissions of hotspots in winter account for 17 to 69% of all year outputs [ABSTRACT FROM AUTHOR]