Subtropical reservoir shorelines have reduced plant species and functional richness compared with adjacent riparian wetlands

Abstract

Dam construction has large negative effects on biodiversity in river and riparian ecosystems worldwide. This study aimed to determine whether reservoir shorelines had lower plant species diversity and functional diversity than unregulated or lightly regulated riparian wetlands and to examine the responses of plant diversity and functional traits to reservoir shoreline environmental gradients. We surveyed 146, 44, and 67 plots on reservoir shorelines and in mainstem and tributary riparian wetlands, respectively, in a subtropical river-reservoir system. Species richness, functional richness, evenness, and divergence were calculated to reflect the species and functional diversity of plant communities. Environmental factors including elevation above water level, slope, landform type, substrate, disturbance, and cover were measured. The results showed that both species and functional richness were significantly lower on reservoir shorelines than in riparian wetlands. The relative species number of clonal plants and relative cover of annual plants were both negatively related to slope and elevation. Structural equation modeling and other statistical analyses indicated that most environmental factors had significant effects on species and functional richness on reservoir shorelines but had no significant effect on functional evenness and divergence. Our findings suggest that reservoir shoreline wetlands formed by damming rivers and inundating pre-existing riparian wetlands can be a biodiversity coldspot in regulated rivers at the plot level. Topographic factors are important in determining the plant diversity and vegetation establishment on reservoir shorelines in the Yangtze River basin.

Topography and land use effects on spatial variability of soil denitrification and related soil properties in riparian wetlands

“…The Han River, originating from the Ningqiang county of Shaanxi province, is the largest tributary of the Yangtze River, with a drainage area of approximately 159,000 km 2 and a total length of 1577 km (Liu et al, 2013). The Han River basin belongs to the north sub-tropic monsoon climatic region.…”

“…Urban areas occupy less than 1% of the total basin area (Li et al, 2008). Because the upper basin is located in the mountainous region, the riparian wetlands are restricted to a very narrow band (Liu et al, 2013). There are many rivers or streams in the middle Han River basin, where the topography and land use are complex and where most of the riparian wetlands have a width over 10 m. The discharge of these rivers and streams decreases during the winter and spring (from December to May) as a result of seasonal precipitation and evapotranspiration.…”

“…The slope perpendicular to the contour lines was measured on each transect with a clinometer (Liu et al, 2013). The distance to the river of each transect was measured using a tape.…”

“…In the field, the substrate was roughly classified into three categories based on soil grain size and texture: gravel, sand and loam (Liu et al, 2013). In the laboratory, soil pH was measured in a soil to water ratio of 1: 5 (v/v) by a pH meter and soil moisture was analyzed gravimetrically by drying for 24 h at 105 • C. To determine the percentage of fine substrates (i.e., sand, silt and clay), 50 g of air-dried soils were sieved through a 2-mm soil sieve (Wood and Armitage, 1997).…”

Damming water influences the structure, composition and functions of adjacent savannahs

“…al., 2015). However, for the following three reasons, this increase in species does not compensate for those lost due to the dam construction: 1) species richness in dammed riparian forests is lower than that of nondammed riparian forest (Liu, Liu, Liu, Song and Zhang, 2013); 2) the new species are different to those that exis- show that the bark thickness of cerrado species is three times greater than that of forest species (Hoffman and Solbrig, 2003), and the basal area is even lower.…”