The indexes H-alpha and NSA/NSN were higher upstream of check dams: the presence of the check dams induced higher species richness and evenness, with alien species prevailing over native ones in the sedimentation wedge. Compared to control transects, vegetation was more extensive (higher GCC) and developed (higher WCH) in the upstream zones the reverse pattern was noticed in the downstream transects (lower GCC and WCH).
Viceversa torrent torrent#
The differences in the riparian vegetation among transects were found as the torrent ecological response to the strong contrasts surveyed in hydrological (q) and geomorphological (w/d, D50 and %fines) characteristics. Upstream of the check dams D50 of bed material was lower and %fines was higher compared to the control transects vice versa, the downstream transects showed higher D50 and lower %fines. Compared to the control transects, the values of w/d were higher upstream of check dams and lower downstream conversely, q was lower upstream and higher in downstream sites. Vegetation cover and structure were evaluated by Global Canopy Cover (GCC) and Weighted Canopy Height (WCH) respectively (Bombino et al., 2008) the index of alpha-diversity (H-alpha, Hill, 1973) and the ratio between the number of alien species and the number of native species (NSA/NSN) were chosen as indicators of species richness/abundance and degree of vegetation integrity, respectively. Channel section morphology was assessed by the width/depth ratio (w/d) the median particle size (D50) and the finer sediment fraction (%fines) were chosen to characterize channel bed material the specific discharge (q, the discharge per channel unit width) was assumed as measure of the flow regime. For each check dam three transects (one upstream, one downstream and one far from the check dam, located in the undisturbed zone and adopted as control) were identified at each transect, a set of geomorphological and ecological indicators were surveyed as follows. Field surveys on channel morphology, bed material and riparian vegetation were carried out close to five check dams in each of four mountain reaches of Calabria (Southern Italy).
This paper provides a further contribution to a better comprehension of the actions played by check dams on hydrological and geomorphological processes in headwaters and their effects on riparian ecosystem. However, the effects of check dams on channel section and riparian vegetation of torrents are not yet completely understood. It is known that installation of check dams noticeably influences torrent morphology and ecology.
0 kommentar(er)
