Breakdown rates and macroinvertebrate colonisation of alder (Alnus glutinosa) leaves in an acid lake (Lake Orta, N Italy), before, during and after a liming intervention

To test the effectiveness of the liming intervention on Lake Orta, the speed of leaves decay and of colonisation processes by macrobenthonic fauna were studied on alder leaves (Alnus glutinosa) placed on the bottom of the lake and recovered after appropriate time intervals. Experiments were performed at two sites (North and South) and two depths (-3 and –18 m), during three successive winters: 1988-1989 (pre-liming), 1989-1990 (liming), 1990-1991 (post-liming). Two main results emerged: 1) alder leaves, which are known to have a medium to high decaying speed in a number of aquatic environments, behave in Lake Orta as a low speed species. Decaying processes in the three years are significantly different only in station N3, where the mean breakdown rate in 1988- 1989 is more than twice that measured in the two subsequent winters. 2) The species richness of colonising benthic fauna is low: the community is made up almost exclusively of Chironomidae, which form 70 to 100% of the whole population; among them, the genus Phenopsectra is always present, while Tanytarsus was collected only during the first year and in the less deep sampling sites. The mean population abundances were higher before liming

a wooded riparian strip set up for nitrogen removal can affect the water flux microbial composition

This research is part of a project aimed at verifying the potential of a specifically assessed wooded riparian zone in removing excess of combined nitrogen from the Zero river flow for the reduction of nutrient input into Venice Lagoon. Specific objectives were pursued to determine seasonal fluctuations of the microbial populations from the input water to a drainage ditch, conveying back the flux into the river after passing through the soil of the wooded riparian strip. The bacterial communities were determined by combined approaches involving cultivation, microscopic methods and DNA based techniques to determine both culturable and total microbial community in water. The results indicate that the size of the bacterial population, including the culturable fraction, increases from the river to the drainage ditch especially on the warm season. The multiple approach here adopted enabled also to demonstrate that the special condition created in the buffer strip supports the development and the metabolism of the microbial community. The nature of the bacterial population, in terms of phylotypes distribution, was investigated by 16S rDNA analysis indicating that the most represented genera belong to Gamma-proteobacteria, which is known to include an exceeding number of important pathogens. In spring, the effect of the buffer strip seems to significantly reduce such a sub-population. The changes observed for the total bacterial community composition become much evident in summer, as revealed by both denaturing gradient gel electrophoresis cluster analysis and by the diversity index calculation. The hydraulic management coupled to the suspension of farming practices and the development of the woody and herbaceous vegetation resulted in a condition suitable for the containment of undesired microbiota (mainly during the spring season) while continuing to support denitrification activity (especially throughout the summer) as verified by the total nitrogen removal

Longitudinal vegetation turnover in an eastern Rift Valley riparian corridor

AbstractEast African riparian corridors are biodiversity hot spots that occur in catchments degrading under deforestation and overgrazing. Quadrats and belt transects were employed to investigate plant succession along the River Gilgil, in the Kenyan Rift Valley. The study found that most species (total 365) were broadly distributed across the tropics, but Rift Valley endemics were 12.5%, and 4%–18% were exotic. Plant composition varied with altitude, lithology, soils and rainfall. Agglomerative (Jaccard) hierarchical clustering and Non‐metric Dimensional Scaling identified two and three vegetation groups, for quadrats and transects, respectively, correlated with lithology and soils. Indicator species analysis highlighted that the upstream portion of the catchment was characterised by forest taxa with few exotics. The downstream included woodland species adapted to mesic/xeric conditions and to overgrazing. Longitudinal change in species composition (β diversity) between sites was assessed by taking into consideration the contribution of 'spatial species turnover' and 'nestedness', resulting from species replacement and species loss, respectively. The β diversity of the riparian corridor vegetation was 0.40 and spatial turnover accounted for 80%–85% of this, while the rest was attributed to the nestedness component. Riverine and native trees increased downstream but with low regeneration. Afromontane vegetation extended its distribution towards lower altitudes

Riparian Zones—From Policy Neglected to Policy Integrated

1. Riparian zones are vital areas of interaction between land and rivers and are often degraded by several pressures such as urbanisation, intensive agriculture and river engineering works. 2. This policy brief provides five key policy messages and recommendations to be considered by policy-makers, scientists, managers, and stakeholders to enhance riparian zone management. 3. Adopting an integrated socioeconomic and environmentally dynamic view will ensure the sustainable management of riparian zones. 4. In light of climate change, it is critically important to conserve and/or restore the ecological integrity of riparian zones. 5. European Union Directives and national-scale legislation and regulations need updating to ensure coordinated implementation of riparian zone-related policies. 6. Stakeholder knowledge exchange, policy co-creation and adaptive management are key to enhancing riparian zone functions