Has riparian woody vegetation a positive effect on dispersal and distribution of mayfly, stonefly and caddisfly species?

During their adult life stage most EPTs (Ephemeroptera, Plecoptera and Trichoptera) disperse by flying following the riparian corridor. Although it is likely that riparian forest fosters EPT dispersion, this has not been empirically tested in a larger dataset yet and several additional open questions remain. First, it is unclear if the effect of riparian vegetation on EPT community differs and depends on the spatial scale. Second, it is not assessed how the effect of riparian vegetation on EPTs is and how it changes depending on other environmental stressors. Third, the effect potentially depends on riparian vegetation characteristics such as trees species composition and cover. We analysed 98 sites in lowland and lower mountain streams in Northrhine Westfalia, Germany, at two longitudinal and two lateral spatial scales. At each site we calculated the EPT community dispersal ability and quantified other environmental stressors as well as deciduous and coniferous woody cover in the riparian buffer. Generalised Linear Models were used to identify the conditions under which woody riparian vegetation has a significant effect on EPT community dispersal ability. Our results confirmed that the share of weak dispersers increased with deciduous woody riparian cover in low mountain streams, indicating a potential positive effect of natural riparian forest on landscape connectivity. This relationship was only observed at the regional longitudinal scale irrespective of the lateral spatial scale. Tree species composition was relevant as coniferous forests did not contribute to this effect. Finally, there was some indication that the positive effect of deciduous riparian forest occurs at a moderate woody cover and levels off at higher values. This highlights the role of riparian forests not only as habitat but also dispersal corridor in river management and the need to preserve and restore natural woody riparian vegetation to improve EPT communities and macroinvertebrates ecological status.

Assessing Restoration Effects on River Hydromorphology Using the Process-based Morphological Quality Index in Eight European River Reaches.

The Morphological Quality Index (MQI) and the Morphological Quality Index for monitoring (MQIm) have been applied to eight case studies across Europe with the objective of analyzing the hydromorphological response to various restoration measures and of comparing the results of the MQI and MQIm as a morphological assessment applied at the reach scale, with a conventional site scale physical-habitat assessment method. For each restored reach, the two indices were applied to the pre-restoration and post-restoration conditions. The restored reach was also compared to an adjacent, degraded reach. Results show that in all cases the restoration measures improved the morphological quality of the reach, but that the degree of improvement depends on many factors, including the initial morphological conditions, the length of the restored portion in relation to the reach length, and on the type of intervention. The comparison with a conventional site scale physical-habitat assessment method shows that the MQI and MQIm are best suited for the evaluation of restoration effects on river hydromorphology at the geomorphologically-relevant scale of the river reach.