The impact of mechanical harvesting regimes on the aquatic and shore vegetation in water courses of agricultural areas of the Netherlands

Abstract

It was demonstrated that a mechanical harvesting regime can influence the species composition of ditch vegetation at the community level. This effect, however, was very small compared with those of other factors such as the between-site and the within-site spatial variation, and several soil and water quality parameters. Cutting in November had the largest effect, in that it caused the greatest extremes in species cover. The vegetation was composed of 136 plant species. The semi-aquatic and aquatic species were less numerous than the terrestrial ones (52 versus 84). The total number per vegetation type and site ranged from 5 to 49; that of persistent plant species, from 4 to 22. Only 16~o of the species was significantly influenced by the mechanical harvesting regime. The significant effects of the mechanical harvesting regime on plant species were related to plant-inherent factors. Mechanical harvesting repeated within a year, on one hand, opened up the vegetation, 1) freeing sites for colonization of new species, 2) improving the light climate for seedlings which had already colonized; on the other hand, it exhausted (carbohydrate) reserves of solitary species. Mechanical harvesting once a year in November had a contrasting effect in that it caused suffocation of the shore vegetation in spring by the not yet decomposed plant material harvested in autumn. The highest species richness was attained for the aquatic vegetation: on sand by cutting three times per year (in May, July and September), and on peat by cutting once a year (in November); and for the shore vegetation: on sand once a year (in May) and two times per year (in May and July), and on peat once a year (in May or November).

Effects of stream restoration and management on plant communities in lowland streams

“…A strong influence of management on macrophyte communities in lowland streams is in line with previous investigations (Wiegleb, Wolfgang & Todeskino, 1989;Best, 1994;Sabbatini & Murphy, 1996;Spink, Murphy & Westlake, 1997;Baattrup-Pedersen et al, 2002. Sparganium emersum, the dominant component of the vegetation in most of the channelised streams, was strongly associated with high-intensity weed cutting.…”

Impacts of different weed cutting practices on macrophyte species diversity and composition in a Danish stream

“…As in previous investigations examining effects of management on macrophyte communities in Denmark and elsewhere (Best, 1994;King, 1996;Sabbatini and Murphy, 1996a,b;Baattrup-Pedersen et al, 2002; in press) our data confirm that weed cutting in streams can influence macrophyte communities. We found that three annual weed cuttings involving either a cutting of the whole stream channel or a less comprehensive cutting of only one central channel led to directional changes in macrophyte composition.…”

The distribution and conservation of threatened Sphaeriidae on British grazing marshland

“…These three species must overlap in habitat requirements, at least at the ditch scale: P. pseudosphaerium occurred in ditches with diverse submerged, floating, emergent and amphibious plants, likely to be at the mid-stages of vegetational succession that follow some years after initial ditch clearance. At this stage, emergent and amphibious plants have yet to dominate, and low-intensity management allows the recolonisation of more locally-demanding species between dredging operations (Newbold et al 1989;van Strien et al 1991;Best 1993Best , 1994RSPB et al 1997). This contrasts with late hydro-successional conditions of well developed emergent and submerged vegetation required by another RDB snail, Segmentina nitida (Watson and Ormerod 2004a, b).…”