Effects of mowing date on the opportunities of seed dispersal of ditch bank plant species under different management regimes
Leng, X. ; Musters, C.J.M. ; Snoo, G.R. de - \ 2011
Journal for Nature Conservation 19 (2011)3. - ISSN 1617-1381 - p. 166 - 174.
agricultural landscapes - microsite limitation - diaspore transfer - field margins - fen meadows - restoration - grassland - diversity - soil - richness
Mowing and plant removal is a traditional practice in low-intensity farming and likely to lead to high plant species richness. Even today, scientific knowledge on the impact of mowing on seed availability is still very limited. We studied whether the seed availability of ditch bank plant species was affected by the timing of mowing and, if so, whether the effect varied according to management regime (nature reserve, agri-environment scheme (AES) with long-term management, AES with short-term management, conventional management). Our focus was on seed availability for transportation, because restoration of ditch bank vegetation is known to be limited by seed dispersal. The presence and seed-setting of 25 target species in 384 plots were recorded at the mowing date, under four management regimes. A Hierarchical Generalised Linear Model (HGLM) was used to analyse the effects of mowing date and management on the number of species setting seed. It suggests that when the mowing is twice annually, mowing on July 1st and on September 1st will result in a maximum number of species of which the seeds are available for transportation and, therefore, create largest opportunities for seed dispersal on ditch banks in the western peat area of the Netherlands. The effect of mowing date differs among species, with certain rare species like Caltha palustris and Lythrum salicaria in particular differing from the commoner species. A flexible mowing regime varying from year to year would therefore help to protect these rare species. The later peak in seed-setting found in nature reserves and long-term AES suggest a postponed mowing compared to conventionally management and short-term AES.
Prospects for fen meadow restoration on severely degraded fens
Klimkowska, A. ; Diggelen, R. ; Grootjans, A.P. ; Kotowski, W. - \ 2010
Perspectives in plant ecology, evolution and systematics 12 (2010)3. - ISSN 1433-8319 - p. 245 - 255.
diffuse phosphorus pollution - agri-environment schemes - plant-species diversity - adhesive seed-dispersal - former arable fields - ecological restoration - land-use - productivity gradient - microsite limitation - wetland restoration
The majority of fens in Europe have been transformed for agricultural purposes and have disappeared or become degraded. Fen meadows that developed under low-intensity management of fens also have become degraded. In this paper, we consider the available restoration methods, biotic constraints for restoration and new prospects and approaches for the reStoration of severely degraded fens. Due to irreversible changes in landscape settings, hydrology, soil and trophic conditions, a full restoration to natural mires is unlikely. Yet, an improvement of the ecosystem functions and revival of biodiversity in degraded fens is possible. A restoration of semi-natural meadows is one of the alternative targets. Important for restoration efforts to succeed are a sufficient reduction of nutrient levels and preventing acidification. In general, a combination of topsoil removal and seed transfer is an effective measure for fen meadow restoration, provided that groundwater seepage can be re-established. There are also several biotic limitations to fen meadow restoration, due to limited propagule availability of target species and the legacy of the former vegetation in form of its soil seed bank and high seed production by unwanted species. Under the present environmental conditions, the re-development of fen meadows on degraded fens will result in species compositions different from those observed in the past and such restoration may require considerable time and effort.
Bottlenecks and Spatiotemporal variation in the sexual reproduction pathway of perennial meadow plants.
Jongejans, E. ; Soons, M.B. ; Kroon, H. de - \ 2006
Basic and Applied Ecology 7 (2006)1. - ISSN 1439-1791 - p. 71 - 81.
dispersal seed predation - microsite limitation - population-dynamics - solidago-altissima - grassland plants - recruitment - wind - establishment - germination - colonization
Sexual reproduction is important for the growth of populations and the maintenance of genetic diversity. Several steps are involved in the sexual reproduction pathway of plants: the production of flowers, the production of seeds and the establishment of seedlings from seeds. In this paper we quantify the relative importance and spatiotemporal variability of these different steps for four grassland perennials: Centaurea jacea, Cirsium dissectum, Hypochaeris radicata and Succisa pratensis. We compared undisturbed meadows with meadows where the top soil layer had been removed as a restoration measure. Data on the number of flower heads per flowering rosette, the numbers of flowers and seeds per flower head, and the seedling establishment probabilities per seed were collected by field observations and experiments in several sites and years. Combination of these data shows that H. radicata and S. pratensis have higher recruitment rates (1.9 and 3.3 seedlings per year per flowering rosette, respectively) than the more clonal C. dissectum and C. jacea (0.027 and 0.23, respectively). Seedling establishment is the major bottleneck for successful sexual reproduction in all species. Large losses also occurred due to failing seed set in C. dissectum. Comparison of the coefficients of variation per step in space and time revealed that spatiotemporal variability was largest in seedling establishment, followed closely by flower head production and seed set