Land Cover Changes (1963–2010) and Their Environmental Factors in the Upper Danube Floodplain

To analyze the changes in the Upper Danube Floodplain, we used aerial photos to quantify the change of landscape pattern from 1963 to 2010. We focused on typical floodplain habitats, i.e., riparian forest and floodplain grassland. We used landscape metrics and transformation matrix to explore changes in land cover structure and composition. The active floodplain experienced increasing fragmentation from 1963 to 2010. Despite an increase of aggregation, riparian forest suffered a 2.3% area loss from 1995 to 2010. Arable land in the active floodplain declined by 28.5%, while its patch size significantly increased. Elevation, distance to river and soil quality were the most relevant environmental factors for the land cover change in the floodplain. Higher soil quality or longer distance to river led to an increase of conversion from grassland into arable land; grassland patches with poorer soil quality were likely to change into riparian forest; riparian forest closer to the river and with a lower height above mean water level tended to remain stable. This comprehensive understanding of historical land cover change and environmental factors is needed for the enhancement of landscape functions and sustainable development in the floodplain

Long-term success of floodplain meadow restoration on species-poor grassland

Restoration of floodplain meadows remains a challenge, as many degraded sites suffer from seed limitation. The transfer of seed-containing plant material from species-rich donor sites is a widely used method to restore semi-natural grasslands. However, most studies on the success of such restoration projects comprise limited time frames. As factors determining restoration success may only become evident after many years, long-term observations are crucial. We re-investigated 20 restored grassland sites in the floodplain of the Northern Upper Rhine 13–16 years after plant material transfer with different soil preparation treatments. To this end, we carried out vegetation surveys on 254 permanent plots and studied the potential influence of soil preparation, soil nutrients, and hydrology on plant species composition, diversity, and transfer of target species. Since sustainable agricultural use is important to ensure the long-term stability of restored semi-natural grasslands, we further investigated biomass productivity and feeding value. While most target species increased in frequency or remained stable over time, we found no positive long-term effect of soil preparation on vegetation development and target species establishment. Instead, increased biomass yield and flooding frequency led to reduced restoration success, while higher soil C/N ratios had a positive effect. Overall, restoration measures did not affect the agricultural value of the restored grasslands, which had higher dry matter biomass yields compared with the donor sites. Our results indicate that the positive effect of soil preparation on the number and cover of target species, which is regularly reported in short-term studies, diminishes over time, and other factors such as site conditions become increasingly important. Furthermore, additional plant material transfer or manual seeding may be necessary to support target species establishment. Concerning agricultural usability, the integration of restored floodplain meadows in farming systems is possible and can ensure long-term management and thus stability of these ecosystems. Our study shows that long-term monitoring of restoration projects is necessary, as factors determining restoration success may only become evident in the long-term

Grassland restoration with plant material transfer – bridging the knowledge gap between science and practice

In Central Europe, species-rich grasslands have strongly diminished over the last century. The transfer of seed-containing plant material from donor sites with a desired species composition to restoration sites is a well-established method to restore species-rich grasslands. Despite a plethora of available literature, restoration projects with plant material transfer often fail or do not reach the planned goals. Practitioners’ knowledge is a highly important but underexplored source of information on factors deciding about success of restoration projects. At the same time, it is unclear to which degree scientific findings on success factors are known and considered by practitioners, and if science actually investigates the most relevant aspects for practice. To bridge the gap between practitioners’ knowledge and restoration science, we conducted semi-structured interviews with 33 practitioners involved in plant material transfer projects. Using qualitative content analysis, we analysed the interviews for success factors, and compared them to success factors of plant material transfer as investigated in peer-reviewed European studies on the method. We found that science investigated a broad range of practical, technical, and ecological success factors, and that practitioners were generally well aware of this evidence, trying to make use of the knowledge. Failure of practitioners’ projects often resulted from organizational obstacles, which were founded in lacking trust and low experience levels among the involved people. We advise unexperienced practitioners to involve more experienced practitioners in their projects if possible. Furthermore, we emphasize the importance of identifying relevant local stakeholders and building trustful regional networks. Interdisciplinary scientific studies considering success factors beyond practical and ecological aspects are required to support widespread effective grassland restoration with plant material transfer

Performance of four floodplain meadow plant species after a 2-week flooding period.

<p>Performance of four floodplain meadow plant species after a 2-week flooding period.</p

Time schedule and air temperatures for the flooding experiment of four floodplain meadow species.

<p>(A) Time schedule of age groups: four age groups with a 2-week flooding treatment starting 2, 4, 6, and 8 weeks after germination (age2, age4, age6, age8) and one unflooded control group (noFl) with regular growth through 12 weeks. (B) Temperature trend during time of the experiment (solid line: daily mean temperature, dashed line: daily minimum temperature, dotted line: daily maximum temperature). Temperature data from HLNUG (Hessian Agency for Nature Conservation, Environment and Geology, <a href="http://www.hlnug.de" target="_blank">http://www.hlnug.de</a>), weather station Linden (distance from experimental site: 700 m).</p

Differences in the survival of four floodplain meadow species among five age groups.

<p>Differences in the survival of four floodplain meadow species among five age groups.</p

Effects of a 2-week flooding treatment on survival of four floodplain meadow plant species.

<p>Cumulative survival of <i>Veronica maritima</i> L., <i>Veronica teucrium</i> L., <i>Sanguisorba officinalis</i> L., and <i>Sanguisorba minor</i> Scop. after a 2-week flooding treatment, starting 2, 4, 6, and 8 weeks, respectively, after germination (age2-age8), and a control group with no flooding (noFl). age2, dot-dashed line & plus; age4, dotted line & filled triangle point up; age6, two-dashed line & circle; age8, long-dashed line & triangle point down; noFl, solid line & cross.</p

Performance of four floodplain meadow plant species after a 2-week flooding period.

<p>Mean (± 95% confidence interval) logarithmic response ratio of plant height (A), leaf number (B) and biomass (C), and mean (± 95% confidence interval) specific leaf area (SLA, D) for each species-seedling age group combination: <i>Veronica maritima</i> L., <i>Veronica teucrium</i> L., <i>Sanguisorba officinalis</i> L., and <i>Sanguisorba minor</i> Scop.; flooding started 2, 4, 6, and 8 weeks after germination (age2-age8), and control group with no flooding (noFl). Effects of flooding treatments on survived plants were considered significant (i.e. different from the controls) when 95% CI did not overlap with zero. Missing bars represent groups with a mortality of 100%.</p