TY - JOUR

T1 - Vegetation responses to environmental conditions in floodplain grasslands

T2 - prerequisites for preserving plant species diversity

AU - Härdtle, Werner

AU - Redecker, Bernd

AU - Aßmann, Thorsten

AU - Meyer, Hartmut

PY - 2006/5/2

Y1 - 2006/5/2

N2 - We studied plant species responses to environmental conditions in floodplain grasslands (alliance Cnidion) of the river Elbe (northern Germany) in order to describe relationships between species composition/diversity and underlying site gradients. We analysed a total area of 639 ha of floodplain grasslands, using 98 sampling plots. Vegetation responses to environmental conditions were examined by means of DCA. The relationships between species diversity and environmental conditions were examined using regression analyses. Our results show that species composition and species richness are mainly affected by present-day utilization, by the phosphate supply and by the productivity of stands. Species richness decreases significantly under grazing, with increasing phosphate supply and productivity of stands. Intermediate productivity levels, mowing and high inundation frequencies promote floodplain target species. Ninorg availability and base availability have only a minor impact on species composition/species diversity. Productivity is closely related to the amount of plant available phosphate. Low phosphate concentrations in the topsoil are particularly characteristic of Cnidium dubium floodplain meadows. Therefore, it is likely that in floodplain grasslands with low to intermediate productivity, phosphate is the most important factor influencing plant competition and plant species diversity. We hypothesize that an increased phosphate supply increases stand productivity and, hence, the competition for light, thus excluding weak competitors. This interpretation is supported by the present-day distribution of C. dubium floodplain meadows of the river Elbe: these are concentrated in the hybrid (between summer and winter dykes) and fossil floodplain (landward side of winter dykes), but have been replaced in the functional floodplain by grass-dominated plant communities as a result of a steady increase in the river water phosphate content. It is, therefore, only in the hybrid and fossil floodplain grasslands that species diversity may be preserved in the long term, as the P input is lower here than in the functional floodplain.

AB - We studied plant species responses to environmental conditions in floodplain grasslands (alliance Cnidion) of the river Elbe (northern Germany) in order to describe relationships between species composition/diversity and underlying site gradients. We analysed a total area of 639 ha of floodplain grasslands, using 98 sampling plots. Vegetation responses to environmental conditions were examined by means of DCA. The relationships between species diversity and environmental conditions were examined using regression analyses. Our results show that species composition and species richness are mainly affected by present-day utilization, by the phosphate supply and by the productivity of stands. Species richness decreases significantly under grazing, with increasing phosphate supply and productivity of stands. Intermediate productivity levels, mowing and high inundation frequencies promote floodplain target species. Ninorg availability and base availability have only a minor impact on species composition/species diversity. Productivity is closely related to the amount of plant available phosphate. Low phosphate concentrations in the topsoil are particularly characteristic of Cnidium dubium floodplain meadows. Therefore, it is likely that in floodplain grasslands with low to intermediate productivity, phosphate is the most important factor influencing plant competition and plant species diversity. We hypothesize that an increased phosphate supply increases stand productivity and, hence, the competition for light, thus excluding weak competitors. This interpretation is supported by the present-day distribution of C. dubium floodplain meadows of the river Elbe: these are concentrated in the hybrid (between summer and winter dykes) and fossil floodplain (landward side of winter dykes), but have been replaced in the functional floodplain by grass-dominated plant communities as a result of a steady increase in the river water phosphate content. It is, therefore, only in the hybrid and fossil floodplain grasslands that species diversity may be preserved in the long term, as the P input is lower here than in the functional floodplain.

KW - Biology

KW - Cnidium dubium

KW - Cnidium dubium

KW - Land-use management

KW - Phosphate limitation

KW - Productivity

KW - River Elbe

UR - http://www.scopus.com/inward/record.url?scp=33645731415&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/d4443c84-7d0d-3438-ad78-8b4b3bf02961/

U2 - 10.1016/j.baae.2005.09.003

DO - 10.1016/j.baae.2005.09.003

M3 - Journal articles

VL - 7

SP - 280

EP - 288

JO - Basic and Applied Ecology

JF - Basic and Applied Ecology

SN - 1439-1791

IS - 3

ER -