Seed addition outweighs soil fertility reduction in restoration of species-rich grasslands on ex-arable land at Assel, Gelderland, the Netherlands
Published Source
Kardol P., Wal A.V. , Bezemer T.M., Boer W., Duyts H., Holtkamp R. & Putten W.H.V. (2008) Restoration of species-rich grasslands on ex-arable land: Seed addition outweighs soil fertility reduction.
Biological Conservation, 141, 2208-2217 (added by: Showler D.A. 2010).
Background
Within a European context, on abandoned agricultural land targeted for semi-natural species-rich grassland creation, high soil fertility and limited natural plant dispersal ability are considered major constraints to restoration success. Often soil fertility reduction is deemed necessary for establishment of desired plant communities. A 3-year experiment was conducted on an ex-arable sandy soil site at the village of Assel, Gelderland (52°21′N, 5°82′E), the Netherlands. Effects of soil fertility manipulations and sowing native mid-successional plant species on plant community development and soil biological properties were assessed.
Action
After abandonment in 2002, in May 2004 four blocks (5 m apart) each containing eight plots (4 x 4 m, 3 m apart), were established. Treatments applied were: control, wheat Triticum spp. straw addition, birch Betula pendula wood chip addition (to incorporate plant-available nutrients), and top soil removal (to reduce nutrients).
Treatments were applied with or without sowing of characteristic mid-successional perennial species of abandoned cropland in the region: a mix of four grasses (common bent Agrostis capillaris, sweet vernal Anthoxanthum odoratum, quaking grass Briza media, sheep’s fescue Festuca ovina; 500 seeds/m2) and four forbs (yarrow Achillea millefolium, cat’s-ear Hypochaeris radicata, ribwort plantain Plantago lanceolata, common sorrel Rumex acetosella; 150 seeds/m2).
In July/August 2004, 2005 and 2006, percentage cover of each vascular plant species was recorded (inner 2 x 2 m of plot), and standing biomass determined by clipping subplots. In May 2004, 2005 and 2006, soil samples were collected from each plot, soil parameters were analysed, bacterial and nematode abundance and root biomass (2005 and 2006) determined.
A microcosm study was also undertaken to assess short-term effects of soil fertility reduction on biomass production of the sown species.
Consequences
Contrary to expectations establishment of the sown plant species was better without soil fertility reduction (i.e. topsoil removal). Whilst the sown species all established, topsoil removal reduced establishment success (reduced biomass) and created a ‘desert-like environment’, although it effectively suppressed arable weeds. Adding straw or wood resulted in short-term plant biomass reduction (suggesting decreased available nutrients).
Topsoil removal also greatly reduced bacteria and nematode abundance, and fungal biomass, but straw and wood addition had little effect. On average, in top soil removal plots bacterial numbers were 2-fold and fungal biomass was 14-fold lower.