No abstract

We tested the long-term effects of liming on soil micro-arthropods in a stand of Scotch pine on former drift sand in the Netherlands. To counteract the effects of acidification, liming was applied in increasing quantities from 0 (control), 3, 6, 9 and 18 ton ha −1 on experimental plots over the course of 1985 and 1986. Soil samples for chemical analyses and those for extraction of soil micro-arthropods were taken in October 2017, 32 years after application. Liming did restore the buffer capacity of the soil and did increase pH and increased plant biomass of the understory. Liming, however, also created P limitation, due to Al precipitation and an excess of free Ca to bind on. The consequence of the observed P limitation was a significant decrease in herbivorous and herbofungivorous micro-arthropods, whereas fungivorous and opportunistic herbofungivores were unaffected. P availability in acidified soils had become limited, due to higher N input that also caused acidification and due to remediation with added buffer material. Decomposition of organic matter was accelerated and increased N release to the system. The forest ecosystem had become P limited, where it originally was N limited or N and P co-limited.Biology and Fertility of Soils (2019) 55:675-683 https://doi.

Question: Which biogeochemical processes are responsible for the decline of endemic metallophyte vegetation in floodplain grasslands? Location: Floodplain grasslands along the River Geul (the Netherlands) and metalliferous mine spoils near the River Geul (Belgium). Methods: In order to find factors and soil processes that have caused a decline of metallophytes and an increase of pseudo‐metallophytes in floodplain grasslands, a soil study was done at locations currently and formerly dominated by metallophytes. In addition, changes in soil chemistry in recent decades in floodplain grasslands were investigated. Finally, a 2‐year plant growth experiment was performed in the field, to test the effects of improving soil conditions by topsoil removal. Results: Metallophytes only occur on acidic floodplain soils (pH‐H2O 5.0‐5.5) with relatively high Zn availability (total Zn >40 μmol g−1; Zn/Ca>0.8; Zn‐H2O>59 μmol kg−1) combined with low phosphate availability (Olsen‐P≪1250 μmol kg−1). The Olsen‐P and total Ca concentrations were relatively high in topsoil (0‐20 cm), while total Zn was high throughout the soil profile (0‐50 cm). Removal of topsoil led to recovery of P and Zn availability. Under the new soil conditions there was almost no growth and expansion of pseudo‐metalliferous grasses in time, wheras metallophytes easily established, maintained and reproduced with significant increases in cover over time. Conclusions: On a global scale, metallophyte vegetation types are increasingly under threat of extinction. Our study shows that factors leading to higher soil alkalinity inhibit Zn availability at the expense of the metallophyte vegetation. Factors leading to a higher Olsen‐P concentration stimulate the growth of more competitive pseudo‐metallophyte grasses. Both eutrophication and alkalinisation have contributed to the decline of metallophyte vegetation in floodplains of the River Geul. Removal of the alkaline‐ and phosphate‐enriched soil top layer restores the original soil chemistry and enables re‐colonisation by the metallophyte vegetation. The results can be applied in conservation and restoration strategies for such sites.

Questions: Which nutrient(s) limit(s) vegetation productivity in Calthion grasslands? Is phosphorus release a bottleneck for restoration of species-rich Calthion grasslands on rewetted dairy meadows? Location: Three species-rich Calthion grasslands in the Western Peat District in the Netherlands. Methods: We conducted a field fertilization experiment with nitrogen (N), phosphorus (P) and potassium (K) in three existing Calthion grasslands to evaluate the potential for restoration on rewetted dairy meadows. Responses of above-ground biomass, tissue nutrient concentrations and nutrient ratios were determined after 2 yr of fertilization. Results: Biomass increased with fertilization with Nonly and K-only but did not react to P-only additions. Comparisons of tissue nutrient concentrations and nutrient ratios also gave indications of N and K limitation. Conclusions: The strong P release expected after rewetting should not necessarily interfere with restoration of Calthion communities on rewetted dairy meadows. It is concluded that for successful restoration management measures should focus on reducing N and/or K availability. Potassium might be an overlooked bottleneck in the restoration of species-rich grasslands.