Restoration of species-rich heaths and matgrass swards. Roland Bobbink B-WARE Research Centre & Landschaps Ecology, UU.

Transcription

1 Restoration of species-rich heaths and matgrass swards Roland Bobbink B-WARE Research Centre & Landschaps Ecology, UU.

2 Outline presentation Introduction - heathland landscape; - species-rich heaths & matgrass swards - causes of the degradation Ecological restoration - dry heaths and matgrass swards - wet heaths and matgrass swards Conclusions & perspectives

3 Dry heath (acid, ph )

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5 Dry Nardo-Galion (ph 4.5-6)

6 Species-poor wet heath ph 4,0-4,5

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8 Species-rich wet heath ph 4,5 5,5

9 Wet Nardo-Galion (ph )

10 Wet heath Dry heath Dry, Nardo- Galion = groundwater level = confined layer //////////////// = loamy material //////////////// Wet, Nardo- Galion ////////////////////// Scheme of the Dutch heathland landscape

11 Important considerations before Ecological Restoration : History of the degraded ecosystem Cause(s) of the degradation (key processes) Present-day situation (vegetation, soil, fauna) --> indication Control of threats!! Adequate management after restoration (semi-natural vegetation)

12 Sensitivity for degradations in the heathland landscape: Many systems (very) sensitive to Acidification (very weakly buffered waters & dry species-rich Nardo-Galion communities) Almost all systems also sensitive to Eutrophication some parts of the landscape (very) sensitive to Desiccation (softwater lakes; wet heaths & wet Nardo-G)

13 Overview effects of Acidification (loss of ANC) (dependent of original buffer capacity):

14 Cation-exchange prosesses (base saturation) Ca 2+ - Ca Ca Mg 2+ Ca 2+ clay Ca Ca 2+ Ca 2+ Ca 2+ - Ca H clay + 2H + Mg 2+ Ca 2+ + Ca 2+ Ca Ca 2+ Ca 2+

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16 Acidsensitive soils in the Netherlands:

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18 Effect N-fertilisation on Molinia biomass above-ground DW (g) C N-deposition (kg ha -1 year -1 ) inflorescens leaves Effect N-fertilisation on Cladonia coverage 50 coverage (%) C N-deposition (kg ha -1 year -1 )

19 30 Dry acidic grasslands UK (Stevens et al. 2004) Mean number of species per quadrat Total Inorganic Nitrogen Deposition (kg N ha -1 yr -1 )

20 Ammonium toxicity

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22 Survival Antennaria (interaction ph & NH4) Ant e nnar i a 100, 00 90, 00 80, 00 70, 00 60, 00 50, 00 40, 00 30, 00 ph NH t i m e ( w e e k s )

23 Desiccation, lowering of the groundwater table

24 Unfortunately, many wet heaths (>1980s):

25 Early phase sod cutting of dry, acid heaths (1987)

26 And 6-8 years years after sod cutting (Calluna vulgaris) (but species poor)

27 Restoration of formerly species-rich dry Nardo-Galion communities after NUTRIENT ENRICHMENT: Aim: rehabilitation of NUTRIENT-POOR soil conditions; adequate establishment conditions

28 Sod cutting (without the removal of relict populations!!)

29 Increase of Arnica montana number of rosettes ph: ;<10m ph:3,8;>8m

30 Havelterberg

31 Restoration of formerly species-rich dry Nardo-Galion communities after SOIL ACIDIFICATION: Aim: rehabilitation of WEAKLY BUFFERED (and nutrient-poor) soil conditions; adequate establishment conditions

32 Liming after sod cutting (1990)

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34 Arnica montana control marl dolokal germination survival germination + survival (%)

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36 Restoration Dry Nardo-Galion communities Conclusions after years of rehabilitation measures: Acidified: sod cutting (except rest populations of RL-species) & liming Eutrophied: sod cutting (except RLspecies)

37 BUT: Recovery seriously limited if the endangered species already disappeared before restoration CAUSES: non-persistent seed bank restricted dispersal capacities in higly fragmented landscape NEEDS: Re-introduction of endangered species

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39 Experimental re-introduction Arnica (1997) (6 jaar after first restoration) (old locations) K iemingspercentage voorjaar najaar Borkeld Holtherzand

40 Survival percentage Arnica (second/third year ) O verlevingspercentage zaden voorjaar zaden najaar kiemplanten voorjaar kiemplanten najaar

41 Restoration of degraded wet species-rich Heaths and Nardo-Galion communities: Aim: rehabilitation of WEAKLY BUFFERED (and nutrient-poor) soil conditions; appropriate hydrology adequate establishment conditions for typical and endangered species

42 Restoration of formerly species-rich Heaths or Nardo-Galion with hydrological measures

43 Just after sod cutting and hydrological measures:

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45 Period : Red List plant species!! Typical vegetation developed; species-rich (seepage zone)

46 BUT still some constraints in restoration present: When the groundwater/seepage has been acidified --> only return of species-poor heath/grass communities (new approach: Catchment liming) ammonium accumulation after sod cutting (low ph)

47 Sod cutting in degraded wet heaths (Dorland et al. 2003) Geplagd Controle Concentratie NH 4 + ( mol kg -1 droge bodem) apr-00 jun-00 aug-00 okt-00 dec-00 feb-01 apr-01 jun-01 aug-01

48 Mechanism: Inhibation of Nitrification Wet Nardo-Galion ph 5,5 Acidified Molinia ph 4,3 Potential net NO 3 - production (µmol g -1 dry soil) a 0-5 cm Control b c cd d 6-10 cm Control 0-5 cm Acidified 6-10 cm Acidified Sod-cut

49 Solution: sod cutting + liming NH4 (µmol kg -1 dry soil) Control Sod-cut Sod-cut + lime ** *** ** 0 sep-01 nov-01 jan-02 mrt-02 mei-02 jul-02 sep-02 nov-02

50 3.5 yrs after sod cutting & liming Number of species m Non-target Characteristic Endangered * 0 HO Sod-cut HO Sod-cut + lime LP Sod-cut LP Sod-cut + lime

51 BUT most disappeared RL-species do not return: (a) Erica tetralix (c) Molinea caerulea Number of seeds m-2 Number of seeds m Depth (mm) Depth (mm) (d) Juncus spec. Number of seeds m Depth (mm)

52 Complex of several vegetation types : Moorland pools Species-rich wet heaths and matgrass swards Species-poor poor dry heaths

53 Catchment Liming: Zuur regenwater Dolokal Ca 2+, HCO 3 - Natte heide Bodem Ondoordringbare laag Ven

54 ph soil - water layer 6.5 Schaopedobbe Catchment liming High (limed) Middle Low Pool

55 97-post '00 '01 '02 '03 97-pre 97-post '00 '01 '02 '03 97-pre 97-post '00 '01 '02 ' Base cations soil High - limed Middle - not limed Low - not limed Schaopedobbe Ca Mg K 97-pre millimol kg -1 dry soil

56 Buffercapacity water layer Schaopedobbe Bieze eq L Catchment liming

57 Wet heath vegetation 9 8 High - limed Middle - not limed Low - not limed Schaopedobbe 7 Number of species m Red List spec. Characteristic spec. Other spec.

58 Conclusions & perspectives Sustainability of restoration high - much lower depositions! Mostly combined measures necessary and succesfull: - recovery of buffer capacity & - removal accumulated nutrients - rather complete plant communities developed Dispersal problems in fragmented NL

59 Thanks to: Maaike de Graaf (RU) Edu Dorland (UU) Leon van den Berg Jan Roelofs and all owners of the investigated Nature reserves!!!