Presentation on theme: "Soil biodiversity and nutrient cycling in rich fens New prospects in Restoration ecology ? Rolf Kemmers Bas van Delft, Miki Madaras, Ab Grootjans."— Presentation transcript:
Soil biodiversity and nutrient cycling in rich fens New prospects in Restoration ecology ? Rolf Kemmers Bas van Delft, Miki Madaras, Ab Grootjans
Problem: Natural vegatations affected by drainage, acidification and eutrophication Restoration efforts directed to amelioration of abiotic conditions Effects: Some times manifest Frequently retarded, transient or ambiguous ! Questions: Did we tune the right buttons ? Why should soil organisms not suffer from env. stress as well ? Did we fuel the car leaving the batteries unloaded ? Is plant biodiversity linked to diversity of soil organisms ? Introduction
1. Acidification of a Dutch rich fen Changed N-availability and plant productivity/biodiversity Two cases: 2. Declined rich fens (NL) compared to calcareous fens (SLK) Changed P-availability and plant productivity/biodiversity
Case 1 Reference of an ‘undisturbed’ rich fen Well buffered homogenized humus profile: Mull ‘Optimal’ conditions Acid-buffer supplied by seepage water (pH 5.5) Active soil fauna (earthworms) High microbial nutrient demand: N-immobilisation C/N: 16 Nr. of species/4m 2 :22 g/m 2 Crop production:375 N-yield: 4,3 N-min: 2,8 Ahg ACg
Case 1 Acidification and decrease of acid buffering capacity development of a stratified humus profile lime ion-exchange aluminum Ca-saturation = 60% pH-H2O = 6 Ca-saturation = 20% pH-H2O = 4.5
Case 1 Acidified and stratified humus profile: Moder Acid-buffer depleted (pH decreased) Earth worm activity decreased Accumulation of organic matter Low microbial nutrient demand Increased C/N ratio’s Nr. of species/4m 2 : g/m 2 Crop production: N-yield: 4,3 6,2 N-min 2,8 5,1 C/N
Conclusions case 1: A shift from N-immobilisation to net N-mineralisation is associated with cessation of earth worm activity A >> Hypothesis: A healthy earth worm population supports microbial N- immobilisation and supports mesotrophic conditions
Case 2 Declined rich fens (NL) and calcareous fens (SLK)
Case 2 Phosphorus behaviour in calcareous fen Theory: Inorganic P is bound to Ca, Fe - or Al-oxides However: No correlations between inorganic P and Ca or Fe Despite high content CaCO 3 and (Fe+Al) ox hardly any inorganic P bound and P organically bound !
Case 2 Phosphorus behaviour Slowak fens (SLK) compared to 10 (best preserved) Dutch fens (NL) NL higher anorg. P fraction SLK higher org. P and extremely low C/P ratio’s (C/P < 50) Upon acidification decreased humification
Case 2 Phosphorus behaviour Results suggest that: Under wet conditions P is immobilized by microbes through (anaerobic) humification Upon drainage and oxidation acidification will occur P will be released by decomposition and mineralisation and Taken up by vegetation or Excess will be bound by Ca, Fe or Al (what we see in NL) A shift from organic bound P to inorganic bound P occurs during degradation
What do we learn from these cases ? Microbes are of main importance in controlling low levels of plant available nutrients by immobilisation in pristine calcareous fens Microbes are outcompeting plants for nutrients and are playing a key role in maintaining primary production at a low level A divers food web of soil organisms (browsers, grazers and predators) is controlling nutrient cycling and availability in soils
Hypothesis Plant biodiversity is controlled by soil biodiversity Conclusion: In restoration ecology we are fueling the cars by amelioration of abiotic conditions, but indeed we left the batteries unloaded by ignoring soil fauna as the main driving force of nutrient cycling. So: Future restoration efforts should focus on soil biodiversity !