Soil biodiversity and nutrient cycling in rich fens New prospects in Restoration ecology ? Rolf Kemmers Bas van Delft, Miki Madaras, Ab Grootjans
Dec 14, 2015
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/4m2 : 22
g/m2
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
3
4
5
6
7
0 25 50 75 100
Ca-saturation
pH
-H2
O
lime
ion-exchange
aluminumCa-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/4m2 : 22 13g/m2
Crop production: 375
490N-yield: 4,3 6,2N-min 2,8 5,1
C/N
37
20
14
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
1. (Pot)wormen
2. Microben
NH4+ min.1. (Pot)wormen
2. Microben
NH4+ min.
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 CaCO3 and (Fe+Al)ox
hardly any inorganic P bound and
• P organically bound !
0
1
2
3
4
5
0 25 50 75 100
CaCO3 (%)
PH
Cl (
mm
ol/k
g)
0
2
4
6
8
10
0 200 400 600 800 1000
Fe+Al (mmol/kg)
Po
x (m
mo
l/kg
)
0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8 9 10 11
Sites
Pa
n/P
tot
(%)
Case 2 Phosphorus behaviourSlowak fens (SLK) compared to 10 (best preserved)
Dutch fens (NL)
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0 100 200 300 400
P-tot (mg/100g)
Pa
n/P
tot
NL
SLK
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0 500 1000 1500 2000
C/P
Pa
n/P
tot
0
500
1000
1500
2000
2500
3000
0,0 2,0 4,0 6,0 8,0 10,0
pH-KCl
C/P
• 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 behaviourResults 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 !