1. Jan Leps, Dept of Botany, University of South Bohemia, České Budejovice, Czech Republic
Biotic and abiotic effects on species and functional trait composition: lessons from a grassland experiment with dominant removal

2. OHRAZENI – a seminatural meadow
Regular mowing ceased in late eighties

3. Nardus stricta
Molinia caerulea

4. Species diversity and “interesting plants” (e. g
Species diversity and “interesting plants” (e.g. red list species) concentrated in “traditional”, i.e. mown, unfertilized
Dactylorhiza majalis
Senecio rivularis

5. 14 Carex species
Carex pulicaris C. hartmanii

6. Scorzonera humilis

7. Myosotis nemorosa

8. Factorial experiment, 3 replications
Mowing (once a year, in June)
Ferilization (65 [50] g of commercial NPK/m2 - 12% N (nitrate and ammonium), 19% P (as P2O5) and 19% K (as K2O))
Dominant (i.e. Molinia caerulea) removal (in spring 1995, but re-weeding necessary time from time)
Yielding 24 plots, 2m × 2m each
Central 1m x 1m sampled, followed by detailed analysis of 50cm × 50cm grid of 10cm × 10 cm – including seedling counts
Experiment started 1994, baseline data available

9. Ohrazení (http://mapy.atlas.cz)

10. Detailed recording of vegetation in all the 15 years
Sprouts of woody plants removed

12. Today, I want to demonstrate
General pattern of species composition changes
Scale dependence of changes in species richness
Importance of species trait for the species response to treatments
Effect of single species on various community processes/functions

13. Error bars =95% confidence intervals
Problem for interpretation, in later years, Molinia removal would have little effect in fertilized mown (as it have very low cover also in the control plots)

14. Species composition

15. DCA - Molinia is passive species - log transformed cover.
Starting points in 1994 show the random variability - the divergence of trajectories show the differentiation according to treatments between 1994 and 2007.
Centroids of Year x Treatment

16. Principal response curves
triangles - mown circles unmown
full symbol - fertil. open symbol - unfert.
solid line - control broken l. - removal

17. Principal response curves
Multivariate counterpart of Repeated measurement ANOVA - the first RDA axis, which is plotted on vertical axis against the time (horizontal axis), captures the main differentiation among categories of YEAR * TREATMENT interaction
The common temporal trend is subtracted from the data - YEAR as covariable(s)
The horizontal axis corresponds to the control (in our case, unmown, unfertilized, no removal)

18. Principal response curves
triangles - mown circles unmown
full symbol - fertil. open symbol - unfert.
solid line - control broken l. - removal

19. Mown - unfertilized (=traditional)

20. Mown - unfertilized & Molinia removed

21. Mown - fertilized (=intensive)

22. Mown - fertilized & Molinia removed

23. Unmown - unfertilized (=abandoned)

24. Unmown - unfertilized & Molinia removed

25. Unmown - fertilized (=abandoned eutrofized meadow)

26. Unmown - fertilized & Molinia removed

27. Species richness

28. In mown plots, increase of the number of species during first six years, regardless of removal of Molinia, in unmown plots, removal has positive effect on species richness. NB. – Molinia is thread only in unmown plots!
NSP of vascular plants per m2

29. In unmown plot, continuous decrease
In unmown plot, continuous decrease. Initial positive effect of removal ceased after 10 yrs. In mown plots, initial increase (5 years) followed by decrease, no effect of removal.

30. Take home message
Increase in soil nutrients can lead to competitive exclusion - nevertheless, in community of established perennial plants, the exclusion can take rather long (six years in our case).
Mgmt recommendations based on short term experiments can be misleading

31. Species richness dynamics depends on spatial scale
Repeated measures ANOVA
3 main plot factors (Mowing, Fertilization, Removal)
2 Rep Mes factors – year and plot size (from 10x10cm2 to 50x50cm2)
Number of species log transformed – i.e. relative change of the richness
Very long ANOVA table, with many significant interactions

32. Unmo
Mown
U n f e r t i l i z e d
F e r t i l i z e d

33. During the first eight years, number of species increases on small plots, but is constant on larger plots

34. Positive effect of mowing is most pronounced on the small spatial scale
50x50
Data from 2008, averaged over fertilization and removal treatments
10x10

35. The species lost from the community under various management types
Are not a random subsample, but species with specific ecological traits (contrary to Hubbell’s neutral theory)
IMPORTANCE OF SPECIES TRAITS
(mostly based on 2004 biomass data)

36. Species based approach to trait response to environment
1. Calculate the environmental response for each individual species (we have used constrained ordination framework / RDA)
2. Predict the species response on the basis of species traits (various regressions, regression trees)

37. Species response to fertilization (RDA score, positive values mean that the species gains from fertilization)
Cirsium palustre

38. Potential height is good predictor of response to fertilization and mowing
With increasing nutrients, the plants are released from competition for nutrients, but simultaneously, the importance of competition for light increases - the taller plants are in advantage.
The taller plants are harmed more by mowing
Higher asymmetry of competition for light (in comparison with competition for nutrients) explains decline in species richness.

39. The role of the dominant (Molinia caerulea)
consequences of its removal

40. Litter - Molinia produces large amount of slowly decaying litter
Litter - Molinia produces large amount of slowly decaying litter. Its removal causes decrease of litter amount (with exception of mown & fertilized conditions)
As a consequence, seedling recruitment is supported by Molinia removal.
Molinia competes also after its death.

41. Seedling number - Averaged over 1996-2007

42. In the presence of Molinia, the peak of biomass is shifted from June to August (and is slightly higher) - only weak statistical support
Unfertilized plots only shown
The presence of a single species can considerably shift the seasonal biomass dynamics

43. In mown plots, the removed Molinia is replaced by other grasses, however, there is no other grass which would be able to replace Molinia in unmown plots.
Take home message: The dominant species (when removed) is not always replaced with the species from the same functional group.

44. Thanks for money
Czech Science Foundation (GACR)
Framework V – VISTA project
Thanks for the help
Iva Spackova, Alena Vitova, Petr Macek, Francesco de Bello, Jiri Dolezal, Vojtech Lanta, Jonathan Titus, Eva Chaloupecka, Katerina Palkova, David Zeleny

45. Thank you for your attention

46. Two approaches to analyse species trait response
Species based: can we predict the species response on the basis of its traits?
Traits are predictors of species response (trait value is a fixed characteristics of individual species)
Community (plot) based: how do the community (weighted) average [or variability] respond to environmental characteristics?
Traits (averages, variability) are response. Trait plasticity can be evaluated

47. Community (plot) based approach
1. Calculate the plot composite characteristics (proportions of functional groups, weighted averages of quantitative traits)
2. Analyse the composite characteristics by univariate (ANOVA) or multivariate (RDA) methods

48. Changes in proportions of four “functional” groups
Grasses
Other graminoids (mostly sedges)
Forbs (other than legumes)
4. Legumes (not very common in our plots)

49. Methodological note 1
Regression tree – highly non-parametric regression approach
Well designed to account for the non-additivity
The tall plants are always harmed by mowing
In a group of “not so tall” plants, also other factors play a role: e.g. those with a rosette respond more positively

50. Methodological note 2
Species based approach – species are considered independent observations – problem of phylogenetic relatedness
Do we need phylogenetic correction?
To which extend could be the similarity of species responses explained by the similarity of their traits, and to which extend by the phylogenetic relatedness?

51. RDA, additive effects of treatments (no interactions)
Proportion of four (functional?) groups in various treatments.
Grasses supported by both, mowing and fertilization

52. RDA - “species traits”
(treatment specific)
Additive effects

53. Separating the effect of species composition and plasticity
Plants in fertilized plots could be taller than in unfertilized either because
The species composition changed in favor of genuinely taller plants (Prunella vulgaris was replaced by Holcus lanatus)
The species composition does not change, but the same species grow taller in fertilized plots
Combination of the two

54. Vegetative height

55. Over all the traits
For the change in species composition (i.e. for fixed traits), mowing is more important, whereas for the plastic response (i.e. for specific values and for the interaction), the fertilization is much more important. I.e. fertilization changes traits of individual species, mowing is a selection force, discriminating according to species traits

56. Univariate analyses with individual traits
The community based approach (i.e. weighted averages) resulted more frequently in significant results
It is easier to predict what will be the prevailing traits in the community, than to predict, how will individual species behave

57. Individual RDA analyses
Individual RDA analyses. Note, that in CANOCO, RDA is scaled so that the total variability (before subtracting the effect of covariables) equals 1. M – mowing, F –Fertilization, S – specificity (i.e. fixed vs. specific values). * means interaction.
Analysis no.
Response
Explanatory variables
Covariables
Variability after subtracting covariables
Variability explained by the explanatory variable(s) F P 1
Fixed
M, F -
1.000
0.423
3.293
0.004 2 M
0.833
0.255
3.978
0.012 3
0.745
0.167
2.609
0.022 4
Specific
0.547
5.431
0.002 5
0.593
0.139
2.767
0.046 6
0.861
0.408
8.095 7
All
M*S, F*S
plot ID, S
0.163
0.130
17.483 8
M*S
plot ID, S, F*S
0.063
0.030
7.979 9
F*S
plot ID, S, M*S
0.134
0.100
26.987