The effects of leaf litter species diversity on decomposition in a forested watershed

Becky A. Ball, Mark A. Bradford, David C. Coleman, Mark D. Hunter, John S. Kominoski, Catherine M. PringleInstitute of Ecology, University of Georgia, Athens, GA 30602

Introduction:There is currently much debate about the effect of species diversity on ecosystem functions, and many theories exist about the relationship between the two. For decomposition, no clear patterns have emerged (see Hättenschwiler et al. 2005, Gartner and Cardon 2004), though an idiosyncratic relationship is commonly found. Such results likely arise due to the way in which diversity is defined. Species diversity can be defined by species richness (the number of species involved) and composition (the identity of species involved). Composition can be further defined as having additive effects (where a mixture reflects the average of the species involved) and non-additive effects (where mixture behaves differently than would be expected by the average). In order to separate richness and composition when researching species diversity, a full factorial design is necessary. This project utilizes a full factorial design to determine the effects of leaf litter species diversity on decomposition and nutrient cycling in a forested riparian zone in the southern Appalachians.

Questions:1. Is there a significant effect of species richness on decomposition?2. Is there an effect of species composition on decomposition? If so, is it

additive or non-additive?3. What does this tell us about nutrient cycling?

Methods:• Site: Lower Ball Creek, Coweeta Hydrologic Lab, Otto, NC• Leaf Species: Liriodendron tulipifera (L), Acer rubrum(A), Quercus

prinus (Q), Rhododendron maximum(R)L LA LAQ LAQRA LQ LARQ LR LQRR AQ AQR

AR QR• Litterbag method to study decomposition over 3 years• Assays:

• AFDM (k rate)• C:N:P• Phenolics

-Total phenolics-Condensed tannins-Hydrolysable tannins

Acknowledgements:•NSF Award #0218001

•Coweeta LTER•Institute of Ecology Graduate Students and undergraduate work-study students

•Institute of Ecology Analytical Lab•Dr. Keller Suberkropp, University of Alabama

Lower Ball Creek, November 2003

J. Kominoski

Results:

Decay rate:

Mass loss:

Chemistry:

Discussion:•Mass Loss

•No significant effect of richness on mass loss •No significant non-additive effect of composition on mass loss•There are additive interactions based on the presence or absence of certain species

•Chemistry• No significant effect of richness on chemical properties of litter• It is composition for which we see significant effects, being non-additive for the nutrients N and P.

•Implications•There are possible effects of litter diversity (through composition) on nutrient movement, both additively and non-additively.•Species identity has a significant impact in this forested system.

•Fiber-Cellulose-Hemicellulose-Lignin

•Fauna-Bacteria (DAPI)-Fungi (Ergosterol)-Nematodes-Arthropods

Literature Cited:Hättenschwiler et al. 2005. Ann. Rev. Ecol, Evol and Syst. 36:191-218.

Gartner and Cardon. 2004. Oikos 104:230-246.

0.0006

0.0007

0.0008

0.0009

0.001

0.0011

0.0012

0.0013

1 2 3 4

Species Richness

k d

ay -1

P = 0.61

51

52

53

54

55

56

57

58

59

60

61

L A Q R

Species

% A

FD

M R

em

ain

ing

present

absent

* **

0

10

20

30

40

50

60

70

80

90

0 6 12 18 24 30

Time (months)

C:N

Rat

io

1 sp

2 spp

3 spp

4 spp

Composition P = 0.00Composition * time P = 0.46

Richness P = 0.31Richness * time P = 0.97

35

40

45

50

LAQ LAR

Composition

C:N

Ratio together

not tog

* *

1.00

1.10

1.20

1.30

1.40

LAQ AQR

Combination

% N together

not tog

*

*

0.04

0.05

0.06

0.07

LAQ AQR

Combination

% P

together

not tog

*

*

Richness P = 0.41Composition P = 0.00

Richness P = 0.73Composition P = 0.04

•Full factorial ANOVA explores effect of composition and richness independent of the presence/absence of each species

Richness P = 0.61Composition P = 0.98