1. Above and Below ground decomposition of leaf litter Sukhpreet Sandhu

2. Introduction Litter decomposition is one of the key biogeochemical processes in forest ecosystems Estimated that nutrients released during litter decomposition account for 69-87% of the total annual requirement of essential elements for forest plants The rate of litter decomposition is largely a determining factor for productivity or biomass of every terrestrial ecosystem in general, and of forest ecosystems in particular.

3. Introduction Most multitrophic studies have been almost exclusively focused on above ground interactions, generally neglecting the fact that above- and below ground organisms interact Most multitrophic studies have been almost exclusively focused on above ground interactions, generally neglecting the fact that above- and below ground organisms interact Combining both above- and below compartments in studies of multitrophic interactions will improve our understanding of ecology and evolution of the real world (Putten et al 2001).

4. Objective  To study if litter decomposition differ with its placement on or below the surface? Hypothesis   There should be no significant difference between above and below ground decomposition.

5. Methods Collection of litter- A leaf litter decomposition experiment was carried out during a 5 week period from February 18 to Mar 24, 2004 Entire leaves of Sapium were harvested directly from adult trees, just before abscission and air dried for about 30 days Entire leaves of Sapium were harvested directly from adult trees, just before abscission and air dried for about 30 days

6. Methods Litter Bag Technique Leaf decomposition evaluated with litter bag technique (Swift and Anderson,1989) Mesh bags 12x15 cm in size with 2 mm mesh were filled with about 2g of air dried leaf litter of Sapium. Each sample was weighed separately and it was recorded as the initial weight Mesh bags 12x15 cm in size with 2 mm mesh were filled with about 2g of air dried leaf litter of Sapium. Each sample was weighed separately and it was recorded as the initial weight

7. Experiment Layout Decomposition study carried out on forest floor of the Natural Ecosystem Teaching Lab. The litter bags were laid according to three time points viz 7days, 21days and 35days Each time point had 5 spatial replicates for above ground decomposition and 5 replicates for below ground decomposition Each time point had 5 spatial replicates for above ground decomposition and 5 replicates for below ground decomposition For the study of below ground decomposition, the litter bags were placed at a soil depth of 8-10 cm

8. Decomposition Study The litter bags collected at their respective sampling date and weighed to get the final weight Decomposition was measured by rate of mass loss and fitted with an exponential decay function to estimate the decomposition rate (k) Decomposition was measured by rate of mass loss and fitted with an exponential decay function to estimate the decomposition rate (k) The percent of the initial mass remaining was plotted against time (days)

9. Carbon and Nitrogen Analysis The oven dried litter samples, were milled Weighed 3mg and rolled in tin cups for the carbon and nitrogen analysis in CHN analyzer Peach in range from 0.5 mg to 3mg was used a standard for this purpose. Peach in range from 0.5 mg to 3mg was used a standard for this purpose. A decay constant was estimated for % carbon and %nitrogen.

10. Statistical Analysis One-way ANOVA used to examining the differences in treatment means in the proportion of original mass, carbon or nitrogen remaining at various times Additional comparison of means using Tukey’s test Fitting decay functions to mass values using the single exponential model

11. Statistical Analysis Simple linear regression analysis was further done with decay constant (k-1days) as dependent variable and percent initial mass, carbon and nitrogen remaining as the independent variable. R 2 value thus obtained gave an estimate of the goodness of fit of these parameters, as predictors of decomposition rate

12. Dynamics of % mass lost in above & below ground litter samples

13. Percent Initial Mass Remaining DAYSABOVEBELOW F- value P- value 7 B 78.1 ± 2.1 A 87.3±3.6 24.810.001 21 A 76.5± 2.6 A 76.0±3.8 0.060.81 35 A 69.8±3.7 A 67.8±5.6 0.490.50

14. Dynamics of % carbon lost in above & below ground litter samples

15. Percent Initial Carbon Remaining DAYSABOVEBELOW F- VALUE P- VALUE 7 79.7±5.5 86.8±4.6 4.80.06 21 78.4±6.3 73.8±4.0 1.90.205 35 70.3±1.9 65.0±5.1 3.10.114

16. Dynamics of % nitrogen lost in above & below ground litter samples

17. Percent Initial Nitrogen Remaining DAYSABOVEBELOW F- VALUE P- VALUE 7 B 78.9±2.9 A 93.5±3.7 47.740.0001 21 A 83.7±7.9 A 90.9±4.8 3.10.1168 35 A 84.6±4.7 A 82.5±8.0* 0.250.629

18. C/N ratio of above and below ground samples during decomposition

19. Decay constant comparison of % mass, %C and %N lost

20. Conclusions Below ground samples show a more gradual constant decomposition, compared to above ground samples Above ground samples show a rapid decline in %mass, then a leveling off at 21 days, this is the same trend as in C/N ratio After a rapid decline in %N, the above ground samples show some net N accumulation, may be due to insect frass, throughfall, N fixation, absorption of atm NH 3, fungal absorption &/or immobilization

21. Conclusions Above ground show initial large decrease in N, due to which the C/N does not decrease to the same extent in above ground, as in below ground Hence, the decomposition of above ground samples decreases between 7 and 21 days Although beginning slowly, below ground samples, ultimately show the same amount of %mass, % carbon and % nitrogen after 35 days

22. Conclusions Lower C/N and high N correlates to higher microbial activity, and consequently, a higher decomposition rate for the below ground samples C/N is good predictor of decomposition Decomposition rates of above and below samples,may or may not be significantly different

23. Conclusions Overall good exercise to understand the basic decomposition processes and the role of, N, C/N in decomposition and how the availability of N affects the rate of decomposition and how above and below ground compartments interact

24. Improvements Increase the decomposition period to atleast 3 months Place samples at different sites as well Statistical analysis, using split-plot design, to study the interaction between time and placement