Relationships between plant functional traits and short-term leaf litter decomposition in 16 plant species native to British Columbia

Background/Question/Methods

Plant functional traits in green foliage have been shown to influence rates of litter decomposition, demonstrating an “after-life effect” of functional traits on ecosystem processes. Chemical traits, such as foliar nutrient content, have historically been studied more extensively in the context of decomposition than physical traits such as specific leaf area (SLA) and leaf toughness, which impart information on litter structure and accessibility to decomposers. This study is intended to explore relationships between physical functional traits and litter decomposition in 16 plant species native to British Columbia, including two herbaceous plant species, nine coniferous tree species, and five broadleaf tree species. Physical traits measured in green foliage samples of each species include SLA, dry matter content, leaf thickness, toughness expressed as force-to-punch, and cuticle thickness. SLA, thickness, and toughness were also measured in litter, along with leaching loss and water uptake rates after 2 and 24 hours. Percent carbon and nitrogen and pH were measured in both green foliage and litter. Decomposition, as net mass loss over time, was measured using litterbags installed in a temperate rain forest at the University of British Columbia farm in Vancouver. Subsets of litterbags were collected after 6 weeks and 3 months. 

Results/Conclusions

After both time points, we found significant positive correlations between percent mass remaining and the natural logarithm of specific force-to-punch (Fp_s) of green foliage (r  = 0.70 and 0.54 respectively, p < 0.001, n = 80). Significant, positive correlations were also found between percent mass remaining and the natural logarithm of Fp_s of air-dried litter (r = 0.64 and 0.65 respectively, p < 0.001, n = 80). Percent N in green foliage (square-root transformed) was significantly, negatively correlated with percent mass remaining after 3 months (r = -0.31, p < 0.006, n = 80). These results suggest that leaf toughness plays an important role in early stages of decomposition, illustrating an after-life effect of functional traits thought to be involved in nutrient retention and herbivore defense on ecosystem processes. Litter nutrient quality may be more influential in later stages of decomposition. The experiment will continue for 3 years.