Many different ecological processes have been suggested to affect resilience of an ecosystem including functional trait redundancy. Contingent trait redundancy can provide an ecological contingency plan in which underlying mechanisms allowing for ecosystem and community function to be achieved through various trait combinations in unique species. However, a knowledge gap exists in understanding how global change drivers affect contingent trait redundancy, thereby affecting temporal community stability (ratio of mean abundance to standard deviation resulting from temporal variation in abundance) and ecosystem disturbance response. Models have shown that by 2050 rates of nutrient inputs are expected to increase in coastal systems, making it critical to better understand the effects nutrient additions have on community structure and function. Our objective was to investigate effects of nutrient deposition on functional diversity and redundancy. Furthermore, we were interested in linking functional metrics to community productivity. We established nitrogen (N), phosphorus (P), and reference (R) plots in a full factorial design, producing 4 groups (N, P, R, and NP). Plots were fertilized twice annually, while annual net primary production (ANPP) and species composition were quantified once per year. We hypothesize that nutrient additions, particularly N and NP, will affect feedbacks between growth strategies, such that trait diversity will correlate with higher community productivity, suggesting limiting niche similarity.
Results/Conclusions
Our data show that nutrient addition affected functional diversity but not functional redundancy of plant communities. Functional diversity was higher in N and NP plots than reference plots (P < 0.05). Furthermore, we found that there was significantly higher biomass production in N and NP plots compared to reference and P plots (P < 0.05). This suggests that N and NP enrichment may drive feedbacks between productivity and functional diversity. In plots with the highest productivity, functional diversity was also highest, limiting niche similarity, thereby promoting competition avoidance. Barrier islands systems are highly stressful and ecosystem functional relies on stress tolerant trait values. If increased N and NP deposition causes higher functional diversity, subsequently shifting traits to utilize alternative niches, disturbance response of communities may be altered as global change drivers accelerate effects of climate change in barrier island systems.