ARS | Publication request: Comparing native and exotic litter decomposition and nutrient dynamics.

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 20, 2010
Publication Date: June 4, 2010
Repository URL: http://ddr.nal.usda.gov/bitstream/10113/45049/1/IND44411517.pdf
Citation: Martin, M.R., Tipping, P.W., Reddy, K.R. 2010. Comparing native and exotic litter decomposition and nutrient dynamics. Journal of Aquatic Plant Management. 54:307-315.

Interpretive Summary: Melaleuca quinquenervia is one of the most problematic invasive species in Florida Everglades’ ecosystem. This exotic tree has colonized and thrived in most natural areas of South Florida including the Pinus elliottii -Taxodium distichum ectone forest. Mechanical, chemical, and biological control programs have contained the spread and largely eliminated the invasive potential of existing M. quinquenervia populations. However, live non-invasive trees remain a part of the vegetative landscape and are targets for future management. Treatment of these populations has been justified in part by hypothesized changes in the rate of organic matter decomposition and nutrient release from exotic litter. This study investigated these questions and developed two main hypotheses: 1) M. quinquenervia will have the slowest rate of decomposition; and 2) M. quinquenervia litter will release less nitrogen and phosphorus than T. distichum and P. elliottii litter. The residence time of M. quinquenervia litter was, in fact, significantly longer than T. distichum litter. However, the residence time of the M. quinquenervia litter was significantly shorter compared to P. elliottii litter. In addition, M. quinquenervia litter did not alter nitrogen or phosphorus release rates compared to the native species. This indicates that M. quinquenervia, in its current suppressed state, should not significantly alter the basic ecosystem processes of organic matter decomposition and nutrient turnover in invaded P. elliottii-T. distichum ecotone forests. This finding indicates the need for ecosystem-specific studies to assess impacts and consequences of plant invasions. Treating remnant M. quinquenervia populations with chemical or mechanical methods may cause significant collateral damage to native plant communities and may negatively influence ecosystem function. At this point, it might be better to focus future weed management activities on more damaging weeds.

Technical Abstract: Melaleuca quinquenervia is one of the most problematic invasive species in Florida Everglades’ ecosystem. Treatment of these populations has been justified in part by hypothesized changes in the rate of organic matter decomposition and nutrient release from exotic litter. This study investigated these questions and developed two main hypotheses: 1) M. quinquenervia will have the slowest rate of decomposition; and 2) M. quinquenervia litter will release less nitrogen and phosphorus than T. distichum and P. elliottii litter. As hypothesized, the residence time of M. quinquenervia litter was significantly longer than T. distichum litter. However, the residence time of the M. quinquenervia litter was significantly shorter compared to P. elliottii litter. In addition, M. quinquenervia litter did not alter nitrogen or phosphorus release rates compared to the native species. Treating remnant M. quinquenervia populations with chemical or mechanical methods may cause significant collateral damage to native plant communities and may negatively influence ecosystem function. Additional research is needed to determine if benefits outweigh costs to plant communities from the treatment of this exotic, but now non-invasive plant.