Natural-enemies affect the seed and litter fall dynamics of Melaleuca quinquenervia in the wetlands, and influence long-term species diversity in leaf-litter

Authors: Rayamajhi, Min; Pratt, Paul; Tipping, Philip; Center, Ted; Leidi, Jorge; RODGERS, LEROY - South Florida Water Management District

Submitted to: Wetlands Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2018
Publication Date: 11/30/2018
Citation: Rayamajhi, M.B., Pratt, P.D., Tipping, P.W., Center, T.D., Leidi, J.G., Rodgers, L. 2018. Natural-enemies affect the seed and litter fall dynamics of Melaleuca quinquenervia in the wetlands, and influence long-term species diversity in leaf-litter. Wetlands Ecology and Management. 27(1):125-139. https://doi.org/10.1007/s11273-018-9645-4.
DOI: https://doi.org/10.1007/s11273-018-9645-4

Interpretive Summary: Natural enemies of the exotic tree Melaleuca quinquenervia (melaleuca) have established in Florida, USA. The litter and seed fall dynamic was predicted to be reduced and more variable in response to the natural enemy attacks. We assessed this by monitoring melaleuca stands over 16-yr at sites where natural enemies were established. Following natural enemy establishment: 1) leaf and seed fall increased during the first half of the study period and then both quantitatively declined by 70% or more, remaining at that range throughout the rest of the study period; 2) leaf and seed fall were positively correlated but the proportion of natural-enemy damaged melaleuca leaf litter was negatively correlated with the quantity of fallen seeds; 3) the overall amount and species composition of fallen non-melaleuca leaf litter gradually increased with the decrease in the amount of fallen melaleuca leaf litter. Over time, 18 non-melaleuca species were recovered in the litter fall, of these only two perennial species were recorded at early stages of the study but increased to seven during the second-half of the study and one was non-native. Only two natives, Cladium jamaicense among monocots and Myrsine sp. among dicots, produced significantly more litter in later stages of the study period. During 1997-2013 melaleuca leaf litter decreased from 96.2 to 81.7% and the total non-melaleuca litter increased from 3.8 to 18.3%. Natural enemies were present during entire study period and the proportion of damaged leaves in the litter increased over time. These results provide additional evidence to a growing body of literature that quantifies the role of natural enemies on leaf and seed fall in melaleuca’s exotic range.

Technical Abstract: Intentional and adventive natural enemies of exotic tree Melaleuca quinquenervia (melaleuca) have established in Florida. They are expected to damage melaleuca tree and result in an unsynchronized litter and seed fall and induce changes in litter composition. To assess these we conducted a 16-yr study using natural enemy established melaleuca sites in occasionally inundated habitat. We determined that following natural establishment: 1) leaf and seed fall increased during the first half of the study period and then both quantitatively declined by 75% or more and remained at that range throughout the study period, 2) leaf and seed fall were positively correlated, i.e., they increased or decreased together, but the proportion of natural-enemy damaged melaleuca leaf litter had negative correlation with the quantity of fallen seeds, 3) overall amount and species composition of fallen non-melaleuca leaf litter gradually increased with the decrease in the amount of fallen melaleuca leaf litter. Of the 18 non-melaleuca species identified to constitute non-melaleuca leaf litter fraction during different years during the study period only two perennial species accounted for the non-melaleuca fraction at the onset of the research and that number grew to seven during the second-half of the study period, of which one was non-native. Only two natives: Cladium jamaicense among monocots and Myrsine sp. among dicots produced significantly litter towards the second half of the study period. Of the total quantity of leaf litter in the research sites, melaleuca constituted 96.2% in 1997 compared to 81.7% in 2013, and during the same period total non-melaleuca litter increased from 3.8 to 18.3%. Signs and symptoms of the natural enemies of melaleuca existed throughout the study period. These results provided a compelling evidence of natural enemy-mediated unsynchronized leaf and seed fall which is diminishing melaleuca’s invasive attributes and providing competitive edge to the native plants.