Influence of woody invader control methods and seed availability on native and invasive species establishment in a Hawaiian forest

Abstract

When invasive woody plants become dominant, they present an extreme challenge for restoration of native plant communities. Invasive Morella faya (fire tree) forms extensive, nearly monospecific stands in wet and mesic forests on the Island of Hawai'i. We used logging, girdling, and selective girdling over time (incremental girdling) to kill stands of M. faya at different rates, with the objective of identifying a method that best promotes native forest re-establishment. We hypothesized that rapid canopy opening by logging would lead to establishment of fast-growing, non-native invaders, but that slower death of M. faya by girdling or incremental girdling would increase the establishment by native plants adapted to partial shade conditions. After applying the M. faya treatments, seed banks, seed rain, and plant recruitment were monitored over 3 years. Different plant communities developed in response to the treatments. Increased light and nitrogen availability in the logged treatment were associated with invasion by non-native species. Native species, including the dominant native forest tree, (Metrosideros polymorpha) and tree fern (Cibotium glaucum), established most frequently in the girdle and incremental girdle treatments, but shortlived non-native species were more abundant than native species. A diverse native forest is unlikely to develop following any of the treatments due to seed limitation for many native species, but girdling and incremental girdling promoted natural establishment of major components of native Hawaiian forest. Girdling may be an effective general strategy for reestablishing native vegetation in areas dominated by woody plant invaders.

Recovery of native forest after removal of an invasive tree, Falcataria moluccana, in American Samoa

“…Thus, it appears from results that once management activities redirect the successional trajectory by killing the mature F. moluccana individuals in the overstory, the native-dominated forest community is capable of regaining dominance. This dynamic stands in stark contrast to results from experimental removal of the non-native, N 2 -fixing tree, Morella faya from forests of Hawaii Volcanoes National Park, where successful reestablishment and recovery of native forest species following girdling of the nonnative, N 2 -fixing tree is much less certain given the presence of highly competitive non-native species (Loh and Daehler 2008). It should be noted, however, that Clidemia hirta, an acknowledged invasive understory weed in Hawaii and elsewhere (Peters 2001;DeWalt et al 2004;Baret et al 2006), was present at relatively high densities (248 individuals ha -1 ) in some of our F. moluccana-removal plots (''Appendix 2'').…”

The assessment of invasive alien plant species removal programs using remote sensing and GIS in two selected reserves in the eThekwini Municipality, KwaZulu-Natal

“…Furthermore, those pixels that were detected as A. podalyriifolia in the 2015 imagery appear to be errors of commission (false positives) (Calviño-Cancela et al, 2014). Even though the clearing of this woody IAPs has been successful in this reserve, their removal could facilitate the recruitment of other IAPs (Loh & Daehler, 2008).…”

“…These species affect human health, agriculture, forestry and biodiversity (Richardson & van Wilgen, 2004). They impact on ecosystems by displacing indigenous vegetation and change ecosystem functions (Loh & Daehler, 2008). This leads to a reduction in the genetic variation of an environment due to localised extinction of endemic species.…”

Effects of Morella faya tree invasion on aboveground carbon storage in Hawaii

“…Once established, it grows in shaded or sunlit conditions (Loh and Daehler 2008), reaching the canopy and rapidly increasing in size. In contrast, native Metrosideros trees grow very slowly on these N-poor substrates (Vitousek et al 1987 Fig.…”