Seed characteristics and regeneration of some species in invaded coastal communities

Abstract

The seed production, germination and regeneration characteristics of two native species (Acacia Iongifolia var. sophorae and Banksia integrifolia) and two invasive subspecies (Chrysanthemoides monilifera ssp. monilifera and ssp. rotundata) were compared.C. monilifera ssp. rotundata was similar in seed characteristics and regeneration to B. integrifolia in that: (1) seed production was over an extended period each year; (2) seed longevity was low (0-2% viable after burial for 3 years), but increased with depth of burial; and (3) re generation from 26 to 28% of mature plants occurred after fire.By contrast, C. monilifera ssp. monilifera was similar to A. Iongifolia var. sophorae in that; (1) seed production was over a short period each year;(2) ofthe total buried, 6-13% of seeds were viable after 3 years, and again numbers increased with depth of burial (percentages of missing seeds of K. longifolia were high but all remaining seeds were viable after 3 years); and (3) regeneration after fire occurred only from seed, hence their seed longevity is an important factor for long-term survival.However, growth habit and niche occupation by ssp. rotundata is similar to that of A. longifolia and the above differences may contribute to the observed displacement of the native by the invasive species. The distribution ofthe two invasive subspecies is at present largely in separate areas in Australia and it is predicted this situation will continue because of their differing climatic preferences, morphology and regeneration from fire.

Soil seed banks of secondary vegetation on the Port Hills and Banks Peninsula, Canterbury, New Zealand, and their role in succession

“…If these dispersed seeds in the upper layers were transient, then there must be both continual addition andloss (Keeley 1977),includingpredation (Kjellson 1985;Wellington & Noble 1985), germination followed by unsuccessful establishment, and loss of viability with time (Schafer & Chilcote 1970;Weiss 1984). At some study sites unsuccessful establishment following germination has been observed in bracken stands adjacent to forest, where seedlings of forest species have been seen to survive during winter, but die the following summer.…”

Heat increases germination of water-permeable seeds of obligate-seeding Darwinia species (Myrtaceae)

“…Acacia spp. Weiss 1984;Auld 1986;Keith et al 2002). Alternatively, some limited on-going establishment could be possible if seedlings were able to tolerate the existing cover of shrubs, herbs and grasses, or if they emerged into gaps caused by mortality of adult trees or shrubs as suggested for several Leucopogon species in the region (Ooi et al 2006b).…”

Novel technique shows different hydrophobic chemical signatures of exotic and indigenous plant soils with similar effects of extracts on indigenous species seedling growth

“…This is logical considering the persistent growth, reproduction and hence metabolism of C. monilifera spp. rotundata throughout the year (Weiss 1984). However the A. longifolia var.…”

“…All of the test species involved in the present study are likely to experience increased germination rates from winter to spring in accordance with the increasing temperatures and rainfall. This is particularly the case for B. integrifolia which seeds during winter and spring and has low seed bank viability (Weiss 1984). I. nodosa typically seeds in summer, although may seed throughout the year and is expected to have low soil seed bank longevity (Ens personal observation).…”

“…sophorae individuals in C. monilifera spp. rotundata invaded sites has been shown to be significantly lower than non-invaded sites (Mason and French 2008), the long lived seed bank (Weiss 1984) and warmer germination requirements suggest that increased interference by C. monilifera spp. rotundata against the establishment of A. longifolia var.…”