Variation in exotic and native seed arrival and recruitment of bird dispersed species in subtropical forest restoration and regrowth

Abstract

Invasive bird-dispersed plants often share the same suite of dispersers as co-occurring native species, resulting in a complex management issue. Integrated management strategies could incorporate manipulation of dispersal or establishment processes. To improve our understanding of these processes, we quantified seed rain, recruit and seed bank density, and species richness for bird-dispersed invasive and native species in three early successional subtropical habitats in eastern Australia: tree regrowth, shrub regrowth and native restoration plantings. We investigated the effects of environmental factors (leaf area index (LAI), distance to edge, herbaceous ground cover and distance to nearest neighbour) on seed rain, seed bank and recruit abundance. Propagule availability was not always a good predictor of recruitment. For instance, although native tree seed rain density was similar, and species richness was higher, in native plantings, compared with tree regrowth, recruit density and species richness were lower. Native plantings also received lower densities of invasive tree seed rain than did tree regrowth habitats, but supported a similar density of invasive tree recruits. Invasive shrub seed rain was recorded in highest densities in shrub regrowth sites, but recruit density was similar between habitats. We discuss the role of microsite characteristics in influencing postdispersal processes and recruit composition, and suggest ways of manipulating these processes as part of an integrated management strategy for birddispersed weeds in natural areas.

Artificial perches promote vegetation restoration

“…The use of artificial perches by birds facilitates the arrival of larger and more diverse seed rain, promoting the establishment of seedlings in degraded open areas. The fact that artificial perches increase the abundance of the seed rain in altered areas is crucial considering that a large proportion of seeds will not survive and the availability of propagule source does not always reflect larger seed rain (White et al 2009;Graham and Page 2012;Reid and Holl 2013;Zwiener et al 2014). Consequently, restoration programs that induced the entry of propagule result in higher plant densities than those based just in passive restoration (Toh et al 1999;Tres and Reis 2009;Schorn et al 2010).…”

Lost in the weeds: Ligustrum sinense reduces native plant growth and survival

“…With no native members in the genus, L. sinense is likely phylogenetically distinct among the 24 native species of the Oleaceae family in the continental United States (USDA 2009). Ligustrum sinense has severe effects on the floodplain forest community and these effects are likely to amplify in the future with increasing habitat fragmentation and increasing atmospheric CO 2 , both factors that promote L. sinense invasion (Bradley et al 2010;Cadenasso and Pickett 2001;Smith et al 2008;White et al 2009). …”

Impacts of invading alien plant species on water flows at stand and catchment scales

“…(1982 ), Nagler et al . (2009 ) Salix babylonica Tree >5 No <4 3.28 S: Glenn and Nagler (2005 ), native willow forest Solanum mauritianum Shrub <10 Probably No Moderate S: White et al . (2009 )—measured values not available Tamarix chinensis Tree <6 Probably No 0.9–3.5 (3.0); 1.2–4.2; 2.6–3.6; 2.58–4.05 (3.58) S: Nagler et al .…”