Experimental translocations of the threatened New Zealand plants carex inopinata cook (Cyperaceae) and simplicia Laxa Kirk (Poaceae)

Abstract

Carex inopinata Cook (Cyperaceae) and Simplicia laxa Kirk (Poaceae) are two threatened ‘grassy’ plants that generally occur in dry grassland and rock outcrop habitats. However, the restriction of these species to such areas may indicate relict habitats. We tested this idea by translocating both species to Ōrokonui Ecosanctuary, near Dunedin. Carex inopinata was translocated to two sites (moderately-and highly-shaded) in 2010 and Simplicia laxa was translocated in 2011, but only to one site due to insufficient propagated material. At each site, plants were established in different microhabitats underneath a kānuka (Kunzea robusta) canopy, where ground cover was sparse and hence provided minimal competition for the translocated plants. We measured plant growth, flowering, and survival twice-yearly from 2010 to 2013, and again from 2015 to 2017. Also, we described the vegetation and recorded microclimate data at each site. Carex inopinata growth, flowering, and survival were highest under moderate shade, either in open (bare-ground) or beside-rock microhabitats. Highest growth levels alternated between these two microhabitats, particularly during a drought when plants in the open suffered some mortality or damage, while plants near rocks remained sheltered. Narrower ranges of relative humidity and temperature in rock versus open microhabitats attest to probable protection from drought. Despite 42% of originally planted C. inopinata individuals surviving, there was no seedling recruitment, therefore, the long-term persistence of this translocated population remains uncertain. Simplicia laxa did not successfully establish, although growth was also highest in open microhabitat. We cannot confirm whether habitat for S. laxa at Ōrokonui is absent but drought-related mortality influenced its failure to establish. Further monitoring of the C. inopinata plants will confirm whether this threatened sedge can persist under the conditions present at the translocation site.