Rethinking assessment of biodiversity in northern New Zealand forests: Incorporating lichens, a neglected but important group, in vegetation monitoring

A project undertaken at the Unitec Institute of Technology and supervised by Dan Blanchon

Project Team:

Dan Blanchon, Andrew Marshall, Glenn Aguilar, Peter de Lange (Unitec Institute of Technology)
Craig Bishop (Auckland Council)
Linton Winder (Consultant)

Approximately 85% of the New Zealand lichen mycobiota has been described, however information about the distribution, population size and ecology of most of these species is lacking (1108 of 2026 taxa are listed as `data deficient' in New Zealand's 2018 threat listing). Biodiversity surveys of vegetation in New Zealand routinely ignore lichens, perhaps assuming that lichen diversity will be reflected in diversity data collected for vascular plants, i.e. biodiversity surrogacy. There is a lack of research into the effectiveness of biodiversity surrogates in New Zealand. Results are often unclear as they are usually dependent on the taxonomic groups in question and the type of forest sampled.  With the exception of one Australian study, most studies of biodiversity surrogates have taken place in the northern hemisphere. In Auckland the Council maintains 20 x 20m permanent plots from which it collects a range of data, however they do not currently assess lichens. Little is known of lichen assemblages in mainland forested areas and only limited, out of date information is available for Auckland's Waitakere Ranges. There is also a lack of literature on lichen assemblages in particular ecosystem types, such as kauri forest (threatened by kauri dieback), or on regenerating forest such as Kunzea/ Leptospermum `scrub', which is often considered to be of “low value” ecologically. This makes it difficult for biodiversity staff to consider lichens when making recommendations on applications to clear forest for development and for restoration initiatives.

This project utilized 50 existing 20 x 20m permanent plant monitoring plots across the Auckland Region (Figure 1) incorporating a variety of forest types in regional parks and urban forest remnants to provide baseline data on lichen diversity in different vegetation types and assess if lichen diversity is "implied" using current monitoring methods.  Six hundred individual trees from 48 different tree species were surveyed, with four vertical quadrats (relevés) per tree (2400 relevés), (Figure 2). Opportunistic sampling within the plots was done for a further 14 tree species (Figure 3) and from tree canopies, roots and the forest floor. Over 2700 voucher specimens have been collected, with around 60% already accessioned into Unitec’s herbarium.

Full identification has been completed for the first twenty plots, with 181 different species of lichens identified, and preliminary identification of the remaining plots currently being completed. Of these, one is listed as “Nationally Critical”, three are “Naturally Uncommon” and 59 are “Data Deficient” (Figure 4). Information from our study was used directly by the New Zealand National Threat Classification Panel (Lichens) in 2017 for the new threat assessment that was published in 2018.

Thirteen new species records for New Zealand were identified, the presence of one of which (Pertusaria endoxantha) has already been published (Figure 5). We are working on a series of papers recording the other species currently (for submission in 2019). Three species new to science have also been identified and the first of these will be named in a paper being written currently.
 
Data for our first twenty plots is currently being analysed in combination with Auckland Council data previously collected on all 20 x 20m permanent vegetation plots situated on Auckland Council reserve land (complete list of vascular plant species present in each plot, species richness and abundance, canopy cover, canopy height, slope, aspect, distance from coast). These plots all fell within the Waitakere Ranges Heritage Area, and a paper detailing our findings is currently being drafted for submission in early 2019. Initial analyses indicate that measures of vascular plant diversity are NOT an effective ecological surrogate for lichen diversity.
 
The next twenty plots visited were in urban forest fragments, and our intention is to analyse this dataset when the identification work is complete to allow a comparison between the data collected in continuous forest and urban bush fragments.
 
Field work on the final four sites has recently been completed for the third stage of the project, visiting continuous forested areas further afield of our original study area, so subsequent data can then be compared with our initial first stage dataset to see if any correlation that may or may not have been found holds true over a larger geographical area.
 
We will use our dataset to summarise our findings from plots in the now threatened Kauri (Agathis australis) forest ecosystem type in the region.  Kauri are under threat from a Phytophthora species, and our findings will contribute to the present pool of knowledge about this ecosystem type.

In addition, this project aims to produce lists for particular sites in the Auckland Region (identification of sites of ecological importance); produce lichen species lists for specific vegetation types (identification of important ecosystems, provision of reference ecosystem data, information for ecological restoration, vegetation covenant audits); produce suitability maps for rare lichen species may aid in the discovery of other populations.


 

 

 

Figure 1. Map of the Auckland region showing study sites.

Figure 2. Attaching the relevé to tree at a site.

Figure 3. Opportunistic collecting of crustose lichens from tanekaha (Phyllocladus trichomanoides) at a field site near Huia, Waitakere Ranges, Auckland

Figure 4. Pertusaria endoxantha on trunk of tanekaha (Phyllocladus trichomanoides).

Figure 5. Anzia entingiana (At Risk: Naturally Uncommon) on kauri (Agathis australis).