Gahnia Grove - Site summary and discussion's Journal

At last we understand the life cycle whose manifestations we have been witnessing since May 2018 throughout the manuka forest margin, and it confirms the suppression of native regeneration through dense soil occupation by corms, despite the failure of the weed to flower in this partial shade: http://www.herbiguide.com.au/Descriptions/hg_Bulbil_Watsonia.htm

On initially observing this forest margin, juvenile and seedling manuka, kunzea and native broadleaf or podocarps were rare in the 6 to 8m H dense manuka canopy, with an understorey only of dead manuka. We feared the forest succession from manuka to kanuka and then forest trees might not occur, and instead the pampas, gorse, Watsonia, Aristea and other weeds might take over this 150 x 10m of land, which had been dedicated to the extension of existing podocarp/rawirinui forest regeneration by the cessation of mowing several decades ago..

If the intended natural forest succession does take place, it may never be possible to determine what would have happened without control of the Watsonia and pampas, since the entire area has now been at least partially hand weeded for 1-2 years, and leptospermeae are germinating and developing in released areas, often seen directly alongside the annually winter-growing Watsonia leaves during their control.

But we may be able to learn the effect of the method and timing being used in the control of Watsonia, both in the filtered light of a broken manuka canopy, and in the partial shade of the outer manuka and rawirinui margin, in previously-mown grass where in 2018 it was flowering and reproducing through cormils.

The location has been generalised in our iNaturalist observation to avoid disturbance or theft, so it won't appear in the data for the restoration trial or the area generally, but it was thrilling to see a gecko in the outer manuka margin, a couple of metres away from where I was handweeding an area of dense Bulbil Watsonia, and only about 10m from the mown recreational grass much enjoyed by dogs and their owners.

Be safe, little gecko. Climb back down into your man-made hole and find a bottle or something too small for rats, to hide in at night. (Note to self: don't remove any more isolated bottles and cans from the forest).

UPDATE: DOC was advised, as requested on heir website, and an appreciative reply was received, with more information to follow. DOC collect data to build knowledge of the remaining population of these endemic reptiles. Currently they are considered At Risk of extinction, after being common in manuka scrub throughout Auckland until the housing boom of the 70s.

Fortunately Reserve visitors generally keep themselves and their dogs to the recreational mown grass area and the forest tracks. However, responsible dog owners ensure their pets have energetic and interesting exercise, and many if not most dogs are off-leash as their owners accompany them through the winding forest tracks.

Protection of the remaining endemic lizards in both the DOC-owned upper forest and estuarine areas, and the Council-owned forest in-between and surrounding them, would require definition of boundaries for recreational and conservation.

Due to the presence of both domestic and feral cats, which, as I observed 30 years ago in the case of my own beloved pet, can effectively eliminate lizards from the forest, areas of cat-proof vegetation are essential to maintain as habitat. Weeds such as dense Eleagnus, blackberry, honeysuckle, jasmine and ivy, and the extensive and widespread inorganic refuse, need to be replaced by equally effective protection for lizards, invertebrates and birds before the complete removal of refuse or weeds.

Ground litter and dead vegetation is especially important as part of their habitat. Welll-intentioned clearing and tidying of vegetation leaves reptiles, invertebrates and young birds without refuge from predators and human disturbance.

The information below is copied from https://rarespecies.nzfoa.org.nz/species/forest-gecko/

"Association with Plantations
Forest geckos have been found associated with exotic forestry in Northland, Auckland, Spooners Range, Nelson and on the West Coast.

Management Options and Methods

Maintain wide and interconnected zones of potential lizard habitat, e.g. indigenous forest and shrubland, rocky gullies, cliffs and other distinctive habitat types.
Create buffers around known habitat.
Consider permanent protection of known habitat.
Comply with best forest operational management practices to avoid damage to lizard habitat.
Fell and haul timber away from lizard habitat.
Exclude livestock from lizard habitat.
Control possums, deer and goats that could enter lizard habitat.
Raise awareness of staff and contractors of the presence of lizards and the need to protect them.
Monitoring Options
Take photographs or write a detailed description when lizards are found. This can be used for later identification.
Survey for lizards, particularly if first time planting is being considered for the area. Note that planned surveys require a permit under the Wildlife Act (contact DOC for survey methods and permits).
Maintain database of sightings of threatened lizards and liaise with DOC.
Report findings to DOC"

From https://www.scoop.co.nz/stories/SC2002/S00030/record-dry-spells-and-effects-on-forests-expert-reaction.htm:

"Associate Professor Cate Macinnis-Ng, School of Biological Sciences and Te Pūnaha Matatini, University of Auckland, comments:
“We often think about the devastating impacts drought can have on agriculture but forests and other ecosystems also suffer under drought. Around the world, there are growing records of forest dieback due to increasing frequencies and intensities of drought due to climate change. Here in Aotearoa, droughts don’t generally cause forest death because our droughts last months rather than years.

“While there are some examples of forest death due to drought in the literature, our ongoing research on kauri suggests their deep roots, stem water stores and conservative water use make this species well-prepared for dry periods.

“However, in the 2013 drought, we found that litter fall increased in kauri forest as kauri trees lost leaves to reduce leaf area and therefore save water. This type of response may complicate ongoing efforts to use remote sensing techniques to detect kauri dieback but continuing work at our experimental drought plot will help us tease apart canopy changes due to drought from canopy changes due to dieback.

“Interactions between kauri dieback impacts and drought are not clear. Dry conditions may prevent spread of the pathogen but when rain does arrive, trees weakened by drought may be vulnerable to infection.

“Established forests may be relatively safe from drought impacts, seedlings and restoration plantings are vulnerable as developing root systems of smaller plants do not have access to deep soil water stores. If drought continues for extended periods, carbon uptake may be reduced as plant productivity slows.

“Drier plant tissues are also more flammable so we all need to be especially careful with fire. The recent forest fires across Australia were exacerbated by drought and severe fire weather across large areas. While we are unlikely to suffer such catastrophic events here, we still need to plan carefully to protect forest and manage our water supply."