Paengaroa has a footbridge across the Hautapu River. PHOTO/SUPPLIED
PAENGAROA Reserve is a larger patch of native forest than Bushy Park and the two areas share only a few plants.
Paengaroa has no tawa, hinau, titoki, nikau, karaka, kamahi, supplejack or northern rata. Only one tree fern species is common and there are no native beeches.
So where is this strange forest? The answer is at Mataroa, some 7km north-west of Taihape - and it's the destination for a Whanganui Summer Programme (WSP) trip on Sunday, January 15.
So, if it's lacking so much, what does it have? In fact, the forest canopy is quite varied. Kowhai (two species), ribbonwood, narrow-leaved lacebark (houhi), black and white maire are common and, above all, there are some very large-diameter podocarps (native conifers), especially kahikatea and matai, specimens of which have been dated at 716 years old and 1358 years respectively. Totara, rimu, miro and pahautea are known here.
The differences between Paengaroa and Bushy Park are even more marked in the kinds of shrubs under the trees. Paengaroa is a little like Whanganui's Gordon Park Scenic Reserve in having a dense understorey of tangled, small-leaved (divaricating) shrubs on the river flats. The variety of shrubs at Paengaroa is much greater than at Bushy Park, and includes some of New Zealand's rarest and most threatened species.
Although at first sight they might look much the same, many of these divaricating shrubs are unrelated and include members of the daisy, coffee and violet families and others in the same families as citrus, myrtle, five-finger, teak, lemonwood, hinau, korokio and fig.
Paengaroa has at least 33 divaricating shrub species, almost certainly more than any comparable extent of forest in New Zealand.
It is thought divaricating shrubs evolved to withstand moa browsing, a theory supported by the fact that some become "normal" trees when they reach about 3m, the height that the tallest moa could browse. These include kowhai, matai, kaikomako, houhi and pokaka. The total number of different native ferns, conifers and flowering plants recorded at Paengaroa is 240 species, about 50 more than Bushy Park. Twelve species are on the NZ threatened plants list.
Some ideas as to why Paengaroa is such a diverse place for plants and why so many of its plants are threatened will be discussed on the WSP trip. Keen watchers and listeners may find tui, bellbird, kereru, grey warbler, fantail, tomtit and rifleman. On a visit last month we saw a NZ falcon. North Island robins were introduced to Paengaroa about the same time as at Bushy Park, and they thrived for a few years. One is reputed to remain. The reserve has lizards and some special invertebrate animals too, but they are not easy to see during the day.
Paengaroa has a footbridge across the Hautapu River at the start, a short length of boardwalk through the forest to an open area, then a somewhat rough, formed route that follows the river through forest until it emerges at the edge of the reserve. As some people found last year, visitors need to be quite sure-footed and moderately fit for the 2-3km walk. There is a short ascent and descent part-way along; keen people may be able to go to the top of the reserve, 150m above the river.
Paengaroa was declared a Mainland Island Reserve by the Department of Conservation in the early 1990s, one of just six in NZ. Participants in the WSP trip will see and hopefully get to know why this is one of New Zealand's most important forest reserves.