On Wednesday, we finally got to work. CG came with us to see just how an exclosure plot is measured. The wind was pretty strong, but once under the canopy you didn't really notice that. The Alphabet exclosure is in a small pocket of forest at the base of the Ruahine range. All around and above it the canopy has collapsed. The total Forest Park area of the Ruahine is 93 260 ha and a good third of that is stuffed.

From near Waipukurau looking towards Ruahine Mountains, painted in 1880.

The exlcosure plot was first build in 1970 to monitor the effects of deer browsing, near the site of what used to be the Alphabet hut, hence Alphabet exclosure. Nothing much has happened to it since. It was visited 1982-1983 and photographed 1983 to show the vegetation growth inside.

The Pohangina field staff inspected the exclosure in 1996, when it was found to be in overall condition good, except for one corner held up by a rotting tree trunk. Back in the 1960's and 70's most plots were set up using trees as corner posts, as this saved on costs and energy, lugging 8 foot corner posts around in the bush is no picnic. Anyway, KM made a beautiful job of removing the dead tree, and restraining the wire netting. He even build a handy little stepladder (near the tree stump) to climb over the fence more easily.

The dotted lines are the outside of the exclosure, made of 6 foot high wire netting to keep deer out. The exclosure in not quite 20 m square (or even 20 m crooked) which is a bit of a shame because we wanted 16 quarter of 5 by 5 m, which didn't quite fit. I can identify why they chose this particular bit inside this forest remnant. It has one of the few remaining large Northern Ratas in it.

At first glance there did not seem to be much difference between the vegetation inside the exclosure and outside. The groundcover outside the exclosure appeared just as luxurious as inside.

Anyway, first job of the day was to squeeze as many 5 by 5 plots into the exclosure as possible. We did this by pulling orange bailing twine (for tying up bales of hay etc.) from one side to other (in the pattern shown above by the red lines). Inside each of these quarters we identified, measured and tagged each tree over 1.35 m tall and with a diameter at breast height (which happens to be 1.35 m too) larger than 3 centimeters.

The tagging is done by affixing small numbered aluminium tags to the tree with a nail. We used tags from D1000 to D0897, so we nailed 104 trees. Fifty-nine tags were used in the exclosure and 45 in the adjacent control plot that we laid out the next day. However, in the control plot, which is unfenced, the majority of trees (25) had multiple stems, and each stem counts as a tree (provided it is larger than the dimensions given above). The large number of multiple stemmed tawa, Beilschmiedia tawa, could reflect the damage done by animals, such as deer, while browsing. Most of the understory species are naturally multi-stemmed.

If you want to know what the species names in the above graph mean then have a look on this page. What us lazy scientists do, so that we don't have to write out the often very long Latin names all the time, is to use the first three letters of the first name (in CAPITALS) and the first three letters of the second name (in lower case).

The other thing to notice is that there are fewer species of tree outside the exclosure than inside. Not only that, but there are very few species that eventually make up the canopy, only tawa was found outside the exclosure. Total number of species (including ferns, lianes, seedlings and saplings) was 68 outside and 77 inside the exclosure.

Once we got our eye in, we could actually see an obvious visual difference between the exclosure and surrounding forest too. In the surrounding forest, there are very few seedlings and saplings in the deer browse tier, despite current low deer numbers.

The graph above shows this difference most clearly. There are very few plants (only 4 in this case) that make it past the 1.35 m tall mark. As it happens 2 of the 4 are actually important canopy species that weren't found at sapling stage inside the exclosure. These species (rewarewa - Knightia excelsa and miro, Prumnopitys ferrugineus) are found as seedlings inside the exclosure, and their absence from the sapling tier might be due to other factors, such as lack of light due to crowding by seedlings. As a general rule however, if a plant is between 30 cm and 2 m tall the deer will eat it.

I've put the seedling, fern and liane graphs on another page for the people that are really keen on science.

Deer numbers in this area are low at the moment. Possum numbers are probably moderate, the neighbours are putting poison out but we did see fresh canopy damage. Just goes to show that you don't need high numbers of deer or possum to get a change in the forest structure. What worries me is that we only found kamahi, Weinmannia racemosa, an important canopy species, as seedlings, and there were no obvious mature trees in the area. I have a suspicion that we might be looking at a slower version of canopy collapse here.

The numbers on the orange lines in the exlosure plot diagram refer to the seedling subplots we also measured. From each point we noted down the species and height classes of all plants within a 49 cm radius of the centre point. I haven't used this data on these pages.

Oh, you are probably wondering about the hailstone reference at the top of the page. Well, the second day, when KM helped us measure the control plot, we had several hailstorms. We were all wearing heavy woolen garb and rain gear in any case because it was bitterly cold that day (it can snow any time in those mountains, summer not withstanding), so a pelting of hail didn't really worry us. Actually, I prefer hail, it is dry rain and doesn't wet the writing surface of our waterproof paper to the same extend. Funny waterproof paper actually, couldn't write on it very well using pencil, had to use pen, and you know what ballpoint pens are like when they get wet - don't write. Must find a new or better supplier of the paper. Catch ya next time.