Sunday, September 28, 2008

Beech forest damage, Days Bay

Our ecosystems develop in association with the their surroundings (by definition). If one part of the system is disrupted then there may be further disruption in the rest of the system. If a large old tree falls down within a forest there can be many consequences.

Additional light may be let in. Wind can get in. The eventually decaying trunk will provide organic material for soil rejuvenation and so on. When several trees fall with very wet feet, inadequate root systems etc the consequences may be greater. When even more trees are felled by the addition of very strong wind the ecological issues escalate.

There is no doubt that the removal of the pines above Sunshine Bay contributed to the die-back and wind assisted toppling of many Beech trees over the southerly ridge from the Pine Forest and in to Days Bay. To imply that the death of the Beech trees was an almost direct result of the trees being cut from 2006 is simply not good ecological reasoning.

With the Pine Forest over the ridge (shown above) gone, other trees that had grown in it's shelter were now more exposed to the elements. Immediately after the first 'wet feet' and 'wind-blow' fall of pine trees in 2004, trees all around took a beating. First, of course, it was the neighbouring pine trees to those that had fallen - to natures hand, not man's.

The same storms had afflicted the Wellington City pine forest on the Tinakori hills (also 2004) and forced the WCC to lead the way in removing the remainder of their pine forest.

HCC council began cutting in 2005 and as already noted earlier a small stand of Beech on the edge of the northern Days Bay ridge were the first taller trees to die back. Other beech trees that had not grown in the lee of the forest, remained strong and unaffected. Medium height native specimens that had also begun to grow on that northern ridge in the lee of the pine forest also were burnt off.

In the photo above and the one below, of the northern ridge of Days Bay, it is clear that Beech trees can and have, survived strong salt laden winds. These photos were taken September 2008.

The photo below is also interesting in showing the very localised nature of the Beech tree wind-burn when viewed against the surrounding forest cover.

The area of the fallen Beech trees, only 2 years later, is covered with hundreds of Beech seedling many well over a metre high. If the trees were going to suffer die-back from wind burn maybe the good thing that happened was that they were not merely burnt but toppled.

It looks a mess now from afar but close up it a an amazing seedling bed. The uprooted trees effectively loosened soil, provided protection from the sun and moisture retention in the area immediately behind the root balls. There is probably going to be much faster return to a stronger forest than existed before, than if regrowth was happening following a fire.

Beech seedlings growing very strongly (despite a very dry summer) two years after their parents toppled. Look forward to a stronger, more healthy Beech forest.

My next post will consider a little of what we know of this area going back about 150 years. The Bays were cleared, burnt (on purpose and by accident) and farmed. Roads were cut into the hillside, sections were cleared and houses built.

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