Sparse alpine vegetation near Tama Saddle. Photo NC.

The sparse and stunted state of the vegetation here is the result of the harsh condition caused by altitude (approx. 1400 m/4593'), but also of the strong westerly winds that often blow through Tama Saddle between the big volcanoes.
Like the rest of New Zealand, Tongariro National Park is subject to a weather pattern in which westerly winds are dominant and which brings successions of depressions and anticyclones. Because they lie high across the path of the weather, the volcanoes have very few windless days per year, and their western sides receive high rainfall (2800 mm/110 in. at 900m (2952') near Whakapapa Village, more so higher up).