In New Zealand concern has been expressed at potential detrimental effects of burning and livestock grazing to snow tussock Chionochloa spp. grasslands, especially at higher altitudes. This paper reports responses to burning (for up to six seasons post-burn), clipping (to simulate grazing), tussock ash addition, and leaf litter removal experiments on subsequent growth and flowering of narrow-leaved snow tussock C.rigida undertaken in alpine zone sites (870-1,200m) on Old Man Range, Maungatua and Coronet Peak (South Island).
On Old Man Range, tussocks were burned in spring fires in 1959 and 1961. Areas nearby were left (unburned since at least 1945). Fifty tussocks were marked in burned and unburned areas to follow flowering, and on 10 leaf elongation and leaf production and tillering. In spring 1964, small areas (each containing about 50 tussocks burnt during 1959 or 1961) were reburnt and fenced to exclude livestock.
At Coronet Peak effects on flowering of burning, cutting, or litter removal during spring or autumn 1960-61 were assessed (10 tussocks monitored/ treatment).
At all three sites, tillering and flowering response to burning, cutting (leaves cut at sheath, equivalent to severe grazing), cutting + tussock ash addition, and ash alone, during autumn (April) and spring (September) 1962 (20 tussocks/treatment and untreated controls) were assessed. At Coronet Peak, tussocks (unburnt for at least 20 years) had a thick accumulated litter layer; the effect of litter removal was investigated. Leaf elongation was measured only at Maungatua and Coronet.
At Old Man Range in 1964, the area burn in 1961 had much lower plant cover and more dead material and bare soil compared to unburnt areas. Vegetation in the 1959 burn area had still not recovered to pre-burn levels.
After spring burning, there was a significant increase in leaf elongation (135% of that of unburnt) during the first season post-burn, followed by a smaller increase (112-126%) in the second. However, during the subsequent four seasons, growth was less than unburnt tussocks (third 84-81% to the fifth season 65%). Reburning after five years significantly accelerated growth in the first season (compared to burnt once or unburnt tussocks); growth stimulation was considerably less in areas reburned after three years.
At Coronet and Maungatua, the most apparent treatment effect was increased leaf growth during the first season after fire. Spring burning resulted in significantly more growth than autumn burning. In the second season growth rate reduced among treated tussocks, and at Maungatua autumn-burnt tussocks grew at a rate less than that of the unburnt tussocks (but not significantly so). Spring cutting alone and with ash increased growth, but only significantly so at Coronet. Addition of ash alone had no effect. Litter removal in spring increased tillering slightly.
Overall, burning (and to a lesser extent clipping) initially increased leaf elongation and tillering rates, and promoted flowering. Tussocks burned/clipped in autumn mostly exhibited a great loss of tillers. Growth responses to fire were countered by grazing.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.royalsociety.org.nz/Site/publish/Journals/nzjb/1965/27.aspx