Clover species cover on summer dry hill country in Central Otago

Abstract

The prevalence of annual clover species and white clover (Trifolium repens) during the critical late winter to early summer period (mid Aug - Dec) are compared in relation to aspect, altitude, temperature and rainfall on Mt Grand at Hawea Flat. Measurements were at four north facing sites (450, 620, 750, 910 m a.s.l.) and one shady site at 630 m a.s.l. The rainfall was similar for all altitudes and aspects but annual clovers dominated on sunny faces and the perennial white clover dominated on the shady face with suckling (T. dubium) the only adventive annual clover present. Annual cluster clover (T. glomeratum) dominated on the lower sunny faces at 450 and 620 m and sub clover (T. subterraneum) dominated at 750 m. Suckling and striated clover (T. striatum) were present on all sunny aspect sites and were unaffected by altitude while haresfoot (T. arvense) presence increased with altitude. Air thermal time accumulation for the mid Aug-Dec period was 1440 °Cd at the 450 m site and declined at 100 °Cd per 100 m of elevation (r2 = 0.99). Thermal time at 910 m was <1000 °Cd and may limit seed production of some annual clover species at or above this altitude. The dominance of adventive annual clovers on the sunny aspects indicates areas that are probably suitable for introduction of improved annual species such as balansa clover (T. michelianum) or modern cultivars of sub. Productivity of perennial white clover which has persisted on the shady faces may be increased by more intensive grazing management. Keywords: altitude, aspect, hill pastures, rainfall, spring production, thermal time, Trifolium arvense, T. glomeratum, T. dubium, T. repens, T. striatum, T. subterraneum.