Effects of seed dispersal and microsite features on seedling establishment in New Zealand fleshy-fruited perennial mountain plants

Factors determining the effectiveness of animals as seed dispersers include effects of gut passage on seed viability and germination, the microsite into which seeds are deposited, and potential post-dispersal impacts on establishment through predation and herbivory. We determined the relative importance of key pre- and post- seed dispersal processes for eight fleshy fruited montane and subalpine woody species that occur naturally in montane-subalpine mixed shrub-grassland in New Zealand's Southern Alps. A full factorial field experiment measuring the effects of fruit pulp removal, beneath-canopy microsite (shade/open), vegetative competition (turf dug/not), and seed/seedling herbivore exclusion (caged/uncaged) on germination, seedling survival and height growth was carried out for 3.5years. Only three species began germination within one year of sowing while all species experienced at least some germination by 3.5years, showing the importance of long-term studies in the subalpine environment. The shade treatment gave the highest germination success, seedling survival and seedling heights for seven of the eight species. Fruit pulp removal, herbivore exclusion and reduced competition were all retained in some final top models, but less often than shade and with smaller effects on means. The seed disperser fauna of New Zealand's mountain flora has transformed from predominantly native birds to exotic mammals over the past century. Birds and mammals likely move seeds to different microsites. Since shady microsites were more important than fruit pulp removal, any changes in plant recruitment caused by changing disperser faunas are likely to come from different seed deposition sites.