DIFFERENTIAL EFFECTS OF PRECIPITATION AND TEMPERATURE ON SEED PHENOLOGY AND SEED PRODUCTION IN AGATHIS MACROPHYLLA IN FIJI

Abstract

Agathis macrophylla (Araucariaceae) is a native tree in Fiji, found in Vanuatu and Solomon Islands, that is of great socio-economic value, ecological significance and cultural importance. Due to the impact of climate change on biodiversity, this bio-geographical study was initiated to analyse a 30-year (1989–2019) data set from the Monasasvu Meteorological station, using descriptive statistics coupled with Mann-Kendall and Sen’s Slope test methods. The study detected the trend and impact of precipitation and rainfall on the fruiting phenology, mean fruit weight, total number of seed produced, volume seed count and germinants propagated for A. macrophylla from the Nausori Highlands, Ba Province, Western Division of Fiji for the period 2010–2019. The results showed significant deviation in the flowering and fruiting seasons and emergence of fruit cones which were observed between April to May, a five-month delay from the seed phenology calendar. There has also been a significant shift in fruiting and maturity richness and intensity as it occurred in the months when both the precipitation (456–652 mm) and temperature (26.8–28.6 °C) were higher. The phenological response to these climate variables was astounding as the coefficient of variation for the average fruit weight, seed numbers and germination rate ranged between 65–73%. This calls for more concerted conservation action in the identification and mapping of mature seed trees, a moratorium on timber harvesting during its fruiting and maturity seasons, establishing at least two seed stands, and germinating larger numbers of seedlings following mast seed years and holding them in the nursery under specific conditions until required for field planting.