Estimating productivity and apparent photosynthesis from differences in consecutive measurements of total living plant parts of an Australian heathland

Abstract

Estimates of productivity and apparent photosynthesis in a typical Australian heathland were obtained by harvesting monthly over a period of 2 years. Net productivity was small (400 g m^-2 year^-1 or less) while the rate of apparent photosynthesis was considerable (about 6000 g m^-2 year^-1), representing a photosynthetic efficiency around 5 %.

Below-ground production exceeded production above ground 6-10 times. Root biomass was of the order of 6500 g m^-2. Death and consumption of roots was large, and most of the products of community photosynthesis were diverted below ground to replace an annual root loss of some 5500 g m^-2.

Community growth was a reflection of the behaviour of the dominant, Leptospermum myrsinoides. Standing biomass above ground was sensitive to the activity of this species, which produces new shoots from spring to autumn in relation to available soil water. The annual occurrence of extensive leaf abscission and high mortality of roots is correlated with high temperatures, low humidity, and depleted soil moisture.