Spatial variation in litter production by the mangrove Avicennia marina var. australasica in Rangaunu harbour, Northland, New Zealand

Abstract

Litter fall was measured at two intertidal levels within two stands of the mangrove Avicennia marina (Forsk.) Vierh. var. australasica (Walp.) Moldenke in Rangaunu Harbour, New Zealand (34° 57'S, 173° 15'E). The seasonal pattern of litter fall was typical of A. marina at high latitudes. Flowering occurred in March‐April and fruit fell 9 months later during December‐January. Leaf fall was highest from November to February and was positively correlated with temperature and negatively correlated with sediment water availability (total rainfall minus total evaporation). Total annual litter fall ranged from 1.81 ha^‐1 yr^‐1 to 6.21 ha^‐1 yH and was proportional to mean tree height at each site. Leaves constituted on average 73% of the total litter fall and were the only litter component to show significantly lower magnitude at both elevated sites. The largest litter collections were made during the summer months coincident with peak falls of leaves and fruit. The possible contribution of mangrove litter to es‐tuarine food chains in northern New Zealand estuaries is discussed.

Keywords:

• mangrove swamps
• productivity
• organic matter
• detritus
• Avicennia marina var. australasica
• New Zealand