Data from: Mangrove above-ground biomass and production are related to forest age at Low Isles, Great Barrier Reef

Above-ground biomass contributes a large proportion of mangrove carbon
stock; however, spatio-temporal dynamics of biomass are poorly understood
in carbonate settings of the Southern Hemisphere. This influences capacity
to accurately project the effects of accelerating sea-level rise on this
important carbon store. Here, above-ground biomass and productivity
dynamics were quantified across mangrove age zones dominated by Rhizophora
stylosa, spanning a tidal gradient atop a reef platform at Low Isles,
Great Barrier Reef, Australia. Above-ground biomass was extrapolated
across the forest using field plot data, allometry, a canopy height model
derived from remotely piloted aircraft (RPA) LiDAR and regression
analyses. Above-ground biomass production was calculated as mean annual
biomass increments and canopy production was determined using RPA-derived
multispectral imagery and a Normalised Difference Vegetation Index.
Mangrove above-ground biomass was estimated at 519.7 ± 3.11 t
ha-1 and increased with age up to the oldest forest (812.0 ± 12.9
t ha-1), believed to be ~135 ± 40 years old. Above-ground biomass was
explained by age and tidal position (r2 >0.8), with a positive
association between the two predictor variables. Above-ground biomass
production peaked at lowest intertidal positions in the youngest forest
aged <11 years at 36.3 t ha-1 yr-1, steadying thereafter, with a
mean of 12.5 ± 5.4 t h-1yr-1 across the island. Production in the canopy
remained high until the oldest forest and was negatively associated with
age and tidal position (r2 >0.9). Declining production in the older
zones corresponded to forest ageing, tidal positions becoming suboptimal
for growth and increased exposure to prevailing winds and cyclones. By
developing relationships between above-ground biomass accumulation and age
and tidal position, this study informs parameterisation of models of the
response of biomass to sea-level rise but requires additional information
about relationships between substrate evolution and forest development and
age.