Biomass estimation within an Australian eucalypt forest: Meso-scale spatial arrangement and the influence of sampling intensity

Plant biomass is important when measuring productivity, calculating carbon stores and when studying interactions between abiotic factors and biotic organisms. However, information on the spatial arrangement of above ground live biomass (AGLB) is lacking and while the influence of replication on estimated AGLB has been studied, it has rarely been the focus in Australian ecosystems. This study examined spatial arrangement of AGLB, the influence of survey design, and interactions between abiotic factors and AGLB. Above ground live biomass was measured in a remnant eucalypt forest at Karawatha Forest Park (∼900 ha), a long term ecological research site (LTER node) within the Terrestrial Ecosystem Research Network (TERN) South-east Queensland Peri-urban Supersite, Australia. Sampling of woody vegetation occurred in 32 one-hectare plots systematically placed at 500 m intervals. Above ground live biomass was estimated to be 146.51 Mg ha−1, with spatial interpolation calculating that there was 133,487 Mg of AGLB (> 1 cm DBH) within Karawatha Forest Park. Time and effort could be saved by not measuring trees <10 cm, because only ∼7% of the AGLB biomass (> 1 cm) would be lost. Despite relatively low variation in AGLB among plots, bootstrapping indicated that at least 15 PPBio (Program for Planned Biodiversity and Ecosystem Research) plots are needed to precisely estimate AGLB within Karawatha Forest Park. Topography and soil chemistry performed poorly at explaining AGLB, and it is likely that past and present human activities (e.g. logging and arson) play a role in influencing AGLB at Karawatha Forest Park. This study identifies the importance of independent replication to capture variation in AGLB for carbon storage estimation, and the power of systematic sampling within sites for mapping carbon stocks at meso and larger scales.