TUTCRIS - Tampereen teknillinen yliopisto


3D Measurements of Tropical Forest Structure for BIOMASS, Morphology and Calibration and Validation of Satellite Observations.

Tutkimustuotos: Konferenssiesitys, posteri tai abstrakti


TilaJulkaistu - toukokuuta 2016
TapahtumaLiving Planet Symposium 2016 - Prague, Tshekki
Kesto: 9 toukokuuta 201613 toukokuuta 2016


ConferenceLiving Planet Symposium 2016


Measurement of tree structure is important for various reasons: estimating above ground biomass (AGB) i.e. the standing stock of carbon (C) stored per unit area; assessing tree function, particularly light, water and nutrient transport; metabolic scaling; competition; characterisation of age, type and history; response to climate and change/disturbance. In addition, tree structure is an important determinant of the Earth Observation (EO) signal, and is thus the focus of many parameter retrieval, calibration and validation efforts. Accurate measurements of tree shape and size are extremely hard to make, particularly non-destructively and for trees of any size. As a result many properties, particularly AGB, are inferred from empirical allometric relationships between easily measurable parameters such as diameter-at-breast height (dbh), and/or tree height, and tree size [1]. Allometric relationships also underpin estimates of forest properties from current and future EO missions; the forthcoming ESA BIOMASS and NASA GEDI missions will both rely on height allometries to infer AGB. Tropical forest allometries are based on relatively few destructive harvest measurements (few 103 trees in total), heavily biased towards smaller trees, and often from only partial tree measurements. This results in allometries with poorly-quantified uncertainty, which increases with tree size [2]. As a result, AGB, and forest structure more generally, are highly uncertain across the tropics. This results in large uncertainties in estimates of tropical forest C stocks and fluxes, as well as major differences between estimates made using slightly different allometries and other assumptions [3].

Here, we show how terrestrial laser scanning (TLS) methods have developed to the point where they can be routinely deployed to measure tree structure of tropical forest trees accurately and non-destructively [4]; this is not currently possible any other way. We present results from TLS field campaigns across the tropics, including Africa, S. America and Australia. We use the TLS measurements to derive estimates of tree volume and, combined with wood density estimates, AGB. We show that these estimates agree to within a few % of destructively measured values [5]. We also show that TLS measurements can capture the size and structure of all trees within measured plots, resulting in size estimates that are significantly different from existing allometries. We discuss the potential for (and implications of) including TLS-derived measurements into tropical forest allometries, for improving estimates of C stocks, particularly for large trees, and particularly from forthcoming EO missions that will depend on tropical forest allometry.