@Article{TreuhaftLeGoKeSaNeAl:2017:TrStBi,
author = "Treuhaft, Robert and Lei, Yang and Gon{\c{c}}alves, Fabio and
Keller, Michael and Santos, Jo{\~a}o Roberto dos and Neumann,
Maxim and Almeida, Andr{\'e}",
affiliation = "Jet Propulsion Laboratory, California Institute of Technology and
Jet Propulsion Laboratory, California Institute of Technology and
{Canopy Remote Sensing Solutions} and Jet Propulsion Laboratory,
California Institute of Technology and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and Amazon and {Universidade Federal
de Sergipe (UFS)}",
title = "Tropical-forest structure and biomass dynamics from TanDEM-X radar
interferometry",
journal = "Forests",
year = "2017",
volume = "8",
number = "8",
pages = "Article number 277",
month = "July",
keywords = "tropical forest dynamics, aboveground biomass, interferometric
SAR, TanDEM-X.",
abstract = "Changes in tropical-forest structure and aboveground biomass (AGB)
contribute directly to atmospheric changes in CO2, which, in turn,
bear on global climate. This paper demonstrates the capability of
radar-interferometric phase-height time series at X-band
(wavelength = 3 cm) to monitor changes in vertical structure and
AGB, with sub-hectare and monthly spatial and temporal resolution,
respectively. The phase-height observation is described, with a
focus on how it is related to vegetation-density, radar-power
vertical profiles, and mean canopy heights, which are, in turn,
related to AGB. The study site covers 18 × 60 km in the
Tapaj{\'o}s National Forest in the Brazilian Amazon.
Phase-heights over Tapaj{\'o}s were measured by DLR's TanDEM-X
radar interferometer 32 times in a 3.2 year period from 2011-2014.
Fieldwork was done on 78 secondary and primary forest plots. In
the absence of disturbance, rates of change of phase-height for
the 78 plots were estimated by fitting the phase-heights to time
with a linear model. Phase-height time series for the disturbed
plots were fit to the logistic function to track jumps in
phase-height. The epochs of clearing for the disturbed plots were
identified with \≈1-month accuracy. The size of the
phase-height change due to disturbance was estimated with
\≈2-m accuracy. The monthly time resolution will facilitate
REDD+ monitoring. Phase-height rates of change were shown to
correlate with LiDAR RH90 height rates taken over a subset of the
TanDEM-X data's time span (2012-2013). The average rate of change
of phase-height across all 78 plots was 0.5 m-yr-1 with a standard
deviation of 0.6 m-yr-1. For 42 secondary forest plots, the
average rate of change of phase-height was 0.8 m-yr-1 with a
standard deviation of 0.6 m-yr-1. For 36 primary forest plots, the
average phase-height rate was 0.1 m-yr-1 with a standard deviation
of 0.5 m-yr-1. A method for converting phase-height rates to
AGB-rates of change was developed using previously measured
phase-heights and field-estimated AGB. For all 78 plots, the
average AGB-rate was 1.7 Mg-ha-1-yr-1 with a standard deviation of
4.0 Mg-ha-1-yr-1. The secondary-plot average AGB-rate was 2.1
Mg-ha-1-yr-1, with a standard deviation of 2.4 Mg-ha-1-yr-1. For
primary plots, the AGB average rate was 1.1 Mg-ha-1-yr-1 with a
standard deviation of 5.2 Mg-ha-1-yr-1. Given the standard
deviations and the number of plots in each category, rates in
secondary forests and all forests were significantly different
from zero; rates in primary forests were consistent with zero.
AGB-rates were compared to change models for Tapaj{\'o}s and to
LiDAR-based change measurements in other tropical forests.
Strategies for improving AGB dynamical monitoring with X-band
interferometry are discussed.",
doi = "10.3390/f8080277",
url = "http://dx.doi.org/10.3390/f8080277",
issn = "1999-4907",
language = "en",
targetfile = "forests-08-00277-v3.pdf",
urlaccessdate = "27 abr. 2024"
}