La altura de los bosques en un nuevo mapa de la NASA/The heights of forests in a new NASA map

Un equipo investigador liderado por la NASA ha creado un mapa exacto en alta resolución de la altura de los bosques de la Tierra. El mapa ayudará a los científicos a comprender mejor el papel que juegan los bosques en el cambio climático y como su altura influye sobre los hábitats de vida salvaje que contienen, y les ayudará a cuantificas el carbono alamcenado en la vegetación de la Tierra.
Los científicos del Jet Propulsion Laboratory de la NASA, Pasadena, California; la Universidad de Maryland, College Park; y el Woods Hole Research Center, Falmouth, Massachusets, crearon el mapa utilizando 2,5 impulsos de laser desde el espacio,cuidadosamente apantallados y distribuidos globalmente . Los datos de detección y alcance de la luz (lidar) fueron recopilados en 2005 utilizando instrumentos a bordo del satélite Ice, Cloud and land Elevation Satellite (ICESat) de la NASA.
Según el investigador Marc Simard del JPL "Conocer la altura de los bosques de la Tierra es crítico para estimar su biomasa o la cantidad de carbono que contiene” . El mapa muestra los puntos más elevados de la cobertura boscosa. Su resolución espacial es de 1 km (0,6 millas). El mapa se validó frente con datos procedentes de una red de cerca de 70 puntos situados en la superficie del planeta.
Los investigadores han encontrado que, en general, las alturas de los bosques decrecen a elevaciones altas y que son más altas a latitudes bajas, disminuyendo según su lejanía a los trópicos. Una notable excepción se encontró acerca de los 40 grados sur, en los bosques tropicales de Australia y Nueva Zelanda, donde hay eucaliptos, uno de los árboles más altos, y que sobrepasan con creces los 40 metros (130 piés)
En general, las estimaciones en el Nuevo mapa muestran los árboles más altos que en un mapa previo del ICESat, sobre todo en los trópicos y en los bosques boreales, y fueron más bajos en as regiones montañosas. La exactitud del nuevo mapa varía con los tipos de comunidades ecológicas de los bosques, y depende también de cuanto han sido perturbados por actividades humanas y de la variabilidad de la altura natural de los bosques.
Los resultados fueron publicados reciente en el Journal of Geophysical Research -- Biogeosciences.

A NASA-led science team has created an accurate, high-resolution map of the height of Earth's forests. The map will help scientists better understand the role forests play in climate change and how their heights influence wildlife habitats within them, while also helping them quantify the carbon stored in Earth's vegetation.
Scientists from NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the University of Maryland, College Park; and Woods Hole Research Center, Falmouth, Mass., created the map using 2.5 million carefully screened, globally distributed laser pulse measurements from space. The light detection and ranging (lidar) data were collected in 2005 by instruments onboard of the NASA's Ice, Cloud and land Elevation Satellite (ICESat).
"Knowing the height of Earth's forests is critical to estimating their biomass, or the amount of carbon they contain," said lead researcher Marc Simard of JPL. The map depicts the highest points in the forest canopy. Its spatial resolution is 0.6 miles (1 kilometer). The map was validated against data from a network of nearly 70 ground sites around the world.
The researchers found that, in general, forest heights decrease at higher elevations and are highest at low latitudes, decreasing in height the farther they are from the tropics. A major exception was found at around 40 degrees south latitude in southern tropical forests in Australia and New Zealand, where stands of eucalyptus, one of the world's tallest flowering plants, tower much higher than 130 feet (40 meters).
In general, estimates in the new map show forest heights were taller than in a previous ICESat-based map, particularly in the tropics and in boreal forests, and were shorter in mountainous regions. The accuracy of the new map varies across major ecological community types in the forests, and also depends on how much the forests have been disturbed by human activities and by variability in the forests' natural height.
Results of the study were published recently in the Journal of Geophysical Research-Biogeosciences.

Tomado de/Taken from Science News
Mapa disponible en/Map available at 3D Land Mapping

Resumen de la publicación/Abstract of the paper

Mapping forest canopy height globally with spaceborne lidar

Marc Simard, Naiara Pinto, Joshua B. Fisher, Alessandro Baccini
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, G04021, 12 PP., 2011
doi:10.1029/2011JG001708
Abstract
Data from spaceborne light detection and ranging (lidar) opens the possibility to map forest vertical structure globally. We present a wall-to-wall, global map of canopy height at 1-km spatial resolution, using 2005 data from the Geoscience Laser Altimeter System (GLAS) aboard ICESat (Ice, Cloud, and land Elevation Satellite). A challenge in the use of GLAS data for global vegetation studies is the sparse coverage of lidar shots (mean = 121 data points/degree2 for the L3C campaign). However, GLAS-derived canopy height (RH100) values were highly correlated with other, more spatially dense, ancillary variables available globally, which allowed us to model global RH100 from forest type, tree cover, elevation, and climatology maps. The difference between the model predicted RH100 and footprint level lidar-derived RH100 values showed that error increased in closed broadleaved forests such as the Amazon, underscoring the challenges in mapping tall (>40 m) canopies. The resulting map was validated with field measurements from 66 FLUXNET sites. The modeled RH100 versus in situ canopy height error (RMSE = 6.1 m, R2 = 0.5; or, RMSE = 4.4 m, R2 = 0.7 without 7 outliers) is conservative as it also includes measurement uncertainty and sub pixel variability within the 1-km pixels. Our results were compared against a recently published canopy height map. We found our values to be in general taller and more strongly correlated with FLUXNET data. Our map reveals a global latitudinal gradient in canopy height, increasing towards the equator, as well as coarse forest disturbance patterns.