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Accueil du site → Projets de développement → Projets de recherche pour le Développement → 2018 → SPATIAL PALEO AND CONTEMPORARY RECONSTRUCTION OF DRYLAND CARBON DYNAMICS USING REMOTE SENSING AND DENDROCHRONOLOGIES

United States Department of Agriculture (USDA) 2018

SPATIAL PALEO AND CONTEMPORARY RECONSTRUCTION OF DRYLAND CARBON DYNAMICS USING REMOTE SENSING AND DENDROCHRONOLOGIES

Dryland Carbon Dynamics

United States Department of Agriculture (USDA) National Institute of Food and Agriculture

Titre : SPATIAL PALEO AND CONTEMPORARY RECONSTRUCTION OF DRYLAND CARBON DYNAMICS USING REMOTE SENSING AND DENDROCHRONOLOGIES

Identification : NEV00764

Pays : Etats Unis

Durée : START : 01 JUL 2018 // TERM : 30 JUN 2021

Résumé
The productive capacity of drylands is not well understood where forests are thought to be moreproductive but surprisingly in 2011 drylands were more productive !! Some 50% of vegetation consists of carbon, because plantsabsorb carbon for photosynthesis with sunlightand oxygen to produce sugars.These sugars are used to build plant cell walls, organs, and hormones which are also examples of carbon storage. The rate of carbon (C) storagein vegetation is called net primary productivity (NPP) or the total weight of carbon stored above and below ground in a specific area in a year. Trees that grow in seasonal environments store this carbon in tree rings which show the annual growth of the tree and in total the tree’s age. The ring width varies with the amount of growth in that year where thicker rings indicate higher production and vice versa. Production in drylands is limited by the amount of water available. Shortages (drought) and abundances of water determine the tree’s ring width. This relationship allows reconstruction of historical rainfall records as far back as 5,000 years.Some satellites can measure the amount of reflected red (R) and infrared (IR) sunlight from a plant canopy. IRis highly reflected from leaves relative to R light. Red light is highly absorbed byleaves for photosynthesis and the fraction of light used for photosynthesis is approximately equal to the ratio of IR to R light or IR/R. This relationship is proportional to the amount of leaves or biomass in the canopy. If there are many leaves in the canopy then the IR/R ratio increases and if there are less leaves, it decreases. The amount of IR/R summed up over a growing season is approximately equal to NPP. Summed IR/R correlates nicely with tree ring width and variability. This correlation has allowed reconstruction of the satellite sensor’s summed IR/R over 200 to 500 years ago. However, in the past these reconstructions have been done in time and not space. Spatial reconstructions produce time series of maps of NPP from 200 or more years ago, i.e., reconstruction for each year or 200 or more maps of NPP would be produced. We have produced and validated 303 NPP maps of California using a tree ring record from 1700 to 2003. We propose to reconstruct the NPP record for Nevada, the US, and North America’s (NA) drylands for the same period using historical archives of tree ring width and satellite data. This will lead to a better spatial and temporal understanding of above- and below-ground carbon dynamics for these different study areas. For example, we will see in the mid 1700’s during particularly wet conditions where Nevada was most productive and during the 1930’s, 1950’s, 1970’s and late 1990s droughts locations where the state was the least productive. We will be able to establish longer term baselines and develop hypotheses about what the drivers of these dynamics may be as well as seek solutions from the areas where we see recovery.

Performing Institution : UNIVERSITY OF NEVADA RENO, NEVADA 89557
Investigator : Washington-Allen, RO,

Présentation : USDA (NIFA)

Page publiée le 10 décembre 2019