Document: MIC-3-59-62

Carbon in semiarid pinyon-juniper woodlands: Implications of patch-scale estimates.

EBINGER, M.H.*, D.D.BRESHEARS and S.R.KAMMERDIENER

Los Alamos National Laboratory, Los Alamos, NM 87545, USA ¹

Abstract:
Many semiarid ecosystems lie within a gradient of increasing coverage by woody plants, from grassland with no cover by woody plants to forests or shrublands with nearly complete cover by woody plants. These ecosystems are a mosaic of two patch types: Canopy patches of woody plants and the intercanopy patches that separate them. Carbon inventories are expected to differ fundamentally between these two patch types, and, perhaps to a lesser extent, between different species within the same patch type. Evaluating the carbon inventories at the patch scale and across gradients of woody vegetation is an important step in understanding how carbon sinks and sources function in semiarid climates. We estimated patch-scale carbon inventories for pinyon and for juniper canopy patches and for intercanopy patches at the Mesita del Buey Pinyon-Juniper Woodland Site in Los Alamos, NM and extrapolated them across an elevational gradient. Our three objectives were to measure the carbon content of foliage, wood, litter, and soil; to estimate carbon inventories of canopy and intercanopy patches; and to evaluate the implications for carbon inventories over gradients with varying proportions of canopy and intercanopy patches. We found that carbon inventories of canopy patches greatly exceeded the carbon inventory in the intercanopies. The ratio of above-ground carbon to soil carbon was also much larger in canopy patches than in the intercanopy. We also found an increase in canopy carbon with elevation: More carbon was found in soils and above-ground in the higher elevation sites than in the lower elevation sites. Our data suggest that increased woody vegetation could sequester carbon especially in soils, but potential losses of stored carbon to the atmosphere could negate any gain in storage. With increased woody vegetation in more patches due to thickening of woody vegetation, loss of carbon due to fire, drought-induced tree mortality, and erosion are processes that must be balanced to sustain carbon sequestration.

Keywords: carbon, pinyon juniper woodlands, semiarid ecosystems, carbon sequestration

This abstract is being presented at: 10:30 AM in session:
CARBON STORAGE