A Simplified GIS Approach to Modeling Global Leaf Water Isoscapes

Abstract

The stable hydrogen (δ2H) and oxygen (δ18O) isotope ratios of organic and inorganic materials record biological and physical processes through the effects of substrate isotopic composition and fractionations that occur as reactions proceed. At large scales, these processes can exhibit spatial predictability because of the effects of coherent climatic patterns over the Earth's surface. Attempts to model spatial variation in the stable isotope ratios of water have been made for decades. Leaf water has a particular importance for some applications, including plant organic materials that record spatial and temporal climate variability and that may be a source of food for migrating animals. It is also an important source of the variability in the isotopic composition of atmospheric gases. Although efforts to model global-scale leaf water isotope ratio spatial variation have been made (especially of δ18O), significant uncertainty remains in models and their execution across spatial domains. We introduce here a Geographic Information System (GIS) approach to the generation of global, spatially-explicit isotope landscapes ( = isoscapes) of “climate normal” leaf water isotope ratios. We evaluate the approach and the resulting products by comparison with simulation model outputs and point measurements, where obtainable, over the Earth's surface. The isoscapes were generated using biophysical models of isotope fractionation and spatially continuous precipitation isotope and climate layers as input model drivers. Leaf water δ18O isoscapes produced here generally agreed with latitudinal averages from GCM/biophysical model products, as well as mean values from point measurements. These results show global-scale spatial coherence in leaf water isotope ratios, similar to that observed for precipitation and validate the GIS approach to modeling leaf water isotopes. These results demonstrate that relatively simple models of leaf water enrichment combined with spatially continuous precipitation isotope ratio and climate data layers yield accurate global leaf water estimates applicable to important questions in ecology and atmospheric science.

Refining oxygen isotope analysis in the Nasca region of Peru: An investigation of water sources and archaeological samples

“…In comparison to Knudson et al's (2009) (Gat, 1996). Also, plant and animal foods from very arid environments, such as the Nasca region, might be 18 O-enriched due to high rates of transpiration and transcutaneous water loss (West et al, 2008). In addition, bone collagen studies on regional samples (Kellner & Schoeninger, 2008) and botanical studies (Conlee, 2000) suggest that chicha was commonly consumed.…”

Progress and challenges in using stable isotopes to trace plant carbon and water relations across scales

“…isoscapes) contain a potential wealth of information regarding ecological processes (West et al, 2008;Bowen et al, 2009), which have, so far been applied at larger spatial scales (see Sect. 2.5).…”

Long-range atmospheric transport of terrestrial biomarkers by the Asian winter monsoon: Evidence from fresh snow from Sapporo, northern Japan

“…show large spatial gradients between the low and high latitudes and arid and humid regions (Sachse et al, 2004(Sachse et al, , 2006Jia et al, 2008;Rao et al, 2009) reflecting global and local hydrological cycles (West et al, 2008). Hence, combination of chain-length distribution and dual-isotope ratios ( 13 C and D) of terrestrial biomarkers provides a powerful tool to access their source regions.…”