NASA Dryland C Cycle Project

Leveraging Field Experiments, Satellite Data and Models to Improve Understanding of the Role of Semi-Arid Ecosystems in the Global Carbon Cycle

Dryland ecosystems represent Earth’s largest biome, making up over 40% of the planet’s terrestrial surface and supporting the livelihoods of billions of people. Semi-arid regions have been shown to play the dominant role in the inter-annual variability (IAV) and long-term trend of the terrestrial carbon, C, sink (Poulter et al., 2014; Ahlstrom et al., 2015), yet our understanding of C cycling in these water-limited ecosystems remains notably poor. 

In this project, we will join remote sensing, on-the-ground measurements, and modeling for a coordinated set of core sites in the semi-arid southwestern US to assess the key contributions of different cover types to semi-arid ecosystem C cycling. We will link ground-based analyses with satellite data to significantly advance our understanding and our capacity to remotely sense dryland ecosystems at multiple scales. We will then employ these data to test, optimize, and further develop the process-based ORCHIDEE DGVM to expand our investigation worldwide into the causes and contributions of semi-arid ecosystem C cycle variability.

Map of core sites (stars) for the NASA Dryland C Cycle Project

We aim to answer the following key questions related to how differing assemblages, sensitivities, and strategies of varied semi-arid organisms and cover types respond to highly dynamic moisture variability interact and contribute to overall net CO2 flux IAV:

  1. How important for CO2 flux IAV are different plant strategies for accessing and redistributing moisture from different soil depths during periods of moisture stress?; and
  2. How do the asynchronous response times of vascular plants, biocrusts, and soil heterotrophs to rainfall pulses contribute to CO2 flux IAV variability, and does their contribution depend on when in the year the rainfall pulses occur (growing season vs. non growing season)? 
Workflow and three main objectives for the project
Project Team:
  • Lead PI: Natasha MacBean (Indiana University)
  • Co-Is:
    • Sasha Reed (USGS)
    • William Kolby-Smith (University of Arizona)
    • Ben Poulter (NASA GFSC)
    • Compton J. Tucker (NASA GSFC)

This project is funded by a NASA Carbon Cycle Science Program Grant No. 20-CARBON20-0063.