Module 4: Land-atmosphere exchange

Jim Washburne (The University of Arizona)

Strengths of the Module

These units address the five central InTeGrate goals of:

1. Addressing geoscience-related grand challenges facing society by focusing on issues related to radiative forcing, water, and carbon cycling. These issues include a better understanding of the driving factors that affect the carbon balance and ecosystem differentiation.
2. Developing students' ability to address interdisciplinary problems by integrating energy, carbon and biophysical knowledge into a watershed-scale process model that helps explain observations.
3. Improving student understanding of the nature and methods of geoscience and developing geoscientific habits of mind by using journal articles as background reading, visualizing data with student-made graphs, and using simple conceptual models to help explain their differences.
4. Making use of authentic and credible geoscience data by incorporating Critical Zone data from the national CZO and Ameriflux network databases into their analysis of energy and carbon fluxes.
5. Incorporating systems thinking by applying conceptual energy/carbon cycle models to the analysis of field data.

Additionally, this module:

• Incorporates collaborative teams in classroom exploration of Critical Zone processes.
• Illustrates a range of conditions by comparing flux data from a wide variety of field sites.
• Provides instructional support using annotated slides.
• Develops advanced analytical/spreadsheet skills by working with large data sets, multivariable plots, and complex calculations.

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Module Goals

This module analyzes how energy and carbon flow through the Critical Zone and how they drive Critical Zone processes. Students will learn how to analyze data and use simple models to interpret spatial and temporal trends in energy flow and reservoirs at a catchment scale to answer questions about Critical Zone processes.

Learning Objectives - Students will:

• Trace primary radiative forcings through the Critical Zone using data derived from a CZO field site.
• Use CZO micro meteorological data to describe the differences between the main atmospheric fluxes at each CZO site.
• Relate carbon flux data collected at various scales to understand the regional exchange of carbon at a CZO site.
• Analyze how energy, carbon, and nutrients flow through the Critical Zone and drive Critical Zone processes.

Linking Unit Content to Overall Course Objectives

Below is a brief outline of examples within each Learning Unit where instructors can find resources that meet the overarching and the four primary learning objectives of the whole Critical Zone curriculum.

Overarching Learning Objective: Describe and characterize how interaction among the atmosphere, lithosphere, hydrosphere, biosphere, and soil (The Critical Zone) support and influence life.
Four primary objectives:

Objective 1) Identify grand challenges that face humanity and societies, ways which humans depend upon and alter the Critical Zone, and the potential role for Critical Zone science to offer solutions for these challenges.

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• Unit 4.1 & 4.2: Implicit in these modules, which focus on analyzing primary energy and carbon fluxes, is the grand challenge of better understanding the world around us. Through the act of monitoring energy and carbon budgets, we will better understand how these critical systems change over time - and quantify the anthropogenic component or influence on these fluxes.

Objective 2) Use and interpret multiple lines of data to explain Critical Zone processes.

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• Unit 4.1: There are multiple activities in this section that focus on using CZO data. These activities include "Exploring" and "Working with" the CZO met/flux database; as well as "Examining" and "Calculating" Reference Evapotranspiration.
• Unit 4.2: The activities in the first part of this unit are designed to help you "Explore" and "Work with" data in the Ameriflux database. The focus of the second part spans objectives 2-4 in that students are challenged to form a simple hypothesis regarding what Critical Zone factors might affect the annual CO2 flux.

Objective 3) Evaluate how the structure of the Critical Zone influences Critical Zone processes/services.

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• Unit 4.1: The introductory reading assignment for Rasmussen et al (2011) describes a novel approach to characterizing Critical Zone settings based on energy and mass transport processes, which are both influenced by the overall structure of the Critical Zone environment.
• Unit 4.2: The pre-class reading for this unit introduce basic carbon cycle concepts and nomenclature, while the journal article that introduces the second part (Luyssaert, 2007) illustrates how forest ecosystem carbon fluxes might be analyzed at the global scale.

Objective 4) Analyze how water, carbon, nutrients and energy flow through the Critical Zone and drive Critical Zone processes.

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• Unit 4.1: The introductory lecture on "Water & Energy Fluxes" summarizes one model for analyzing the fluxes of water and energy in the Critical Zone.
• Unit 4.2: The introductory lectures in this unit focus on "Carbon cycle and budgets" and "Eddy Correlation and modeling" are designed to introduce you to the basics of this rather complicated part of the Critical Zone.

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Assessment

Many of the activities include fact-based queries but also include the construction of various graphs. The main summative activity is at the end of the second unit where the students must construct a testable hypothesis linking ecosystem function with energy and carbon fluxes.

• Unit 4.1: Using data derived from the CZO database, calculate Penman-Monteith Reference ET and compare with a reference site.
• Unit 4.2: Using data derived from the Ameriflux database, develop a simple hypothesis on the linkage between ecosystem function and expected carbon fluxes that can be tested against observed measurements from one or more sites.

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Module Outline

These two units follow a similar structure (introduction, data exploration, data analysis, and synthesis) to facilitate student and teacher use.

• Unit 4.1: Energy Budgets (Two 75 min class sessions)
• Analyze energy flux data collected at a CZO site of interest and calculate reference ET.
• Unit 4.2 Carbon Budgets (Two 75 min class sessions)
• Analyze carbon flux data collected at an Ameriflux site of interest to better understand the regional exchange of carbon.

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