A Working Framework for Quantifying Carbon Sequestration in Disturbed Land Mosaics

We propose a working framework for future studies of net carbon exchange (NCE) in disturbed landscapes at broad spatial scales based on the central idea that landscape-level NCE is determined by the land mosaic, including its age structure. Within this framework, we argue that the area-of-edge-influence (AEI), which is prevalent in many disturbed, fragmented landscapes, should constitute a distinct ecosystem type since numerous studies have indicated unique ecological properties within these areas. We present and justify four working hypotheses currently being tested in northern Wisconsin, based on this framework: (1) the area of an ecosystem that is influenced by structural edges (e.g., AEI) has NCE that is significantly different from the ecosystem interior; (2) age structure and composition of an ecosystem play critical roles in determining the ecosystem’s contribution to the cumulative net ecosystem production (NEP) of the landscape mosaic; (3) the relative importance of different structural and biophysical controls of carbon exchange is ecosystem dependent; and (4) the frequency and intensity of disturbances in time and space control the cumulative NCE of the land mosaic through alteration of ecosystems that vary in age, structure, physical environment, and interactions. In addition, we describe five different research approaches to quantify NCE at broad scales, including biometric estimations, ecophysiological methods, micrometeorological methods, applications of remote sensing and GIS, and ecosystem models.