Analysis of forest biomass and carbon stock using photogrammetry and lidar in support of the National Forest Inventory

Funded by: NSERC Strategic GRANTS - Biocap foundation

Project duration : November 2003 - October 2006

• Mark Gillis / Canadian Forest Service (Pacific Forestry Centre)
• Werner Kurz / Canadian Forest Service (Pacific Forestry Centre)
• Benoît St-Onge, P.I. / University of Québec at Montreal (Geography)
• Paul Treitz / Queen's University (Geography)
• Mike Wulder / Canadian Forest Service (Pacific Forestry Centre)

Short term objectives and project scope

The Canadian Forest Carbon Accounting Framework is designed to meet the information requirements for Kyoto protocol reporting on the national carbon balance of forest ecosystems. It relies in great part on the National Forest Inventory (NFI), an inter-agency effort coordinated by the Canadian Forest Service (CFS). The NFI will constitute the only standardized national dataset available on the condition and extent of Canada's forests. The overall short-term goal of this project is to facilitate the implementation, and the future updating, of the NFI by providing accurate, cost efficient, and operational methods to produce key NFI attributes, with special attention to biomass and carbon stocks. Short-term objectives are related to the national grid of NFI photo-plots , a country-wide mesh of plots in which forest attributes will be quantified using aerial photographs and field measurements. The methods we seek to develop will improve the estimates of those that are currently employed, and concern:

1. The estimation of current above-ground biomass, and the amount of carbon (C) stored therein , and of other key attributes of the NFI . This will consist of using lidar data to create canopy height models (CHMs), and ameliorate current CHM processing methods to produce accurate estimates of above ground biomass and carbon (C) quantities for pilot photo-plot sites across Canada. The aim is to replicate the NFI data with lidar estimates by minimising the error to a large extent. Other key information such as canopy height and percent cover are also targeted, as well as ground topography.
2. The estimation of changes over time in the above-ground biomass and stored C . For each photo-plot, a temporal series of CHMs will be created using a combination of lidar-based ground topography and photogrammetric reconstructions of canopy topography. By adopting the methods developed in § 1 to the characteristics of photo-lidar CHMs, we will perform biomass and C estimations over different dates and calculate changes. This combination of lidar and photogrammetry is also designed to allow the monitoring of NFI photo-plots in the future using aerial photography alone, or high resolution space images such as IKONOS. Therefore, once lidar data is acquired, retrospective studies and future monitoring will only require, respectively, the retrieval of archived photographs, or the use of new ones.
3. The detection of changes over large areas to identify sites that need remeasurement . The on-going NFI in future requires remeasurement in the photo-plots regularly to account for changes. Not all plots will experience change over a given period. In order to optimize remeasurement work, change detection methods using Landsat imagery will be adopted to identify plots which show significant change, and a clear need to be revisited. Changes detected on diachronic Landsat images will be verified based on aerial photographs acquired during the same years as the Landsat images.

Long-term objectives

The primary long-term objective is to increase the accuracy and credibility of overall national estimates of carbon storage . This project will provide new methods and datasets, based on pilot sites, for which lidar data is already available. We envisage the possibility of simultaneous acquisition of lidar and photographic data so that each photo-plot is described by both data types within one survey. This would facilitate the application of methods developed in this project to a great number of NFI photo-plots representing a wide range of ecosystem types. The credibility of C estimates is a key Kyoto reporting issue. Secondly, we seek to increase our knowledge of forest dynamics , with particular attention to carbon fluxes and storage. The retrospective reconstruction of CHMs will significantly enhance our understanding of spatio-temporal growth patterns, effects of disturbances and gaps, harvesting and regeneration rates, etc . These gains will strengthen our understanding of C-related processes, as well as forest productivity, and could lead to findings helpful to the forest industry. Thirdly, we seek to help develop knowledge on the effect of past climate changes on the carbon dynamics . The methods we will develop may help estimate growth rates over different historical periods of the recent past for various environments, and may bring the opportunity to study trends in forest growth.

For information concerning the project, please contact:
Benoît St-Onge, Ph.D.
Associate professor / Department of Geography
Head of the Graduate GIS Program
University of Quebec at Montreal
C.P. 8888, succ. Centre-Ville
Montréal (Québec) Canada
H3C 3P8
Tel. +1 (514) 987-3000 ext. 0280#
Fax: +1 (514) 987-6784
St-Onge.Benoit@uqam.ca
www.geo.uqam.ca