GEO-TREES aims to become a network of 100 CORE Biomass Reference Measurement (BRM) sites and 200 supplementary BRM sites.
BRM SITE REQUIREMENTS
Biomass Reference Measurement sites (BRM) are in situ forest measurement sites with a common standard for high-quality data acquisition, transparent measurement protocols, long-term monitoring, and measurements traceable to SI units.
GEO-TREES will be established through collaboration with existing international networks of high-quality forest plots that use standard forest monitoring protocols.
The Forest Biomass Reference System will be centered on 100 core BRM sites representing forests around the world, with strong priority placed on the tropics. Core sites will consist of long-term intensive measurements of forest biomass. An additional 200 supplementary BRM sites will be used to ensure full representation of the main environmental and anthropogenic dimensions over which forests occur globally. Supplementary sites will involve less intensive biomass sampling, but will provide a strategy for gap-filling under-represented areas.
The raw biomass data collected by the GEO-TREES project will be made publicly accessible through the GEO-TREES web portal. To deliver these high-quality data over a sustained period in dozens of countries requires skilled teams hosted by institutional partners. The labor and skill demanded for the groundwork are high, and conditions of work are often insecure and difficult. It follows that for in situ data to be shared openly GEO-TREES partners will be fairly and systematically funded with adequate provision of training and career development. The intellectual property of the primary stem and species data remain with the principal investigators of each site.
Core BRM sites meet the following measurement requirements:
- Forest inventory on 10 existing 1-ha permanent sample plots. Each tree is mapped, its diameter measured and species identified. Plots have been inventoried on a regular basis in the past and be accurately geolocated;
- Air borne lidar scanning (ALS) covering 1,000 ha at each of the 100 core sites and associated supplementary sites will be regularly surveyed. ALS provides accurate and precise above-ground biomass maps over landscape scales that are essential for the validation of satellite-based biomass sensors;
- Terrestrial lidar scanning (TLS) of three hectares within each of the 100 core sites will be surveyed every five years. TLS provides more direct and accurate site-specific measurements of wood volume and total tree height, both critical for biomass estimation;
- Availability of a weather station and automated soil moisture monitoring (encompassing the landscape-scale variation in soil moisture) will be implemented where possible.
GEO-TREES sites will follow the CEOS LPV biomass protocol that was written by the Earth Observation and ecological communities. This document represents the current state of knowledge and data gaps for operational validation of satellite products on a global scale. The focus lies on standardized intercomparison and validation across products from different satellite, algorithms, and agency sources.
GEO-TREES BRM sites
The map below provides a first estimate of potential BRM sites based on an analysis of representativeness of sites with respect to environmental variation among forested areas globally (Labrière et al. 2022). We welcome suggestions and insights from the community on high-priority areas for GEO-TREES sampling.