National Forest Inventory of Ethiopia 2014-2016

The NFI applied a country-specific stratification into five biome categories: Acacia-Commiphora, Combretum-Terminalia, Dry Afromontane, Moist Afromontane, and an additional "Other" biome class. The survey excluded sampling units located within water bodies, non-vegetated permanent land uses such as urban and industrial zones, and inaccessible or boundary-overlapping areas.

In total, 627 sampling units were planned across the country, of which 539 were accessible and measured. This stratified systematic cluster sampling design ensured statistically robust representation of Ethiopia's diverse ecological zones, providing reliable national-level estimates of forest resources, biomass, and land-use transitions.

The determination of the number of sampling units for the National Forest Inventory (NFI) was guided by three key factors: the statistical reliability required for the data, the financial and human resources available for the assessment, and the goal of enabling consistent, long-term monitoring.

To ensure optimal sampling intensity, the country was first divided into meaningful ecological strata. This stratification was a foundational step, achieved through a series of consultative meetings with experts, including foresters, plant ecologists, and statisticians. Insights from previous forest inventory efforts were also reviewed to extract valuable lessons and refine the current approach.

For the implementation of the systematic sampling design, Ethiopia's agroecological zones (defined by altitude, temperature, and rainfall) were combined with the land use/land cover map from WBISPP (2004) to create distinct, non-overlapping strata. Initially, four major strata were identified. However, due to ecological variations within the extensive woodland areas in the north, southwest, and east, this category was further subdivided to ensure balanced sampling intensity across regions.

Field data were gathered through a combination of direct observation, physical measurements, and interviews conducted at multiple hierarchical levels. These levels included the main Sampling Units (SUs) and their internal subdivisions: plots, subplots, Land Use/Cover Sections (LUCS), and Land Use/Cover Classes (LUCC).

Each Sampling Unit is a square area measuring 1 km × 1 km. The southwest corner coordinates of each SU align with points selected from a systematic sampling grid. Every SU contains four field plots strategically placed for comprehensive coverage. Plots are rectangular, each measuring 20 meters wide by 250 meters long, positioned at the corners of an inner 500-meter square centered within the SU. Plots are numbered clockwise from 1 to 4, starting from the top-left corner.

Each plot includes three types of subplots, designed to capture data at varying levels of detail: three Rectangular Subplots (RSP, 20 m × 10 m, 200 m²) corresponding to Level 1; three Circular Subplots (CSP, radius 3.99 m, 50 m²) corresponding to Level 2, located in the left-hand half of the rectangular subplots; and three Litter Subplots (LSP, radius 18 cm, about 0.1 m²) corresponding to Level 3, located at the center of the circular subplots. Each subplot type is numbered 1 to 3, following the layout from the start to the end of the plot.

A Measurement Point (MP) for soil and topography is placed at the center of each rectangular subplot, and a Fallen Deadwood Transect (FDT) is established at the end of each rectangular subplot to assess fallen deadwood. Each plot is further divided into LUCS, which represent areas of uniform land use or vegetation type (e.g., forest, cropland, grassland). These sections vary in shape and size based on field observations. Within LUCS, data are collected on grazing practices, crop types, forest structure, resource management, and user interactions.

Source: MEFCC (Ministry of Environment, Forest and Climate Change). 2018. Ethiopia's National Forest Inventory: Final Report. Addis Ababa, Ethiopia.