Methods for Estimating Above Ground Biomass

Above-ground biomass includes all biomass in living vegetation, both woody and herbaceous, above the soil including stems, stumps, branches, bark, seeds and foliage. Above-ground biomass is the most visible of all the carbon pools, and changes in it are an important indicator of change or of the impact of an intervention on benefits related to both carbon mitigation and other matters. Above-ground biomass is a key pool for most land-based projects. The features and the need for measuring and monitoring above-ground biomass, its importance to national greenhouse gas inventory and different project types as well as the frequency of measurement of the pool are described in Chapter 4. The different methods available for estimation and monitoring of above-ground biomass pool are described in Chapter 9. Among all the methods described in Chapter 9, the "plot method" is described in detail in this chapter. The rationale for selecting the "plot method" as the most suitable method includes the following factors:

• Applicability to baseline as well as project scenario measurements

• Applicability at project development and project monitoring phases

• Applicability to national greenhouse gas inventory estimation

• Suitability for all project types and projects of different tree sizes (mature and young) and density (dense and spare) of tree vegetation

• Simple and cost-effective

• Suitability for long-term monitoring

The "plot method" is extensively used in forest inventory programmes and by project managers and evaluators for estimating and monitoring roundwood production or carbon stock changes. Researchers in forestry, ecology and agriculture routinely adopt this method not only for estimating the changes in biomass stock, but also for monitoring biodiversity and production of commercial timber, fuelwood and grass. The "plot method" is further used for estimating biomass changes in cropland as well as grassland projects. The "plot method" is described in reports, manuals and books Special Report of Intergovernmental Panel on Climate Change on Land Use Land-Use Change and Forestry (Watson et al. 2000), Winrock Carbon Monitoring Guideline (MacDicken 1997), FAO (Brown 1997), Revised IPCC 1996 Guidelines (IPCC 1996), IPCC Good Practice Guidance (IPCC 2003), USEPA and LBNL (Vine and Sathaye 1999), CIFOR Methods (Hairiah et al. 2001), GHG Inventory

Guidelines 2006 (IPCC 2006) and Forest Inventory (Kangas and Maltamo 2006). This chapter presents a detailed description of methods, procedures, and steps for measurement, estimation and monitoring of above-ground biomass stocks and changes in those stocks.

Broad approaches to measurement, estimation and monitoring of carbon stocks, namely carbon "Gain-Loss" and "Stock-Difference" are presented in Chapter 9; the plot method can be applied to both these approaches.

Step 1

Select a land-use category or project activity

1

Step 2

Define the project boundary and map the land-use category or project area

1

Step 3

Stratify the project area or land-use category

1

Step 4

Select the 'plot method'

1

Step 5

Select carbon pools and frequency of measurement

1

Step 6

Identify the indicator parameters

1

Step 7

Select sampling method and sample size

1

Step 8

Prepare for fieldwork and data recording

1

Step 9

Decide on sampling design

1

Step 10

Locate and lay sample plots

1

Step 11

Measure the indicator parameters in the field and conduct laboratory analysis

1

Step 12

Record and compile data

*

Step 13

Analyse data and estimate uncertainty

Fig. 10.1 Steps in measurement and estimation of above-ground biomass stock

Fig. 10.1 Steps in measurement and estimation of above-ground biomass stock

The methods and steps are described for projects related to carbon mitigation as well as roundwood production. The methods and steps are also applicable to national greenhouse gas inventory for land-use categories such as forest land, cropland and grassland.

Procedure for measurement and monitoring of above-ground biomass stock All programmes and projects require estimation of above-ground biomass stock at a given point in time, annual growth rates as well as changes in stocks over a period of time. The broad steps for estimating the stock of above-ground biomass at a given point in time are given in Fig. 10.1.

10.1 Selection of Land-Use Category, Project Activity or Vegetation Type

Every project will have a set of activities aimed at achieving the project goals. A project may have a single activity such as planting eucalyptus species with a single set of management practices. Some projects may have multiple activities, where a part of the project area is under monoculture plantation and the rest could be natural regeneration of degraded forest land. These activities will have different above-ground biomass accumulation rates. Further, the density, rotation period and silvicultural practices such as irrigation and fertilizer application may vary. These different activities and management systems will have implications for carbon inventory and decisions on plot sizes, frequency of monitoring and parameters for measurement. The selection could be along the following lines:

• Land-use category (forest land, grassland and cropland), subcategory (based on soil or topography), vegetation type (evergreen and deciduous forests)

• Project activity (afforestation, avoided deforestation and grassland reclamation) and management system (density of plantation, rotation period, fertilizer application or irrigation)

10.2 Definition of the Project Boundary and Mapping of the Land-Use Category or Project Area

It is important to define the project boundary and prepare a map of the project area, demarcating the areas under different activities and management systems for carbon inventory. The project boundary definition and methods for defining project boundaries are given in Chapter 8. The project boundary may incorporate all the land-use categories, project activities and management systems. The project boundary and the extent of area under each of the land-use systems and activities should be spatially represented on a map. The following procedure could be adopted for defining the boundary and mapping.

(i) Select the land-use category and project activities A project may include multiple land-use categories, project activities and management systems. All the land-use categories, project activities and management systems should be selected separately for carbon inventory, for example:

• Land-use categories such as forest land, grassland and cropland

• Multiple activities such as promotion of natural regeneration on degraded forest land, monoculture plantation on grasslands and agroforestry in cropland

• Plantation activity may include short-rotation as well as long-rotation species

• Plantation activity may have high and low density plots and could be with or without fertilizer application

(ii) Estimation of area under the project or project activity Data on area under different activities are required for sampling as well as for estimating the above-ground biomass stock and changes. Project area estimation is required at the following phases of a project:

• Project development phase Obtain the area under each land-use category and project activity proposed in the project document.

• Project monitoring phase Obtain the actual area under each of the activities from the project authorities. The area actually brought under the project activity may differ from the area proposed at the project development phase. If the project activity is implemented in phases, obtain the data annually.

(iii) Map preparation Data on the total project area and area under different activities, subactivities and management systems should be obtained and spatially marked on a georeferenced map with a grid. The procedures for map preparation and boundary marking are described in Chapter 8. Map preparation involves the following key steps:

• Historical land records Collect any historical land-use records over the last 10-20 years to understand the trends in land-use change and to project the future land-use pattern under the baseline scenario.

• Maps Collect all the maps available for the project location: soil, vegetation, land tenure and land use.

° If maps from satellite imagery and aerial photography are available, it would be very useful to collect them. ° Using different maps, select the most important map showing the features relevant to the project, for example, land use or soils.

• Overlay Overlay different maps with various features on a geo-referenced map with many identifiable landmarks on the ground and mark the existing land-use systems such as cropland, grassland, water bodies or settlements.

• Boundary Mark the boundary of different project activities and management systems on the georeferenced grid map with relevant features such as soil quality and land use.

• GPS readings Mark the GPS readings of the polygons (plots of different shapes) under different activities and of different parcels of land.

• GIS maps If GIS facility is available, which is becoming increasingly common, different maps with various land features as well as the project activities could be overlaid along with positions needed for boundary and areas. These spatially oriented maps on a GIS platform would help the project managers and monitoring teams to

° Understand the land-use changes

° Map the area brought under different activities over the years ° Track the area brought under different management activities such as area harvested periodically or treated differently ° Locate and sample the plots and revisit the "permanent plots"

periodically ° Mark areas for estimating leakage ° Store existing data

° Easily record changes throughout the project period

• Updating of maps It is necessary to periodically update the maps, depending on any new information on changes in land use, such as implementation of project activities or area subjected to harvest.

• Maps from remote sensing Data on land-use changes, particularly the historical ones, can be obtained from interpreting satellite images over the area. Periodic updates of remote sensing maps will help in assessing

° Changes in boundaries of different land-use systems

° Changes in crown cover

° Rate of implementation of project activities

° Biomass stocks and changes

10.3 Stratification of the Project Area or Land-Use Category

Stratification is disaggregation of land area into homogeneous subunits. Land area of any project will consist of strata with varying physical and biological features, subjected to different management practices, and carbon stocks may vary because of these and other features. Stratification helps in obtaining a better representation of the land or project activities while sampling reflects the diversity of conditions that contribute to carbon stocks and minimizes costs. Stratification reduces sampling error and sampling effort by aggregating those spatial components that are homogeneous. Stratification of land area is required for the baseline as well as the project scenario (Fig. 10.2), which may be the same or different. Multistage stratification may be required, for example, to highlight broad land-use categories, features of the land, the main project activity and management systems within a project activity (as described in Fig. 10.2). The strata for sampling and monitoring refer to the last stage of disaggregated homogeneous land area or project activity such as (i) high-density short-rotation plantation on degraded forest land and (ii) grassland development with irrigation. In this handbook, a stratum refers to the last stage homogeneous unit of multistage strata for a given land-use category or project activity.

Sap Enterprise Structure
Fig. 10.2 Stratification for a multicomponent project in a village ecosystem

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  • aleksander
    How to estimate above ground biomass?
    1 month ago

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