Selection ofLand Use Categories Estimation ofArea and Preparation of Spatial Maps of the Land Use Categories

Land-use stratification may lead to a large number of forest or plantation types with differing management systems, a large diversity of cropping systems, etc. Stratification is very critical since the area under different land strata could be large, covering millions of hectares, with diverse rainfall, soil and topographic conditions. Thus, multistage stratification may be needed. Select the land-use strata for monitoring based on criteria such as extent of area under land-use system, distribution of area under a given land-use system into areas under different rainfall, soil and management systems. It may not be feasible to select all the strata for each land-use

Table 16.1 Stratification of forest and non-forest land-use categories

Ecological

Type of

Crown

Land use

zone

forest

cover (%)

Altitude (m)

Tropical

Tropical moist

- Degraded

->70

<500

forest

deciduous

- Secondary

-50-70

500-1,000

forest

- Old growth

-10-50

>1,000

<10

Tropical

- Degraded

->70

<500

dry forest

- Secondary

-50-70

500-1,000

- Native

-10-50

>1,000

-<10

Species

Rainfall

Age group

Density of

(cm/year)

(years)

trees

Plantations

Eucalyptus

50-100

<5

<2,000

100-200

5-10

2,000-4,000

>200

10-20

>4,000

>20

Pines

50-100

<5 years

<2,000

100-200

5-10 years

2,000-4,000

>200

10-20 years

>4,000

>20 years

Seasonality

Rainfall

Crop system

Crops

(cm/year)

Cropland

Annual crops

-50-100

-100-200

- Irrigated

- Sorghum

->200

- Rainfed

- Maize

- Rice

Perennial

-50-100

- Irrigated

- Coconut

crops

-100-200

- Rainfed

- Mango

->200

Agroforestry

-50-100

- Irrigated

- Mixed:

system

-100-200

- Rainfed

tree + annual

->200

crops

- Orchards

system because of constraints of data and financial and other resources. Obtain a land-use map of the country with land-use categories and wherever possible stratify each category into subcategories based on vegetation type, management system and other criteria. Obtain the area under each strata consisting of land-use category, subcategory and any additional criteria. Higher the levels of stratification into homogenous categories, lower will be the error in estimation. Area under different strata and its spatial distribution is necessary for sampling for long-term monitoring. An illustration of land-use stratification, based on IPCC guidelines, is given in Table 16.1.

The national land-use map showing spatial distribution of different strata should be overlaid on a latitude-longitude grid for sampling. If GIS facility is available, different layers of maps, each representing a land-use or management system or rainfall zone or other feature, could be overlaid.

16.8 Estimation and Monitoring of Biomass Stocks and Changes

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