About Forest Inventory
National Forest Inventory of India
The history of conducting forest inventory in India goes back to eighteen centuries. Assessment of the Forest Resource on a relatively large area basis (catchment basis) using statistically robust approach and aerial photographs began in 1965 when the Pre investment Survey of Forest Resources (PISFR) was launched in the country with FAO/UNDP assistance. Besides, trained and committed team from India, foreign experts were also involved in designing the methodology of forest inventory and data processing. This was also a beginning of era where assessment of the forest resources was linked to the requirement of wood based industries. The forest inventory was continued in different parts of the country with varying sampling design till 1981 when PISFR was reorganised as Forest Survey of India (FSI). Inventory remained as one of the important activity of FSI even after creation of FSI with a uniform design.
Forest Inventory conducted by FSI during 1965 to 2002
During 1965 to 1980 generally, systematic cluster sampling was used in study area. The study area was divided into suitable grid sizes (5'x5' or2½'x2½') depending upon the optimum sample size (which defines the sampling intensity) and within the selected grid a cluster of 3 to 8 sub-plots was considered for recording the data on different parameters of inventory. Whenever the information on stratification variable was available (generally, pre-stratification on the basis of aerial photographs), stratified random sampling was used, otherwise the collected data was post-stratified to increase the precision of estimates.
The late 1970s and early 1980s, were very important in inter-national as well as national forest scenario and influenced a paradigm shift in realization of role of forest resources. The forests which initially seemed inexhaustible resource under the pressure of human and cattle population were rapidly depleting and leading to overall deterioration in the environment, threatening the very existence of civilization. Therefore, strategies were framed to divert production forestry to conservation forestry. New programs like social and agro-forestry came into being. To formulate suitable strategies for the new scenario there was a need to have information at national level. Acknowledging the utility of forest resources survey in 1976, the National Commission on Agriculture recommended in its report, creation of a National Forest Resource Survey Organization. As a result of this recommendation, PISFR was converted into Forest Survey of India (FSI) in 1981. Anticipating this transcription, PISFR had started developing National level forest inventory design. A high level committee under the chairmanship of Director, Central Statistical Organization was constituted in 1980. It was recommended that systematic sampling should be used for national forest inventory.
During the last decade of 20th century, the role of forests was again redefined by including the additional parameters like carbon sequestration in plant community and in forest soil, regeneration status, naturalness etc. Taking it as opportunity to fulfill its dream of conducting national level forest inventory (NFI), FSI conducted a series of workshops and meetings with experts and came out with an integrated approach in 2001-02 in which forest inventory with provision of capturing above mentioned parameters be conducted in a cycle of two years. This approach was followed and the estimates were being improved cycle after cycle till 2016.
Initiation of National Forest Inventory in India
As the forest inventories carried out in different parts of the country since 1965 were in a different time frame, it was not possible to generate national level estimates on growing stock, area statistics and other parameters with reference to one point of time. At the beginning of the 10th five-year plan in 2002, considering the resource limitation, a new sampling design was adopted to generate national level estimates of various parameters including those of growing stock from forests which is described in the following paragraphs.
Sampling Design for NFI (2002)
A two-stage sampling design was adopted for national forest inventory. In the first stage the country was stratified into homogeneous strata, based on physiography, climate and vegetation called the ‘physiographic zones'. The civil districts within the physiographic zones were taken as sampling units. The 14 physiographic zones were identified in the country; Western Himalayas, Eastern Himalayas, North East, Northern Plains, Eastern Plains, Western Plains, Central Highlands, North Deccan, East Deccan South Deccan, Western Ghats, East Ghats, West coast and East coast.
A sample of 10 percent districts (approx. 60 districts in the country) distributed over all the physiographic zones in proportion to their size were selected randomly for detailed inventory of forest and trees outside forests. In the second stage, separate sampling designs were followed for detailed inventory of forest and TOF.
Second stage sampling design for forest area
The 60 districts selected in the first stage were taken for detailed inventory of forests. The Survey of India (SOI) topographic sheets on 1:50,000 scale (size 15'x15' i.e. 15 minutes latitudes and 15 minutes longitudes) of the district were divided into 36 grids 2 1⁄2* x 2 1⁄2* which were further divided into sub-grids of 1 1⁄4* x 1 1⁄4* forming the basic sampling frame. Two of these 1 1⁄4* x 1 1⁄4* sub-grids were then randomly selected to lay out the sample plots. Other forested sub-grids in the districts were selected systematically taking first two sub-grids as random start. If the Centre of the selected, 1 1⁄4* x 1 1⁄4* sub-grid does not fall in the forest area then it was rejected. If it fell in the forest area, it was taken up for inventory. The intersections of diagonals of such sub-grids were marked as the Centre of the plot at which a square sample plot of 0.1 ha area was laid out to record the measurements on tree diameter at breast height (dbh) and height of sampled trees species. In addition, within this 0.1 ha plot, sub-plots of 1mx1m were laid out at north-east and south-west corner for collecting data on soil and forest floor (humus and litter) etc. The data regarding herbs, shrubs and climbers was collected from four square plots of 1mx1m and 3mx3m in all four directions along the diagonal, 30m away from centre of 0.1 ha plot.
Besides forest inventory, TOF inventory was also started. This design was continued till 2016. However, as per the national and international requirement, FSI again modified its sampling design.
New NFI Design
Sampling Scheme for NFI
Under the new design, a nationwide uniform grids of 5 Km x 5 Km have been created. A forest layer has been developed by combining the digital layer of RFA boundaries/greenwash. Overlaying the forest layer on grid layer, the intersection of these two layers provided the general sampling frame for NFI. On the basis of forest layer, every grid was identified as either forested grid or non-forested grid (TOF grid). All the grids have been numbered from 1 to 5. Choosing one of these numbers as random start and thereafter all grids containing that number marked as forested grid, were chosen for data collection. Within the selected forested grid denoting 25 Km2 forest area, a random point using GIS gives the centre of the sample point from where the detailed data is collected as per sample design. The diagram shows, the cluster of four circular sub-plots each with radius of 8m in a fixed pattern. Here, the central subplot-1 is laid out at the point with assigned lat-long. Other three subplots-2, 3 and 4 are to be located at a distance 40m in north, 120º and 240º from north respectively. It is also envisaged that out of these plots, around 10% plots will be measured for biodiversity indicators, health indicators, climate change indicators and soil characteristics.
The NFI is designed to include all forest area of the country. The forest area is notified by the Government. The digital boundaries of forest area are not available for entire country. This is available for 12 states and for remaining states green-wash area as depicted in Survey of India topographic sheet will be taken as proxy of RFA (Survey of India shows some area as green in their topographic sheets usually referred as 'green-wash'. This green-wash depicts: recorded forest areas and other traditional forest areas at the time of survey for topographic sheets preparation).
The NFI envisages measurement of about 35,000 sample points across the country in the five years. Every year 20% sample points will be covered. In other words, it will measure a fixed proportion of the plots in each State, each year. Around 10% of the identified sample plots will be used for special studies related to biodiversity and soils.
The sample size is optimized so that enough plots are measured to satisfy precision standards for area and volume estimates. There is provision that if States wants more precise estimates then they may choose to increase the sample size by installing additional plots.
Layout of the sample plot
|Cluster of four sub plot of 8 metre radius each from the centre of sub-plot -1 at Azimuth at 360 degrees, 120 degrees and 240 degrees at a distance of 40 metre.|
|Three 1 m x 1m plot for soil and forest floor with centre at a distance of 20 metre from the centre of sub-plot -1 in the direction of sub-plot 2, 3 and 4.|
|Two circular plots for NTFPs, for Herbs (0.6 m radius), Shrub, Climber and Regeneration and woody litter (1.7 m radius) in all four sub plots at a distance of 5 metre from the centre towards east.|
|A circular plot of 2.8 metre for stump & dead wood collection will be laid out in all four sub plots at a distance of 5 metre from the centre towards east.|
|Set of Herbs, Shrubs-climbers-regeneration-woody litter and stump, dead wood circular plots is concentric.|
NFI Plot Design
In order to generate information for changing requirements of
|1)||Support to States in Sustainable Forest Management|
|2)||Inventory of NTFP and other new variables|
|3)||Monitoring of Change in Forest characteristics.|
|4)||Inclusion of climate change indicators.|
|5)||Significant improvement of precision at the state / regional level etc. following changes have been proposed and brought into force.|
From two stage sampling design to Uniform grid based (5kmx5km) systematic sampling scheme; Re-measuring of same plot after 5 years (doubles the workload);Single plot design to cluster of sub-plots design; There is provision of permanent and temporary plots; provision for nationally relevant data; use of GIS and satellite imageries, for enhancing precision of estimates and developing small areaestimates; and flexibility to increase sample size at state and local levels so that combined effort may yield information at national, regional and local levels.
Sampling design for TOF (Rural)
The rural TOF area includes all areas outside the traditional/notified Reserved and Protected Forests but excludes notified urban areas. As for any survey, sampling frame is required, sampling frame for rural areas is prepared by headquarter using remote sensing and GIS technique.
The sampling frame for rural TOF has been obtained from the nation-wide uniform grid of 5 km x 5 km as explained earlier. The frame of rural TOF excludes all grids, which have been identified for forest inventory and urban TOF inventory. The inventory cycle for TOF is taken as 10 years. Thus, all grids in the frame are numbered from 1 to 10. Within the selected grids for a particular year, two-phase sampling design is used. In the first phase, grids are stratified into block, linear and scattered stratum using high resolution remote sensing satellite data. In the second phase, one random sample point will be laid out in each grid. Generally, in a grid there will be one sample point. The list of selected grids and plot centre with latitude and longitude will be provided by the headquarter to zonal offices. The methodology used for stratification of tree resources of the grid into block, linear and scattered is described as follows.
The cycle of TOF inventory has been decided to be 10 years. As is already known, TOF inventory has two parts 1) Rural2) Urban. Different methodologies have been adopted using the same framework of 5kmx5km grids for TOF (R) and TOF (U) inventory. All the area grids are numbered from 1 to 10 for TOF inventory as well. For list of all urban towns and cities, census 2011 data have been used which has name and area. The latitude and longitude of centroid of all such towns have been arrived at using BHUVAN and GOOGLE earth portal. Using the latitude and longitude of centroid and area of the towns, a buffer zone of appropriate radius has been created. At state level, this layer of buffer area has been considered as a proxy of digital urban area of that state. In a GIS framework, this urban layer is overlaid on the 5km x 5km grid layer. All such grids intersecting the urban buffer layer have been considered as urban grid for TOF Urban inventory. All urban grids which are numbered 'one' will be considered for 1st year TOF (Urban) inventory. On grid basis, towns are selected and UFS blocks are randomly selected from these towns and are used for inventory.
Optimum plot size
The optimum size of the plot for each stratum has been determined by FSI by conducting a pilot study in the past. The optimum plot size for Block and Linear strata is 0.1 ha and 10m strip, respectively. In case of scattered stratum, as the new design is grid based, instead of district as being used earlier, the scattered plots will be identified as hilly or non-hilly on the basis of altitude of a particular plot and same will be mentioned against each plot. The optimum size of sample plot has been fixed as 3.0 ha for non-hilly area and 0.5 ha for hilly area.
Sample points are randomly generated within each grid for selected stratum and the data on pre-decided variables like dbh, crown diameter, species name and category of plantation, etc. are collected on designed formats. The complete enumeration of all the trees of 5 cm and above dbhwill be carried out in the prescribed formats. Data processing will be carried out using data processing module developed for this purpose by FSI.
Sampling Design for TOF (Urban)
The study area for this survey is considered as urban centers as defined by office of Registrar General of India. Sampling frame for urban areas has been prepared by National Sample Survey Organisation (NSSO) under the Ministry of Statistics and Programme Implementation, Government of India. This organization conducts surveys by the name of 'Urban Frame Survey' (UFS). They divide all urban centers of a district in blocks called 'UFS blocks'. These blocks are having well defined boundaries, and are formed on the basis of 600-800 population or 120-160 households; they cover the whole area within the geographical boundary of a town including vacant lands.
To identify the urban grids from the frame of the 5 km x 5km grids excluding grids marked for forest inventory, the list of urban towns and cities as per Census 2011 has been used. The centroid of all such towns/cities has been determined with the help of BHUVAN and GOOGLE earth. The area of all such towns/cities is also known from the census data. Using area of urban towns/cities, a buffer area has been created around the centroid of all towns/cities. A random point has been laid out in the buffer area for urban inventory. The list of urban grids along with latitudes and longitudes to be inventoried in a particular year will be given to zonal offices for field work. The zonal offices will identify the UFS block corresponding to selected sample point from NSSO. For this purpose, they may take toposheets or screen prints of Google/Bhuvan imagery of the selected sample point, which may be helpful in identification of UFS block. The inventory is to be done in the selected block and all trees above 5 cm diameter are to be recorded in the designated field forms.
Preparation of National Forest Inventory Database System (NFIDS) As per the Tenth Five Year Plan approval, FSI is conducting National Forest/Tree Inventory along with the vegetation survey. As the objectives of the inventory have been redefined with inclusion of several new parameters, the methodology has also been significantly modified. As per the revised methodology a National Forest Inventory Database System (NFIDS) based on database software (MS Access) using front end on Visual Basic has been prepared. The data base system has the following modules:
|National Forest Inventory/TOF Data Entry Module.|
|National Forest Inventory/TOF Data Processing Module.|
|National Forest Inventory/TOF Reporting Module.|
|National Forest Inventory/TOF Result Database Module.|
|General interface with forest cover.|
Estimation of carbon stock in India's forest
Forest Survey of India has been one of the major contributors on forest biomass estimation and carbon stock change. In India's Initial National Communication (INC) submitted to United Nation Framework Convention on Climate Change (UNFCCC) in 2004, FSI estimated forest carbon of woody growing stock. In 2010, FSI has completed estimation of forest carbon stock and change between two-time period viz. 1994 and 2004 as part of Second National Communication (SNC) to UNFCCC. Since inventory of forest /TOF is a regular process of FSI which forms the basis for estimation of carbon stock, FSI is estimating carbon stock in India's forest, both at national and state level, using forest inventory data, forest cover mapping and forest type mapping information.
FSI has been estimating the carbon stock in the India's forest as per the methodology of 'Good Practices Guidance' (GPG) developed by Inter-governmental panel on Climate Change (IPCC). For estimation of emission factors for different strata, data of National Forest Inventory (NFI) has been used. Biomass equations/factors were developed through a special study conducted by FSI. GIS techniques were used for synthesizing the data and to estimates carbon stock under different carbon pools.
In the present assessment ISFR-2015 total carbon stock in forest is estimated to be 7,044 million tones. There is an increase of 103 million tons in the carbon stock of country as compared to the last assessment. (i. e. between years 2011 to 2013)
Ongoing activities in TFI Unit
Biodiversity study for FTG's within FTM Project
For FTM Project of NFDMC, task of estimating sample size and generation of sample points for Biodiversity study for 16 Forest type groups has been assigned to TFI.Main objective of the study is to highlight role of understory vegetation (herbs and shrubs) in forest ecosystem and underlying biodiversity. To access ground vegetation (species richness and abundance), sample design, methodology and field forms have been generated and development of data entry module and processing algorithm is in pipeline.
Removal of fuelwood, fodder and small timber in Forest Fringe Villages from forest of India
Main objective of this task is to study removal of fuelwood and fodder from the forests by the inhabitants of FFV's to analyze their dependence and quantity of extractions. Assigned work started with sample size generation followed by development of methodology and formats for data collection.
Inventory of TOF in Rajasthan
The project on Inventory of Trees Out-side Forests (TOF) in Rajasthan, is undertaken by FSI. The field work in state is being carried out by Rajasthan state forest department. The data processing and report writing will be done by FSI.
Project for Forest Cover Mapping and Inventory of Forest/Tree Resources in Nagaland
Nagaland state, which has forest cover of 12,868(77.61% of the state's geographical area) for preparation of Working Plans of its nine forest divisions spread over 11 districts, a new project has been completed. The project objective was achieved as indicated by Nagaland Forest Department using remote sensing data and inventorying of forest and tree resources including vegetation survey and estimation of soil carbon as per the methodology laid down by FSI. The different types of satellite data (LISS-III and LISS-IV 2011-12 multispectral data, ASTER DEM, SOI Topo sheets 1:25000/1:50000) were used for the execution of this project. The District wise information's about the forest cover map showing the categories of forests by Density classes, forest type map, slope map, aspect map, drainage map, land use area map, DEM (District and state wise) and FC draped (District and state wise) completed and submitted to Nagaland forest department.
To assess the forest resources of Nagaland state, forest inventory work was carried out by FSI which has been completed. The Forest inventory results have been submitted to Nagaland forest department. The final report is under printing.
On the request of West Bengal forest department, Forest Survey of India is conducting a base line survey in collaboration with West Bengal forest department for forest growing stock under the'West Bengal Forest and Biodiversity Conservation Project' (WBFBCP) being implemented by forest department of West Bengal with assistance of Japan International Cooperation Agency(JICA) in 8 districts of West Bengal viz. Bankura, Birbhum, Vardhaman, Cooch Bihar, Darjeeling, Jalpaiguri, PaschimMadinipur and Puruliato establish bench mark. The duration of the implementation of the project is 8 years starting from 2012-13 to 2019-20.
Objectives of this project are to improve forest ecosystem and conserve biodiversity by undertaking afforestation, regeneration and wildlife manangement activities through Joint Forest Management approach.