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Prior to inventory, a "stratification" needs to be done. This is valid also in a complete inventory (when all stands in the analysis area are included), since some general inventory parameters are set in this part. Considering cost-efficiency, the inventory is commonly based on a two-stage sampling procedure. Here, this starts with selecting the imported stand register of interest, i.e. the analysis area to be in-field inventoried by plotwise sampling in PPS-sampled stands. | Prior to inventory, a "stratification" needs to be done. This is valid also in a complete inventory (when all stands in the analysis area are included), since some general inventory parameters are set in this part. Considering cost-efficiency, the inventory is commonly based on a two-stage sampling procedure. Here, this starts with selecting the imported stand register of interest, i.e. the analysis area to be in-field inventoried by plotwise sampling in PPS-sampled stands. | ||
==Stand Data Required== | |||
The following stand register parameters are, more or less, required to enable stratification: | |||
* Area (productive forest land), | |||
* Volume | |||
* Age | |||
* Basal area | |||
* Number of stems | |||
* Tree species proportions | |||
== Classify the imported stand register into different domains== | |||
A domain is here a certain type of forest (e.g., stands with the dominating tree species ''Pinus contorta'') where a certain inventory-scheme should be applied, e.g. securing a certain sample size. The classification is done in the same manner as the forest domain-builder in PlanWise, i.e. the user can select stand-wise properties in the register and define (by using the logical operators) the conditions of a certain domain. If the same inventory-scheme should be applied in all stands in the current analysis area, no additional domains needs to be defined. | A domain is here a certain type of forest (e.g., stands with the dominating tree species ''Pinus contorta'') where a certain inventory-scheme should be applied, e.g. securing a certain sample size. The classification is done in the same manner as the forest domain-builder in PlanWise, i.e. the user can select stand-wise properties in the register and define (by using the logical operators) the conditions of a certain domain. If the same inventory-scheme should be applied in all stands in the current analysis area, no additional domains needs to be defined. | ||
==A stratum is defined usually based on volume and age from the stand register== | |||
The stratification is done in each domain separately. The stands (their productive forest land areas) of a certain domain are related to one of the several user-defined strata. In addition to total area, the number of stands and the area of the largest stand can be viewed in each stratum. The stratum-matrix should first be arranged according to current forest state (by number of classes and class width) and, if desirable, defined by other variables than volume and age. | The stratification is done in each domain separately. The stands (their productive forest land areas) of a certain domain are related to one of the several user-defined strata. In addition to total area, the number of stands and the area of the largest stand can be viewed in each stratum. The stratum-matrix should first be arranged according to current forest state (by number of classes and class width) and, if desirable, defined by other variables than volume and age. | ||
==When a satisfying stratification of the domain(s) has been obtained, the total number of sample stands are decided== | |||
This is called the sample size-definition part. First, a defined number of sample stands will be allocated to each stratum (e.g., proportional to the volume). You could and probably should re-distribute the sample stands over the different strata, with a higher sampling intensity in strata with more valuable forests and where forest management decisions are supposed to be more difficult. The term and parameter "Representative Area", with a value calculated as ''Productive forest land area in current stratum / Sample size (number of sampled stands) in current stratum'', might be found a bit confusing. ''A scale factor with a unit (hectares)? With the same value for all sampled stands in a stratum (despite they probably will have different areas)?'' Don't worry, as long as the sampling of stands is done PPS, and size is the productive area (in hectares), it will all turn out alright. Try to follow this: an estimation of, e.g., the total biomass (in m<sup>3</sup>) in a stratum is derived using a Horvitz-Thompson (HT) estimator with inclusion probabilities (''�?''<sub>''i''</sub>) defined as ''(Area of the i:th sample stand * Number of sample stands in current stratum) / Area of current stratum''. By dividing this estimation by the total area of the stratum an average value (here in m<sup>3</sup>/ha) is derived. Finally, the total volume of biomass in current stratum that is represented by the sample is derived by multiplying the average value-estimate by ''Representative area''. The only time this procedure is not followed is when a single stand show an area equal to or greater than the representative area - such stand will become a sample stand and represent its own area (nothing more, nothing less). | This is called the sample size-definition part. First, a defined number of sample stands will be allocated to each stratum (e.g., proportional to the volume). You could and probably should re-distribute the sample stands over the different strata, with a higher sampling intensity in strata with more valuable forests and where forest management decisions are supposed to be more difficult. The term and parameter "Representative Area", with a value calculated as ''Productive forest land area in current stratum / Sample size (number of sampled stands) in current stratum'', might be found a bit confusing. ''A scale factor with a unit (hectares)? With the same value for all sampled stands in a stratum (despite they probably will have different areas)?'' Don't worry, as long as the sampling of stands is done PPS, and size is the productive area (in hectares), it will all turn out alright. Try to follow this: an estimation of, e.g., the total biomass (in m<sup>3</sup>) in a stratum is derived using a Horvitz-Thompson (HT) estimator with inclusion probabilities (''�?''<sub>''i''</sub>) defined as ''(Area of the i:th sample stand * Number of sample stands in current stratum) / Area of current stratum''. By dividing this estimation by the total area of the stratum an average value (here in m<sup>3</sup>/ha) is derived. Finally, the total volume of biomass in current stratum that is represented by the sample is derived by multiplying the average value-estimate by ''Representative area''. The only time this procedure is not followed is when a single stand show an area equal to or greater than the representative area - such stand will become a sample stand and represent its own area (nothing more, nothing less). | ||
''NB: There should be at least three sample stands in each stratum. Moreover, aviod extreme differences in the representative area of different strata.'' | ''NB: There should be at least three sample stands in each stratum. Moreover, aviod extreme differences in the representative area of different strata.'' | ||
==The presupposed number of plots in a sample stand is set, depending on stand characteristics (chosen by the user)== | |||
This is called the sample plot intensity-definition part. The matrix can be re-arranged as in previous parts, by selecting preferred variables and number of classes and class width. | This is called the sample plot intensity-definition part. The matrix can be re-arranged as in previous parts, by selecting preferred variables and number of classes and class width. | ||
==The sample plot size is set in a similar manner== | |||
Definitions corresponds to the radius, in meters, of the circular plots. Finally, some additional settings are made, necessary in the inventory (e.g. in the sample tree sampling). Read more about the sample tree parameters 1-3 [[Field_inventory_instruction/sv#Provtr.C3.A4dsurvalet|here]]. Unless you're into "living on the edge", it is recommended you leave P1 and P3 as default and later (in field) edit P2 to obtain a certain number of sample trees per plot (on average). | Definitions corresponds to the radius, in meters, of the circular plots. Finally, some additional settings are made, necessary in the inventory (e.g. in the sample tree sampling). Read more about the sample tree parameters 1-3 [[Field_inventory_instruction/sv#Provtr.C3.A4dsurvalet|here]]. Unless you're into "living on the edge", it is recommended you leave P1 and P3 as default and later (in field) edit P2 to obtain a certain number of sample trees per plot (on average). | ||