Diameter growth models using Minnesota forest inventory and analysis data

ABSTRACT. The Forest Inventory and Analysis (FIA) program of the USDA Forest Service North Central Research Station (NCRS) has begun replacing the 12-to 13-yr periodic inventory periods for the states in the North Central region with annual inventories featuring measurement of approximately 20% of all plats in each of the 11 states each year. State reports upon summaries of the forest resources will be produc each 5 yr. As a mode of updating information on plats not visited in the general year, NCRS is developing nonlinear, individual-tree, distance-independent annual diameter expansion models for species groups. The moulds formulated as the product of an average diameter development component and a modifier constituting were calibrated on Minnesota FIA data from stands that were generally undisturbed, of mixed ages and of mixed species. The hanging variable is annual diameter expansion The independent variables include diadem ratio, crown class, stand basal area, stand basal area larger than the make submissive tree, physiographic class, and latitude and longitude of plat locations. The model predictions at the one and the other the individual-tree level and piece of ground level have negligible bias, and the archetypes may be easily recalibrated to include fresh data sets obtained from the annual inventories. For. Sci. 47(30):301-310

Key Words: Average diameter increase model, gamma probability distribution function, individual-tree, distance-independent.

IN reply TO THE 1998 FARM BuL formally known as the Agricultural Research Extension and Education Reform Act, the North Central Research Station (NCRS) of the USDA Forest Service has discloseed an annual inventory system featuring a hexagonal grid of Forest Inventory and Analysis (FIA) plats to be measured in 5 yr inventory periods with 20% of the piece of grounds to be measured each year (Brand et al. 2000) State reports summarizing the 5 yr inventory of forest resources will be published. Because inventories are leadershiped over 5 yr cycles, data from 80% of the piece of grounds will be 1 to 4 yr advanced in years and summaries based on moving averages lag common conditions. Individual tree diameter development models provide a means to eliminate this lag through estimating current conditions for FIA plats not measured in the generally received year.

Historically, growth and yield patterns have been generally classified into three categories (Davis and Johnson 1987): (1) whole stand originals that predict growth for the entire stand based upon a stand characteristic such as basal area, age, or site index (eg Buckman 1962 clatter 1963, Moser and Hall 1969 Sullivan and confused noise 1972, McRoberts 2000); (2) diameter class moulds that predict stand growth rates by dint of diameter classes among which the number of tree for unit area are distributed (eg Bailey and ravine 1973, Adams and Ek 1974 Ek 1974 Solomon et al. 1995); and (3) individual tree patterns that predict growth for individual tree generally based upon a combination of tree and stand characteristics. The individual tree moulds that predict diameter growth may be further divided into distance-dependent moulds that require that the data include mapped tree locations thus that competition information may be incorporated (eg Daniels and Burkhart 1975 Daniels and Burkhart 1988) and distanceindependent prototypes that do not require mapped tree locations, on the contrary use competition factors such as stand basal area or stand density (eg Stage 1973 Belcher et al. 1982 Murphy and Sternitzke 1979 Shifley and Fairweather 1983 Shifley 1987 Amateis et al. 1989 Hasenauer et al. 1998 Murphy and Graney 1998 Cao 2000) The growing models developed by Stage (1973) Murphy and Sternitzke (1979) Belcher et al. (1982) Shifley and Fairweather (1983) and Shifley (1987) have been applied to FIA data for predicting increase Of these models, FIA data was used to calibrate the patterns developed by: (1) Murphy and Sternitzke (1979) for burgout pine (Pines taeda L.) upon 145 FIA plots in the West Gulf; (2) Shifley and Fairweather (1983) for all species upon 831 FIA plots in western Oregon; and (3) Shifley (1987) for all species assemblages on more than 2,700 FIA plats in the central states. The latter sum of two units sets of models were based upon the STEMS (Belcher et al. 1982) mould formulation. The diameter growth originals developed in this article are individual-tree distance-independent protoplasts that are calibrated on FIA data.

The FIA program of NCR has used stipes (Belcher et al. 1982) to predict individual tree diameter expansion and survival. The current methodology for calibrating protoplasts departs from that used for main stocks in order to improve the efficacy of the moulds in several areas:

>The primary intended application of the designs reported in this study is in an inventory connection Therefore, the calibration data have been restricted to inventory data, whereas the source of a great quantity [i]or[/i] amount of of the data used to calibrate the stipes models was long-term research piece of grounds

> The mathematical form of the rife models avoids the potential extension construct common to STEMS and other growing models, because potential growth cannot be observ and historical conducts for estimating it are composite and time-consuming.