title: The Wood and Bark Biomass and Production of Populus tremuloides, Abies lasiocarpa and Picea engelmannii in Northern Utah
Creators: name: Zimmerman, George L.
Publisher: name: Utah State University
Year: 1979

description: Thirty-two engelmann spruce (Picea engelmannii) ranging in d.b.h. from 9.4 to 84.6 em, twenty subalpine fir (Abies lasiocarpa) with d.b.h.'s from 8.1 to 58.8 cm, and twenty aspen (Populus tremuloides) ranging in d.b.h. from 4.5 to 48.2 em. were destructively sampled in Northern Utah to construct wood and bark biomass and production prediction equations for above and below ground parts. These prediction equations were then applied to stand table data from 20 x 25 meter plots representing a sere that changes from subalpine meadow to aspen to fir to a 'climax' stand of spruce. The biomass production data along the successional stages were then used to test some of Odum's hypotheses regarding ecosystem development (Science 1969).
In all biomass and production predictive equations diameter at breast height (1.38 meters) and its transformations was found to be the single best independent variable. Spruce bole bark biomass was best correlated linearly with d.b.h. Spruce bole wood, branch wood and branch bark were best predicted with a d.b.h.2 relationship. All fir above ground biomass components as well as all aspen above ground components except aspen branch wood were best correlated with d.b.h.2 Aspen branch wood biomass was best predicted by a d.b.h.3 equation. Seedling sized fir, spruce, and aspen (trees less than 1.38 meters in height) had their total above ground wood and bark biomass best predicted using basal diameter3 as the independent variable.
Seven spruce and fir stump and root systems, from trees ranginq from 2.5 to 66.0 cm in d.b.h., were excavated by hand. All roots down to one centimeter in diameter were cut weighed and oven-dried. Biomass data from the fir and spruce stumps and roots were combined because of their similarity. The resulting combined biomass data was described accurately by using d.b.h.4 as the independent variable. Aspen root biomass was obtained through the use of three randomly located excavated cubic meter pits in each of four different clones. The aspen pit root biomass was best described by employing a sixth degree polynomial using the diameter (em) of the four nearest trees to pit center divided by their average distance (meters) to pit center.
Two production methods were used : l) mean annual increment (MAl) and 2) periodic annual increment (PAl). No production estimates for roots were made. Spruce bole wood and bark MAl's were best predicted by d.b.h. and log-log d.b.h. equations respectively. Spruce branch wood and branch bark MAl's were both best described by d.b.h. (li near) relationships. All fir MAl branch and bole components used d.b.h.2 in their predictive equations. All aspen MAl equations used sixth degree polynomials with d.b.h. as the independent variable. Polynomials were employed when downward or leveling trends could not be adequately represented using standard statistical techniques.
Spruce and aspen PAI equations were constructed using polynomials. Fir PAl, because of the data, could be best predicted using standard regression techniques. Fir bole wood and bark PAl equations were 'linear and thus best described by d.b. h. untransformed. Fir branch and wood PAl showed some leveling which was gradual enough to best be fitted by a d.b.h.3 equation.
Using the biomass and production predictive equations and stand tables from plots representing a succession, plot biomass and productions were generated. The plot biomasses and productions were plotted against estimated age (time from the initial meadow invasion by aspen). Above and below ground total wood and bark plot biomass was found to increase with time through all stages being low in early aspen dominated stages (1.5 x 105 kg/ha @ 7.5 years) to high in late spruce dominated stands (5.25 x 105 kg/ha @ 258 years). This finding supports Odum's hypothesis that biomass is low in early stages and higher in later stages of ecosystem development.
Both estimates (MAl and PAI) of total above-ground plot production show that production is high in early aspen stages (PAl is 4.7 x 103 kg/ha/yr @ 65 years), low in mid-successional fir dominated stands (PAl is 3.0 x 103 kg/ha/yr@ 130 years), and high again in the late spruce stages (4.6 x 103 kg/ha/yr @ 258 years). This tends to contradict Odum's hypothesis that production tends to keep decreasing after the initial stages of succession. While these tests of Odum's hypotheses are only on the basis of tree wood and bark, these values will probably be found to be the largest single biomass and possibly production community contributors.