The Hubbard Brook Ecosystem Study: Forest Biomass and Production

Abstract

A small watershed in the White Mountains of New Hampshire bearing mesophytic, cool—temperate, broadleaf—deciduous forests was studied. Acer saccharum, Betula lutea, and Fagus grandifolia are dominant, but toward higher elevations Picea rubens and Abies balsamea also occur and indicate the transition toward subalpine climate. The stands are young (following cutting in 1909—17) but contain older trees; stand composition is thought reasonably representative of the climax. For application of the Brookhaven system of forest dimension analysis, 93 sample trees of major species were cut and roots excavated. Mean dimensions of sample trees, and the constants for the system of logarithmic regressions relating volume, surface, mass, and growth to diameter at breast height and other independent variables, show decrease in tree sizes and height/diameter ratios toward higher elevations. Stand characteristics, based on application of the regressions to forest samples, show trends of decrease for the elevation belts from low to high: stem basal area 26.3, 23.7, and 22.0 m2/ha, weighted mean tree height 16.9, 16.7, and 10.8 m, weighted mean age 124, 95, and 83 yr, stem wood volume 176, 155, and 103 m3/ha, aboveground biomass (dry matter) 162, 152, and 102 t/ha, estimated volume increment 379, 365, and 223 cm3/m2/yr, aboveground net primary productivity (1956—60) 1127, 1041, and 790 g/m2/yr, and leaf area ratio 6.2, 5.7, and 5.5 m2/m2. Biomass (and, presumably, production) of root systems is 18%—21% of that aboveground. Different estimations suggest that a mean climax biomass for the watershed may be around 350 t/ha, aboveground. Net ecosystem production (i.e., addition to the pool of woody biomass in the community) is estimated as 350 g/m2/yr aboveground and 85 belowground for 1956—60, 238 and 52 g/m2/yr for 1961—65. Analysis of stem wood volume increments reveals an abrupt and striking (18%) decrease in volume growth and productivity from 1956—60 to 1961—65. The net primary productivity of the former period, with a weighted mean for the watershed of 1110 g/m2/yr above and below the ground, is thought more nearly normal for the forest. Both drought and effects of increasing air pollution (notably increasing acidity of rainfall) may be responsible for the recent decrease in productivity.

Comparison of biomass component equations for four species of northern coniferous tree seedlings

“…Predicting tree biomass is important for a) developing indicators of forest productivity [2], b) quantifying patterns of forest succession [17], c) estimating potential carbon sequestering in forest stands [11], and d) modeling forest growth at both tree and stand levels [9].…”

Modelos preditores da fitomassa aérea da Floresta Baixa de Restinga

“…Amostragem e análise de dados -A amostragem foi baseada na distribuição da vegetação em classes de diâmetro (DAP) apresentada por MKR & Embraport (2005), garantindo a coleta de árvores de todos os tamanhos para a construção dos modelos (Overman et al 1994 As árvores selecionadas foram amostradas por método destrutivo (Whittaker et al 1974, Chapman 1976, Golley et al 1978. Destas foram tomadas medidas de circunferência à altura do peito (1,3 m), com fita métrica comum, e de altura total, com trena, após sua derrubada.…”

Scaling net primary production to a MODIS footprint in support of Earth observing system product validation

“…Measured wood production was derived from allometric equations that include standing woody tissues (stem, branch, bark, etc), but not woody roots or woody litter. Whittaker et al (1974) estimated that woody root biomass at the Hubbard Brook Experimental Forest was approximately 10% of total wood biomass, hence this difference in calculation between allometrically-derived and modelled estimates alone could account for a large fraction of the discrepancy.…”