Live Basal Area Research Articles

Invasive pathogen threatens bird–pine mutualism: implications for sustaining a high‐elevation ecosystem

Human-caused disruptions to seed-dispersal mutualisms increase the extinction risk for both plant and animal species. Large-seeded plants can be particularly vulnerable due to highly specialized dispersal systems and no compensatory regeneration mechanisms. Whitebark pine (Pinus albicaulis), a keystone subalpine species, obligately depends upon the Clark's Nutcracker (Nucifraga columbiana) for dispersal of its large, wingless seeds. Clark's Nutcracker, a facultative mutualist with whitebark pine, is sensitive to rates of energy gain, and emigrates from subalpine forests during periods of cone shortages. The invasive fungal pathogen Cronartium ribicola, which causes white pine blister rust, reduces whitebark pine cone production by killing cone-bearing branches and trees. Mortality from blister rust reaches 90% or higher in some whitebark pine forests in the Northern Rocky Mountains, USA, and the rust now occurs nearly rangewide in whitebark pine. Our objectives were to identify the minimum level of cone production necessary to elicit seed dispersal by nutcrackers and to determine how cone production is influenced by forest structure and health. We quantified forest conditions and ecological interactions between nutcrackers and whitebark pine in three Rocky Mountain ecosystems that differ in levels of rust infection and mortality. Both the frequency of nutcracker occurrence and probability of seed dispersal were strongly related to annual whitebark pine cone production, which had a positive linear association with live whitebark pine basal area, and negative linear association with whitebark pine tree mortality and rust infection. From our data, we estimated that a threshold level of approximately 1000 cones/ha is needed for a high likelihood of seed dispersal by nutcrackers (probability > or = 0.7), and that this level of cone production can be met by forests with live whitebark pine basal area > 5.0 m2/ha. The risk of mutualism disruption is greatest in northern most Montana (USA), where three-year mean cone production and live basal area fell below predicted threshold levels. There, nutcracker occurrence, seed dispersal, and whitebark pine regeneration were the lowest of the three ecosystems. Managers can use these threshold values to differentiate between restoration sites requiring planting of rust-resistant seedlings and sites where nutcracker seed dispersal can be expected.

Two decades of change in vegetation in Adirondack spruce-fir, northern hardwood and pine-dominated forests1

In 2004 we remeasured trees in 42 permanent vegetation plots that had been established in Adirondack spruce-fir, northern hardwood, and pine-dominated stands in 1984. Over the 20-yr interval, live basal area (BA) in red spruce and/or balsam fir-dominated plots decreased by 15%. Blowdown was a major cause of balsam fir, but not red spruce mortality in two plots. Excluding the two blowdown plots, balsam fir live BA increased by 17%, while red spruce live BA decreased by 42% (P < 0.05). There was no significant change in the overall live BA of northern hardwood plots. However, excluding beech, the pooled northern hardwoods showed a significant decrease (P ≤ 0.05) in live BA over the 20-yr interval. In contrast to the spruce-fir and northern hardwood plots, the live BA of pine-dominated plots increased by 19% over the 20-yr interval (P ≤ 0.01). Changes in sapling densities in the spruce/fir plots were not significant, though fir in the 2–9.9 cm dbh class reached densities of > 3000 stems ha−1 in four plots where they filled large gaps. There was a trend toward increased red spruce sapling density (P ≤ 0.10) in the upper northern hardwood zone (600–950 m). Sugar maple sapling density and BA decreased significantly (P ≤ 0.05) in the northern hardwood plots during the twenty-year interval.

Quantitative assessment of stand condition and its relationship to physiological stress in stands of Eucalyptus camaldulensis (Myrtaceae)

River regulation has led to a decline in the condition of Australia’s dominant riverine tree species, Eucalyptus camaldulensis Dehnh., in the Murray–Darling Basin. A quantitative method of assessing the condition of these important riparian forests is required for effective monitoring and management. A range of stand structural, morphological and physiological variables was measured in stands of contrasting condition along the Murray River in south-eastern Australia. Percentage live basal area, plant area index and crown vigour were found to be reliable, objective indicators of stand condition. Little difference was detected in the physiological performance of trees in terms of water potential and chlorophyll fluorescence among stands of good and poor condition.

Red spruce ecosystem level changes following 14 years of chronic N fertilization

In the early 1980s, nitrogen (N) deposition was first postulated as a cause of N saturation and spruce mortality across the northeastern US. In 1988, a series of high elevation spruce-fir forest N addition plots were established on Mt. Ascutney (southeastern) Vermont to test this hypothesis. The paired plots each received, in addition to ambient N deposition, 15.7 kg N ha −1 year −1 (low N addition), 31.4 kg N ha −1 year −1 (high N addition) or no N addition (control) from 1988 to 2002. Over the years, potential and annual in situ forest floor net N mineralization and net nitrification, foliar and forest floor elemental concentrations, and basal area growth by species were measured on each plot. Live basal area decreased by 18% on the low N addition plots, and by 40% on the high N addition plots between 1988 and 2002, while the control plots had a 9% increase in basal area over the same time period. Initially, none of the plots had measurable rates of in situ nitrification, but by 2002, 21% of the mineralized N was being annually nitrified on the high N addition plots, compared to no net nitrification on the control plots. We also observed a significant increase in forest floor N concentration on the high N plots from 1988 to 2000. Reductions in live basal area, and increased net nitrification suggest that we induced late stage N saturation on the high N addition plots. The low N addition plots exhibited symptoms of mid-stage N saturation, with a smaller reduction in live basal area and net N mineralization, and a smaller increase in net nitrification compared to the high N addition plot values. Other correlations between forest floor and vegetation composition and function, and N saturation will be discussed in the paper.

Arboreal vegetation, coarse woody debris, and disturbance history of mature and old-growth stands in a coniferous forested wetland1

Abstract Forrester, J. A. (SUNY, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210-2778), T. E. Yorks (Environmental Studies Program, Cazenovia College, 22 Sullivan Street, Cazenovia, NY 13035) and D. J. Leopold (SUNY, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210-2778). Arboreal vegetation, coarse woody debris, and disturbance history of mature and old-growth stands in a coniferous forested wetland. J. Torrey Bot. Soc. 132: 252–261. 2005.—We quantified the forest age and tree size structure of an old-growth and mature stand in a coniferous forested wetland in central New York, USA. We also determined the volume and decay class distribution of standing and downed coarse woody debris. The old-growth stand contains eastern white pine (Pinus strobus L.) > 400 years old and other species > 200 years old. Live tree basal area in the old-growth area (36 m2·ha−1) was dominated by approximately equal amounts of balsam fir (Abies balsamea (L.)...

Red Spruce Dynamics in an Old Southern Appalachian Forest

BUSING, R.T. (U.S. Geological Survey, 200 SW 35h St., Corvallis, OR 97333). Red spruce dynamics in an old southern Appalachian forest. J. Torrey Bot. Soc. 131: 337-342. 2004.-By the late 1980s the composition and structure of forest stands in the southern Appalachian spruce-fir zone were altered by insect infestations to Fraser fir. The response of red spruce, the sole remaining coniferous forest dominant, to this disturbance was followed over twenty years (1983-2003) in an old spruce-fir forest at Mt. Collins, Great Smoky Mountains National Park. Although diameter growth of canopy red spruce (>30 cm dbh) at six plot sites was considerable (mean 10-yr increment 2.1 cm; 1993-2003), red spruce mortality increased sharply (mean 4% yr-'; 1993-2003). Wind-related mortality of canopy red spruce was substantial after the loss of Fraser fir from the canopy circa 1985 (>70% of the dead spruce had broken or uprooted boles; 1983-2003). Wind damage to red spruce was observed at most plot sites, but it was most pronounced on exposed topographic positions, where canopy gap expansion was extensive. The elevated mortality of red spruce at Mt. Collins was not associated with reduced diameter growth. Altered canopy structure has left large red spruce vulnerable to high winds. With the loss of canopy fir and the subsequent increase in mortality of canopy spruce, total live basal area has declined to about half of its pre-disturbance level.

Relationships between Arceuthobium americanum and the structure of Pinus contorta var. murrayana stands in central Oregon

We examined the importance of the dwarf mistletoe Arceuthobiumamericanum in determining the size-class structure ofPinuscontorta var. murrayana forests in the centralOregon pumice zone. We considered the interrelationships among A.americanum abundance, P. contorta populationstructure, soil type, site topography, the density of competing tree and shrubspecies, and understory woody litter. We found that A.americanum was associated with reduced live basal area(P < 0.001) and increased bole diameter variability(P < 0.001) of P. contorta, andalso with an increase in the density of saplings and seedlings(P < 0.001) at the expense of dominant andtall-intermediate trees. Saplings and seedlings were over 15 times as dense inheavily infested stands as in uninfested stands. Reflecting this shift towardsmaller size classes, each unit increase in stand-level dwarf mistletoe rating(DMR) reduced live basal area by 1.32 m2/ha and reducedthe density of dominant-sized trees by 45 trees/ha. The significant reductionsin live basal area and the density of dominant trees contrast with otherstudiesconducted in P. contorta stands containing A.americanum. However, DMR uniquely explained less than 25% of thetotal site-level variance in all size class variables except sapling density(36%), and varied in importance relative to interspecific competition betweenPinus ponderosa and P. contorta, theeffects of abiotic factors, and intercohort dynamics in determining thestructureof P. contorta stands across the study site. DMR uniquelyexplained less of the variance in live basal area (12%) than abiotic factors(28%) and P. ponderosa density (16%), and only 15% ofvariability in the density of the dominant P. contortasizeclass. Furthermore, the relative effects of DMR on specific P.contorta size classes varied across patch- and stand-level spatialscales. We conclude that the relative importance of the effects of A.americanum on specific P. contorta size classesdepends on spatial scale, and should be interpreted in relation to patchdynamics, site-level topoedaphic variability, and interspecific competitionamong the dominant tree species present.

Stand dynamics over 18 years in a southern mixed hardwood forest, Texas, USA

Summary 1 Using 18 years of permanent‐plot data from a 4‐ha stand, we investigated whether stand dynamics is predictable, i.e. driven by competition (inferred from species shade tolerances), or unpredictable (driven by frequent exogenous disturbance or other factors). We also considered whether small disturbance might accelerate or retard succession. The study involved dynamics of stems ≥ 4.5 cm diameter at breast height (d.b.h.) for 10 important species in a southern mixed hardwood forest 80 years after selective removal of Pinus taeda. 2 Shade‐tolerant species (Ilex opaca, Fagus grandifolia, Magnolia grandiflora, Acer rubrum, Nyssa sylvatica) increased in small d.b.h. classes, whereas intermediate (Quercus alba) and shade‐intolerant species (Q. nigra, Q. hemisphaerica, Liquidambar styraciflua, Pinus taeda) did not. 3 Per‐capita ingrowth was higher for shade‐tolerant species (0.016–0.024) than for intermediate and shade‐intolerant species (0–0.006), whereas mortality was lower ((0.006–0.015 vs. 0.019–0.035). 4 Over 18 years, ingrowth exceeded mortality loss slightly, resulting in an increase in number of stems of about 1%, from 995 to 1029 stems ha−1; average live basal area (BA; 35.9 m2 ha−1) varied by less than 2% over eight surveys spanning 18 years. Basal area increased substantially for three species (Ilex opaca, Pinus taeda, Acer rubrum), and declined strongly for three others (Quercus nigra, Q. hemisphaerica and Fagus grandifolia). 5 The stand d.b.h. distribution had a rotated sigmoid form which became flatter over time. Species d.b.h. distributions were mostly bell‐shaped for intolerant species, and irregular‐to‐monotonic declining for shade‐tolerant species. Over time, bell‐shaped distributions moved to the right and irregular distributions remained irregular. 6 A hurricane in 1986 caused loss of 4.5% of standing BA. Compositional change was most rapid during the hurricane interval and ingrowth was highest in the two intervals following the hurricane. Effects on species trends in density, basal area, mortality or recruitment were minor. 7 Temporal trends in species abundances mostly supported the hypothesis of predictable successional change related to competition for light. However, d.b.h. distributions of shade‐tolerant species and rapid declines in BA of Quercus nigra and Fagus indicated that other processes are also important and will limit predictability of change.

Use of Coarse Woody Debris by the Plant Community of a Hawaiian Montane Cloud Forest1

ABSTRACTMany species of woody plants in Hawaiian montane forests germinate on nurse logs or epiphytically, often developing aerial roots. This study investigated the role of fallen logs, wood fragments, and other forms of coarse woody debris (CWD; 35 cm diam.) in providing habitat for woody species in a forest with waterlogged soils. Oxidation‐reduction potentials (Eh) of root mats and nurse logs (−70.1 to 278.6 mV) were higher than the underlying soil horizons (−203.6 to −128.1 mV). CWD volume varied between 135.9 and 427.9 m3/ha. Live basal area varied between 18.4 and 29.7 m2/ha and increased with total CWD volume. Seedling and sapling abundances on nurse logs were correlated with moss coverage and decomposition class. Moss coverage was the only significant predictor of seedling density on nurse logs, whereas moss coverage and log volume were important for predicting sapling density. The proportion of woody plants established on logs was higher than in a younger Hawaiian montane forest site with well‐drained soils.

Use of Coarse Woody Debris by the Plant Community of a Hawaiian Montane Cloud Forest1

Many species of woody plants in Hawaiian montane forests germinate on nurse logs or epiphytically, often developing aerial roots. This study investigated the role of fallen logs, wood fragments, and other forms of coarse woody debris (CWD; 35 cm diam.) in providing habitat for woody species in a forest with waterlogged soils. Oxidation-reduction potentials (Eh) of root mats and nurse logs (−70.1 to 278.6 mV) were higher than the underlying soil horizons (−203.6 to −128.1 mV). CWD volume varied between 135.9 and 427.9 m3/ha. Live basal area varied between 18.4 and 29.7 m2/ha and increased with total CWD volume. Seedling and sapling abundances on nurse logs were correlated with moss coverage and decomposition class. Moss coverage was the only significant predictor of seedling density on nurse logs, whereas moss coverage and log volume were important for predicting sapling density. The proportion of woody plants established on logs was higher than in a younger Hawaiian montane forest site with well-drained soils.

Spring Defoliation Effects on Bluebunch Wheatgrass: II. Basal Area

Spring livestock grazing has been suggested as a tool to improve winter forage quality of bluebunch wheatgrass (Agropyron spicatum [Pursh] Scribn. &Smith). Impacts on plant vigor and survival are important concerns associated with spring grazing. We report basal area change and mortality responses of bluebunch wheatgrass to 3 spring, 1 winter, and 3 spring + winter defoliation treatments. The study was conducted in l993 and 1994 at 2 sites in the Blue Mountains of northeastern Oregon. Basal area of individual plants was measured shortly after application of the spring treatments and again approximately 1 year after treatment. Clipping the entire basal area of bluebunch wheatgrass plants to a 7.6-cm stubble height during the mid-boot phenological stage and during the inflorescence emergence stage produced 7.0 and 7.8% declines in live basal area, respectively. Unclipped control plants and plants having only one-half their basal area clipped to a 7.6-cm stubble height during the mid-boot stage exhibited 5.2 and 18.6% increases in live basal area, respectively. Combining the mid-boot/half-plant treatment with an early winter clipping to a 2.5-cm stubble height reduced the positive live basal area response to 6.0%. No additional declines in live basal area relative to the spring-only treatments were detected for combinations of the early winter treatment with the mid-boot/whole plant treatment and the inflorescence emergence treatment. Experiment-wide plant mortality was only 0.2%. If managed for a moderate level of defoliation where a portion of the basal and of each bunchgrass plant is left undefoliated, livestock grazing during the boot stage should have little negative impact on the vigor and survival of bluebunch wheatgrass under environmental conditions similar to northeastern Oregon.

Canonical correlation analysis of coniferous forest spectral and biotic relations

Abstract Canonical correlation analysis was used to examine the relations between the six reflective Thematic Mapper bands and six forest structural variables for 70 lodgepole pine forest stands in Yellowstone National Park, U.S.A. Two significant canonical variate pairs were extracted, accounting for 96·4 per cent of the total information in the overall canonical correlation analysis. Results of the canonical redundancy analysis indicate that 78 per cent of the overall unstandardized variance in spectral data is explained by the first two spectral canonical variates, while the first and second biotic canonical variates explain 59 per cent and 5·9 per cent of the raw variance in the spectral data. The first two biotic canonical variates collectively explain 59 per cent of the raw variance in the biotic data, and the first and second spectral canonical variates explain 41 per cent and 6 per cent of the raw variance in the biotic data, respectively. Height, live basal area, leaf area index (LAI), and size d...

Spatial patterns in forest composition and standing dead red spruce in montane forests of the Adirondacks and northern Appalachians

The decline of red spruce (Picea rubens Sarg.) in montane forests of the northeastern United States has been previously reported. The objective of this study was to assess spatial patterns, if any, in standing dead red spruce stems in the Adirondacks of New York and northern Appalachians of Vermont, New Hampshire, and Maine. A stratified random sample of 19 mountains along a west to east transect in the Adirondacks and the northern Appalachians showed that the live basal area of all species was highest in the White Mountains (34.6 m(2) ha(-1)) and lowest in the Adirondack Mountains (23.7 m(2) ha(-1)) in the Green Mountains was significantly lower than in any other region. Intact standing dead red spruce in the Adirondack and Green Mountains (30%) was significantly higher than that in the three eastern clusters (14%). The amount of intact standing dead red spruce trees increased with elevation in only the western part of the region. With the exception of the Adirondacks, there was a greater average percent dead red spruce on the west side than on the east side of each mountain. The sum of standing dead for other tree species (average 13%) showed no statistically significant patterns with region, elevation or aspect, and was significantly lower than the amount of total dead red spruce (average 42%). The standing dead red spruce patterns we observed cannot be associated with any specific causal factors at this time.

Maritime Forests on Bull Island, Cape Romain, South Carolina

HELM, A. C., N. S. NIcHoLAs, S. M. ZEDAKERO AND S. T. YoUNG (Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061). Maritime forests on Bull Island, Cape Romain, South Carolina. Bull. Torrey Bot. Club 118: 170-175. 1991.Bull Island is a barrier island within Cape Romain National Wildlife Refuge in Charleston county, South Carolina. Prior to Hurricane Hugo in September of 1989, the island's maritime forest contained healthy stands of old-growth, 70-160 year old loblolly pine (Pinus taeda L.) that averaged 43.8 m2/ha live pine basal area. The Bull Island stands may have been the second oldest documented loblolly pine forest in the United States. Other predominant overstory tree species on Bull Island included live and laurel oak (Quercus virginiana Miller and Quercus laurifolia Michaux) with a combined live basal area of 31.2 m2/ha, cabbage palm (Sabalpalmetto Lodd. ex Schultes) and Chinese tallow tree (Sapium sebiferum L. Roxb.), with live basal areas of 7.3 and 6.4 m2/ha, respectively.

Effects of irrigation and artificial drought on the growth and health ofPinus radiatanear Canberra, A.C.T

Summary A series of plots comparing 1) irrigation at 12.5 mm per week 2) normal rainfall and 3) artificial drought was established in a 9-year old stand of Pinus radiata D. Don. near Canberra, A.C.T. The degree of drought-induced dieback was inversely proportional to water supply. Mortality was at first greatest on the draughted plots but later these plots became more resistant to mortality caused by natural drought than plots which received normal rainfall. After 12 years of treatment total basal area production was 64, 46, and 33 m2 ha-1 on the irrigated, normal and draughted plots respectively. Self-thinning maintained live basal area at about 35 m2 ha′ on the normal plots and 25 m2 ha-1 on the draughted plots. Although there was some mortality on the irrigated plots there was no indication of an upper limit for carrying capacity for live basal area. The cessation of irrigation was followed by substantial deaths which reduced live basal area to a level comparable with the normal plots. Examination of s...

Effects of the December 1983 tornado on forest vegetation of the big thicket, southeast Texas, U.S.A.

On December 10, 1983, a large tornado touched down in southwestern Tyler County in southeastern Texas, U.S.A., causing major damage to two areas of forest in the Big Thicket National Preserve (BTNP). The sizes of the disturbed areas were 31.1 ha in the Hickory Creek Unit and 10.4 ha in the Turkey Creek Unit of the BTNP. Canopy cover at Hickory Creek was reduced by 83%, live basal area declined by 66.7%, and live density declined by 33.6%. At Turkey Creek, canopy cover was reduced by 46%, live basal area declined by 37.8% and live density declined by 14.4%. Large percentages of surviving trees at both sites were badly damaged: 31.3% at Hickory Creek and 48.9% at Turkey Creek. Tornado mortality was strongly concentrated in the large size classes and, for this reason, the primary short-term effect on forest composition at both sites was to select strongly against the previously dominant canopy species.

A comparison of vegetative cover and tree community structure in three forested Adirondack watersheds

The Integrated Lake–Watershed Acidification Study (ILWAS) was conducted using three forested watersheds (Panther, Sagamore, and Woods) in the central Adirondack Park of New York State. By comparing the biogeochemical behavior of these watersheds, the ILWAS investigators hoped to elucidate the major ecosystem parameters controlling the fate of strong acids introduced from the atmosphere to lake–watershed systems. The ILWAS vegetation research program was designed to compare the quantitative patterns of forest structure in these midelevation watersheds. Results showed that the ILWAS catchments contain closely related variants of the northern hardwood – spruce – fir complex of the Adirondack region. The dominant tree species in these watersheds are beech (Fagusgrandifolia Ehrh.), red spruce (Picearubens Sarg.), sugar maple (Acersaccharum Marsh.), red maple (Acerrubrum L.), and yellow birch (Betulaalleghaniensis Britt.). On an areal basis, the watersheds contain 57–88% hardwood cover type and 5–29% spruce–fir cover type. Mean live basal area values range from 22 to 30 m2 ha−1 between catchments, while standing dead basal area values range from 4 to 8 m2 ha−1. Mean live stem densities range from 1400 to 1700 stems ha−1. Mean aboveground biomass projections for the tree stratum in the three watersheds range from 143 to 199 Mt ha−1, while estimated aboveground annual biomass increments range from 4.1 to 5.3% of standing biomass.

The Response ofPinus radiatato Initial Spacing

SYNOPSIS This paper deals with the statistical analysis of growth data, obtained from the C.C.T. spacing trial at Tokai in Pinus radiata. The Chapman-Richards growth model was used to fit equations with live basal area as predicted variable. The estimated parameters were subsequently regressed on nominal stems per hectare. A linear regression with log age as predictor variable was used to obtain estimates for mean diameter at different ages. The coefficients of this equation were also regressed on nominal stand stems per hectare. A regression equation with stems per hectare and mean height as independent variables was used to estimate top height, which was subsequently regressed on age. A regression analysis with nominal stems per hectare as independent and coefficients of the top height-age regression as dependent variables revealed a maximum top height in stands of medium stand density. The growth curves for u.b. volume were derived from the corresponding basal area growth curves. An analysis of the obs...

Plot size and number of plots needed to assess spruce budworm impact

This study investigated size and number of plots needed to precisely estimate tree mortality, mean dead basal area, mean dead volume, mean live basal area, and mean live volume in stands infested with the spruce budworm, Choristoneurafumiferana (Clemens).Depending on the parameter, precision of four different plot sizes (0.02, 0.04, 0.08, 0.40 ha) was examined. For most parameters the 0.04-ha plot appears to be approximately as precise as the larger plot sizes. Variables which affect the precision of the plot sizes are percent mortality, patchy distribution of the character of interest, and the variability associated with the population of interest. The precision of two, three, four, and five plots per stand was investigated. The coefficient of variation of the mean is reduced the greatest between two and three plots; subsequent reductions beyond three plots are not great. The number of plots needed based on sampling theory varied according to the parameter and the variability associated with the parameter. It was determined that the time involved in evaluating three 0.04-ha plots was approximately the same as needed to evaluate two 0.08-ha plots.

The Effect of Initial Spacing on Some Growth Parameters of Eucalyptus grandis

ABSTRACT The relationship between the growth rate of Eucalyptus grandis and initial spacing was studied in a replicated spacing trial correlated Curve Trends (CCT) on the coastal plain of Zululand. The parameters of the Richard~ growth equation, applied to live basal area, were regressed on nominal stand density, An asymptotic regression was fitted to the observed mean diameters, the estimated parameters of which were subsequently regressed on Nnom An analysis of height growth revealed that mean height as well as top height are related to stems per hectare. Measurements of crown width and crown length served to evaluate the effect of stand density on crown parameters.