Plot Basal Area Research Articles

POTENTIAL IMPACTS OF THE INVASIVE EXOTIC SHRUB RHAMNUS FRANGULA L. (GLOSSY BUCKTHORN) ON FORESTS OF SOUTHERN NEW HAMPSHIRE

This paper investigated the potential for the exotic shrub Rhamnus frangula L. (glossy buckthorn) to alter native plant community composition in southeastern New Hampshire. Stratified random sampling was performed with 2 m × 2 m plots randomly located in 5 m intervals along three 50 m transects in four even-aged Pinus-mixed hardwood forests, three of which were managed stands. The associations between R. frangula and the measured species abundances and environmental variables were investigated using linear, least-squares multiple regression and Non-metric Multidimensional Scaling Ordination. Plot basal area of R. frangula was inversely related to woody seedling density (p < 0.001), herb cover (p < 0.05), and species richness (p < 0.01). The relative contribution of R. frangula to explaining variance in seedling density was greater than canopy openness, soil pH, soil clay, or soil sand. Abundance of R. frangula was a statistically significant predictor (p < 0.05) of individual herb species abundances for all study sites. This evidence supports the hypothesis that R. frangula causes a decline in seedling density and alters native ground level plant species abundances. Furthermore, the patterns agree with the suppression of ground level plant species abundances by R. frangula found in removal experiments.

Competition among canopy trees in indigenous forests: An analysis of the ‘additive basal area’ phenomenon

Abstract The basal area of indigenous forest plots containing large canopy individuals appears to be larger than plots without them. One explanation for this effect is the avoidance of competition for light due to these large individuals emerging above the rest of the canopy and thus casting relatively little shade. In this way the basal area of these emergent individuals becomes ‘additive’ to that of the ‘rest’ of the individuals on a plot. The ‘additive basal area’ phenomenon was tested for in the Knysna Forest, South Africa by regressing the basal area of focal species versus the total basal area of 0.04‐ha plots, as well as against the basal area of the ‘rest’. Regression analysis suggested weak competition and a stronger additive effect. However, no emergent individuals occurred in the study taxa. A strong impact of the size of the largest individual on total plot basal area was found. It is suggested that the reason for this is that large individuals overcome spatial and packing limitations in forests.

Stocks and flows of coarse woody debris across a tropical rain forest nutrient and topography gradient

Large pieces of standing or fallen dead wood, known as coarse woody debris (CWD), play important roles in temperate forest carbon and nutrient cycles, and affect the abundance and distribution of many classes of organisms. CWD biomass and inputs are poorly documented in tropical rain forests (TRF), and the causes for their variation at landscape-scales in this biome have not been studied. We quantified standing and fallen CWD stocks and inputs in upland (non-swamp) old-growth TRF at the La Selva Biological Station, Costa Rica. We used a network of 18 0.5 ha plots sited in three edaphic conditions to analyze soil nutrient effects on CWD stocks and inputs controlling for topography, and to examine topographic effects controlling for soil nutrients. The edaphic conditions were flat inceptisols, flat ultisols, and steep ultisols. Chemical analyses confirmed the existence of an almost three-fold gradient in total P and K in the upper 1 m of soil. We also annually censused all live woody stems ≥10 cm diameter above buttresses in each plot in September/October from 1997 to 2000 to obtain data on stand structure and dynamics. Fallen CWD stocks averaged 46.3 Mg ha −1 (22.3 Mg C ha −1), while standing CWD averaged 6.5 Mg ha −1 (3.1 Mg C ha −1). There were no significant differences in volume or mass of standing or fallen CWD among edaphic conditions. Annual inputs of CWD averaged 4.9 Mg ha −1 (2.4 Mg C ha −1). Turnover time of fallen CWD was ca. 9 year. Neither stocks nor inputs were correlated with stand structure (number of trees per plot, plot basal area, or plot estimated above-ground biomass). Potential differences in CWD stocks and inputs among sites with different edaphic conditions may have been obscured by a 10-fold variation in tree mortality among plots and a two-fold variation in mean CWD input among years. Analysis of sample variance showed that stocks of CWD were adequately sampled with the 18 0.5 ha plot design, but that inputs were measured with low precision. At La Selva fallen and standing CWD stocks together equaled ca. 33% of estimated above-ground live woody biomass. Tropical rain forest CWD and its associated carbon are intermediate in pool size and turnover rate between fine litter and live trees. Our results show that scaling up TRF CWD estimates to larger spatial scales may be more constrained by the quality of data obtained over single landscapes than by variation due to zonal soil nutrient and topographic conditions. Both the magnitude and vagility of TRF CWD pools are likely to change with global climate change, but the overall direction of change is uncertain.

The Ratio of Live Crown Length to Sapwood Area as a Measure of Crown Sparseness

Abstract Leaf area density is a biologically appealing index of forest tree health because it can provide an assessment of foliage loss or retention; however, it is difficult to measure directly. In contrast, the ratio of crown length to sapwood area (CL:SA) is quite amenable to objective field measurement, and could be interpreted as an index of crown sparseness. CL:SA was computed for Douglas-fir trees from 70 plots covering a range in average size, stand density, site quality, and crown condition in the Oregon Coast Range. When expressed as cm:cm2, the index ranged from 2 to 100 for individual trees and from 2 to 11 for plot averages based on the 200 largest trees per ha. In general, individual trees with a high CL:SA had a lower relative height within the stand. The index also increased with increasing severity of needle loss on sites where Swiss needle cast (SNC) is causing premature loss of foliage. After correcting for stand density and stand age, plot basal area growth increased significantly with a decrease in plot average CL:SA across a gradient in Swiss needle cast severity. CL:SA has strong potential for discriminating effectively among stands with varying degrees of foliage loss and growth reduction due to other disturbances as well, such as air pollution and defoliating insects. FOR. SCI. 48(1):93–100.

Distance-dependent and distance-independent models of Douglas-fir and western hemlock basal area growth following silvicultural treatment

Distance-independent and distance-dependent individual-tree basal area growth equations for Douglas-fir and western hemlock growth following thinning and fertilization treatments were developed using regression analysis. Distance-independent models included only non-spatial competition and thinning indices, while distance-dependent models included both spatial and non-spatial indices. The distance-independent models with the highest adjusted multiple coefficient of determination (adjusted R 2) for both species included diameter at breast height, crown class, percent basal area removed in thinning, plot basal area greater than the subject tree and stand age as independent variables. The distance-dependent models with the highest adjusted R 2 included all of these variables in addition to a variant of the area potentially available index, which is based on the spatial tessellation of the point pattern of trees in the stand. Addition of this spatial index produced only a small (<.01) increase in adjusted R 2 for models of both species. The relatively small amount of increase was due to three factors; thinning resulted in an even distribution of growing space among residual trees, tree size explained much of the variation in local competitive stress and the competitive neighborhood of individual trees was large relative to the size of the sample plots. The results suggest that the additional effort and expense required to obtain spatially referenced stand data for developing empirical forest growth models in similar stands is not justified.

Forest Characteristics Associated with Abundance of Foraging Ants (Hymenoptera: Formicidae) in Connecticut

Thirty forested plots throughout Connecticut were established to determine the associationof forest site conditions with population sizes of common ants (Hymenoptera: Formicidae).The plot characteristics investigated were plot slope, elevation,longitude,latitude, basal area of trees and number of understory stems of species associated with moist conditions, and total length of intersection of rocks along 4 plot transects.Two plot characteristics were consistently related to ant abundance: plot latitude and basal area of trees that prefer mesic or wet sites. Ant numbers were less at high latitudes and in moister sites. Implications of these results for improving biological control by ants are discussed.

Coarse woody debris in an old-growth deciduous forest on the Cumberland Plateau, southeastern Kentucky

Volume and mass of coarse woody debris (&gt; 20 cm diameter) in an old-growth forest on the Cumberland Plateau in southeastern Kentucky averaged 66.3 m3/ha and 21.8 Mg/ha, respectively. Coarse woody debris was patchily distributed among 80 sample plots (0.04 ha each), with 10 plots containing 39% of the total mass. Coarse woody debris mass was inversely, although not strongly, related to plot basal area. While 23 species contributed to the accumulation of coarse woody debris, five accounted for 72% of the total mass. These included Quercusprinus L. (25% of the total), Fagusgrandifolia L. (16%), Quercusalba L. (12%), Castaneadentata (Marsh.) Borkh. (11%), and Quercusvelutina Lam. (9%). The few studies of coarse woody debris in old-growth deciduous forests of North America suggest a regional pattern of accumulation correlated with temperature. In warmer regions, old-growth deciduous forests accumulate a mass in the range of 22–32 Mg/ha, while in cooler ecosystems, coarse woody debris ranges from 34 to 49 Mg/ha.

Stand dynamics in a primary warm-temperate rain forest analyzed by the diffusion equation

The change in the stand structure with recovery after gap formation was analyzed by using the diffusion equation for a primary warm-temperate evergreen rain forest on Yakushima Island of southern Kyushu, Japan. The tree density in dbh classes, the mean growth rate of dbh and the variance of dbh growth rate in closed stands and gaps were expressed as functions of dbh. The change in dbh frequency calculated from these functions and the observed tree mortality clarified the fact that the dbh distribution in the closed stands is rather stable but becomes more positively skewed with time. Attention was also paid to the change in stand basal area (BA) in 20m×20m plots. The log-normal distribution expressed the frequency distribution of BA in the forest as a whole. The growth rate of BA in plots without new gap formation was formulated as a function of BA. Gap formation rate observed in 0.8 ha closed stands in recent four years was 1.3% per year. This rate agreed with the result of calculations based on the assumption that the frequency distribution of BA is stationary with time.

Four Decades of Secondary Succession in Two Lowland Permanent Plots in Northern Lower Michigan

Two 0. 1-acre lowland permanent plots in northern lower Michigan were compared for changes since 1938 in community structure and population dynamics. One was on wet sandy soil with Populus tremuloides dominant in 1938, and was severely affected by a storm in 1940. The other was on wet organic soil with Thuja occidentalis, Picea mariana and Abies balsamea present and was unaffected by the 1940 storm. In the conifer plot basal area continuously increased, whereas species richness and density peaked ca. 30 years after logging and burning and declined to a low in 1981. In general, survivorship was highest for trees already established in 1938, and numbers of recruits as well as their diameter growth and survivorship decreased as stand age increased. As a result, 85%o of the 1981 population of conifers was present in 1938. The present population of trees was most strongly influenced by conditions at the time of establishment at least 50 years ago, and events since then have been of minor importance. In contrast, a storm in 1940 destroyed the overstory aspen of Plot 6, causing an initial decrease in basal area, temporary increase in species richness, and shift in dominance from trees to shrubs. Eleven years later, the basal area had returned to prestorm levels, largely because of increases in Alnus rugosa. By 1981 Fraxinus nigra had increased in number; Acer rubrum, Populus tremuloides, Abies balsamea and Betula papyrifera had larger dbh but low density because of high mortality and low recruitment. In 1981, 41 years after the storm, the plot was still dominated by a dense shrub layer of Alnus rugosa and Ilex verticillata.

Fertilization of a pole-sized maple stand: 10-year results

A 48-year-old stand of Acersaccharum Marsh. and A. rubrum L. in northeastern Wisconsin, U.S.A., was fertilized with 168 kg/ha (150 lb/acre) of elemental N, P, N + P, or N + P + K in May 1966. Trees were stratified by crown class and initial diameter. Ten-year diameter and basal area growth were evaluated by analysis of covariance with initial plot basal area (IBA) as the covariate and by stepwise multiple regression in hierarchal models. Both diameter and basal area growth were influenced greatly by initial diameter and stand density. IBA accounted for 65% of the variation in diameter growth and 49% of the variation in basal area growth.Fertilization decreased diameter growth and increased mortality of suppressed trees. Pole-sized maples in intermediate and codominant crown positions tended to respond to fertilization with N and N + P but the differences were not statistically significant. Dominant trees grew more than did intermediates or codominants, but fertilization response could not be evaluated. Treatment effects were confounded by widely varied stand and site conditions. Results illustrate conditions likely to be encountered in fertilizing northern hardwoods on an operational scale.

An analysis of throughfall and stemflow in mixed oak stands

Net rainfall was studied under immature stands of mixed oak in southern New England. Throughfall did not differ significantly between stands. Stemflow was measured from all trees on one‐fortieth‐acre plots. Although yields varied greatly between plots, plot sampling of stemflow within 15% error tolerance was considered practical in most mixed oak stands. Both average dbh of dominant and codominant trees on stemflow plots and plot basal area showed high positive correlations with stemflow. Analysis of individual stems showed species and dbh highly correlated with stemflow. Black oaks yielded more stemflow than white oaks. The only storm characteristic significantly correlated with stemflow was storm size. Stemflow was greater during the dormant season.