Maximum Basal Area Research Articles

White cypress pine in N.S.W.: growth patterns and optimal thinning regimes for 60 to 80 year old stands

Summary The growth of 60-year-old white cypress pine stands at five locations in the Pilliga Management Area of N.S.W. is analysed over a 20 year period following thinning. The growth pattern and the optimum thinning range differed from that previously reported for this species. At four of the five locations stand basal area increment was independent of basal area for a range of values forming a ‘plateau’ of maximum increment. For these sites, no stand basal area increment rise or decline was detected with increasing residual basal area, over the range 6 to 18 m2 ha−1. The other location exhibited a growth pattern akin to the phenomenon of “lock-up” where increment did not “plateau” but peaked at a basal area of about 8 m2 ha−1 and then declined markedly at higher basal area without corresponding mortality. The optimum thinning range, where both tree size and site utilisation are maximised, was determined to be within the range 6 to 10 m2 ha−1. Maximum basal area increment ranged from 0.30 to 0.40 m2 ha−1...

Derivation of a competitive index for individual trees from seasonal growth patterns

A competitive index for lodgepole pine (Pinuscontorta Dougl.) trees in central Oregon is developed from seasonal basal area growth and an indirect estimator of foliar leaf area. Differences in seasonal basal area growth and the ratio of basal area growth to sapwood basal area between trees with and without neighbors are used to document growth reductions owing to the proximity of competing individuals. A regression between basal area growth and sapwood basal area (an estimator of leaf area) is used as a predictor of maximum potential basal area growth for trees growing free of competition. The competitive index is determined as the ratio of actual to potential basal area growth for individual trees. This index standardizes growth against differences in tree size and site conditions. Plant and soil water relations are considered as possible mechanisms of competitive interaction. Moderate minimum seasonal values of predawn leaf pressure potentials (−0.76 to −0.92 MPa) and minor differences between trees in different competitive classes led to the conclusion that soil water may not be the primary mechanism of competition on this site.

Stand Structure and Yield Relationships in a 20-Year-Old Loblolly Pine Spacing Study

Abstract A loblolly pine (Pinus taeda L.) spacing study on a Piedmont site (SI 75, base age 25) had at age 20 a maximum yield of 49 cords per acre with a near maximum basal area of 187 square feet at a spacing of 8 x 8 feet. Comparative yields on the other spacings tested were: 6 x 6, 188 ft² and 43 cords; 10 x 10, 166 ft² and 45 cords; 12 x 12, 152 ft² and 43 cords. Sawtimber volume in trees larger than 9.5 inches in diameter rose from zero at 6 x 6 feet to almost 10,000 board feet per acre at 12 x 12 feet. Survival on the 6 x 6 plots was 71 percent; 8 x 8, 87 percent; 10 by 10, 92 percent; and 12 x 12, 93 percent.

Principles and practice of foliar analysis as a basis for crop-logging in pine plantations

Progress towards the introduction of crop-logging as a management tool is illustrated by the development of multiple regression equations relating basal area increment to various stand parameters including foliar phosphorus levels. Mixed mode regression analysis was used, removing foliar P variables first and adding other variables stepwise. The model which best described the relationships sought was of the form: $$\log B = a_1 P + a_2 P^2 + a_3 \frac{{BA.SI}}{{Age}} + a_4 \frac{{SI}}{{BA.Age}}$$ where B = average annual basal area increment for the three-year period preceding or subsequent to foliar sampling; P = percentage phosphorus in foliage; BA = basal area standing at the time of sampling; SI = site index, defined as predominant height (predicted or actual) in feet at age 25 years; and Age = age of plantation in years at time of sampling. Using this equation, the critical level of phosphorus in slash pine (Pinus elliottii Engelm.) is set at 0.075–0.080 per cent and in loblolly pine (P. taeda L.) at 0.095–0.105 per cent. Critical level is here defined as the foliar P concentration associated with 90 per cent of maximum basal area increment. Over the range of parameters examined, the critical levels so determined are, for all practical purposes, independent of age, site index and stand density. Utilization of critical foliar nutrient levels in crop-logging requires a know-ledge of fertilizer — soil — plant interactions which can be derived in part from the fertilizer trials used to establish critical levels in the first instance.

Dynamics of Black Cherry (Prunus serotina Erhr.) in Southern Wisconsin Oak Forests

Black cherry occupies a key position in the dynamics of oak (Quercus spp.) forests in southern Wisconsin. Its relative importance in sapling and small—tree sizes averaged over 50%, and in some stands it was the only species in these strata. Age analysis of 854 cores showed that 58% of all black cherry stems were established between 1931 and 1941. The appearance of large amounts of black cherry in the 1930 decade was the result of drought and livestock—feed shortages. The latter were especially severe in 1934 and 1936 and resulted in large—scale disturbance of forests through grazing and possibly extensive cutting of forests for foliage. The presence of a strong shrub component exerted a major influence on the dynamics of the oak forest. An inverse relationship existed between overstory tree basal area and the importance of shrubs. Although density and cover of tree seedlings were independent of tree basal area and shrub cover, seedling numbers were insufficient for adequate restocking of most stands. In clear—cut forests the shrub layer was extensive, and regrowth of trees was largely confined to stump sprouts. Shrubs in disturbed forests averaged 38,635 stems/acre, 4,535 square inches basal area/acre, and 145.8% cover. In undisturbed forests, shrub competition (average 16,231 stems/acre, 1,036 square inches basal area/acre, and 51.4% cover) largely precluded seedling establishment by tree species, and maximum basal area levels in these forests were not maintained. Growth and survival of black cherry in the understory depended on the complex interaction of environmental factors. Tree overstory basal area and soil available water were the most significant factors controlling its vigor. Suppressed stems of cherry were as old as 60 years. Growth patterns in stem cores showed that stems responded to release after 39 years of suppression. The capacity of black cherry to develop basal sprouts and the occurrence of light intensities greater than 1,200 ft—c in the understory greatly aided its survival in this stratum. The important role of black cherry in the dynamics of the oak forests was based on opportunistic characteristics including widespread dispersal, delayed germination of seeds, and flexible seedbed requirements. Forest conditions, such as the isolation of forests as woodlots, pioneer environmental conditions, and widespread disturbance, predisposed invasion by opportunistic species. Dynamic processes were characterized by general rather than gradient compositional changes. Patterns of replacement were not orderly and predictable, but irregular as a result of chance dispersal and local catastrophe. Although not uncommon in oak forests in the northeastern United States, invasion by Acer saccharum is not occurring in southern Wisconsin. Succession to Acer—Tilia is confined to specific sites. The overall existing pattern is one of increasing diversity typical of many pioneer communities in an early phase of colonization.