Windthrow Research Articles

Suppression of Spruce Beetle Attacks by MCH Released from Bubble Caps

Abstract The attack density of the spruce beetle, Dendroctonus rufipennis (Kirby), was reduced to 10-25% of that on untreated felled Engelmann spruce (Picea engelmannii) trees, when the trees were treated with 9-15 bubble cap release devices, each releasing the aggregation inhibitor MCH at 1-3 mg/24 h at 20°C. In the first experiment, deterioration of many release devices reduced the suppression effect. In the second experiment, MCH reduced attacks by 85%, and total brood production by 79-88%. The attacks on the MCH treated trees occurred late, as evidenced by the early stage of development of galleries and brood on these trees. Semiochemical-baited traps at untreated, or MCH-treated, felled trees caught few beetles, and had no effect on the attack density. The results show that manually applied MCH can be used operationally to reduce attacks by the spruce beetle on small groups of wind thrown trees. Mass trapping of spruce beetles is not feasible with currently known semiochemicals. West. J. Appl. For. 4(2):49-52, April 1989.

Wind Throw and Tree Replacement in a Climax Beech-Maple Forest

Over a period of 25 seasons, wind throw of trees larger than 25.4 cm dbh at Warren Woods, Michigan, USA, was at the rate of 0.2 trees ha-1 yrC. Beeches Fagus grandifolia Ehrhart larger than 76 cm dbh were more susceptible than smaller trees. In forests where the subcanopy trees are heavily dominated by sugar maple Acer saccharum Marshall and beech, wind throw appears not to maintain canopy diversity; nearly all the replacement trees for current gaps are these two species. Maintenance of canopy diversity in such mature forests is probably by more extensive and severe perturbation. Three to five thousand years would be required for the total soil surface to be disturbed by wind throw.

Developmental and Environmental History of the Dismal Swamp

Pollen analysis of several cores from the Dismal Swamp in southeastern Virginia have indicated that the swamp is a relatively young feature, having begun to develop along drainage lows as recently as the late—glacial. Formation of extensive fresh—water marshes along streams appears to have been brought about by general water—table changes controlled by the post glacial rise of sea level. As the sea continued to rise, marsh development proceeded inland and fine—grained organic sediments began to accumulate. By 6,000 years B.P. approximately 50% of Dismal Swamp area had been mantled by fine—grained peat deposits. From 6,000 to 3,500 B. P. peat accumulation continued, but at an appreciably lower rate. The corresponds both to the hypsithermal interval and to a distinct slackening in the rate of sea—level rise. By 3,500 B.P. peat had mantled virtually all of the interfluves and "islands" within the swamp. The pollen diagrams suggest a gradual change from boreal spruce—pine forests during the full—glacial, to somewhat less boreal pine—spruce during the early late—glacial, to hardwood forests containing many species characteristic of the present northern hardwoods forests during the latter portion of the late—glacial, to hardwood—dominated forests containing species now found in southeastern Virginia during the early postglacial. Although precise vegetational and environmental reconstructions are not possible, this general sequence suggests a unidirectional climatic amelioration from conditions comparable to those in northern New England during the full—glacial to a climate comparable to the present by 8,000 years B.P. The climate may have been warmer and drier during the hypsithermal, but the observed changes could just as easily be a result of a slackening in the rate of sea—level rise. The cypress—gum forests that have characterized the Dismal Swamp for the past 3,500 years have been variable both spatially and temporally. These variations doubtless reflect local differences in water table, peat depth, fires, wind throws, and a variety of human disturbances. The origin of Lake Drummond remains an enigma. It is a young feature of the swamp, apparently originating only 4,000 years ago. It is not the last vestige of an earlier open—water phase of the swamp.

Shrub and Herb Continua of Upland Forests of Northern New Jersey

The shrub and herb strata of 55 upland forest stands in northern New Jersey were studied. For the herbs, frequency and cover data were gathered by means of 0.5 x 2 m quadrats; for the shrubs, cover and frequency data were gathered on 5-rn line transects. Data were obtained from 36 to 48 points in each stand. Importance values were so calculated based on relative cover and relative frequency for shrubs and herbs as to give a total of 200. Using the method of leading dominants, climax adaptation numbers (ranging from 1 to 10) were assigned to 194 herbaceous taxa and 45 shrub taxa. The terminal shrub species were Lindera benzoin (10) and Gaylussacia baccata (1). The terminal herb species were Arisaema triphyllum (10) and Gaultheria procumbens (1). A continuum index number was calculated for each stand, with a possible range of 10 to 100. The shrub continuum shows a wide range of stand composition reflecting the broad spectrum of habitat conditions in the area, the index numbers ranging from 33-100. The herb continuum did not show as broad a pattern as did the shrubs, the continuum index numbers for stands based on the herbaceous layer ranging from 19 to 69. This was interpreted as primarily the result of (1) persistence in mesic forests of clonal relicts representative of earlier successional stages, the result being a dilution' effect on the true mesophytic forest herb composition of a stand and (2) the frequent disturbance, characteristic of the forests of northern New Jersey principally through wind throw and drought, which results in establishment of herbaceous species more characteristic of earlier successional stages.

Distribution of subfossil forest remains, eastern South Island, New Zealand

Abstract The distnbutiOn of subfossil forest remains collected in the eastern part of the South Island of New Zealand 15 outlined. Surface logs, buried wood and charcoals, wind–throw dimples and buried podsols provide convincing evillence of a former widespread forest cover over now–treeless tracts of the South Island. Most of the Wood and charcoals discovered have been identitied, and collecting sites plotted on a map. A broad distinction can be drawn between probable podocarp and beech forest areas.Radiocarbon dates for a number of wood and charcoal samples are presented and most of these point to forest destruction by fire since the advent of man In New Zealand within the last 1.000 years or so.Older dates presented obviously lie outside the period of human occupatIOn of New Zealand and the fires that produced these ancient charcoah are assumed to have originated from mltural causes. The pre~ent vegetallon on former forest sites and the distribution of forest remains in relation to existing forest are discussed, and some of the leading opinions as to the causes of forest destruction arc briefly reviewed

Infestation Patterns of Douglas-Fir Beetle in Standing and Windthrown Trees in Southern Idaho

To facilitate population studies, the infestation patterns of Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, were investigated in standing and wind thrown trees in southern Idaho. Three infestation zones were recognized in most standing trees. The basal zone was infested least densely, progeny did not result from about one-fourth of the galleries, and the infestation varied more than in the upper portions. Typically, a middle zone comprised four-fifths of the infested stem, and the infestation there was densest and most successful as well as least variable. At the top of the infestation, the proportion of unsuccessful galleries again increased and fewer live progeny were present. In windthrown trees, the infestation varied circumferentially, but lengthwise stratification was not demonstrated. Both galleries and progeny were denser on the shaded underside than on the sun-exposed upper side of down trees. Although lengthwise differences were not demonstrated, the infestation was least variable mid way along the infested length, thereby favoring the underside in that vicinity for sampling of down trees.