Abundance Of Cones Research Articles

Red pine cones: distribution within trees and methods for sampling

Numbers of Pinusresinosa cones (1-month-old pistillate strobili) per branch increased with branch length and exposure. South branches invariably had significantly more cones than other branches. Cones per branch decreased from top to bottom of the crown and with increasing stand density. Highest cone yields will probably occur at densities of 80 to 100 stems/acre (181 to 277 stems/ha). Cone abundance per acre (1 acre = 0.404 685 6 ha) can be efficiently estimated [Formula: see text] by sampling three branches from both upper and middle crown thirds of only 12 trees per stand.

The role of insects in the dynamics of cone production of red pine.

The mortality of red pine cones was studied for several consecutive years using life tables in eight different stands in the northern Great Lakes States. Usually less than 20% of a cohort of female flowers survived to maturity. Insects were the main source of mortality and were primarily responsible for annual fluctuations in the abundance of mature cones. Insects were probably also responsible, along with late summer weather (especially precipitation), for influencing the rate of initiation and differentiation of flower bud primordia, as shown in a model of the flowering-cone production processes. These studies suggest that the devastation of developing cone crops by insects may actually enhance flower primordia production and thus the future abundance of feeding and breeding sites for cone insects.

RELATIONSHIP BETWEEN CONE CROP SIZE AND CONE DAMAGE BY INSECTS IN RED PINE SEED-PRODUCTION AREAS

AbstractAnnual cone abundance and insect damage to cones are highly variable in red pine seed-production areas. Cone crop size fluctuates almost unpredictably from year to year, but the number of insect-attacked cones tends to increase annually unless limited by cone abundance. Sixty-six per cent of the variation in cone damage can be associated with variations in cone abundance. This information, coupled with the fact that red pine cone insects are almost entirely dependent on red pine cones for food, implies that crop size is highly important in regulating populations of cone insects. Insects will be most devastating in areas where crop size varies little from year to year.