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A Search For Phytotoxins Influencing Germination And Early Growth Of Ponderosa Pine, United States Department Of Agriculture, Forest Service
A Search For Phytotoxins Influencing Germination And Early Growth Of Ponderosa Pine, United States Department Of Agriculture, Forest Service
Forestry
A series of laboratory and field experiments were conducted to determine if mature ponderosa pines produce a substance (phytotoxin) that inhibits the germination and growth of seedlings directly under the tree crown. Neither live nor dead materials collected from ponderosa pines produced either volatile or water-soluble phytotoxins that drastically inhibited germination of seeds or growth of seedlings. Seed overwintering beneath the canopy of mature pine, or planted in soils collected there, showed reduced germination. Exact cause of the reduction was not determined. If weak phytotoxins were responsible, they did not inhibit growth of seedlings that germinated.
Influence Of Some Environmental Factors On Initial Establishment And Growth Of Ponderosa Pine Seedlings, United States Department Of Agriculture, Forest Service
Influence Of Some Environmental Factors On Initial Establishment And Growth Of Ponderosa Pine Seedlings, United States Department Of Agriculture, Forest Service
Forestry
Study plots were established to determine the effects of various environmental factors on ponderosa pine seed germination and initial seedling establishment and growth. A series of soil surface treatments were performed on plots in two locations: within or under the influence of overstory pine trees and in openings away from the pine influence. Seed germination was significantly greater in the opening plots. The overstory canopy and forest floor restricted the amounts of precipitation, light, and heat reaching the soil and probably decreased germination. Cutworms, birds, and small mammals caused the greatest seedling mortality. The largest seedlings occurred in the fire-treated …