Growth and Biomass Partitioning of Northern Red Oak and Yellow-Poplar Seedlings: Effects of Shading and Grass Root Competition

Author： Kolb T. E. Steiner K. C.

Publisher： Society of American Foresters

ISSN： 0015-749X

Source： Forest Science, Vol.36, Iss.1, 1990-03, pp. : 34-44

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Abstract

Seedling growth of northern red oak (Quercus rubra L.) and yellow-poplar (Liriodendron tulipifera L.) were compared under conditions of grass root competition (Poa pratensis L.) and shading. Each species was grown from seed for 2 years in each of four environments: (1) 100% sun/no grass, (2) 100% sun/grass, (3) 37% sun/no grass, and (4) 37% sun/grass. Leaf, stem, and root biomass and projected surface areas of leaves and roots were measured by destructive harvests in each year. Growth allocation to organs was compared among environments by coefficients of the allometric equation Y = aX^b. Total seedling biomass of oak was greater than yellow-poplar in all environments and harvests because of an initial growth advantage from larger seed reserves. However, biomass relative growth rate of yellow-poplar was greater than oak in all environments. Grass root competition reduced biomass of both species, but more for yellow-poplar than for oak. In the absence of grass, shading reduced biomass of both species, especially yellow-poplar, while shading in the presence of grass resulted in a nonsignificant increase in biomass of both species. In all environments, shoot-root ratio and partitioning of leaf and root biomass to surface area for yellow-poplar was greater than oak. In response to competition for soil resources, both species increased biomass partitioning to the root at the expense of the shoot. In response to shading, yellow-poplar increased leaf area proportion, while oak did not. Thinner leaves and a more fibrous root system were more important in explaining yellow-poplar's higher relative growth rate under conditions of shading and root competition compared to oak than differences in shoot-root weight ratio or plasticity in biomass partitioning. For. Sci. 36 (1):34-44.