Growth dynamics of oak seedlings ( Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm.) from gallery forests: implications for forest expansion into grasslands

Abstract

Seedling growth dynamics of Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm. were compared over a 3-month period under optimal growth conditions. These two species are the dominant trees at the western limit of the eastern deciduous forest, and are typically confined to gallery forests along stream beds in tallgrass prairie. Since tallgrass prairie is characterized by a highly variable climate and is prone to periodic drought, we hypothesized that these oaks would have rapid root growth and produce deep taproots as seedlings, enabling them to avoid drought stress and persist in this region. These traits may also facilitate forest expansion into the more xeric tallgrass prairie if fires are suppressed. Taproots of Q. macrocarpa and Q. muhlenbergii grew to approximately 140 cm and 100 cm in length, respectively, after 104 days. In both species, 65% or more of seedling biomass was allocated below ground, and root/total biomass was significantly greater in Q. muhlenbergii at 0-20 and 21-40 days after germination. The seedling taproot elongation rates reported here are much greater than rates reported in other eastern deciduous forest trees. Long-term precipitation data and soil moisture patterns from tallgrass prairie, when combined with rapid taproot elongation rates, suggest that soil moisture may not limit oak establishment or growth in tallgrass prairie in most years, although water uptake by roots was not measured in this study. Other factors, such as fire, herbivory, and seed predation and dispersal may be equally important in constraining the distribution of these species to gallery forests.

Survival and early growth of mixed forest stands installed in a Mediterranean Region: Effects of site preparation intensity

“…Height growth occurred only in spring (24-27 and 36-39 months) whereas the diameter growth occurred in spring and summer (27-30 and 39-42 months) (Table 5). This growth pattern is consistent with the strategy of adaptation to summer water deficits (Danner and Knapp, 2001). The mean increase in both height and diameter for each one of the species shows a very similar trend, but the response of the two species is completely different (Fig.…”

Root system of Quercus suber L. seedlings in response to herbaceous competition and different watering and fertilisation regimes

“…Deep taproot of Q. suber trees during the early stage Q. suber seedlings developed a deep taproot irrespective of the system and treatments, probably as a common mechanism found in other oak species (Danner and Knapp, 2001;Cubera et al 2009a). When growing in bare soil (Oak BS ), both the root and shoot biomass of seedlings were reduced under drought conditions.…”

Mature trees versus seedlings: Differences in leaf traits and gas exchange patterns in three co-occurring Mediterranean oaks

“…Oaks have rapid root growth and produce deep taproots as seedlings [8,30]. However, it may take some years to pass the maximum penetration depth of the roots of the herbaceous plants and thus reduce their competitive effects ( [3,31], Mediavilla, personal observation).…”