Co-occurring Tree Species Research Articles

Different Incidences of Pine Wilt Disease in Pinus densiflora Seedlings Growing with Different Tree Species

Abstract Field-grown Japanese red pine (Pinus densiflora) seedlings were inoculated with the pine wood nematode (Bursaphelenchus xylophilus) in early July 1991 to clarify the effect of co-occurring tree species on the susceptibility of P. densiflora to pine wilt disease. Sixteen weeks after inoculation, 48, 33, 14, and 18% of pine seedlings were diseased when they grew with Alnus sieboldiana, with Sarothamus scoparius, with the naturally associated species of P. densiflora such as Ilex pedunculosa and Eurya japonica, and in a pure stand of P. densiflora, respectively. When associated with A. sieboldiana or S. scoparius, pine seedlings quickly had visual discoloration of foliage. Twenty percent of P. densiflora seedlings treated with water died within 6 months when growing in the stand with A. sieboldiana, suggesting that the seedlings were stressed. The susceptibility of P. densiflora seedlings to pine wilt disease was enhanced by the different tree species co-occurring with the seedlings. For. Sci. 41(4):841-850.

CO2-induced growth enhancements of co-occurring tree species decline at different rates.

To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence the long-term growth of tree seedlings, six co-occurring members of temperate forest communities including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum), yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra L.) were raised in a glasshouse for three years in a complete factorial design. After three years of growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient CO2 atmospheres, however, magnitudes of CO2-induced growth enhancements were contingent on the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO2-induced growth enhancements after one year of growth were greater than after three years of growth, though species' growth enhancements over the three years declined at different rates. These results suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence forest productivity via long-term species compositional changes in forests.

Co‐Occurring Tree Species Change Rank in Seedling Performance with Resources Varied Experimentally

Parallel hypotheses are advanced: (1) the distribution of resources in mesic upland temperate forests is patchy at a scale that is fine for adult trees and coarse grained for seedlings and (2) co—occurring tree species differ in abilities to exploit resources, resulting in differences in species rank order, by absolute growth rates of seedlings, among different resource combinations. Spatial variation in growth rate ranking among species may translate, through competition, into patterns of relative species abundances of seedlings that could persist in the community composition of adult trees. Here I report the results of factorial greenhouse experiments that address the second hypothesis. Seedlings of six co—occurring tree species of temperate eastern North American upland forests showed strong interspecific differences in growth rates and patterns of biomass allocation in response to variation in light and mineral nutrients. The ranks of four species in growth measures associated with competitive ability, absolute rates of change in stem height, total leaf area, and root biomass, varied significantly among nutrients treatments. Seedlings of American chestnut, Castanea dentata, ranked highest in traits associated with competitive ability over the broadest range of combinations of resource levels.

Leaf and Simulated Whole‐Canopy Photosynthesis in Two Co‐Occurring Tree Species

The goal of this study was to explore how leaf and canopy level difference interact in determining total canopy productivity. Maximum rates of carbon gain and transpiration were found to be higher in leaves of the deciduous oak quercus lobata than in the co—occurring evergreen oak Quercus agrifolia. However, the efficiency of water and nitrogen use is greater in leaves of Q. agrifolia. A biochemically based model of annual leaf photosynthesis using environmental field data indicates that the evergreen habit in Q. agrifolia partially compensates for the lower photosynthetic capacity of leaves and increases the amount of photosynthate produced per unit water or nitrogen. Simulations indicate that with low N or water availability, the evergreen species can produce canopies with greater annual production than the deciduous species; the converse is true at higher levels of resource supply. Some of the patterns of distribution of these species in northern California may be explained by examining the relationships between source availability and estimated annual production.

Growth responses of seven major co-occurring tree species of the northeastern United States to elevated CO2

We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (Fagusgrandifolia Ehrh.), paper birch (Betulapapyrifera Marsh.), black cherry (Prunusserotina Ehrh.), white pine (Pinusstrobus L.), red maple (Acerrubrum L.), sugar maple (Acersaccharum Marsh.), and eastern hemlock (Tsugacanadensis (L.) Carr). We also tested whether the degree of shade tolerance of species and the age of seedlings affected plant responses to enhanced CO2 levels. Seedlings that were at least 1 year old, for all species except beech, were removed while dormant from Harvard Forest, Petersham, Massachusetts. Seeds of red maple and paper birch were obtained from parent trees at Harvard Forest, and seeds of American beech were obtained from a population of beeches in Nova Scotia. Seedlings and transplants were grown in one of four plant growth chambers for 60 d (beech, paper birch, red maple, black cherry) or 100 d (white pine, hemlock, sugar maple) under CO2 levels of 400 or 700 μL•L−1. Plants were then harvested for biomass and growth determinations. The results showed that the biomass of beech, paper birch, black cherry, sugar maple, and hemlock significantly increased in elevated CO2, but the biomass of red maple and white pine only marginally increased in these conditions. Furthermore, there were large differences in the magnitude of growth enhancement by increased levels of CO2 between species, so it seems reasonable to predict that one consequence of rising levels of CO2 may be to increase the competitive ability of some species relative to others. Additionally, the three species exhibiting the largest increase in growth with increased CO2 concentrations were the shade-tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enhance the growth of relatively shade-tolerant forest trees to a greater extent than growth of shade-intolerant trees, at least under the light and nutrient conditions of this experiment. We found no evidence to suggest that the age of tree seedlings greatly affected their response to elevated CO2 concentrations.

Vegetative and reproductive phenology of Ziziphus mucronata subsp. mucronata (Rhamnaceae)

Vegetative growth of Ziziphus mucronata Willd. subsp. mucronata (Rhamnaceae) commences in spring and leaf fall starts towards the end of July. Flowering coincides with that of three co-occurring tree species. It shares pollinators only with Olea europaea subsp. africana , but the inconsistency and much shorter duration of flowering minimizes competition with this species. Some Z. mucronata individuals appear to function as males. A population comprises juveniles (vegetative), subadults (males) and adults (fully reproductive). The relation between height and reproductive potential of the individual plants indicates that small individuals in the population have a lower probability of flowering than the larger ones. The monomorphic flowers of Z. mucronata are protandrous and dichogamous. Dichogamy is complete and the flower can furthermore be regarded as heterodichogamous and herkogamous.

Reproductive Strategies and the Co-occurrence of Climax Tree Species

In a central New Hampshire forest, three co-occurring tree species were found to occupy different positions on a reproductive strategy gradient. These reproductive strategy differences, in part, described separate niches for the species. The three-species complex is hypothesized to form a dynamic climax overstory characterized by cyclical replacement of one dominant species by another.