Competition among Secondary-Successional Pine Communities: A Field Study of Effects and Responses

Abstract

Three common associates on secondary-successional pine sites (Andropogon virginicus, Liquidambar styraciflua, and Pinus taeda) were established in a field study in which a wide array of plant densities and species proportions were established using an additive series design. To mimic a specific competitive scenario (i.e., a managed earlysuccessional Pinus stand), Andropogon and Liquidambar were established a year prior to the establishment of Pinus. Competitive effect (the attenuation of resources) and competitive response (the growth of each species as a function of resource availability) were determined.Effect on soil water varied among species, depth of soil, and time. In the surface soil, soil water was largely influenced through non-uptake effects, while uptake effects were predominant in deeper portions of the solum. When competitor abundance was expressed on an aboveground biomass basis, rather than a density basis, species differences in effects on soil water were eliminated. Differences among the species in effects on soil water per unit leaf area or leaf biomass appear to be largely explained by differences in stomatal conductance. Predawn leaf-water potential was integrated over the season using a waterstress integral. Analysis of the water-stress integral suggested that Liquidambar and Andropogon both affected water available to Pinus; however, only Liquidambar affected Andropogon, and only Andropogon affected seasonal water available to Liquidambar. Light was most strongly influenced by Liquidambar density; however, as Andropogon density increased, the effects of Liquidambar were reduced.Andropogon response was correlated with light but not with water stress or leaf nitrogen. This reflects high light requirements and high water use efficiency of C 4 plants. Liquidambar response was related to water stress and leaf nitrogen, perhaps reflecting the greater nitrogen requirements of hardwoods. Pinus response was significantly related to all three resources individually, i.e., water stress, light, and leaf nitrogen. Pinus response was better explained by a regression model that included light and water stress than by water stress or light alone. Pinus growth as a function of water stress and light indicated that communities dominated by Liquidambar largely reduced Pinus growth through reduction in light, while communities dominated by Andropogon reduced Pinus growth primarily by increasing water stress. In mixed communities of Liquidambar and Andropogon, pine growth was constrained more equally by light and water stress.

Competition, traits and resource depletion in plant communities

“…Björkman 1981; Meziane and Shipley 1999;Saldana et al 2005). Phytometer base , which is a direct indicator of the soil water status perceived by plants (Boyer 1995), decreased in response to soil water shortage due to competitors, as reported in previous studies (Mitchell et al 1999;Gebauer et al 2002). Predawn water potential values lower than ¡1.0 MPa were recorded in half of the situations (Fig.…”

Community homogenization and the invasiveness of commensal species in Mediterranean afforested landscapes

“…Several authors describe the occurrence of strong successional processes (Allen et al 1995;Ogden et al 1997), possibly caused by combined effects of low light availability and intense belowground competition from the dense tree layer. Both are known to be major direct or indirect factors in forest successions (Connell and Slatyer 1977;Mitchell et al 1999;Thysell and Carey 2001;Roberts 2002). Indeed, the negative relation between pine canopy cover and maqui cover documented in this study supports the notion that competition for light and/or other resources was a problem for indigenous vegetation and promoted biotic homogenization in the pine plantations.…”

Vascular diversity patterns of forest ecosystem before and after a 43-year interval under changing climate conditions in the Changbaishan Nature Reserve, northeastern China

“…Such effects extend to the entire community through the interactions between plants (Mitchell et al 1999;Klanderud and Totland 2005). Hence, the changes in the three forest types can be studied by analyzing the unique features of the species, the composition of the community, the degree of diversity, climate change, and human impact factors.…”