Architectural and growth traits differ in effects on performance of clonal plants: an analysis using a field-parameterized simulation model

Abstract

Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual-based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short-term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus . These plants all co-occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes.Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models.Species traits are general, genetically determined characteristics of morphology and physiology. Such traits are often used in ecology to group species; these groups are then used to explain and predict community structure and dynamics (Grime et al.

Community assembly by limiting similarity vs. competitive hierarchies: testing the consequences of dispersion of individual traits

“…1; see also Wildov a et al 2007; Wildov a, . It incorporates competitive processes between ramets through density-dependent resource uptake and accumulation.…”

“…and Schoenoplectus pungens (Vahl) Palla; no other species constitutes > 5% of the biomass. These species span a range of growth forms from tussock-forming to runners and are described in detail in Wildov a et al (2007) and Yu et al (2012). The model was parameterized primarily using direct estimation from measurements of plants either collected in fens in south-eastern Michigan, USA, or grown in a short-term (90 days) garden experiment (see Wildov a et al 2007 for details).…”

“…We thus use in silico manipulations of values of traits around the baseline observed values for all species in the community to mechanistically examine the effects of trait structure on community diversity in a way that can never be attained in a field system (see e.g. Pacala, Canham & Silander 1993;Rees, Grubb & Kelly 1996;Peck 2004;Marks & Lechowicz 2006;Turnbull et al 2007;Wildov a et al 2007). By examining a number of different traits for the full set of coexisting species in two different communities, we test for generality in linkages between levels of trait dispersion and community processes.…”

“…We simulated two different field-parameterized systems to attain greater generality: (i) a four-species mountain grassland in Central Europe parameterized by and (ii) a five-species fen community in Michigan parameterized by Wildov a et al (2007); (see also Yu et al 2012). In both cases, the parameterized species used in simulations represent all the common species from the community.…”

Do Clonal and Bud Bank Traits Vary in Correspondence with Soil Properties and Resource Acquisition Strategies? Patterns in Alpine Communities in the Scandian Mountains

“…Grime et al (1997) found that traits like root and shoot foraging were associated with foliar concentrations of N, P, K, Ca and Mg, the capacity for growth in productive conditions or the inability to sustain yield under limiting supplies of nutrients. However, despite the large body of empirical work conducted in the field of comparative ecology, both in the areas of clonality/vegetative reproduction and of plant traits related to resource acquisition and competitive ability (Jónsdóttir and Watson 1997;Bellingham and Sparrow 2000;Vesk and Westoby 2004), these groups of traits determining fundamental strategies of plant in response to the environment have seldom been analyzed together with the aim of exploring common patterns of trait distributions, largely due to the time-consuming effort of collecting below-ground traits for many species (Weiher et al 1999), but see Wildová et al (2007) and Goldberg et al (2008).…”