Competitive effect is a linear function of neighbour biomass in experimental populations of Kochia scoparia

Abstract

Summary1 Neighbour size and distance are confounded in most studies of plant growth and competition at the individual level. To investigate the effects of neighbour size on competitive effect, we grew target Kochia scoparia individuals surrounded by six equidistant, even-aged conspecific neighbours. We varied neighbour size by sowing groups of neighbours at different times, and we also varied the sowing time of the target plants to generate variation in both neighbour and target size during the process of competition. We analysed the growth of target plants over two time intervals as a function of their own size and the size of their neighbours at the beginning of the interval. 2 When competition became intense, the relative growth rate of target plants was primarily determined by the size of their neighbours. There was a negative linear relationship between the relative growth rate of target plants over an interval and the biomass of their neighbours at the beginning of the interval. The size of the target plant itself did not make a significant additional contribution to predicting its growth rate. There is a limit on the growth in biomass of the population (target + neighbours), and growth of individuals occurs within this constraint. Local biomass density, which can be primarily determined by neighbouring individuals, can be much more important for an individual's growth than its own size. 3 There was no evidence of size-asymmetric competition. The size of neighbours was the primary determinant of a target plant's relative growth rate, but the effect of a given amount of neighbour biomass was the same for neighbours larger and those smaller than the target plant.

The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad.

“…Intraspecific competition can markedly reduce kochia vegetative and reproductive growth (Franco and Harper 1988;Ramseier and Weiner 2006). Such intraspecific competition is due, in part, to autotoxicity.…”

Effect of Intraspecific Competition and Substrate Type on Terpene Emissions from Some Mediterranean Plant Species

“…As soils are often nutrient-poor in Mediterranean regions, the study of competition is of particular interest. Moreover, plant biomass and growth are especially sensitive to competition (Ramseier and Weiner, 2006;Midoko-Iponga et al, 2005), and these factors may explain some BVOC variability among plants of the same species (Batten et al, 1995). Nevertheless, the effect of this factor remains almost wholly unexplored, as only a single study is available on terpene emission response to competition (Peñuelas and Llusià, 1998).…”

Vegetation Productivity/Stability and Other Possible Ecological Invariant Relationships Demonstrated in a Microplot Multispecies Pasture Sward

“…Besides those morphological or physiological differences there has also been the attempt to see if there are any generalities in the interactions irrespective of the species or processes involved (e.g., a general negative correlation between the mass of a plant and the mean mass of surrounding plants [38,40]. The present study gave emphasis on the latter type of generalities of which individuals or species thrive and which die.…”

“…These include, the near constant final yield of communities in particular environments; the −3/2 thinning rule between density and size principally demonstrated in plant monocultures, for example, [1][2][3][4][5][6][7][8]; the near linear relationship between the logarithm of relative contribution of a species and it's rank order within a community, for example, [9][10][11][12][13][14][15][16][17][18][19][20]; the assembly abundance/rank process and models of why that may be so, for example, [21][22][23][24][25][26]; the inverse relationship between body mass and density in animals and possibly plants, the metabolic rates across diverse taxa scaling to body mass to the 3/4 power, cellular metabolism, and life span to the 1/4 power; mortality to the −1/4 power, for example, [27][28][29][30][31][32][33]; generalities in proximity interactions of individuals in size distributions, growth, and mortality, for example, [34][35][36][37][38][39][40][41]; the positive correlation between the distribution of a species and its local abundance, for example, [42,…”