Root competition: beyond resource depletion

Abstract

Summary1 Root competition is defined as a reduction in the availability of a soil resource to roots that is caused by other roots. Resource availability to competitors can be affected through resource depletion (scramble competition) and by mechanisms that inhibit access of other roots to resources (contest competition, such as allelopathy). 2 It has been proposed that soil heterogeneity can cause size-asymmetric root competition. Support for this hypothesis is limited and contradictory, possibly because resource uptake is affected more by the amount and spatial distribution of resource-acquiring organs, relative to the spatial distribution of resources, than by root system size per se . 3 Root competition intensity between individual plants generally decreases as resource availability (but not necessarily habitat productivity) increases, but the importance of root competition relative to other factors that structure communities may increase with resource availability. 4 Soil organisms play important, and often species-specific, roles in root interactions. 5 The findings that some roots can detect other roots, or inert objects, before they are contacted and can distinguish between self and non-self roots create experimental challenges for those attempting to untangle the effects of self/non-self root recognition, self-inhibition and root segregation or proliferation in response to competition. Recent studies suggesting that root competition may represent a 'tragedy-of-the-commons' may have failed to account for this complexity. 6 Theories about potential effects of root competition on plant diversity (and vice versa) appear to be ahead of the experimental evidence, with only one study documenting different effects of root competition on plant diversity under different levels of resource availability. 7 Roots can interact with their biotic and abiotic environments using a large variety of often species-specific mechanisms, far beyond the traditional view that plants interact mainly through resource depletion. Research on root interactions between exotic invasives and native species holds great promise for a better understanding of the way in which root competition may affect community structure and plant diversity, and may create new insights into coevolution of plants, their competitors and the soil community.

Non-lethal effects of an invasive species in the marine environment: the importance of early life-history stages

“…Competition for space seems unlikely due 387 While we believe that the most likely source of the effect of S. plicata on M. 398 squamiger survival in the field was competition, we must also consider other potential 399 explanations. Allelopathic effects of invasive species on natives have been found in 400 some studies (Schenk 2006;Figueredo et al 2007), and in our study the interaction of 401 the two species might induce the production of waterborne allelopathic metabolites in 402 the introduced species that could reduce both survival and growth of the native. An 403 alternative mechanism for the negative effect of the invasive on the native species in 404 the field is that there are indirect effects via a third organism.…”

Public goods in relation to competition, cooperation, and spite

“…Spatial localization of interactions can also reward greed, selfish behavior, and spite. For example, trees evolve strategies to shade out neighbors (61), or to interfere with neighbors' roots, through mechanisms that would be too costly if their effects were diffused over large areas (62)(63)(64); indeed, it has been suggested that this can lead to a potential tragedy of the commons (63,65). Similarly, plants and microbial organisms produce allelochemics that poison neighbors (66), and selection for these traits depends critically on the fact that the allelochemics will not be diffused over broad areas but will remain close enough to poison the most intense competitors.…”

Controle de plantas daninhas na cultura do milho com gliricídia em consorciação

“…Essa redução foi devido à competição com o milho pelos fatores do crescimento. Abaixo da superfície do solo, as plantas daninhas influenciariam o comportamento do milho, alterando a disponibilidade de nutrientes (Lehoczky & Reisinger, 2003;Kumar et al, 2005) e de água e/ou inibindo o acesso das raízes de milho a esses recursos, por alelopatia (Schenk, 2006). A deficiência d'água, causada pela competição entre raízes, induziria o fechamento dos estômatos, reduzindo a fotossíntese (Silva et al, 2004), e, consequentemente, reduziria também o crescimento de caules, folhas e espigas.…”