Root responses to neighbors depend on neighbor identity and resource distribution

Abstract

Purpose: In a complex soil environment, competitive and environmental factors will interact with individual traits to in uence a plant's root growth patterns and ability to compete for resources. Here, we examine how root growth of a focal plant, Plantago lanceolata L., responds to resource heterogeneity and to presence of two neighbor species, Centaurea jacea L.and Poa pratensis L. Methods: A full factorial experiment tested the effects of nutrient heterogeneity, neighbors, and their interaction on root responses of Plantago. Roots in shared quadrants of a pot were harvested and quanti ed by qPCR for plants grown alone or with a neighbor, in patchy or even soil. The effects of experimental treatments on Plantago root mass distribution were tested with two-way ANOVA.Results: When soil resources were evenly distributed, Plantago individuals increased root allocation to soil shared with a Centaurea neighbor but not a Poa neighbor. When soil resources were patchy, Plantago responded more strongly to Poa than to Centuarea, and placed more roots in the high-resource patch.Conclusions: These results demonstrate that plants can respond differently to neighbors depending on species and that integrating multiple cues results in non-additive effects on root behavior.

Effects of Soil Heterogeneity and Species on Plant Interactions

“…Plant responses depend on neighbor identity and resource distribution (Mommer et al, 2012;Garlick et al, 2021).…”

“…Plant interactions play an important role in shaping the composition and structure of plant populations and communities (Baer et al, 2003;Rajaniemi et al, 2009;Wassmuth et al, 2009;Cahill and McNickle, 2011;Houseman, 2014;Zhang et al, 2020). Numerous studies have explored plant interactions (Robinson et al, 1999;O'Brien et al, 2007;Allesina and Levine, 2011;Roiloa et al, 2014;Ravenek et al, 2016;Fichtner et al, 2018;Garlick et al, 2021), yet, several factors impede researchers to exactly quantify such interactions. For example, it is difficult to connect the cause and effect of plant interactions in natural communities with multiple species growing together, where many other factors such as climate change, disturbance, and natural heterogeneity may affect the results (Ravenek et al, 2016;Liu et al, 2019).…”

“…Plants growing in a population or a community interact with each other (Chesson, 2000;Levine et al, 2017;Garlick et al, 2021). However, how to quantify such interactions is a hot topic in ecology.…”

“…RCI was applied to quantify plant interactions, where RCI was calculated as a direct ratio of monoculture and mixture performance, and positive (or negative) values simply indicated that a plant individual experiences stronger (or weaker) competition in mixtures compared with growing alone (Weigelt and Jolliffe, 2003). Specifically, we put forward three hypotheses: (i) RCI is expected to increase with increasing soil heterogeneity, where higher soil heterogeneity could reduce plant interactions due to an increase in the available resources at higher soil heterogeneity levels (Levine et al, 2017;Liu et al, 2017b); (ii) Such patterns may be modified by plant species identity since responses to soil heterogeneity can be modified via strategies or traits such as plasticity (Hodge, 2004;Craine and Dybzinski, 2013); (iii) Soil heterogeneity and species are assumed to jointly affect RCI since plant responses to soil resources depend on their neighbor identity and the distribution pattern of soil resources (Mommer et al, 2012;Garlick et al, 2021).…”

Quantifying effects on tree growth rates of symmetric and asymmetric inter-tree competition in even-aged, monoculture Eucalyptus pilularis forests

“…These have included spatial heterogeneity of resources in the soil or of litter layers (Casper and Jackson. 1997;Rajaniemi 2003;Hodge 2006;Forrester 2019;Garlick et al 2021), conditions of low water availability (Forrester 2019;Forrester et al 2022), development of ectomycorrhizal systems on roots (Franklin et al 2014) and of inter-specific effects in mixed species populations (Putz and Canham 1992;van Noordwijk et al 1996;Forrester 2019;Boyden et al 2012;Forrester et al 2022). Higher efficiency of water uptake by become difficult to appreciate.…”