Dynamic trajectories of growth and nitrogen capture by competing plants

Abstract

Summary• Although dynamic, plant competition is usually estimated as biomass differences at a single, arbitrary time; resource capture is rarely measured. This restricted approach perpetuates uncertainty. To address this problem, we characterized the competitive dynamics of Dactylis glomerata and Plantago lanceolata as continuous trajectories of biomass production and nitrogen (N) capture.• Plants were grown together or in isolation. Biomass and N content were measured at 17 harvests up to 76 d after sowing. Data were fitted to logistic models to derive instantaneous growth and N capture rates.• Plantago lanceolata was initially more competitive in terms of cumulative growth and N capture, but D. glomerata was eventually superior. Neighbours reduced maximum biomass, but influenced both maximum N capture and its rate constant. Timings of maximal instantaneous growth and N capture rates were similar between species when they were isolated, but separated by 16 d when they were competing, corresponding to a temporal convergence in maximum growth and N capture rates in each species. Plants processed N and produced biomass differently when they competed.• Biomass and N capture trajectories demonstrated that competitive outcomes depend crucially on when and how 'competition' is measured. This potentially compromises the interpretation of conventional competition experiments.

Temporal Differentiation of Crop Growth as One of the Drivers of Intercropping Yield Advantage

“…3. The results of this study are in agreement with previous studies on the dynamic processes of above-ground dry weight accumulation 33,35–37 and nutrient uptake 13 . Previous research suggests that crops reach their maximum daily growth rate at the stages of canopy closure and maximum leaf area 45 .…”

“…The logistic growth function using least squares has been used increasingly to fit above-ground dry weight yield data (at least six harvests) from emergence until death or harvest 30,37 . The logistic growth equation comprises:Where M t (kg ha −1 ) is the above-ground dry weight per unit ground area of each crop component grown in a given treatment at ( t ) days after maize emergence during the growing season.…”

“…Characterizing the development of plant–plant interactions during crop growth may help us to understand the potential performance of interspecific interactions 17,34 . Recent studies clearly show that the temporal dynamics of competition can be characterized using the logistic growth model 30,33,35–37 . Here, we employ the logistic growth function to analyze the growth trajectories of the interacting species in four intercropping systems with large variation in crop growth traits.…”

Is ‘peak N’ key to understanding the timing of flowering in annual plants?

“…As the plant grew and N became limiting the concentration of N in new tissue would therefore decline and the plant could use a critical C : N ratio as the trigger to flower. This critical threshold would vary with physiological and environmental factors in exactly the same way as peak N. Intriguingly, it is already known that around half of the A. thaliana transcriptome is regulated by, C, N or C : N interactions (Guti errez et al, 2007), that N signalling influences both growth and senescence (Coruzzi & Bush, 2001;Sugiura & Tateno, 2011;Trinder et al, 2012), and that the onset of flowering relies on assessment of the plant's nutritional status (Castro Mar ın et al, 2011;Wahl et al, 2013). Hence, the molecular machinery to indirectly detect peak N or its onset appears to exist.…”

Variation in phosphorus acquisition efficiency among maize varieties as related to mycorrhizal functioning

“…To understand the balance between resource competition and complementarity between maize varieties, more above-and below-ground sampling may be needed. The method described by Trinder et al (2012) and Qiao et al (2015) may constitute a useful approach.…”