Modelling assimilation rates of 14 temperate arable weed species as a function of the environment and leaf traits

Abstract

Information on the response of assimilation rate to environmental factors is lacking for many less competitive weed species that need to be considered in the context of increasing farm biodiversity. A pot experiment was sown to parameterize gross assimilation rate at light saturation and initial light use efficiency for 14 common UK annual weeds and winter wheat at four leaf temperatures. Field experiments were also sown to measure inter-specific differences in specific leaf area (SLA), leaf nitrogen content and assimilation rates in the field at near-optimum temperatures. A generic relationship describing the response of assimilation rate to temperature and light using SLA and leaf nitrogen content as conversion factors successfully predicted inter-specific differences in assimilation rates in the field. This relationship could be incorporated into weed-crop competition models to predict the productivity and competitive impact of weed mixtures, including species outside the current data set. Assimilation rates at light saturation in the field were determined largely by SLA. This trait was variable between species and within a species across the growing season and needs to be well described in mechanistic competition models to accurately calculate instantaneous assimilation rates

Changes in functional diversity and intraspecific trait variability of weeds in response to crop sequences and climate

“…Our findings of a high contribution of intraspecific variability in SLA corroborate those of previous studies (Jung et al ., ; Albert et al ., ; Perronne et al ., ). This high level of intraspecific trait variability within crop sequence types could potentially be related to weed response to crop canopy closure or to phenological differences between individuals, SLA being sensitive to these two criteria (Storkey, ). Indeed, 98% of weed plants collected in 2011 grown under the winter wheat and winter oilseed rape canopy and showed a shade‐tolerance syndrome, relevant with the high SLA values observed (Storkey, ; Valladares & Niinemets, ).…”

“…This high level of intraspecific trait variability within crop sequence types could potentially be related to weed response to crop canopy closure or to phenological differences between individuals, SLA being sensitive to these two criteria (Storkey, ). Indeed, 98% of weed plants collected in 2011 grown under the winter wheat and winter oilseed rape canopy and showed a shade‐tolerance syndrome, relevant with the high SLA values observed (Storkey, ; Valladares & Niinemets, ). Interestingly, the LDMC, showed a smaller intraspecific variability than SLA, in accordance with previous studies (e.g.…”

“…In contrast, during the 2010–2011 growing season, almost all weed individuals of the three abundant species were under the canopy in both WaO and OaW. These spring‐germinating late‐emerging weeds were therefore characterised by a lower growth and broadly present a shade‐tolerance syndrome (Storkey, ).…”

Ecophysiological characteristics of five weeds and a wheat crop in the Indo‐Gangetic Plains, India

“…As the light intensity increases, however, it becomes more advantageous to have a lower SLA to increase the capacity of individual leaves to absorb light. This will be more important for the taller species and there appears to be a general trade‐off between plant height later in the season and the SLA (Storkey ). This also was observed in the study, as the taller weeds ( C. album and P. minor ) and the crop (wheat) had a low SLA later in the season.…”

Interception of wet deposited atmospheric pollutants by herbaceous vegetation: Data review and modelling

“…(4) and (5), respectively. SLA, L and p can be reasonably assumed constant throughout the vegetative stages, from plant emergence until the point at which leaf area begins to senesce (Storkey, 2004(Storkey, , 2005(Storkey, , 2006Storkey and Cussans, 2007). When plant switches to reproductive stages, the specific area index begins to decline due to both the dying of the foliage and the increase of biomass due to the growth of storage organ.…”