Intraspecific variation in surface water uptake in a perennial desert shrub

Abstract

1. Despite broad recognition that water is a major limiting factor in arid ecosystems, we lack an empirical understanding of how this resource is shared and distributed among neighbouring plants. Intraspecific variability can further contribute to this variation via divergent life-history traits, including root architecture. We investigated these questions in the shrub Artemisia tridentata and hypothesized that the ability to access and utilize surface water varies among subspecies and cytotypes. We used an isotope tracer to quantify below-ground zone of influence inA. tridentata, and tested whether spatial neighbourhood characteristics can alter plant water uptake. We introduced deuterium-enriched water to the soil in plant interspaces in a common garden experiment and measured deuterium composition of plant stems. We then applied spatially explicit models to test for differential water uptake by A. tridentata, including intermingled populations of three subspecies and two ploidy levels.3. The results suggest that lateral root functioning in A. tridentata is associated with intraspecific identity and ploidy level. Subspecies adapted to habitats with deep soils generally had a smaller horizontal reach, and polyploid cytotypes were associated with greater water uptake compared to their diploid variants. We also found that plant crown volume was a weak predictor of water uptake, and that neighbourhood crowding had no discernable effect on water uptake. 4. Intraspecific variation in lateral root functioning can lead to differential patterns of resource acquisition, an essential process in arid ecosystems in the contexts of changing climate and seasonal patterns of precipitation. Altogether, we found that lateral root development and activity are more strongly related to genetic variability within A. tridentata than to plant size. Our study highlights how intraspecific variation in life strategies is linked to mechanisms of resource acquisition. K E Y W O R D SArtemisia tridentata (big sagebrush), below-ground interactions, deuterium tracer, intraspecific variation, lateral roots, resource competition, surface water uptake | 1171 Functional Ecology ZAIATS eT Al.

Intraspecific variation mediates density dependence in a genetically diverse plant species

“…In our arid study system, direct root-to-root interactions and competition for water is one obvious mechanism for suppressed growth in crowded neighborhoods (Krannitzi and Caldwell 1995). Nevertheless, a water isotope tracer experiment in one of our common garden sites did not support direct root competition in surface water uptake (Zaiats et al 2020). In addition to observational studies that confirm our results, developing mechanistic hypotheses that can explain our findings will be an important next step.…”

“…Nevertheless, a water isotope tracer experiment in one of our common garden sites did not support direct root competition in surface water uptake (Zaiats et al. 2020). In addition to observational studies that confirm our results, developing mechanistic hypotheses that can explain our findings will be an important next step.…”

“…Based on empirical and experimental evidence on lateral root zone in big sagebrush (Sturges 1977, Zaiats et al. 2020), we expected no direct effect from neighbors beyond a 4‐m distance, and, therefore, considered plant neighbors in a radius of <4 m from target plants.…”

“…To analyze spatial interactions between the individuals, we calculated a distance matrix, i.e., pairwise distances between all plants in each common garden. Based on empirical and experimental evidence on lateral root zone in big sagebrush (Sturges 1977, Zaiats et al 2020, we expected no direct effect from neighbors beyond a 4-m distance, and, therefore, considered plant neighbors in a radius of <4 m from target plants.…”

Polyploidy but Not Range Size Is Associated With Seed and Seedling Traits That Affect Performance of Pomaderris Species

“…There is a strong association between tolerance of water stress and survival, as well as numerous traits, such as reduction in growth rate and height, total biomass production ( Pérez-Harguindeguy et al, 2016 ), relative amount of investment in root biomass ( Comas et al, 2013 ; Larson and Funk, 2016 ) or trade-offs, such as smaller stature in exchange for higher seed production ( Eliášová and Münzbergová, 2017 ). Experimentally, polyploids have been shown to have greater water uptake than diploids ( Zaiats et al, 2020 ) and to be more resilient in drought conditions, for example, seed production was shown to be over four times higher in drought-stressed polyploids than diploids ( Godfree et al, 2017 ).…”