Intraspecific trait variation, functional turnover and trait differences among native and exotic grasses along a precipitation gradient

Abstract

Questions: California's grasslands are heavily invaded by exotic species. Counteracting these invasions depends on understanding the functional differences between native and exotic species and how these shift along environmental gradients. Focusing on grasses, we ask: (a) how native and exotic trait means and intraspecific trait variation (ITV) differ; (b) how the functional composition of grass assemblages shifts with precipitation; and (c) how species shift their functional strategies as precipitation changes.Location: Marin County, California (USA). Methods:In spring 2017, we censused grassland vegetation plots across eight reserves in Marin County that are arrayed along a precipitation gradient. At each plot, we measured traits of grasses, including height, leaf area and specific leaf area (SLA). Results:We found modest differences in functional traits between native and exotic species. Exotic species had larger seeds and higher SLAs, indicating higher reproductive investments and a leaf strategy focused on obtaining rapid returns on investments with relatively short leaf life spans. Native and exotic species did not differ in the ITV for any of the measured traits. Variation in precipitation among sites drove strong turnover in the functional trait composition of grasses, as well as shifts within species. Wetter sites had shorter species with smaller leaf areas, smaller seeds and higher leaf N concentrations. There was also strong intraspecific SLA variation along the precipitation gradient; all species displayed lower SLA values as precipitation increased.Conclusions: Consistent with previous results, native species had more conservative leaf strategies. Grasses that display these conservative strategies tend to be more abundant in dry climates, leading to increasing exotic abundance in wetter climates.However, each species shifted towards more conservative strategies as precipitation increased, suggesting that the factors that drive species turnover and ITV differ. K E Y W O R D Sfunctional trait, grass, height, intraspecific trait variation, leaf area, N mass , Poaceae, seed mass, specific leaf area 634 |

Predicting intraspecific trait variation among California's grasses

“…This contrasts with results for all plants at global and continental scales (Bruelheide et al., 2018; Moles et al., 2009; Šímová et al, 2018), and with grasses at a global scale (Jardine et al., 2020; Sandel et al., 2016) and regional scale (Forrestel et al, 2017). However, it is consistent with a previous study of California grasses (Sandel & Dangremond, 2012) and grasses within the San Francisco Bay Area (Sandel & Low, 2019). Temperature, however, exerted strong positive influences on Height at both inter‐ and intraspecific levels.…”

“…The relationships between mean annual temperature and trait values were largely congruent between and within species. This supports the idea that trait–climate relationships predicted at the inter‐species level can often be transferred to the intra‐species level (Sandel & Low, 2019). For example, warmer regions tended to contain species with higher mean SLA and Height, and within those species, the individuals with relatively high SLA and Height.…”

“…Thus, quantifying trait variation within species across environmental gradients can provide a new test for these predictions. In most cases, it appears that the directions of ITV match those of interspecific functional turnover (Ackerly & Cornwell, 2007; Carlucci et al, 2015; Derroire et al., 2018; Kumordzi et al., 2015; Lepš et al, 2011; Sandel & Low, 2019), although exceptions exist (Kichenin et al., 2013; Lepš et al, 2011).…”

Fitness components and the determinants of fecundity in populations of a native perennial grass (Tridens flavus)

“…Density of flowering T. flavus at each site was estimated by counting tillers with panicles in several 1‐m 2 quadrats in autumn. Because soil water conditions are important to growth and reproduction of perennial grasses (Fitch, Questad, & Bobich, 2019; Münzbergová, Hadincová, Skálová, & Vandvik, 2017; Sandel & Low, 2019), on August 13 and September 16, 2015, volumetric water content (%) of the soil was determined by inserting a 7.6‐cm soil moisture probe (Spectrum Technologies, Plainfield, IL) into 12 haphazardly chosen spots in each site on each date. These data (log 10 ‐transformed) were subjected to ANOVA, with site as the source of variation.…”

Leaf reflectance can surrogate foliar economics better than physiological traits across macrophyte species

“…The issue of disentangling the effects of inter-specific and intra-specific trait variability is at the centre of the current debate (Albert et al, 2012;Osnas et al, 2018), especially for key traits related to the leaf economics spectrum (LES; Wright et al, 2004). Moreover, spatial patterns of trait variability at local scale have been studied only by a limited number of works (Kumordzi et al, 2015;Sandel & Low, 2019) and some light has still to be shed on this level of heterogeneity in plant communities, with implications on productivity and connected processes (Funk et al, 2016).…”