Drought has inconsistent effects on seed trait composition despite their strong association with ecosystem drought sensitivity

Abstract

1. Seeds provide the basis of genetic diversity in perennial grassland communities and their traits may influence ecosystem resistance to extreme drought. However, we know little about how drought effects the community functional composition of seed traits and the corresponding implications for ecosystem resistance to drought.2. We experimentally removed 66% of growing season precipitation for 4 years across five arid and semi-arid grasslands in northern China and assessed how this multi-year drought impacted community-weighted means (CWMs) of seed traits, seed trait functional diversity and above-ground net primary productivity (ANPP).3. Experimental drought had limited effects on CWM traits and the few effects that did occur varied by site and year. For three separate sites, and in different years, drought reduced seed length and phosphorus content but increased both seed and seed-coat thickness. Additionally, drought led to increased seed functional evenness, divergence, dispersion and richness, but only in some sites, and mostly in later years following cumulative effects of water limitation. However, we observed a strong negative relationship between drought-induced reductions in ANPP and CWMs of seed-coat thickness, indicating that a high abundance of dominant species with thick seeds may increase ecosystem resistance to drought. Seed trait functional diversity was not significantly predictive of ANPP, providing little evidence for a diversity effect.

Infrastructure to factorially manipulate the mean and variance of precipitation in the field

“…Drought can also increase the water use efficiency of subdominant C 3 plant species as evidenced by enriched δ 13 C isotopes (Fain, 2022). Third, an extreme drought in our grasslands also altered community‐weighted mean plant and seed traits, including height, leaf carbon content (Luo et al, 2021), and seed coat thickness (Luo et al, 2022), and extreme drought increased the collective plant community's drought‐escape strategies, rather than drought‐resistance strategies (Griffin‐Nolan et al, 2019). Such changes in plant species‐level and community‐level traits could alter water relations, creating legacy effects on soil moisture in subsequent years.…”

High below‐ground bud abundance increases ecosystem recovery from drought across arid and semiarid grasslands

“…Therefore, any shift in community‐weighted traits indicates variation in species composition and/or relative abundance rather than intraspecific trait variability (i.e. variation in traits within species due to phenotypic or genotypic diversity) (Klimešová, Mudrák, et al, 2021; Klimešová, Ottaviani, et al, 2021; Luo et al, 2022).…”

“…under ambient conditions), as has been done in similar studies (e.g. Griffin-Nolan et al, 2019;Klimešová, Mudrák, et al, 2021;Luo et al, 2022;Sandel et al, 2010). This method was used to prevent destructive measurements, which could hinder the regeneration of plants in drought plots.…”

“…variation in traits within species due to phenotypic or genotypic diversity) (Klimešová, Mudrák, et al, 2021;Luo et al, 2022).…”

Interspecific and intraspecific trait variability differentially affect community‐weighted trait responses to and recovery from long‐term drought

“…response‐effect trait framework; Lavorel & Garnier, 2002, Suding et al, 2008). Plant traits can be linked to ecosystem processes, including net primary productivity, biogeochemical cycling and decomposition in terrestrial ecosystems (Griffin‐Nolan et al, 2019; Luo, Griffin‐Nolan, Felton, et al, 2022; Reichstein et al, 2014; Wilcox et al, 2021). For example, community‐weighted plant height was positivity correlated with above‐ground net primary productivity (ANPP) during drought in a semi‐arid grassland (Luo, Griffin‐Nolan, et al, 2021).…”