Effects of drought on grassland phenology depend on functional types

Abstract

Shifts in flowering phenology are important indicators of climate change. However, the role of precipitation in driving phenology is far less understood compared with other environmental cues, such as temperature.We use a precipitation reduction gradient to test the direction and magnitude of effects on reproductive phenology and reproduction across 11 plant species in a temperate grassland, a moisture-limited ecosystem. Our experiment was conducted in a single, relatively wet year. We examine the effects of precipitation for species, functional types, and the community.Our results provide evidence that reduced precipitation shifts phenology, alters flower and fruit production, and that the magnitude and direction of the responses depend on functional type and species. For example, early-blooming species shift toward earlier flowering, whereas later-blooming species shift toward later flowering. Because of opposing species-level shifts, there is no overall shift in community-level phenology.This study provides experimental evidence that changes in rainfall can drive phenological shifts. Our results additionally highlight the importance of understanding how plant functional types govern responses to changing climate conditions, which is relevant for forecasting phenology and community-level changes. Specifically, the implications of divergent phenological shifts between early-and late-flowering species include resource scarcity for pollinators and seed dispersers and new temporal windows for invasion.

A comparative study of 17 phenological models to predict the start of the growing season

“…Experimental studies (Henry and Molau, 1997;Price and Waser, 1998;Menzel and Fabian, 1999;Botta et al, 2000;Fu et al, 2015;Malyshev, 2020) have shown that air temperature is the main driver of phenological changes in northern temperate and highlatitude regions. In addition, precipitation has an impact on the spring phenology of grasslands (Shen et al, 2018;Castillioni et al, 2022). In the temperate grasslands of China, the effects of daytime and nighttime temperatures on spring phenology are asymmetric, with the monthly average maximum temperature having a greater effect in winter and the monthly average minimum temperature causing a greater effect in spring (Shen et al, 2018).…”

Different responses of functional groups to N addition increased synchrony and shortened community reproductive duration in an alpine meadow

“…Our study found that N addition delayed reproductive phenology and shortened the reproductive period at the community level, which is in contrast to previous reports that N addition significantly prolonged flowering and fruit‐set durations at the species level on the Tibetan Plateau (Shen et al, 2022; Xi et al, 2015). This difference in results may be due to differences in the direction and magnitude of phenological changes within the community, offsetting effects at the species and functional group levels (Castillioni et al, 2022; Meng et al, 2016). We observed that under N addition this community‐level phenological response pattern was attributed to a significant delay in the onset of budding and flowering in early‐flowering sedges and to an advanced end of flowering and fruiting in late‐flowering forbs (Figure 2).…”

“…Any phenological differences in plant functional groups may alter the relative fitness among members of the community, which in turn affects community composition (Castillioni et al, 2022). However, phenological responses to N enrichment and precipitation changes are often at the specific-species level (focused on a few common species) (Liu et al, 2021;Liu, Monaco, et al, 2017;Xia & Wan, 2013), with no clear responses of specific functional groups (Prevey et al, 2019), which exacerbates the difficulty of assessing plant phenological changes under ongoing N enrichment and precipitation changes.…”

“…The existing reports of phenological responses to N enrichment and precipitation changes are mostly based on species‐level observations (Liu et al, 2021; Liu, Monaco, et al, 2017; Smith et al, 2012), and plant phenological response to these factors is complex (Liu, Monaco, et al, 2017) with substantial differences among species (Piao et al, 2019; Wang & Tang, 2019). Differences in phenology between species could depend on different developmental trajectories (Prevey et al, 2019; Suonan et al, 2017) and life forms (Liu et al, 2021; Wang & Tang, 2019) of species in different functional groups (Castillioni et al, 2022). For example, grasses tend to be late‐flowering with increased productivity under N addition treatment (Wang et al, 2022), which delays the transition from the growth to reproductive phase (Cleland et al, 2006).…”

“…In addition, increased productivity after N addition leads to greater evapotranspiration and rapid depletion of soil water content (Yang et al, 2011), which may have a negative effect on plant phenology, especially sedges, since they are shallow‐rooted and thus are more sensitive to drought than deep‐rooted species (Dorji et al, 2013). Any phenological differences in plant functional groups may alter the relative fitness among members of the community, which in turn affects community composition (Castillioni et al, 2022). However, phenological responses to N enrichment and precipitation changes are often at the specific‐species level (focused on a few common species) (Liu et al, 2021; Liu, Monaco, et al, 2017; Xia & Wan, 2013), with no clear responses of specific functional groups (Prevey et al, 2019), which exacerbates the difficulty of assessing plant phenological changes under ongoing N enrichment and precipitation changes.…”