Flowering time advances since the 1970s in a sagebrush steppe community: Implications for management and restoration

Abstract

Climate change is widely known to affect plant phenology, but little is known about how these impacts manifest in the widespread sagebrush ecosystem of the Western United States, which supports a number of wildlife species of concern. Shifts in plant phenology can trigger consequences for the plants themselves as well as the communities of consumers that depend upon them. We assembled historical observations of first-flowering dates for 51 species collected in the 1970s and 1980s in a montane sagebrush community in the Greater Yellowstone Ecosystem and compared these to contemporary phenological observations targeting the same species and locations (2016)(2017)(2018)(2019). We also assembled regional climate data (average spring temperature, day of spring snowmelt, and growing degree days) and tested the relationship between first-flowering time and these variables for each species. We observed the largest change in phenology in early-spring flowers, which, as a group, bloomed on average 17 days earlier, and as much as 36 days earlier, in the contemporary data set. Mid-summer flowers bloomed on average 10 days earlier, nonnative species 15 days earlier, and berry-producing shrubs 5 days earlier, while late summer flowering plants did not shift. The greatest correlates of early-spring and mid-summer flowering were average spring temperature and day of snowmelt, which was 21 days earlier, on average, in 2016-2019 relative to the 1973-1978 observations. The shifts in flowering phenology that we observed could indicate developing asynchronies or novel synchronies of these plant resources and wildlife species of conservation concern, including Greater Sage-grouse, whose nesting success is tied to availability of spring forbs; grizzly bears, which rely heavily on berries for their fall diet; and pollinators. This underscores the importance of maintaining a diverse portfolio of native plants in terms of species composition, genetics, phenological responsiveness to climatic cues, and ecological importance to key wildlife and pollinator species.

The influence of climate warming on flowering phenology in relation to historical annual and seasonal temperatures and plant functional traits

“…1 ). This is consistent with other similar studies showing plants flowering 2–6 days earlier ( Primack et al, 2004 ; Miller-Rushing et al, 2006 ; Robbirt et al, 2011 ; Anderson et al, 2012 ; Panchen et al, 2012 ; Calinger, Queenborough & Curtis, 2013 ; Hart et al, 2014 ; Bertin, 2015 ; Davis et al, 2015 ; Park & Schwartz, 2015 ; Bertin et al, 2017 ; Pearson, 2019 ; Williams et al, 2021 ; Bloom, O’Leary & Riginos, 2022 ; Yang et al, 2022 ). The plants in this study are on the low end of this range for earlier flowering with warming.…”

“…This can be mitigated by using a consistent application of flowering time based on the percentage of open flowers, and by using plants with similar durations of flowering ( Davis et al, 2015 ). Finally, the use of the collection date of flowering herbarium specimens as a proxy for actual flowering time has been validated in studies that show no significant difference between specimen collection dates and flowering dates observed in the field in the same year ( Bolmgren & Lönnberg, 2005 ; Miller-Rushing et al, 2006 ; Robbirt et al, 2011 ; Jones & Daehler, 2018 ; Ramirez-Parada, Park & Mazer , 2022 ; Bloom, O’Leary & Riginos, 2022 ).…”

Effects of Annual Weather Variation on Peak Herbaceous Yield Date in Sagebrush Steppe

“…Alteration of plant phenophases likely impacts herbage PYDs and the duration of peak growth. Several recent studies indicate significant shifts in herbaceous plant phenology in sagebrush steppe and semiarid forested rangelands of the western United States (Bloom et al 2022, Brown et al 2022). Collectively, their results point to earlier spring growth initiation and flowering, shorter periods of active growth, and earlier onset as well as longer periods of summer senescence.…”