Early snowmelt projected to cause population decline in a subalpine plant

Abstract

How climate change influences the dynamics of plant populations is not well understood, as few plant studies have measured responses of vital rates to climatic variables and modeled the impact on population growth. The present study used 25 y of demographic data to analyze how survival, growth, and fecundity respond to date of spring snowmelt for a subalpine plant. Fecundity was estimated by seed production (over 15 y) and also divided into flower number, fruit set, seeds per fruit, and escape from seed predation. Despite no apparent effects on flower number, plants produced more seeds in years with later snowmelt. Survival and probability of flowering were reduced by early snowmelt in the previous year. Based on demographic models, earlier snowmelt with warming is expected to lead to negative population growth, driven especially by changes in seedling establishment and seed production. These results provide a rare example of how climate change is expected to influence the dynamics of a plant population. They furthermore illustrate the potential for strong population impacts even in the absence of more commonly reported visual signs, such as earlier blooming or reduced floral display in early melting years.climate change | fecundity | population dynamics | seed production | snowmelt A critical challenge in predicting the biological impacts of climate change is to understand how the new environmental conditions will influence decline or growth of a population. Climate change has reduced the extent of snow cover in the Northern Hemisphere since the mid-20th century (e.g., by 11.7% per decade in June) and is projected to further reduce it as the average global temperature rises (1). In mountainous areas of the western United States, the snowpack water equivalent has declined (2), and, in at least some of those regions, the average date of snowmelt in the spring has advanced (3). That earlier snowmelt has been associated with shifts to earlier phenology in a large number of species, including blooming times in flowering plants (4-6). Whereas phenological shifts of plants in response to climate change are well documented (7), rarely is the impact of the phenological shift on reproduction known (8,9). In general, few studies examine associations of climatic variables with the demography of individual plant populations. However, it is ultimately through changes in demographic vital rates that a population will persist or not in the face of environmental change.An understanding of how climate influences plant demography can be separated into two problems: (i) how climate influences a vital rate and (ii) how that vital rate influences population growth. Studies of the climate sensitivity for any vital rate are relatively rare for plant populations (10), but that gap is most striking for the rate of reproduction through seed production, as reproduction is the vital rate that would be impacted by a shift in blooming time. Studies of how climate influences seed production have often focused on long-lived tree species, especi...

Climate warming drives Himalayan alpine plant growth and recruitment dynamics

“…Accordingly, and contrary to our observation from the steppe populations, the recruitment in P. pamirica alpine and subnival plants decreased with the occurrence of snowy weather during the previous year's fall and winter respectively. It is interesting to note that this result is also contrary to the negative consequences of early snowmelt on seeding establishment (survival) and seed production documented in a subalpine species from the Colorado Rocky Mountains (Campbell, 2019).…”

Climate change disrupts local adaptation and favours upslope migration

“…This result is consistent with other studies that document local extinctions in trailing edge populations at the warm edge of the range (Sheth & Angert ). Indeed, montane plants are vulnerable to extreme reductions in range size as climate change causes many sites to become unsuitable (Dullinger et al ; Hülber et al ; Panetta et al ; Campbell ).…”

“…Climate change is decoupling historically correlated conditions, like photoperiod and temperature, but we know little about how climate change shifts fitness landscapes (Etterson & Shaw 2001;Kingsolver et al 2013;Logan et al 2014;Wadgymar et al 2018b). To predict the eco-evolutionary consequences of climate change, we must dissect the extent to which novel climates disrupt long-standing patterns of local adaptation (Wang et al 2010;Wilczek et al 2014) and diminish population growth rates (Panetta et al 2018;Campbell 2019). Here, we address these crucial issues by manipulating the timing of snowmelt and depth of snowpack in temporally and spatially replicated field experiments conducted across an elevational gradient.…”

Plant adaptation to climate change—Where are we?

“…Only experimental manipulations of key climatic factors can test the causal role of these factors in local adaptation (Wadgymar et al, 2017;Anderson & Wadgymar, 2020). For example, in high elevation and high latitude systems, climate change is rapidly reducing winter snowpack and accelerating spring snowmelt (e.g., Fyfe et al, 2017), which can expose plants to spring frost that they would not have experienced historically (Inouye, 2008) and contribute to the decline of native plant species (Campbell, 2019). Boechera stricta (Brassicaceae) is a perennial forb native to the Rocky Mountains, where local populations are adapted to historical snowpack levels (Anderson & Wadgymar, 2020).…”