The effects of age on the demography of a perennial plant depend on interactions with size and environment

Abstract

Age‐dependence of the demographic rates survival, fecundity and individual growth is a fundamental aspect of population biological theory. Knowledge about plant ageing can also be important for conservation and agriculture as it will improve the accuracy of population viability assessments and long‐term performance assessments in perennial crops. Recent studies show age effects on demographic rates for several plant species, yet much remains to be learned about the patterns and mechanisms of plant ageing, particularly about how age effects interact with the environment and with plant size. We collected age‐and‐size‐based demographic data, as well as individual‐based environmental data, for the perennial herb Plantago lanceolata in Denmark over three annual transitions (4 years). We combined frequent field monitoring of carefully mapped individuals with the underused technique of root histology to determine age of herbaceous plants. We used generalized linear mixed effects models to assess how age, soil properties and year influenced survival, growth and reproduction. Our results show no strong evidence of consistent age declines, rather, we found mostly positive effects of age on vital rates. For all vital rates, i.e. survival, growth, flowering and reproductive output, age effects also differed significantly among years. Additionally, we detected an interactive effect of age and size in the growth model. Size, and temporal and spatial environmental variation also affected vital rates independently of age. Synthesis. Our study shows that age‐dependence of demographic rates can depend both on individual size and environmental variation. These results suggest that a consideration of potential age‐interactions may improve the accuracy of comparative studies of ageing and population projections. Moreover, this study shows that much is still unknown about how plant ageing can be affected by the environment.

Plant and herbivorous insect communities respond in complex ways to rainfall manipulation in an oak savanna grassland

“…For example, perennials (e.g. clumping perennial grasses) may vary in productivity due to life span, energy allocation to growth/reproduction and/or to how much biomass accumulates from year to year (Baden et al, 2021; Lundgren & Des Marais, 2020; Mooney et al, 1986), resulting in changes in overall productivity and diversity. Although we did not have enough data to examine time lags, considering lagged effects of precipitation and soil moisture and temporal autocorrelation between years on the plant and herbivore communities community is an important way forward (Sala et al, 2012; Zhu et al, 2014), as is exploring how life histories of plants and herbivores may play into the responses of these communities.…”

Quantifying patch‐specific seed dispersal and local population dynamics to estimate population spread of an endangered plant species

“…Local population dynamics and dispersal are the main mechanistic drivers for spatial population spread (Hastings et al., 2005 ; Kot et al., 1996 ; Schreiber & Beckman, 2020 ; Skellam, 1951 ). As remnant habitats become smaller and more fragmented, considerable variation in local population dynamics and seed dispersal may occur among remnant patches, due to environmental heterogeneity and context dependency of local population dynamics and seed dispersal (Baden et al., 2021 ; Clobert et al., 2012 ). Accordingly, recent studies emphasize the significance of intraspecific variation in seed dispersal (Chen & Giladi, 2020 ; Snell et al., 2019 ) and local population dynamics (Yang et al., 2021 ) for predicting how plants respond to environmental change.…”

Plant diversity effects on plant longevity and their relationships to population stability in experimental grasslands

“…Empirical evidence has shown various survivorship curves (Harper, 1967), and the chance to survive may even rise with age (Baudisch et al., 2013; Lauenroth & Adler, 2008). More recent studies have shown that age may positively and negatively influence the vital rates, that is, survival, growth and fecundity, of plant individuals in herbaceous species (Baden et al., 2021; Baudisch et al., 2013; Roach, 2012). Moreover, plant age has been shown to significantly control biomass allocation in plants, and may thereby affect competitive interactions (Doležal et al., 2020).…”