Climate fluctuations drive the recruitment and growth of temperate grassland plants

Abstract

Recent climate warming is associated with the increasing magnitude and frequency of extreme events, including heatwaves and drought periods worldwide. Such events can have major effects on the species composition of plant communities, hence on biodiversity and ecosystem functioning. Here we studied responses of Central European dry grassland plants to fluctuating temperature and precipitation over the last thirty years with monthly temporal resolution. We assessed the seasonal and annual dynamics of plant recruitment and growth based on the analysis of annual growth rings from the root collar. Although most studies so far applied such methods to trees and shrubs, we focused on typical grassland plants, two forbs and two chamaephytes. We related the recruitment and annual growth to monthly and annual precipitation, temperature and aridity between 1991 and 2019. We revealed species-specific responses, namely the (i) recruitment of deep-rooted, heavy-seeded species was positively affected by precipitation in both late winter-early spring and summer, whereas recruitment of shallow-rooted, light-seeded species was weakly influenced by climate fluctuations; (ii) growth of shallow-rooted species was more adversely affected by high summer temperature and drought than the growth of deep-rooted species. The population age structure of all the studied species was affected by the climate of the past decades. Most individuals established in the wet period of the 2000s, fewer in the precipitation-poorer 1990s, and the establishment was considerably reduced in the dry and warm period of the 2010s. Our findings indicate that the change towards warmer and drier climate has a profound effect even on drought-adapted ecosystems such as temperate dry grasslands. However, plant responses to various climatic extremes are species-specific, depending on their characteristics, such as life form or rooting depth. Consequently, the ongoing and anticipated climate warming will likely result in complex changes in species composition and other ecosystem properties of temperate grasslands.

Sticking around: plant persistence strategies on edaphic islands

“…For example, the chamaephytes Helianthemum and Thymus or the forbs Carlina, Centaurea, Knautia and Scleranthus were distinguished by well-differentiated strategies to successfully persist on the edaphic islands ( Figure 2b ). This may be due to differences in rooting depth and regenerative strategies (Rosbakh & Poschlod, 2021) and not to plant longevity (see also Doležal et al, 2021). Such a complex and species-specific set of responses may indicate that the focal non-clonal species are likely to be well-adapted to cope with (and not limited by) the distinct ecological and biogeographical conditions provided by the spatially-confined temperate dry grasslands.…”

“…These findings challenge the notion that plants inhabiting harsher environments are slower in their growth and longer-lived (Nobis & Schweingruber, 2013). This may suggest that Carlina and Helianthemum have developed at the intraspecific level unique adaptive strategies to successfully persist in the distinct conditions provided by the edaphic islands, which do not necessarily constrain their growth (Doležal et al, 2021). Non-clonal plants also exhibited a greater ability to transport water through larger vessels in deeper, more variable and sandier soils.…”

“…Yet, this may be explained by an adaptive hydraulic safety-efficiency functional trade-off (Drake et al, 2015). Larger vessels may imply quicker growth (as found for Helianthemum , probably facilitated by its deep rooting ability; Doležal et al, 2021) and higher evapotranspiration, but may also increase the risk of embolism associated with cold and arid spells typical of the highly-seasonal temperate dry grasslands.…”

“…Their average area is ∼2,912 m 2 (min = 361 m 2 , max = 14,115 m 2 ). The regional macroclimate is temperate (mean annual temperature: 6.5–8°C, annual precipitation: 500–550 mm; Tolasz, 2007), characterized by a marked temperature and precipitation seasonality (Doležal et al, 2021). The vegetation growing on these gently dome- shaped outcrops (maximum elevation ∼5-10 m compared to the surroundings) is acidophilous dry grassland.…”

Sticking around: plant persistence strategies on edaphic islands

“…For example, the chamaephytes Helianthemum andThymus or the forbs Carlina , Centaurea ,Knautia and Scleranthus were distinguished by well-differentiated strategies to successfully persist on the edaphic islands (Figure 2b). This may be due to differences in rooting depth and regenerative strategies (Rosbakh & Poschlod, 2021) and not to plant longevity (see also Doležal et al, 2021). Such a complex and species-specific set of responses may indicate that the focal non-clonal species are likely to be well-adapted to cope with (and not limited by) the distinct ecological and biogeographical conditions provided by the spatially-confined temperate dry grasslands.…”