Persistent decadal differences in plant communities assembled under contrasting climate conditions

Abstract

Plant community assembly outcomes can be contingent upon establishment year (year effects) due to variations in the environment. Stochastic events such as interannual variability in climate, particularly in the first year of community assembly, contribute to unpredictable community outcomes over the short term, but less is known about whether year effects produce transient or persistent states on a decadal timescale. To test for short-term (5-year) and persistent (decadal) effects of establishment year climate on community assembly outcomes, we restored prairie in an agricultural field using the same methods in four different years (2010, 2012, 2014, and 2016) that captured a wide range of initial (planting) year climate conditions. Species composition was measured for 5 years in all four restored prairies and for 9 and 11 years in the two oldest restored prairies established under average precipitation and extreme drought conditions. The composition of the four assembled communities showed large and significant differences in the first year of restoration, followed by dynamic change over time along a similar trajectory due to a temporary flush of annual volunteer species.Sown perennial species eventually came to dominate all communities, but communities remained distinct from each other in year five. Precipitation in June and July of the establishment year explained short-term coarse community metrics (i.e., species richness and grass/forb cover), with wet establishment years resulting in a higher cover of grasses and dry establishment years resulting in a higher cover of forbs in restored communities. Short-term differences in community composition, species richness, and grass/forb cover in restorations established under average precipitation and drought conditions persisted for 9-11 years, with low interannual variability in the composition of each prairie over the long term, indicating persistently different states on a decadal timescale. Thus, year effects resulting from stochastic variation in climate can have decadal effects on community assembly outcomes.

Climate before and after planting drive divergent outcomes ten years after restoration of a wheat field to grassland

“…In this study and others, the responses of particular species to abiotic conditions corresponded broadly to functional groups (Fig. 3) (Manning and Baer, 2018;Eckhoff et al, 2023). This suggests that in addition to following previously outlined recommendations to have high diversity in seed mixtures (Barr, Jonas and Paschke, 2017), land managers may be able to tailor species mixes according to observed antecedent conditions along with near-term forcasts while planning restoration actions, perhaps using a recruitment niche framework (Larson et al 2023).…”

“…Seed germination and seedling establishment are especially sensitive to short-term fluctuations in climatic conditions (Larson et al, 2015;Shriver et al, 2018), even if mean annual temperature or precipitation is suitable for a given species' climatic niche. The inter-and intra-annual timing of moisture availability and heat stress within the year of a restoration treatment is of tantamount importance for determining germination, seed establishment, and community assembly (Young et al, 2015;O'Connor et al, 2020;Werner et al, 2020) compositional differences due to climate variability can have decadal legacies (Eckhoff et al, 2023).…”

Soil climate underpins year effects driving divergent outcomes in semi-arid cropland to grassland restoration

“…In this study and others, the responses of particular species to abiotic conditions corresponded broadly to functional groups (Fig. 3) (Manning and Baer, 2018;Eckhoff et al, 2023). This suggests that in addition to following previously outlined recommendations to have high diversity in seed mixtures (Barr, Jonas and Paschke, 2017), land managers may be able to tailor species mixes according to observed antecedent conditions along with near-term forecasts while planning restoration actions, perhaps using a recruitment niche framework (Larson et al, 2023).…”

Fit by design: Developing seed–substrate combinations to adapt dike grasslands to microclimatic variation

“…After 4 years, the vegetation was still distinct from positive references and seed mixtures. In the south exposition, the plots were rather similar to the negative reference of dry ruderal vegetation typical of grassland restoration when perennial species are still developing to become dominant (Eckhoff et al, 2023). The gap between goal and restoration outcome was also shown for other sowing experiments or restorations (Engst et al, 2016; Kaulfuß et al, 2022; Mitchley et al, 2012) or for dike vegetation compared with semi‐natural reference grassland (Bátori et al, 2016).…”

“…After 4 years, the vegetation was still distinct from positive references and seed mixtures. In the south exposition, the plots were rather similar to the negative reference of dry ruderal vegetation typical of grassland restoration when perennial species are still developing to become dominant (Eckhoff et al, 2023).…”