Summer precipitation limits plant species richness but not overall productivity in a temperate mesic old‐field meadow

Abstract

Question Water availability is a primary regulator of plant productivity and species richness in arid and semi‐arid ecosystems, but its influence in other habitats is much less clear partly because experimental manipulations of water are relatively rare. How important is soil moisture availability relative to other key environmental factors in determining plant species biomass and diversity in temperate mesic grasslands? Location An old‐field meadow in southeastern Ontario, Canada. Methods We established a long‐term factorial field experiment to investigate how variation in soil water (achieved by rainout shelters and water additions), nutrients (NPK fertilizer additions), and above‐ground herbivory (deer fence exclosures), interact as regulators of plant production, species richness, and species composition. Above‐ground biomass for each species was determined in replicate plots (1 m2, n = 10) after five years of treatment applications. Results The rainout shelters reduced community shoot biomass by 35% relative to ambient (control) plots, with no influence of the fertiliser. To our surprise, however, the fertiliser enhanced community biomass in the ambient and water addition plots to a similar extent. Species richness and Shannon diversity were increased by water addition, but reduced by the rainout shelters and by fertilisation. Total species richness across all replicate plots was 60% higher in the water addition treatment, and almost halved in the water‐reduced treatment. In contrast to the above, the exclosures had negligible impacts on these community variables. Conclusions Together, these results suggest that in old‐field meadow grasslands: (a) shoot productivity is primarily limited by soil nutrient supply except under drought conditions when water availability becomes the primary constraint; (b) the two main soil resources for plants — water and nutrients — affect productivity and species richness/composition in fundamentally different ways; and (c) future increases in summer soil aridity and anthropogenic nitrogen deposition may interact to reduce vegetation productivity and diversity in temperate mesic ecosystems.

Late‐season drought exerts more negative effects on plant diversity and cover than early‐season drought through changing soil moisture in a semi‐arid grassland

“…effects on plant cover. The reduced plant cover under late-season drought also agrees with previous reports of decreased plant biomass and cover under summer (Perez-Camacho et al, 2012;Kreyling et al, 2017;Wagg et al, 2017;Serafini et al, 2019) and autumn drought (Nogueira et al, 2017). Decreased plant cover was mainly caused by the lower PF and SS cover (Figure 4b,c).…”

“…Precipitation in the late growing season is critical for maintaining plant growth and biomass allocation. For example, summer drought can suppress plant species richness and plant growth by reducing soil water availability (Wagg et al, 2017; Stampfli et al, 2018; Serafini et al, 2019). Changes in drought timing do not affect all species equally, and can disproportionately affect particular plant species/functional groups due to the differences in life history and functional traits (Nippert & Knapp, 2007; Robertson et al, 2010; Báez et al, 2013).…”

Assessing the roles of nitrogen, biomass, and niche dimensionality as drivers of species loss in grassland communities

“…The csv files and R file have been deposited in Figshare, https://figshare.com/s/d2933788bc55814b47f3 ( 64 ). Previously published data were used for this work ( 8 , 27 , 34 , 43 , 44 , 53 , 65 …”

Precipitation controls seed bank size and its role in alpine meadow community regeneration with increasing altitude

“…However, much research has suggested that increasing precipitation increases species richness (Serafini, Grogan, & Aarssen, 2019;Yang et al, 2011). Our result could be explained by the following: First, soil moisture is relatively abundant during the growing season in alpine meadows on the Tibetan Plateau (Wang, Lan, & Jin, 1993).…”

“…We also found that an increase in MAP indirectly decreased the species richness of the soil seed banks by directly decreasing the species richness of the aboveground plant communities. However, much research has suggested that increasing precipitation increases species richness (Serafini, Grogan, & Aarssen, 2019; Yang et al., 2011). Our result could be explained by the following: First, soil moisture is relatively abundant during the growing season in alpine meadows on the Tibetan Plateau (Wang, Lan, & Jin, 1993).…”