Belowground bud bank response to grazing under severe, short-term drought

Abstract

While the effects of drought and grazing are often studied separately, these disturbances co-occur in grasslands worldwide and interactively influence population, community, and ecosystem processes. The effects of drought and grazing on the belowground bud bank may dictate the trajectory of community recovery because new shoots arise from belowground buds after disturbance in perennial grasslands. We therefore investigated the separate and interactive effects of severe drought and grazing on the belowground bud bank and aboveground vegetation in the tallgrass prairie of northeast Kansas, USA. Contrary to our expectations, we observed changes in community structure and declines in species richness both above and below ground in response to drought and grazing. We also hypothesized that drought would reduce bud bank density of all taxonomic groups, but found that grass bud and shoot densities remained constant across all drought and grazing treatment combinations. While sedge and forb bud and shoot densities were reduced by drought, only sedge bud density declined to a greater extent when grazed under drought conditions. Live rhizome biomass did not vary by treatment and was highly correlated with bud bank density, suggesting that bud demography is tightly linked to the production and senescence of rhizomes. Despite the effects of drought and grazing on aboveground net primary productivity and community structure, our work suggests that grasses stabilize tallgrass prairie plant communities because their rhizomes and associated buds persist through co-occurring disturbances.

Summer drought decreases Leymus chinensis productivity through constraining the bud, tiller and shoot production

“…Thus, for L. chinensis, the decrease in belowground bud bank density is caused by lower bud production per plant due to a reduction in both the number and length of rhizomes produced per plant. This drought induced decrease in buds, differs from grass species in wetter environment like tall prairie grassland, where drought induced increased bud mortality (VanderWeide & Hartnett, 2015). Leymus chinensis is a drought-adapted species common in semi-arid regions, where droughts occur frequently, whereas drought only occurs infrequently in wetter years.…”

“…In general, precipitation affects current year's productivity directly and indirectly by influencing bud bank size, stolon growth and death, and influencing future year's productivity through tiller retention and resource storage into buds (Reichmann & Sala, 2014). Particularly, in dry years, drought-induced bud number reductions are caused by either a lower rhizome density (VanderWeide & Hartnett, 2015) or an increase in current year bud death rate (Flemmer, Busso, & Fernandez, 2002). In addition, the bud bank contains several different bud types (Ott & Hartnett, 2012;Zhang et al, 2009) that have a different function (Wang et al, 2010).…”

Belowground plant functional ecology: Towards an integrated perspective

“…This basic functional scheme of shoots and roots is preserved in trees and annual plants (Figure a,b). However, for perennial herbs and shrubs, belowground is also the place where plants are safe from disturbances (e.g., fire, mowing, grazing; Dalgleish & Hartnett, ; Klimešová & Klimeš, ; Pausas, Lamont, Paula, Appezzato‐da‐Glória, & Fidelis, ) or climatic adversities (e.g., drought, frost; Raunkiaer, ; VanderWeide & Hartnett, )—see Figure c,d. In this safe belowground space, plants can accumulate carbohydrates and reserve buds that could be then used for resprouting, that is, to restore the aboveground biomass following its removal (Clarke et al., ; Klimešová & Klimeš, ).…”

“…This basic functional scheme of shoots and roots is preserved in trees and annual plants (Figure 1a,b). However, for perennial herbs and shrubs, belowground is also the place where plants are safe from disturbances (e.g., fire, mowing, grazing; Dalgleish & Hartnett, 2009;Klimešová & Klimeš, 2007;Pausas, Lamont, Paula, Appezzatoda-Glória, & Fidelis, 2018) or climatic adversities (e.g., drought, frost; Raunkiaer, 1934;VanderWeide & Hartnett, 2015)-see Figure 1c,d.…”

The unseen invaders: introduced earthworms as drivers of change in plant communities in North American forests (a meta‐analysis)

“…This finding suggests that earthworm invasion acts as a significant ecological filter that appears to drive strong changes in plant community composition. The long-term effects of earthworm invasion on abiotic conditions in the forest understory, for example, rapid soil nutrient release and subsequent depletion, decreased soil water content, and increased surface runoff (Hale et al, 2005;Eisenhauer et al, 2012;Resner et al, 2015), may confer a competitive advantage to graminoids, particularly those with greater drought tolerance (Craine et al, 2013) and persistent bud banks (Bond, 2008;VanderWeide & Hartnett, 2015). Certain graminoids, such as those with greater tolerance of root herbivory (Cameron et al, 2014;Gilbert et al, 2014) or those without obligate mycorrhizal associations (e.g., Carex pensylvanica; Holdsworth et al, 2007a), also may respond positively to earthworm invasion.…”