The effects of fire frequency and grazing on tallgrass prairie productivity and plant composition are mediated through bud bank demography

Abstract

Periodic fire, grazing, and a variable climate are considered the most important drivers of tallgrass prairie ecosystems, having large impacts on the component species and on ecosystem structure and function. We used long-term experiments at Konza Prairie Biological Station to explore the underlying demographic mechanisms responsible for tallgrass prairie responses to two key ecological drivers: fire and grazing. Our data indicate that belowground bud banks (populations of meristems associated with rhizomes or other perennating organs) mediate tallgrass prairie plant response. Fire and grazing altered rates of belowground bud natality, tiller emergence from the bud bank, and both short-term (fire cycle) and long-term ([15 year) changes in bud bank density. Annual burning increased grass bud banks by 25% and decreased forb bud banks by 125% compared to burning every 4 years. Grazing increased the rate of emergence from the grass bud bank resulting in increased grass stem densities while decreasing grass bud banks compared to ungrazed prairie. By contrast, grazing increased both bud and stem density of forbs in annually burned prairie but grazing had no effect on forb bud or stem density in the 4-year burn frequency treatment. Lastly, the size of the reserve grass bud bank is an excellent predictor of long-term ANPP in tallgrass prairie and also of short-term interannual variation in ANPP associated with fire cycles, supporting our hypothesis that ANPP is strongly regulated by belowground demographic processes.

Do Clonal and Bud Bank Traits Vary in Correspondence with Soil Properties and Resource Acquisition Strategies? Patterns in Alpine Communities in the Scandian Mountains

“…Below-ground perennial bud banks were associated with nutrient poor substrate, and seasonal, above-ground bud banks were more represented in rich substrate sites. Several studies have addressed the question of bud banks in relation to responses of plants to disturbance (Benson et al 2004;Klimešová and Klimeš 2007;Dalgleish and Hartnett 2009), but few have studied the relationships between bud banks and resource availability. In our study, it was not possible to assess whether bud bank densities varied with soil properties, but in agreement with patterns observed in other studies (Dalgleish and Hartnett 2006), we hypothesized that the capacity to sprout determined by the number of buds would be larger under more favorable conditions for growth.…”

Belowground bud banks of tallgrass prairie are insensitive to multi‐year, growing‐season drought

“…Knapp and Smith (2001) developed the meristem limitation hypothesis to explain patterns of variation in ANPP across years, proposing that the availability of meristems may constrain the ability of ANPP to respond to interannual variability in precipitation. Dalgleish and Hartnett attempted to test this hypothesis in tallgrass twice, once by sampling bud bank density across a 700 mm gradient in long-term average annual precipitation (Dalgleish and Hartnett 2006), and again by correlating bud bank density to productivity at Konza Prairie Biological Station (Dalgleish and Hartnett 2009). They demonstrated that grassland bud bank density was positively correlated with ANPP at local and broad spatial scales.…”

Season of fire manipulates bud bank dynamics in northern mixed-grass prairie

“…Survival of species during a fire event usually depends on available vegetative buds to generate new growth (Dalgleish and Hartnett 2009). Belowground buds are well protected from direct effects of fire due to the buffering capacity of soil and soil moisture (Alexander 1982;Bradstock and Auld 1995).…”

“…Although allocation of reproductive effort varies among ecosystems , dependence on bud banks may be expected for perennial grasslands world-wide, unless plants are very short-lived. Since bud banks are the source for future tiller growth, the size of a species' bud bank plays a decisive role in species and plant community response following disturbances, such as fire, grazing, and drought (Benson et al 2004;Dalgleish and Hartnett 2009;Carter et al 2012).…”

“…Tiller recruitment can be meristem limited, when there are not enough buds to completely replace the aboveground tiller population, constraining primary production . Although vegetative production is the primary source of new growth, bud densities can become limited or depleted if aboveground disturbances become too frequent, or occur during susceptible growth periods (Benson et al 2004;Dalgleish and Hartnett 2009). These bud limitations may have consequences for aboveground growth if the timing of disturbance, such as fire and grazing, interferes with critical phenological growth patterns of buds further inhibiting the production or maintenance of belowground buds (Carter et al 2012;Ott and Hartnett 2012).…”