Strong impact of management regimes on rhizome biomass across Central European temperate grasslands

Abstract

Grassland ecosystems account for approximately 40% of terrestrial biomes globally. These communities are characterized by a large allocation to belowground biomass, often exceeding its aboveground counterpart. However, this biomass investment cannot be entirely attributed to the acquisitive function of roots. Grassland plants also allocate to non-acquisitive, stem-derived, belowground organs, such as rhizomes. These organs are responsible for the key plant functions of space occupancy, resprouting after damage, and seasonal rest. However, biomass investment to rhizomes has rarely been studied. Here we gathered community-level aboveground and rhizome biomass data for 52 temperate grasslands in Czech Republic (Central Europe), differing in management intensity. We found that rhizome biomass scaled linearly with aboveground biomass, and more intensive management disproportionally (negatively) affected rhizome biomass. This finding may have important implications for the persistence of temperate grassland plants and their provision of ecosystem services (e.g., soil carbon sequestration, soil stabilization) in relation to changing environments.

Buried but unsafe – defoliation depletes the underground storage organ (USO) of the mesic grassland geophyte,Hypoxis hemerocallidea

“…In that study, below-and above-ground biomass scaled linearly (Ottaviani et al (2021), similar to the positive linear relation between corm size and spring biomass production in H. hemerocallidea (Fig. 3).…”

“…The most marked impact of single season of clipping on H. hemerocallidea was the loss of more than half of its corm mass. Ottaviani et al (2021) also observed far lower (by > 70%) rhizome biomass in temperate grassland mown twice versus grassland mown once annually.…”

“…The effect of growing-season disturbance intensity, frequency, and timing on biomass allocation and growth of geophytic forbs has, unlike for grasses (Briske and Richards, 1995;Ferraro and Oesterheld, 2002), received very little attention. Frequent mowing suppresses above-and below-ground forb biomass (Ottaviani et al, 2021) and forb species diversity (Fynn et al, 2014). Generally, longer periods between defoliations (i.e., low defoliation frequency) reduce the negative effect of defoliation on plants (Ferraro and Oesterheld, 2002) by allowing leaf area to accumulate, roots to grow and stores to be replenished and accumulated (Bayer, 1955;Chapin et al, 1990;Tyler and Borchert, 2003).…”

“…Taken together, results of this trial indicate that growing-season damage to leaves, such as by intensive mowing or by the grazing and/or trampling of livestock can reduce the shortterm resilience, and potentially long-term persistence of, geophytic forbs such as H. hemerocallidea in disturbed mesic grassland. Use of stored reserves for regrowth after repeated, intense disturbance during the growing season depletes USOs while diminished USOs reduce the potential for future shoot growth and reserve replenishment (Ottaviani et al, 2021). This recursive, negative feedback on plant growth may result in progressive rundown of vigour and above-and below-ground plant biomass if grazing and trampling continues unabated (Turner et al, 1993).…”

“…Without regular disturbance by burning during the dormant season or early spring, forb diversity, composition, and underground bud banks will decline (Uys et al, 2004;Fynn et al, 2005;Fidelis et al, 2014;Kirkman et al, 2014;Gordijn et al, 2018). Forb biomass and diversity can also be maintained by infrequent summer mowing (Fynn et al, 2004;Ottaviani et al, 2021). Heavy stocking with concentrated herds of livestock is not a safe alternative to fire or mowing, as advocated by proponents of high-density grazing systems (e.g.…”