Unearthing belowground bud banks in fire‐prone ecosystems

Abstract

Despite long-time awareness of the importance of the location of buds in plant biology, research on belowground bud banks has been scant. Terms such as lignotuber, xylopodium and sobole, all referring to belowground bud-bearing structures, are used inconsistently in the literature. Because soil efficiently insulates meristems from the heat of fire, concealing buds below ground provides fitness benefits in fire-prone ecosystems. Thus, in these ecosystems, there is a remarkable diversity of bud-bearing structures. There are at least six locations where belowground buds are stored: roots, root crown, rhizomes, woody burls, fleshy swellings and belowground caudexes. These support many morphologically distinct organs. Given their history and function, these organs may be divided into three groups: those that originated in the early history of plants and that currently are widespread (bud-bearing roots and root crowns); those that also originated early and have spread mainly among ferns and monocots (nonwoody rhizomes and a wide range of fleshy underground swellings); and those that originated later in history and are strictly tied to fire-prone ecosystems (woody rhizomes, lignotubers and xylopodia). Recognizing the diversity of belowground bud banks is the starting point for understanding the many evolutionary pathways available for responding to severe recurrent disturbances.

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands

“…). Many, if not most, tropical old‐growth grassland plants have evolved to endure disturbances that remove aboveground biomass, including recurrent fires and herbivory (Bond & Keeley, ; Veldman et al ., ; Bond, ; Pausas, ) by investing in underground storage organs (USOs; Simon et al ., ; Maurin et al ., ; Pausas et al ., ) and bud banks (near or below the soil surface) that allow resprouting after loss of aboveground biomass (Coutinho, ; Brewer & Platt, , b ; Appezzato‐da‐Glória et al ., ; Fidelis, Lyra & Pivello, ).…”

“…USOs are extremely difficult to uproot and transfer without damage (Zaloumis, ; Le Stradic et al ., ) and can require long periods of time to develop (Veldman et al ., ). Given the importance of bud banks to the regeneration capacity of tropical grasslands (Fidelis et al ., ; Pausas et al ., ), determining if and how USOs may be transplanted is a key research need. Among human land uses that severely affect tropical grasslands, surface mining (including open‐pit mining) has the most profound local ecological impact (Sonter et al ., ).…”

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, ).…”

“…Similar to carbohydrates storage, buds can be stored belowground where they are protected against disturbances. Plants generally store and accumulate buds on stem‐derived organs (Klimešová & Klimeš, ; Pausas et al., ), sometimes also on root‐derived organs (Bartušková, Malíková, & Klimešová, ). Positioning of buds, therefore, does influence plant ability to cope with different disturbance severities (Bartušková & Klimešová, ; Malíková, Šmilauer, & Klimešová, ).…”

Beyond the species pool: modification of species dispersal, establishment, and assembly by habitat restoration

“…But also in ancient grassland habitats regularly disturbed by fire, such as old‐growth campo rupestre grasslands, the seed bank was found to be insufficient for community recovery after severe anthropogenic disturbance (Le Stradic et al ). Obviously the bud bank is more important in regularly burnt old‐growth grasslands than the seed bank (Fidelis et al ; Pausas et al ) and resprouting seems to be the major way of plant regeneration (see also Kiss et al ).…”