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FEATURE

One of the many plant species in African tropical grasslands – Protea Grassland expert Paulina Meller shows an ‘underground tree’, Diospyros
angolensis var angolensis chamaethamnus, in the Bicuar National Park, Angola. Underground trees
are woody species that grow in grasslands exposed to fire and frost, and
keep their trunks and branches protected below ground. They flower and
fruit at ground level.

after ploughing/tillage in different the initiation of a disturbance regime for to have at a given site, but also functional
African grasslands. recovery feedbacks. To push back woody diversity, soil structure and the below-
3. Working with biodiversity organisations encroachment, land managers have ground component. This will allow the
and policy makers to develop incentives sometimes resorted to cutting, herbicides, system to recover from an extreme event,
for “avoided conversion” of grassland, ploughing up trees and extreme fires. as the presence of a viable bud bank and
similar to the “avoided deforestation” underground storage organs ensures
incentives that are part of REDD In the case of invasive grasses, they can the resilience of the system. In spite of
(reducing emissions from deforestation maintain disturbance regimes which the difficulties climate change presents
and forest degradation). are not conducive to the below-ground to restoring old-growth grasslands, the
complexity of old-growth systems. There authors expect that prioritising below-
Buisson and her colleagues propose the can, under certain circumstances, be a ground complexity and functional
following three considerations to guide dominance in the seed bank, making diversity should enable resilience while
restoration interventions: it difficult to re-establish long-lived maintaining the character and services
natives. Seed enhancement technology that embody these systems.
Embrace and manage and ordering the reintroduction of
disturbance-vegetation feedbacks plants provide a strategy to influence Outlook
Many grasslands globally co-evolved species dominance in the early stages of Restoration science and practice are
with fire and grazing animals and have restoration. critical in combatting the loss of old-
been structured by feedbacks among growth grasslands and the loss of
disturbance, vegetation and below- Old-growth grassland species biodiversity. Tree planting in grasslands as
ground soil development. Re-establishing How does one speed up species turnover a way of restoration, and the conversion of
broken feedbacks in cases where fire has to restore an old-growth state? Grasslands arable land to agriculture, are irreversible
been suppressed or grazer communities are often restored by sowing seeds. actions which ignore the below-ground,
have become depauperate can have rapid However, seeding fast-growing species soil-locked carbon storage in old-growth
and beneficial impacts on biodiversity may impede long-term success due to a grasslands.
and ecosystem services. Sometimes novel lack of resilience and by excluding longer-
interventions are required to re-initiate lived species from restoration. Once The authors warn of the hard road ahead,
feedbacks, and the authors give examples below-ground structures are gone, not littered with challenges, but are confident
where fire has been used as a tool to enough information is available on how to that viewing grassland restoration
recreate grazing habitat, and livestock restore them, emphasising the importance as assembly towards old-growth
grazing is managed to foster habitat for of preserving them in the first place. There characteristics with unique biota and
other large mammalian herbivores. As has been some success in broadening below-ground complexity “will enable us
the system recovers, interventions can be types of species through topsoil and to achieve ambitious restoration goals for
amended. vegetative transfer. Techniques to speed Earth’s grassy ecosystems”.
up the establishment of bud banks are
Breaking the cycle of invasion promising, but are in their infancy. In conclusion, they “urge conservation
Woody encroachment or exotic herbaceous initiatives to safeguard against the
species invasion can threaten grassland Climate change conversion of old-growth grasslands
integrity. Once the grassy understory has Climate controls the distribution of for tree planting or tillage agriculture,
been knocked back to such an extent that grasslands, and climate change may to maintain our ancient biodiverse
it cannot carry a fire or support grazers, require a shift in restoration trajectories grasslands with appropriate disturbance
woody encroachment becomes difficult depending on species best able to regimes, and to emphasise the long-term
to reverse. This requires replanting of tolerate future conditions. Decisions may restoration of grasslands in efforts to
herbaceous vegetation, together with be influenced not only by which species restore Earth’s biodiversity”. n

Landscape SA • Issue 118 2022 21