Competitive interactions between established grasses and woody plant seedlings under elevated CO2 levels are mediated by soil water availability

Manea, Anthony; Leishman, Michelle R.

doi:10.1007/s00442-014-3143-z

Cited by 34 publications

(38 citation statements)

References 50 publications

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“…There is a large body of experimental work that has provided us with a wealth of understanding on the responses of temperate grasslands to changes in precipitation patterns, including extreme drought (Cherwin & Knapp, ; Fay, Carlisle, Knapp, Blair, & Collins, ; Heisler‐White, Blair, Kelly, Harmoney, & Knapp, ; Heisler‐White, Knapp, & Kelly, ; Knapp et al, ; Thomey et al, and others). However, rainfall manipulation studies in savannas are currently very limited (but see February et al, , Manea & Leishman, ). Experimental manipulations in the field can be logistically challenging, particularly in the presence of fire and mega‐herbivores such as elephants, but are needed to better understand how changes in the intensity, duration and timing of droughts influence vegetation responses across diverse savanna types.…”

Section: The Way Aheadmentioning

confidence: 99%

Droughts and the ecological future of tropical savanna vegetation

Sankaran

2019

Journal of Ecology

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Climate change is expected to lead to more frequent, intense and longer droughts in the future, with major implications for ecosystem processes and human livelihoods. The impacts of such droughts are already evident, with vegetation dieback reported from a range of ecosystems, including savannas, in recent years. Most of our insights into the mechanisms governing vegetation drought responses have come from forests and temperate grasslands, while responses of savannas have received less attention. Because the two life forms that dominate savannas—C3 trees and C4 grasses—respond differently to the same environmental controls, savanna responses to droughts can differ from those of forests and grasslands. Drought‐driven mortality of savanna vegetation is not readily predicted by just plant drought‐tolerance traits alone, but is the net outcome of multiple factors, including drought‐avoidance strategies, landscape and neighborhood context, and impacts of past and current stressors including fire, herbivory and inter‐life form competition. Many savannas currently appear to have the capacity to recover from moderate to severe short‐term droughts, although recovery times can be substantial. Factors facilitating recovery include the resprouting ability of vegetation, enhanced flowering and seeding and post‐drought amelioration of herbivory and fire. Future increases in drought severity, length and frequency can interrupt recovery trajectories and lead to compositional shifts, and thus pose substantial threats, particularly to arid and semi‐arid savannas. Synthesis. Our understanding of, and ability to predict, savanna drought responses is currently limited by availability of relevant data, and there is an urgent need for campaigns quantifying drought‐survival traits across diverse savannas. Importantly, these campaigns must move beyond reliance on a limited set of plant functional traits to identifying suites of physiological, morphological, anatomical and structural traits or “syndromes” that encapsulate both avoidance and tolerance strategies. There is also a critical need for a global network of long‐term savanna monitoring sites as these can provide key insights into factors influencing both resistance and resilience of different savannas to droughts. Such efforts, coupled with site‐specific rainfall manipulation experiments that characterize plant trait–drought response relationships, and modelling efforts, will enable a more comprehensive understanding of savanna drought responses.

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Section: The Way Aheadmentioning

confidence: 99%

Droughts and the ecological future of tropical savanna vegetation

Sankaran

2019

Journal of Ecology

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“…Work by Ward and Esler (2010) showed that encroachment by Acacia species is suppressed by water competition from grasses. Furthermore, recent work by Manea and Leishman (2015) showed that, under elevated CO 2 conditions, the growth of C 4 grasses increases greatly, resulting in greater leaf area. This in turn, restricts light and water to tree seedlings, suppressing their growth and offsetting the benefits provided by increased moisture availability resulting from reduced stomatal conductance.…”

Section: Global Driversmentioning

confidence: 99%

Determinants of woody encroachment and cover in African savannas

et al. 2017

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Savanna ecosystems are an integral part of the African landscape and sustain the livelihoods of millions of people. Woody encroachment in savannas is a widespread phenomenon but its causes are widely debated. We review the extensive literature on woody encroachment to help improve understanding of the possible causes and to highlight where and how future scientific efforts to fully understand these causes should be focused. Rainfall is the most important determinant of maximum woody cover across Africa, but fire and herbivory interact to reduce woody cover below the maximum at many locations. We postulate that woody encroachment is most likely driven by CO2 enrichment and propose a two-system conceptual framework, whereby mechanisms of woody encroachment differ depending on whether the savanna is a wet or dry system. In dry savannas, the increased water-use efficiency in plants relaxes precipitation-driven constraints and increases woody growth. In wet savannas, the increase of carbon allocation to tree roots results in faster recovery rates after disturbance and a greater likelihood of reaching sexual maturity. Our proposed framework can be tested using a mixture of experimental and earth observational techniques. At a local level, changes in precipitation, burning regimes or herbivory could be driving woody encroachment, but are unlikely to be the explanation of this continent-wide phenomenon.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-017-3807-6) contains supplementary material, which is available to authorized users.

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“…Although we found that elevated CO 2 levels do not directly favours a particular sprouting type, it may affect their interactions with other co-occurring plant species. For example, woody plant seedling establishment in grasslands in the future will be strongly coupled to the CO 2 response and subsequent competitive effect of the grass species within those systems (Manea and Leishman 2015). Several studies have shown that elevated CO 2 levels stimulate biomass production in grasslands when resources are not limited (Morgan et al 2001;Shaw et al 2002;Dijkstra et al 2010) which may reduce woody plant seedling establishment success (Manea and Leishman 2015).…”

Section: Discussionmentioning

confidence: 99%

Are fire resprouters more carbon limited than non-resprouters? Effects of elevated CO2 on biomass, storage and allocation of woody species

2015

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Resprouting ability is a key functional trait determining plant responses and vegetation dynamics after disturbances such as fire that shape most global biomes. It is likely that rising atmospheric CO 2 concentrations will alter resource allocation patterns in plants which in turn will alter resprouting responses. In this study, we asked: (1) do resprouters have greater allocation to storage than non-resprouters?; (2) if so, do resprouters account for this negative carbon balance by having reduced growth?; and (3) do resprouters have a relatively weaker growth response compared to non-resprouters under elevated CO 2 levels due to their increased allocation to storage? To address these questions, we grew congeneric species-pairs of shrubs common to south-eastern Australia with contrasting resprouting abilities under ambient and elevated CO 2 levels. We found that resprouters in general allocated more resources to storage (root non-structural carbohydrates and biomass) and had less total biomass than non-resprouters. Under elevated CO 2 levels both sprouting types increased biomass production, suggesting they were carbon limited. Surprisingly, the resprouters allocated this additional carbon to biomass rather than to storage. This suggests that although elevated CO 2 levels may not affect resprouting ability directly in resprouters, it may enhance other aspects of persistence such as escapability and bud protection. Furthermore, non-resprouters may also benefit from the additional carbon by being able to set seed more quickly and increase seed production thus enhancing their recruitment after fire. Thus, the relative benefits of elevated CO 2 levels on resprouters versus nonresprouters remain equivocal.

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Competitive interactions between established grasses and woody plant seedlings under elevated CO2 levels are mediated by soil water availability

Cited by 34 publications

References 50 publications

Droughts and the ecological future of tropical savanna vegetation

Droughts and the ecological future of tropical savanna vegetation

Determinants of woody encroachment and cover in African savannas

Are fire resprouters more carbon limited than non-resprouters? Effects of elevated CO2 on biomass, storage and allocation of woody species

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