Tropical forests and the changing earth system

Lewis, Simon L.

doi:10.1098/rstb.2005.1711

Cited by 283 publications

(218 citation statements)

References 115 publications

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“…The consequences of longer droughts and higher temperatures are potentially dramatic. For example, rapid forest collapse as a result of drought could convert the world's tropical forests from a net carbon sink into a large carbon source during this century 8,15 . Predicting how forests will respond to future climate changes hinges on a quantitative understanding of the physiological mechanisms governing drought stress at the species level.…”

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confidence: 99%

Global convergence in the vulnerability of forests to drought

Choat

Jansen

Brodribb

et al. 2012

Nature

2,097

105

2,036

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Shifts in rainfall patterns and increasing temperatures associated with climate change are likely to cause widespread forest decline in regions where droughts are predicted to increase in duration and severity. One primary cause of productivity loss and plant mortality during drought is hydraulic failure. Drought stress creates trapped gas emboli in the water transport system, which reduces the ability of plants to supply water to leaves for photosynthetic gas exchange and can ultimately result in desiccation and mortality. At present we lack a clear picture of how thresholds to hydraulic failure vary across a broad range of species and environments, despite many individual experiments. Here we draw together published and unpublished data on the vulnerability of the transport system to drought-induced embolism for a large number of woody species, with a view to examining the likely consequences of climate change for forest biomes. We show that 70% of 226 forest species from 81 sites worldwide operate with narrow hydraulic safety margins against injurious levels of drought stress and therefore potentially face long-term reductions in productivity and survival if temperature and aridity increase as predicted for many regions across the globe. Safety margins are largely independent of mean annual precipitation, showing that there is global convergence in the vulnerability of forests to drought, with all forest biomes equally vulnerable to hydraulic failure regardless of their current rainfall environment. These findings provide insight into why drought-induced forest decline is occurring not only in arid regions but also in wet forests not normally considered at drought risk

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confidence: 99%

Global convergence in the vulnerability of forests to drought

Choat

Jansen

Brodribb

et al. 2012

Nature

2,097

105

2,036

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“…They are important for recreation and human well being, and provide numerous ecosystem services, and are vital for the maintenance of the majority of biological diversity on Earth (Lacaze, 2000;Dirzo and Raven, 2003;Ozanne et al, 2003;Lewis, 2006). These roles need to be considered when we try to manage forests.…”

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confidence: 99%

Breakdown of the species-area relationship in exotic but not in native forest patches

2008

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Forest specialist species Forestry practice Hungary Generalist speciesHabitat structure a b s t r a c tWe studied the pattern of bird species richness in native and exotic forest patches in Hungary. We hypothetized that species-area relationship will depend on forest naturalness, and on the habitat specialization of bird species. Therefore, we expected strong species-area relationship in native forest patches and forest bird species, and weaker relationship in exotic forest patches containing generalist species. We censused breeding passerine bird communities three times in 13 forest patches with only native tree species, and 14 with only exotic trees in Eastern Hungary in 2003. Although most bird species (92%) of the total of 41 species occurred in both exotic and native forests, the species-area relationship was significant for forest specialist, but not for generalist species in the native forests. No relationship between bird species and area was found for either species group in the forest with exotic tree species. The comparison of native versus exotic forest patches of similar sizes revealed that only large (>100 ha) native forests harbor higher bird species richness than exotic forests for the forest specialist bird species. There is no difference between small and medium forest patches and in richness of generalist species. Thus, the species-area relationship may diminish in archipelago of exotic habitat patches and/or for habitat generalist species; this result supports the warning that the extension of exotic habitats have been significantly contributing to the decline of natural community patterns.

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“…One important observation from a tropical forest network is the increase in biomass quantified over time on fixed-area permanent sample plots, which when scaled globally accounted for ∼60% (1.3 Pg C·y −1 ) of the residual terrestrial carbon sink (6,21). There have been broad discussions on potential causal agents driving this nonsteady-state behavior, and growth fertilization of tropical trees from increasing atmospheric CO 2 has been suggested as a parsimonious explanation for some of these observations (22). However, if patches that are rapidly losing carbon following disturbance demonstrate spatial and temporal clustering, they may be underrepresented in current sampling schemes (19,23).…”

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confidence: 99%

The steady-state mosaic of disturbance and succession across an old-growth Central Amazon forest landscape

Chambers

Negrón‐Juárez

Marra

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

208

238

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Old-growth forest ecosystems comprise a mosaic of patches in different successional stages, with the fraction of the landscape in any particular state relatively constant over large temporal and spatial scales. The size distribution and return frequency of disturbance events, and subsequent recovery processes, determine to a large extent the spatial scale over which this old-growth steady state develops. Here, we characterize this mosaic for a Central Amazon forest by integrating field plot data, remote sensing disturbance probability distribution functions, and individual-based simulation modeling. Results demonstrate that a steady state of patches of varying successional age occurs over a relatively large spatial scale, with important implications for detecting temporal trends on plots that sample a small fraction of the landscape. Long highly significant stochastic runs averaging 1.0 Mg biomass·ha −1 ·y −1 were often punctuated by episodic disturbance events, resulting in a sawtooth time series of hectare-scale tree biomass. To maximize the detection of temporal trends for this Central Amazon site (e.g., driven by CO 2 fertilization), plots larger than 10 ha would provide the greatest sensitivity. A model-based analysis of fractional mortality across all gap sizes demonstrated that 9.1-16.9% of tree mortality was missing from plot-based approaches, underscoring the need to combine plot and remote-sensing methods for estimating net landscape carbon balance. Old-growth tropical forests can exhibit complex large-scale structure driven by disturbance and recovery cycles, with ecosystem and community attributes of hectare-scale plots exhibiting continuous dynamic departures from a steady-state condition.biodiversity | community composition | gap dynamics | NEP NEE NBP A common assumption in old-growth forest studies is that, in the absence of a directional forcing, ecosystem characteristics and tree species composition should exhibit some type of steady-state behavior (1). Thus, plot-based studies in old-growth tropical forests that observe changing tree species composition (2), increased liana abundance (3), faster turnover rates (4), and forest biomass accumulation (5, 6), are viewed as surprising departures from an expected steady-state condition. However, disturbance events can create a landscape with patches of varying successional age, and the extent to which forest plots representatively sample this mosaic remains an open question. An important issue is how to distinguish directional trends driven by a warming climate, or rising atmospheric CO 2 concentration, from smaller-scale stochastic patterns driven by disturbance and recovery cycles (7,8).Over long time periods, the disturbance regime of a forested region creates a shifting steady-state mosaic, represented by patches of different successional ages, with the fraction of the landscape in any particular state remaining relatively constant over time (9,10). In many tropical forests, gaps created by the windthrow of canopy trees is a major mode of disturb...

show abstract

Tropical forests and the changing earth system

Cited by 283 publications

References 115 publications

Global convergence in the vulnerability of forests to drought

Global convergence in the vulnerability of forests to drought

Breakdown of the species-area relationship in exotic but not in native forest patches

The steady-state mosaic of disturbance and succession across an old-growth Central Amazon forest landscape

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