Hydroclimatic adaptation critical to the resilience of tropical forests

• Published in: Global change biology Vol. 28; no. 9; pp. 2930 - 2939
• Main Authors: Singh, Chandrakant, van der Ent, Ruud, Wang‐Erlandsson, Lan, Fetzer, Ingo
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-05-2022; John Wiley and Sons Inc
• Subjects: Acclimatization; Adaptation; Adaptation, Physiological; alternative stable states; Dynamic stability; Dynamic structural analysis; Dynamics; Ecology and Evolution; Ecosystem; ecosystem change; Ecosystems; ekologi och evolution; Forest ecosystems; forest-savanna transition; Forests; Frequency dependence; Frequency distribution; hydrologi; Hydrology; Perturbation; Rainforests; Remote sensing; Resilience; Root zone; Savannahs; spatio-temporal approach; Storage capacity; Storage conditions; subsoil adaptation; Subsoils; Substitutes; Terrestrial ecosystems; Terrestrial environments; transient state; Trees; Tropical climate; Tropical forests; transient state; ecosystem change; remote sensing; subsoil adaptation; alternative stable states; spatio-temporal approach; forest-savanna transition
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/gcb.16115

Forest and savanna ecosystems naturally exist as alternative stable states. The maximum capacity of these ecosystems to absorb perturbations without transitioning to the other alternative stable state is referred to as ‘resilience’. Previous studies have determined the resilience of terrestrial ecosystems to hydroclimatic changes predominantly based on space‐for‐time substitution. This substitution assumes that the contemporary spatial frequency distribution of ecosystems’ tree cover structure holds across time. However, this assumption is problematic since ecosystem adaptation over time is ignored. Here we empirically study tropical forests’ stability and hydroclimatic adaptation dynamics by examining remotely sensed tree cover change (ΔTC; aboveground ecosystem structural change) and root zone storage capacity (Sr; buffer capacity towards water‐stress) over the last two decades. We find that ecosystems at high (>75%) and low (<10%) tree cover adapt by instigating considerable subsoil investment, and therefore experience limited ΔTC—signifying stability. In contrast, unstable ecosystems at intermediate (30%–60%) tree cover are unable to exploit the same level of adaptation as stable ecosystems, thus showing considerable ΔTC. Ignoring this adaptive mechanism can underestimate the resilience of the forest ecosystems, which we find is largely underestimated in the case of the Congo rainforests. The results from this study emphasise the importance of the ecosystem's temporal dynamics and adaptation in inferring and assessing the risk of forest‐savannah transitions under rapid hydroclimatic change.
With the availability of longer time series of remotely sensed datasets, our study tries to incorporate far overlooked temporal support in determining the transient ecosystems’ state and resilience across time. Here, we use the last 20 years of remote sensing data to provide empirical (spatio‐temporal) evidence to alternative stable states and the influence of hydroclimatic adaptation dynamics in maintaining these transient states. Our results also show that ignoring this adaptive capacity can largely underestimate the resilience of the forest ecosystems. Moreover, spatially explicit mapping of these transient states can help strengthen conservation and management efforts.