Global Ecology and Biogeography最新文献

Aim

Current observations of global tree mortality events associated with drought raise concerns about climate change risks to forests' dynamics and function. It is unclear which forests are more susceptible to pulses of mortality under further changing climates. We examined whether tree mortality related to hotter droughts is predominantly occurring in edge or core populations in niche space and assessed whether mortality patterns are consistent with species' drought tolerances.

Location: Global.

Time Period: 1970–2020.

Major Taxa Studied: Angiosperm and gymnosperm trees.

Methods

We estimated species' climatic niches on the basis of global occurrences and annual time series of climate. We computed the distance to the niche core of drought mortality sites (982 observations, 44 tree species) and compared it with null models of randomly distributed tree mortality. We assessed how loss of xylem conductance and hydraulic safety margin related to populations' position in niche space and to the degree of climate anomaly during mortality.

Results

In the year of mortality, 64.3% of the sites were closer to the species' niche edge than the niche core. However, when considering long-term climate averages, both marginal and central populations experienced drought-associated pulses of mortality. Overall, tree mortality was related to populations' shifts towards the edge of species' climatic niches and, in angiosperm mortality sites, species' drought tolerances were correlated with the intensity of climatic anomalies. In gymnosperm sites, marginal populations were more affected and other processes, such as heat-induced stress or cumulative drought effects, may have affected mortality.

Main Conclusions

Both marginal and central populations, even for highly drought-tolerant species, are vulnerable to climate change. Climate anomaly magnitude, cumulative drought effects, plant physiological limits and species niche geometry help explain range-wide patterns of hotter-drought-associated tree mortality.

Aim

Plastic responses of root productivity to precipitation changes would facilitate plant survival under drought stress. However, whether the responses are pervasive along the soil profile remains unknown. Here, we compiled a global dataset of root productivity at different soil depths from in situ precipitation manipulation experiments, and investigated whether the root productivity responded to precipitation changes uniformly or nonuniformly along the soil profile across diverse biomes.

Location

Global.

Time Period

Studies published during 2000–2022.

Major Taxa Studied

Mature woody plants and herbaceous.

Methods

Meta-analysis was conducted to evaluate the responses of root productivity at different soil depths to precipitation changes. The partial least squares path model (PLS-PM) was used to explore the pathways how various biotic and abiotic factors regulate these responses at different soil depths and across different vegetation types.

Results

Root productivity responded divergently to decreased precipitation between surface and deep soil. Decreased precipitation significantly reduced root productivity in surface soil (effect size: −0.19 ± 0.05), but significantly increased root productivity in deep soil (effect size: 0.18 ± 0.13), particularly under long-term (> 3 years) and severe (> 50% reduction in precipitation) drought treatments. Increased precipitation stimulates root productivity in all soil layers, with increasing stimulation towards deep soil depth.

Main Conclusions

This study highlights higher sensitivity of deep soil root productivity to precipitation changes, providing crucial insights into potential shifts in ecosystem belowground structure and functioning in a more extreme climate regime.

Aim

Plants are hypothesised to have changed in function, biogeography and environmental impact throughout the Phanerozoic. The fossil record preserves large-scale shifts in water use traits with evolution. We test how time-appropriate plants modified their environment differently based on their water use traits and where they survived during Earth's penultimate icehouse using a computer model.

Location

Global Pangea.

Time Period

The Late Palaeozoic Ice Age (LPIA, 330–290 Ma).

Major Taxa Studied

Iconic plant groups of the LPIA—marratialean tree ferns, arborescent lycopsids, medullosans and early diverging conifers.

Methods

We utilise fossil-preserved water-use traits to inform a fundamental biophysical trade-off in simulations using the palaeo-ecosystem model Paleo-BGCv2.0. Simulations were driven by atmospheric conditions from an Earth System Model (CESMv1.2) for the Carboniferous (~300 Ma) to test hypotheses regarding LPIA vegetation–environment interactions. We use these simulations to infer arborescent vegetation cover and frame simulation differences so that they may be compared to two large-scale, well-documented community turnovers late in the LPIA, using end-member CO₂ concentrations and plant types to evaluate potential feedbacks to water availability.

Results

Simulated forest cover varied widely in global terrestrial extent, from less than 5% to greater than 65% cover. This difference was the result of fossil-informed water-use traits corresponding to two broad categories of LPIA plants: wet- and dry-adapted. The addition of stem physiology in this work restricts wet-adapted plants to high-precipitation regions. Expanded biogeography interacted with the prolonged water use of dry-adapted plants to reduce site water balance. The transition to dry-adapted plant types with constant CO₂ reduced runoff up to 36%, as compared to halving CO₂, which reduced runoff up to 95%.

Main Conclusions

Dry-adapted plants likely created environments that promoted thei