Tree growth responses to temporal variation in rainfall differ across a continental-scale climatic gradient

Abstract

Globally, many biomes are being impacted by significant shifts in total annual rainfall as well as increasing variability of rainfall within and among years. Such changes can have potentially large impacts on plant productivity and growth, but remain largely unknown, particularly for much of the Southern Hemisphere. We investigate how growth of the widespread conifer, Callitris columellaris varied with inter-annual variation in the amount, intensity and frequency of rainfall events over the last century and between semi-arid (<500 mm mean annual rainfall) and tropical (>800 mm mean annual rainfall) biomes in Australia. We used linear and polynomial regression models to investigate the strength and shape of the relationships between growth (ring width) and rainfall. At semi-arid sites, growth was strongly and linearly related to rainfall amount, regardless of differences in the seasonality and intensity of rainfall. The linear shape of the relationship indicates that predicted future declines in mean rainfall will have proportional negative impacts on long-term tree growth in semi-arid biomes. In contrast, growth in the tropics showed a weak and asymmetrical (‘concave-down’) response to rainfall amount, where growth was less responsive to changes in rainfall amount at the higher end of the rainfall range (>1250 mm annual rainfall) than at the lower end (<1000 mm annual rainfall). The asymmetric relationship indicates that long-term growth rates of Callitris in the tropics are more sensitive to increased inter-annual variability of rainfall than to changes in the mean amount of rainfall. Our findings are consistent with observations that the responses of vegetation to changes in the mean or variability of rainfall differ between mesic and semi-arid biomes. These results highlight how contrasting growth responses of a widespread species across a hydroclimatic gradient can inform understanding of potential sensitivity of different biomes to climatic variability and change.

Tree growth sensitivity to climate varies across a seasonal precipitation gradient

“…This has been documented on a temporal scale where drier sites showed increasing growth sensitivity to PDSI over the last century, paralleled by higher mortality following the ongoing drought in California (Keen et al 2021). Similar changes in growth sensitivity to climate have been reported across precipitation gradients in different functional types (Kannenberg et al 2022) and between different biomes (Hsu et al 2012, Gherardi and Sala 2019, Maurer et al 2020, O'Donnell et al 2021. We would expect these trends to continue given projections of rising temperatures (Zobel et al 2017).…”

Using Multi-decadal Satellite Records to Identify Environmental Drivers of Fire Severity Across Vegetation Types

“…It is possible that, in ecosystems of intermediate productivity, a preceding wet summer may translate into higher fire risk in successive summers due to biomass build-up [56,161]. Other studies worldwide have reported that such ecosystems are more affected by precipitation variability during the dry season than during the cool season [108,113,177] because cool seasons are not normally water-limited, contrarily to dry seasons, where precipitation increases lead to higher plant productivity and, therefore, more biomass available for burning [59,89,139].…”

A Spatiotemporal Approach in Detecting and Analyzing Hydro-climatic Change in Northwest Algeria

“…A study of the changes in data series of climate variables at annual and monthly scales in the western part of the French Mediterranean area showed that annual precipitation was too low [17]. Moreover, the study stated that monthly rainfalls were decreasing in June and increasing in November throughout the area.…”