Wood and water: How trees modify wood development to cope with drought

Abstract

Societal Impact Statement Drought plays a conspicuous role in forest mortality, and is expected to become more severe in future climate scenarios. Recent surges in drought‐associated forest tree mortality have been documented worldwide. For example, recent droughts in California and Texas killed approximately 129 million and 300 million trees, respectively. Drought has also induced acute pine tree mortality across east‐central China, and across extensive areas in southwest China. Understanding the biological processes that enable trees to modify wood development to mitigate the adverse effects of drought will be crucial for the development of successful strategies for future forest management and conservation. Summary Drought is a recurrent stress to forests, causing periodic forest mortality with enormous economic and environmental costs. Wood is the water‐conducting tissue of tree stems, and trees modify wood development to create anatomical features and hydraulic properties that can mitigate drought stress. This modification of wood development can be seen in tree rings where not only the amount of wood but also the morphology of the water‐conducting cells are modified in response to environmental conditions. In this review, we provide an overview of how trees conduct water, and how trees modify wood development to affect water conduction properties in response to drought. We discuss key needs for new research, and how new knowledge of wood formation can play a role in the conservation of forests under threat by climate change.

Synergies and Entanglement in Secondary Cell Wall Development and Abiotic Stress Response in Trees

“…Given the role of xylem in water transport ( Rodriguez-Zaccaro and Groover, 2019 ), it is not surprising that alterations in wood composition often result in reduced water transport ( Kitin et al, 2010 ). In Arabidopsis , this can be mitigated by restoring expression of SCW-related genes in vessels ( De Meester et al, 2018 ).…”

Impact of Severe Drought during the Strong 2015/2016 El Nino on the Phenology and Survival of Secondary Dry Dipterocarp Species in Western Thailand

“…For instance, the prolonged drought during the strong 1997/1998 El Niño induced high tree mortality and dieback in SEA tropical rainforests especially in younger trees [30,31]. Understanding the responses of tree species from different functional groups to drought stress will enable new approaches for predicting and mitigating the future effects of drought [27,32]. Yet, the high diversity of tree species in TDFs complicates the task to distinct different groups of species exhibiting similar phenological responses or adaptation to drought.…”

Climate has a larger effect than stand basal area on wood density in Pinus ponderosa var. scopulorum in the southwestern USA

“…The southwestern USA is subject to periodic droughts that have the effect of reducing crown growth (Adams and Kolb 2005) which can increase latewood proportion and therefore ring density (Larson 1969). Additionally, turgor pressure is the mechanism that drives cell expansion (Hsiao 1973;Rathgeber et al 2016;Rodriguez-Zaccaro and Groover 2019). Therefore, in addition to indirectly affecting ring density through suppression of crown growth, drought could directly increase ring density by limiting the expansion of earlywood cells (Hsiao 1973;Rodriguez-Zaccaro and Groover 2019).…”

“…Additionally, turgor pressure is the mechanism that drives cell expansion (Hsiao 1973;Rathgeber et al 2016;Rodriguez-Zaccaro and Groover 2019). Therefore, in addition to indirectly affecting ring density through suppression of crown growth, drought could directly increase ring density by limiting the expansion of earlywood cells (Hsiao 1973;Rodriguez-Zaccaro and Groover 2019). Ponderosa pine growth is most responsive to the previous winter's precipitation (Adams and Kolb 2005;Kerhoulas et al 2013), suggesting that drought could cause a narrower earlywood band and increase the overall ring density.…”