Plant height and hydraulic vulnerability to drought and cold

Abstract

Understanding how plants survive drought and cold is increasingly important as plants worldwide experience dieback with drought in moist places and grow taller with warming in cold ones. Crucial in plant climate adaptation are the diameters of water-transporting conduits. Sampling 537 species across climate zones dominated by angiosperms, we find that plant size is unambiguously the main driver of conduit diameter variation. And because taller plants have wider conduits, and wider conduits within species are more vulnerable to conduction-blocking embolisms, taller conspecifics should be more vulnerable than shorter ones, a prediction we confirm with a plantation experiment. As a result, maximum plant size should be short under drought and cold, which cause embolism, or increase if these pressures relax. That conduit diameter and embolism vulnerability are inseparably related to plant size helps explain why factors that interact with conduit diameter, such as drought or warming, are altering plant heights worldwide.

Vestured pits and scalariform perforation plate morphology modify the relationships between angiosperm vessel diameter, climate and maximum plant height

“…developmental patterns or physical properties of the stem such as resistance to mechanical or functional failure). In addition, because the relationship between vessel diameter and plant height approximates to a power law (Olson et al ., ), mean basal vessel diameter across a wide range of mature plant heights should correlate fairly closely with maximum height. In support of this, within our dataset, the slopes for the relationships between vessel diameter and maximum plant height for species without vestures or scalariform perforations (see the ‘Results’ section, Table S3) were within the 95% confidence interval estimated for slopes for the relationships between vessel diameter and measured plant height reported in the literature (Olson & Rosell, ).…”

“…Because resistance to water flow increases with greater total path length (Giordano et al ., ; Hacke & Sperry, ), as plants grow taller the overall diameter of vessels must increase in order to maintain a tip‐to‐bole gradient from narrower to wider conduits (Olson et al ., ). Our work expands on this by showing that vessel diameter is indeed strongly related to maximum plant height, and that scalariform plates and vesturing can explain some of the variation observed in vessel–height relationships (Olson et al ., , ; Rosell & Olson, ; Morris et al ., ). By including maximum plant height in our analyses of vessel dimeters across species with different pit and perforation plate morphologies, we provide support for the idea that selection may act, to some extent, on either trait independently.…”

Convergent xylem widening among organs across diverse woody seedlings

“…Fast-growing species build wider xylem conduits at low carbon (C) cost by producing tissues of low density (Cornelissen et al, 1997;Castro-D ıez et al, 2000;Wahl & Ryser, 2000) and high nitrogen content (Reich et al, 1998;Niinemets, 1999). Across a wide range of wood densities, low-density plants (species) have the same conduit widening rate while having wider conduits than plants with high densities, for a given height (Olson et al, 2018).…”

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

“…Conversely, other studies have shown that the set of adjustments in the hydraulic system to deal with the increased stature might increase the hydraulic safety margin and, consequently, the resilience of taller trees in a scenario of reduced precipitation (Ambrose et al, ). In fact, a recent study showed that taller Amazonian forests are less sensitive to precipitation variation (Giardina et al, ), a result that contrast directly with other studies which show that larger trees suffer more during drought events in forests worldwide (Bennett et al, ; Olson et al, ). These contrasting results highlight the uncertainties about how species with different ages and heights will respond to the increase in drought intensity and duration.…”