ORCID Profile
0000-0003-1695-4696
Current Organisation
Colorado State University
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Publisher: Wiley
Date: 03-2017
DOI: 10.1111/JVS.12524
Publisher: Wiley
Date: 10-10-2023
DOI: 10.1111/GCB.16950
Publisher: Wiley
Date: 18-08-2021
DOI: 10.1002/ECY.3465
Abstract: Extreme drought decreases aboveground net primary production (ANPP) in most grasslands, but the magnitude of ANPP reductions varies especially in C 3 ‐dominated grasslands. Because the mechanisms underlying such differential ecosystem responses to drought are not well resolved, we experimentally imposed an extreme 4‐yr drought (2015–2018) in two C 3 grasslands that differed in aridity. These sites had similar annual precipitation and dominant grass species ( Leymus chinensis ) but different annual temperatures and thus water availability. Drought treatments differentially affected these two semiarid grasslands, with ANPP of the drier site reduced more than at the wetter site. Structural equation modeling revealed that community‐weighted means for some traits modified relationships between soil moisture and ANPP, often due to intraspecific variation. Specifically, drought reduced community mean plant height at both sites, resulting in a reduction in ANPP beyond that attributable to reduced soil moisture alone. Higher community mean leaf carbon content enhanced the negative effects of drought on ANPP at the drier site, and ANPP–soil‐moisture relationships were influenced by soil C:N ratio at the wetter site. Importantly, neither species richness nor functional dispersion were significantly correlated with ANPP at either site. Overall, as expected, soil moisture was a dominant, direct driver of ANPP response to drought, but differential sensitivity to drought in these two grasslands was also related to soil fertility and plant traits.
Publisher: Wiley
Date: 10-02-2023
Abstract: Leaf hydraulic traits characterize plant drought tolerance and responses to climate change. Yet, plant hydraulics are biased towards northern hemisphere woody species. We collected rhizomes of several perennial grass species along a precipitation gradient in eastern Australia and grew them in an experimental pot study to investigate potential trade‐offs between drought tolerance and plant morphology. We measured the following leaf hydraulic traits: the leaf water potential (Ψ leaf ) at 50% and 88% loss of leaf hydraulic conductance (P50 Kleaf and P88 Kleaf ), the Ψ leaf at 50% loss of stomatal conductance (P50 gs ), leaf turgor loss point (TLP), leaf dry matter content (LDMC), leaf modulus of elasticity (ε), and the slope of the relationship between predawn and midday Ψ leaf . We also measured basal area, tiller density, seed head density, root collar diameter, plant height, and aboveground biomass of each in idual. As expected, grass species varied widely in leaf‐level drought tolerance, with loss of 88% hydraulic conductance occurring at a Ψ leaf ranging from −1.52 to −4.01 MPa. However, all but one species lost leaf turgor, and most reached P50 gs before this critical threshold. Taller more productive grass species tended to have drought vulnerable leaves characterized by low LDMC and less negative P88 Kleaf . Species with greater tiller production experienced stomatal closure and lost turgor at more negative Ψ leaf . Although our s le size was limited, we found no relationships between these species' traits and their climate of origin. Overall, we identified important hydraulic and morphological trade‐offs in Australian grasses that were surprisingly similar to those observed for woody plants: (1) xylem of taller species was less drought tolerant and (2) turgor loss occurs and stomatal closure begins before significant loss of K leaf . These data build upon a small yet growing field of grass hydraulics and may be informative of species responses to further drought intensification in Australia. Read the free Plain Language Summary for this article on the Journal blog.
No related grants have been discovered for Alan Knapp.