Translating soil salinity to agricultural salt stress: Key salt-tolerance mechanisms for agrohydrologic models.

Salt stress has a detrimental impact on crop yield and survival rates, which salt-tolerant cultivars can resist through numerous adaptive mechanisms. Most models of salt stress impacts on productivity and water use employ empirical or simplified schemes to represent salt-adaptive traits. However, with an increased understanding of these physiological tolerance mechanisms and emergent measurement techniques for monitoring key salinity dynamics, the potential for developing mechanistic agrohydrological models of the soil-plant-atmosphere continuum has grown.

Leaf transpiration decreases similarly among five pine species as height increases over stand development.

With increasing tree height, leaf transpiration (EL) is increasingly restricted by path-length resistance and gravity's discount to the driving force of xylem water flow. The effect of height on leaf transpiration is nearly always assessed using chronosequence data; however, in this long-term, dynamic study, we assessed increasing height's effects on EL using continuous monitoring of sap-flux for five Pinus species growing in a common-garden and experiencing a wide range of environmental conditions. We assessed how three drivers of EL-path-length (h), water-potential gradient (ΔΨ), and sapwood-to-leaf area ratio (AS:AL)-affect transpiration of the five Pinus species ranging five-fold in needle length by performing gas-exchange and water potential measurements, and monitoring tree biometrics, sap-flux, and soil and atmospheric conditions over five years at the Duke Forest, NC.

Xylem Hydraulic Properties of Five Pinus Species Grown in Common Environment Vary From Needles to Roots With Needle Length and Native-Range Climate.

Plant hydraulics govern water transport linking root to mesophyll surfaces, affecting gas-exchange, survival and growth. Xylem and leaf structural and functional characteristics vary widely among Pinus species, even when growing under similar conditions. We quantified the variation of xylem anatomy, hydraulic function, and within-tree hydraulic resistivity distribution, among five widely ranging southern US species: Pinus echinata, Pinus elliottii, Pinus palustris, Pinus taeda and Pinus virginiana.

The global spectrum of tree crown architecture.

Trees can differ enormously in their crown architectural traits, such as the scaling relationships between tree height, crown width and stem diameter. Yet despite the importance of crown architecture in shaping the structure and function of terrestrial ecosystems, we lack a complete picture of what drives this incredible diversity in crown shapes. Using data from 374,888 globally distributed trees, we explore how climate, disturbance, competition, functional traits, and evolutionary history constrain the height and crown width scaling relationships of 1914 tree species.