Browsing by Subject "hydraulic conductivity"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Climate determines vascular traits in the ecologically diverse genus Eucalyptus
    (Wiley, 2016) Pfautsch, Sebastian; Harbusch, Marco; Wesolowski, Anita; Smith, Renee; Macfarlane, Craig; Tjoelker, Mark G; Reich, Peter B; Adams, Mark A
    Current theory presumes that natural selection on vascular traits is controlled by a trade-off between efficiency and safety of hydraulic architecture. Hence, traits linked to efficiency, such as vessel diameter, should show biogeographic patterns; but critical tests of these predictions are rare, largely owing to confounding effects of environment, tree size and phylogeny. Using wood sampled from a phylogenetically constrained set of 28 Eucalyptus species, collected from a wide gradient of aridity across Australia, we show that hydraulic architecture reflects adaptive radiation of this genus in response to variation in climate. With increasing aridity, vessel diameters narrow, their frequency increases with a distribution that becomes gradually positively skewed and sapwood density increases while the theoretical hydraulic conductivity declines. Differences in these hydraulic traits appear largely genotypic in origin rather than environmentally plastic. Data reported here reflect long-term adaptation of hydraulic architecture to water availability. Rapidly changing climates, on the other hand, present significant challenges to the ability of eucalypts to adapt their vasculature.
  • Thumbnail Image
    Item
    Hydraulic and Mechanical Properties of Recycled Materials
    (Minnesota Department of Transportation, 2009-10) Gupta, Satish; Kang, Dong Hee; Ranaivoson, Andry
    Construction and maintenance of roads requires large volume of aggregates for use as base and subbase materials. Because of the cost of virgin aggregates, federal and state agencies are encouraging the recycling of waste materials including materials in old pavements. This study assessed the suitability of four recycled materials relative to virgin aggregates for use as base and subbase materials. The four recycled materials were the reclaimed asphalt pavement (RAP), fly ash (FA), reclaimed concrete material (RCM), and foundry sand (FS). Assessment of these materials was done in terms of their hydraulic, mechanical, and leaching properties when mixed in with various proportions of virgin aggregates. Except for slightly higher fine content in some RAP-aggregate mixtures, particle size distribution of all mixtures was within the Mn/DOT specification band for Class 5 materials. Water retention (pore size distribution), hydraulic conductivity, resilient modulus, and shear strength measurements were generally similar to that of 100% aggregates. Exception was the mixtures of FS. Heavy metal concentrations in the leachate were also generally less than the EPA drinking water standards. We concluded that FA, RAP, and RCM mixtures will be good substitutes of virgin aggregates as base and subbase materials.
  • Thumbnail Image
    Item
    Is it getting hot in here? Adjustment of hydraulic parameters in six boreal and temperate tree species after 5 years of warming
    (Wiley, 2016) Mculloh, Katherine A; Petitmermet, Joshua; Stefanski, Artur; Rice, Karen E; Rich, Roy L.; Montgomery, Rebecca A; Reich, Peter B
    Global temperatures (T) are rising, and for many plant species, their physiological response to this change has not been well characterized. In particular, how hydraulic parameters may change has only been examined experimentally for a few species. To address this, we measured characteristics of the hydraulic architecture of six species growing in ambient T and ambient +3.4 °C T plots in two experimentally warmed forest sites in Minnesota. These sites are at the temperate–boreal ecotone, and we measured three species from each forest type. We hypothesized that relative to boreal species, temperate species near their northern range border would increase xylem conduit diameters when grown under elevated T. We also predicted a continuum of responses among wood types, with conduit diameter increases correlating with increases in the complexity of wood structure. Finally, we predicted that increases in conduit diameter and specific hydraulic conductivity would positively affect photosynthetic rates and growth. Our results generally supported our hypotheses, and conduit diameter increased under elevated T across all species, although this pattern was driven predominantly by three species. Two of these species were temperate angiosperms, but one was a boreal conifer, contrary to predictions. We observed positive relationships between the change in specific hydraulic conductivity and both photosynthetic rate (P = 0.080) and growth (P = 0.012). Our results indicate that species differ in their ability to adjust hydraulically to increases in T. Specifically, species with more complex xylem anatomy, particularly those individuals growing near the cooler edge of their range, appeared to be better able to increase conduit diameters and specific hydraulic conductivity, which permitted increases in photosynthesis and growth. Our data support results that indicate individual's ability to physiologically adjust is related to their location within their species range, and highlight that some wood types may adjust more easily than others.