| 1. |
- Manzoni, Stefano, et al.
(författare)
-
Hydraulic limits on maximum plant transpiration and the emergence of the safety-efficiency trade-off
- 2013
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 198, s. 169-178
-
Tidskriftsartikel (refereegranskat)abstract
- Soil and plant hydraulics constrain ecosystem productivity by setting physical limits to water transport and hence carbon uptake by leaves. While more negative xylem water potentials provide a larger driving force for water transport, they also cause cavitation that limits hydraulic conductivity. An optimum balance between driving force and cavitation occurs at intermediate water potentials, thus defining the maximum transpiration rate the xylem can sustain (denoted as Emax). The presence of this maximum raises the question as to whether plants regulate transpiration through stomata to function near Emax. To address this question, we calculated Emax across plant functional types and climates using a hydraulic model and a global database of plant hydraulic traits. The predicted Emax compared well with measured peak transpiration across plant sizes and growth conditions (R=0.86, P<0.001) and was relatively conserved among plant types (for a given plant size), while increasing across climates following the atmospheric evaporative demand. The fact that Emax was roughly conserved across plant types and scales with the product of xylem saturated conductivity and water potential at 50% cavitation was used here to explain the safetyefficiency trade-off in plant xylem. Stomatal conductance allows maximum transpiration rates despite partial cavitation in the xylem thereby suggesting coordination between stomatal regulation and xylem hydraulic characteristics.
|
|
| 2. |
|
|
| 3. |
- Manzoni, Stefano, et al.
(författare)
-
Optimal plant water-use strategies under stochastic rainfall
- 2014
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 50:7, s. 5379-5394
-
Tidskriftsartikel (refereegranskat)abstract
- Plant hydraulic traits have been conjectured to be coordinated, thereby providing plants with a balanced hydraulic system that protects them from cavitation while allowing an efficient transport of water necessary for photosynthesis. In particular, observations suggest correlations between the water potentials at which xylem cavitation impairs water movement and the one at stomatal closure, and between maximum xylem and stomatal conductances, begging the question as to whether such coordination emerges as an optimal water-use strategy under unpredictable rainfall. Here mean transpiration is used as a proxy for long-term plant fitness and its variations as a function of the water potentials at 50% loss of stem conductivity due to cavitation and at 90% stomatal closure are explored. It is shown that coordination between these hydraulic traits is necessary to maximize , with rainfall patterns altering the optimal range of trait values. In contrast, coordination between ecosystem-level conductances appears not necessary to maximize . The optimal trait ranges are wider under drier than under mesic conditions, suggesting that in semiarid systems different water use strategies may be equally successful. Comparison with observations across species from a range of ecosystems confirms model predictions, indicating that the coordinated functioning of plant organs might indeed emerge from an optimal response to rainfall variability.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Vico, Giulia
(författare)
-
Coupled carbon and water fluxes in CAM photosynthesis: modeling quantification of water use efficiency and productivity
- 2014
-
Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 383, s. 111-138
-
Tidskriftsartikel (refereegranskat)abstract
- Due to their high water use efficiency, Crassulacean acid metabolism (CAM) plants are of environmental and economic importance in the arid and semiarid regions of the world. Moreover, many CAM plants (e.g., Agave tequilana) have attractive qualities for biofuel production such as a relatively low lignin content and high amount of soluble carbohydrates. However, the current estimates of CAM productivity are based on empirical stress indices that create large uncertainties. As a first step towards a more accurate quantification of CAM productivity, this paper introduces a new model that couples both soil and atmosphere conditions to CAM photosynthesis.The new CAM model is based upon well established C-3 photosynthesis models coupled to a nonlinear circadian rhythm oscillator for the control of the photosynthesis carbon fluxes. The leaf-level dynamics are coupled to a simple, yet realistic description of the soil-plant-atmosphere continuum, including a plant water capacitance module.The resulting model reproduces the four phases of CAM photosynthes is and the evolution of their dynamics during a soil moisture drydown, as a function of soil type, plant features, and climatic conditions.The results help quantify the impact of soil water availability on CAM carbon assimilation and transpiration flux.
|
|
| 9. |
- Vico, Giulia
(författare)
-
Ecohydrology of street trees: design and irrigation requirements for sustainable water use
- 2014
-
Ingår i: Ecohydrology. - : Wiley. - 1936-0584 .- 1936-0592. ; 7, s. 508-523
-
Tidskriftsartikel (refereegranskat)abstract
- Whereas the beneficial effects of urban vegetation have long been recognized, growing conditions in urban environments, especially for street trees, are typically harsh and limited by low water availability. Supplemental irrigation may be used to preserve aesthetic quality and ability to provide ecosystem services of urban vegetation but requires careful management of available economic and water resources to reduce urban water footprint. To this purpose, decision makers need quantitative tools, requiring few, physically based parameters and accounting for the uncertainties and future scenarios of the hydroclimatic forcing. Focusing on in-row and isolated trees, a minimalist description of street tree water balance is proposed here, including rainfed and irrigated conditions, and explicitly accounting for tree water requirements, growing conditions (in terms of soil properties and extension of bare soil, permeable and impervious pavements surrounding the tree) and rainfall unpredictability. The proposed model allows the quantification of tree cooling capacity, water stress occurrence and irrigation requirements, as a function of soil, plant and climate characteristics, thus providing indications regarding the tree ability to provide ecosystem services and management costs. In particular, an analysis of different planting designs suggests that a balanced design consisting in bare soil and permeable pavement with size equal to the lateral canopy extension is optimal for water conservation, tree cooling capacity and health. The proposed model provides useful indications towards the definition of site-specific guidelines for species selection and planting design, for sustainable urban vegetation. Copyright (c) 2013 John Wiley & Sons, Ltd.
|
|
| 10. |
- Vico, Giulia
(författare)
-
Elliptically Symmetric Distributions of Elevation Gradients and the Distribution of Topographic Aspect
- 2013
-
Ingår i: Mathematical Geosciences. - : Springer Science and Business Media LLC. - 1874-8961 .- 1874-8953. ; 45, s. 819-835
-
Tidskriftsartikel (refereegranskat)abstract
- Characterizing the spatial variability of topography is essential when modeling landscape processes such as surface energy and water balances, and landslide and avalanche risk, to name a few. A probabilistic representation of topographic features is a parsimonious alternative to the more detailed but computationally demanding descriptions. In this work, an analytical expression for the theoretical distribution of topographic aspect is obtained that is based on the statistical parameters of the topographic elevation gradients, that is, the mean, standard deviation, and correlation coefficient. For this expression, an elliptically symmetric distribution of elevation gradients is assumed, and this assumption is validated with the resulting theoretical distribution of aspect using the data of six case studies in the continental United States with different geology, elevation range, climate, and vegetation. The comparison shows that the theoretical distribution of aspect is a suitable description for the observed distribution of aspect on a regional scale. Consequently, the theoretical expression for the distribution of aspect could be a useful tool in models that rely on aspect for the accuracy of surface energy and water balances, and other relevant processes.
|
|
