scholarly journals Temperature Reduction in Urban Surface Materials through Tree Shading Depends on Surface Type Not Tree Species

Forests ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1141
Author(s):  
Kaluarachichi T.U.N. ◽  
Tjoelker M.G. ◽  
Pfautsch S.
Keyword(s):  
Urban Space ◽  
Tree Species ◽  
Austral Summer ◽  
Bare Soil ◽  
Urban Surface ◽  
Surface Material ◽  
Free Standing ◽  
Area Index ◽  
Surface Temperatures ◽  
Surface Materials

Trees play a vital role in urban cooling. The present study tested if key canopy characteristics related to tree shade could be used to predict the cooling potential across a range of urban surface materials. During the austral summer of 2018–2019, tree and canopy characteristics of 471 free-standing trees from 13 species were recorded across Greater Sydney, Australia. Stem girth and tree height, as well as leaf area index and ground-projected crown area was measured for every tree. Surface temperatures were recorded between noon (daylight saving time) and 3:00 p.m. under the canopy of each tree in the shade and in full sun to calculate the temperature differential between adjacent sunlit and shaded surfaces (∆Ts). The limited control over environmental parameters was addressed by using a large number of randomly selected trees and measurement points of surface temperatures. Analyses revealed that no systematic relationship existed among canopy characteristics and ∆Ts for any surface material. However, highly significant differences (p < 0.001) in ∆Ts existed among surface materials. The largest cooling potential of tree shade was found by shading bark mulch (∆Ts = −24.8 °C ± 7.1), followed by bare soil (∆Ts = −22.1 °C ± 5.5), bitumen (∆Ts = −20.9 °C ± 5.8), grass (∆Ts = −18.5 °C ± 4.8) and concrete pavers (∆Ts = −17.5 °C ± 6.0). The results indicate that surface material, but not the tree species, matters for shade cooling of common urban surfaces. Shading bark mulch, bare soil or bitumen will provide the largest reductions in surface temperature, which in turn results in effective mitigation of radiant heat. This refined understanding of the capacity of trees to reduce thermal loads in urban space can increase the effectiveness of urban cooling strategies.

scholarly journals A Comparison of the Shading Effectiveness of Five Different Street Tree Species in Manchester, UK

2013 ◽  
Vol 39 (4) ◽  
Author(s):  
David Armson ◽  
Mohammad Asrafur Rahman ◽  
Anthony Roland Ennos
Keyword(s):  
Tree Species ◽  
Urban Areas ◽  
Urban Landscape ◽  
Urban Trees ◽  
Area Index ◽  
Pyrus Calleryana ◽  
Human Thermal Comfort ◽  
Surface Temperatures ◽  
Street Tree ◽  
Crataegus Laevigata

One major benefit of urban trees is the shade they provide on sunny days; this reduces the heat stored in engineered surfaces and lowers the heat load on people, increasing their comfort. This study compared the shading effectiveness of five small street tree species within the urban landscape of Manchester, UK. The area of shade produced by each tree during early and midsummer 2012 was calculated from morphological measurements, such as canopy height, width, and aspect ratio. The effect of tree shade on air, mean radiant and surface temperatures was also compared and related to the leaf area index (LAI) of the canopy. It was found that tree shade reduced mean radiant temperatures by an average of 4°C, though neither tree species nor LAI had a significant effect. Tree shade reduced surface temperatures by an average of 12°C, and the tree species and LAI both had significant effects. Tree species with higher LAI, Crataegus laevigata and Pyrus calleryana, provided significantly more cooling than the other species, and surface temperature reduction was positively correlated with LAI. This study has shown that trees are useful in improving both human thermal comfort and reducing surface temperatures in urban areas, and that selection of tree species with high LAI can maximize the benefits they provide.

scholarly journals GROWTH OF DIFFERENT FRUIT TREE SPECIES IN SILVOPASTORAL SYSTEMS DURING THE ESTABLISHMENT PHASE

2017 ◽  
Vol 30 (4) ◽  
pp. 1040-1049 ◽  
Author(s):  
CAROLINA DELLA GIUSTINA ◽  
ROBERTA APARECIDA CARNEVALLI ◽  
MARCELO RIBEIRO ROMANO ◽  
DIEGO BARBOSA ALVES ANTONIO ◽  
CAMILA ECKSTEIN
Keyword(s):  
Tree Species ◽  
Block Design ◽  
Control Plant ◽  
Fruit Trees ◽  
Fruit Tree ◽  
Silvopastoral Systems ◽  
Area Index ◽  
Mato Grosso ◽  
Plant Accumulation ◽  
Establishment Phase

ABSTRACT The benefits of integrating agricultural components into silvopastoral systems are widely known, but the limited knowledge about ecological processes in the establishment phase impedes the use of this technology. The objective of this study was to evaluate interactions between fruit tree species and the sward layer under canopies of trees in the establishment phase of silvopastoral systems in Mato Grosso, Brazil. The experiment was implemented in October 2013, with an evaluation period from January to July 2015. The systems were composed of eight fruit trees intercropped with Tifton 85 grass. A completely randomized block design was adopted, with two replications per area per treatment. We evaluated the agronomic performance of the fruit trees, the categories of the light environment, and the plant accumulation under the canopies. The acerola fruit trees of the variety Roxinha had higher Leaf area index (LAI) and Light interception (LI) values, showing a denser canopy with small porosity and the lowest light quality available to the plants beneath the canopy (lower red/far-red ratio), thereby decreasing plant accumulation under trees. The guava fruit trees showed higher growth rates than the other fruit trees, but lower LAI and LI values and a higher red/far-red ratio, allowing higher plant growth under the canopy. Cajá trees showed a similar behavior; however, this species is deciduous, which limits its potential use in integrated systems. Banana and coconut trees were highly dependent on irrigation during the dry season. The remaining species showed an adequate growth and potential to control plant species growth under their canopies.

scholarly journals Forest summer albedo is sensitive to species and thinning: how should we account for this in Earth system models?

2014 ◽  
Vol 11 (8) ◽  
pp. 2411-2427 ◽  
Author(s):  
J. Otto ◽  
D. Berveiller ◽  
F.-M. Bréon ◽  
N. Delpierre ◽  
G. Geppert ◽  
...  
Keyword(s):  
Forest Management ◽  
Tree Species ◽  
Near Infrared ◽  
Model Parameters ◽  
Earth System ◽  
Forest Thinning ◽  
Area Index ◽  
System Models ◽  
Maximum Change ◽  
Earth System Models

Abstract. Although forest management is one of the instruments proposed to mitigate climate change, the relationship between forest management and canopy albedo has been ignored so far by climate models. Here we develop an approach that could be implemented in Earth system models. A stand-level forest gap model is combined with a canopy radiation transfer model and satellite-derived model parameters to quantify the effects of forest thinning on summertime canopy albedo. This approach reveals which parameter has the largest affect on summer canopy albedo: we examined the effects of three forest species (pine, beech, oak) and four thinning strategies with a constant forest floor albedo (light to intense thinning regimes) and five different solar zenith angles at five different sites (40° N 9° E–60° N 9° E). During stand establishment, summertime canopy albedo is driven by tree species. In the later stages of stand development, the effect of tree species on summertime canopy albedo decreases in favour of an increasing influence of forest thinning. These trends continue until the end of the rotation, where thinning explains up to 50% of the variance in near-infrared albedo and up to 70% of the variance in visible canopy albedo. The absolute summertime canopy albedo of all species ranges from 0.03 to 0.06 (visible) and 0.20 to 0.28 (near-infrared); thus the albedo needs to be parameterised at species level. In addition, Earth system models need to account for forest management in such a way that structural changes in the canopy are described by changes in leaf area index and crown volume (maximum change of 0.02 visible and 0.05 near-infrared albedo) and that the expression of albedo depends on the solar zenith angle (maximum change of 0.02 visible and 0.05 near-infrared albedo). Earth system models taking into account these parameters would not only be able to examine the spatial effects of forest management but also the total effects of forest management on climate.

scholarly journals Analyses of urban pavement surface temperatures

2015 ◽  
Vol 10 (3) ◽  
pp. 239-246 ◽  
Author(s):  
Aleksandra Deluka-Tibljaš ◽  
Sanja Šurdonja ◽  
Sergije Babić ◽  
Marijana Cuculić
Keyword(s):  
Urban Areas ◽  
Concrete Surface ◽  
City Centre ◽  
Heat Islands ◽  
Pavement Surface ◽  
Island Effect ◽  
Surface Temperatures ◽  
Additional Heating ◽  
Air Temperatures ◽  
Surface Materials

Heat islands are areas that have higher air temperatures than their surroundings. It has been proven that the use of certain types of pavement surface materials contributes to the occurrence of heat islands. The heat island effect is dominant in urban areas, mainly in city centres. To identify potentially favourable pavement surface materials that are suitable for the use on surfaces in urban areas, an extensive analysis of in-place material temperatures was conducted in the city centre of Rijeka (Croatia) during the summer of 2011 and 2012. The measurements included temperatures of pavement surfaces made of asphalt, concrete and stone. The analysis results identified local materials whose use help to reduce or mitigate the effect of additional heating in the urban environment caused by emission of heat from pavement surfaces. In terms of additional heating of urbanized areas, asphalt has proven to be significantly less favourable than other analysed materials. In addition to the materials selected for the use in wearing courses, their characteristics and the microclimates of the locations where they will be placed must be taken into consideration. Among the standard paving materials, in terms of heating and temperature, concrete is more favourable than asphalt because the differences between concrete surface temperatures and air temperatures are significantly smaller than between asphalt surface temperatures and air temperatures. Stone surfaces have proven to be the most favourable. The analysis results presented can be used to establish clear guidelines for using specific materials under specific conditions.

scholarly journals Detecting Unknown Artificial Urban Surface Materials Based on Spectral Dissimilarity Analysis

Sensors ◽  
2017 ◽  
Vol 17 (8) ◽  
pp. 1826 ◽  
Author(s):  
Marianne Jilge ◽  
Uta Heiden ◽  
Martin Habermeyer ◽  
André Mende ◽  
Carsten Juergens
Keyword(s):  
Urban Surface ◽  
Surface Materials

scholarly journals Leaf and Crown Optical Properties of Five Early-, Mid- and Late-Successional Temperate Tree Species and Their Relation to Sapling Light Demand

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 925 ◽  
Author(s):  
Marc Hagemeier ◽  
Christoph Leuschner
Keyword(s):  
Optical Properties ◽  
Leaf Area ◽  
Tree Species ◽  
Forest Floor ◽  
The Sun ◽  
Area Index ◽  
Minimum Light ◽  
Tree Canopies ◽  
Successional Species ◽  
Shade Leaves

The optical properties of leaves and canopies determine the availability of radiation for photosynthesis and the penetration of light through tree canopies. How leaf absorptance, reflectance and transmittance and radiation transmission through tree canopies change with forest succession is not well understood. We measured the leaf optical properties in the photosynthetically active radiation (PAR) range of five Central European early-, mid- and late-successional temperate broadleaf tree species and studied the minimum light demand of the lowermost shade leaves and of the species’ offspring. Leaf absorptance in the 350–720 nm range varied between c. 70% and 77% in the crown of all five species with only a minor variation from the sun to the shade crown and between species. However, specific absorptance (absorptance normalized by mass per leaf area) increased about threefold from sun to shade leaves with decreasing leaf mass area (LMA) in the late-successional species (Carpinus betulus L., Tilia cordata Mill., Fagus sylvatica L.), while it was generally lower in the early- to mid-successional species (Betula pendula Roth, Quercus petraea (Matt.)Liebl.), where it changed only a little from sun to shade crown. Due to a significant increase in leaf area index, canopy PAR transmittance to the forest floor decreased from early- to late-successional species from ~15% to 1%–3% of incident PAR, linked to a decrease in the minimum light demand of the lowermost shade leaves (from ~20 to 1%–2%) and of the species’ saplings (from ~20 to 3%–4%). The median light intensity on the forest floor under a closed canopy was in all species lower than the saplings’ minimum light demand. We conclude that the optical properties of the sun leaves are very similar among early-, mid- and late-successional tree species, while the shade leaves of these groups differ not only morphologically, but also in terms of the resource investment needed to achieve high PAR absorptance.

scholarly journals Effects of vegetation structure on biomass accumulation in a Balanced Optimality Structure Vegetation Model (BOSVM v1.0)

2013 ◽  
Vol 6 (3) ◽  
pp. 4603-4663 ◽  
Author(s):  
Z. Yin ◽  
S. C. Dekker ◽  
B. J. J. M. van den Hurk ◽  
H. A. Dijkstra
Keyword(s):  
Water Stress ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Vegetation Structure ◽  
Bare Soil ◽  
Feedback Mechanism ◽  
Carbon Gain ◽  
Area Index ◽  
Local Climate ◽  
Vegetation Structures

Abstract. A myriad of interactions exist between vegetation and local climate for arid and semi-arid regions. Vegetation function, structure and individual behavior have large impacts on carbon-water-energy balances, which consequently influence local climate variability that, in turn, feeds back to the vegetation. In this study, a conceptual vegetation structure scheme is formulated and tested in a new carbon-water-energy coupled model to explore the importance of vegetation structure and vegetation adaptation to water stress on equilibrium biomass states. Surface energy, water and carbon fluxes are simulated for a range of vegetation structures across a precipitation gradient in West Africa and optimal vegetation structures that maximizes biomass for each precipitation regime are determined. Two different strategies of vegetation adaptation to water stress are included. Under dry conditions vegetation tries to maximize the Water Use Efficiency and Leaf Area Index as it tries to maximize carbon gain. However, an important negative feedback mechanism is found as the vegetation also tries to minimize its cover to optimize the surrounding bare ground area from which water can be extracted, thereby forming patches of vertical vegetation. Under larger precipitation, a positive feedback mechanism is found in which vegetation tries to maximize its cover as it then can reduce water loss from bare soil while having maximum carbon gain due to a large Leaf Area Index. The competition between vegetation and bare soil determines a transition between a "survival" state to a "growing" state.

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