Field experiment on transpiration from isolated urban plants

Abstract

Abstract:The effect of pot plant density on plant transpiration rate was examined in a series of field experiments. Three spatial densities were created using 203 nearly homogeneous pot plants; the ratios of plant separation to plant height were 0Ð25, 0Ð5, and 3 for the 'high,' 'medium,' and 'low' groups respectively. The daily transpiration rate of 55 pot plants was measured for 28 days. During that period, the plants were randomly rotated each day to statistically eliminate individual characteristics and to successfully ascertain the effect of plant spatial density on the transpiration rate. As a best-case scenario, the soil for each plant was saturated at the start of each experiment. The results showed that the transpiration rate of potted plants in the 'low' group was about 1Ð5 times greater than that of the 'high' group. On the basis of the transpiration rate per unit of vegetation area projected on a horizontal plain, which is a general index used in meteorological modeling, the plants in the 'low' group evaporated 2Ð7 times as much water as those in the centre of the 'high' group. These results indicate the need for modified models that can consider the relative increase in evapotranspiration from vegetation in small-size plants or low spatial density of vegetation to estimate latent heat flux in urban areas.

Water, heat, and airborne pollutants effects on transpiration of urban trees

“…Measured under comparable conditions, the sap flux densities of P. tabulaeformis and R. pseudoacacia grown in the urban center were considerably higher than those growing in the surrounding suburban Beijing where trees grown in natural forest settings (Ma et al, 2006; Fan et al, 2008). The significant increment of tree transpiration in the urban area may be attributable to the higher air temperatures (Wang et al, 2005;Xiao et al, 2007) and lower plant density (Hagishima et al, 2007) in urban than suburban Beijing.…”

“…Vegetations occupying isolated and small urban spaces such as hedges, garden plants, and roadside trees are exposed to more intense radiation and sensible heat due to a lack of obstacles therefore lose more water than comparable vegetations in the forests (Van Bavel et al, 1962;Hagishima et al, 2007). The pervasive presence of airborne pollutants would be a confounding issue.…”

“…The water use patterns of potted plants arranged in varying urban landscaping compositions have been investigated (Neighbour et al, 1988;Montague and Kjelgren, 2004;Hagishima et al, 2007). The small potted trees and mature trees in situ are different in energy budgets, canopy/root balance, architecture, and carbon allocation patterns (McLaughlin et al, 2007).…”

The ecology and evolution of constructed ecosystems as green infrastructure

“…Compared with many other types of constructed ecosystem, container gardens, like indoor potted plant ecosystems (e.g., Orwell et al, 2004) they are often designed and installed by ordinary citizens outside of the professional and academic fields of ecological engineering. The emphasis on green infrastructure to date has been on "big": wide expanses of relatively natural forest, wetland or riverine habitats, or large organisms (trees in the urban forest) but the role of microgreening in food production (Hui, 2011), ameliorating microclimates (Hagishima et al, 2007), and providing visual relief (Kaplan, 2001;Groenewegen et al, 2006) may be important where it provides the only green infrastructure in the urban core and can be readily implemented by urban residents.…”

Ozone uptake by adult urban trees based on sap flow measurement

“…At a given ambient O 3 concentration, the rate of O 3 uptake by leaves was effectively controlled by stomatal conductance, which is influenced by factors such as leaf characteristics, crown position, tree age, tree height, climate, and altitude (Beckett et al, 2000;Schafer et al, 2000;Wieser et al, 2000;Nunn et al, 2007). In urban settings, higher temperature (Landsberg, 1981), lower plant density (Hagishima et al, 2007), irrigation (Martin and Stabler, 2002), energy balance properties of urban surfaces (Montague and Kjelgren, 2004), and night illumination (Longcore and Rich, 2004) may allow for higher stomata aperture, hence, more O 3 uptake. Considerable researches have been conducted to investigate ozone uptake by natural forests (Wieser et al, 2003(Wieser et al, , 2006Nunn et al, 2007;Köstner et al, 2008;Braun et al, 2010).…”