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

Abstract

a b s t r a c tTranspiration rates of six urban tree species in Beijing evaluated by thermal dissipation method for one year were correlated to environmental variables in heat, water, and pollutant groups. To sort out colinearity of the explanatory variables, their individual and joint contributions to variance of tree transpiration were determined by the variation and hierarchical partitioning methods. Majority of the variance in transpiration rates was associated with joint effects of variables in heat and water groups and variance due to individual effects of explanatory group were in comparison small. Atmospheric pollutants exerted only minor effects on tree transpiration. Daily transpiration rate was most affected by air temperature, soil temperature, total radiation, vapor pressure deficit, and ozone. Relative humidity would replace soil temperature when factors influencing hourly transpiration rate was considered.

Quantifying the impacts of socio-economic factors on air quality in Chinese cities from 2000 to 2009

“…Variation partitioning was used to decompose the variation in air quality, following the methods described by Anderson and Gribble (1998), Heikkinen et al (2004Heikkinen et al ( , 2005, and Wang et al (2011). This partitions the variance of AOFDAQ-A into eight fractions, namely the individual effects of urbanization, pollution, and environmental treatment, respectively; joint effects of urbanization and pollution, urbanization and environmental treatment, and pollution and environmental treatment respectively; joint effects of the three explanatory variable groups; and finally unexplained variance.…”

“…Explanatory variables that did not contribute significantly to the variance of AOFDAQ-A at p > 0.05 (Borcard et al, 1992;Wang et al, 2011) were excluded. Quadratic terms of predictors were also analyzed in this procedure to take potential curvilinear relationships into account (Heikkinen et al, 2004;Wang et al, 2011). Only significant predictor variables identified in this process were included in the subsequent analyses.…”

“…Only significant predictor variables identified in this process were included in the subsequent analyses. The other three steps to calculate the value of the eight fractions followed Wang et al (2011).…”

“…Hence, for those variables which were only significant in quadratic terms, the quadratic terms were entered into the partitioning to improve the linearity of relationships between air quality and socio-economic variables (Wang et al, 2011).…”

Ozone uptake by adult urban trees based on sap flow measurement

“…The trees selected for certain type of species had similar diameter at the breast height (DBH), height, projected canopy area (A c ), and sapwood cross-sectional area (A s ) (Wang et al, 2011). The size of the selected trees in terms of DBH was determined based on the field surveys conducted in Beijing in 2007.…”