334 Montague and Bates: Response of Maple to Reduced Irrigation Arboriculture & Urban Forestry 2015. 41(6): 334–345 Response of Two Field-grown Maple (Acer) Species to Reduced Irrigation in a High Vapor Pressure, Semi-arid Climate D. Thayne Montague and Amber Bates Abstract. Urban forests provide many benefits for those living and working in urban areas. However, urban trees face many chal- lenges (e.g., poor soil, drought, high vapor pressure deficits). Therefore, finding tree species adapted to urban climates is essential to maintain a healthy urban forest. In a semi-arid climate, field-grown ‘Autumn Blaze’ (Acer × freemanii ‘Autumn Blaze’) and shantung (A. truncatum) maple trees were subjected to three reference evapotranspiration (ETo) based irrigation regimes (100%, 66%, and 33% ETo) over a three-year establishment period (2003–2005). During this time, weather data, tree water relations, gas exchange, and growth data were measured. Growing-season maximum air temperature was 40.1°C, and maximum vapor pressure deficit was 6.8 kPa. Pre-dawn leaf water potential was more negative for ‘Autumn Blaze’ trees, and trees receiving the least amount of irrigation. However, midday stomatal conductance was similar for trees receiving 100% and 66% ETo based irrigation regimes. In addition, sto- matal conductance was greatest for ‘Autumn Blaze’ trees. Growth data were influenced by species and irrigation regime. However, despite differing irrigation volumes, greatest growth was not necessarily associated with trees receiving the greatest irrigation volume. Regardless of irrigation volume, these maple species maintained adequate growth and appearance when grown in an adverse, semi- arid climate. Despite reduced irrigation, each species appears to be adapted to harsh climates associated with urban environments. Key Words. Acer × freemanii ‘Autumn Blaze’; A. truncatum; Gas Exchange; Plant Factor; Reference Evaporation; Shantung Maple; Urban Forest; Vapor Pressure Deficit. Trees growing in urban environments are exposed to harsh growing conditions. The heterogeneous physical environment found in urban areas expose urban trees to numerous abiotic stress factors (Zwack et al. 1999). De-icing salt (Fluckiger and Braun 1981), reduced soil moisture (Clark and Kjelgren 1990; Cregg 1995; Fahey et al. 2013), lim- ited soil volume availability for root expansion (St. Hilaire and Graves 2001), and precipitation runoff onto impermeable surfaces (St. Hilaire and Graves 2001) reduce water accessibility to urban tree roots. Furthermore, compaction of urban soils may result in excessive soil moisture (Kawase 1981), or increase flooding potential (Zwack et al. 1999). Urban pollu- tion may also influence growth, and limit survival of urban trees (Muir and McCune 1988). Urban soils also tend to have greater temperatures when compared to soils of non-urban areas, and greater soil temperatures may promote faster soil moisture ©2015 International Society of Arboriculture evaporation (Graves and Dana 1987). In addition, non-vegetative, urban surfaces (e.g., asphalt, con- crete) lack evaporative cooling, and when compared to vegetative surfaces (e.g., ground covers, turf), are good conductors of energy (Montague et al. 2000). Therefore, non-vegetative surfaces store more en- ergy, and have greater surface temperatures, when compared to vegetative surfaces (Doll et al. 1985; Montague et al. 2000). Greater surface temperatures increase longwave radiation flux and sensible heat, which increase air temperature, decrease relative humidity, and raise vapor pressure deficits (VPD) in urban areas (Kim 1992; Cregg and Dix 2001). The combination of increased longwave radiation from non-vegetative surfaces (Heilman et al. 1989; Montague et al. 2000) and greater combustion from urban vehicles create an urban heat island (Kim 1992). As a result of the urban heat island, radiation load in urban sites increases, and temperatures in
November 2015
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
