Arboriculture & Urban Forestry 35(3): May 2009 Arboriculture & Urban Forestry 2009. 35(3): 113–121 113 Relative Growth and Water Use of Seedlings from Three Italian Quercus Species Daniel K. Struve, Francesco Ferrini, Alessio Fini, and Laura Pennati Abstract. A species’ water use characteristics and growth habits are important to urban foresters. Seedlings from three species (and two sources)—Quercus cerris L., Q. pubescens Willd., and Q. robur L.—were container-grown and subjected to a three day water use trial under nonlimiting soil moisture conditions. Water use varied among species and between sources within a species. Larger seedlings used more water than smaller seedlings; Q. robur seedlings were the tallest, 70.5 cm (27.8 in), and had the greatest water use seedling, 73.4 g (2.5 oz) water, while Q. pubescens and Q. cerris seedlings were shorter, 46 and 45 cm (18.1 and 17.7 in), and av- eraged 47.5 and 44.9 g (1.68 and 1.58 oz) water, respectively. Quercus pubescens seedlings had the highest water use cm-2 (0.111 g); Q. cerris seedlings had the highest height-adjusted water use (1.4 g water cm-1 leaf area height). There were significant differences in water use between sources within species. Principal component analysis, using 20 variables, showed that seedlings of Q. robur and Q. pubescens sources clustered while seedlings of the two Q. cerris sources were separate from each other and the Q. robur and Q. pubescens sources. The clustering reflected the proportionally greater distribution of dry weight to shoot growth and correspondingly less to root growth of the Q. robur and Q. pubescens seedlings, than that for Q. cerris seedlings. The results are related to the species’ relative value to nursery producers and to the potential value to urban forest managers and the potential for cultivar development. Key Words. Drought Resistance; Dry Weight Partitioning; Seedling Growth; Water Use. The urban environment is stressful. Tree growth and survival are limited by edaphic factors such as soil moisture, essential min- eral nutrients, high pH and compaction, temperature extremes, light, airborne pollution, and mechanical injury (Fini and Fer- rini 2007). A species’ growth rate, drought resistance, and water use are important characteristics to urban forest managers. Oaks are adapted to various sites (from wet and humid floodplains to mesic uplands and xeric forests (Johnson et al. 2002) and thus are potential candidates for planting in the urban forest. Oaks (Quercus sp.) as a species are generally considered drought re- sistant (Abrams 1990), with drought resistance being conferred by a combination of drought avoidance and tolerance mecha- nisms (Abrams 1990). Three common Italian oak species— Quercus cerris L., Q. robur L., and Q. pubescens (Willd.)—are the subject of this study. Quercus robur has the greatest potential size, followed by Q. cerris and Q. pubescens (Krussman 1986). In European forests, the genetic complex of Quercus robur, Q. petraea, and Q. pubescens occupy a continuum of mesic-to- xeric sites with Q. cerris occupying more xeric sites. The authors are unaware of any study that compares the relative drought resistance among these three species. However, Q. robur is considered the least and Q. pubescens the most drought resis- tant species (Fineschi et al. 2002). Quercus pubescens drought resistance is attributed to both drought avoidance and tolerance mechanisms. Under drought conditions, Quercus pubescens trees express drought avoidance traits such as: maintenance of hy- draulic conductivity and high relative leaf moisture content, high assimilation rates and stomatal conductance, and low water use efficiency, attributed to a deep root system that allows access to subsurface soil moisture (Damesin and Rambal 1995; Damesin et al. 1997; Damesin et al. 1998; Nardini et al. 1998; Nardini and Pitt 1999; Lo Gullo et al. 2003; Mediavilla and Escudero 2004; Fotelli et al. 2005; Poyatos et al. 2005; Zweifel et al. 2005; Zweifel et al. 2006). Under extreme drought, Q. pubescens trees close their stomata as predawn leaf moisture potentials decrease (Damesin and Rambal 1995; Tognetti et al. 1999), and can shed leaves and limit the current season’s shoot growth to avoid desic- cation (Nardini and Pitt 1999; Lo Gullo et al. 2003). Quercus pu- bescens also expresses drought tolerance by a rapidly increasing its leaf water potential and leaf conductance following drought relief (Tognetti et al. 1999; Galle et al. 2007). Quercus robur and Q. petraea also respond to drought using both drought avoidance and tolerance mechanisms. However, because of higher water use efficiency, Q. petraea seedlings are considered better adapted to xeric sites (Epron and Dreyer 1993). Under nonlimiting soil moisture conditions, Q. robur seedlings have a faster growth rate, but under drought they have lower rates of assimilation and stomatal conductance than Q. petraea seedlings (Steudle and Meshcheryakov 1996; Ponton et al. 2002; Gieger and Thomas 2005). Although Q. robur seedlings are not as drought resistant as Q. petraea seedlings, their quicker recovery from drought was considered an expression of greater drought tolerance. Less studied is Q. cerris’ physiological response to drought. It is considered a mesophile species (D’Alessandro et al. 2006). It expressed less stomatal control than the xeric-adapted Fraxinus ornus during a summer drought indicative of deep root access to subsurface soil moisture (D’Alessandro et al. 2006). One study compared Q. cerris and Q. pubescens seasonal water use (Valen- tini et al. 1992). Both species relied on ground water (as opposed to surface soil moisture) during a summer drought, with Q. pube- scens being more water conserving than Q. cerris. Another study compared Q. petraea and Q. cerris sap flow and cavitation. Quer- ©2009 International Society of Arboriculture
May 2009
| 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
