Journal of Forestry Research (2014) 25(4): 827−834 DOI 10.1007/s11676-014-0530-6 ORIGINAL PAPER Growth characteristics and reproductive output of dwarf mistletoe- infected Juniperus polycarpos in Iran Abolfazl Daneshvar • Mulualem Tigabu • Asaddollah Karimidoost Mostafa Farhadi • Per Christer Odén Received: 2013-04-01; Accepted: 2013-04-14 © Northeast Forestry University and Springer-Verlag Berlin Heidelberg 2014 Abstract: Dwarf mistletoes are parasitic flowering plants that infect germination capacity. We conclude that reproductive output of J. poly- conifers, resulting in substantial loss of growth and mortality. Recently, carpos is more sensitive than growth characters to moderate infection by forest managers in Iran are contemplating whether infection of Juniperus juniper dwarf mistletoe, and this might partly account for poor natural polycarpos C. Koch forests by dwarf mistletoe, Arceuthobium oxycedri regeneration. (DC.) M. Bieb, influences tree vigor and contributes to insufficient Keywords: conifers, Greek juniper, forest health, parasitic plant, seed natural regeneration. The present study aimed at assessing the severity of size infection and its impact on growth and reproductive output of J. polycar- pos. Infected and uninfected trees (n =20 each) were selected for assess- ment of diameter, height, crown area, and crown volume as well as Introduction quantity and quality of cones and seeds. The severity of infection of trees was determined by Hawksworth’s 6-class dwarf mistletoe rating (DMR) The genus Juniperus (Cupressaceae) consists of approximately system. The DMR system revealed that 40% of the infected sample trees 67 species that are mostly distributed over the northern hemi- were lightly infected (DMR =1−2) and 60% were moderately infected sphere and Africa (Farjon 2005). Juniperus polycarpos C. Koch (DMR =3−4). Growth characteristics did not differ significantly (p > is one of six native juniper species in Iran that are naturally 0.05) between infected and uninfected trees. However, moderate infec- distributed along the southern slopes of the Alborz mountain tion affected the reproductive output of J. polycarpos by significantly (p chain, Arassbaran, and Northern part of Khorasan (Korouri et al. <0.05) reducing the mean number of cones per unit area of the crown, 2012). The juniper forest is highly valued for its economic and increasing the number of damaged seeds, and reducing seed size and seed ecological importance: the wood is suitable for manufacturing of pencils; the essential oil is used in several pharmaceutical prepa- rations and for traditional treatment of various diseases (Akkol et Project funding: This study was supported by the Iran Government al. 2009). Juniper forest also provides habitats for wildlife and Science and Technology Scholarship Program. protection against soil erosion (Korouri et al. 2012). Although The online version is available at http://www.springerlink.com commercial harvesting of J. polycarpos in Iran has been prohib- Abolfazl Daneshvar1,2, Mulualem Tigabu1, ( ), Mostafa Farhadi1 ited since 1989, the population size of juniper forests continues Per Christer Odén1 to decline due to illegal cutting and overgrazing as well as insuf- 1 Swedish University of Agricultural Sciences, Southern Swedish ficient natural regeneration due to poor seed production (Ahani Forest Research Centre, P.O Box 49, SE-230 53, Alnarp, Sweden. 2 et al. 2013). Recently, forest managers are contemplating permanent address: Department of Natural Resources, Gonbad Kavous whether infection of juniper forests by dwarf mistletoe, particu- University, Shahid Fallahi Street, POBOX: 163, Gonbad, Iran. Email: larly at elevations from 1800 to 2700 m.a.s.l., influences tree [email protected]. vigor and reproductive output, thereby contributing to insuffi- cient natural regeneration of juniper forests in Iran. Asaddollah Karimidoost Dwarf mistletoes are parasitic flowering plants that infect Agriculture and Natural Resources Research Center of Golestan Prov- conifers, producing characteristic yellow to orange or green to ince, Beheshti Ave. PO Box 4915677555, Gorgan, IRAN. brown leafless aerial shoots on the host plant. The dwarf mistle- [email protected] toe associated with juniper (hereafter referred to as juniper dwarf mistletoe) is Arceuthobium oxycedri (DC.) M. Bieb, Viscaceae, Corresponding editor: Hu Yanbo which has a wide geographic distribution, ranging from North 828 Journal of Forestry Research (2014) 25(4): 827−834 Africa, Southern Europe to Central and Western Asia as far as northeastern Iran, and their growth characteristics were measured. near East and Western China (Hawksworth and Weins 1996; The severity of dwarf mistletoe infection was assessed using Sarangzai et al. 2010). Dwarf mistletoes depend on their host Hawksworth’s six-class dwarf mistletoe rating system (Hawk- trees for their nutrients and water. Infections cause branch swell- sworth 1977) coupled with quantitative estimate of the dwarf ing, reduced growth, dieback, and abnormal proliferation of host mistletoe colonies and witches’ brooms. The number of cones branches known as “witches’ brooms”, all of which vary with produced by each tree was assessed using the frame method infection severity and the vigor of the host. Generally, severe (Lamien et al. 2006), and cones were collected for characteriza- infection is associated with growth loss and mortality (Geils and tion of cone and seed characters. Hawksworth 2002; Stanton 2006; Scott and Mathiasen 2012), alteration of physiological processes of the hosts (Glatzel and Geils 2009) and predisposition of host trees to other pests (Ke- Materials and methods naley et al. 2006) and climate factors (Stanton 2007). Impacts of infection by dwarf mistletoe on the reproductive Study site outputs (cone production, seed quantity and quality, and seedling survival) of its coniferous hosts in general have not been a sub- The study was conducted in a J. polycarpos stand at Chaharbagh ject of many studies (Geils and Hawksworth 2002). To our in northeastern Iran, located between 36° 36´−36° 41´ N and 54° knowledge, no detailed studies have been carried out regarding 28´−54° 35´ E at an elevation range of 2150−3150 m a.s.l. (Fig. the extent of damage incurred by dwarf mistletoe on J. polycar- 1). The climate is characterized as semi-dry with average annual pos. Such information is useful for forest managers who rely on precipitation of 305 mm, which appears mostly in the form of natural regeneration to mitigate the damage to juniper forests that snow. The study area has cold winters and moderately warm results from infection of this dwarf mistletoe. Thus, the main summers with the minimum temperature (-14°C) occurring in objective of the study was to investigate the effect of juniper December and the maximum (31°C) in July. Relative humidity dwarf mistletoe infection on growth characteristics and reproduc- varies during the year from 46% to 69.9%, the frost period is 120 tive output of its host, J. polycarpos. The specific research ques- days, starts in November and continues until February. The site tions addressed were: (1) How severe is dwarf mistletoe infec- has shallow sandy soils (45−71.8% sand, 8.3−26.6% clay, tion and to what extent has this infection influenced growth 19.8−28.4% silt, pH 8.3 and electrical conductivity 0.15−0.18) characteristics of J. polycarpos? (2) Does infection by dwarf with stone outcrops and is prone to low nutrient availability mistletoe reduce cone production, seed quality or seed quantity? (Korouri et al. 2012). To answer these questions, infected and uninfected trees (n = 20 each) were sampled in J. polycarpos stands at Chaharbagh, Fig. 1: Geographic distribution of J. polycarpos and J. excelsa and location of the study area, Charbagh, Golestan province, Iran. cones. Near every infected tree, one uninfected tree with compa- Sample tree selection rable growth characteristics and morphological features was chosen as a control. As we were interested to evaluate stress A total of 40 sample trees (n = 20 for infected and uninfected reactions only from dwarf mistletoe infection, thereby avoiding trees each) in the same altitudinal range were marked for subse- potential confounding effects of other factors on cone and seed quent assessment of dwarf mistletoe infection and collection of characters, trees free from decay in the trunk, pest attack, dis- Journal of Forestry Research (2014) 25(4): 827−834 829 eases and other environmental stresses were judiciously selected with a DMR of 5 to 6 were considered heavily infected (Hawk- as controls. sworth 1977). Presence of infection was most easily determined from the ground by the presence of witches’ broom-like growth. Assessment of dwarf mistletoe infection Mistletoe brooms are infected host branches with excessive branching and shortened/lengthened internodes. The severity of a dwarf mistletoe-infected tree was assessed To get a quantitative estimate of the infection level, the num- using dwarf mistletoe rating (DMR) system, where ratings ber of witches’ brooms was also counted in each vertical third of ranged from 0 to 6 (Hawksworth 1977). With this method, the the crown. In addition, the numbers of dwarf mistletoe colonies tree crown was first divided into three parts (Fig. 2), and the were counted in the middle part of the crown along the four sides severity of infection in each third was rated as 0 if there was no of the crown (north, south, east and west) using 1 m × 1 m visible dwarf mistletoe infection, 1 if less than half of the wooden-frame mounted on a long pole (Fig. 2). This frame branches were infected or 2 if more than half of the branches method is commonly applied in flower and fruit assessment were infected. Ratings for each third of the crown were then (Lamien et al. 2006). The middle part of the crown was selected summed to obtain a DMR for the whole tree. Finally, trees with a as point of assessment because most cones and dwarf mistletoe DMR of 1 to 2 were considered lightly infected, trees with a colonies appear around this part of the crown of J.