Infestation of Common Mistletoe and Nutrition Status of Silver Fir in Gorski Kotar (Croatia)

• Main Authors: Danko Diminić, Anamarija Jazbec, Nenad Potočić, Miljenko Županić
• Format: Article
• Language: English
• Published: University of Zagreb, Faculty of Forestry 2011-01-01
• Series: Croatian Journal of Forest Engineering
• Online Access: https://hrcak.srce.hr/file/101763
• ISSN: 1845-5719; 1848-9672

In the region of Gorski Kotar 6 sites (localities) of Silver fir (Abies alba Mill.) were selected to investigate the health status of trees, the infestation by common mistletoe (Viscum album L. ssp. abietis /Wiesb./ Abromeit), and to reveal the nutrition status of fir trees and mistletoes. Three localities were selected on soil sub-types based on silicate and three on limestone-dolomite (Table 1). In the period 2003–2005, from the end of September to the beginning of November, 15 fir trees were randomly selected on each site and evaluated according to crown defoliation with a 5% precision using the criteria and methods of UN/ECE ICP Forests. The diameter of the selected trees was measured at breast height. The trees height and their age on stumps were determined after felling. The crowns were examined in detail; the mistletoes were removed and counted to reveal the number of parasitic plants, and weighed to obtain their crown biomass per each site (Tables 2–7). This paper presents the analyses of 90 trees in total. Samples of fir needles and mistletoe leaves were collected for nutrition analyses from the upper 1/3 of the crown. Needle samples (1- and 2-year old) were dried at 105°C, weighed, and analyzed for the total amount of nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese and zinc. In total, the results are given of the analyses of 180 needles and 17 mistletoe samples. In October 2008 the repeated collection of needle samples was carried out on the same sites in 5 fir trees of a good vitality with crown defoliation <25%. Each site was represented by a composite sample of 1- and 2-year old needles. The same procedure was performed to analyze samples. Soil samples were also taken as composite samples for each site from two soil depths 0–30 and 30–60 cm, using the Holland drill. Standardized soil analyses were performed to obtain the total nitrogen, plant available phosphorus and potassium, and for the determination of pH. Descriptive statistics was made for all analyzed variables. For all tests, the error of type I (a) of 5% was considered as significant difference. Statistical analyses of variables were performed as follows: • one factor analysis of variance for number of mistletoes and mistletoe biomass according to locality and soil sub-type, • two factor analysis of variance for concentration of elements in fir needles and mistletoe leaves according to soil sub-types, • repeated measures analysis of variance for concentration of elements in fir needles according to soil sub-types and needles age, • repeated measures analysis of variance for chemical analyses of two soil sub-types and two soil depths (0–30, 30–60 cm) (Sokal and Rohlf 1995). Statistical analyses and graphics were done using the software STATISTICA 7.1 (StatSoft, Inc. 2010). The research revealed differences in fir trees with mistletoe infestation. Fig. 1 and 2, and Table 8 show the results of statistical analyses of the number of mistletoes and their biomass in fir crowns. The differences revealed between localities are not statistically significant. These results also confirmed previously published data (Diminić i Kauzlarić 2006) that with the increment of crown defoliation the number of mistletoes and their biomass increase in fir trees as well. The general picture of infestation, comparing the sites on two soil sub-types, revealed slightly more infested trees on limestone-dolomite, in number and mistletoe biomass. However, during our research the most infested firs revealed 417, 421 and 491 mistletoes in the trees grown on silicate soils, while in trees on limestone-dolomite soils the most infested firs revealed 205, 303 and 364 mistletoes. According to biomass, the most affected fir had 52.4 kg of mistletoes in the tree on silicate soil, and 52.3 kg in the tree on limestone-dolomite soil. Statistical analyses of data on nutrition status in firs and mistletoes revealed no significant difference generally, although some trends could be seen (Fig. 5, Table 9). Significant difference was obtained by comparing fir needles and mistletoe leaves in N, P, K and Zn, which was expected as two different plant organisms were compared. In the case of other elements no significant difference was found. The same result was obtained in two different soil sub-types, except in phosphorous concentrations (Fig. 5, Table 9). The nutrition status of mistletoe expectedly followed nutrition status of its host, and the differences in concentration of elements according to type of substratum (soil sub-type) were almost identical in needles and mistletoe leaves, with respect to differences in absolute values. Comparing the limited values with average values of a single analyzed element according to the soil sub-type, concentrations of nitrogen in fir trees were not adequate on limestone-dolomite but they were adequate on silicate. Phosphorous concentrations were not adequate, neither on limestone-dolomite nor on silicate, which correlates to the low contents in the sampled soils. Concentrations of potassium were adequate on both soil sub-types, and calcium and magnesium optimal. Analyses of 1- and 2-year old fir needles (repeated sampling) revealed similar results (Fig. 6, Table 10). The differences among results in nutrition status of 15 and 5 sampled trees were not significant, and they can be explained by annual fluctuations. Analyses of soil samples of two soil sub-types revealed the expected significant statistical difference in pH, where soils on silicate had lower reaction. Analyses of total nitrogen, plant available phosphorus and potassium in the soils revealed no significant difference (Fig. 7, Table 11). The research on fir trees with mistletoe infestation in the region of Gorski Kotar revealed some facts. Intense infestation was found in five of six investigated sites, intensity of mistletoes presence as well as their biomass in fir crowns correlated to crown defoliation, and the nutrition status of mistletoe expectedly followed nutrition status of its host, with respect to differences in absolute values.