EUROPEAN ASH HEALTH CONDITION IN THE FOREST-STEPPE PART OF SUMY REGION 1

Average health condition index of European ash (Fraxinus excelsior L.) in inspected stands of the State Enterprise “Trostyanetske Forest Economy” is 2 points. European ash mortality was the highest in Krasnyanske forestry (0.8 % and 3.5 % of recently died trees and the trees died over a year ago respectively). The highest proportion of healthy European ash trees were inspected in Makivske and Krasnyanske forestries (85.3 % and 50.1 % respectively). The trees of European ash of the 1 st category of health condition can be reliably distinguished from the trees of other categories of health condition. A total score of “0” for all parameters of health condition (defoliation, dieback, and epicormic shoots occurrence) reliably points the healthy tree. The trees can be assigned to the 1 st category of health condition with defoliation, caused by insects, up to 50 %, with up to 10 % dry branches and single epicormic shoots. Multiple epicormic shoots are characteristic for the trees of the 3 rd category of health condition. Ambiguous results in distinguishing of European ash trees of the 2 nd and the 3 rd , the 3 rd and the 4 th categories of health condition confirm the need for improvement of its assessment and annual monitoring the forest health at key plots.

Materials and Methods.Survey of 62 forest plots with European ash participation was carried out in 2018 in Neskuchanske, Lytovske, Makivske and Krasnyanske forestries of the State Enterprise "Trostyanets Forest Economy" (SE "Trostyanets FE") (Table 1).The survey covered 1529 trees of European ash of 5-110 years old in the stands with 0.6-0.8relative density of stocking and 2-8 units of European ash in forest composition.
In each forest plot, 2-4 subplots of 10×10 m were inspected.The number of plots depended on European ash presence.We tried to assess not less than 25 European ash trees per plot but in inspected stands of Makivske forestry, there were rather few ash trees.
Stand age was not uniform in most of the plots because ashes of vegetative origin and seed specimens of different age were presented.Therefore, we considered the diameter at breast height as a more reliable parameter.Mean ash tree diameter was almost similar in all inspected forestries except Makivske one (see Table 2).
Occurrence (incidence) of each type of damage was evaluated as the proportion of trees with respective symptoms or signs.
The severity of each type of damage as well as tree health condition was estimated using respective scores.
Category of the health condition of European ash was evaluated on a range of visual characteristics (crown density and color, the presence and proportion of dead branches in the crown, etc.) according to "Sanitary rules in the forests of Ukraine" (Sanitary rules 1995).Each tree was referred to one of six categories of health condition (1 sthealthy; 2 ndweakened; 3 rdseverely weakened; 4 thdrying up; 5 threcently died; 6 thdied over a year ago).Health condition index (HCI) for forest stand was calculated as mean weighted from trees number of each category of health condition.
The statistical analyses were carried out using software MS Excel, particularly for descriptive statistics, analysis of variance (ANOVA) as well as a correlation between particular parameters of tree health condition (Atramentova & Utevskaya 2008).
Results and Discussion.According to the "Sanitary rules in the forests of Ukraine", the European ash stands in the SE "Trostyanetske FE" are weakened (Fig. 1).Health condition index of European ash stands, considering all trees (living and dead ones), was 2 points for the whole forest enterprise and for Neskuchanske forestry.It was the highest (2.2 points) for Lytovske forestry and the lowest (1.2 points) for Makivske forestry with the youngest ash stands.Forest health index for living trees was a bit smaller than for all trees in the forestries with European ash mortality.As mortality rate of European ash trees was rather low, therefore forest health index for all trees and for living trees differed slightly, except Krasnyanske forestry, where ash mortality was 4.3 % (0.8 % and 3.5 % of recently died trees and the trees died over a year ago) (Fig. 2).

Fig. 1 -Forest health index (FHI) for all European ash trees I 1-6 , living European ash trees I 1-4 and sum of
European ash trees of the 5 th and 6 th categories of health condition in different forestries of SE "Trostyanetske FE" The highest proportion of healthy European ash trees were inspected in Makivske and Krasnyanske forestries (85.3 % and 50.1 % respectively).The number of trees of the 2 nd and 3 rd categories of health condition was rather low as well as the total number of ash trees in inspected plots of Makivske forestry (see Table 1).In Krasnyanske and Neskuchanske forestries the proportion of European ash trees decreased with an increase of forest health category, however, in Lytovske forestry such proportion increased from 21 % of healthy trees to 42.3 % of severely weakened trees (see Fig. 2).
Our analysis shows that ash defoliation has a trend to increase with the category of health condition (Fig. 3).However, different defoliation may be found for each category of health condition.A significant difference was revealed between defoliation score for the ash trees of the 1 st category of health condition on the one side and the trees of the 2 nd , 3 rd or 4 th category of health condition on another side (p < 0.001).At the same time, the difference of defoliation score between the ash trees of the 2 nd category of health condition on the one side and the trees of the 3 rd category of health condition on another side was not significant (p > 0.1).Such difference between ash trees of 2 nd and 4 th or between 3 rd and 4 th health condition categories was significant only at p < 0.01.
The score of ash dieback has a trend to increase with the category of health condition (Fig. 4).However, different dieback scores may be found for each category of health condition.A significant difference was observed between dieback score for the ash trees of the 1 st category of health condition on the one side and the trees of the 2 nd -4 th categories of health condition on another side, as well as between each other pair of categories (p < 0.001).At the same time, ash trees with 0-1 dieback score were found for each category of health condition, with 0-2 dieback score for 2 nd -4 th categories, and with 2-3 dieback score for 3 rd -4 th categories of health condition (see Fig. 4).In our research, the epicormic shoots' occurrence takes the values "0" and "1" for any category of health condition, and the values from "0" to "2" for the 3 rd category of health condition (Fig. 5).Epicormic shoots development in the ash trees of the 3 rd category of health condition is crucial for determining the fate of a tree, which can become "drying up" or recover to "weakened" or "healthy" category.
From the database of field assessment for European ash health condition, the score values of defoliation, dieback and epicormic shoots occurrence were determined for each category of living trees health condition (Table 2).
The scores "2"-"4" for defoliation may be characteristic for European ash trees of the 2 nd , 3 rd and 4 th categories of health condition.The scores of dieback can be "0" for the trees of the 1 st , 2 nd and 3 rd categories of health condition.It can be "1" for all health condition of living ash trees, be "2" for the trees of the 2 nd , 3 rd and 4 th categories of health condition, and be "3" for the trees of the 3 rd and 4 th categories of health condition.
Both the absence of epicormic shoots and single epicormic shoots can be present on the living ash trees of each health condition but multiple epicormic shoots are characteristic mainly for the trees of the 3 rd category of health condition.The tree which is not able to recover by forming secondary crown has a trend to become drying up and then die.Therefore, 82 combinations of scores are possible for defoliation, dieback and epicormic shoots occurrence: 10 combinations for the 1 st category, 18 for the 2 nd and the 4 th categories and 36 for the 3 rd category of health condition.Any combination with the total score "0" or "1" is characteristic only for the trees of the 1 st category as well as total score "2" with "0" for any one parameter.At the same time total score "2" with "2" points for defoliation and "0" points for other parameters is characteristic only for the trees of the 2 nd category of health condition.
The total score "5" or "6" is characteristic for the trees of the 2 nd , 3 rd and 4 th categories of health condition, and the total score "7" only for the trees of the 3 rd category of health condition.
Total score distribution of European ash health condition calculated for inspected plots of SE "Trostyanets FE" shows the largest mean and mode values for Krasnyanske forestry and the lowest values for Makivske forestry (Table 3).However, some trees in all forestries were rated by the total score "4" points, in all forestries, except Makivske, the total score exceeded "4" points, and in Krasnyanske forestry several trees were rated even "7" points.Such ambiguous results confirm the need for a differentiated assessment of European ash health condition and annual monitoring at key plots.
Conclusions.Average health condition index of inspected European ash stands is 2 points.It is the highest (2.2 points) for Lytovske forestry and the lowest (1.2 points) for Makivske forestry.European ash mortality was the highest in Krasnyanske forestry (4,3 %).The highest proportion of healthy European ash trees were inspected in Makivske and Krasnyanske forestries (85.3 % and 50.1 %, respectively).
The trees of European ash of the 1 st category of health condition can be reliably distinguished from the trees of other categories of health condition.The total score of "0" for all parameters of health condition reliably points the healthy tree.The trees of European ash can be assigned to the 1 st category of health condition with defoliation, caused by insects, up to 50 %, with up to 10 % dry branches and single epicormic shoots.Multiple epicormic shoots and the total score "7" are characteristic for the trees of the 3 rd category of health condition.

Fig. 2 -
Fig. 2 -Distribution of European ash trees by health condition categories (1-6) in different forestries of SE "Trostyanetske FE" (data on trees of 5 th and 6 th health condition are pooled)

Table 1 Plot and European ash tree numbers assessed in different forestries of the SE "Trostyanets FE"
Means followed by different letters were significantly different at the 95 % confidence level.** Figures in brackets show the smallest and largest values in each forestry.