GIS-based prediction of the foliage browsing insects ’ outbreaks in the pine stands of the SE “ Kreminske FHE ”

To improve the detection and prevention of foliage browsing insects’ outbreaks it is very important to reveal the forest plots, which are the most favorable for these pests. The aim of this research was to predict using GIS technologies the spatial dynamics of foliage browsing insects’ outbreaks in the pine stands of the State Enterprise “Kreminske FHE” (Luhansk region). Forest inventory databases of Production Association “Ukrderzhlisproekt” were analyzed for the SE “Kreminske FHE” as of 2001 and 2011. Rating of forest plots preferences for common pine sawfl y (Diprion pini L.) and European pine sawfl y (Neodiprion sertifer Geoffr.) considered the type of forest site conditions, age of stand, density of stocking, and the part of pine in the stand composition. If forest plot bordered with clear-cut, then 1 point was added to the general score of the threat. It was shown, that the area with high threat of European pine sawfl y and common pine sawfl y outbreaks for 2001– 2011 increased in the forest fund of the SE “Kreminske FHE” by 702.8 and 2004.2 hectares respectively. The part of foci area made up 27.5 and 32 % from forest fund area, 42.5 % and 49.5 % from pine stands area for European pine sawfl y and common pine sawfl y respectively. The areas of pine sawfl ies foci increased mainly in result of decrease the stocking density of pine stands and increase the number of plots which border with clear-cuts. The survey for pine sawfl ies is recommended to carry out fi rst of all in the plots with high threat of foci appearance.

To improve the detection and prevention of outbreaks development it is very important to know precisely the plots, which are the most favorable for foliage browsing insects.Methodical approach for evaluation of indivi dual plots preferences for the most spread foliage browsing insects was developed by Meshkova (2009) and tested in Kharkiv (Meshkova, 2006a(Meshkova, , 2006b)), Kherson, Luhansk (Meshkova & Kolienkina, 2016) and Zhytomyr regions of Ukraine (Andreieva, 2009).
According to this approach, a rating of forest plots preferences for the main species of foliage browsing insects was carried out considering the type of forest site conditions, age of stand, density of stocking, and the part of pine in the stand composition.Then total score of points and threat risk is calculated for each forest plot taking into account forest inventory database.The plots with maximal threat of foliage browsing insects' outbreaks are recommended for high priority fi eld inspection, and total area of such plots in the forest stand corresponds to the potential area of certain pest focus in the years of its outbreak.
In different countries GIS-approach is widely used for evaluation of forest damage by different causes, including insects, together with remote sensing and aerial survey (Bone et al., 2013, Rullan-Silva et al., 2013, Senf et al., 2017).
The maps of forest stands are plotted and connected with geographic coordinates and forest inventory database in Ukrainian Research Institute of Forestry & Forest Melioration (URIFFM).Additional fi elds can be attached with characteristics of certain insect pests' preferences, abundance, and forest damage by wind, fi re etc. (Polupan et al., 2011).Such approach gives the possibility not only to reveal the foci, but also to predict the trends in their development in time and space (Grodzki, 2005, Meshkova, 2006a, 2006b).However, the possibility of change the land category of neighboring plots was not taken into account.It is known (Meshkova, 2009), that the risk of foliage browsing insects outbreaks increases, if forested neighboring plots are converted to clear-cuts, burnt area, roads or another categories of the lands, which are not covered with forest.Infl uence of land category change on spread of foliage browsing insects' foci can be taken in to account with the help of GIS applications.A similar approach was developed for assessment the level of fi re threat (Polupan et al., 2011) and gave the possibility to build respective thematic maps, to obtain the lists of forest plots with high fi re risk and respective area, to plan the necessary preventive measures, as well as to improve the algorithm for optimal mobility of vehicles in the case of forest fi res.
The using of GIS approaches gives the possibility also to improve the prediction of foliage browsing insects spread for the cases of change the forest age, species composition or stocking density (Meshkova & Kolienkina, 2016).
The State Enterprise "Kreminske Forest & Hunting Economy" (SE "Kreminske FHE", Luhansk region) was selected as model object, because of high severity, frequency and duration of foliage browsing insects outbreaks there, which strengthens by climate aridity (annual precipitation 492 mm per year, annual air temperature 8 °C) and high anthropogenic loading (Meshkova & Kolienkina, 2016).
At the beginning of XXI century the area of foliage browsing insects foci and outbreak duration increased, and intervals between outbreaks decreased, particularly from 12 to 7 years for common pine sawfl y (Diprion pini L.) and from 7 to 5 years for European pine sawfl y (Neodiprion sertifer Geoffr.)(Meshkova & Kolienkina, 2016).
The aim of this research was to predict using GIS technologies the spatial dynamics of foliage browsing insects' outbreaks in the pine stands of the State Enterprise "Kreminske FHE".
Objects and methods.Forest inventory Databases of Production Association "Ukrderzhlisproekt" were analyzed for the SE "Kreminske FHE" as of 2001 and 2011.These databases were converted into Access and Excel tables using applications developed in URIFFM.
The foci of two foliage browsing insects of pine stands -common pine sawfl y (Diprion pini L.) and European pine sawfl y (Neodiprion sertifer Geoffr.) were analyzed as the most spread forest pests in the region (Meshkova & Kolienkina, 2016).
The threat of pine sawfl ies spread in the pine forests of SE "Kreminske FHE" was evaluated using approach of Meshkova (2009).According to it each plot in the database was scored by the type of forest site condition, part of pine (Pinus sylvestris L.) in the forest composition, stand age, density of stocking, and then total score and threat level were evaluated.For all plots with the absence of pine the threat was evaluated as "0 points".
In the second scenario of evaluation the threat of pine sawfl ies spread, the neighboring plots were taken into account.Using QGIS 2.18, the spatial query was formed with the fulfi llment of the predicates of neighborhood, affi liation and adjoining.So if forest plot bordered with clear-cut, then 1 point was added to the general score of the threat.
Thus total area with the threat of pine sawfl ies outbreaks was evaluated for forest fund of the SE "Kreminske FHE" by three levels: low, moderate and high.Thematic maps on common pine sawfl y and European pine sawfl y foci distribution were built using QGIS 2.18 for the whole territory of forest fund.Here we show only the maps for Serebryanske forestry by the variants: as of 2001 without considering land category of neighboring plots; as of 2001 with considering the land category of neighboring plots; as of 2011 without considering land category of neighboring plots; as of 2011 with considering the land category of neighboring plots.
Results and discussion.Data analysis shows that the area of forest stands in the SE "Kreminske FHE" increased from 41401.5 hectares in 2001 to 41503.8 hectares in 2011.The area of pine stands increased from 26340.4 to 26827.8 hectares, and the part of pine stands in forest fund increased from 63.6 to 64.6 % (Table 1).According to this, the area of stands available for pine sawfl ies outbreaks increased.
The area of stands with high threat for European pine sawfl y outbreak increased from 10701.7 hectares in 2001 to 11404.5 hectares in 2011 (by 702.8 hectares), and that for common pine sawfl y increased from 11266.5 hectares in 2001 to 13270.7 hectares in 2011 (by 2004.2 hectares).The part of European pine sawfl y foci area from forest fund area increased for this period from 25.8 to 27.5 %, and the part of common pine sawfl y foci area -from 27.2 to 32 %.The part of European pine sawfl y foci area from pine stands area increased from 40.6 to 42.5 %, and the part of common pine sawfl y foci area -from 42.8 to 49.5 % (see Table 1).More intensive growth of common pine sawfl y foci area, than European pine sawfl y foci area, is explained by greater photophilia of the fi rst species.It prefers the plots with lower relative density of stocking.Therefore if we consider only the change of relative density of stocking, we can calculate, that the area with the high threat of outbreaks increased for 2001-2011 from 853.5 to 2576 ha, and its part from all predicted foci area (with low, moderate and high threat) increased from 3.2 to 9.6 % (Fig. 1).
The change of land category of neighboring plots also contributes to the growth of pine sawfl y foci area.So with considering the land category of neighboring plots in 2001 the area of European pine sawfl y and common pine sawfl y foci was by 327.7 and 242.3 hectares larger respectively, than without considering the land category of neighboring plots.In 2011 respective difference was 167.4 and 263.2 hectares for European pine sawfl y and common pine sawfl y foci respectively (see Table 1).
For 2001-2011 the area of pine stands with high threat of European pine sawfl y and common pine sawfl y foci, evaluated considering land category of neighboring plots, increased by 542.5 and 2025.1 hectares respectively (see Table 1).
The trend of growth the pine sawfl ies foci in connection with decrease of stocking density of stands and increase of number of plots, which border with clear-cuts, was supported also for individual forestries of SE "Kreminske FHE", particularly for Serebryanske forestry (Fig. 2-4).The area of pine stands in Serebryanske forestry with high threat of European pine sawfl y foci, evaluated by 2011 database, exceeded 209 and 261.1 hectares such area evaluated by 2001 database, and for common sawfl y by 416.5 and 448.9 hectares in the cases without considering neighboring plots and with such considering.
It is necessary to carry out the survey and assessment of pine sawfl ies fi rst of all in these plots.Considering these data gives the possibility to reduce the costs both on forest inspection and on forest treatment with insecticides.Due to greater photophilia of common pine sawfl y it is more sensitive not only to decrease of stocking density, but also to appearance of clear-cuts in the neighboring plots (Meshkova, 2009).
As the area of pine stands in Serebryanske forestry was 2627.5 and 2688.1 hectares in 2001 and 2011, the part of area with the highest threat of European pine sawfl y foci from pine stands area increased from 30.3 to 39.3 %, and the part of area with the highest threat of common pine sawfl y foci from pine stands area increased from 42.3 to 58 %.
Obtained data show, that total treatment of all pine forests with insecticides is inexpedient, because potential area of European pine sawfl y foci cannot exceed 39.3 % of pine stands area, and such area for common pine sawfl y cannot exceed 58 % of pine stands area.Considering these data gives the possibility to reduce the costs on insecticide treatment and negative infl uence of forest ecosystem.
Conclusions.Rating of forest plots by preferences for foliage browsing insects show, that in the forest fund of the SE "Kreminske FHE" the area with high threat of European pine sawfl y and common pine sawfl y outbreaks for 2001-2011 increased by 702.8 and 2004.2 hectares respectively.
The part of foci area made up 27.5 and 32 % from forest fund area, 42.5 % and 49.5 % from pine stands area for European pine sawfl y and common pine sawfl y respectively.
The areas of pine sawfl ies foci increased mainly in result of decrease the stocking density of pine stands and increase the number of plots which border with clear-cuts.
On example of Serebryanske forestry it was evaluated, that the area of pine stands with high threat of European pine sawfl y outbreak increased for 2001-2011 by 209 and 261.1 hectares, and such area for common pine sawfl y by 416.5 and 448.9 hectares respectively in the cases without considering neighboring plots and with their considering.

Fig. 1 .
Fig. 1.Distribution of pine sawfl ies foci area in SE "Kreminske FHE" by threat level with considering the change of stocking density for 2001-2011 (H -high threat: M -moderate threat; L -low threat)

Fig. 2 .
Fig. 2. Area of European pine sawfl y and common pine sawfl y foci in Serebryanske forestry of SE "Kreminske FHE", evaluated by forest inventory databases for 2001 and 2011 without considering the land category of neighboring plots (N0) and with considering the land category of neighboring plots (N1)

Fig. 4 .
Fig. 4. Distribution of predicted common pine sawfl y foci area in Serebryanske forestry of SE "Kreminske FHE" (upper row -as of 2001, lower row -as of 2011; in every row left map is built without considering land category of neighboring plots; right map is built with considering the land category of neighboring plots)