Tarasova O., Sukhovolsky A., Soldatov V., Sukhovolsky V. Temporal and spatial conjugacy of the development of xylophage insects outbreaks in the forests of Krasnoyarsk Region // Principy èkologii. 2019. № 3. P. 101‒122. DOI: 10.15393/j1.art.2019.9062

Issue № 3

Original research

pdf-version

Temporal and spatial conjugacy of the development of xylophage insects outbreaks in the forests of Krasnoyarsk Region

Introduction

Among the phytophagous insects that inhabit forests, most species have very low population densities, when the damage to forage plants is very rare or absent. But there is a group of species whose population size can change by 5-7 orders every few years. A large part of the forest insects with periodic changes in the number of populations refers to a group of coniferous- and leaf-eating insects and causes severe defoliation of forage plants, but rarely – their death. However, mass reproduction of coniferous- and leaf-eating insects and the weakening of the forest lead to the growth of stem pests-insects number that feed on bark and wood tissues. In Siberia, foci of stem pests are often formed after outbreaks of mass reproduction of the Dendrolimus sibiricus. Insects-stem pests accelerate the process of death of plants and stands in general.

The purpose of this work is to identify the spatial and temporal synchronization of the development of outbreaks of mass reproduction of xylophage insect species complex in the forests of the Krasnoyarsk region. This analysis is necessary to assess the risks of outbreaks and the optimization of the monitoring of xylophage insects that damage forest stands. Knowing the spatial relationship of outbreaks of a particular species of xylophage allows to assess the risk of outbreaks in other territories if a mass breeding site of this species is detected in a separate forest area. The knowledge of the temporal conjugation of the development of outbreaks of several xylophagous species in a separate forestry makes it possible to assess the risks of breeding foci of other xylophagous species when detecting outbreaks of mass reproduction of other species in this forestry.

Materials

The data on damage of forest plantations and information on forest pests were collected during ground surveys of current forest pathology forest plantations by the Center of forest protection of the Krasnoyarsk region in various forest areas during 2007-2015. In the process of forest pathology survey, the boundaries of forest damage, the accounting of the number of pests, assessment of insect damage to forest stands was carried out. The pathological examination of forests inhabited by stem pests was carried out by employees by visual inspection of weakened areas of the forest. The population of plantations with stem pests was estimated by the presence of shrunken and shrinking trees, by the withering of needles in the crown, the presence of drill flour on the bark, crawling beetles, and entrance and exit holes. An area where the number of trees inhabited by stem pests exceeds 10 % is considered to be a source of stem pests (Лесная энтомология, 2010).

In the course of forest pathology surveys in the forest Fund of the Krasnoyarsk territory, foci of mass reproduction of 15 species of xylophages were found, in particular such species of stem pests as Dicerca aenea L., Melanophila guttulata Gebl. (Coleoptera, Buprestidae), Monochamus urussovi Fisch., Monochamus sutor L., Monochamus galloprovincialis Ol., Saperda carcharias L. (Coleoptera, Cerambycidae), Xylechinus pilosus Ratz., Tomicus minor Hartig., Tomicus piniperda L., Dendroctonus micans Kug., Polygraphus proximus Blandf., Scolytus ratzeburgi Jans., Ips sexdentatus Boern., Ips subelongatus Motsch. Ips typographus L. (Coleoptera, Scolytidae).

In table. 1 the data on the area of stem pest foci in forest stands in the territory of forest districts of the Krasnoyarsk territory (unpublished materials of the annual reports of the forest protection Center Krasnoyarsk region) is shown.

 

Table 1. Areas (ha) of damage to forest stands by insects-xylophages in the territory of Krasnoyarsk Region

 

№	Species of insect- xylophages	Forestry	Areas (ha) of insects-xylophages damage foci by years
			2007	2008	2009	2010	2011	2012	2013	2014
1	Polygraphus proximus	Achinskoye	0	0	753.5	753.5	863.5	1009.4	1681.4	984.5
2	Monochamus urussovi	Achinskoye	0	13.7	13	13	13	13	13	13
3	Monochamus urussovi	Balakhtinskoye	0	41.5	35.3	33.2	0	0	0	0
4	Tomicus piniperda	Bogotolskoye	0	0	0	54	0	0	0	0
5	Polygraphus proximus	Bogotolskoye	0	0	474.6	474.6	474.6	474.6	143.3	115.3
6	Xylechinus pilosus	Bogotolskoye	0	54	54	54	54	54	0	0
7	Monochamus urussovi	Bogotolskoye	0	373.8	350.8	350.8	350.8	350.8	25	25
8	Tomicus minor	Boguchanskoye	10	0	0	0	0	0	0	0
9	Monochamus sutor	Boguchanskoye	3	0	0	0	0	0	0	0
10	Polygraphus proximus	Bolshemurtinskoye	0	0	0	0	0	0	475	475
11	Polygraphus proximus	Bolsheuluyskoye	0	0	0	0	0	0	676.3	676.3
12	Ips subelongatus	Borskoye	50	17.5	17.5	17.5	0	0	0	0
13	Monochamus urussovi	Verhne-Manskoye	0	659	659	609	609	609	609	609
14	Ips sexdentatus	Verhne-Manskoye	20	20	66	979	979	979	933	933
15	Dicerca aenea	Gremuchinskoye	45	45	0	0	0	0	0	0
16	Ips subelongatus	Gremuchinskoye	41	41	41	5.4	5.4	188.1	78.4	30.2
17	Ips sexdentatus	Gremuchinskoye	423	213.6	213.6	213.6	213.6	213.6	213.6	213.6
18	Tomicus minor	Gremuchinskoye	298	297.8	297.8	23.1	15.2	15.2	15.2	80
19	Tomicus piniperda	Gremuchinskoye	39	25.1	25.1	0	23.1	259	121.3	48.6
20	Monochamus sutor	Gremuchinskoye	4	4	4	4	4	4	4	4
21	Melanophila guttulata	Gremuchinskoye	0	0	45	45	45	45	45	96.3
22	Saperda carcharias	Gremuchinskoye	0	0	0	0	0	35	35	12.8
23	Xylechinus pilosus	Gremuchinskoye	0	0	0	15.2	0	0	0	0
24	Monochamus urussovi	Gremuchinskoye	0	3287.4	3279.6	3241.2	3241.2	3241.2	3203.2	3203.2
25	Scolytus ratzeburgi	Dzerzhinskoye	0	0	0	0	0	0	22	0
26	Monochamus urussovi	Dzerzhinskoye	0	0	0	0	0	2	2	2
27	Tomicus minor	Divnogorskoye	16	0	0	0	0	0	0	0
28	Monochamus urussovi	Dolgomostovskoye	0	95.3	95.3	205.3	110	110	110	110
29	Ips subelongatus	Dolgomostovskoye	24	24	24	24	0	0	0	0
30	Scolytus ratzeburgi	Dolgomostovskoye	1	0.7	0.7	0.7	0	0	0	0
31	Polygraphus proximus	Emelyanovskoye	0	0	0	0	0	0	109.2	1785
32	Monochamus urussovi	Eniseyskoye	0	10081	10144	1711	2227	2227	831	831
33	Monochamus urussovi	Ermakovskoye	0	3280.4	3280.4	3280.4	3280.4	3280.4	3140	3140
34	Ips sexdentatus	Irbeyskoye	206	206	206	206	206	206	206	206
35	Tomicus piniperda	Irbeyskoye	21	21	21	0	21	12	12	12
36	Tomicus minor	Irbeyskoye	0	0	0	21	0	0	0	0
37	Monochamus urussovi	Irbeyskoye	0	35508	35508	35508	35508	27250	26520	0
38	Monochamus urussovi	Kazachinskoye	0	7750	150	150	0	0	0	0
39	Ips sexdentatus	Karatuzskoye	0	0	0	0	0	295	295	295
40	Monochamus urussovi	Karatuzskoye	0	4065	4065	3434	3434	3567	1732	1732
41	Ips sexdentatus	Kizirskoye	0	0	0	5.8	5.8	5.8	5.8	5.8
42	Monochamus urussovi	Kizirskoye	0	798	2961.1	2669.3	2650.9	2496.2	2496.2	2048.2
43	Ips subelongatus	Kodinskoye	84	84	84	84	84	84	84	84
44	Ips sexdentatus	Kodinskoye	31	23.4	23.4	23.4	23.4	23.4	23.4	23.4
45	Tomicus piniperda	Kodinskoye	1580	1580	1580	0	1580	1580	1580	1529.8
46	Scolytus ratzeburgi	Kodinskoye	0	92	92	92	92	92	92	92
47	Dicerca aenea	Kodinskoye	0	360	0	0	0	0	0	0
48	Melanophila guttulata	Kodinskoye	0	0	360	360	360	360	360	360
49	Tomicus minor	Kodinskoye	0	0	0	1580	0	0	21.2	21.2
50	Monochamus urussovi	Kodinskoye	0	2391	2391	2391	2391	2391	2293	2578.9
51	Polygraphus proximus	Kozulskoye	0	0	724.5	884.2	887.5	505.4	1196.3	1174.6
52	Monochamus urussovi	Kozulskoye	0	3.9	3.9	3.9	3.9	3.9	0	0
53	Tomicus minor	Krasnoyarskoye	30	0	0	0	0	0	0	0
54	Tomicus piniperda	Krasnoyarskoye	17	0	0	0	0	0	0	0
55	Polygraphus proximus	Krasnoyarskoye	0	0	0	0	0	0	366.3	366.3
56	Monochamus urussovi	Krasnoyarskoye	0	89.5	84	84	0	0	0	0
57	Monochamus urussovi	Maganskoye	0	83	83	82.5	82.5	82.5	82.5	82.5
58	Scolytus ratzeburgi	Manzenskoye	4	0	0	0	0	0	0	0
59	Ips subelongatus	Manzenskoye	21	0	0	0	0	0	0	0
60	Dendroctonus micans	Manzenskoye	5	0	0	0	0	0	0	0
61	Monochamus urussovi	Manzenskoye	0	67.1	48.5	22	22	22	22	22
62	Dicerca aenea	Manskoye	123	123	103	54	54	54	8	8
63	Ips sexdentatus	Manskoye	978	1084.4	1025.9	1291	1305.9	1231.9	1181.9	1280.9
64	Melanophila guttulata	Manskoye	0	0	0	7	0	0	0	0
65	Polygraphus proximus	Manskoye	0	0	0	0	0	0	0	5.1
66	Monochamus urussovi	Manskoye	0	574.2	571.4	598.1	583.2	583.2	583.2	583.2
67	Monochamus sutor	Manskoye	0	0	0	14.9	0	0	0	0
68	Polygraphus proximus	Mininskoye	0	0	0	0	0	0.4	707.22	749.1
69	Monochamus urussovi	Mininskoye	0	8.1	8.1	8.1	0	0	0	0
70	Monochamus urussovi	Motyginskoye	0	42143.6	40644.6	40361.6	40361.6	40361.6	35780.6	15342
71	Ips typographus	Nazarovskoye	27	16.2	0	0	0	0	0	0
72	Polygraphus proximus	Nazarovskoye	0	0	0	0	0	0	1522.4	1470.4
73	Ips subelongatus	Nevonskoye	4	4.2	4.2	4.2	4.2	4.2	4.2	4.2
74	Tomicus minor	Nevonskoye	119	98.9	86.3	21.4	49.9	49.9	161.9	123.9
75	Tomicus piniperda	Nevonskoye	39	39.4	39.4	0	21.4	21.4	21.4	21.4
76	Scolytus ratzeburgi	Nevonskoye	3	3	3	3	3	3	3	3
77	Melanophila guttulata	Nevonskoye	0	0	0	0	0	0	245.5	245.5
78	Xylechinus pilosus	Nevonskoye	0	0	0	49.9	0	55	55	55
79	Monochamus urussovi	Nevonskoye	0	104.9	104.9	104.9	104.9	104.9	137.9	137.9
80	Ips sexdentatus	Pirovskoye	87	87	87	87	87	87	87	70
81	Ips typographus	Pirovskoye	1125	1207.6	1052.6	1052.6	1052.6	1052.6	869.5	731.2
82	Tomicus minor	Pirovskoye	43	72.6	72.6	48	59.6	59.6	59.6	59.6
83	Tomicus piniperda	Pirovskoye	31	48	48	0	48	48	48	34.4
84	Scolytus ratzeburgi	Pirovskoye	97	97	97	97	97	97	97	0
85	Polygraphus proximus	Pirovskoye	0	0	0	0	0	0	3	3
86	Xylechinus pilosus	Pirovskoye	0	0	0	59.6	0	0	0	0
87	Monochamus urussovi	Pirovskoye	0	5570.2	5532.7	5532.7	5532.7	5532.7	5343.2	3442
88	Xylechinus pilosus	Sayano-Shushenskoye	1	1	1	53.9	0	0	0	0
89	Dicerca aenea	Sayanskoye	16	16.3	0	0	0	0	0	0
90	Tomicus minor	Sayanskoye	107	82.4	53.9	0	53.9	53.9	53.9	53.9
91	Melanophila guttulata	Sayanskoye	0	0	16.3	16.3	16.3	16.3	16.3	16.3
92	Monochamus urussovi	Sayanskoye	0	1.2	0	0	0	0	0	0
93	Monochamus urussovi	Severo-Eniseyskoye	0	330.5	330.5	309.2	25.9	25.9	25.9	5.9
94	Monochamus urussovi	Sayano-Shushenskoye	0	956	956.1	956.1	0	0	956.1	956.1
95	Monochamus sutor	Tayozhinskoye	73	68.9	24.9	24.9	20	20	20	20
96	Polygraphus proximus	Tayozhinskoye	0	0	0	0	0	0	275	355
97	Monochamus urussovi	Tayozhinskoye	0	2252.7	2135.2	1953.9	1310.4	1289.7	1281.4	1281.4
98	Ips subelongatus	Teryanskoye	0	0	0	0	0	0	93.2	93.2
99	Tomicus piniperda	Teryanskoye	0	0	0	0	0	0	70	70
100	Monochamus urussovi	Teryanskoye	0	759	759	759	759	759	654	654
101	Ips subelongatus	Tungusso-Chunskoye	48	30.7	30.7	30.7	30.7	0	30.7	30.7
102	Ips sexdentatus	Tungusso-Chunskoye	74	0	0	0	0	0	0	0
103	Tomicus minor	Tungusso-Chunskoye	0	0	0	27.1	0	0	0	0
104	Tomicus piniperda	Tungusso-Chunskoye	0	28.6	27.1	0	27.1	27.1	27.1	27.1
105	Monochamus urussovi	Tungusso-Chunskoye	0	0.6	0.6	0.6	0.6	0.6	0.6	0.6
106	Monochamus sutor	Tyuhtetskoye	4	4	4	4	4	4	4	4
107	Polygraphus proximus	Tyuhtetskoye	0	0	0	0	0	38.3	306.3	278
108	Monochamus urussovi	Tyuhtetskoye	0	173	173	173	173	173	172.5	172.5
109	Ips subelongatus	Uzhurskoye	7	7	7	7	7	7	7	7
110	Monochamus urussovi	Uzhurskoye	0	35	35	35	35	35	35	35
111	Melanophila guttulata	Usinskoye	0	0	0	0	0	91	91	91
112	Ips sexdentatus	Usinskoye	0	0	0	0	0	209	209	209
113	Monochamus urussovi	Usinskoye	0	0	0	0	0	1499	1499	1499
114	Monochamus urussovi	Usolskoye	0	1666	1666	39	39	39	39	39
115	Tomicus minor	Uyarskoye	14	14	14	0	0	0	0	0
116	Monochamus urussovi	Uyarskoye	0	346.5	346.5	0	0	0	0	0
117	Tomicus minor	Khrebtovskoye	0	0	0	0	0	0	0	0
118	Tomicus piniperda	Khrebtovskoye	0	84	84	84	84	84	84	84
119	Monochamus urussovi	Khrebtovskoye	0	768	768	768	717	717	717	717
120	Tomicus minor	Chunskoye	291	281	281	0	0	0	0	0
1121	Monochamus sutor	Chunskoye	3	1.5	1.5	1.5	1.5	21.5	21.5	21.5
1122	Scolytus ratzeburgi	Chunskoye	61	0	0	0	0	4	4	4
1123	Dendroctonus micans	Chunskoye	0	0	0	0	0	0	31	31
1124	Monochamus urussovi	Chunskoye	0	1552	0	0	956.1	956.1	17	17

 

 

Methods

In any community consisting of a large number of species, it is unlikely that any environmental factor affects only one species in the entire community. The effect of an environmental factor and the simultaneous reaction of several species to it may indicate the presence of an interaction between species, about possible connectivity into a complex within a community, about the presence of conjugation of population dynamics. This correlation is revealed as a correlation between the quantitative characteristics of species populations. There are two main types of contingency: the temporary conjugation of several species in one habitat and spatial conjugation of population dynamics of one species in different habitats. The temporal correlation is shown in the fact that the dynamics of the number of different species of the complex can occur synchronously in the same habitat, such as the rise in the number of Bupalus piniaria and the complex of phyllophages related to this species in the Krasnoturansky Bor in the Krasnoyarsk territory (Пальникова и др., 2014). The spatial conjugacy of a particular species can be characterized, for example, by the number of forest areas where outbreaks of its mass reproduction are observed at a given time.

When studying the spatial conjugacy of a certain species k in N = 62 habitats (forestries) during M = 8 years, the matrix A(k) = || a_ijk || dimension (N x M) was used, in which cell (i, j) presents data on the area of damage to the stands by species k in the i-th forestry in the j-th year. Such matrices were constructed for each of the P = 15 registered xylophage species.

When studying the temporal conjugacy of P species in habitat m, the matrix B(m)=||b_ijm|| of dimension (P x M) was used, in which data on the indicator of damage to plantings in this habitat by species i in year j are presented in cell (i, j). Such matrices were constructed for each of N = 62 forestries.

15 matrices A(k) were used to assess the spatial conjugation of population dynamics of an individual insect species in different habitats (forest areas). The values of correlation coefficients between rows of A(k) matrices for each of the 15 xylophage species studied were used for spatial conjugation calculations. As a result of such calculations, correlation matrices of spatial conjugacy dimension (N x N) were obtained for all 15 species of xylophages, in which a separate cell (i, j) characterized the spatial conjugacy development of outbreaks of mass reproduction of a separate xylophages species during 2007-2014 in forest areas i and j. If the absolute value of the correlation coefficient in the cell was significant according to standard statistical criteria, this indicated spatial correlations (in the case of negative values of the correlation coefficient – anticonjugation) of the development of foci of individual species in the two forest areas i and j. A positive value of the correlation coefficient in the cell of the correlation matrix indicated that with the emergence of the focus of mass reproduction of individual species within the forest area a similar lesion appears in another forest. If the correlation coefficient is negative, the appearance of a focus in one forest area was associated with the absence of a focus of the studied species in another forest area.

62 correlation matrices B(m) were used to estimate the time conjugacy of mass reproduction of different xylophage species in the same forest area. The values of correlation coefficients between rows of B(m) matrices were used for calculations. If the correlation coefficient was positive, it indicated that the presence of one species of the xylophage complex was a factor that influenced the appearance of another species, i.e. the presence of a temporary conjugation in the population dynamics between different xylophage species in the same habitat (forestry). If the correlation coefficient was negative, it indicated that the presence of one species in the focus did not affect the appearance of another species.

The statistical package Statistica 6.0 was used to calculate correlation matrices. The statistical significance of each correlation coefficient in the correlation matrices was estimated at the level of p = 0.90. If a separate correlation coefficient in the correlation matrix turned out to be insignificant at the selected level p, then it was concluded that there was no spatial synchronism of damage to plantations by pests of the same species in different habitats or a temporary synchronization of damage to plantations by pests of several species in one habitat.

Results

Time synchronization characterizes a situation when in a single territory outbreaks of several species are observed. For xylophages, this effect may be associated with changes in the state of forage woody plants on the territory. Different forestries in the Krasnoyarsk territory differ in the number of registered centers of mass reproduction of xylophages. The "record holder" for the number of foci of different species of xylophages is the Gremuchinsky forestry, where during 2007-2014 there were foci of mass reproduction of 11 species of xylophages. Also, a large number of foci of different species of stem pests were observed in the territories of the Kondinsky, Pirovsky, Mansky and Nevonsky forestries. In 11 forestries the centers of mass reproduction of only one species was observed; in 16 forestries there were no outbreaks of mass reproduction of xylophages in 2007-2014.

The distribution of forestries by the number of centers of mass reproduction of various species of xylophages is shown in Fig. 1. In almost two-thirds (65.6 %) of the total number of forestries (61), the number of xylophage enters does not exceed 2.

 

Fig. 1. Distribution of forest areas in Krasnoyarsk region by the number of outbreaks of various xylophages species

 

Distribution of centers of mass reproduction of xylophages in the territory of The Krasnoyarsk region depends on the natural and climatic conditions in which the forests are located. In table. 2 the characteristics of the occurrence of stem insect foci depending on the forest-plant area in which the forestry is located are given (Государственный доклад..., 2018).

 

Table 2. Occurrence of outbreaks of various species of xylophages depending on the forest-plant zone in which the forestry is situated 

Forest-plant zone	Total number of forestries	Number of forestries with registered outbreaks of mass breeding	The share of forestries with centers of mass reproduction	The average number of recorded outbreaks of breeding on a forestry
Taiga zone	17	12	0.71	4.75
Forest-steppe zone	36	28	0.78	2.79
South Siberian mountain zone	9	5	0.55	2.00

 

The share of forest areas with centers of mass reproduction of stem pests for the taiga zone is 71 %; for the forest-steppe zone - 78 %, for the South Siberian mountain zone – 55 %. In all three forest zones, the average number of registered xylophage mass breeding centers is at least 2. For the taiga zone it is 4.75, for the forest-steppe zone – 2.79, for the South Siberian mountain zone – 2. Different types of xylophage insects differ greatly in the area of territories where their mass breeding centers appeared and operated (table. 3).

 

Table 3. Maximum annual area (ha) of xylophage foci in the territory of Krasnoyarsk 

Species rank	Xylophagous insect species	Maximum annual area of outbreaks, ha
1	Monochamus urussovi	153085.0
2	Polygraphus proximus	8437.6
3	Monochamus galloprovincialis	7050.3
4	Ips sexdentatus	3250.7
5	Tomicus piniperda	2031.5
6	Ips typographus	1223.8
7	Tomicus minor	928.0
8	Melanophila guttulata	809.1
9	Ips subelongatus	314.0
10	Scolytus ratzeburgi	218.0
11	Dicerca aenea	184.0
12	Monochamus sutor	87.0
13	Xylechinus pilosus	55.0
14	Saperda carcharias	35.0
15	Dendroctonus micans	31.0

 

From the data of the table. 3 it can be seen that the size of the centers of mass reproduction of different species of xylophages differed significantly. Thus, the maximum annual area of foci of mass reproduction of Monochamus urussovi (153085 ha) is almost 5000 (!) times more than the maximum annual area of Dendroctonus micans foci (31 ha).

As an example of calculating the time conjugation of the occurrence of foci of mass reproduction of various xylophage species in one forestry, in the table 4 it is shown the area of damaged forest plantations (ha) on territory of Gremuchinsky forestry (data are selected from table 1). In the course of forest pathological surveys of forest plantations during 2007-2014, 9 xylophage species were observed in the Gremuchinsky forestry. The mass reproduction of Xylechinus pilosus was noted only once, and the area of the plantations damaged by it was just over 15 hectares. Saperda carcharias propagated in mass during 2012-2014, damaging stands on a small area. Every year in the plantations of the Gremuchinsky forestry there are foci of Ips sexdentatus, Tomicus minor, and Monochamus urussovi (since 2008). Complex centers of mass reproduction of xylophages are formed as a result of the increase in the number of 5-6 species of insects at the same time. Since 2012, 7 xylophage species have been registered simultaneously in outbreak foci (see table. 4).

 

Table 4. Areas (ha) of outbreak foci of various species of insects-xylophages on the territory of the Gremuchinsky forestry 

Xylophagous insect species	The area of foci (ha) of stem insects by years
	2007	2008	2009	2010	2011	2012	2013	2014
Dicerca aenea	45	45	0	0	0	0	0	0
Ips subelongatus	41	41	41	5.4	5.4	188.1	78.4	30.2
Ips sexdentatus	423	213.6	213.6	213.6	213.6	213.6	213.6	213.6
Tomicus minor	298	297.8	297.8	23.1	15.2	15.2	15.2	80
Tomicus piniperda	39	25.1	25.1	0	23.1	259	121.3	48.6
Melanophila guttulata	0	0	45	45	45	45	45	96.3
Saperda carcharias	0	0	0	0	0	35	35	12.8
Xylechinus pilosus	0	0	0	15.2	0	0	0	0
Monochamus urussovi	0	3287.4	3279.6	3241.2	3241.2	3241.2	3203.2	3203.2

 

By the data from the table. 4, according to the above calculation method, the correlation matrix of the time conjugation of foci of different xylophage species in the territory of this forestry was calculated (table. 5).

  

Table 5. Correlation matrix of the temporary conjugation of xylophage outbreaks in the Gremyachinsky forestry 

№ of species	Xylophagous insect species *
	1	2	3	4	5	6	7	8	9
1	1.000	-0.134	0.655**	0.737*	-0.258	-0.814*	-0.403	-0.218	-0.642
2		1.000	-0.088	-0.220	0.976*	-0.005	0.804*	-0.331	0.085
3			1.000	0.483	-0.136	-0.533	-0.264	-0.143	-1.000*
4				1.000	-0.405	-0.590	-0.559	-0.308	-0.464
5					1.000	0.123	0.881*	-0.321	0.129
6						1.000	0.313	0.064	0.516
7							1.000	-0.264	0.249
8								1.000	0.142
9									1.000

Note. * – species: 1 – Dicerca aenea, 2 – Ips subelongatus, 3 – Ips sexdentatus, 4 – Tomicus minor, 5 – Dendroctonus micans, 6 – Melanophila guttulata, 7 – Saperda carcharias, 8 – Xylechinus pilosus, 9 – Monochamus urussovi. ** – correlations are significant at the level of p = 0.90.

 

As it is known, for species i and j, the correlation coefficient r (i, j) = r (j, i), so the correlation matrix is symmetric with respect to the main diagonal, and data below the main diagonal can be omitted. As shown in table 5, there may be a positive conjugacy of the occurrence of foci of two species in the same forestry (the correlation coefficient r > 0 and is significant at the level of p = 0.90) and a negative conjugation of foci of two species in the same forestry (r < 0 and is significant at the level of p = 0.90). In the first case, if there is a focus of one species in the forestry, for the most part a focus of a positively conjugate species is also found. Thus, the centers of mass reproduction of the Ips subelongatus (species 2) and the Tomicus piniperda (species 5) are positively associated. For these species, the correlation coefficient r (2, 5) = +0.976. The centers of mass reproduction of Ips subelongatus (species 2) and Saperda carcharias (species 7) are positively associated too. For these species, the correlation coefficient r (2, 7) = + 0.804.

In a case of negative conjugacy, if there is a focus of one species, the foci of another species do not occur. This is the case with the foci of Ips sexdentatus (species 3) and the Monochamus urussovi (species 9). For these species, the correlation coefficient r (3, 9) = - 1.0.

On the basis of calculations of time conjugation correlation matrices of foci of mass reproduction of the xylophage insect complex in various forestries of the Krasnoyarsk territory, a positive conjugation in the dynamics of a number of xylophage species was revealed (table 6).

M. galloprovincialis (see table 6) is the species that is associated with the largest number of foci of other species-xylophages of this complex. This species forms conjugate foci with 10 other species, of which the foci of Monochamus galloprovincialis and Scolytus ratzeburgi are most often interconnected. Monochamus galloprovincialis damages all coniferous trees, but most strongly – the scotch pine. When passing additional nutrition in the crowns of trees, beetles gnaw the bark of thin branches, which significantly weaken the trees during mass reproduction. In addition to coniferous trees, beetles can damage branches and hardwoods such as birch and aspen. Scolytus ratzeburgi is widespread and damages, as a rule, old and weakened birch trees. Since these species do not compete for food resources, the conjugacy of their foci, according to Moran (1953), may be related to the common requirements for climatic conditions.

 

Table 6. Positive temporary conjugation of foci of certain types of xylophages 

Xylophagous insect species	The number of conjugated species	The most common interconnected species
Monochamus galloprovincialis	10	Scolytus ratzeburgi
Tomicus piniperda	8	Tomicus minor
Ips sexdentatus	8	Monochamus galloprovincialis
Monochamus urussovi	8	Monochamus galloprovincialis
Scolytus ratzeburgi	7	Monochamus urussovi
Melanophila guttulata	6	Dicerca aenea
Polygraphus proximus	6	Monochamus urussovi
Dicerca aenea	5	Melanophila guttulata
Ips subelongatus	5	Monochamus galloprovincialis
Ips typographus	4
Tomicus minor	4	Monochamus galloprovincialis
Dendroctonus micans	3
Xylechinus pilosus	3	Tomicus piniperda
Saperda carcharias	2
Monochamus sutor	2

 

Quite a large conjugation with foci of other species is characteristic for Tomicus piniperda, Ips sexdentatus and Monochamus urussovi. The number of related stem insect species with these three species is 8. At the same time, the most frequently paired species are Tomicus minor and Monochamus galloprovincialis.

Tomicus minor as Tomicus piniperda are found in the area of pine everywhere. The beetles feed on weakened trees. Their settlement area – the peaks, large branches, and the central part of tree trunks of various ages. In addition, the Tomicus by "haircut" weakens healthy, not yet populated by it pine trees, thereby preparing the base for further setting.

Tomicus piniperda attack weakened pines, often form foci on burning areas, in the foci of the pine fungus, in conditions of development pressure. These species belong to the spring phenological complex of stem pests.

Monochamus urussovi develop in all coniferous species. Beetles additionally feed on needles and bast on the shoots and branches of living trees. Monochamus urussovi in the forests of Siberia and the far East, breeds in huge number in Siberian silkworm foci, in burning areas, and in areas of large logging operations. All Monochamus inhabit both standing and fallen trees (Лесная энтомология, 2010). These species can act as competitors, but still form conjugate (complex) foci. This is due to the fact that the Tomicus piniperda, Tomicus minor, and Monochamus are capable of additional feeding in the imaginal phase. Additional feeding is carried out by beetles on shoots and branches viable trees, weakening them and expanding their food base. In addition, the joint mastering of woody plants by different species of xylophages allows to overcome the resistance of the physiological tree systems (Исаев, Гирс, 1975).

The spatial conjugacy of outbreaks of mass reproduction of a particular species can be characterized by the number of forest areas where outbreaks of its mass reproduction are observed. So, the centers of mass reproduction of Monochamus urussovi met in 36 forestries, Monochamus galloprovincialis – in 20, Tomicus minor and Polygraphus proximus – in 13 forestries. Among the most common species in the territory of the region are the Tomicus piniperda and Ips typographus (in 10 forest districts). Saperda carcharias with a 35-hectare outbreak was recorded on the territory of one forestry (see table 1). The reasons for spatial conjugation can be the synchronization of population dynamics and the state of forage plants, the similarity of the reaction of populations to weather changes in different habitats.

The risk of outbreaks of mass reproduction of a particular xylophagus species in the territory in the region can be characterized using the following indicators: the share of forest areas where outbreaks of this species occur, indicators of the conjugacy of outbreaks of this species in different forestries, the area of outbreaks of mass reproduction of this species in relation to the total area of forest plantations. The higher these values, the more risk of outbreaks of this species of xylophage.

As an illustration, we present an assessment of the risk of an outbreak of mass reproduction of Monochamus urussovi in forest areas in the Krasnoyarsk territory during 2007-2014.

Having data on the area of outbreaks of Monochamus urussovi in the forestry space of the Krasnoyarsk territory and time (2008-2014) (table 7), one can calculate the correlation matrix of spatial conjugation of Monochamus urussovi outbreaks in various forestries in the Krasnoyarsk territory. In table 8 a fragment of this correlation matrix is given (it is difficult to give the entire correlation matrix due to its large size).

The analysis of table 8 allows to identify areas with synchronous centers of mass reproduction of Monochamus urussovi. For example, the dynamics of development of the outbreaks of Monochamus urussovi matches in Gremuchinsky, Eniseysky and Usolsky forestries (correlation coefficients more than 0.78), whereas temporal dynamics of the development of outbreak of this species anticorrelated in Achinsky and Kizirsky forestry. Thus, the share of forestries where outbreak of this species is observed is equal to 0.581. For the entire complex of xylophages considered, information on the area of outbreaks and the percentage of forestries where outbreaks occur is given in table 9.

The risks of developing outbreaks of mass reproduction of various xylophage species in the territories of different forestries can be represented graphically in Fig. 2, where on the abscissa axis in this graph is the share q of forestries in which outbreaks of this species are observed, and on the ordinate axis is the logarithm of the share S₀ of the area of foci of this species from the total territory of the whole forests region. A point on the plane characterizes a separate species. For example, there are points that characterize the Monochamus urussovi (point 1), Monochamus galloprovincialis (point 2), and Ips sexdentatus (point 3).

Points in the lower left corner of the plane {q, ln S₀} characterize species with a low level of impact on the forest (the percentage of forest areas where these xylophage species occur is small, and the areas of foci are small). Thereto group belong the majority of species of studied entomocomplexes: Dendroctonus micans, Saperda carcharias, Xylechinus pilosus, Monochamus sutor, Dicerca aenea, etc. Points in the upper right corner of the plane {q, ln S₀} characterize the xylophagous species with a strong impact on the forest (the centers of mass reproduction of these species occur in most forestries on the territory of Krasnoyarsk region and the area of centers are large). Species from this group include Monochamus urussovi, Monochamus galloprovincialis, Tomicus minor, Polygraphus proximus. In the upper-left corner of the plane {q, ln S₀} on Fig. 2 there should be points that characterize locally impacting species (occurring in a small number of forestries, but the areas of centers in these forestries are large). In the lower right corner of the plane {q, ln S₀} there should be points that characterize diffusely affecting species with centers in a large number of forestries, but with a small area. However, as can be seen in Fig. 2, locally and diffusely affecting xylophage species were not found in the territory of forestries of the Krasnoyarsk region during the research period.

Discussion

The problem of the occurrence of foci and the frequency of outbreaks of mass reproduction of dendrophilic insects for many decades occupies a leading place in ecological studies in the world. In the mid-twenties of the twentieth century, ecologists put forward theoretical ideas about the periodicity of mass reproduction, their interaction with the cycles of solar activity, climate, and natural enemies (entomophages). The main factor in the dynamics of the number of stem insects is the quantity and quality of food. Weather and other ecological factors have an indirect effect on population dynamics through the state of fodder plants.

In domestic and foreign ecological literature for a long time the question is raised about the relationship of insect population cycles with climatic factors Domestic and foreign ecological literature long ago has raised the question about the relationship of insect population cycles with climate factors. It is known (Берриман, 1990) that cycles of different populations of the same species separated by large distances can take place synchronously with each other. The mechanisms that ensure a synchronous increase in the number of insect populations over a wide area are not yet known in details. It is assumed that the cause of synchronization of outbreaks of mass reproduction of insects may be some external factor, the impact of which leads to the simultaneous development of local outbreaks. In particular, such synchronizing factors can be changes in the Sun activity (Чижевский, 1973), summer droughts over a wide area (Кондаков, 1974, 2002). Since the rhythm of the solar activity determines the dynamics of the impact of solar radiation simultaneously on the entire planet, and the number of outbreaks of number of insect species are not synchronized in time and space, it is assumed that the synchronizing factor is a combination of the rhythm of solar activity and local planetary rhythms (Moran, 1953). According to different authors, the reason for the conjugation of population dynamics of one species in different habitats may be the effect of P. Moran, associated with the uniformity of climatic conditions over a large area and the similarity of the reaction of populations to weather changes in different habitats (Максимов, 1989; Bjornstad, Bascompte, 2001; Пальникова и др., 2014). It is shown (Liebhold, Kamata, 2000; Liebhold et al., 2004), that the degree of conjugation of population dynamics of one species in different habitats monotonously decreases with increasing distance between these habitats. If the level of conjugacy of population dynamics does not decrease with increasing distance between habitats, and the distance between them significantly exceeds the radius of individual movement of animals of the studied species, then we should talk about its global spatial coherence associated with the reaction of populations to the influence of a powerful modifying factor.

 

Table 7. Areas of outbreak foci for Monochamus urussovi Fisch. on Krasnoyarsk Region territory for 2008–2014 

Forestry	The area of foci of Monochamus urussovi Fisch.(ha) by years
	2008	2009	2010	2011	2012	2013	2014
Achinskoye	13.7	13	13	13	13	13	13
Balakhtinskoye	41.5	35.3	33.2	0	0	0	0
Bogotolskoye	373.8	350.8	350.8	350.8	350.8	25	25
В.-Manskoye	659	659	609	609	609	609	609
Gremuchinskoye	3287.4	3279.6	3241.2	3241.2	3241.2	3203.2	3203.2
Mininskoye	8.1	8.1	8.1	0	0	0	0
Dzerzhinskoye	0	0	0	0	2	2	2
D.-Mostovskoye	95.3	95.3	205.3	110	110	110	110
Eniseyskoye	10081	10144	1711	2227	2227	831	831
Ermakovskoye	3280.4	3280.4	3280.4	3280.4	3280.4	3140	3140
Irbeyskoye	35508	35508	35508	35508	27250	26520	0
Kazachinskoye	7750	150	150	0	0	0	0
Karatuzskoye	4065	4065	3434	3434	3567	1732	1732
Kodinskoye	2391	2391	2391	2391	2391	2293	2578.9
Kozulskoye	3.9	3.9	3.9	3.9	3.9	0	0
Krasnoyarskoye	89.5	84	84	0	0	0	0
Kizirskoye	798	2961.1	2669.3	2650.9	2496.2	2496.2	2048.2
Maganskoye	83	83	82.5	82.5	82.5	82.5	82.5
Manzenskoye	67.1	48.5	22	22	22	22	22
Manskoye	574.2	571.4	598.1	583.2	583.2	583.2	583.2
Motyginskoye	42143.6	40644.6	40361.6	40361.6	40361.6	35780.6	15342
Nevonskoye	104.9	104.9	104.9	104.9	104.9	137.9	137.9
Pirovskoye	5570.2	5532.7	5532.7	5532.7	5532.7	5343.2	3442
S.-Shushenskoye	956	956.1	956.1	0	0	956.1	956.1
Sayanskoye	1.2	0	0	0	0	0	0
С.-Eniseyskoye	330.5	330.5	309.2	25.9	25.9	25.9	5.9
Tayozhinskoye	2252.7	2135.2	1953.9	1310.4	1289.7	1281.4	1281.4
Teryanskoye	759	759	759	759	759	654	654
Т.-Chunskoye	0.6	0.6	0.6	0.6	0.6	0.6	0.6
Tyuhtetskoye	173	173	173	173	173	172.5	172.5
Uzhurskoye	35	35	35	35	35	35	35
Usolskoye	1666	1666	39	39	39	39	39
Uyarskoye	346.5	346.5	0	0	0	0	0
Khrebtovskoye	768	768	768	717	717	717	717
Chunskoye	1552	0	0	956.1	956.1	17	17
Usinskoye	0	0	0	0	1499	1499	1499

 

Table 8. A fragment of the correlation matrix of spatial contiguity of the foci of the Monochamus urussovi Fisch in various forestries in the Krasnoyarsk Territory 

The number of forestry	The number of forestry *
	1	5	7	9	16	17	20	32
1	1.00	0.60**	-0.35	0.64*	0.51	-0.92*	-0.42	0.65*
5		1.00	-0.76*	0.91*	0.78*	-0.30	-0.51	0.85*
7			1.00	-0.60*	-0.75*	0.06	0.09	-0.55
9				1.00	0.75*	-0.37	-0.75*	0.99*
16					1.00	-0.25	-0.14	0.74*
17						1.00	0.31	-0.40
20							1.00	-0.76*
32								1.00

Note. * – forestries: 1 – Achinskoye, 5 – Gremuchinskoye, 7 – Dzerzhinskoye, 9 – Yeniseiskoye, 16 – Krasnoyarskoye, 17 – Kizirskoye, 20 – Manskoye, 32 – Usolskoye. ** – the correlation coefficient is significant at p = 0.90.

 

Table 9. Occurrence of outbreaks foci of certain xylophages species in forest areas of Krasnoyarsk Region during 2007–2014 

Species of insects- xylophages	Maximal annual area of foci, ha	Number of forestries with foci of this species	Percentage of forestries with foci of this species	The ratio of the areas of foci to the areas of forest plantations
Monochamus urussovi	153085	36	0.581	0.00156
Polygraphus proximus	8437.6	13	0.210	8.61*10-5
Monochamus galloprovincialis	7050.3	20	0.323	7.19488*10-5
Ips sexdentatus	3250.7	2	0.032	3.31736*10-5
Tomicus minor	2031.5	10	0.161	2.07316*10-5
Ips typographus	1223.8	10	0.161	1.2489*10-5
Tomicus minor	928	13	0.210	9.47031*10-6
Melanophila guttulata	809.1	6	0.097	8.25692*10-6
Ips subelongatus	314	9	0.145	3.20439*10-6
Scolytus ratzeburgi	218	7	0.113	2.22471*10-6
Dicerca aenea	184	4	0.065	1.87773*10-6
Monochamus sutor	87	6	0.097	8.87841*10-7
Xylechinus pilosus	55	5	0.081	5.61279*10-7
Saperda carcharias	35	1	0.016	3.57177*10-7
Dendroctonus micans	31	2	0.032	3.16357*10-7

 

Fig. 2. The risks of outbreaks of various xylophages species

 

The dynamics of the foci distribution, the synchronicity of their formation in space and the degree of synchronicity of the foci formation of different species in the same habitat are of practical importance. However, this requires materials on the inventory population outbreaks of dendrophilic species in forestries, performed by specialists. The use of spatial correlation matrices for a particular species allows, after the detection of foci of mass reproduction of this species of xylophage in a single forestry to assess the risks of outbreaks of this species in other forestries. The use of the correlation matrix of the temporal conjugation of the dynamics of several species in a separate forestry makes it possible to assess the risks of developing outbreaks of other xylophagous species in this forestry when a focus of mass reproduction of one xylophage species is detected.

Conclusions

1. The most dangerous species of xylophagous insects at risk of impact to forest stands in the Krasnoyarsk region are: Monochamus urussovi Fisch., Polygraphus proximus Blandf., Monochamus galloprovincialis Ol., Tomicus piniperda L.

2. To assess the risk of developing of conjugated foci of a number of species in a single forestry, one can use correlation matrices of time conjugation of xylophage populations. For example, for Gremuchinskoye forestry it is a high risk of concurrent development (temporary conjugation) of several species of xylophages: Ips subelongatus and Tomicus piniperda, Ips subelongatus and Saperda carcharias, Tomicus piniperda and Saperda carcharias, Dicerca aenea and Tomicus minor, Dicerca aenea and Ips sexdentatus.

3. To assess the risk of spatial conjugation of mass reproduction of a particular species of xylophage in different forestries, one can use correlation matrices of spatial conjugation of foci of this species. The highest degree of spatial conjugation of foci is typical for Monochamus urussovi, Monochamus galloprovincialis, Polygraphus proximus. This indicates the spatial distribution of these species, one should expect the simultaneous appearance of breeding centers of these species on the territory of different forestries.

References