Ecology /6. Ecological monitoring
Dr. Kovjazin V.F.
National Uinversity of mineral resources “Gorniy”,
Russia
PhD student Morozova N.A.
Saint-Petersburg state forest technical University,
Russia
The Influence of Multiple Ground Fires
on Sanitary and Forest Pathological Conditions of Larch Forests in Central
Yakutia
Annually hundreds of forest fires burn hundreds of thousands
of hectares of forest areas in the central region of Republic Sakha (Yakutia). Fires
occur because of hot and dry summers and 30% of forest fires in suburban
forests of Yakutsk are the fault of human. Inaccessibility of many territories and
lack of forest roads seriously impact the timely fire detection and
extinguishing.
Consequently, many larch forests, prevailing in Yakutia,
are regularly burned by multiple ground fires. That also prevents good larch reforestation
because small larch trees die in fire.
In 2012 we conducted
forest pathological researches of larch forests in Namskiy district forestry
Namskiy branch of state fiscal institution (SFI) “Yakutian Forestry”. The aim
of the researches was to determine the sanitary and forest pathological
conditions of larch stands after multiple ground fires.
The studied
territory is a part of the middle taiga with forested area of 72-93%. Predominant
species in the forests is Cajanderi larch (Larix cajanderi Mayr) that occupies
87.4% of the forest covered area. Woodlands in the study area were burned by
ground fires of low and medium intensity in 1972 and 2002.
We studied
forest management documents and materials of forest taxation, analyzed
cartographic databases of past forest management, conducted field researches
and use modern satellite images of the forest reserves of Republic Sakha (Yakutia).
During the
current forest pathological researches we calculated the average sanitary category
of plants and percentage of burned trees, marked degree of root spur, root
collar and phloem damage by fire in each stratum. Tree survey was conducted to
identify the centers of mass reproduction of pests and diseases. Work was
carried out in accordance with the governing document of Federal forestry agency
number 523 of 29.12.2007 [3]. Type of pest insects and diseases was detected by
the determinants and reference books [1, 2].
In the course
of forest pathological researches of the territories the following was established.
Ground fires damage the root spur and root collar and dry the phloem (tab. 1).
Table 1
The degree of trees damage by ground fire
|
Tree species |
The number of trees with burned root spur, % |
Condition of root
collar |
Phloem torrefaction |
|||
|
English name |
Latin name |
burn of the root collar around the circumference |
The number of trees with burned root collar, % |
around the circumference |
The number of trees with torrefacted phloem collar,
% |
|
|
Larch |
Larix cajanderi Mayr. |
29 |
1/4 |
33 |
1/4 |
2 |
|
Pine |
Pinus sylvestris |
24 |
1/4 |
18 |
1/4 |
2 |
|
Birch |
Betula sp. |
59 |
2/4 |
42 |
1/4 |
8 |
Larch trees have higher percent of fire damage than pine ones. Birch is
not forest forming species on the forestry territory and in fires it burned
much more serious than thick-barked conifers. Larch and pine trees have trunk burns
of varying severity; many trees are greatly weakened.
Table 2
The degree of
stands infection
|
Tree species |
The name of
the disease |
The number of
infected trees, % |
|
|
English |
Latin |
||
|
Larch, Pine |
Red rot |
Phellinus pini (Fr.)
Pil. |
31 |
|
Pine |
“Resin top” |
invader – fungi: Cronartium flaccidum, Peridermium pini |
8 |
|
Birch |
Birch rot |
Piptoporus betulinus |
52 |
Forest stands with butt burns are infected by “resin top” and rot (tab.
2) and damaged by pest insects.
Trunks are strongly damaged by buprestid and bark beetle
(tab. 3). 10 years passed since the last fire and currently the stands are
already left by the pest insects.
Table 3
Main pest
insects of the researched forest stands
|
Tree species |
The name of
the pest |
The number of
damaged trees, % |
The damage degree |
|
|
English |
Latin |
|||
|
Larch |
Buprestid |
Phaenops
guttulata Gebl. |
38 |
low |
|
Pine |
Bark bittle |
Ips sexdentatus |
46 |
medium |
|
Birch |
Birch scolytid |
Scolytus ratzeburgi
Jans. |
15 |
medium |
The huge number of pest insects in the first years after
the fire attract birds, including woodpeckers. Woodpeckers, feeding on the stem
insect larvae that are under bark or in wood, hollow out a large number of wood
caves. This leads to an even greater reduction of the mechanical properties of
wood.
Table 4
Stand volume
and forest area distribution by sanitary condition categories.
|
Sanitary condition category |
Stand volume distribution by the categories |
Forest area distribution by the categories |
||
|
m3 |
% |
ha |
% |
|
|
Healthy |
18810,2 |
20,7 |
122,6 |
20,3 |
|
Weakened |
25171,1 |
27,7 |
164,9 |
27,3 |
|
Very weak |
17628,9 |
19,4 |
119,0 |
19,7 |
|
Dying |
3816,6 |
4,2 |
27,8 |
4,6 |
|
Recent deadwood |
90,9 |
0,1 |
0,6 |
0,1 |
|
Previous years deadwood |
5906,6 |
6,5 |
40,5 |
6,7 |
|
Windfall |
4089,2 |
4,5 |
29,0 |
4,8 |
|
Windbreak |
15357,1 |
16,9 |
99,7 |
16,5 |
|
Total |
90870,5 |
100 |
604,0 |
100 |
Thermal damage of butt and the subsequent attack of
stem pests heavily weakened the forests and led to the trees infection by stem
rot, as well as windbreaks and windfalls. In general, there was found the
prevalence of weak, very weak and windfallen trees on the district forestry
territory (tab. 4). The low percentage of resent deadwood and quite a large
percentage of plants of I-III sanitary condition categories show a gradual regeneration
of the forest ecosystem after the fire ten years ago.
To improve sanitary
and forest pathological conditions of the forest areas we recommend conducting
of total sanitary cutting on the territory of 84 ha and selective sanitary cutting
on 356 ha.
References