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Периоды повторяемости пожаровменее 25 лет
25 - 50 лет
50 - 75 лет
75 - 100 лет
100 - 200 лет
200 - 400 лет
более 400 лет
Периоды повторяемости пожаровменее 25 лет
25 - 50 лет
50 - 75 лет
75 - 100 лет
100 - 200 лет
200 - 400 лет
более 400 лет
A R C T I C
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70N
60N
50N
180
30W
60W 60E
120W
90W
120E
30E
150W
150Е
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FI
C O C EA
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90E
less than 60 180–200
60–80 200–220
80–100 220 and more
100–120
120–140
140–160
160–180
Stand replacement return interval an estimated average time period (in years) during which the complete
replacement of old stands by the young ones could occur on every plot
(within the area of 100,000 ha) with the rate of tree cover change
as observed during the years 2000–2013.
T. Khakimulina 1, A. Yaroshenko 2 Moscow, Greenpeace Russia, 20161 [email protected] 2 [email protected]
Greenpeace Russia, 125040, Russia, Moscow, Leningradsky prospekt, 26, b. 1 Phone: +7 (495) 988 74 60, [email protected], www.greenpeace.ru
What is the stand replacement return interval?
The periodic replacement of old forest stands by the young ones – as a result of natural and semi-natural disturbances (such as fires, windthrows, insect outbreaks and forest diseases) as well as forest management (particularly clearcuts) – is characteristic to the majority of forests in northern countries. In these cases large-scale disturbances and clearcuts compete for the same resource — productive forest stands.
To find out whether forest management may lead to depletion of forests, it is necessary to take into account changes in the forest cover, resulting from both the influence of the forest industry and spontaneous (natural or semi-natural) stand replacement events. Even if logging alone does not exceed the annual allowable cut and the scale of spontaneous stand replacement events does not exceed historical averages, the cumulative impact of both of them may lead to quick changes in the forest cover and overall depletion of forest resources.
How quickly the old stands are replaced by the young ones within the analyzed area can be characterized by the stand replacement return interval (SRRI) — an estimated value calculated with “moving window” method using the following formula:
The SRRI is an analogue of the rotation period average for all forests within a clearcut system, but it is calculated by taking into account clearcuts as well as other stand-replacing events.
The SRRI shows the estimated average period of time during which each particular site (within the area under consideration or “moving window”) would undergo a complete replacement of old forest stands by the young ones, under the condition that the rate of tree cover change would be the same as during time T. Calculating the SRRI helps as the first approximation to detect areas where forest stands disappear more quickly than they can recover.
If the SRRI value is smaller than the rotation period most widely used in Northern forests (80-120 years), it means that the rate of annually cut or otherwise replaced forest stands is larger than what would be acceptable in the most intensive sustainable forest use. Small SRRI values clearly indicate that within the examined area the use of forests is not sustainable.
However, forest management could also be unsustainable even with medium and large SRRI values (80–160 years and longer) due to a shift in species composition, depletion of quality and productivity of forest stands as a result of high grade logging and other reasons. To correctly estimate whether forest management with such SRRI values does not cause the depletion of forests, it is necessary to provide an additional analysis taking into account tree species composition and stand qualities.
Data source and methodology
The calculation of the SRRI was based on the global forest change dataset for 13 years (2000–2013) by the University of Maryland specialists, based on Landsat satellite images with a spatial resolution of 30 meters — Global Forest Change (Hansen, Potapov, Moore, Hancher et al.).
Only forests that have a canopy density of 50% or more (according to the dataset) were included in the calculation. *The “moving window” method with a hundred thousand ha window size was used to calculate the SRRI values, which means that every point of the final map reflects the results of the SRRI calculation for all forests within a radius of 17.84 km around this point.
A detailed description of the methodology has been published on the following webpage by Greenpeace Russia: forestforum.ru/srri/en
NoteThe map is based on the Earth remote sensing data of global character and could contain local inaccuracies.
Stand Replacement Return Intervals in the Northern Forests in 2000–2013
T — period of time under analysis, in years; А — forest area within the moving window*, ha; В — area within the moving window where the stand replacement took place during the time T, ha.
SRRI = TxBA
