Hydrological Regime and Human Activity in Forest Watersheds of Siberia

1. T.A. Burenina, A.A. Onuchin, E.V. Fedotova Hydrological Regime and Human Activity in ForestWatersheds of Siberia V.N. Sukachev Institute of Forest Siberian Branch the Russian Academy of Sciences

2. Forest ecosystems are the regulator of river flow; they have very important environmental functions, as soil and water protective. Ecological forest functions are greatly effected by forest industry, firstly, timber cutting.

3. Our study was conducted in forest ecosystems and watershed found in western Sayan Mountains and North Angara region. On the base of long time forest and hydrology investigations on cuts and in secondary forest estimation of water balance was made taking into account forest structure change during regeneration succession.

4. These regions are now days a mosaic of forest regeneration sites including both post-human and post-fire regeneration patterns.

5. Intact stands of Siberian Pine (Pinus sibirica) are found only in inaccessible areas.

7. DYNAMICS OF FORESTS STRUTURE IN NORTH ANGARA REGION

8. Kebezh (A) and Taigish (B) river catchments: 1 – undisturbed dark-needled conifer stands of chern taiga AVB; 2 – secondary mixed conifer/deciduous forest of chern taiga AVB; 3 – logging and fire scars in chern taiga AVB; 4 – grass-bog sites in chern taiga AVB; 5 – undisturbed dark-needled conifer forest in mountain taiga AVB; 6 – secondary mixed conifer/deciduous stands in mountain taiga AVB; 7 - logging and fire scars in mountain taiga AVB; 8 - grass-bog sites in mountain taiga AVB; 9 – dark-needled conifer open woodlands; 10 – tall and small shrubs; 11 – alpine meadows; 12 – dwarf birch (Betula nana) sites; 13 – rock outcrops; 14 – water bodies; 15 – clouds and shadows; 16 – roads; 17 – settlements. The result of the 2010 Landsat image classification

9. Total moisture evaporation on logging sites and in post-logging forest stands A: 1- Siberian pine, 2 – logging sites; B: 1- fir, 2 – birch, 3 – aspen; VIII – class of age of Siberian pine (160 years)

10. Structural changes of the total moisture evaporation during post-logging forest regeneration in Sayan transpiration, mm evaporation from soil, mm Evaporation of precipitation intercepted by canopy, mm Evaporation from snow surface, mm

11. Dynamics of runoff in secondary phytocoenoses

12. Dynamics of water balance characteristics in North Angara region is differ then in West Sayan. This region characterized by a highly continental climate. During the first several years after logging, strong winds blowing on vast clear cuts promote snowstorms, increase snow moisture evaporation, and hence reduce snow amountand river runoff.

13. Dynamics of snow pack in North Angara basin blue – forest sites black – logging sites

14. Correlationof river runoff with annual precipitations and time after beginning of forest cutting (A) and after reforestation (B) Y– river runoff, mm; X –annual precipitations, mm; Т – time, year

15. Dependence of runoff on annual amount of precipitation and forest cover in different climatic conditions Y – river runoff, mm; X –annual precipitations, mm; L – forest cover, %

16. Investigations in boreal forests of Central Siberia showed that post-logging recovery of forest water protection and erosion prevention functions can occur different ways on slopes and in big river catchments

17. While erosion decreases several times during only three to five years after logging on slopes, as compared to its immediate post-logging rate, water silt load in big rivers can remain high for decades after forest logging in their catchments. Among other factors, this can be attributable to erosion of timber transportation roads and skidding trails, which become extremely eroded 10-15 years following forest logging.

18. The model describing soil erosion rates on individual (separate) slopes and in elementary catchments ln M= -9,3+0,95lnX-0,064NlnL+0,069lnXlnm/lnL+ 5,03K+1,49lnI+0,0162ln((X-W)/In)I - 0,00026ln((X-W)/In)i2 • R2 =0,86; G =1,04; F=221;

19. Dependence of sediment load on slope length and precipitation rate M is sediment load modulus, tkm-2; L – slope length, m; I – precipitation rate, mm·min.-1

20. Dependence of erosion on time since last human activity at watershed and immediate post-disturbance soilmineralization area M is sediment load modulus, tkm-2; N is time since last human disturbance (logging, fire), years; m is immediate post-disturbance soil mineralization area %.

21. Dependence of restoration soil-protective functions period (yeas) fromsteepness of slope (degrees) and immediate post-disturbance soilmineralization area, %

22. CONCLUSIONS • Study areas, West Sayan and North Angara region, are nowadays a mosaic of forest regeneration sites including both post-human and post-fire regeneration patterns. These forest cover changes influence hydrological regime, particularly the total moisture evaporation and runoff. Our study revealed that hydrological effects of forest logging are determined by the background climatic parameters and logging site recovery characteristics. The rate of regeneration in logging sites controls moisture amount spent on transpiration and intercepted precipitation evaporation. Water balance calculated for secondary forest stands showed that evaporation structure and total amount significantly depend on forest succession trajectory.

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