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/lp/de-gruyter/erosion-processes-initialized-by-use-of-heavy-equipment-in-mountain-nAMZwhZP0H
- Publisher
- de Gruyter
- Copyright
- Copyright © 2016 by the
- ISSN
- 2083-4810
- eISSN
- 2083-4810
- DOI
- 10.1515/aep-2016-0010
- Publisher site
- See Article on Publisher Site
Abstract
Forest stand decomposition of the Silesian Beskids which is followed by the tree cutting has been observed since the beginning of the 21st century. Changes in forest management due to the introduction of heavy machines for forest work mainly for skidding have been observed in the Silesian Beskids for the last decade. The paper presents results of a three-year investigation of erosion gullies forming in mountain forest after the skidding performed with use of heavy equipment. In the Wilczy Potok catchment comprising an area of above 100 ha 40 gullies were identified. The measurement of the length and depth of gullies showed that the total volume of soil and rock material removed from the catchment area due to erosion accelerated by skidding exceeded 9 000 m3. The year erosion rate for deep gullies was found to be 10%. The presented results show that necessary protective actions and preventive measures should be taken to mitigate the soil degradation processes. Introduction Among many forest ecosystem services the protection function of mountain forests seems to be of great importance. Their role increases along with the intensity of biotic and abiotic adverse stresses occurring presumably owing to climatic changes, such as weather anomalies, increased pest attacks and improper management practices (Bytnerowicz et al. 1999). Most of the mountain forests located in the southern Poland have the status of soil protection forests. Moreover, most of Polish rivers have their sources in the mountain areas. Changes in the retention capacity of mountain forests begin to be a problem not only for foresters but also for the local community due to the lack of drinking water. This is the reason why mountain forests in the southern Poland are classified as water protection forests. The Silesian Beskids belong to the Polish part of the West Carpathians. Spruce contributes in 74.4% to the 40,500 ha area of forests in the Silesian Beskids. In the Silesian Beskids, due to several successive years of droughts followed by the bark beetle gradation, the spruce forest dieback was observed. It is assumed that within 15 years all spruce trees will be cut down in that area. This situation needs the stand reconstruction, which is assessed to comprise 5500 ha, in the period of 10 years. Forest stand decomposition is followed by the sanitary cuttings. In Poland the forwarding and along-the-ground skidding are the most popular methods of wood extraction. The horse skidding which was traditionally used in the mountain areas has not caused so drastic changes in water/soil environment (one horse could pull one or two logs). Heavy tractors, such as LKT, are currently used in the whole mountain region and they can pull several spruce logs at the same time. Such activities lead to intensive erosion gully formation. Soil erosion involving gullies is one of the major causes of land degradation worldwide and a global threat to forestry productivity (Gyssels et al. 2005). The gullies are permanent incisions in the landscape and, depending on location, are responsible for 10% to 94% of the total sediment yield caused by water erosion in the world (Poesen et al. 2003). The negative effects of soil erosion include water pollution, crop yield depression, organic matter, suspended and dissolved material loss from the ecosystem, and reduction in water storage capacity (Bakker et al. 2004, Boardman and Poesen 2006, Stavi et al. 2010). The clearing of vegetation (Zheng et al. 2005), cultivation (Gyssels and Poesen 2003, Valentin et al. 2005) or overgrazing (Moir et al. 2000) are mentioned as anthropogenic causes of gully formation. The protection of soil resources has therefore been recognized as an important objective of environmental policy (CEC, 2006): this requires correct erosion rate assessment (Cerdan et al. 2010). The aim of this paper is to assess the effect of skidding with use of heavy equipment on soil erosion processes in the mountain area. The investigation carried out in the catchment consisted of three parts: identification of the gullies, measurement of the section (depth of gullies), and calculation of the erosion rate. Methods Investigation Area Investigation was carried out in the catchment of the Wilczy Potok Valley in Brenna, the Silesian Beskids (49°4007 N, 18°5637 E) in 20102012. The catchment area of 138 ha at the elevation of 750 m a.s.l. is covered with spruce monoculture. Slope steepness amounts to 13°. The soil is developed of the Carpathian Flysch, Godulska series, is classified as Albic Cambisol and the soil textural groups are as follow: 040 cm sandy loam, and 40160 cm medium and heavy stony loam (RDLP Katowice 2014). Mean annual temperature and rainfall for the last decade were 8.8°C and 1084 mm, respectively. Identification of the gullies Inventory of the gullies was performed using a GPS receiver. After finding the gully a starting point was marked followed by consecutive points every 10 m (shallow gullies) and 25 m (deep gullies). The course of the gullies was recorded as a "path" in the GPS receiver which made it possible to put them on topographic maps. Establishing and measurements of erosion gullies sections Observation of the erosion processes and their rate should be carried out on permanent sections. Gully sections are marked out by two benchmarks (steel rods) plunged into the soil. Next, the tape measure is stretched between the rods. Each section (course of the tape) should be selected in the same way to facilitate their identification in the field. These "zero points" which can be big stones, studs or thick tree roots should be localized 50 cm from the gully edge (Fig. 1a). The next step is determination of the gullies depth. Measurement is made using a metallic measurement tape whose end is loaded with 50 g weight. This tape is moved along the tape stretched between benchmarks and lowered so that its loaded end could reach the gully bottom. First measurement is made in the "zero point" towards the main axis of the gully and the last one in the opposite "zero point". The depth is recorded as Yi whereas localization on the horizontal tape as Xi (Fig. 1b). Such measurement allows for calculating a cross-sectional area of the gully through adding up the area of trapezoids (Fig. 2). Joining the corresponding individual trapezoids with trapezoids of the next section one can obtain a solid (Fig. 3), boulder tape measure rootstock 2,17 right ,,zero point" 2,48 3,37 2 ,1 4 - main axis of gulley right benchmark growing spruce tree A.) left benchmark h = 0,10 m an - sector area =(an+an+1)/2*h right benchmark - an+1 - consecutive measurements of gulley depth left ,,zero point" right ,,zero point" B.) Fig. 1. Installation of benchmarks and measurements of gully cross sections 2,2 left benchmark left ,,zero point" 0 1,8 1,07 2,22 V= v1 ..v11 Vx X= 1 2 3 4 5 6 7 8 Px Px=1 Sx Px+2 1m X= 1 2 S= s1 ..s11 Volume of gulley 1 running meter = = volume of segment between PX and PX+1 sections divided by distance (in meters) between these sections Fig. 2. Measurement of the erosion gully fragment volume between consecutive sections z y h4 h1 h3 h2 Fig. 3. Elementary segment of erosion gully for the volume calculation the volume of which is calculated according to the following equation: V= f ( x, y )dxdy + OAB f 2 ( x, y )dxdy CBA (1) gully type found in the catchment area formed by the alongthe-ground skidding. Data from this gully were not included in the analysis and measurements were performed to compare environmental consequences of horse and tractor skidding. Calculation of the erosion rate In 2011, on two deep gullies (R14 and R16) and on one shallow gully (R19) the measurement sections were established to determine the erosion rate. So the total volume of the gully segment between the successive sections is a sum of solids volume formed in the way described above. Field measurements In 2006 on slopes of the Wilczy Potok Valley the high level of trees defoliation was observed. In the same year cutting of forest stand has begun. The logs cut were skidded using LKT80 and LKT81 tractors; this was organized along the line which had not been used as a skidding route before. In 2010 an inventory of erosion gullies was carried out. In 2011, on 5 gullies R14, R16, R19, R21 and R18 of "W" type which were formed as a result of the overhead skidding the measurement sections were established. Such sections were also established on R34 gully which was the only "V" Results and discussion Within the investigated catchment, 40 erosion gullies formed due to skidding were registered (Fig. 4). In total the length of all identified gullies amounted to 10,198 m (Tab. 1). The longest one was 1,327 meters long (R5 + R13) followed by R1 828 m long (Tab. 1). Individual ride of a LKT heavy tractor leaves a "trace" of 2 m width. However, the dragged logs cause the widening of the gully. Further gully widening results from erosion of its edges. In the catchment area the width of gullies ranged from 2.5 m to 5.10 m, giving mean value of 3.5 m (n=123). Assuming such Fig. 4. Gullies in the Wilczy Potok catchment in Brenna Table 1. Parameters of the gullies Gully R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 Length [m] 828.3 600.3 628.1 520.2 531.8 361.8 358.9 487.5 414.0 79.9 318.6 81.8 794.8 350.0 197.0 375.3 110.8 130.0 150.0 145.2 304.0 Estimated volume [m3] 755.6 547.7 573.0 474.5 485.1 330.1 327.4 444.7 377.6 72.9 290.6 74.7 725.1 319.3 179.7 342.3 101.1 118.6 136.8 132.4 277.3 270.0 62.0 46.0 605.0 192.0 Measured volume [m3] Gully R22 R23 R24 R25 R26 R27 R28 R29 R30 R31 R32 R33 R34 R35 R36 R37 R38 R39 R40 Total Length [m] 179.3 74.9 103.4 364.9 93.3 65.2 145.8 180.4 65.9 192.6 39.9 69.4 98.2 117.3 124.7 163.2 104.7 37.6 197.6 10197.7 Estimated volume [m3] 163.5 68.4 94.3 332.9 85.1 59.4 133.1 164.5 60.1 175.7 36.4 63.3 89.6 107.0 113.7 148.9 95.5 34.3 180.3 9303.3 33.0 Measured volume [m3] to erosion accelerated by skidding amounted to 9,303 m3 (Tab. 1). Taking into account that skidding activities have been performed for six years we can assume that the annual volume of the soil material removed from the catchment amounted to 1500 m3/ha. For comparison, under natural conditions in the French Southern Alps, where the brittleness of the Jurassic black marl terrains renders them prone to intense gully erosion, this value amounted up to 100 m3/ha (Mathys et al. 2003). The volume of deeper gullies increased with the rate of 10% per year and in shallow gullies this decrease was twice lower (Tab. 3). From the deepest gully above 50 m3 of soil was removed during one year. Figure 5 shows that due to erosion process in gully no 19, from which the material is accumulated in the shallower segments, deepening of the deeper segments takes place. It may result from the lack of intensive or torrential rainfall. average width of the gully, in the catchment area of 138 ha 3.6 ha of undergrowth was taken away due to skidding. The field observations reveal that only small front parts of gullies have the capacity to self-regenerate due to succession. In the more remote parts of the gully route the erosion processes take place resulting in soil flow down which excludes this area from forest production. The main problem related to the erosion gullies caused by exploitation of forests is the soil erosion. Ten kilometres of gullies which were found on the 138 ha of the catchment area testify to the intensity of skidding work in this area. According to (Poesen et al. 2003) the investigation carried out in the watershed of Bystra (the ywiec Beskids) showed that this 420 ha catchment contained more than 4 km of gullies. In this area most of the gullies were formed due to horse skidding. Among the tested gullies the lowest volume of running meter was found for the V type gully (R34) and the highest volume for gully R19 1,613 m3/m (Tab. 2). In the work mentioned earlier (Pierzgalski and Popek 2002) that value amounted to approximately 1.35 m3 per running meter. The measurements were taken on 13% of the inventoried gullies. Taking into account the differentiation of the gullies in length and depth it may be stated that the selected gullies are representative for the investigated catchment. The mean depth of one running meter of gully was found to be 0,891 m3. On this basis it can be assumed that the total volume of soil and rock material removed from the catchment area due Conclusions Among the most common types of damages caused to forest ecosystems during skidding are soil disturbance and soil compaction which may increase the potential for erosion, retard the growth of residual trees and interfere with regeneration, and damage to residual trees and other vegetation which may slow down forest recovery and reduce the volume and quality of timber available for the subsequent harvest (Dykstra and Heinrich 1996). Table 2. Characteristic of gullies with the established cross sections No of gully R14 R16 R19 R21 R18 R34 Length [m] 350 375 150 304 129 98 total 1308 Volume [m3] 192 605 46 270 52 33 total 1165 Volume of one running meter [m3] 0.549 1.613 0.307 0.888 0.403 0.368 mean 0.891 ,,V" gully ,,W" gully Type of gully Table 3. Erosion rate of deep and shallow gullies No of gully Year 2011 R_14 2012 soil loss 2011 R_16 2012 soil loss 2011 R_19 2012 soil loss 0.309 0.325 1.48 1.61 Volume of one running meter [m3] 0.539 0.550 Total volume [m3] 175.274 192.469 17. 20 553.82 605.04 51.23 46.392 48.765 2.37 5 9 10 % Fig. 5. Erosion rate of a shallow gully R19 The presented data show that use of heavy equipment for skidding in mountain forests intensifies the erosion processes. Field observation has shown that even a few rides of skidder can begin the erosion process on the mountain slope leading to the formation of the "W" shape gullies which in comparison to "V" shape gullies leads to the increase of the soil material carried away from the catchment. Taking into consideration further long-time activities connected with forest reconstruction combined with felling of big volume of trees in the Beskid Mountains it is evident that such activities should be duly controlled by the forest services. The best practices should include: planning of new skidding trails taking hydrological and soil properties of the region into consideration all skidding routes should possess the infrastructure preventing the soil from erosion skidding routes that are no longer used should be protected against further erosion.
Journal
Archives of Environmental Protection – de Gruyter
Published: Mar 1, 2016