The Anthropic Impact On Relief And Vegetation. Case Study: Valea Ierii

Data collecting and processing

Data collection included in two stages. In July 2019, we organised a practical activity along the Iara River, from the exit of this river from the territory of Valea Ierii Commune to the area of Şimo, at the First Aid and Emergency Preparedness Base of the Romanian Red Cross, Cluj branch. On this route, we carried out several research activities in which we observed and analysed the components of the geographical space, various landscapes and some geographical processes. Data collection meant using the observation method, the case study, and photography. In the second stage, we selected the photos and cases proposed for analysis. In each case illustrated by the photographs, we made a list of questions that we asked the participants with the request to phrase concise answers, without additional documentation. The answers underwent content analysis and comparison. The photographs were analysed through visual methods. The guide published by Magdaș (2018) was also considered.

Participants

Three students (one at the Master’s and two Ph.D. level) and one professor with skills in the Sciences of Education participated in the field activity. Thus, the questions were answered by the three students who participated in the field activity and by two students at the Master’s level, who studied only the photographs.

The research material

It consists of field observations and photographs, and students’ answers to questions asked based on photographs.

The 1st case study

During previous research in the field, on a slope with southern exposure, located in the Iara Valley, upstream of Valea Ierii settlement, we identified a part of a landslide body (Figures 1 and 2 ). From the base of the slope, we did not notice the whole body of the slide, nor the head scrap. The rocks on both sides of the road indicated to us that the slip front covered it and temporarily blocked the access to the upper basin of the Iara River.

During the current practical field activity, we investigated more thoroughly, by brief observations and discussions with the participants, to establish the conditions that determined the sliding of the rock mass on the slope. It was confirmed the hypothesis that there is a forest road that crosses the body of the slip. The road has an inclination of more than 30°, it is arranged in diluvial deposits with a thickness of over 2 m, made up of chaotic blocks of crystalline systems with dimensions of maximum 30/30 cm, trapped in a clay mass, resulted by disintegration, alteration, and by their displacement from the upper part of the slope and redeposition to its middle and lower part (Figure 2 ). The road facilitated the rapid penetration of the water and caused the breaking of the balance of the unstable diluvial deposits, which were located on the slope with an inclination of more than 50°. They moved over the impermeable metamorphic rocks, resulting in the movement of this rock mass towards the base of the slope. The forest road was covered by the body of the landslide and was subsequently reconfigured and rebuilt above it.

After field observations, we asked the students to specify the following: the slope of the versant, the dimensions of the landslide body, the conditions that favoured the production of the landslide, the cause, the evolution, and measures to stop it. Those who analysed the slope in the photograph perceived that it has a lower inclination (30-45°) than in reality (50-60°), an aspect perceived correctly by those who studied it in the field. Estimating the dimensions of the landslide body based on the photographs was difficult, in particular, because objects with known dimensions where not visible. The three students that were in the field estimated the width of 3-15 m, the length of 10-25 m, and one student estimated the surface of the slide body as having 5000 m2. All students considered defrosting as the main cause of this gravitational process. They considered the large slope and the lack of vegetation, visible in the photograph, as conditions that favoured the landslide production and, based on previous knowledge, evoked other potential conditions (the presence of the clay that comes in contact with the water in the substrate; abundant precipitation in a short time and excess ground-water; the existence of a waterproof layer). Regarding future evolution, the students who were in the field noticed the risk of extending the body of the landslide both to the side and to the upper part of the slope, still forested now.

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As clues/evidence, a student referred to the bodies of rocks detached from the upper part of the slope, visible in Figure 2 . A student argues that the forest in the area bordering the landslide will not allow the process to be extended at the same speed as if the land had no forest vegetation. As measures to stop the landslide, they proposed: planting trees and shrubs, terracing, drainage works, and placement of nets. At the end of the case study, we concluded that the inadequate location and defective execution of a forest road on the slope produced an overload of a sector with minimum stability, the breakdown of the slope’s profile balance and induced a disorder effect on the natural elements.

The 2nd case study

In Figure 3 , we observe a pond ecosystem created through recent anthropic intervention. The road, at the base of the slope, formed an obstacle for the water and the downslope transported materials/sediments. The erosion and transport of the deluvial materials on the slope was favoured by the arrangement of the forest road, it facilitated the flow of water from precipitation and melting of snow along the slope. In the absence of a drainage channel underneath the road, materials of different sizes have accumulated and formed a quasi-horizontal drainage cone. The water has accumulated in a concavity resulting from the over-elevation of the road and because of the lack of necessary marginal canals for water to flow to the Iara River. The accumulation of water was also favoured by the impermeability of the petrographic substrate. The overheating of the soil and the stagnation of the water above it determined the drying of spruce (Picea abies), the predominant species in this area. As a result of the oscillations of the water level, under the influence of the precipitation variation, the initial vegetation was replaced by rush (Typha) and by other plants specific to this type (swamp) of humid environments.

The students were asked to remark the conditions that they thought favoured the accumulation of water and the development of the specific vegetation (i.e. rush) visible in Figure 3 . They mentioned several conditions that favoured the accumulation of water (the existence of a deep concavity, its overlap over an impermeable layer; the water supply from the streams), but without insisting on the favourable conditions necessary for the development of a pond ecosystem (for example, low water depth, small water level oscillations, etc.). Regarding the cause for this wet environment, the students mentioned the following: heavy rains, groundwater close to the surface, waterproof substrate, the water courses that fed this accumulation, and excess water. At the end of the case study, we concluded that the occurrence of a forest road along the slope represented an anthropic “aggression axis” on the environment, it directed the materials (water and sediments) and the road, without lateral drainage, formed a barrier for the runoff; as a result, the process of silting and ponding generated a pond ecosystem.

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The 3rd case study

On a slope with a southern exposure, with an inclination below 20-30°, we observed an association in which deciduous species with a height of 2-4 m predominate, indicating an age below 15 years (Figure 4 ). These trees were either planted or naturally grown, after clear-cutting trees in the previously existing forest. As a proof of the felling of the trees, the visible logs are kept among the young trees and several trunks of trees placed on the edges of the road located at the base of the slope, two being caught in the foreground of the photograph. On the left side of the picture, one can see taller trees, which have been preserved from the previous forest.

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Regarding the vegetation type, the students considered it to be a mixed forest, which includes species of conifers and deciduous trees. Although in the foreground there is a small spruce, the coniferous forest is visible in the photograph towards the upper part of the slope and on the watershed. Because we were interested whether the students noticed the existence of young arbores and that it developed on the site of the former forest, we asked them to mention what differences they observe in the landscape and what are their causes. The students noticed the differences in height and age between the taller and older trees on the left side of the image and those on the right, smaller and younger. The pyramidal shape of the young trees of the deciduous species and probably the smaller spruce, located in the foreground, induced three students to perceive them as conifers and to conclude that there was a vegetation reversal. The fact that the trees in the central part of the image have a lower height was explained by their later planting or by their natural development, subsequent to the development of taller trees. The vegetation inversion and the presence of conifers at the base of the slope was explained through thermal inversion. At the end of the case study, we came to the conclusion that the “clear-cut” felling of the deciduous / coniferous forest resulted in the reduction of the initial forest surface, the destruction of the natural habitat, the natural development of secondary vegetation, and changes in forest composition.

The 4th case study

Downstream of the Commune of Valea Ierii, after a sector with a wide meadow of more than 100 m, a narrow sector begins in which the minor riverbed of the Iara River has direct contact with the slopes. On this broad meadow (Figure 5 ), on which grassy vegetation develops, several dry trunks and branches are visible. In the field activity, we asked several questions: Where do these trees come from? What was the agent who transported the trees to this place? Regarding the place of origin, in the field, we formulated several hypotheses: the trees come from the forests located upstream; the trees come from the nearby meadow; the trees come from the forest of the background slope. A student who was in the field expressed his opinion that the trees were cut from the opposite bank and transported near the access road. The existence of a road that goes up the slope is an indication to support this claim. Two students assumed that the trees came from upstream and had been transported by water at high flows. A student also presented the opinion that those trees were probably broken in place, due to natural causes (old age, storm). The presence of branches is confusing because if the trees were transported from the slope, their branches would have been cut before transport. The chaotic arrangement of the trees in the meadow indicates rather their transport and deposition by water, not by humans. The fact that the valley is narrowing suddenly in this place probably prevented the transport of the trees downstream, even in the situation of high flows. At the end of this case study, we concluded that, regardless of the place of origin for the trees, the absence of their roots indicates their cutting by humans, and their deposition in the meadow induces a disorganization effect of the natural elements and a negative visual impact.

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In addition to the results of the four case studies, another finding was that such activities contribute to students’ motivation for learning and overall well-being (see also Cuc, 2019c; Trifan, 2015; Trifan & Chiș, 2017).