Natural and anthropogenic fragmentation of vegetation of Valday lake area

Abstract

Several hypotheses of inheritance “field” structure of the landscape in the modern forests of Valdai were confi rmed, as well as the opportunity to reconstruct the original dimension of its contours using geobotanical techniques. Evaluation of fragmentation of vegetation carried out using remote data revealed the dimension of the modern contours of different types of vegetation (forest, meadow and marsh). The average area of relatively homogeneous contour was 1.9 ha, coinciding with the average size of agricultural circuits identifi ed in the assessment of agro-landscape fragmentation. Index of fragmentation of the Valdai landscape within the boundaries of the contours of modern vegetation (pine, spruce, birch forests, meadows) is 0.18–0.24, showing not only the similarity of their genesis (in place of forest clearings and fi elds), but also centuries of existence in the cycle of the agricultural use. The analysis of field data and remote sensing data revealed patterns of actual spatial dynamics of vegetation in conditions of widespread reforestation and form an idea of the stability of its anthropogenic mosaic. It was established that the syntaxonomic analysis of vegetation (classifi cation of plant communities on the fl oristic principle) allows to reconstruct typologically (and, may be, actually) borders of single contour before agricultural land development. According to preliminary estimates, their size range from a few tens to hundreds of hectares, i.e., arrays of indigenous forests until settled farmers in Valdai occupied homogeneous elements of mesorelief and contours of similar Quaternary deposits completely. Comparison of fi eld data and remote sensing data helped to clarify the parameters of phytomass of plant communities in Valdai – from 12 (meadows) to 400 (immoral spruce) t/ha, as well as parameters of production – from 3 (bogs) to 13–15 (meadows, spruce immoral) t/ha per year. Comparison of phytomass of indigenous and secondary forests shows the decline in the latter case by 1.5–2.0 times. Reforestation of grasslandss, hayfi elds and pastures has signifi cantly changed the spatial structure of vegetation productivity in Valdai National Park, the stock of phytomass has grown. At the same time, recreational qualities of historically formed in Valdai ancient Russian forest-fi eld-meadow landscape that is attractive to tourists and valuable object of conservation of natural and cultural heritage are decreasing.