The effects of Douglas fir monoculture on stand characteristics in a zone of Montane beech forest

Abstract

The right choice of tree species to form forest cultures is of paramount importance to the preservation of the diversity, fertility and ecological stability of forest ecosystems. To that end, we examined the effect of a 40-year-long cultivation of Douglas fir (Pseudotsuga menziesii (Mirb) Franco) on the floristic composition, characteristics of the forest floor, physical and chemical properties of the soil and the intensity of organic matter decomposition in a beech forest in western Serbia (Mt. Maljen). It was found that the cultivation of Douglas fir caused a reduction in biodiversity, changes in the chemical properties of the soil, that were most pronounced in the surface layers (0-10 cm), and a slowing down in the metabolism of the beech stand. The absence of many plant species characteristic to natural beech forests was observed in the Douglas fir plantation, these were reflected in the detected changes in the chemical properties of the soil, such as lower substitutional acidity (p<0.05), depletion of the adsorption of basis in the cation complex (p<0.001) and lower amounts of C, N, P (p<0.001) and K (p<0.01) in relation to the beech stand (control). No differences were found in soil moisture and active acidity levels. The higher value of the C/N ratio of the Douglas fir litter (p<0.001) provided proof for its lower decomposition rate compared to beech litter (p<0.05). Over time, all these changes could lead to further acidification and degradation of the soil and a reduction in this ecosystem's productivity.

Douglas fir impact on the dynamics and composition of humus in the soil of indigenous beech forest in western Serbia

“…The study area lying within the forty-year-old silvicultural system of Douglas fir and the control area within the autochthonous beech forest are characterised by the same ecological conditions, i.e. western exposure, a 2-5 ° slope, and the same soil types, formed on the same geological substrate (diabase), (WRB, Cambisol, dystric 2006;Kostić et al, 2016;Pavlović et al, 2017).…”

“…Even though these processes are related to moisture, temperature, aeration and the physical and chemical properties of the soils, as well as soil macrofauna activity, leaching by water and humus stabilisation (organomineral complexes and aggregates), the primary factor in these processes is the amount and quality of litter from woody species. For this reason, tree species substitution affects the quality and quantity of annual organic matter stock, as well as the decomposition rate, and can thus have a considerable impact on the modification of the physical and chemical characteristics of soil and on the processes in the soil (Pavlović et al, 1998;Albers et al, 2004;Moukoumi et al, 2006;Kostić et al, 2012Kostić et al, , 2016. Hence, the amount of organic matter and its dynamics have become a focus of research (Augusto et al, 2002;Moukoumi et al, 2006;Bonifacio et al, 2008;Kostić et al, 2012Kostić et al, , 2016.…”

“…Either translocated autochthonous species like Norway spruce were used or allochthonous species like Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) (Kostić et al, 2012(Kostić et al, , 2016 and Pinus strobus L. (Pavlović et al, 1997;Pavlović, 1992). Research has shown the impact of anthropogenic activities in forest ecosystems on the quantitative and qualitative dynamics of humus (particularly humins, humic and fulvic acids) and the dynamics of organic matter (Wollum Schubert, 1975;Piene and VanClave, 1978;Vesterdal et al, 1995;Pavlović et al, 1997;Ussiri and Johnson, 2001;Kawahigashi and Sumida, 2006).…”

Impacts of Norway spruce (Picea abies L., H. Karst.) stands on soil in continental Croatia

“…The C/N ratio in the soil surface layer in spruce plantations was in the range from 13.9 to 15.4, as opposed to 11.1 to 19.7 in natural stands. With increasing depth, the C/N ratio is reduced (Kostić et al 2016). In the present study, the C/N ratio at depths of 10-20 cm in the spruce plantations ranged from 11.1 to 14.9, as opposed to 9.8 to 17.5 in natural stands.…”

“…Research has shown that certain species, tipically when planted in a monoculture, have varying impacts on soil (Klimo 2000). The specificity of such impacts is associated with the nature of the tree species, in terms of the quality and quantity of the organic matter participating in humus production, nutrient cycling, fertility maintainance and ecological stability of the forest ecosystem (Augusto et al 2002, Mareschal et al 2010, Kostić et al 2016), leading to a modification of local microclimate and pedoclimate. Furthermore, the specific influences of vegetation on soil are associated with the macroclimatic conditions which will determine the production of organic matter and the dynamics of its humification and mineralisation (Berg & Mc-Claugherty 2008).…”