The impact on soil CO2 emissions by tree plantations composition, structure and climatic factors

Abstract

The monoculture stands of tree species had a different impact on soil respiration, which increased in the sequence: Thuja< Quercus< Larix< Betula. Compared with deciduous tree stands, soil respiration rate was about 27% lower in coniferous tree stands. Significant factors, which correlated with soil respiration, were soil temperature and humidity, soil nutrient concentration and cover of herbs layer. The aim of the investigation was to evaluate the impact of planted native and alien tree species on the compositions and abundance of ground vegetation species as well as on soil respiration, and chemical and biological properties. The study was performed in the biome of temperate mixed forests in the monoculture stands of native (Acer platanoides L., Alnus glutinosa L., Betula pubescens Ehrh., Quercus robur L., Tilia cordata Mill., Carpinus betulus L., Picea abies (L.) H.Karst., Pinus sylvestris L.) and alien (Aesculus hippocastanum L., Lcirix eurolepis Henry., Larix sibirica Lebed., Thuja occidentalis L.) trees, which, in 1958-1965, were planted near Kaunas, Lithuania. The same climatic and soil conditions were present in the area; the soil type was Endocalcari-Epihypogleic Cambisols with an anthropogenic influence. The average annual temperature was 6.0-6.5 °C, while rainfall was 600-650 mm. The data was collected in 2014—2017. The species composition and projection cover of shrubs, herbs and mosses were recorded in 10 1 nr plots in each stand. Soil respiration was measured with portable C02 analyser ADC BioScientific LCpro+ System in 10 randomly selected points. Soil moisture and soil temperature were electrochemically measured with portable instrument 'Wet' at the depth of 5 cm in the same points. Composite soil samples from the 10 points were collected randomly from each stand in three replicates at the depth of 0-10 cm. The concentration of organic carbon (C), total nitrogen (N), available phosphorus (P2O5) and potassium (K>0) was determined. The soil microbiota was assessed as well. The results showed differences in shrubs, herbs and mosses among the stands of different tree species. The ground vegetation was reduced in Carpinus betulus, Aesculus hippocastanum and Thuja occidentalis L. stands due to a dense canopy cover.