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This study performed on randomly selected seven sample plots in leguminous black locust (Robinia pceudoacacia L.) plantations and five sample plots in umbrella pine (Pinus pinea L.) plantations on coal mine soil/spoils. Soil samples were taken from eight different soil depths (0-1, 1-3, 3-5, 5-10, 10-20, 20-30, 30-40, and 40-50 cm) into the soil profile. On soil samples, bulk density, fine soil fraction (Ø < 2 mm), sand, silt and clay rates, soil acidity (pH), organic carbon (C(org)), and total nitrogen (N(t)) contents were investigated. Also, some forest floor properties (unit mass, organic matter, and total nitrogen) were determined, and results were compared statistically between umbrella pine and black locust. As a result, 17 years after plantations, total forest floor accumulation determined as 6,107 kg ha(-1) under black locust compared to 13,700 kg ha(-1) under umbrella pine. The more rapid transformation of leguminous black locust forest floor creates organic carbon that migrates further into the mineral profile, and rapid accumulation of C and N in the soil profile was registered. Slower transformation processes of forest floor under umbrella pine result in lower soil N ratio and greater quantity of forest floor. Higher soil pH under leguminous black locust was determined significantly than umbrella pine. In conclusion, the composition of symbiotic nitrogen fixation of black locust appears to be a possible factor favoring carbon and nitrogen accumulation and, consequently, soil development. Clearly, both tree species have favorable impacts on initial soil formation. The umbrella pine generates the more forest floor layer; in contrast, black locust forest floor incorporates into the soil more rapidly and significantly increases soil nitrogen in upper soil layers.

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We sampled pure Douglas‐fir (DF) [Pseudotsuga menziesii (Mirb.) Franco] and mixed red alder (Alnus rubra Bong.)(RA) and DF (RA/DF) stands in 1980 and in 1999 to investigate the influence of RA on soil C and N pools. In RA/DF plots with 25% RA, the soil N pool to a 45‐cm depth increased significantly (P < 0.05) by 190 g N m−2, corresponding to 10 g N m−2 yr−1 accretion. The average between treatment soil N difference in 1999 was 166 g m−2, representing N accretion of 8.7 g m−2 yr−1 In pure DF plots, the soil N pool remained nearly constant. Resin N mineralization in RA/DF plots was about ten fold greater than on pure DF plots, but the enhanced resin N availability did not affect DF foliar N concentration. Temporal plot pairing was necessary within this landscape with high spatial variability to detect significant changes in soil N pools, and only large effects, such as N addition by RA, could be identified with statistical significance. Minimum detectable difference (MDD) estimates for mean total soil C differences in RA/DF plots showed that it would require about 30 more years of C accretion to detect differences at P < 0.05. Conversely, total soil N accretion in RA/DF plots was 28% greater than the MDD after 19 yr.

© iForest -Biogeosciences and Forestry IntroductionThe use of fossil fuels has determined an increase in the CO2 concentration of the atmosphere, causing the global greenhouse effect. According to the United Nations Framework Convention on Climate Change (UNFCCC) and its Kyoto Protocol (KP), forest ecosystems may contribute toward reducing human-induced greenhouse effect (UNFCCC 2001).It is well-known that any increase in the level of atmospheric carbon dioxide and other greenhouse gases also increases atmospheric temperature. Carbon dioxide is the most greenhouse gas with the greatest effect, and the steady increase in the amount of carbon dioxide in the atmosphere may be attributed to the use of fossil fuels and deforestation throughout the world (Nowak & Crane 2002).Forest ecosystems play a critical role in reducing the greenhouse effect and stabilizing climate by storing atmospheric carbon dioxide as biomass (Dixon et al. 1994, Binkley et al. 2004, Mohanraj et al. 2011.In order to understand the carbon sequestration process and carbon cycle, it is necessary to obtain data on tree biomass. On the other hand, because carbon is becoming a valued product on the global market, estimating the amount of carbon stored in growing trees and harvested wood is also important (McKinley et al. 2011). The determination of tree biomass is a challenging, time-consuming and costly process due to operations such as the cutting, uprooting, drying, and weighing of tree matter. Alternative techniques have been developed for the estimation of biomass from easily measured tree characteristics. Within the literature, the estimation of biomass values has generally used allometric equations. Allometry is the relationship between above-ground biomass and diameter at breast height and/or total height, below-ground biomass and diameter at breast height and/or total height, and above-ground biomass and below-ground biomass (Specht & West 2003, Gower et al. 1999. In former studies, scientists have frequently used allometric models for assessing above-ground and below-ground biomass (Overman et al. 1994, Sierra et al. 2007, Basuki et al. 2009, Khan & Faruque 2010, Razakamanarivo et al. 2011, Singh et al. 2011, Alvarez et al. 2012, Lima et al. 2012. Correspondingly, recent studies in Turkey have used allometric relationships to estimate the above-ground biomass for common tree species (Durkaya et al. 2009(Durkaya et al. , 2010a(Durkaya et al. , 2010b. These studies allow the estimation of above-ground biomass according to stem, branch, and leaf components; however, without additional evaluations, such techniques do not enable the estimation of the amount of bark and above-ground biomass, which are commercially valuable and thus removed from the forest during harvest, as well as those with no commercial value, that are left in the forest. Furthermore, there are a limited number of studies on the carbon contents of tree components that may be used for the estimation of the carbon storage capacity of forest ecosystems in Turkey.This study focus...