Bark thickness models for oak forests being converted from coppice to high forests in Northwestern Turkey.

The research was carried out in the coppice-originated pure oak stands that are being converted to high forests in northwest Turkey. The main goal of the research was to determine the bark thickness (BT) based on tree variables, such as tree diameter at breast height (DBH), total tree height (H), crown diameter (CD), and age (AGE) of the stem sections taken from a total of 350 trees that were destructively sampled from different sites, different oak species (Quercus petraea, Quercus frainetto, Quercus cerris), and different development stages. Models were developed with stepwise multiple regression analysis to predict BT based on the variables. For all oak species, all models obtained by stepwise multiple regression analysis were found to be significant at p = 0.001 level. In Quercus petraea, only the DBH-dependent model explained the variation in BT at a rate of 73%, estimating with an absolute error rate of 21%. The fit statistics of the models (based on DBH and DBH-H explanatory variables) obtained for Quercus frainetto are very close to each other, and they explained the variation in BT at a rate of 69% and estimated with an error rate of 26%. Models (based on DBH and DBH-H explanatory variables) explain the variation in BT in Turkey oak at a rate of 91%, indicating species-specific results. The models based on only DBH can be used with high accuracy to estimate BT.

Nitrogen accumulation in forest floors with introduced Pinus pinea and Pinus pinaster in dune site.

Introduced stone pine (Pinus pinea L.) and maritime pine (Pinus pinaster Aiton) stands were sampled 60 years after plantation in Istanbul-Durusu (Terkos), Turkey. Sampling was conducted at four different developmental stages (mean diameter of trees at 1.3-m height (DBH) in stands: SDF = < 8 cm, MDF = 8-20 cm, LDF = 20-36 cm, and UDF > 36 cm), with 15 replicated sample plots for each species and developmental stage, for a total of 120 sample plots. The forest floor was sampled in 5 replications in each sample plot. The forest floor samples were divided into two layers: L + F (litter + fermentation) and H (humus), and the oven dry mass and nitrogen (N) content were determined. As a result, the masses of the total forest floor and of both layers were significantly different among the development stages with an increasing trend in maritime pine stands despite no significant difference found in the mass of the humus layer in stone pine stands. However, total forest floor accumulation significantly increased with the development stage (28-60 t/ha in stone pine and 17-64 t/ha in maritime pine). In both species, the N concentrations in the forest floor layers differed significantly among the development stages, and the N concentrations tended to increase as the development stage increased in the L + F layer, whereas a fluctuating trend was observed in the H layer. Although the N content of the humus layer of stone pine did not show a significant difference among the development stages, the N content in the total forest floor was determined to be 0.1-0.5 t/ha in maritime pine and 0.2-0.5 t/ha in stone pine. The relationship between the mean stand DBH and the N stock of the total forest floor was determined to have a higher correlation in maritime pine (R2 = 0.8) than stone pine (R2 = 0.4). In conclusion, the nitrogen concentrations and nitrogen contents of the forest floor were remarkably different in stands introduced with different tree species, indicating the accumulation of forest floor nitrogen.

Estimation of fresh sprout biomass based on tree variables of pollarding Turkey oak (Quercus cerris L.).

Pollarding of oak trees for livestock and animal feeding is a traditional application, and it has been used for centuries from generation to generation in southern and southeastern Turkey. Estimation of the fresh sprout biomass (FSB) potential of pollarded oak forests in high accuracy is important for sustainable forest management. In the present study, 40 trees were sampled from Turkey oak (Quercus cerris L.) stands that have been irregularly pollarded for animal husbandry in Adiyaman, southeastern Turkey. In order to estimate FSB, a multiple logarithmic linear model was developed with explanatory variables such as tree diameter at breast height (DBH), total tree height (H), mean sprout length (SL), and mean sprout age (SA), which are in a significant relationship with FSB. Stepwise multiple regression analysis was used to fit this multiple logarithmic linear model and to determine the best independent variable set. As a result of stepwise regression analysis, three models were obtained in which SL, DBH, and SA are independent variables. Model 1 estimates the FSB by taking only SL, Model 2 uses SL and DBH, and Model 3 uses SL, DBH, and SA as independent variables. All models were significant at p = 0.001 level. Model 1 explained the variation in FSB by 65%, Model 2 by 81%, and Model 3 by 86%. Inclusion of DBH in the model (Model 2) decreased the mean absolute error (MAE) of FSB by 26% and the inclusion of SA (Model 3) decreased MAE by 43%.

Biomass estimation of aboveground tree components for Turkey oak (Quercus cerris L.) in south-eastern Turkey.

Biomass equations were developed for different components of oak trees (Quercus cerris L.), which have been managed in coppices at different development stages-small-diameter forest (SDF) and medium-diameter forest (MDF). In this context, four biomass regression models-two based on diameter at breast height (DBH) alone and two based on DBH and total tree height (H)-were developed for each of the crown, stem, and total aboveground biomass components. Akaike's information criterion (AIC), root mean square error percentage (RMSE (%)), mean absolute error percentage (MAE (%)), adjusted coefficient of determination (Adj.R2), and bias values were used to evaluate and compare the suitability of a total of 12 regression models developed for biomass components. As a result, in the estimation of crown biomass, only DBH-based models provided higher estimation accuracy than DBH-H-based models. For the most suitable model, estimated values were Adj.R2 = 0.60, bias = - 0.009, RMSE = 66%, and MAE = 41%. In models developed to estimate stem biomass, the estimation accuracy of DBH-H-based models was higher. In the goodness-of-fit statistics calculated for the most suitable model, Adj.R2, bias, RMSE, and MAE were 0.89, 0.010, 38%, and 23%, respectively. The models developed to estimate the total aboveground biomass were all close in terms of estimation accuracy. The biomass components (crown and stem) in the total aboveground biomass were proportionally as follows: crown at 38% and stem at 62% in the SDF stage, and crown at 35% and stem at 65% in the MDF stage, indicating lower crown and higher stem partitioning as the development stage increased.

Biomass, carbon and nitrogen in single tree components of grey poplar (Populus × canescens) in an uncultivated habitat in Van, Turkey.

The biomass, carbon and nitrogen storage in the single tree components (foliage, branch, crown, bark, stem and total aboveground) of the grey poplar (Populus × canescens) in its distribution in Eastern Anatolia (Van, Turkey) were determined and modelled. The biomass, carbon and nitrogen storages were not estimated at a stand level but were based on single trees. Regression models based on the tree diameter at breast height (DBH) and total tree height (H) were developed to estimate the biomass, carbon (C) storage and nitrogen (N) storage of the different tree components of a total of 28 grey poplar trees. The two main regression models in the power function were developed based only on the DBH (Model 1) and the combination of the DBH and height (D2H) (Model 2). All regression models, except for those of the foliage components, developed to estimate the biomass and C and N storages of the tree components were found to be statistically significant (p < 0.001). The partitioning of the total aboveground biomass in the bark, foliage, branches and stems was 0.7, 9, 17 and 73%, respectively. The average C concentrations of the tree components ranged from 48 (foliage) to 50% (bark, branch and stem), while the N concentrations ranged from 0.35 (stem) to 1.32% (foliage). Higher biomass and lower nitrogen concentrations of foliage compared with cultivated poplars were likely related to the natural site conditions, low soil nitrogen and/or characteristics of single tree growth.

Soil organic carbon accumulation and several physicochemical soil properties under stone pine and maritime pine plantations in coastal dune, Durusu-Istanbul.

The study was conducted in dune restoration sites introduced with maritime pine (MP, Pinus pinaster Aiton) and stone pine (SP, Pinus pinea L.) at different development stages (diameters at breast height (DBH) in which small-diameter forests (SDF) = 0-8 cm, medium-diameter forests (MDF) = 8-20 cm, large-diameter forests (LDF) = 20-36 cm, and upper large-diameter forests (UDF) = > 36 cm). There were 15 replicated plots in each stage of both species and 25 dune sites; thus, a total of 145 sample plots were selected. Soil samples were taken from six different depth layers (0-5, 5-15, 15-30, 30-50, 50-70, and 70-100 cm). Forest floors were sampled with five replicates in each plot, and they were separated into leaf + fermentation and humus layers to determine unit mass and carbon concentration. Forest floor mass is significantly increased (17-34 t/ha in MP and 28-57 t/ha in SP) with the development stage. Low organic carbon (0.09-0.36% in MP and 0.13-0.84% in SP) was found in the top soil layer despite a significant accumulation of forest floor. The soil organic carbon density varies between 3 and 34 t C/ha. As the stand development stage increases, clay concentrations in every depth layer increased and soil pH and calcium carbonate values tend to decrease. Results indicated that both species have capability to grow on sandy material within poor nutrient and water capacities in a 50-year restoration process. However, the accumulation of forest floor increased and organic matter storage in the topsoil (0-5 cm) remained quite low due to the slow decomposition process.

Estimating the effect of abandoning coppice management on carbon sequestration by oak forests in Turkey with a modeling approach.

A significant area of the oak forests in Turkey has been historically managed by short-rotation coppicing for wood production. Coppice management was almost abandoned in Turkey in 2006 and so investigating its impact on forest carbon (C) sequestration has become an important issue. Therefore, we investigated the net effect of this change in management on C sequestration by oak forests in Turkey using field measurement data and a forest C model (Forest Biomass and Dead organic matter Carbon (FBDC) model). The FBDC model estimated the annual forest C dynamics and considered the effect of the substitution of wood for fossil fuels under two management scenarios over a 100-year period: (1) abandoning coppice (no management) and (2) continuing coppice (20-year-interval harvest). The field measurement data were used to parameterize the FBDC model to the study sites and to verify the simulated C stocks. Continuing coppice management constrained an increase in the C stocks (116.0-140.3 Mg C ha-1) and showed a mean annual C sequestration of 0.6 Mg C ha-1 yr-1 if wood was substituted for fossil fuels. In contrast, abandoning coppicing practices increased the level of forest C stocks (128.1-236.2 Mg C ha-1), enhancing the mean annual C sequestration to 1.1 Mg C ha-1 yr-1. Accordingly, the abandonment of coppice management increased the mean annual C sequestration by 0.5 Mg C ha-1 yr-1 in the long-term. However, sensitivity analysis showed a possibility of a larger difference in C sequestration between the two scenarios due to a decrease in the stand productivity by repeated coppices and a high likelihood of a lower substitution effect. The verification supported the scientific reliability of the simulation results. Our study can provide a scientific basis for enhancing C sequestration in coppice forests.

Humus characteristics and seasonal changes of soil arthropod communities in a natural sessile oak (Quercus petraea L.) stand and adjacent Austrian pine (Pinus nigra Arnold) plantation.

In order to assess the effects of conversion of natural stands into plantations, soil invertebrate micro- and macroarthropod communities were evaluated for their abundance and richness in a sessile oak (SO; Quercus petraea L.) stand and adjacent Austrian pine (AP; Pinus nigra Arnold) plantation. Sites were sampled four times a year in 3-month intervals from May 2009 to February 2010. Humus characteristics such as total mass; carbon, lignin, and cellulose contents; and C/N ratio were significantly different between SO and AP. Statistically significant differences were detected on soil pH, carbon and nitrogen contents, and electrical conductivity between the two sites. The number of microarthropods was higher in AP than in the SO site. The annual mean abundance values of microarthropods in a square meter were 67,763 in AP and 50,542 in SO, and the annual mean abundance values of macroarthropods were 921 m(-2) in AP and 427 m(-2) in SO. Among the soil microarthropods, Acari and Collembola were the dominant groups. Shannon's diversity index was more affected by evenness than species number despite the species diversity (H') of soil arthropods being generally higher in the SO stand. The abundance of microarthropods showed clear seasonal trends depending upon the humidity of the soil.

Temporal changes of soil respiration under different tree species.

Soil respiration rates were measured monthly (from April 2007 to March 2008) under four adjacent coniferous plantation sites [Oriental spruce (Picea orientalis L.), Austrian pine (Pinus nigra Arnold), Turkish fir (Abies bornmulleriana L.), and Scots pine (Pinus sylvestris L.)] and adjacent natural Sessile oak forest (Quercus petraea L.) in Belgrad Forest-Istanbul/Turkey. Also, soil moisture, soil temperature, and fine root biomass were determined to identify the underlying environmental variables among sites which are most likely causing differences in soil respiration. Mean annual soil moisture was determined to be between 6.3 % and 8.1 %, and mean annual temperature ranged from 13.0°C to 14.2°C under all species. Mean annual fine root biomass changed between 368.09 g/m(2) and 883.71 g/m(2) indicating significant differences among species. Except May 2007, monthly soil respiration rates show significantly difference among species. However, focusing on tree species, differences of mean annual respiration rates did not differ significantly. Mean annual soil respiration ranged from 0.56 to 1.09 g C/m(2)/day. The highest rates of soil respiration reached on autumn months and the lowest rates were determined on summer season. Soil temperature, soil moisture, and fine root biomass explain mean annual soil respiration rates at the highest under Austrian pine (R (2) = 0.562) and the lowest (R (2) = 0.223) under Turkish fir.

Impacts of repeated timber skidding on the chemical properties of topsoil, herbaceous cover and forest floor in an eastern beech (Fagus orientalis Lipsky) stand.

In this study, long-term timber skidding effects on herbaceous understory forest floor and soil were investigated on a skid road in a stand of the eastern beech (Fagus orientalis Lipsky). For this purpose, herbaceous understory forest floor and soil samples were collected from the skid road and from an undisturbed area used as a control plot. The mass (kg ha(-1)) of herbaceous and forest floor samples was determined, and soil characteristics were examined at two depths (0-5 cm and 5-10 cm). We quantified sand, silt and clay content, as well as bulk density compaction, pH, and organic carbon content in soil samples. The quantities of N, K, P, Na, Ca, Mg, Fe, Mn, Zn and Cu were determined in all herbaceous cover forest floor and soil samples. The quantities of Na, Fe, Zn, Cu and Mn in herbaceous understory samples from the skid road were considerably higher than those in the undisturbed area, while the quantity of Mg was considerably lower. These differences could have been caused by decreased herbaceous cover in addition to variations in the properties of the forest floor and soil after skidding. A lower amount of forest floor on the skid road was the result of skidding and harvesting activities. Mg and Zn contents in forest floor samples were found to be considerably lower for the skid road than for the undisturbed area. No significant differences were found in soil chemical properties (quantities of N, P, K, Na, Ca, Mg, Fe, Zn, Cu and Mn) at the 0-5 cm soil depth. Important differences exist between soil quantities of Mg at a 5-10 cm depth on the skid road and in undisturbed areas. Both 0-5 cm and 5-10 cm soil depths, the average penetrometer resistance values for the skid road was higher than for the undisturbed area. This result shows that the compaction caused by skidding is maintained to depth of 10 cm. Skid road soil showed higher bulk density values than undisturbed areas because of compaction.

Comparative study on soil properties in a picnic and undisturbed area of Belgrad Forest, Istanbul.

The aim of this paper was to investigate the recreational impacts on some soil properties (sand, silt, clay pH, electrical conductivity, organic carbon, bulk density, fine soil weight, compaction and saturation capacity), and litter (unit weight-mass, organic matter content (%) and organic matter mass) properties in a picnic area by comparing an undisturbed area in Istanbul Belgrad Forest-Turkey. According to the results obtained in this study the litter mass on the picnic area has been found considerably lower. There were some crucial changes in the characteristics of the soil which has been investigated in 0-5 cm depth. No important difference had been detected between the picnic area and the undisturbed area in terms of sand, silt and clay proportions. However, other investigated soil properties in 0-5 cm depth showed significant differences between undisturbed area and picnic area. Soil was significantly compacted by recreational activities in picnic area. Moreover organic carbon content (1.328%) on the picnic area has found quite lower Depending on the compaction of the soil and lessen quantity of soil organic matter the value of saturation capacity (24.13%) in the picnic area was considerably lower bulk density and fine soil weights significantly higher. Thus, the soil properties in the picnic area were negatively affected by recreational pressure.

Long-term effects of red deer (Cervus elaphus) grazing on soil in a breeding area.

This paper examines the effects of red deer grazing on some properties of soil (sand, silt, clay pH, electrical conductivity organic carbon, bulk density, fine soil weight, compaction and saturation capacity), and litter (unit weight-mass, organic matter content (%) and organic matter mass) properties on a red deer breeding area by comparing an undisturbed area in Istanbul Belgrad Forest-Turkey. According to the results obtained in this study the litter mass in the breeding area has been found considerably lower. There were some crucial changes in the characteristics of the soil which has been investigated in 0-5 cm depth. No important difference had been detected between the breeding area and the undisturbed area in terms of electrical conductivity. However, other investigated soil properties in 0-5 cm depth showed significant differences between the undisturbed area and the breeding area. Soil was significantly compacted by red deer grazing. The soil pH was 2.18 unit higher in undisturbed area. Moreover, organic carbon content (1.395%) in the breeding area was found quite lower. Depending on the compaction of the soil and lessen quantity of soil organic matter the value of saturation capacity (28.83%) on the breeding area is considerably lower, bulk density and fine soil weights were significantly higher. Mean silt and clay proportions (25.4 and 33.7%, respectively) are quite higher and the mean sand proportion (40.9%) was lower in the breeding area than in the undisturbed area. Results indicated that long-term red deer grazing in the breeding area adversely affected litter and soil properties.

Some soil properties on coal mine spoils reclaimed with black locust (Robinia pceudoacacia L.) and umbrella pine (Pinus pinea L.) in Agacli-Istanbul.

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.

Soil organic carbon and nitrogen accumulation on coal mine spoils reclaimed with maritime pine (Pinus pinaster Aiton) in Agacli-Istanbul.

Mining operations on open coal mines in Agacli-Istanbul have resulted in the destruction of vast amounts of land. To rehabilitate these degraded lands, plantations on this area began in 1988. Twelve tree species were planted, however, the most planted tree species was maritime pine (Pinus pinaster Aiton). This study performed on 14 sample plots randomly selected in maritime pine plantations on coal mine soil/spoils in 2005. Soil samples were taken from eight different soil layers (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; fine soil fraction (<2 mm), soil acidity (pH), organic carbon (C(org)) and total nitrogen (N(t)) contents were investigated, and results were compared statistically among soil layers. As a result, 17 years after plantations, total forest floor accumulation determined as 17,973.20 kg ha(-1). Total nitrogen and organic matter amounts of forest floor were 113.90 and 14,640.92 kg ha(-1) respectively. Among soil layers, the highest levels of organic carbon (1.77%) and total nitrogen (0.096%) and the lowest pH value (pH 5.38) were found in 0-1 cm soil layer, and the variation differs significantly among soil layers. Both organic carbon and total nitrogen content decreased, pH values increased from 0-1 to 5-10 cm layer. In conclusion, according to results obtained maritime pine plantations on coal mine spoils; slow accumulation and decomposition of forest floor undergo simultaneously. Depending on these changes organic carbon and total nitrogen contents increased in upper layer of soil/spoil.

Plant Species Recovery on a Compacted Skid Road.

This study was executed to determine the plant species of herbaceous cover in a skid road subjected to soil compaction due to timber skidding in a beech (Fagus orientalis Lipsky.) stand. Our previous studies have shown that ground based timber skidding destroys the soils extremely, and degradations on ecosystem because of the timber skidding limit recovery and growth of plant cover on skid roads. However, some plant species show healthy habitat, recovery and they can survive after the extreme degradation in study area. We evaluated composition of these plant species and their cover-abundance scales in 100 m x 3 m transect. 15 plant species were determined belongs to 12 plant families and Liliaceae was the highest representative plant family. Smilax aspera L., Epimedium pubigerum (DC.) Moren et Decaisne, Carex distachya Desf. var. distachya Desf., Pteridium aquilinum (L.) Kuhn., Trachystemon orientalis (L.) G. Don, Hedera helix L. have the highest coverabundance scale overall of determined species on compacted skid road.

Long term effects of thinning on soil and forest floor in a sessile oak (Quercus petrea (Matlusch) Lieb.) forest in Turkey.

The effects of thinning on mineral soil and forest floor for three different thinning intensities (control, moderate and heavy) were studied in a sessile oak forest 8 years after treatment. To examine responses to thinning, mass, organic matter and total nitrogen content in forest floor, bulk density and fine soil weight, total nitrogen, organic carbon concentrations and pH in upper mineral soil horizons were measured, and the results compared to control plot. The thinned plots have shown higher total nitrogen concentration and organic carbon in soil. Total mass, weight of layers of forest floor have shown significant patterns with thinning intensity. The present results indicate that various intensities of thinning for a sessile oak stand had major influence on soil and forest floor in eight years following treatment.