Environ Monit Assess (2014) 186:2563–2572 DOI 10.1007/s10661-013-3560-1
Transforming Pinus pinaster forest to recreation site: preliminary effects on LAI, some forest floor, and soil properties Melih Öztürk & İlyas Bolat
Received: 24 June 2013 / Accepted: 19 November 2013 / Published online: 4 December 2013 # Springer Science+Business Media Dordrecht 2013
Abstract This study investigates the effects of forest transformation into recreation site. A fragment of a Pinus pinaster plantation forest was transferred to a recreation site in the city of Bartın located close to the Black Sea coast of northwestern Turkey. During the transformation, some of the trees were selectively removed from the forest to generate more open spaces for the recreationists. As a result, Leaf Area Index (LAI) decreased by 0.20 (about 11 %). Additionally, roads and pathways were introduced into the site together with some recreational equipment sealing parts of the soil surface. Consequently, forest environment was altered with a semi-natural landscape within the recreation site. The purpose of this study is to assess the effects of forest transformation into recreation site particularly in terms of the LAI parameter, forest floor, and soil properties. Preliminary monitoring results indicate that forest floor biomass is reduced by 26 % in the recreation site compared to the control site. Soil temperature is increased by 15 % in the recreation site where selective removal of trees expanded the gaps allowing more light transmission. On the other hand, the soil bulk density which is an indicator of soil compaction is unexpectedly slightly M. Öztürk (*) Division of Landscape Techniques, Department of Landscape Architecture, Faculty of Forestry, Bartın University, Room no: 314, 74100 Bartın, Turkey e-mail: [email protected] İ. Bolat Division of Soil Science and Ecology, Department of Forest Engineering, Faculty of Forestry, Bartın University, Room no: 404, 74100 Bartın, Turkey
lower in the recreation site. Organic carbon (Corg) and total nitrogen (Ntotal) together with the other physical and chemical parameter values indicate that forest floor and soil have not been exposed to much disturbance. However, subsequent removal of trees that would threaten the vegetation, forest floor, and soil should not be allowed. The activities of the recreationists are to be concentrated on the paved spaces rather than soil surfaces. Furthermore, long-term monitoring and management is necessary for both the observation and conservation of the site. Keywords LAI . Forest floor . Soil properties . Pinus pinaster forest . Recreation site
Introduction Forest landscapes are unique ecosystems involving both the land and atmosphere along with the interactions within these two components. Major land components consist of parent rock, soil, flora, fauna, surface and groundwater, whereas the major atmospheric components comprise aboveground parts of the vegetation particularly leaves, avian creatures, and atmospheric gasses including the air humidity. Besides their principal role in wood production, the hydrological cycle, generation of wildlife habitat, soil conservation and development, forest landscapes offer recreation for humans, supplying canopy and scenery (Waring and Running 2007). In turn, humans have significant effects both positive and negative on forest ecosystems. Positive
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impacts include the generation of new forests by plantation, treatment facilities and selective removals by thinning, and etc. On the other hand, consciously or unconsciously, intervention of man has caused negative consequences on the forests such as extensive cutting for fuel, fire generation, disturbance of wildlife by hunting, and etc. Managing forests for recreation (Koch and Skovsgaard 1999) and esthetics (Zipperer 2008) has been a growing concern in the world where rapidly increasing population requires psychological relaxation. Consequently, parts of the forests close to the peripheries of urban and suburban settlements are frequently transformed into recreation forests. Recreational usage of forests bears the possibility of both positive and negative ecological impacts. Encouraging the tree growth by thinning (Pretzsch 2009) and improvement of landscape quality by removal of invasive vegetation are the positive examples, whereas negative effects include threatening the wildlife (Jestaedt 2008), plant disturbance, and soil compaction due to trampling. Threats to forest flora and soil due to recreational activities were the focus of numerous studies; however, relatively few studies that concentrate on forest wildlife affected by recreation are found in the literature (Marzano and Dandy 2012). Studies that examined the effect of recreation on the forest flora and soil properties mainly focus on the trampling effects of the recreationists. Hamberg et al. (2010) and Özcan et al. (2013) are two relatively recent examples which have solely investigated the plant and soil disturbances, respectively. Most other studies generally examined jointly the disturbances on both forest flora and soil properties (e.g., Kuss and Hall 1991; Littlemore and Barker 2001; Amrein et al. 2005 and Kissling et al. 2009). Such studies generally focus on the disturbance of aboveground vegetation and soil properties involving soil density, compaction analysis, and assessment of organic matter amount. Yet, none of these mentioned studies refer to the change in forest Leaf Area Index (LAI) and impacts of this change. The change in the forest LAI occurs particularly after the thinning and clear-cutting practices which are applied primarily for silvicultural purposes (Ganatsios et al. 2010). LAI is commonly used for determining the impact of change due to the silvicultural practices such as thinning on soil and vegetation hydrology (Bréda et al. 1995; Tian et al. 2012) on carbon dynamics (Campbell et al. 2009) and removal of trees for the
Environ Monit Assess (2014) 186:2563–2572
generation of a recreation site. However, the use of LAI for the disturbance of the soil properties during the generation of recreation sites is not common. Conversion of a forest or part of a forest to recreation site can lead to major changes in the forest floor and soil properties (Cole and Marion 1988). Forest LAI is altered by any removal of trees during the generation of a recreation site. Forest LAI change influences the forest floor and soil properties both directly and indirectly (Perry et al. 2008). Based on the amount of litterfall from the canopy, LAI determines the dry forest floor biomass just beneath that canopy. Gaps within the canopy define the amount of light intrusion through the canopy onto the soil surface below (Bonan 2008; Perry et al. 2008). Light reaching the soil surface stimulates the growth of understory vegetation altering the amount of wet forest floor, particularly herbs. The distribution of dry forest floor biomass within a recreation site may change due to scattering by the recreationists. Dry and wet forest floor biomass may also be trampled on by pedestrians as well as vehicles or be covered by the roads and pathways constructed on the soil surface. Similar disturbances and compaction due to trampling may also occur to soils in the recreation site (Littlemore and Barker 2001), and they may be sealed by the roads and pathways (Kozlowski 1999). In addition to the above physical impacts, forest floor and soil may be exposed to some disturbances that would alter their chemical properties such as their organic carbon (Corg) and total nitrogen (Ntotal) contents (Kissling et al. 2009). In this study, a recreation site where the forest LAI was decreased by selective removal of Pinus pinaster trees is compared with a control site where no treatment was applied. Nevertheless, the concept involves the preliminary results indicating the environmental effects of Pinus pinaster forest transformation to recreation site.
Materials and methods Site description The forest site is located in the province of Bartın at the northwest of Turkey. The site that covers about 22.7 ha is located at 32°20'E latitude and 41°39'N longitude (Fig. 1). The altitude ranges between 80 and 195 m with an average of 138 m. The average slope is 16 % with the
Environ Monit Assess (2014) 186:2563–2572
Fig. 1 Location of Pinus pinaster forest within Bartın watershed and Turkey
dominant aspect oriented southwest. Moderate deep (50–90 cm) brown forest soil (TMFAL 2005) has formed on calcareous parent material (TGDMRE 2007). The average annual precipitation is 1041 mm
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mainly in the form of rainfall where the annual mean temperature is 12.6 °C (TSMS 2007). The dominant wind direction is from north and north-west. The site was planted with Pinus pinaster trees. The tree ages range between 10 and 20 years with an average of about 15 years. Height of the trees varies between 8 and 11 m. Mean diameter at breast height of the trees is 28 cm, ranging from a minimum of 20 cm to a maximum of 36 cm (TGDF 2011). The understory vegetation is mainly the shrubs composed of prickly juniper (Juniperus oxycedrus), smoke tree (Cotinus coggyrea), and green olive (Phyllrea latifolia) (Yılmaz 2001). The site is about 6.5 km away from the city center (Öztürk and Bolat 2012) and neighboring to the peripheral settlements. A major part of the Pinus pinaster forest covering 18.7 ha (about 82 % of the total experimental forest) was transformed to a recreation site under the name of ‘Bartın Urban Forest (BUF)’. BUF was opened in 2010 for public recreational usages and activities such as picnic, jogging, hiking, viewing, and etc. Recreational equipment comprising wooden pergolas, banks, taps, and waste baskets were introduced into the forest to serve visitors’ picnic activities. Pavements and pathways were constructed to convey visitors to the equipment and for jogging and hiking. The requisite space that was about 20 % of the area for all these usages, activities, and related equipment was obtained by removal of some trees. BUF has been used by visitors for the past 2 years. The visitors come particularly on the weekends of the summer months of June, July, and August when the mean temperatures are 19.7, 22.3, and 21.7 °C, respectively (TSMS 2007). Since making fire is not permitted, weekend recreational activities are mainly in the form of fire-free picnic. The number of the visitors is lower during the weekdays when the recreational activities are jogging and hiking rather than picnicking. On the other hand, only 4 ha (almost 18 %) of the Pinus pinaster forest site is occupied by the control site where the visitor entrance is restricted through wire barriers. Thinning has not been applied to this control site and consequently, no recreational equipment, pavement, and pathway were allowed. This forest site was selected for analyzing the impact of the recreational activities on the forest because it encompasses both disturbed and undisturbed areas. Methods and preliminary results of the environmental analysis of this relatively new site are briefly discussed in the subsequent sections.
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Six points from each of the recreation and control sites were selected for sampling in March 2012. Air temperature measurement, soil, forest floor sampling and analysis together with the canopy photographing and analysis were conducted within the neighborhood field of these points. Measurement of the air temperature was done by a thermometer placed at a shade. Leaf area index (LAI) analysis The Leaf Area Index (LAI) is a dimensionless parameter indicating the ratio of one-sided surface area of the leaves over the unit ground surface area (Chen 1996). Although there are numerous indirect measurement methods of LAI (Jonckheere et al. 2004), hemispherical photographing and analysis technique (Hale and Edwards 2002) was performed for this study. An 8mm fisheye lense mounted on a digital SLR body was used during the photographing. Six photographs within the neighborhood field of the sampling points were taken at each of the recreation and control sites. These photographs were then analyzed using the Hemisfer software (Schleppi et al. 2007) version 1.5.3. The analysis method of Lang (1987) was chosen and corrections were based on the integrated method of Chen and Cihlar (1995) and Schleppi et al (2007). Forest floor sampling and analysis Sampling locations within the recreation site were selected from areas where recreational activities are concentrated. A square wooden frame (20×20 cm) was used for sampling the forest floor. The forest floor within the square area of the frame was transferred into labeled plastic bags. Twelve forest floor samples were carried to the laboratory for analysis. After air-drying, all the samples were weighed, ground, passed through 2-mm sieve, and prepared for the analysis. The forest floor physical analyses comprise the determination of the total mass and moisture content. Chemical analyses were performed to determine the pH, organic carbon, total nitrogen, and electrical conductivity. The moisture content was defined by heating definite mass of forest floor to 70 °C. The ratio of the mass loss over the remaining forest floor mass gives the moisture content. Soil pH in a 1:2.5 soil/water suspension was determined using a pH meter while electrical conductivity of the soil was measured with an electrical conductivity meter using a 1:5 extract (Rowell 1994). Organic carbon
Environ Monit Assess (2014) 186:2563–2572
(Corg) was analyzed using the potassium dichromate (K2Cr2O7) oxidation method. Total nitrogen (Ntotal) was estimated using Kjeldahl digestion method (Rowell 1994). Soil sampling and analysis Soil temperature was measured directly in the field by inserting a sensitive thermometer into the surface soil. Soil samples were taken with a metal cylinder whose diameter and height are 8.1 and 6.5 cm, respectively. They were then transferred into labeled plastic bags. In total, 12 soil samples were carried to the laboratory for the analysis. After all the samples were air-dried, plant residues and gravels were excluded. Remaining soil samples were then ground and passed through a 2-mm sieve and prepared for analysis. Both the physical and chemical soil properties were analyzed. The soil physical analyses include the texture, moisture content, bulk density, particle density, and porosity, whereas the chemical analyses include pH, organic carbon, total nitrogen, calcium carbonate, and electrical conductivity. The soil texture was determined using the Bouyoucos (1936) hydrometer method. Hygroscopic moisture content was defined by heating known mass of soil to 105 °C. The ratio of the mass loss to the remaining soil mass is the hygroscopic moisture content. Dividing the soil mass by the volume of the metal cylinder gives the moist soil bulk density (Blake 1965). Extracting the hygroscopic moisture content means that the soil dry bulk density. Particle density was measured using the Pycnometer method, while the soil porosity was determined from the soil bulk density and the particle density (Brady 1990). CaCO3 was measured by the Scheibler calcimeter method (Rowell 1994). For the analyses of pH, electrical conductivity, organic carbon, and total nitrogen, same procedures were applied as described in previous section for the chemical analysis of the forest floor. Statistical analysis All statistical analyses were performed using the SPSS 16.0 software (SPSS Inc., Chicago, IL, USA). Specifically, the t-test was used to assess the significance of differences of the physical and chemical characteristics of the forest floor and soil from the recreation and control sites. The Pearson correlations between
Environ Monit Assess (2014) 186:2563–2572
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selected data were also determined (Devore and Farnum 1999).
Results The physical and chemical properties of the forest floor, together with the air temperature and LAI for the six sampling points in each of the recreation and control sites (Table 1) and the soil physical and chemical properties (Table 2) constitute the results of this study. The average and standard deviation for each parameter and whether the differences in the averages between the recreational and control sites are significant are also reported (Tables 1 and 2). The LAI, soil temperature, forest floor biomass, soil bulk density, soil organic carbon (Corg), soil total nitrogen (Ntotal) for the recreation and control sites are graphically compared (Fig. 2). The correlations between LAI and soil temperature, soil organic carbon and soil temperature, soil total nitrogen and soil temperature, soil organic carbon and soil bulk density, soil total nitrogen and soil bulk density, and soil organic carbon and soil total nitrogen are presented (Fig. 3). Given the proximity of the recreational and control sites, the air temperature in the recreation (16.0 °C) and control (16.3 °C) sites were close to each other (Table 1). Due to the removal practices, LAI of recreation site is 0.20 lower than the control site (Table 1, Fig. 2a). Based on the lower LAI, forest floor biomass of the recreation site (1440 gr m−2) is about 26 % lower than the control site (1941 gr m−2) (Table 1, Fig. 2c). On the other hand, reducing the LAI by removal allowed more light transmission increasing the average soil temperature of the recreation site (11.4 °C) compared to the control site Table 1 Physical and chemical properties of forest floors in the recreation and control sites. Values in bold indicate a significant difference (p
Transforming Pinus pinaster forest to recreation site: preliminary effects on LAI, some forest floor, and soil properties Melih Öztürk & İlyas Bolat
Received: 24 June 2013 / Accepted: 19 November 2013 / Published online: 4 December 2013 # Springer Science+Business Media Dordrecht 2013
Abstract This study investigates the effects of forest transformation into recreation site. A fragment of a Pinus pinaster plantation forest was transferred to a recreation site in the city of Bartın located close to the Black Sea coast of northwestern Turkey. During the transformation, some of the trees were selectively removed from the forest to generate more open spaces for the recreationists. As a result, Leaf Area Index (LAI) decreased by 0.20 (about 11 %). Additionally, roads and pathways were introduced into the site together with some recreational equipment sealing parts of the soil surface. Consequently, forest environment was altered with a semi-natural landscape within the recreation site. The purpose of this study is to assess the effects of forest transformation into recreation site particularly in terms of the LAI parameter, forest floor, and soil properties. Preliminary monitoring results indicate that forest floor biomass is reduced by 26 % in the recreation site compared to the control site. Soil temperature is increased by 15 % in the recreation site where selective removal of trees expanded the gaps allowing more light transmission. On the other hand, the soil bulk density which is an indicator of soil compaction is unexpectedly slightly M. Öztürk (*) Division of Landscape Techniques, Department of Landscape Architecture, Faculty of Forestry, Bartın University, Room no: 314, 74100 Bartın, Turkey e-mail: [email protected] İ. Bolat Division of Soil Science and Ecology, Department of Forest Engineering, Faculty of Forestry, Bartın University, Room no: 404, 74100 Bartın, Turkey
lower in the recreation site. Organic carbon (Corg) and total nitrogen (Ntotal) together with the other physical and chemical parameter values indicate that forest floor and soil have not been exposed to much disturbance. However, subsequent removal of trees that would threaten the vegetation, forest floor, and soil should not be allowed. The activities of the recreationists are to be concentrated on the paved spaces rather than soil surfaces. Furthermore, long-term monitoring and management is necessary for both the observation and conservation of the site. Keywords LAI . Forest floor . Soil properties . Pinus pinaster forest . Recreation site
Introduction Forest landscapes are unique ecosystems involving both the land and atmosphere along with the interactions within these two components. Major land components consist of parent rock, soil, flora, fauna, surface and groundwater, whereas the major atmospheric components comprise aboveground parts of the vegetation particularly leaves, avian creatures, and atmospheric gasses including the air humidity. Besides their principal role in wood production, the hydrological cycle, generation of wildlife habitat, soil conservation and development, forest landscapes offer recreation for humans, supplying canopy and scenery (Waring and Running 2007). In turn, humans have significant effects both positive and negative on forest ecosystems. Positive
2564
impacts include the generation of new forests by plantation, treatment facilities and selective removals by thinning, and etc. On the other hand, consciously or unconsciously, intervention of man has caused negative consequences on the forests such as extensive cutting for fuel, fire generation, disturbance of wildlife by hunting, and etc. Managing forests for recreation (Koch and Skovsgaard 1999) and esthetics (Zipperer 2008) has been a growing concern in the world where rapidly increasing population requires psychological relaxation. Consequently, parts of the forests close to the peripheries of urban and suburban settlements are frequently transformed into recreation forests. Recreational usage of forests bears the possibility of both positive and negative ecological impacts. Encouraging the tree growth by thinning (Pretzsch 2009) and improvement of landscape quality by removal of invasive vegetation are the positive examples, whereas negative effects include threatening the wildlife (Jestaedt 2008), plant disturbance, and soil compaction due to trampling. Threats to forest flora and soil due to recreational activities were the focus of numerous studies; however, relatively few studies that concentrate on forest wildlife affected by recreation are found in the literature (Marzano and Dandy 2012). Studies that examined the effect of recreation on the forest flora and soil properties mainly focus on the trampling effects of the recreationists. Hamberg et al. (2010) and Özcan et al. (2013) are two relatively recent examples which have solely investigated the plant and soil disturbances, respectively. Most other studies generally examined jointly the disturbances on both forest flora and soil properties (e.g., Kuss and Hall 1991; Littlemore and Barker 2001; Amrein et al. 2005 and Kissling et al. 2009). Such studies generally focus on the disturbance of aboveground vegetation and soil properties involving soil density, compaction analysis, and assessment of organic matter amount. Yet, none of these mentioned studies refer to the change in forest Leaf Area Index (LAI) and impacts of this change. The change in the forest LAI occurs particularly after the thinning and clear-cutting practices which are applied primarily for silvicultural purposes (Ganatsios et al. 2010). LAI is commonly used for determining the impact of change due to the silvicultural practices such as thinning on soil and vegetation hydrology (Bréda et al. 1995; Tian et al. 2012) on carbon dynamics (Campbell et al. 2009) and removal of trees for the
Environ Monit Assess (2014) 186:2563–2572
generation of a recreation site. However, the use of LAI for the disturbance of the soil properties during the generation of recreation sites is not common. Conversion of a forest or part of a forest to recreation site can lead to major changes in the forest floor and soil properties (Cole and Marion 1988). Forest LAI is altered by any removal of trees during the generation of a recreation site. Forest LAI change influences the forest floor and soil properties both directly and indirectly (Perry et al. 2008). Based on the amount of litterfall from the canopy, LAI determines the dry forest floor biomass just beneath that canopy. Gaps within the canopy define the amount of light intrusion through the canopy onto the soil surface below (Bonan 2008; Perry et al. 2008). Light reaching the soil surface stimulates the growth of understory vegetation altering the amount of wet forest floor, particularly herbs. The distribution of dry forest floor biomass within a recreation site may change due to scattering by the recreationists. Dry and wet forest floor biomass may also be trampled on by pedestrians as well as vehicles or be covered by the roads and pathways constructed on the soil surface. Similar disturbances and compaction due to trampling may also occur to soils in the recreation site (Littlemore and Barker 2001), and they may be sealed by the roads and pathways (Kozlowski 1999). In addition to the above physical impacts, forest floor and soil may be exposed to some disturbances that would alter their chemical properties such as their organic carbon (Corg) and total nitrogen (Ntotal) contents (Kissling et al. 2009). In this study, a recreation site where the forest LAI was decreased by selective removal of Pinus pinaster trees is compared with a control site where no treatment was applied. Nevertheless, the concept involves the preliminary results indicating the environmental effects of Pinus pinaster forest transformation to recreation site.
Materials and methods Site description The forest site is located in the province of Bartın at the northwest of Turkey. The site that covers about 22.7 ha is located at 32°20'E latitude and 41°39'N longitude (Fig. 1). The altitude ranges between 80 and 195 m with an average of 138 m. The average slope is 16 % with the
Environ Monit Assess (2014) 186:2563–2572
Fig. 1 Location of Pinus pinaster forest within Bartın watershed and Turkey
dominant aspect oriented southwest. Moderate deep (50–90 cm) brown forest soil (TMFAL 2005) has formed on calcareous parent material (TGDMRE 2007). The average annual precipitation is 1041 mm
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mainly in the form of rainfall where the annual mean temperature is 12.6 °C (TSMS 2007). The dominant wind direction is from north and north-west. The site was planted with Pinus pinaster trees. The tree ages range between 10 and 20 years with an average of about 15 years. Height of the trees varies between 8 and 11 m. Mean diameter at breast height of the trees is 28 cm, ranging from a minimum of 20 cm to a maximum of 36 cm (TGDF 2011). The understory vegetation is mainly the shrubs composed of prickly juniper (Juniperus oxycedrus), smoke tree (Cotinus coggyrea), and green olive (Phyllrea latifolia) (Yılmaz 2001). The site is about 6.5 km away from the city center (Öztürk and Bolat 2012) and neighboring to the peripheral settlements. A major part of the Pinus pinaster forest covering 18.7 ha (about 82 % of the total experimental forest) was transformed to a recreation site under the name of ‘Bartın Urban Forest (BUF)’. BUF was opened in 2010 for public recreational usages and activities such as picnic, jogging, hiking, viewing, and etc. Recreational equipment comprising wooden pergolas, banks, taps, and waste baskets were introduced into the forest to serve visitors’ picnic activities. Pavements and pathways were constructed to convey visitors to the equipment and for jogging and hiking. The requisite space that was about 20 % of the area for all these usages, activities, and related equipment was obtained by removal of some trees. BUF has been used by visitors for the past 2 years. The visitors come particularly on the weekends of the summer months of June, July, and August when the mean temperatures are 19.7, 22.3, and 21.7 °C, respectively (TSMS 2007). Since making fire is not permitted, weekend recreational activities are mainly in the form of fire-free picnic. The number of the visitors is lower during the weekdays when the recreational activities are jogging and hiking rather than picnicking. On the other hand, only 4 ha (almost 18 %) of the Pinus pinaster forest site is occupied by the control site where the visitor entrance is restricted through wire barriers. Thinning has not been applied to this control site and consequently, no recreational equipment, pavement, and pathway were allowed. This forest site was selected for analyzing the impact of the recreational activities on the forest because it encompasses both disturbed and undisturbed areas. Methods and preliminary results of the environmental analysis of this relatively new site are briefly discussed in the subsequent sections.
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Six points from each of the recreation and control sites were selected for sampling in March 2012. Air temperature measurement, soil, forest floor sampling and analysis together with the canopy photographing and analysis were conducted within the neighborhood field of these points. Measurement of the air temperature was done by a thermometer placed at a shade. Leaf area index (LAI) analysis The Leaf Area Index (LAI) is a dimensionless parameter indicating the ratio of one-sided surface area of the leaves over the unit ground surface area (Chen 1996). Although there are numerous indirect measurement methods of LAI (Jonckheere et al. 2004), hemispherical photographing and analysis technique (Hale and Edwards 2002) was performed for this study. An 8mm fisheye lense mounted on a digital SLR body was used during the photographing. Six photographs within the neighborhood field of the sampling points were taken at each of the recreation and control sites. These photographs were then analyzed using the Hemisfer software (Schleppi et al. 2007) version 1.5.3. The analysis method of Lang (1987) was chosen and corrections were based on the integrated method of Chen and Cihlar (1995) and Schleppi et al (2007). Forest floor sampling and analysis Sampling locations within the recreation site were selected from areas where recreational activities are concentrated. A square wooden frame (20×20 cm) was used for sampling the forest floor. The forest floor within the square area of the frame was transferred into labeled plastic bags. Twelve forest floor samples were carried to the laboratory for analysis. After air-drying, all the samples were weighed, ground, passed through 2-mm sieve, and prepared for the analysis. The forest floor physical analyses comprise the determination of the total mass and moisture content. Chemical analyses were performed to determine the pH, organic carbon, total nitrogen, and electrical conductivity. The moisture content was defined by heating definite mass of forest floor to 70 °C. The ratio of the mass loss over the remaining forest floor mass gives the moisture content. Soil pH in a 1:2.5 soil/water suspension was determined using a pH meter while electrical conductivity of the soil was measured with an electrical conductivity meter using a 1:5 extract (Rowell 1994). Organic carbon
Environ Monit Assess (2014) 186:2563–2572
(Corg) was analyzed using the potassium dichromate (K2Cr2O7) oxidation method. Total nitrogen (Ntotal) was estimated using Kjeldahl digestion method (Rowell 1994). Soil sampling and analysis Soil temperature was measured directly in the field by inserting a sensitive thermometer into the surface soil. Soil samples were taken with a metal cylinder whose diameter and height are 8.1 and 6.5 cm, respectively. They were then transferred into labeled plastic bags. In total, 12 soil samples were carried to the laboratory for the analysis. After all the samples were air-dried, plant residues and gravels were excluded. Remaining soil samples were then ground and passed through a 2-mm sieve and prepared for analysis. Both the physical and chemical soil properties were analyzed. The soil physical analyses include the texture, moisture content, bulk density, particle density, and porosity, whereas the chemical analyses include pH, organic carbon, total nitrogen, calcium carbonate, and electrical conductivity. The soil texture was determined using the Bouyoucos (1936) hydrometer method. Hygroscopic moisture content was defined by heating known mass of soil to 105 °C. The ratio of the mass loss to the remaining soil mass is the hygroscopic moisture content. Dividing the soil mass by the volume of the metal cylinder gives the moist soil bulk density (Blake 1965). Extracting the hygroscopic moisture content means that the soil dry bulk density. Particle density was measured using the Pycnometer method, while the soil porosity was determined from the soil bulk density and the particle density (Brady 1990). CaCO3 was measured by the Scheibler calcimeter method (Rowell 1994). For the analyses of pH, electrical conductivity, organic carbon, and total nitrogen, same procedures were applied as described in previous section for the chemical analysis of the forest floor. Statistical analysis All statistical analyses were performed using the SPSS 16.0 software (SPSS Inc., Chicago, IL, USA). Specifically, the t-test was used to assess the significance of differences of the physical and chemical characteristics of the forest floor and soil from the recreation and control sites. The Pearson correlations between
Environ Monit Assess (2014) 186:2563–2572
2567
selected data were also determined (Devore and Farnum 1999).
Results The physical and chemical properties of the forest floor, together with the air temperature and LAI for the six sampling points in each of the recreation and control sites (Table 1) and the soil physical and chemical properties (Table 2) constitute the results of this study. The average and standard deviation for each parameter and whether the differences in the averages between the recreational and control sites are significant are also reported (Tables 1 and 2). The LAI, soil temperature, forest floor biomass, soil bulk density, soil organic carbon (Corg), soil total nitrogen (Ntotal) for the recreation and control sites are graphically compared (Fig. 2). The correlations between LAI and soil temperature, soil organic carbon and soil temperature, soil total nitrogen and soil temperature, soil organic carbon and soil bulk density, soil total nitrogen and soil bulk density, and soil organic carbon and soil total nitrogen are presented (Fig. 3). Given the proximity of the recreational and control sites, the air temperature in the recreation (16.0 °C) and control (16.3 °C) sites were close to each other (Table 1). Due to the removal practices, LAI of recreation site is 0.20 lower than the control site (Table 1, Fig. 2a). Based on the lower LAI, forest floor biomass of the recreation site (1440 gr m−2) is about 26 % lower than the control site (1941 gr m−2) (Table 1, Fig. 2c). On the other hand, reducing the LAI by removal allowed more light transmission increasing the average soil temperature of the recreation site (11.4 °C) compared to the control site Table 1 Physical and chemical properties of forest floors in the recreation and control sites. Values in bold indicate a significant difference (p
