**3. Methods**

An ecological map to grasp landscape structure was obtained from Seoul City [59]. Landscape ecological analyses of the maps were determined with ArcGIS program (ver. 10.0).

Soil samples were collected from 150 grids, dividing 2 km × 2 km intervals, throughout the entire area of Seoul (all 605 km<sup>2</sup> ). Soil properties were measured for pH, Ca2+, Mg2+, and Al3+ contents, which can explain acidification and its effects. Soil pH was measured with a benchtop probe after mixing the soil with distilled water (1:5 ratio, weight per volume) and filtering the extract through Whatman No. 44 paper. Exchangeable Ca2+, Mg2+, and Al2+ concentrations were measured after extraction with 1 N ammonium acetate (pH = 7.0 for Ca2+ and Mg2+ and pH = 4.0 for Al3+) and using inductively coupled plasma (ICP) atomic emission spectrometry (Shimadzu ICPQ-1000) described in Allen [60].

Vegetation data were collected in the urban areas (Mts. Nam, Daemo, Bulam, Acha, Surak, Bukhan, and Cheonggye) and a natural area (Mt. Jeombong) (**Figure 1**). Vegetation survey was conducted in 66 plots, with 8, 10, 7, 8, 10, 4, 10, and 9 plots in each of the following sites: Mts. Nam (Mt. N hereafter), Daemo (Mt. D), Bulam (Mt. Bl), Acha (Mt. A), Surak (Mt. S), Bukhan (Mt. Bk), Cheonggye (Mt. Cg), and Jeombong (Mt. J), respectively. The size of each plot was 20 m × 20 m. All the plant species in each plot were identified using the Korea Plant Name Index [61]. For major tree species, stem diameters (at breast height for mature trees or at stem base for seedlings and saplings) were measured and sorted by diameter classes. The vegetation survey was conducted by applying the phytosociological procedure of Braun-Blanquet [62]. Dominance of each species in each plot was estimated by ordinal scale (1 for ≤5% up to 5 for ≥75%), and each ordinal scale was converted to the median value of percent cover range in each cover class. Relative coverage was regarded as the importance value of each species. Relative coverage was determined by dividing the cover fraction of each species by the summed cover of all species in each plot and then multiplying by 100. A matrix of importance values for all species in all plots was constructed and used as data for ordination using detrended correspondence analysis (DCA) [63]. To describe and compare species diversity and dominance among sites, rank abundance curves [55, 64, 65] were plotted. The Shannon-Wiener diversity index (H′) [65] was also calculated for each stand in each site.

**75**

*Forest Decline Under Progress in the Urban Forest of Seoul, Central Korea*

Meteorological data to confirm drought state were obtained from the Korea Meteorological Administration (https://data.kma.go.kr). The amount of evapotranspiration and evaporative demand was obtained by applying a method of

*Photos showing the grades for assessing drought-induced plant damage. I, none damaged; II (slight), less than 25% damaged; III (moderate), 25–50% damaged; IV (severe), 50–75% damaged; V (very severe), more than* 

Field survey for investigating drought-induced plant damage was carried out from May to early July before rainy season in 2017 and from July to August in 2018.

Field survey was conducted by recording degree of leaf surface injury of all plants appearing along the trampling path. Damage degree was classified into five groups based on the percentage of injury showed on leaf surface: very severe (V, more than 75% of total leaf area damaged), severe (IV 50–75% damaged), moderate (III, 25–50% damaged), slight (II, less than 25% damaged), and none (I, 0%) (**Figure 2**). We regarded the plant that all leaves were withered as dead individual in survey of 2017 and confirmed the result in the survey of 2018. The length of trampling path where field survey was conducted was about 4.0 km,

As the result of analysis on the landscape ecological map generated for Seoul, urban area occupied the widest as 60.8% of total area, secondary forests (12.7%), plantations (8.6%), river and reservoir (5.6%), landscape architectural plantation (4.5%), agricultural fields (2.5%), grasslands (2.4%), inaccessible area (2.3%), and bare ground (0.7%) followed (**Figure 3**). Forests composed of secondary forests and plantations and agricultural fields were usually concentrated to the city's fringe, and the urban center has little vegetation. Moreover, vegetation in the urban center was of low ecological quality, as most were fragmented into small patches and consisted of species introduced by landscape architects without ecological consideration or exotic plants [39, 40]. Therefore, green space showed severe imbalanced

Survey in 2018 focused on verifying the result assessed in 2017 survey.

and horizontal range was within 10 m in both sites.

*DOI: http://dx.doi.org/10.5772/intechopen.86248*

Blaney and Criddle [66].

**Figure 2.**

*75% damaged.*

**4. Landscape structure**

spatial distribution (**Figure 3**).

#### **Figure 2.**

*Forest Degradation Around the World*

**3. Methods**

program (ver. 10.0).

throughout the entire area of Seoul (all 605 km<sup>2</sup>

Siebold & Zucc.) community in the mountain peaks and around the residential area, the Mongolian oak (*Quercus mongolica* Fisch. ex Ledeb.) community in the upper slopes, the hornbeam (*Carpinus laxiflora* (Siebold & Zucc.) Blume) community in the lower slopes, and the sawleaf zelkova (*Zelkova serrata* (Thunb.) Makino) community in the mountain valleys [52]. East Asian alder (*Alnus japonica* (Thunb.) Steud.) stands remained in the plains and valleys of lowlands that escaped from urbanization [53–55]. Much of the natural forest in the Seoul metropolitan area disappeared due to extensive deforestation for fuel, building material, and other purposes during the twentieth century [56]. The human population of Seoul has increased from 2.4 million in 1960 to 9.8 million as of 2010 [57]. During this period, the percentage of green space decreased from 70% in 1960 to 29% in 2015, mostly to accommodate residential area [54, 56, 58]. Korean government designated most of the forested mountains in suburban areas of Seoul as greenbelt zones in order to prevent further loss of green space. Under the current greenbelt ordinance, no commercial, industrial, or urban development is permitted in those forests [58].

An ecological map to grasp landscape structure was obtained from Seoul City [59]. Landscape ecological analyses of the maps were determined with ArcGIS

Soil samples were collected from 150 grids, dividing 2 km × 2 km intervals,

Vegetation data were collected in the urban areas (Mts. Nam, Daemo, Bulam,

for pH, Ca2+, Mg2+, and Al3+ contents, which can explain acidification and its effects. Soil pH was measured with a benchtop probe after mixing the soil with distilled water (1:5 ratio, weight per volume) and filtering the extract through Whatman No. 44 paper. Exchangeable Ca2+, Mg2+, and Al2+ concentrations were measured after extraction with 1 N ammonium acetate (pH = 7.0 for Ca2+ and Mg2+ and pH = 4.0 for Al3+) and using inductively coupled plasma (ICP) atomic emission

Acha, Surak, Bukhan, and Cheonggye) and a natural area (Mt. Jeombong) (**Figure 1**). Vegetation survey was conducted in 66 plots, with 8, 10, 7, 8, 10, 4, 10, and 9 plots in each of the following sites: Mts. Nam (Mt. N hereafter), Daemo (Mt. D), Bulam (Mt. Bl), Acha (Mt. A), Surak (Mt. S), Bukhan (Mt. Bk), Cheonggye (Mt. Cg), and Jeombong (Mt. J), respectively. The size of each plot was 20 m × 20 m. All the plant species in each plot were identified using the Korea Plant Name Index [61]. For major tree species, stem diameters (at breast height for mature trees or at stem base for seedlings and saplings) were measured and sorted by diameter classes. The vegetation survey was conducted by applying the phytosociological procedure of Braun-Blanquet [62]. Dominance of each species in each plot was estimated by ordinal scale (1 for ≤5% up to 5 for ≥75%), and each ordinal scale was converted to the median value of percent cover range in each cover class. Relative coverage was regarded as the importance value of each species. Relative coverage was determined by dividing the cover fraction of each species by the summed cover of all species in each plot and then multiplying by 100. A matrix of importance values for all species in all plots was constructed and used as data for ordination using detrended correspondence analysis (DCA) [63]. To describe and compare species diversity and dominance among sites, rank abundance curves [55, 64, 65] were plotted. The Shannon-Wiener diversity index

spectrometry (Shimadzu ICPQ-1000) described in Allen [60].

(H′) [65] was also calculated for each stand in each site.

). Soil properties were measured

**74**

*Photos showing the grades for assessing drought-induced plant damage. I, none damaged; II (slight), less than 25% damaged; III (moderate), 25–50% damaged; IV (severe), 50–75% damaged; V (very severe), more than 75% damaged.*

Meteorological data to confirm drought state were obtained from the Korea Meteorological Administration (https://data.kma.go.kr). The amount of evapotranspiration and evaporative demand was obtained by applying a method of Blaney and Criddle [66].

Field survey for investigating drought-induced plant damage was carried out from May to early July before rainy season in 2017 and from July to August in 2018. Survey in 2018 focused on verifying the result assessed in 2017 survey.

Field survey was conducted by recording degree of leaf surface injury of all plants appearing along the trampling path. Damage degree was classified into five groups based on the percentage of injury showed on leaf surface: very severe (V, more than 75% of total leaf area damaged), severe (IV 50–75% damaged), moderate (III, 25–50% damaged), slight (II, less than 25% damaged), and none (I, 0%) (**Figure 2**). We regarded the plant that all leaves were withered as dead individual in survey of 2017 and confirmed the result in the survey of 2018. The length of trampling path where field survey was conducted was about 4.0 km, and horizontal range was within 10 m in both sites.
