**Acknowledgements**

*Forest Degradation Around the World*

leaved forest as the general public think.

preparing on climate change are urgently required.

**10. Conclusion**

In addition, aggravation of spring drought, which comes from reduction of snow fall due to temperature rise during winter season and temperature rise and evapora-

Climate change does not induce temperature rise only simply but accompanies diverse and complex environmental changes likewise drought that we experience now. Moreover, vegetation damage spreads into various native plants beyond several sensitive plants. Environmental change due to climate change may cause additive retrogressive succession into poor vegetation near to open woodland rather than simple change from the deciduous broad-leaved forest to the evergreen broad-

The damage of *Castanea crenata* and *Prunus sargentii* was severe, and damage of *Q.mongolica* and *Carpinus laxiflora*, which composes late successional vegetation, was also found. Of more concern is that most plants without any relation with species and life form over all layers composing vegetation stratification such as canopy tree, understory tree, shrub, and herb layers were injured or died. For example, *P. densiflora* and *Q. variabilis*, which composes vegetation of the representative dry land and *Juniperus rigida*, *Weigela florida*, *Rhododendron mucronulatum*, etc., which forms their undergrowth, were damaged or died. Indeed, serious phenomenon progressed around us. Continuous monitoring and synthetic consideration for

In Seoul, the capital of South Korea, most flat plains and hilly terrain were transformed from the natural land surface to the artificial impervious one with the increase of population due to both birth and influx from the rural area. Consequently, green space shows imbalanced spatial distribution as it is restricted to the urban fringe, where the land is mountainous and thus development is difficult topographically and deficient in urban center. This imbalanced distribution of green space led to severe urban heat island effect, and the effect was followed by temperature inversion. Subsequently, this change produced altered air circulation patterns specific to city, particularly city with basin-type topography like Seoul [77, 79]. Movement of air pollutants from urban area is likely dominated by this air circulation. In this process, relatively heavy particulates are felled in urban center, while light gaseous pollutants are transported to the forested area in urban boundary. Spatial distribution of physicochemical properties of soil reflects the trends. Forest of this area experiences retrogressive succession from Mongolian oak forest of the late successional stage to Korean mountain ash forest of the earlier successional stage as it is continuously exposed to air pollutants blowing from urban center, and soil is acidified due to the effect. As the results of such changes, urban Mongolian forest shows decline symptom that species composition is different and species diversity is lower than that in natural landscape. Further, the result increases vulnerability to environmental stresses related to climate change including drought. Plant damage due to drought begun from withering of leaves of plants introduced for landscaping in the urban park. Over time, branches died and death of the whole plant body followed. As drought continues, plant damage spreads toward the urban forest beyond the residential area in the urban center. Damage of exotic plants or plants introduced for landscaping was observed first of all. But damage of the native plants began to appear soon after. In particular, damage of *Sorbus alnifolia*, the product of retrogressive succession, was remarkable. As retrogressive succession has already progressed much and thus the number of individuals of *Sorbus alnifolia* increased greatly, it was surmised as the level so that this phenomenon can

tion increase due to climate change, incites vegetation damage [37, 38].

**86**

This paper was supported by LTER program of the Ministry of Environment of Korea.
