Recent human impact on vegetation in Takkobu, northern Japan, reconstructed from fossil pollen in lake sediments

Abstract

The vegetation of Takkobu, northern Japan, has been significantly altered by land-use development following Japanese settlement at the end of the 19th century. In order to assess the impact of human activity on vegetation dynamics in Takkobu, changes in the vegetation composition over the last 300 years were reconstructed from fossil pollen in the sediments of Lake Takkobu. The pollen assemblage represented broadleaved forests on the surrounding hills and alder forests found on the margin of the wetland bordering the lake. Prior to Japanese settlement, the hillside forests consisted predominantly of oak. However, with the onset of land-use development, a significant decline in oak relative to increasing birch was apparent, particularly after the early 1960s. These results suggest that successive logging since the 1880s had gradually undermined the resilience of oak. An increase of Artemisia and birch pollen also indicates an expansion of disturbed land. Since the 1960s, a large part of the broadleaved forests in Takkobu has been converted to larch plantations, although this was not represented in the pollen data because of the underrepresentation of larch pollen. The results of the pollen analysis have implications for forest restoration in Takkobu. The use of long-term data allows the determination of the baseline (natural) vegetation to be restored, and also illustrates the factors affecting present-day vegetation and how it may change in the future.

The Significance of Meander Restoration for the Hydrogeomorphology and Recovery of Wetland Organisms in the Kushiro River, a Lowland River in Japan

“…More than 80% of the wetland consists of low peatlands dominated by reed, sedge, and alder trees. Forests in the headwaters of the Kushiro River have been heavily exploited for charcoal and timber production since the 1880s (Ahn et al ; Kumagai et al ).…”

Recent history of sediment dynamics in Lake Toro and applicability of 210Pb dating in a highly disturbed catchment in northern Japan

“…They mainly used the area for crop cultivation and timber harvesting, but their exploitation of natural resources was very limited. Japanese settlement around the lake catchment started in the 1880s, and the forest was partly harvested for charcoal production (Shibecha Choushi Hensaniinkai, 2002;Kumagai et al, 2008). The road was constructed in 1939 to promote milk production and group settlement (Shibecha Choushi Hensaniinkai, 2002).…”

“…The catchment was the most popular Ainu settlement site in the Kushiro Mire because of natural resources such as water, forests, and fertile soil. As the Japanese settlement began in the 1880 s, indigenous forest was partly cleared for charcoal production (Kumagai et al, 2008). Group settlement in the Lake Toro catchment occurred after road construction in 1939, and the dairy industry was established (Shibecha Choushi Hensaniinkai, 2002).…”

Recent Changes of Sedimentation Rate in Lake Takkobu, Northern Japan, Determined210Pb Dating

“…토지이용 변화로 인해 산림에서 생산된 토사는 바다까지 유출·퇴적되고 있어 토사의 이 동 범위는 매우 광범위하다고 할 수 있다. 특히 유출된 토 사는 장기간동안 호수와 범람원 등에 퇴적되어 수질, 지 형과 식생 등의 자연생태계를 변화시키는 원인이 되고 있다 (Ahn et al, 2006;2008;2009;2010; Ahn and Nakamura, 토사를 습지와 호수 등으로 유입·퇴적시키고 있다 (Nakamura et al, 1997;2004;Ahn et al, 2006;Mizugaki et al, 2006;Ahn and Nakamura, 2009). …”