Geoscience Reference
In-Depth Information
studies aimed at developing sustainable stewardship of local, regional, and global
ecosystems that are coupled with human societies is steadily growing.
3.3
Biogeochemical Processes Coupled with Anthropogenic
Disturbances
Biogeochemistry offers a powerful scientifi c approach for understanding ecosystem
structures, functioning, and their human impacts through the analysis of material
dynamics and their driving mechanisms within different environments. In particu-
lar, for most biota, nitrogen (N) is a major limiting nutrient within biogeochemical
cycles relating to various biotic and abiotic processes and their interactions in and
across ecosystems. Moreover, N behavior is closely linked to a number of human
activities. For example, excess production and consumption of fossil fuels and food
are known to affect ecosystem structures and functioning through several processes
and mechanisms (Schlesinger
1997
; Chapin et al.
2002
; Shibata et al.
2011a
). Shibata
et al. (
2001a
) have shown that nitrate concentration in forest streams has increased
near the Kanto area in Japan. This fi nding suggests that these forests have mostly
reached N saturation (Ohte et al.
2001
) as a result of the atmospheric N pollution
produced in the Tokyo metropolitan region. Recently, air pollution (e.g., PM
2.5
) has
increased to dangerous levels for human health in China (Zhao et al.
2013
), thus
raising the risk of ecosystems and environments in the Japanese archipelago being
further impacted by long-range transport of N pollutants from the Asian continent.
Japan consists of an archipelago of fi ve main islands (Hokkaido, Honshu, Sikoku,
Kishu, and Okinawa) and over 6,800 small islands that varies widely from north to
south (20-45°N). This archipelago includes many active and inactive volcanos
forming part of the circum-Pacifi c orogenic zone. Forests cover about 66 % of the
total land area of Japan and mostly located in mountainous regions. There are
diverse topographies from steep alpine and subalpine mountainous areas to middle-
downstream fl at plains. The climate belongs mostly to the temperate zone, but has a
range from sub-tropical to sub-boreal zones, all of which are affected by the Asian
monsoon climate. These natural environmental characteristics strongly infl uence
the diverse structures and functioning of Japanese ecosystems. Regarding forest
ecosystem responses to anthropogenic air pollution, Shibata et al. (
2001b
) con-
ducted a comprehensive analysis of proton (H
+
ion) budgets in Japanese forest eco-
systems. Their fi ndings in relation to ambient levels of anthropogenic acidic
deposition indicated that relatively young bedrock derived primarily from volcanic
rock contributed to a higher acid neutralization capacity through base cation
exchanges and chemical weathering in soil.
Timber production is another major form of human disturbance to biogeochemical
processes and stream water quality in forested catchments. In northern Hokkaido,
which is at Japan's northernmost point,
Sasa
dwarf bamboo species (
Sasa kurilensis
and
S. senanensis
) are predominant forest fl oor plants that densely cover the
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