Effects, and Their Mechanisms, of Temporal and Special Continuity in Grasslands on Plants- and Butterflies- communities

概要

Grasslands are terrestrial ecosystems with high biodiversity (Akeroyd & Page, 2011; J. B. Wilson et
al., 2012). However, all over the world, natural grasslands have been lost through conversion to farmland,
with 50% of the world's grasslands disappearing between 1700 and 1990 (Boakes et al., 2010; Goldewijk,
2001) . Semi-natural grasslands, where forestation has been prevented by burning, mowing, and grazing,
and where agricultural use has been promoted, are widespread, especially in Europe and East Asia.
Semi-natural grasslands are declining due to management abandonment and afforestation (Dengler &
Tischew, 2018)。These land use changes are one of the main causes of biodiversity loss (Gerstner et al.,
2014; Sala et al., 2000).
In Japan, natural grasslands existed during the glacial period in a cold and dry climate and were
inhabited by grassland species introduced from the continent (Suka, 2008) . Post-glacial warming and
wetting decreased natural grasslands, but human activities have increased semi-natural grasslands,
which have functioned as refugia for grassland plants and animals. Semi-natural grasslands have been
used for agriculture, but after the 1950s, with the advent of chemical fertilizers and agricultural
machinery, the demand for grassland-dependent livestock and manure decreased. This led to
abandonment of management, forestation through afforestation, and conversion to other land uses. As a
result, grasslands, which covered more than 13% of the country's land area in the 1900s, have been
reduced to approximately 1% at the present time (Ogura, 2006). Due to the rapid decline of grasslands,
grassland plants and animals are in danger of extinction (Kaneko et al., 2009; Nakamura, 2010).This
decline in biodiversity due to inactive land use is considered by the Ministry of the Environment of
Japan to be a "second crisis" of biodiversity (Ministry of the Environment of Japan, 2012).
Grassland management such as burning, mowing, and grazing is necessary to protect the biodiversity
of semi-natural grasslands. In the past, grassland management was carried out with a great deal of effort
for social and economic reasons, but now that the motivation for such grassland management has greatly
decreased, it is not realistic to aim for the same level of grassland management for the same area as in
the past. Therefore, it is necessary to identify grasslands that should be prioritized for grassland
management to conserve biodiversity. As an indicator of grassland biodiversity, I focus on the vegetation
history of grasslands. In recent years, it has been successively reported that the duration of grassland
affects the current biological community. It has been reported that grasslands with longer duration have
higher plant diversity (Cousins & Eriksson, 2002; Straubinger et al., 2022) , that duration affects the
diversity and community of arbuscular mycorrhizal fungi (Honnay et al., 2017) , and that grasslands
with longer duration endangered species have been reported (Yaida et al., 2019) . Investigating the
impact of vegetation history on the biodiversity of current grassland plant species not only provides
valuable insights for assigning conservation priorities, but also enhances our understanding of the
processes by which biological communities are formed. However, few studies to date have investigated
whether plant and animal community structure changes (e.g. Honnay et al., 2017). These temporal
effects of vegetation history also interact with spatial scale. Both the temporal continuity and spatical
area of habitats have positive effects on the number of grassland plants species(Noda et al., 2022). ...

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