Land Use in
Temperate East Asia (LUTEA):
Dennis Ojima, Togtohyn Chuluun and Wang Yanfen
Natural Resource Ecology
Laboratory, Colorado State University, USA
Land
use has a long history in Temperate East Asia, and much of the ecological
landscapes have been shaped by the changing land use patterns in the past. Long-term studies of the relationships
between climate variability, ecosystem dynamics, and land use are needed to
better understand the current and future ecosystem functioning. Examples are provided from the Land Use
in Temperate East Asia (LUTEA) study of interactions between nomadic land use
and environmental conditions on the development of grassland ecosystems in the
region for hundreds of years. Land
use intensification in China have resulted in overgrazing and degradation of
grassland ecosystems, especially in the past 50 years. In Mongolia, recent political and
economic changes have resulted in an increased number of grazing animals. These recent changes in Mongolia and
long-term affects in China provides an opportunity to evaluate the resilience
of the Mongolian steppe ecosystem to changing land use intensity. The purpose of this paper is to analyze
a long-term ecosystem dynamics and land use impact on ecosystem structure and
function in this region. Climate,
soil (carbon, nitrogen and carbon isotopes) and plant (biomass, cover and
diversity) relations have been studied in ecosystems of Temperate East
Asia. The results from two long-term
steppe ecological research sites: Xilingole in China and Tumentsogt in Mongolia
have been incorporated in this paper.
Grasslands at Xilingole and Tumentsogt are dominated by cool season
grasses and soil carbon isotopic analysis shows that it has been for a long
period of time. Stipa and Leymus are the dominant grass genera. Interestingly, Cleistogenes
spp. were the only C4 species in the steppe ecosystems of this region. Soil organic carbon and nitrogen levels
were positively correlated with annual precipitation in Mongolia, but not in
China. However, there was a
decreasing trend of soil organic C and N with increase of mean annual
temperature. Soil carbon isotopes
were related better with annual precipitation than annual mean temperature,
although there is some disagreement in China. Soil carbon isotope distribution with the depth indicates a
possibility that the Stipa site was
more sensitive to past climate change than Leymus
site in Xilingole and Tumentsogt sites.
The C4 plant cover and actual plant cover increased and plant diversity
decreased with grazing in all research sites we studied. A total soil organic carbon level
decrease by about 25% was observed with heavy grazing at Xilingole research
site. A simulation model showed
that 50 years of heavy grazing in summer period may result in such change in
soil carbon level. Future research
in this region needs to focus on the integrated impact of changing political,
economic and social forces controlling livestock management, maintenance of biodiversity,
sustaining the steppe ecosystem integrity, and economic development of the
region.
The Mongolian steppe study was supported from a research grant from the
US National Science Foundation Long-term ecological studies component of the
Division of Environmental Biology and from support from the Chinese Academy of
Sciences and the Mongolian Ministry of Nature and Environment and the Mongolian
Academy of Sciences.