9.2 Overview of the Manipulated Nitrogen Deposition
Experiments
9.2.1 History of the Manipulated Nitrogen Deposition
Experiments
Knowledge of how N deposition affects ecosystem processes is mostly achieved
from the manipulated experiments. To assess the ecological effects of elevated N
deposition, many manipulated experiments were established since 1980s in Europe
(e.g. the Nitrogen Saturation Experiments, NITREX; the Experimental Manipulation
of Forest Ecosystems in Europe, EXMAN) and North America (e.g. chronic nitrogen
addition experiment in Harvard Forest), when both regions have been experiencing
high-level atmospheric N deposition (Tietema et al. 1995; Wright and Rasmussen
1998; Magill et al. 2004). The NITREX project, initiated in the late 1980s, is a crosssite network of large-scale manipulation experiments under the auspices of the
Commission of European Communities (Wright and Rasmussen 1998). The
NITREX project comprises ten experiments at eight forested sites in seven countries
that either added external N or removed ambient N deposition (Tietema et al. 1995;
Wright and Rasmussen 1998). The EXMAN project was established in 1987 at six
sites in four countries, and the key objective was to understand the ecological effects
of atmospheric deposition by manipulating the amount of chemical components and
water deposited (Wright and Rasmussen 1998). In the United States, a chronic N
addition experiment in Harvard Forest has been established since 1988, which is an
important component of the Harvard Forest Long-Term Ecological Research
(LTER) project (Magill et al. 2004). These efforts have greatly improved our
understanding on how elevated N deposition affects temperate and boreal forest
ecosystems in Europe and North America.
The environmental issue of acid deposition in China was recognized in the early
1980s, and early research efforts mainly focused on the role of sulphur deposition
(Zhao and Sun 1986; Larssen et al. 1999). As national measures have been taken to
reduce SO 2 emissions since the 1990s, the role of N deposition becomes increasingly
important. Since the early 2000s, manipulated N addition experiments have been
emerging in various ecosystems in China (Liu et al. 2011). A well-known example is
the Long-term Nitrogen Research Project in the Dinghushan Biosphere Reserve in
Guangdong Province, South China, which was initiated in 2003 (Mo et al. 2008).
The experimental results have substantially improved our understanding of subtropical forests in response to elevated N deposition (Mo et al. 2008; Lu et al. 2010.
2014; Liu et al. 2013b). To assess and predict how ecological processes respond to
increasing N deposition in China’s forests, a cross-site network of Nutrient Enrichment Experiments in China’s Forests (NEECF) was established in 2010 (Du et al.
2013). The NEECF comprises ten experiments at seven sites located from North to
South China, covering major forest types in eastern China from boreal forest in
Greater Khingan Mountains to tropical forests in Hainan Island (Du et al. 2013).
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E. Du et al.
Experiments
9.2.1 History of the Manipulated Nitrogen Deposition
Experiments
Knowledge of how N deposition affects ecosystem processes is mostly achieved
from the manipulated experiments. To assess the ecological effects of elevated N
deposition, many manipulated experiments were established since 1980s in Europe
(e.g. the Nitrogen Saturation Experiments, NITREX; the Experimental Manipulation
of Forest Ecosystems in Europe, EXMAN) and North America (e.g. chronic nitrogen
addition experiment in Harvard Forest), when both regions have been experiencing
high-level atmospheric N deposition (Tietema et al. 1995; Wright and Rasmussen
1998; Magill et al. 2004). The NITREX project, initiated in the late 1980s, is a crosssite network of large-scale manipulation experiments under the auspices of the
Commission of European Communities (Wright and Rasmussen 1998). The
NITREX project comprises ten experiments at eight forested sites in seven countries
that either added external N or removed ambient N deposition (Tietema et al. 1995;
Wright and Rasmussen 1998). The EXMAN project was established in 1987 at six
sites in four countries, and the key objective was to understand the ecological effects
of atmospheric deposition by manipulating the amount of chemical components and
water deposited (Wright and Rasmussen 1998). In the United States, a chronic N
addition experiment in Harvard Forest has been established since 1988, which is an
important component of the Harvard Forest Long-Term Ecological Research
(LTER) project (Magill et al. 2004). These efforts have greatly improved our
understanding on how elevated N deposition affects temperate and boreal forest
ecosystems in Europe and North America.
The environmental issue of acid deposition in China was recognized in the early
1980s, and early research efforts mainly focused on the role of sulphur deposition
(Zhao and Sun 1986; Larssen et al. 1999). As national measures have been taken to
reduce SO 2 emissions since the 1990s, the role of N deposition becomes increasingly
important. Since the early 2000s, manipulated N addition experiments have been
emerging in various ecosystems in China (Liu et al. 2011). A well-known example is
the Long-term Nitrogen Research Project in the Dinghushan Biosphere Reserve in
Guangdong Province, South China, which was initiated in 2003 (Mo et al. 2008).
The experimental results have substantially improved our understanding of subtropical forests in response to elevated N deposition (Mo et al. 2008; Lu et al. 2010.
2014; Liu et al. 2013b). To assess and predict how ecological processes respond to
increasing N deposition in China’s forests, a cross-site network of Nutrient Enrichment Experiments in China’s Forests (NEECF) was established in 2010 (Du et al.
2013). The NEECF comprises ten experiments at seven sites located from North to
South China, covering major forest types in eastern China from boreal forest in
Greater Khingan Mountains to tropical forests in Hainan Island (Du et al. 2013).
188
E. Du et al.