9.2.2 Summary of the Manipulated Nitrogen Deposition
Experiments in China
Currently, there are more than 40 manipulated N deposition experiments across
grassland and forest ecosystems in China (Fig. 9.1). The design of these experiments
mainly considers the following aspects: (i) N forms (e.g. NH 4 NO 3 , NaNO 3 ,
(NH 4 ) 2 SO 4 and NH 4 Cl), (ii) the dose of N application, (iii) the time and frequency
of N application, (iv) the method of N application (e.g. spray as solutions or power,
application from the canopy or on the forest floor) and (v) the ambient N deposition
and background soil N availability (Du et al. 2013). For most cases, NH 4 NO 3
solutions are applied to simulate the effect of N deposition. Nitrate-N
(e.g. NaNO 3 ) and ammonium-N (e.g. (NH 4 ) 2 SO 4 ) are also used to evaluate the
effect of oxidized and reduced N deposition, respectively. In addition to N solutions,
N powders are occasionally applied to assess the effect of dry N deposition. Most N
deposition experiments in China’s forests apply N solutions or powders monthly
with three to four treatments (e.g. 0, 50, 100 and 150 kg N ha
À1 year
À1 ), while lower
N treatments (e.g. 20 kg N ha
À1 year
À1 ) are increasingly realized to be important in
view of the background level of N deposition (Du et al. 2013). Experiments with
multiple N treatments (>5 N levels) are also emerging (e.g. Geng et al. 2017a), which
are expected to improve our understanding of the non-linear effect of N deposition
(De Vries et al. 2014). Due to limited funding sources, most experiments applied N
solutions or powders to forest floor, while rare have conducted N additions to forest
canopy. Until recently, two forest canopy N addition experiments have been initiated
in Jigongshan National Natural Reserve, Henan Province, and Shimentai National
Natural Reserve, Guangdong Province, China (Zhang et al. 2015), which are
expected to improve our understanding of the interactions between N deposition
and forest canopy as well as the consequent effects on the whole ecosystems.
Fig. 9.1 Distribution of
manipulated N deposition
experiments in forests and
grasslands in China
9 Impacts of Nitrogen Deposition on Forest Ecosystems in China
189
Experiments in China
Currently, there are more than 40 manipulated N deposition experiments across
grassland and forest ecosystems in China (Fig. 9.1). The design of these experiments
mainly considers the following aspects: (i) N forms (e.g. NH 4 NO 3 , NaNO 3 ,
(NH 4 ) 2 SO 4 and NH 4 Cl), (ii) the dose of N application, (iii) the time and frequency
of N application, (iv) the method of N application (e.g. spray as solutions or power,
application from the canopy or on the forest floor) and (v) the ambient N deposition
and background soil N availability (Du et al. 2013). For most cases, NH 4 NO 3
solutions are applied to simulate the effect of N deposition. Nitrate-N
(e.g. NaNO 3 ) and ammonium-N (e.g. (NH 4 ) 2 SO 4 ) are also used to evaluate the
effect of oxidized and reduced N deposition, respectively. In addition to N solutions,
N powders are occasionally applied to assess the effect of dry N deposition. Most N
deposition experiments in China’s forests apply N solutions or powders monthly
with three to four treatments (e.g. 0, 50, 100 and 150 kg N ha
À1 year
À1 ), while lower
N treatments (e.g. 20 kg N ha
À1 year
À1 ) are increasingly realized to be important in
view of the background level of N deposition (Du et al. 2013). Experiments with
multiple N treatments (>5 N levels) are also emerging (e.g. Geng et al. 2017a), which
are expected to improve our understanding of the non-linear effect of N deposition
(De Vries et al. 2014). Due to limited funding sources, most experiments applied N
solutions or powders to forest floor, while rare have conducted N additions to forest
canopy. Until recently, two forest canopy N addition experiments have been initiated
in Jigongshan National Natural Reserve, Henan Province, and Shimentai National
Natural Reserve, Guangdong Province, China (Zhang et al. 2015), which are
expected to improve our understanding of the interactions between N deposition
and forest canopy as well as the consequent effects on the whole ecosystems.
Fig. 9.1 Distribution of
manipulated N deposition
experiments in forests and
grasslands in China
9 Impacts of Nitrogen Deposition on Forest Ecosystems in China
189