and methanotrophs have been evidenced in forest soils, suggesting changes in soil N
cycling (e.g. Liu et al. 2016; Tang et al. 2016).
9.4.3 Impacts of Nitrogen Deposition on Soil Enzymes
Soil extracellular enzymes catalyse many key reactions in the processes of organic
matter decomposition and nutrient mineralization in forest soils (Baldrian and
Štursová 2010). Several studies have investigated the latitude patterns and their
driven factors of soil enzyme activities in China’s forest. Across a transect from
boreal forest to subtropical forest in China, Wang et al. (2015) found significantly
higher activities of chitinase and β-glucosaccharase in temperate forest than in
subtropical forest, mainly due to a shift in soil pH. In a cross-site study, Xu et al.
(2017) observed higher activity of acid phosphatase in subtropical and tropical
forests than in temperate forests, supporting the P limitation hypothesis in tropical
regions. In addition, they found that climate (mean annual temperature and precipitation) and soil properties (soil C:P and N:P ratio, soil pH) are the main abiotic
factors affecting soil enzyme activities.
The impacts of N deposition on soil enzymes in China’s forest ecosystems have
been intensively examined during recent years. The results indicate inconsistent
responses of soil enzymes to N deposition, depending on N forms, N doses, duration
of N application and the interaction of N additions with the other factors (Guo et al.
2011, 2017; Wang et al. 2011; Zhao et al. 2014; Dong et al. 2015; Yang et al. 2015;
Chen et al. 2016). For instance, Jing et al. (2017) assess the effect of N deposition on
seven soil enzymes (β-1,4-glucosidase, cellobiohydrolase, phenol oxidase, peroxidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase, acid phosphatase)
across six temperate/subtropical forest ecosystems in eastern China and generally
found no significant response of these enzymes and their stoichiometry to 4–5 years
of N addition (50 and 100 kg N ha
À1 year
À1 ). Guo et al. (2011) reported that the
addition of mixed inorganic and organic N increases soil enzyme activities in a
subtropical forest. They concluded that N forms and the ratio of inorganic and
organic N are main factors mediating soil enzyme activities in response to N
deposition. At the same site, Wang et al. (2011) found that ammonium, nitrate,
urea and a mix of all three increased soil enzymes (i.e. catalase, cellulase, invertase,
polyphenol oxidase, nitrate reductase, urease and acid phosphatase) in litter. In
addition, Huang et al. (2012a) observed that acid phosphatase does not respond to
low-level N addition rate but is decreased in medium-level N addition in the early
succession stage of a subtropical forest. They also found acid phosphatase is
depressed by high-level N addition in late forest succession stage. However, Du
et al. (2014b) found no significant responses of seven soil enzymes to N addition in
temperate coniferous plantations. However, in a nearby larch plantation, the effect of
N addition has been evidenced to vary with stand age and differ between soil layers
(litter and mineral soil) (Ma et al. 2013).
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E. Du et al.
cycling (e.g. Liu et al. 2016; Tang et al. 2016).
9.4.3 Impacts of Nitrogen Deposition on Soil Enzymes
Soil extracellular enzymes catalyse many key reactions in the processes of organic
matter decomposition and nutrient mineralization in forest soils (Baldrian and
Štursová 2010). Several studies have investigated the latitude patterns and their
driven factors of soil enzyme activities in China’s forest. Across a transect from
boreal forest to subtropical forest in China, Wang et al. (2015) found significantly
higher activities of chitinase and β-glucosaccharase in temperate forest than in
subtropical forest, mainly due to a shift in soil pH. In a cross-site study, Xu et al.
(2017) observed higher activity of acid phosphatase in subtropical and tropical
forests than in temperate forests, supporting the P limitation hypothesis in tropical
regions. In addition, they found that climate (mean annual temperature and precipitation) and soil properties (soil C:P and N:P ratio, soil pH) are the main abiotic
factors affecting soil enzyme activities.
The impacts of N deposition on soil enzymes in China’s forest ecosystems have
been intensively examined during recent years. The results indicate inconsistent
responses of soil enzymes to N deposition, depending on N forms, N doses, duration
of N application and the interaction of N additions with the other factors (Guo et al.
2011, 2017; Wang et al. 2011; Zhao et al. 2014; Dong et al. 2015; Yang et al. 2015;
Chen et al. 2016). For instance, Jing et al. (2017) assess the effect of N deposition on
seven soil enzymes (β-1,4-glucosidase, cellobiohydrolase, phenol oxidase, peroxidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase, acid phosphatase)
across six temperate/subtropical forest ecosystems in eastern China and generally
found no significant response of these enzymes and their stoichiometry to 4–5 years
of N addition (50 and 100 kg N ha
À1 year
À1 ). Guo et al. (2011) reported that the
addition of mixed inorganic and organic N increases soil enzyme activities in a
subtropical forest. They concluded that N forms and the ratio of inorganic and
organic N are main factors mediating soil enzyme activities in response to N
deposition. At the same site, Wang et al. (2011) found that ammonium, nitrate,
urea and a mix of all three increased soil enzymes (i.e. catalase, cellulase, invertase,
polyphenol oxidase, nitrate reductase, urease and acid phosphatase) in litter. In
addition, Huang et al. (2012a) observed that acid phosphatase does not respond to
low-level N addition rate but is decreased in medium-level N addition in the early
succession stage of a subtropical forest. They also found acid phosphatase is
depressed by high-level N addition in late forest succession stage. However, Du
et al. (2014b) found no significant responses of seven soil enzymes to N addition in
temperate coniferous plantations. However, in a nearby larch plantation, the effect of
N addition has been evidenced to vary with stand age and differ between soil layers
(litter and mineral soil) (Ma et al. 2013).
198
E. Du et al.