litter quality at species level and changing community structure and thus regulate the
processes of litter decomposition and nutrient cycling in grassland ecosystems
through a plant-mediated pathway.
Nitrogen deposition would influence litter decomposition through altering characters of both litter and soils. The impacts of N deposition on litter decomposition
would be dependent on plant growth forms. For example, N addition enhanced litter
mass loss of a grass, Stipa krylovii, but had no impacts on that of a forb species,
Artemisia frigida (Wang et al., 2017). Consequently, changes in community composition following N enrichment would affect litter decomposition. The positive
effects of N deposition on litter decomposition by its positive impacts on litter
quality would be offset by the negative effect of increased soil N availability (Liu
et al. 2010). The negative impacts of increasing soil N availability on litter decomposition could be accounted for by the decreases of soil microbial biomass and
activity. To disentangle the relative contribution of litter quality and soil characteristics on litter decomposition and home-field advantage effects, Li et al. (2017)
carried out microcosm experiments with litter and soil samples from a long-term N
deposition field experiment (Fig. 10.4). They found that litter decomposition on
standard soils was influenced by N addition treatment though showing no consistent
trend with increasing N addition rates. The decomposition of standard litter on soils
collected from different N treatments was reduced, whereas litter decomposition on
soil collected from the same plot was increased with increasing N addition rates. The
results from Li et al. (2017) indicate that N deposition would decrease the capability
of soils to decompose litter and increase the home-field advantage effect due to the
specialization of soil communities.
10.4 Impacts on Greenhouse Gas Emissions
Nitrogen deposition interactively with precipitation and temperature factors affected
greenhouse gas (GHG) emissions in natural ecosystems under global change. Nitrogen deposition alters fluxes of GHG by affecting plant and microbial activities which
are associated with GHG emission directly (Liu and Greaver 2009). Recently, the
effects of simulated nitrogen deposition on CO 2 , CH 4 , and N 2 O have been studied in
grassland ecosystems in the Inner Mongolia, Qinghai-Tibetan Plateau, Tian Shan
mountains of China. Three main GHG emissions vary greatly in different grassland
types.
10.4.1 CO 2
Soil organic matter decomposition and root and rhizomicrobial respiration are
associated with CO 2 emission. Nitrogen addition reduced CO 2 emission in temperate
grasslands/steppes, and N addition did not affect the seasonal emissions of CO 2 in a
10 Impacts of Nitrogen Deposition on China’s Grassland Ecosystems
225
processes of litter decomposition and nutrient cycling in grassland ecosystems
through a plant-mediated pathway.
Nitrogen deposition would influence litter decomposition through altering characters of both litter and soils. The impacts of N deposition on litter decomposition
would be dependent on plant growth forms. For example, N addition enhanced litter
mass loss of a grass, Stipa krylovii, but had no impacts on that of a forb species,
Artemisia frigida (Wang et al., 2017). Consequently, changes in community composition following N enrichment would affect litter decomposition. The positive
effects of N deposition on litter decomposition by its positive impacts on litter
quality would be offset by the negative effect of increased soil N availability (Liu
et al. 2010). The negative impacts of increasing soil N availability on litter decomposition could be accounted for by the decreases of soil microbial biomass and
activity. To disentangle the relative contribution of litter quality and soil characteristics on litter decomposition and home-field advantage effects, Li et al. (2017)
carried out microcosm experiments with litter and soil samples from a long-term N
deposition field experiment (Fig. 10.4). They found that litter decomposition on
standard soils was influenced by N addition treatment though showing no consistent
trend with increasing N addition rates. The decomposition of standard litter on soils
collected from different N treatments was reduced, whereas litter decomposition on
soil collected from the same plot was increased with increasing N addition rates. The
results from Li et al. (2017) indicate that N deposition would decrease the capability
of soils to decompose litter and increase the home-field advantage effect due to the
specialization of soil communities.
10.4 Impacts on Greenhouse Gas Emissions
Nitrogen deposition interactively with precipitation and temperature factors affected
greenhouse gas (GHG) emissions in natural ecosystems under global change. Nitrogen deposition alters fluxes of GHG by affecting plant and microbial activities which
are associated with GHG emission directly (Liu and Greaver 2009). Recently, the
effects of simulated nitrogen deposition on CO 2 , CH 4 , and N 2 O have been studied in
grassland ecosystems in the Inner Mongolia, Qinghai-Tibetan Plateau, Tian Shan
mountains of China. Three main GHG emissions vary greatly in different grassland
types.
10.4.1 CO 2
Soil organic matter decomposition and root and rhizomicrobial respiration are
associated with CO 2 emission. Nitrogen addition reduced CO 2 emission in temperate
grasslands/steppes, and N addition did not affect the seasonal emissions of CO 2 in a
10 Impacts of Nitrogen Deposition on China’s Grassland Ecosystems
225