Asynchronous responses of soil microbial community and understory plant community to simulated nitrogen deposition in a subtropical forest

Abstract

Atmospheric nitrogen (N) deposition greatly affects ecosystem processes and properties. However, few studies have simultaneously examined the responses of both the above- and belowground communities to N deposition. Here, we investigated the effects of 8 years of simulated N deposition on soil microbial communities and plant diversity in a subtropical forest. The quantities of experimental N added (g of N m−2 year−1) and treatment codes were 0 (N0, control), 6 (N1), 12 (N2), and 24 (N3). Phospholipid fatty acids (PLFAs) analysis was used to characterize the soil microbial community while plant diversity and coverage were determined in the permanent field plots. Microbial abundance was reduced by the N3 treatment, and plant species richness and coverage were reduced by both N2 and N3 treatments. Declines in plant species richness were associated with decreased abundance of arbuscular mycorrhizal fungi, increased bacterial stress index, and reduced soil pH. The plasticity of soil microbial community would be more related to the different responses among treatments when compared with plant community. These results indicate that long-term N deposition has greater effects on the understory plant community than on the soil microbial community and different conservation strategies should be considered.

Spatial and Temporal Variation in Soil Nitrous Oxide Emissions from a Rehabilitated and Undisturbed Riparian Forest

“…Stand density was quantified using three randomly located quadrats (5 m by 5 m), and distance (m) from each chamber to the nearest tree was also determined. Illuminance, an indicator of canopy cover (Wu et al, 2013), was measured at midday in each 5‐m by 5‐m quadrat using a light meter (Nicety LX802). The difference between open sky and canopy readings was quantified as percentage of light penetration.…”

Impacts of nitrogen deposition on soil nitrogen cycle in forest ecosystems: A review

“…Moore et al [69] examined the patterns of N and P dynamic during decomposition in ten foliar tissues over 6 years at 18 upland forests in Canada; they found that net N release started when the average C/N ratios of leaf litter are less than 55 and litter accumulated more N in the sites with high soil N availability. The changes Wu et al [57] of litter initial N content, litter C/N ratio, and soil N availability caused by N deposition, may affect the pattern of N immobilization and mineralization. Perakis et al [63] examined relationships between initial N concentration (0.67-1.31%), decomposition, and N dynamics in both ambient and N fertilized (150 kg N hm −2 year −1 ) plots at four Douglas fir forests over 3 years.…”

“…Stemflow acidification caused by N deposition altered the biomass and community composition of tree mosses and lichens, and then reduced their BNF capacity. Meanwhile, soil acidification changed the understory community, which weakened soil N retention and increased the risk of N losses in these forests [57,82].…”

Effects of experimental N addition on plant diversity in an old‐growth temperate forest

“…We performed a survey documenting the stand characteristics and soil properties before N addition and found that there was no significant variation in the stand characteristics or soil properties in the N treatment sites (Mao, Chen, & Jin, ). According to previous studies with similar local N deposition amounts (Lu et al., ; Wu et al., ; Zheng et al., ), four N addition treatments (in three replicates) were established: control (0 kg N ha −1 year −1 ), low N (30 kg N ha −1 year −1 ), medium N (60 kg N ha −1 year −1 ), and high N (120 kg N ha −1 year −1 ). Applications of a CO(NH 2 ) 2 solution were initiated in June 2008.…”