Yilai Lou

Four years of free-air CO2 enrichment enhance soil C concentrations in a Chinese wheat field.

Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems. The effects of free-air CO2 enrichment (FACE) and N fertilization on soil organic C (Corg), dissolved organic C (DOC), microbial biomass C (Cmic) and soil basal respiration (SBR) were investigated in a Chinese wheat field after expose to elevated CO2 for four full years. The results indicated that elevated CO2 has stimulative effects on soil C concentrations regardless of N fertilization. Following the elevated CO2, the concentrations of Corg and SBR were increased at wheat jointing stage, and those of DOC and Cmic were enhanced obviously across the wheat jointing stage and the fallow period after wheat harvest. On the other hand, N fertilization did not significantly affect the content of soil C. Significant correlations were found among DOC, Cmic, and SBR in this study.

Nematode community structure as bioindicator of soil heavy metal pollution along an urban?rural gradient in southern Shenyang, China

Effects of heavy metals caused by urbanisation on soil nematode communities were investigated along an urban?suburban?rural gradient in southern Shenyang, China. The numbers of total nematodes increased significantly along the urban?rural gradient. Similar trends were observed in the values of Structure Index (SI), with lower values found in urban site and higher in the rural site. Generic richness and SI were sensitive indicators for assessing the effect of heavy metals on soil nematode communities. The Canonical Correspondence Analysis (CCA) indicated that copper concentration and Cation Exchange Capacity (CEC) were most important environmental parameters that influenced nematode distribution.

Community diversity, structure and carbon footprint of nematode food web following reforestation on degraded Karst soil

We examined community diversity, structure and carbon footprint of nematode food web along a chronosequence of T. Sinensis reforestation on degraded Karst. In general, after the reforestation: a serious of diversity parameters and community indices (Shannon-Weinier index (H′), structure index (SI), etc.) were elevated; biomass ratio of fungivores to bacterivores (FFC/BFC), and fungi to bacteria (F/B) were increased, and nematode channel ratio (NCR) were decreased; carbon footprints of all nematode trophic groups, and biomass of bacteria and fungi were increased. Our results indicate that the Karst aboveground vegetation restoration was accompanied with belowground nematode food web development: increasing community complexity, function and fungal dominance in decomposition pathway, and the driving forces included the bottom-up effect (resource control), connectedness of functional groups, as well as soil environments.

Long-term effects of nitrogen fertilization on aggregation and localization of carbon, nitrogen and microbial activities in soil

Long-term nitrogen (N) fertilization affects soil aggregation and localizations of soil organic carbon (SOC), N and microbial parameters within aggregates. The mechanisms of these N effects are poorly understood. We studied these processes in a loamy soil from a 23-year repeated N addition field experiment under a rice-barley rotation. Nitrogen fertilization increased plant productivity and the portion of large macroaggregates (>2mm). However, SOC contents in macro- and micro-aggregates remained constant despite an N-induced increase of 27% in root C input into soil. Therefore, N fertilization accelerated SOC turnover. Nitrogen addition increased total N (TN) content in bulk soil and two macroaggregates (>2, and 1-2mm), but not in microaggregates (<0.25mm). Also, N fertilization increased the phospholipid fatty acids (PLFAs) contents of fungi in the large macroaggregates, but not in the microaggregates. In contrast, the effect of N addition on contents of bacterial and total microbial PLFAs was not apparent. Nitrogen fertilization increased N-acetyl-β-D-glucosaminidase (NAG) activities in the two larger macroaggregate size classes (>2, and 1-2mm), but not in the aggregates (<1mm). In both control and N fertilization, the large macroaggregates localized more TN, microbial PLFAs, and NAG activities than the microaggregates. In conclusion, long-term N fertilization not only directly promotes soil N resource but also indirectly improves soil structure by forming large macroaggregates, accelerates SOC turnover, and shiftes localization of microorganisms to the macroaggregates.