X (Xu) Han MSc

X (Xu) Han MSc

PhD student

Personal page NIOO

Research conducted by the Laboratory of Nematology is part of the research program of the Graduate School Experimental Plant Sciences (EPS) and the C.T. de Wit Graduate School for Production Ecology & Resource Conservation (PE&RC).

Research:

The effects of aboveground grazing of livestock on soil nematode community diversity, heterogeneity, and composition is expected to mainly operate via altering plant community structure and composition. In a structural equation study, abiotic soil properties had less influence on nematode community composition. Grazing effects showed up at various positions in the soil food web, reducing the numbers of bacteria and nematodes. It is known that grazing may alter the plant community structure and composition and decrease the litters and both aboveground and underground productivity of grassland; the altered plant community structure and composition could affect the soil nematode community diversity, heterogeneity, and composition. However, less is known about the effects of grazing intensity on nematode community composition, diversity, and heterogeneity, as well as consequences for soil community functioning.

Nutrient limitation of nitrogen and other compounds is common in typical grasslands in Inner Mongolia, China, and the soil nematodes that play a significant role in the soil nitrogen cycle and are important component of the soil food web. Studies showed that nitrogen addition reduced the community diversity and richness of fungi and bacteria, but it had less effects on soil animal groups (such as nematodes, mites). Bacteria-feeding nematodes have a great impact on bacteria during nitrogen mineralization, as they increased soil NH4+-N and NO3--N, and the number of Ammonia Oxidizing Bacteria (AOB) also increased[13-15]. It is not well known whether this phenomenon is due to an increase in NH4+-N, so that the nitrification was enhanced. Bacteria-feeding nematode can also enhance the nitrogen utilization efficiency of plants by hormonal regulation. However, it is still not known how effective exactly is nematodes involved in nitrogen mineralization?

Hence, my Ph.D. research aims to study how grazing affects the community structure of nematodes by altering plants community structure or by altering soil properties, and how grazing affects the structure of the soil food web by affecting nematodes. Finally, I aim at examining how nematode grazing affects the process of soil nitrogen transformation.