Soil nematodes are one of the most commonly used indicators of soil food web conditions and can be grouped into 16 functional guilds. 

Nematode guilds are assigned with different weighting factors in the formulas used to calculate indices. However, these weighting factors for nematode guilds are somewhat arbitrary and require refinement. So far, no methodology has been developed to re-assess the cp scale and weighting system of nematodes. 

A team of researchers in the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) employed three data sets to calculate the indices using guild-based weighting and genus-based weighting. 

The researchers found that the genus-based weighting factors were quadratically correlated with guild-based weighting factors, but were highly variable within each nematode guild, which indicated a likely missing during the use of guild-based weighting. "Although variation patterns of indices in response to management practices and land use were often similar for the two weighting systems, they sometimes differed substantially, and the specific index values frequently differed depending on which weighting system was used." said lead researcher Dr ZHAO Jie from ISA. "The absolute values of the indices were frequently found to be different between the two weighting systems. Moreover, the genus-based system was found to complementary rather than superior to the guild-based system." Besides, both weighting systems were suggested to be used for the calculation of the nematode community indices in a study for a better distinction between the treatment effects. 

This study was supported by the Chinese Academy of Sciences Action Plan for the Development of Western China (KZCX2-XB3-10), two NSFC programs (41471445 and 31270551), the program of the Youth Innovation Promotion Association of Chinese Academy of Sciences (2015303), and a Western Light Program from CAS. 

The study entitled "Using the biomasses of soil nematode taxa as weighting factors for assessing soil food web conditions" has been published in Volume 60, Issue 2016 of Ecological Indicators, details could be found at http://www.sciencedirect.com/science/article/pii/S1470160X1500326X 

Contact: WANG Kelin 

E-mail: kelin@isa.ac.cn 

Institute of Subtropical Agriculture, Chinese Academy of Sciences