Effect of organic amendment amount on soil nematode community structure and metabolic footprints in soybean phase of a soybean-maize rotation on Mollisols

It has been well documented that organic amendment affects soil nematode community structure.However,little is known about the effect of organic amendment amount on soil nematodes.To assess the effect of the amount of organic amendments on soil nematode community structure and metabolic activity,the community composition,abundance,and metabolic footprints of soil nematodes were determined in a long-term field experiment with various amounts of organic amendment in Northeast China.Fertilization treatments included an unfertilized control(CK),chemical fertilizer without manure amendment(OM0),manure applied at 7.5 Mg ha^-1 plus chemical fertilizer(OM1),and manure applied at 22.5 Mg ha^-1 plus chemical fertilizer(OM2).A total of 46 nematode genera were found.Treatments with the largest amount of organic amendment had the smallest number of plant parasite genera(5),but a largest number of dominant genera(7).Soil nematodes,bacterivores,and fungivores were the most abundant in OM2,followed by OM1,and the lowest in OM0 and CK.Organic amendment increased the enrichment index(EI),and the large amount of organic amendment increased the metabolic footprints of bacterivore(Baf)and fungivore(Fuf)and enrichment footprint(Ef).The relationships between Baf(or Fuf)and the increases in soil organic carbon(?SOC)and total nitrogen(?TN)were stronger than those of bacterivore(or fungivore)abundance with?SOC and?TN,except for the relationship between bacterivore abundance and ?SOC.The EI and Ef were positively correlated with ?SOC and ?TN.These findings suggest that the amount of organic amendment affects soil nematode activity and function at entry levels in soil food web,and that metabolic footprints of soil nematodes may be better indicators than their abundances in assessing their relationships with soil nutrients.

Identifying porphyry-Cu geochemical footprints using local neighborhood statistics in Baft area, Iran

Identifying geochemical anomalies related to ore deposition processes facilitates the practice of vectoring toward undiscovered mineral deposit sites.In districtscale exploration studies,analysis of dispersion patterns of ore-forming elements results in more-reliable targets.Therefore,deriving significant geochemical footprints and mapping the ensuing geochemical anomalies are of important issues that lead exploration geologists toward anomaly sources,e.g.,mineralization.This paper aims to examine the effectiveness of local relative enrichment index and singularity mapping technique,as two methods of local neighborhood statistics,in the delineation of anomalous areas for further exploration.A data set of element contents obtained from stream sediment samples in Baft area,Iran,therefore was applied to illustrate the procedure proposed.The close relationship between anomalous patterns recognized and known Cu-occurrences demonstrated that the procedures proposed can efficiently model complex dispersion patterns of geochemical anomalies in the study area.The results showed that singularity mapping method is a better technique,compared to local relative enrichment index,to delineate targets for follow-up exploration in the area.We made this comparison because,as pointed out by exploration geochemists,dispersion patterns of geochemical indicators in stream sediments vary in different areas even for the same deposit type.The variety in the dispersion patterns is due to the operation of post-mineralization subsystems,which are affected by local factors such as landscape of the areas under study.Therefore,the effectiveness of the methods should be evaluated in every area for every targeted deposit.

Evaluation of heavy metal contamination hazards in nuisance dust particles, in Kurdistan Province, western Iran

The effects of natural andgeochemical factors depending on heavy metal contamination in nuisance dust particles were evaluated. The nuisance dust particles were sampled using passive deposit gauge method for one year from April2010 to March2011 and the obtained samples were measured for the total contents and the contamination levels of Fe, Mn, Cu and As usinggeo-accumulation index （Igeo ）, enrichment factor （EF） and the integrated pollution index （IPI）. The results showed that, the contamination levels of Fe and Mn based on Igeo values, were uncontaminated （Igeo 〈 0） （variations of the Igeo index was from -3.11 to -1.751 for Fe, from -0.630 to -1.925 for Mn）, while the values of Cu and As were demonstrated to have moderate contamination based on Igeo values （variations of Igeo index was from -1.125 to 0.848 for Cu, and from -2.002 to 1.249 for As）. The analysis of EF also revealed minor to moderate enrichment for Mn （1.215-4.214）, minor to moderately severe enrichment for Cu （2.791-6.484）, and As （1.370-8.462）, respectively. The variation of the IPI index also showed low to moderate level of heavy metal pollution in nuisance dust particulates （0.511-1.829）. The analysis of the results also approved that the natural processes andgeochemical variables （the changing meteorological parameters） can significantly affect the availability of heavy metals in nuisance dust particles in Western Iran.