Role of secondary metabolites of wild marigold in suppression of Johnson grass and Sun spurge

Objective: To analyze the wild marigold [(Tagetes minuta L.)(T. minuta)] leaf extract with respect to phytochemicals and allelopathic activity. Methods: The aqueous extracts of T. minuta leaves at concentrations of 50%, 75% and 100% were prepared. Preliminary phytochemical analysis was carried out and then allelopathic ef ect of T. minuta on root length, shoot length, germination, fresh and dry weight of Johnson grass and Sun spurge was tested on i lter paper and in soil.Results: Qualitative phytochemical analysis showed the presence of alkaloids, tannins, saponins, l avonoides and terpenoids. The higher concentrations proved to be signii cantly ef ective in reducing almost all the parameters of Sun spurge and Johnson grass in i lter paper bioassay. Supplemented with the soil, all concentrations of leaf extract showed reduction in germination, root and shoot growth, fresh and dry weight of Sun spurge; however, 100% concentration signii cantly reduced the germination of Johnson grass. Conclusions: This study suggests that marigold allelochemicals can be used as an integrated weed management for the production of better crop yield.

Variation of Soil Nutrition in a Fagus engleriana Seem.-Cyclobalanopsis oxyodon Oerst, Community Over a Small Scale in the Shennongjia Area, China

Soil nutrition is a key factor influencing species composition in a community, but it has clearly scaledependent heterogeneity. In the present study, geostatistics methods and canonical correspondence analysis （CCA） were used to detect： （i） the variation range of soil spatial heterogeneity; （ii） the influence of topographic factors on the distribution of soil nutrition; and （iii） the relationships between soil chemical properties and species in the community. In all, 23 soil variables were measured, including total N and organic C, AI, Ba, Ca, Cr, Cu, Fe, Ga, Li, Mg, Mn, Na, NH4-N, Ni, NO3-N, Pb, pH, P, Sr, Ti, V, and Zn. Semi-variograms of these variables were calculated and mapped. All indices showed autocorrelatlons, with ranges between 29 and 200 m. When the sample method was larger than these distances, spatial autocorrelations were avoided. The distribution patterns of Ca, Cr, Ga, K, Mg, organic C, P, Pb, and pH, and total N were related to the microtopography and the distribution of these compounds was clumped in water catchments area. The CCA method was used to investigate the relationship between plant species and soil properties in this community. Fagus engleriana Seem., Lindera obtusiloba BI. Mus., and Acer griseum （Franch.） Pax were correlated with organic C, available N, and P.

The PCA index for measuring functional diversity and its application to Juglans mandshurica communities in the Beijing mountains~ China

Methods for measuring functional diversity are essential for functional studies of plant communities. A useful method, the PCA index, based on principal component analy- sis ordination of functional trait data was introduced and applied to functional diversity analysis of Juglans mandshurica communities in the Beijing Mountains. Thirty-five 10 m×10 m quadrats were established in Juglans mandshurica communities. Species composition, functional traits and environmental factors were measured and recorded. The four common indices, FAD, MFAD, FDp and FDc, were used and compared with the PCA index in the analysis. The results showed that the PCA index was successful in quantifying functional diversity and describing its relationships with environmental variables; therefore, it was an effective index in functional diversity analyses. Functional diversity in Juglans mandshurica communities varied widely. Elevation and aspect were the key factors affecting functional diversity in communities. Functional diversity increased with elevation increases and with the change in aspect from North to South. Functional diversity was significantly correlated with species richness and heterogeneity.