Aims Recent theories indicate that N is more in demand for plant growth than P;therefore,N concentration and N:C and N:P ratios are predicted to be positively correlated with relative growth rate(RGR)in plants under n...Aims Recent theories indicate that N is more in demand for plant growth than P;therefore,N concentration and N:C and N:P ratios are predicted to be positively correlated with relative growth rate(RGR)in plants under nutrient-enriched conditions.This prediction was tested in this study.Methods We examined the whole-plant concentrations of C,N and P and RGR,as well as the relationship between RGR and the concentrations and the ratios of N:C,P:C and N:P,for different harvest stages(the days after seed germination)of the seedlings of seven shrub species and four herbaceous species grown in N and P non-limiting conditions.The relationships among plant size,nutrient concentrations and ratios were subsequently determined.Important Findings RGR was positively correlated with N concentration and the ratios of N:PandN:C when the data were pooled for all species and for each shrub species,but not for individual herbaceous species.However,the relationship between RGR and P concentration and P:C was not significantly correlated for either shrubs or herbs.The variation of N among harvest stages and species was much greater than that of P,and the variation in N:P ratio was determined primarily by changes in N concentration.The shrub species differed from the herbaceous species in their N and P concentrations,nutrient ratios and in intraspecific relationships between RGR and nutrient ratios.These differences possibly reflect differences in the capacity for P storage and biomass allocation patterns.In general,our data support recent theoretical predictions regarding the relationship between RGR and C:N:P stoichiometry,but they also show that species with different life forms differ in the relationships among RGR and C:N:P stoichimetries.展开更多
Aims Understanding the response of farmland weed community assembly to fertilization is important for designing better nutrient management strategies in integrated farmland ecological systems.Many studies have focused...Aims Understanding the response of farmland weed community assembly to fertilization is important for designing better nutrient management strategies in integrated farmland ecological systems.Many studies have focused on weed characteristics,mainly crop–weed competition responses to fertilization or weed communities alone.However,weed community assembly in association with crop growth is poorly understood in the agroecosystems,but is important for the determination of integrated weed management.Biodiversity promotes ecosystem productivity in the grassland,but whether it applies to the agroecosystems is unclear.Based on an 11-year field experiment,the cumulative effects of different fertilization patterns on the floristic composition and species diversity of farmland weed communities along with wheat growth in a winter wheat–soybean rotation were investigated.Methods The field trial included five fertilization patterns with different combinations of N,P and K fertilizers.Species composition and diversity of weed communities,aboveground plant biomass and nutrient accumulation of weeds and winter wheat,light penetration to the ground surface and wheat yield were measured at each plot in 2009 and 2010.Multivariate analysis,regression and analysis of variance were used to analyze the responses of these parameters to the different fertilization treatments.Important Findings Four dominant weeds(Galium aparine L.,Veronica persica Poir.,Vicia sativa L.and Geranium carolinianum L.)accounted for~90%of the total weed density in the 2 years of experimental duration.The residual weed community assembly was influenced primarily by topsoil available nutrients in the order P>N>K.Competition for nutrients and solar radiation between crops and weeds was the main indirect effect of fertilization on the changes in weed community composition and species diversity.The indices of species diversity(species richness,Shannon–Wiener,Pielou and Simpson indices)showed significant linear relationships with wheat yield.The balanced fertilization treatment was more efficient at inhibiting the potential growth of weeds because of solar radiation being intercepted by wheat.These results support the conclusion that wheat yield is favored by balanced fertilization,whereas the weed community is favored by PK fertilization in terms of density and diversity.However,the negative effects on wheat yield may be compromised by simultaneous positive effects of weed communities in the fertilization treatments,for instance,the NP and NK treatments,which are intermediate in terms of increasing wheat production and to a level maintaining a diverse community.展开更多
文摘Aims Recent theories indicate that N is more in demand for plant growth than P;therefore,N concentration and N:C and N:P ratios are predicted to be positively correlated with relative growth rate(RGR)in plants under nutrient-enriched conditions.This prediction was tested in this study.Methods We examined the whole-plant concentrations of C,N and P and RGR,as well as the relationship between RGR and the concentrations and the ratios of N:C,P:C and N:P,for different harvest stages(the days after seed germination)of the seedlings of seven shrub species and four herbaceous species grown in N and P non-limiting conditions.The relationships among plant size,nutrient concentrations and ratios were subsequently determined.Important Findings RGR was positively correlated with N concentration and the ratios of N:PandN:C when the data were pooled for all species and for each shrub species,but not for individual herbaceous species.However,the relationship between RGR and P concentration and P:C was not significantly correlated for either shrubs or herbs.The variation of N among harvest stages and species was much greater than that of P,and the variation in N:P ratio was determined primarily by changes in N concentration.The shrub species differed from the herbaceous species in their N and P concentrations,nutrient ratios and in intraspecific relationships between RGR and nutrient ratios.These differences possibly reflect differences in the capacity for P storage and biomass allocation patterns.In general,our data support recent theoretical predictions regarding the relationship between RGR and C:N:P stoichiometry,but they also show that species with different life forms differ in the relationships among RGR and C:N:P stoichimetries.
基金China Program of International Plant Nutrition Institute(IPNI-HB-34)the Opening Project of Hubei Key Laboratory of Wetland Evolution&Ecological Restoration(2011-02).
文摘Aims Understanding the response of farmland weed community assembly to fertilization is important for designing better nutrient management strategies in integrated farmland ecological systems.Many studies have focused on weed characteristics,mainly crop–weed competition responses to fertilization or weed communities alone.However,weed community assembly in association with crop growth is poorly understood in the agroecosystems,but is important for the determination of integrated weed management.Biodiversity promotes ecosystem productivity in the grassland,but whether it applies to the agroecosystems is unclear.Based on an 11-year field experiment,the cumulative effects of different fertilization patterns on the floristic composition and species diversity of farmland weed communities along with wheat growth in a winter wheat–soybean rotation were investigated.Methods The field trial included five fertilization patterns with different combinations of N,P and K fertilizers.Species composition and diversity of weed communities,aboveground plant biomass and nutrient accumulation of weeds and winter wheat,light penetration to the ground surface and wheat yield were measured at each plot in 2009 and 2010.Multivariate analysis,regression and analysis of variance were used to analyze the responses of these parameters to the different fertilization treatments.Important Findings Four dominant weeds(Galium aparine L.,Veronica persica Poir.,Vicia sativa L.and Geranium carolinianum L.)accounted for~90%of the total weed density in the 2 years of experimental duration.The residual weed community assembly was influenced primarily by topsoil available nutrients in the order P>N>K.Competition for nutrients and solar radiation between crops and weeds was the main indirect effect of fertilization on the changes in weed community composition and species diversity.The indices of species diversity(species richness,Shannon–Wiener,Pielou and Simpson indices)showed significant linear relationships with wheat yield.The balanced fertilization treatment was more efficient at inhibiting the potential growth of weeds because of solar radiation being intercepted by wheat.These results support the conclusion that wheat yield is favored by balanced fertilization,whereas the weed community is favored by PK fertilization in terms of density and diversity.However,the negative effects on wheat yield may be compromised by simultaneous positive effects of weed communities in the fertilization treatments,for instance,the NP and NK treatments,which are intermediate in terms of increasing wheat production and to a level maintaining a diverse community.
