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991.
Jér?me?MathieuEmail author Jean-Pierre?Rossi Michel?Grimaldi Philippe?Mora Patrick?Lavelle Corinne?Rouland 《Biology and Fertility of Soils》2004,40(5):300-305
The influence of three spatially hierarchical factors upon soil macrofauna biodiversity was studied in four pasture plots in eastern Amazonia. The first factor was the local depth of the soil. The second factor was the ground cover type on the soil samples (bare ground, grass tufts, dead trees lying on the ground). The third factor was the dimensions of the grass tufts sampled (size and shape). The effect of each factor upon the morphospecies richness and density of total soil macrofauna was analysed. Detailed results are given for earthworms, termites, ants, beetles and spiders. All factors significantly affected the morphospecies richness and/or density of the soil macrofauna. The type of ground cover had the strongest influence, affecting the total richness and density of the soil macrofauna and of almost all the groups represented. The soil depth affected only the density of the termites and the global morphospecies richness. Interactions between soil depth and ground cover type affected the total macrofauna morphospecies richness and the density of the earthworms. The dimensions of the grass tuft influenced the global morphospecies richness, the morphospecies richness of the ants and the density of the spiders. 相似文献
992.
Bi-directional nitrogen transfer in an intercropping system of peanut with rice cultivated in aerobic soil 总被引:1,自引:0,他引:1
Three separate greenhouse experiments were conducted to determine the bi-directional N transfer in a peanut and rice intercropping system using the direct 15N foliar feeding technique at N application rates of 15, 75 and 150 kg ha–1. When peanut was used as the 15N donor plant, the atom % 15N in the rice shoot was consistently higher than in control rice, indicating that 15N transfer from peanut to the associated rice crop occurred. The percentage of N transfer (%NT) from peanut to the associated rice was 9.9%, 5.7% and 4.2% at the three N application rates, respectively. The N transferred from peanut to rice was 22.6, 15.5 and 8.2 mg N plant–1, accounting for 10.9%, 6.4% and 3.1% of the total N accumulated in rice plants at the three N application rates, respectively. When rice functioned as the 15N donor plant, the %NTs were 4.4%, 2.1% and 1.4% and represented about 5.2%, 3.4% and 2.4% of total N accumulated in peanut shoot at the three N application rates, respectively. The net directional N transfer was from peanut to rice and this was calculated by the difference in the bi-directional transfers and was mainly due to peanut root decomposition. Thus, the %NTs were 10.7%, 6.3%, 5.1% and 3.5% on 28 July (the day on which peanut shoots were cut), 8 August, 28 August and 8 September, respectively, and correspondingly, the N transferred from peanut to rice represented 6.0%, 5.8%, 5.1% and 3.2% of the total N accumulated in the rice plants. 相似文献
993.
The impacts of individual plant species on rhizosphere microbial communities in soils of different fertility 总被引:1,自引:0,他引:1
Louise?InnesEmail author Philip?J.?Hobbs Richard?D.?Bardgett 《Biology and Fertility of Soils》2004,40(1):7-13
To investigate the effects of individual plant species on microbial community properties in soils of differing fertility, a microcosm experiment was carried out using plant species representative of the dominant flora in semi-fertile temperate grasslands of northern England. Soil microbial biomass and activity were found to be significantly greater in the more fertile, agriculturally improved soil than in the less productive unimproved meadow soil. Differences in microbial community structure were also evident between the two soils, with fungal abundance being greater in the unimproved soil type. Individual plant species effects significantly differed between the two soils. Holcus lanatus and Anthoxanthum odoratum stimulated microbial biomass in the improved soil type, but negatively affected this measure in the unimproved soil. In both soil types, herb species generally had negative effects on microbial biomass. Patterns for microbial activity were less consistent, but as with microbial biomass, A. odoratum and H. lanatus promoted respiration, whereas the herbs negatively affected this measure. All plant species grown in the improved soil increased the abundance of fatty acids synthesised by bacteria (bacterial phospholipid fatty acid analysis) relative to bare soil, but they negatively impacted on this group of fatty acids in unimproved soil. Similarly, the abundance of the fungal fatty acid 18:26 was increased by all plants in the more fertile improved soil only, albeit non-significantly. Our data indicate that effects of plant species on microbial properties differ markedly in soils of differing fertility, making general predictions about how individual plants impact on soil properties difficult to make. 相似文献
994.
A greenhouse experiment was conducted with a specially designed apparatus consisting of an upper and lower chamber where the treatment with rice was carried out (treatment 1). The apparatus also had a single chamber where treatment 2, without rice plants, was carried out. The scope of this study was to elucidate the influence of rice plant growth on gaseous N losses as N2 and N2O produced by nitrification-denitrification in a flooded soil fertilized with (NH4)2SO4 (with 56.50 atom% 15N). Gas samples were withdrawn weekly and analyzed for (N2 + N2O)-15N losses by mass spectrometer and for N2O by gas chromatograph. The gaseous (N2 + N2O)-15N losses of the treatment with rice plants were significantly (P =0.01) higher than those of the treatment without rice plants, as were the amounts of N2O emitted. Rice plants facilitate the efflux of N2 and N2O from soil to atmosphere, as about half of the total gaseous 15N loss as N2 and N2O was found in the upper chamber. The proportion of N2O-15N to (N2 + N2O)-15N in the upper chamber was 10.56%, much higher than that of the lower chamber in treatment 1 and the headspace of treatment 2. 相似文献
995.
Measurement of coupled nitrification-denitrification in paddy fields affected by Terrazole,a nitrification inhibitor 总被引:2,自引:0,他引:2
David?CarrascoEmail author Eduardo?Fernández-Valiente Yoanna?Ariosa Antonio?Quesada 《Biology and Fertility of Soils》2004,39(3):186-192
Coupled nitrification-denitrification and potential denitrification were measured as 15N2O and 15N2 evolution rates in ammonium sulphate-treated rice soils with or without Terrazole [5-ethoxy-3 (trichloromethyl) 1,2,3 Thiadizole] under laboratory and field conditions. The greatest coupled nitrification-denitrification activity was found after drying and rewetting the soil, with maximum values of 322 ng N cm–2 h–1 in the laboratory and 90.8 ng N cm–2 h–1 in the field. These 15N2O + 15N2 evolution rates were about 10 times lower than potential denitrification in these soils. These results and the observed decrease in 15N2O + 15N2 evolution rate in soils treated with Terrazole (60% under laboratory conditions and 52% under field conditions) indicate that denitrification was limited by coupled nitrification-denitrification activity. Oxygen and previous addition of ammonium sulphate appear to control the rate of 15N2O + 15N2 evolution in ammonium sulphate-fertilised soils. 相似文献
996.
Anema SG Lee SK Lowe EK Klostermeyer H 《Journal of agricultural and food chemistry》2004,52(2):337-343
Reconstituted skim milk was adjusted to pH values between 6.5 and 7.1 and heated (90 degrees C) for up to 30 min. The skim milk samples were then readjusted to pH 6.7. Acid gels prepared from heated milk had markedly higher G ' values, a reduced gelation time, and an increased gelation pH than those prepared from unheated milk. An increased pH at heating decreased the gelation time, increased the gelation pH, and increased the final G ' of acid set gels prepared from the heated milk samples. There were only small differences in the level of whey protein denaturation in the samples at different pH values, and these differences could not account for the differences in the G ' of the acid gels. The levels of denatured whey protein associated with the casein micelles decreased and the levels of soluble denatured whey proteins increased as the pH at heating was increased. The results indicated that the soluble denatured whey proteins had a greater effect on the final G ' of the acid gels than the denatured whey proteins associated with the casein micelles. 相似文献
997.
Kim YM Park K Joo GJ Jeong EM Kim JE Rhee IK 《Journal of agricultural and food chemistry》2004,52(13):4192-4196
A gene responsible for the chlorothalonil biotransformation was cloned from the chromosomal DNA of Ochrobactrum anthropi SH35B, capable of efficiently dissipating the chlorothalonil. The gene encoding glutathione S-transferase (GST) of O. anthropi SH35B was expressed in Escherichia coli, and the GST was subsequently purified by affinity chromatography. The fungicide chlorothalonil was rapidly transformed by the GST in the presence of glutathione. LC-MS analysis supported the formation of mono-, di-, and triglutathione conjugates of chlorothalonil by the GST. The monoglutathione conjugate was observed as an intermediate in the enzymatic reaction. The triglutathione conjugate has not been previously reported and seems to be the final metabolite in the biotransformation of chlorothalonil. The glutathione-dependent biotransformation of chlorothalonil catalyzed by the bacterial GST is reported. 相似文献
998.
999.
Jeong SM Kim SY Kim DR Jo SC Nam KC Ahn DU Lee SC 《Journal of agricultural and food chemistry》2004,52(11):3389-3393
The effect of heat treatment on the antioxidant activity of extracts from Citrus unshiu peels was evaluated. Citrus peels (CP) (5 g) were placed in Pyrex Petri dishes (8.0 cm diameter) and heat-treated at 50, 100, or 150 degrees C for 10, 20, 30, 40, 50, and 60 min in an electric muffle furnace. After heat treatment, 70% ethanol extract (EE) and water extract (WE) (0.1 g/10 mL) of CP were prepared, and total phenol contents (TPC), radical scavenging activity (RSA), and reducing power of the extracts were determined. The antioxidant activities of CP extracts increased as heating temperature increased. For example, heat treatment of CP at 150 degrees C for 60 min increased the TPC, RSA, and reducing power of EE from 71.8 to 171.0 microM, from 29.64 to 64.25%, and from 0.45 to 0.82, respectively, compared to non-heat-treated control. In the case of WE from CP heat-treated at the same conditions (150 degrees C for 60 min), the TPC, RSA, and reducing power also increased from 84.4 to 204.9 microM, from 15.81 to 58.26%, and from 0.27 to 0.96, respectively. Several low molecular weight phenolic compounds such as 2,3-diacetyl-1-phenylnaphthalene, ferulic acid, p-hydroxybenzaldoxime, 5-hydroxyvaleric acid, 2,3-diacetyl-1-phenylnaphthalene, and vanillic acid were newly formed in the CP heated at 150 degrees C for 30 min. These results indicated that the antioxidant activity of CP extracts was significantly affected by heating temperature and duration of treatment on CP and that the heating process can be used as a tool for increasing the antioxidant activity of CP. 相似文献
1000.
Functional shift hypothesis and the relationship between temperature and soil carbon accumulation 总被引:1,自引:0,他引:1
Panagiotis?DaliasEmail author Giorgos?D.?Kokkoris Andreas?Y.?Troumbis 《Biology and Fertility of Soils》2003,37(2):90-95
Recent experimental evidence on the relationship between temperature and litter or soil organic matter decomposition suggests that the simple assumption that temperature affects the rate constant of the processes may not be valid. Thermal conditions seem to influence the kinetics of C mineralization by changing, in a qualitatively predictable way, the estimated percentages of initial material that behave as labile or recalcitrant. The consequences of this shift in mineralization dynamics due to temperature, referred to as the functional shift hypothesis, for the long-term C accumulation potential of a soil were investigated using a modified version of Jenny's model. It was concluded that if soils behave according to the functional shift hypothesis, then the utilization of Q10 or other temperature response functions by simulation models leads to significant overestimations of soil C losses due to temperature increase. 相似文献