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81.
森林土壤氮转化的微生物功能研究 总被引:2,自引:1,他引:1
本文研究了不同林型下土壤(A+6层和A_1层)微生物、土壤酶活性在森林土壤氮转化中的作用。结果表明不同林型下土壤具有不同的固氮作用、反硝化作用、氨化作用和硝化作用速率,即阔叶林>针阔混交林>针叶林。已经证明,固氮作用主要存在于森林土壤的A_1层,反硝化作用主要存在于A_0层。森林土壤存在2种硝化作用过程,即由自养微生物所引起的自养硝化作用过程和异养微生物所引起的异养硝化作用过程。它的存在与林型有关,某些森林土壤中这2种硝化作用过程都存在,如针阔混交林下的A_0层和A_1层。有些林型下土壤,则以异养硝化作用过程为主,如针叶林的A_0层。 相似文献
82.
The thermodynamic treatment of the disproportionation reaction of adenosine 5′-diphosphate to adenosine 5′-triphosphate and adenosine 5′-monophosphate is discussed in terms of an equilibrium model which includes the effects of the multiplicity of ionic and metal bound species and the presence of long range electrostatic and short range repulsive interactions. Calculated quantities include equilibrium constants, enthalpies, heat capacities, entropies, and the stoichiometry of the overall reaction. The matter of how these calculations can be made self-consistent with respect to both calculated values of the ionic strength and the molality of the free magnesium ion is discussed. The thermodynamic data involving proton and magnesium-ion binding data for the nucleotides involved in this reaction have been evaluated. 相似文献
83.
A study was made of soil samples collected during an expedition to the Highlands of Papua New Guinea. Fungi were isolated from the samples by the method of hair baiting (To-Ka-Va). Of the 33 species isolated, about half showed keratinolytic activity. Such activity is previously unreported for Mucor hiemalis f. hiemalis, Myrothecium roridum, Paecilomyces carneus, P. marquandii, Penicillium brevicompactum, Rhinocladiella mansonii and Verticillium lecanii. The species most active keratinolytically were Chrysosporium an. Arthroderma cuniculi, C. an. A. curreyi, C. indicum, Myceliophthora vellerea and Trichophyton ajelloi. The spectrum of fungi with keratinolytic activity isolated from the different sites differed considerably according to the frequency of use by man, heaviest use being correlated with greatest activity. The pH of the soil (varying from 5.8–7.5) had little influence on the type of such fungi isolated. 相似文献
84.
Analysis of bacterial populations in a grassland soil according to rates of development on solid media 总被引:3,自引:0,他引:3
Abstract The process of colony formation by bacteria from grassland soil sampled in April, July and September was simulated by a colony-forming curve (CFC). The CFC was a super-imposition of several component curves (cCFC) given theoretically by the first order reaction (FOR) model [3,6]. The pattern of FOR model curves was not influenced by the time of sampling and four cCFCs were always recognized during an incubation period of 160 h. It was considered that the CFC describes an inherent property of the bacterial population of the field. Bacterial isolates were obtained from colonies produced in each of four cCFCs on agar plates. Isolates corresponding to one cCFC were classified as one group. The bacterial isolates were characterized by morphological and physiological tests and subsequently clustered. Few oligotrophic bacteria were obtained among bacteria which produced visible colonies within 63 h of incubation time. On the other hand, approx. 50% of bacteria which produced v colonies after 63 h were oligotrophic bacteria. The time required for the appearance of the first colony, t r of the FOR model, was very similar in the isolates belonging to one group. A close linear relationship was observed between t r value and doubling time of isolates. 相似文献
85.
V. P. Shabaev 《Plant and Soil》1986,91(2):249-256
Summary Fertilizer/soil N balance of cropped and fallow soil has been studied in a pot experiment carried out with grey forest soil (southern part of Moscow region) at increasing rates of15N labelled ammonium sulfate (0; 8; 16; 32 mg N/100 g of soil). The fertilizer15N balance has been shown to depend upon its application rate and the presence of growing plants. Fertilizer N uptake efficiency was maximum (72.5%) and gaseous losses-minimum (12.5%) at the application rate of 16 mg N/100 g of soil. Fertilizer N losses from the fallow soil were 130–220% versus those from the cropped soil. At the application of fertilizer N the plant uptake of soil N was 170–240% and the amount of soil N as N–NH4 exchangeable + N–NO3 in fallow was 350–440% as compared to the control treatment without nitrogen (PK).After cropping without or with N fertilizer application at the rates of 8 and 32 mg N/100 g of soil, a positive nitrogen balance has been found which is likely due to nonsymbiotic (associative) N-fixation. It has been shown that biologically fixed nitrogen contributes to plant nutrition. 相似文献
86.
Summary The N-metabolism ofArthrocnemum fruticosum (L.) Moq., growing in a saline area north-east of the Dead Sea in Jordan, was studied over its vegetative growth period from
March to September 1981. Plant and soil samples were taken at monthly intervals. Water content, Na+, K+, Cl−, NH
4
+
, NO
2
−
and NO
3
−
concentrations were determined in the soil extracts, and the same determinations plus ash weight, soluble carbohydrates,
proline, proteins andin vivo nitrate reductase in the plant roots and shoots.
Soil humidity decreased and salinity increased from March to August, with re-wetting occurring in late July. K+ and Cl− were much lower in the soils than Na+. Plant relative dry weight increased during summer due to the absorption of Na+ in addition to increased organic dry weight. The uptake of Na+ was not balanced by a similar uptake of Cl−.
Ammonium and nitrate decreased in soil and plants in parallel with increasing salinity. Nitrite was only found in the roots
and always in very low quantities. Proline was found only in March. The total soluble carbohydrates in the roots showed a
short increase in June when the sodium in the plants also increased. It was concluded that carbohydrates may be used to balance
osmotic shocks, but that another compatible compounds is necessary to maintatin long-term osmotic equilibrium.
The nitrate reductase activity, measuredin vivo, and the soluble protein changed roughly in parallel with the internal nitrate from May to August, suggesting that nitrogen
uptake and reduction in the plant is inhibited during summer when the soil is dry and very saline. This could be a direct
effect of drought and/or salinity on the plants, or an indirect onevia an inhibition of nitrifying bacteria. 相似文献
87.
Summary In order to improve nitrogen recovery by rice, the effect of a urease inhibitor phenylphosphorodiamidate (PPD) on the efficiency
of fertilizer urea was studied in laboratory and greenhouse. Addition of PPD to urea (5% w/w) delayed urea hydrolysis by 3
to 4 days and reduced ammonia volatilization from 45% (without PPD) to 8.5% (with PPD). Ammonia volatilization obeyed first
order kinetics. Urea hydrolysis was sufficiently strongly inhibited to match the nitrification potential of the soil. N application
to rice by three different modes showed that a delayed mode (4 splits) was superior to two conventional modes (3 splits) in
nitrogen recovery and fertilizer efficiency since it met nitrogen requirement of plants at reproductive stage. In 2 out of
3 modes of application, there was a 14% increase (relative) in grain yields and dry matter, and 6.8% increase in N uptake
efficiency on application of PPD along with urea. The results indicate that urease inhibitors like PPD can be effectively
used to block urea hydrolysis, reduce ammonia volatilization losses and improve N use efficiency by rice. 相似文献
88.
A canonical variate analysis was used to summarize the distribution pattern of 30 species of dung beetles (Scarabaeinae) from 162 sites in the Iberian peninsula (Spain and Portugal) in relation to 4 site variables. The best separation of beetle
species, obtained using a xerothermic climatic index, was into 3 groups called “mediterranean”, “unrestricted” and “temperate”.
Little further separation was achieved using altitude, dung type or soil type. These data are used to select dung beetles
for introduction to south-western Australia for bush fly control.
Résumé On a fait appel à l'analyse de variables canoniques pour résumer le plan de distribution, relatif à 4 variables de localité, de 30 espèces de bousiers (Scarabaeinae) de 162 localités de la Péninsule ibérique (l'Espagne et le Portugal). La meilleure division des espèces, obtenue à l'aide d'un indice xérothermique climatique, se faisait en 3 groupes désignés respectivement comme “méditerranéen”, “ubiquiste” et “tempéré”. Peu de séparation supplémentaire a été obtenue en ayant recours à des facteurs d'altitude, de nature de la bouse ou de type de sol. Ces données ont été employées pour aider à la sélection de bousiers destinés à être introduits en Australie Occidentale pour y combattreMusca vetustissima Walker[Diptera].相似文献
89.
Maximal exercise capacity in adolescent European and Amerindian high-altitude natives 总被引:1,自引:0,他引:1
L P Greksa H Spielvogel L Paredes-Fernández 《American journal of physical anthropology》1985,67(3):209-216
Forty-seven highland natives were given maximal exercise tests on a treadmill ergometer at 3,600 m. The subjects were grouped into four subsamples on the basis of ethnicity (European vs. Aymara) and age (young vs. old adolescent). Two-way ANOVA indicated that VO2max adjusted for body size did not differ significantly between ethnic groups but was significantly larger in older than younger boys within each ethnic group (p less than .05). This finding does not support the hypothesis that Amerindian highland natives have adapted genetically to hypoxia but is consistent with the hypothesis that the relatively high VO2max's of highlanders are acquired by developmental adaptation. Several measures of ventilation and oxygen transport capacity differed significantly between ethnic groups, suggesting that growing European and Aymara boys may respond somewhat differently to the stress of high-altitude hypoxia. However, despite these differences, VO2max, an integrated measure of the overall functional capacity of the oxygen transport system, did not differ significantly between ethnic groups, suggesting that both groups are equally capable of meeting the body's oxygen requirements during maximal exercise at high altitude. 相似文献
90.
PLANT GROWTH RESPONSES TO VESICULAR-ARBUSCULAR MYCORRHIZA 总被引:6,自引:4,他引:2