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81.
The effect of fire on nutrient losses and cycling in aQuercus coccifera garrigue (southern France) 总被引:1,自引:0,他引:1
Louis Trabaud 《Oecologia》1994,99(3-4):379-386
The effects of burning on plant nutrient budgets and rates of carbonic gas and particulate matter emission during fires were evaluated in aQuercus coccifera (garrigue) shrubland. Nutrient levels were determined in field-collected pre-fire vegetation and combustion residues. The losses (increased elemental transfer) were calculated as the difference between the quantity of an element in the fuel (combustible standing vegetation plus litter) before burning and that present in the postfire residues (ash). Weight losses of elements are correlated with weight losses of burnt plant biomass. The relative order of nutrient losses was: N>C>Na>Ca>P>K>Mg. Estimated losses of N, C and P from combustible plant matter exceeded 98, 97 and 79% respectively. Copious N, C and P volatilization during burning was promoted by high concentrations of these elements in foliage and fine woody biomass of the aboveground vegetation and leaf litter of the garrigue. Elements were principally removed in the smoke. The quantities of gaseous emissions of CO2, CO and particulate matter produced were estimated. 相似文献
82.
Carbon allocation in developing spruce needles. Enzymes and intermediates of sucrose metabolism 总被引:2,自引:0,他引:2
Rüdiger Hampp Bernd Egger Susanne Effenberger Werner Einig 《Physiologia plantarum》1994,90(2):299-306
In lyophilized needles of Norway spruce ( Picea abies [L.] Karsten) and starting from bud break, we determined enzyme activities (sucrose phosphate synthase [SPS; EC 2.4,1.14]. sucrose synthase [SS; EC 2.4,1.13]. acid invertase [AI; EC 3.2,1.26]) and intermediates (starch, sucrose, glucose, fructose; fructose 6-phosphate, fructose 2.6-bisphosphate [F26BP]) of carbohydrate metabolism together with needle weight, shoot length, chlorophyll and protein. For up to 110 days after bud break, samples were taken twice a week from about 25-year-old trees under field conditions. At least three periods can be distinguished during needle maturation. During the first period (up to 45 days after bud break) Al showed the highest extractable activity. This coincided with very high levels of F26BP (up to 11 pmol [mg dry weight]−1 ) and a transient increase of starch in parallel to a decrease of sucrose. The interval between 45 and 70 days after bud break was characterized by high SS activity (ratio of fructose/glucose >1), much decreased levels of F26BP (down to below 1 pmol [mg dry weight]−1 ), and a pronounced increase in the dry weight/fresh weight ratio. In parallel, starch declined and soluble carbohydrates increased. Finally, needle maturation was characterized by decreasing SS and continuously increasing SPS activities, so that the ratio of SPS/SS increased more than 6-fold. AI. however, did not decline with maturation. Changes in pool sizes of metabolites and enzyme activities (AI. SPS) are consistent with current concepts on sink/source transition. SS is obviously important with regard to the synthesis of structural polysaccharides. 相似文献
83.
A simple model was developed to estimate the contribution of nitrogen (N) mineralization to the N supply of crops. In this model the soil organic matter is divided into active and passive pools. Annual soil mineralization of N is derived from the active pool. The active pool comprises stabilized and labile soil organic N. The stabilized N is built up from accumulated inputs of fresh organic N during a crop rotation but the labile N is a fraction of total N added, which mineralizes faster than the stabilized N. The passive pool is considered to have no participation in the mineralization process. Mineralization rates of labile and stabilized soil organic N from different crop residues decomposing in soil were derived from the literature and were described by the first-order rate equation dN/dt =-K*N, where N is the mineralizable organic N from crop residues andK is a constant. The data were groupedK
1 by short-term (0–1 year) andK
2 by long-term (0–10 years) incubation. Because the range of variation inK
2 was smaller than inK
1 we felt justified in using an average value to derive N mineralization from the stabilized pool. The use of a constant rate ofK
1 was avoided so net N mineralization during the first year after addition is derived directly from the labile N in the crop residues. The model was applied to four Chilean agro-ecosystems, using daily averages of soil temperature and moisture. The N losses by leaching were also calculated. The N mineralization varied between 30 and 130 kg N ha–1 yr–1 depending on organic N inputs. Nitrogen losses by leaching in a poorly structured soil were estimated to be about 10% of total N mineralized. The model could explain the large differences in N- mineralization as measured by the potential N mineralization at the four sites studied. However, when grassland was present in the crop rotation, the model underestimated the results obtained from potential mineralization. 相似文献
84.
Growth rate, plant development and water relations of the ABA-deficient tomato mutant sitiens 总被引:2,自引:0,他引:2
Given the close relationship between a plant's growth rate and its pattern of biomass allocation and the effects of abscisic acid (ABA) on biomass allocation, we studied the influence of ABA on biomass allocation and growth rate of wildtype tomato ( Lycopersicon esculentum Mill. cv. Moneymaker) plants and their strongly ABA-deficient mutant sitiens. The relative growth rate of sitiens was 22% lower than that of the wildtype, as the result of a decreased specific leaf area. The net assimilation rate and the leaf weight ratio were not affected. The mutant showed a much higher transpiration rate and lower hydraulic conductance of the roots. These two factors resulted in sitiens having a significantly lower leaf water potential and turgor. resulting in reduced leaf expansion and, consequently, a lower specific leaf area relative to the wildtype. Addition of ABA to the sitiens roots resulted in phenotypic reversion to the wildtype. We conclude that the influence of ABA-deficiency on biomass allocation and relative growth rate is the result of altered water relations in the plants, rather than of a direct effect on sink strength of different plant organs. 相似文献
85.
The duckweed Lemna gibba required light and a suitable energy source such as sucrose, glucose or fructose, for maximum growth in culture. The requirement
for light was relatively unimportant and the plants grew well in a photon flux density of only 52 μmol m-2s-1 PAR. The uptake and incorporation of uniformly labelled 14C-glucose into fronds was related only to the concentration of the sugar.
When incubated with soil, labelled L. gibba behaved in a manner similar to that of labelled ryegrass roots which had been produced by a more elaborate technique using
a 14CO2 labelled atmosphere. During incubation with soil for 224 days the L. gibba material (specific activity 6133 Bq mg-1 d. wt) lost 64% of its radioactivity as 14CO2 and ryegrass (specific activity 6634 Bq mg-1 d. wt) lost 49%. Alkaline extracted humic and fulvic acids from soil had specific activities for the L. gibba incubation of 3409 and 407 Bq mg-1 solid and for ryegrass roots of 4609 and 546 Bq mg-1 solid respectively. The production of 13C or 14C-labelled L. gibba can be undertaken using only simple equipment producing material the specific radioactivity of which can be controlled by
adjusting the activity of the sugar energy source. 相似文献
86.
B. S. Griffiths 《Plant and Soil》1994,164(1):25-33
Food web studies from a range of ecosystems have demonstrated that the fauna contributes about 30% of total net nitrogen mineralization.
This results mainly from the activities of microbial-feeding microfauna (nematodes and protozoa). Microbial and microfaunal
activity is concentrated at spatially discrete and heterogeneously distributed organic substrates, including the rhizosphere.
The dynamics of microfauna and their effect on nutrient cycling and microbial processes at these sites is reviewed. The potential
manipulation of microfauna, either as an experimental tool to further understand soil microbial ecology or as a practical
means of managing nutrient flows in agroecosystems, is discussed. 相似文献
87.
Nutrient distribution in a Swedish tree species experiment 总被引:2,自引:0,他引:2
The influence of four tree species on the distribution of nutrients between different compartments of the ecosystem was examined.
In a randomized block (n=3) experiment in south-western Sweden, Ca, Mg and K were determined as exchangeable amounts in the
mineral soil and as total amounts in the O+A1 horizons (topsoil) and in the aboveground tree biomass. N contents were determined in all compartments as well as P contents
of the aboveground tree biomass and the topsoil. The four tree species planted were: silver fir [Abies alba Mill.] (AA), grand fir [Abies grandis Lindl.] (AG), Norway spruce [Picea abies L. Karst.] (PA) and Japanese larch [Larix leptolepis (Sieb. och Zucc.) Endl.] (LL). At the age of 35–36 years, the total stemwood production of the most productive species, AG,
was estimated at 471 m3 ha−1. In relation to AG, LL had produced 80%, PA 73% and AA 37%.
The system totals [aboveground tree biomass total + topsoil total + exchangeable (Ca, Mg, K) or total (N) in the mineral soil]
of Ca, K and N did not differ significantly at the 5% level between the investigated species. For Mg, the system total in
LL was significantly higher than for the other species.
There was an indication that LL and AA contained higher amounts of Ca, Mg, K and N in the topsoil but less in the biomass
than did AG and PA (partly significant). In the mineral soil, there were no significant differences in the exchangeable pools
of Ca and K, nor in the total amounts of N.
The biomass nutrient concentrations generally decreased in the order: AA > PA > AG > LL. At stem or whole-tree harvest, the
Ca export per biomass unit would more than double in the case of PA compared to LL. LL also contained less N in the biomass
than the other species. However, the N content in the biomass did not differ between the most (AG) and the least (AA) productive
species, although the production of dry weight biomass (standing + harvested) of AG had been twice that of AA. It is concluded
that the nutrient budget of a managed forest may vary considerably depending on the choice of tree species. 相似文献
88.
Size and sex allocation in monoecious woody plants 总被引:2,自引:0,他引:2
John F. Fox 《Oecologia》1993,94(1):110-113
The female size advantage hypothesis predicts that the allocation ratio of female: male reproductive effort should increase with plant size (total reproductive effort). A male height advantage hypothesis has also been proposed, based on the supposed greater advantage of height to male reproductive success in wind-pollinated plants. These ideas were tested with data for wind-pollinated, monoecious trees and shrubs which exhibit a suitably large range of sizes. Number of male inflorescences increased faster with size than did number of female inflorescences in 2 of 9 species; in the remaining 7 species there was no significant difference. The male:female ratio of inflorescence numbers increased with height in 4 of 7 species and did not change significantly in the remaining 3 species, as shown by regression. Height and size are highly correlated and so their effects could not be distinguished. The fact that many conifers place the female cones uppermost in the crown suggests that size and not height favors increased allocation to male function, as does well-established theory connecting the existence of male versus female size advantage to pollen and seed dispersal chacteristics. Regression analysis of the relation between male and female reproductive effort should be done by reduced major axis regression; ordinary least squares regression underestimates slopes; in this study opposite conclusions could be drawn from ordinary least squares and reduced major axis regressions. 相似文献
89.
Pot experiments were conducted with a calcareous soil (Inceptisol) to elucidate the effects of bicarbonate (0 and 20 mM) and root zone temperature (15° and 25°C) on the uptake of Zn, Fe, Mn and Cu by "Zn-efficient" and "Zn-inefficient" rice cultivars. Bicarbonate decreased concentrations and total uptake of Zn in shoots of "Zn-inefficient" cultivars, especially of IR 26 at 25°C, but not in Zn-efficient cultivars. Bicarbonate decreased concentrations and uptake of Fe in shoots of Zn inefficient cultivars, particularly in IR 26. Concentrations and total uptake of Mn were lower in bicarbonate treatment in the Zn-inefficient cultivars at 15°C, and in all cultivars at 25°C. However, concentration and uptake of Cu were not affected by bicarbonate in all cultivars. Compared to the 25°C root zone temperature, the concentrations and total uptake of both Zn and Cu in shoots at 15°C were lower in Zn-inefficient than in the Zn-efficient cultivars. The results indicate that Zn-efficiency in rice is causally related to high tolerance of plant to elavated bicarbonate concentrations in soil solution. 相似文献
90.
Estimating regional carbon stocks and spatially covarying edaphic factors using soil maps at three scales 总被引:2,自引:1,他引:1
Most estimates of regional and global soil carbon stocks are based on extrapolations of mean soil C contents for broad categories
of soil or vegetation types. Uncertainties exist in both the estimates of mean soil C contents and the area over which each
mean should be extrapolated. Geographic information systems now permit spatially referenced estimates of soil C at finer scales
of resolution than were previously practical. We compared estimates of total soil C stocks of the state of Maine using three
methods: (1) multiplying the area of the state by published means of soil C for temperate forests and for Spodosols; (2) calculating
areas of inclusions of soil taxa in the 1:5,000,000 FAO/UNESCO Soils Map of the World and multiplying those areas by selected
mean carbon contents; and (3) calculating soil C for each soil series and map unit in the 1:250,000 State Soil Geographic
Data Base (STATSGO) and summing these estimates for the entire state. The STATSGO estimate of total soil C was between 23%
and 49% higher than the common coarse scale extrapolations, primarily because STATSGO included data on Histosols, which cover
less than 5% of the area of the state, but which constitute over one-third of the soil C. Spodosols cover about 65% of the
state, but contribute less than 39% of the soil C. Estimates of total soil C in Maine based on the FAO map agreed within 8%
of the STATSGO estimate for one possible matching of FAO soil taxa with data on soil C, but another plausible matching overestimated
soil C stocks. We also compared estimates from the 1:250,000 STATSGO database and from the 1:20,000 Soil Survey Geographic
Data Base (SSURGO) for a 7.5 minute quadrangle within the state. SSURGO indicated 13% less total soil C than did STATSGO,
largely because the attribute data on depths of soil horizons in SSURGO are more specific for this locality. Despite localized
differences, the STATSGO database offers promise of scaling up county soil survey data to regional scales because it includes
attribute data and estimates of areal coverage of C-rich inclusions within map units. The spatially referenced data also permit
examination of covariation of soil C stocks with soil properties thought to affect stabilization of soil C. Clay content was
a poor predictor of soil C in Maine, but drainage class covaried significantly with soil C across the state. 相似文献