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91.
Air temperature triggers the recovery of evergreen boreal forest photosynthesis in spring 总被引:11,自引:0,他引:11
Suni Tanja Frank Berninger† Timo Vesala Tiina Markkanen Pertti Hari† Annikki Mäkelä† Hannu Ilvesniemi† Heikki Hänninen‡ Eero Nikinmaa† Timo Huttula Tuomas Laurila§ Mika Aurela§ Achim Grelle¶ ers Lindroth Almut Arneth Olga Shibistova†† Jon Lloyd 《Global Change Biology》2003,9(10):1410-1426
The timing of the commencement of photosynthesis (P*) in spring is an important determinant of growing‐season length and thus of the productivity of boreal forests. Although controlled experiments have shed light on environmental mechanisms triggering release from photoinhibition after winter, quantitative research for trees growing naturally in the field is scarce. In this study, we investigated the environmental cues initiating the spring recovery of boreal coniferous forest ecosystems under field conditions. We used meteorological data and above‐canopy eddy covariance measurements of the net ecosystem CO2 exchange (NEE) from five field stations located in northern and southern Finland, northern and southern Sweden, and central Siberia. The within‐ and intersite variability for P* was large, 30–60 days. Of the different climate variables examined, air temperature emerged as the best predictor for P* in spring. We also found that ‘soil thaw’, defined as the time when near‐surface soil temperature rapidly increases above 0°C, is not a useful criterion for P*. In one case, photosynthesis commenced 1.5 months before soil temperatures increased significantly above 0°C. At most sites, we were able to determine a threshold for air‐temperature‐related variables, the exceeding of which was required for P*. A 5‐day running‐average temperature (T5) produced the best predictions, but a developmental‐stage model (S) utilizing a modified temperature sum concept also worked well. But for both T5 and S, the threshold values varied from site to site, perhaps reflecting genetic differences among the stands or climate‐induced differences in the physiological state of trees in late winter/early spring. Only at the warmest site, in southern Sweden, could we obtain no threshold values for T5 or S that could predict P* reliably. This suggests that although air temperature appears to be a good predictor for P* at high latitudes, there may be no unifying ecophysiological relationship applicable across the entire boreal zone. 相似文献
92.
93.
After drainage of natural boreal peatlands, the decomposition of organic matter increases and peat soil may turn into a net source of CO2 and N2O, whereas CH4 emission is known to decrease. Afforestation is a potential mitigation strategy to reduce greenhouse gas emission from organic agricultural soils. A static chamber technique was used to evaluate the fluxes of CH4, N2O and CO2 from three boreal organic agricultural soils in western Finland, afforested 1, 6 or 23 years before this study. The mean emissions of CH4 and N2O during the growing seasons did not correlate with the age of the tree stand. All sites were sources of N2O. The highest daily N2O emission during the growing season, measured in the oldest site, was as high as 29 mg N2O m–2d–1. In general, organic agricultural soils are sinks for methane. Here, the oldest site acted as a small sink for methane, whereas the two youngest afforested organic soils were sources for methane with maximum emission rates (up to 154 mg m–2d–1) similar to those reported for minerogenous natural peatlands. Soil respiration rates decreased with the age of the forest. The high soil respiration in the younger sites, probably resulted from the high biomass production of herbs, could create soil anaerobiosis and increase methane production. Our results show that afforestation of agricultural peat soils does not abruptly terminate the N2O emissions during the first two decades, and afforestation can even enhance methane emission for a few years. The carbon accumulation in the developing tree stand can partly compensate the carbon loss from soil. 相似文献
94.
Effects of temperature and oxygenavailability on greenhouse gas and nutrient dynamics in sediment of a eutrophic mid-boreal lake 总被引:4,自引:0,他引:4
Anu Liikanen Timo Murtoniemi Heikki Tanskanen Tero Väisänen Pertti J. Martikainen 《Biogeochemistry》2002,59(3):269-286
The effects of oxygen conditions and temperature on dynamics of greenhousegases (CH4, CO2, N2O) and nutrients(NH4
+, NO2
–+NO3
–, tot-P) were studied in sediment of hyper-eutrophic LakeKevätön, Finland. Undisturbed sediment cores were incubated at 6, 11,16, and 23 °C in a laboratory microcosm using a continuouswater flowtechnique with an oxic or anoxic water flow. The production of CO2increased with increasing temperature in both oxic (Q10 3.2 ±0.6) and anoxic (Q10 2.3 ± 0.4) flows. The release ofCH4 increased with temperature in anoxic conditions (Q102.3 ± 0.2), but was negligible with the oxic flow at all temperatures.The release of NH4
+ increased with temperature with the oxic and anoxic flows(Q10 2.4 ± 0.1). There was a net production of NO2
–, NO3
– and N2O with the oxic flow at temperatures below16 °C. The release of phosphorus was greater from the anoxicsediments and increased with temperature with both the anoxic (Q102.9 ± 0.5) and oxic (Q10 1.9 ± 0.1) flows. It isprobable that the temperature of boreal lakes and the associated oxygendeficiency will increase as the climate becomes warmer. Our experiments showedthat this change would increase the global warming potential of greenhousegasesreleased from sediments of eutrophic lakes predominately attributable to theincrease in the CH4 production. Furthermore, warming would alsoaccelerate the eutrophication of lakes by increasing release of phosphorus andmineral nitrogen from sediments, which further enhance CH4productionin sediments. 相似文献
95.
96.
Diversity and succession of the phytoplankton in a small lake over a two-year period 总被引:2,自引:2,他引:0
Pertti Eloranta 《Hydrobiologia》1993,249(1-3):25-32
Phytoplankton in the small central Finnish lake, Vasikkalampi, was studied over a two-year period by weekly sampling simultaneously with monitoring of physical and chemical properties of water, solar radiation energy and zooplankton. In the present paper, the fluctuations in phytoplankton diversity were studied in relation to environmental factors. The special aim for the study was to detect a relation between environmental disturbances and phytoplankton diversity. 相似文献
97.
Pertti J. Martikainen Marja Lehtonen Kristiina Lång Wiestse De Boer Ari Ferm 《FEMS microbiology ecology》1993,13(2):113-121
Abstract Using aerobic soil slurry technique nitrification and nitrous oxide production were studied in samples from a pine site in Western Finland. The site received atmospheric ammonium deposition of 7–33 kg N ha−1 a−1 from a mink farm. The experiments with soil slurries showed that the nitrification potential in the litter layer was higher at pH 6 than at pH 4. However, the nitrification potentials in the samples from the organic and mineral horizons at pH 6 and 4 were almost equal. Also N2 O was produced at a higher rate at pH 6 than at pH 4 in slurries of the litter layer samples. The reverse was true for samples from the organic and mineral horizons. The highest N2 O production and nitrification rates were measured in the suspensions of litter layer samples. Nitrification activity in field-moist soil samples was lower than the activity in the slurries indicating that the availability of ammonium limited nitrification in these soils. Acetylene (2.5 kPa) retarded nitrification activity (70-–100%) and N2 O production (40 – 90%) in soil slurries. Acetylene inhibited the N2 O production by 40–60% during the first 3 days after its addition to field-moist samples incubated in aerobic atmosphere. After 3 days the inhibition became much lower (4–5%). The results indicate that, in soil profiles of boreal coniferous forests receiving ammonium deposition, chemolithotrophic nitrification may have importance in the N2 O production, and that changes in soil pH affect differently nitrification as well as N2 O production in litter and deeper soil layers. 相似文献
98.
Esa Tahvanainen Henrik Forsius Margareta Damsten Elvi Karila Juha Kolehmainen Jean Weissenbach Pertti Sistonen Albert de la Chapelle 《Genomics》1995,30(3)
We recently assigned a gene for autosomal recessive cornea plana congenita (CNA2; MIM No. 217300) by linkage analysis to the approximately 3-cM interval between markers D12S82 and D12S327. Here, we extended these studies by exploiting the haplotype and linkage disequilibrium information that can be derived from the genetically isolated Finnish population and its subpopulations. By testing 32 independent families with 10 polymorphic markers in the CNA2 interval, strong allelic association between CNA2 and a set of markers with a peak at marker D12S351 was detected. Based on linkage disequilibrium analysis, the critical region for CNA2 could be narrowed to only 0.04-0.3 cM from marker D12S351, thus defining a critical interval 0.08-0.60 cM in length. These results provide a basis for highly focused positional cloning of CNA2. 相似文献
99.
Use of benthic diatom communities to evaluate water quality in rivers of southern Poland 总被引:12,自引:0,他引:12
Janina Kwandrans Pertti Eloranta Barbara Kawecka Krzysztof Wojtan 《Journal of applied phycology》1998,10(2):193-201
Biological and chemical data were processed to estimate trophic stage and degree of pollution in several streams and rivers
in southern Poland. The majority were eutrophic and some of them heavily polluted; only a few were oligo-mesotrophic. The
differences in the water quality of the rivers were reflected by different types of diatom community and also by the values
for some diatom indices, which were calculated using the latest version of the 'Omnidia' database software. Except for the
Sládeček's index, all diatom indices correlated significantly with organic load (COD), oxygen concentration, conductivity
and most of the measured ions. Some indices showed a significant negative correlation with trophic level (expressed by NH4-N and PO4-P). In general, IPS (Specific Pollution Sensitivity Index) and GDI (Generic Diatom Index) indices gave the best results.
Among the investigated diatom communities, only a few taxa indicated oligo-mesotrophy and oligo-β-mesosaprobity. Most of the
sites were characterised by a greater relative contribution of eutraphent and tolerant ones as well as α-mesosaprobic and
polysaprobic diatoms. This study suggests that the structure of benthic diatom communities and diatom indices, especially
GDI, can be applied for monitoring rivers in Poland.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
100.
Abstract. As an example of ecological gradient analysis, Gaussian response functions, with Poisson or quasi-Poisson error distribution, were fitted for diatom taxa on a pH gradient. It is possible to predict or infer the pH of lake water from the fitted curves using the method of maximum likelihood, which is easily implemented in standard non-linear regressionprograms. Due to overdis-persion with respect to the Poisson distribution, moment estimates forthe negative binomial distribution were also applied, both in estimating the species response curves and in prediction. Simulations indicated that the theoretical maximum precision (measuredby standard deviation of prediction errors) in our data set was 0.17 pH units. The observed errors were much greater (SD 0.35 to 0.43). It seems that roughly equal proportions of the excess error were caused (1) by systematic differences between the training (estimation) data and the validation (prediction) data, and (2) from a misspecified model. It is suggested that the error due to model misspecification consists of inadequacy of the presumed error distribution and of inadequacy of the simple Gaussian response function. 相似文献