Radial distribution of sap flux density in trunks of a mature beech stand     

Dietmar Lüttschwager  Rainer Remus 《Annals of Forest Science》2007,64(4):431-438

In a mature beech stand located in north-eastern Germany, xylem sap flux measurements were continuously performed during the 2002–2004 growing seasons. Ten representative trunks were studied using heated thermal dissipation probes. The measurements aimed at identifying principles governing radial profiles of xylem flux in beech trunks. The measurements were taken up to a trunk depth of 132 mm. The sap flow density in the pericambial xylem was found to vary among trees of different diameters, but was not considerably smaller in suppressed trees. A model for the radial distribution of sap flux density was formulated relating trunk radius and sap flow density. The model takes into account different trunk diameter. About 90% of the sap flux was found to occur in the outer two fifths of the trunk. Using this model, an adequate estimate of transpiration can be achieved at tree and stand level, even when the sap flux measurements are restricted to the outer trunk sectors.  相似文献   

Initiale Bodenentwicklung in aufgespültem Löß und Hafenschlick     

Dietmar Schrder 《植物养料与土壤学杂志》1988,151(1):3-8

Initial soil development in loess and harbourbasin mud reclaimed by slurry poldering In the Rhenish Brown Coal Strip Mining Area initial soil development was investigated for 6–15 and 15–25 years old loamy-silty loess soils reclaimed by slurry poldering. In the Emden environs the same analyses were applied to 6, 17, and 28 years old silty-clayey harbour-mud soils, also reclaimed by slurry application. The most prominent results when comparing these two types of soil are as follows: The mud soils show higher contents of clay and organic matter. Therefore they reveal more favourable characteristics concerning cation-exchange capacity, soil physical and soil biological properties in comparison to those of the loess soils. In both types of soils cation-exchange-capacity and soil biological activity increase in the Ap-horizon over time. The soil physical characteristics of the mud soils markedly improve in the run of the development, whereas those of the loess soils hardly improve. It remains a subject of discussion, since what stage of development mud soils should be classified as sea-marshes/“Kleimarschen” and loess soils as rendzinas.  相似文献   

Vulnerability of Bavarian silty loam soil to compaction under heavy wheel traffic: impacts of tillage method and soil water content     

H. Gülü Yavuzcan  Dietmar Matthies  Hermann Auernhammer 《Soil & Tillage Research》2005,84(2):200-215

Soil compaction caused by traffic of heavy vehicles and machinery has become a problem of world-wide concern. The aims of this study were to evaluate and compare the changes in bulk density, soil strength, porosity, saturated hydraulic conductivity and air permeability during sugar beet (Beta vulgaris L.) harvesting on a typical Bavarian soil (Regosol) as well as to assess the most appropriate variable factors that fit with the effective controlling of subsequent compaction. The field experiments, measurements and laboratory testing were carried out in Freising, Germany. Two tillage systems (conventional plough tillage and reduced chisel tillage) were used in the experiments. The soil water contents were adjusted to 0.17 g g⁻¹ (w₁), 0.27 g g⁻¹ (w₂) and 0.35 g g⁻¹ (w₃).Taking the increase in bulk density, the decrease in air permeability and reduction of wide coarse pore size porosity (−6 kPa) into account, it seems that CT (ploughing to a depth of 0.25 m followed by two passes of rotary harrow to a depth 0.05 m) of plots were compacted to a depth of at least 0.25 m and at most 0.40 m in high soil water (w₃) conditions. The trends were similar for “CT w₁” (low soil water content) plots. However, it seems that “CT w₁” plots were less affected than “CT w₃” plots with regard to bulk density increases under partial load. In contrast, diminishments of wide coarse pores (−6 kPa) and narrow (tight) coarse pores (−30 kPa) were significantly higher in “CT w₁” plots down to 0.4 m. Among CT plots, the best physical properties were obtained at medium soil water (w₂) content. No significant increase in bulk density and no significant decrease in coarse pore size porosity and total porosity below 0.2 m were observed at medium soil water content. The soil water content seemed to be the most decisive factor.It is likely that, CS (chiselling to a depth of 0.13 m followed by two passes of rotary harrow to a depth 0.05 m) plots were less affected by traffic treatments than CT plots. Considering the proportion of coarse pore size porosity (structural porosity) and total porosity, no compaction effects below 0.3 m were found. Medium soil water content (w₂) provides better soil conditions after traffic with regard to wide coarse pore size porosity (−6 kPa), air permeability (at 6 and 30 kPa water suction), total porosity and bulk density. Proportion of wide coarse pores, air permeability and bulk density seems to be suitable parameters to detect soil compaction under the conditions tested.  相似文献   

Avoidance test with<Emphasis Type="Italic">Eisenia fetida</Emphasis> as indicator for the habitat function of soils: Results of a laboratory comparison test     

Kerstin?Hund-RinkeEmail author  Rudolf?Achazi  J?rg?R?mbke  Dietmar?Warnecke 《Journal of Soils and Sediments》2003,3(1):7-12

Intention, Goal, Scope, Background. The habitat function of soils is often assessed using the reproduction test withEisenia fetida. As this test is rather labour-intensive, an alternative is needed which is less cost-intensive in terms of duration and workload, but gives reasonable results. The avoidance test withE. fetida is a suitable screening test meeting these criteria. However, before a novel test system can be generally recommended it has to be ensured that comparable results are acquired from different laboratories on the basis of the respective test guideline.  相似文献   

Mineralselektive K-Freisetzung aus Böden mit Oktodecylammonium-Ionen (nc = 18)     

Ernst A. Niederbudde  Ernst Raugh  Dietmar Schrder 《植物养料与土壤学杂志》1988,151(4):255-260

Mineral-selective K release from soils by octodecylammonium- ions (n_c = 18) n_c18-releasable potassium was determined on soils of five different areas. n_c18-releasable K is the potassium which is displaced by octodecylammonium ions (ODA). Because the main sources of this potassium are trioctahedral micas, it is called briefly biotite-K. The investigated soils are from different areas in Bavaria (loess and clay stone derived soils, alluvial soils); partly the locations are K fertilizer trials. Soils of known age are locations from the Niederrhein terraces (Holocene soils). In the 0.2–2 μm (coarse clay) and 2–6 μm (fine silt) fractions the biotite-K content lies between 12 and 40% of total K. At given fractionation the highest amounts of K were released from the coarse clay of the soils. In the loess soils rich in silt the biotite-K pool in the medium and coarse silt fractions was also considerable. Clay soils showing poor K supplying power (K fertilizer trials) in the field are characterized by very low biotite-K quantities in all silt fractions. In the Holocene soils the age of which varies between 4 000 and 8 000 years the ODA releaseable values are greater than in the loess soils. In all fractions of the young Holocene soils the released K is greater than in the same fractions of the old Holocene soils. Calculated to a soil depth of 60 cm the K release in kg/ha reaches from 25 000 (young soil form) to 17 000 (old soil form).  相似文献   

家禽育种的未来25年     

李政萍  申瓴 《国外畜牧学(猪与禽)》2010,30(1):53-55

几十年来,家禽育种一直是提高禽蛋和禽肉生产效率(以较低的生产成本获得较高的产量)的一种永恒的手段。已经达到了家禽遗传潜力的极限呢,还是在未来的25年中仍有可能提高遗传进展?一位遗传学家通过本文对2034年家禽行业的状况提出了他的看法。  相似文献   

Amphiregulin, a TH2 cytokine enhancing resistance to nematodes     

Zaiss DM  Yang L  Shah PR  Kobie JJ  Urban JF  Mosmann TR 《Science (New York, N.Y.)》2006,314(5806):1746

Although type 2 immune responses contribute to allergy and asthma, these responses are essential for clearing intestinal helminth infestations by mechanisms that include increased epithelial shedding. We show that T helper 2 cells (T(H)2), but not other T cell subsets, express amphiregulin, a member of the epidermal growth factor (EGF) family. EGF receptor ligands directly induce epithelial cell proliferation, and lack of amphiregulin delayed expulsion of the nematode Trichuris muris. This newly recognized link between T(H)2 cells and epithelial proliferation should help in planning therapeutic interventions for helminth infections and other diseases that involve both cell proliferation and allergy, such as asthma.  相似文献   

Comparison between discontinuous and continuous lactose conversion processes for the production of prebiotic galacto-oligosaccharides using beta-galactosidase from Lactobacillus reuteri     

Splechtna B  Nguyen TH  Haltrich D 《Journal of agricultural and food chemistry》2007,55(16):6772-6777

Galacto-oligosaccharide (GOS) formation from lactose in discontinuous and continuous modes of conversion was investigated using beta-galactosidase (beta-gal) from Lactobacillus reuteri. A continuous stirred tank reactor (CSTR) with an external crossflow membrane was set up, and continuous GOS production was analyzed and compared to the batchwise formed GOS product. Marked differences were detected for the two reactor setups. Above 65% lactose conversion, the GOS yield was lower for the CSTR due to a lower content of tri- and tetrasaccharides in the reaction mixture. In the CSTR, beta-gal from L. reuteri showed up to 2-fold higher specificity toward the formation of beta-(1-->6)-linked GOS, with beta-D-Galp-(1-->6)-D-Glc and beta-D-Galp-(1-->6)-D-Gal being the main GOS components formed under these conditions. This could be used to synthesize more defined GOS products.  相似文献   

Compaction of forest soils with heavy logging machinery affects soil bacterial community structure     

Beat Frey  Johann Kremer  Andreas Rüdt  Stephane Sciacca  Dietmar Matthies  Peter Lüscher 《European Journal of Soil Biology》2009,45(4):312-320

Soil compaction is widespread but tends to be most prevalent where heavy machinery is used in landfill sites, agriculture and forestry. Three forest sites strongly disturbed by heavy logging machinery were chosen to test the physical effects of different levels of compaction on soil bacterial community structure and soil functions. Community analysis comprised microbial biomass C and T-RFLP genetic profiling. Machine passes, irrespective of the compaction level, considerably modified soil structural characteristics at two soil depths (5–10 cm; 15–20 cm). Total porosity decreased up to 17% in the severe compaction. Reflected in this overall decline were large decreases in macroporosity (>50 μm). Reduction in macroporosity was associated with higher water retention and restricted gas exchange in compacted soils. The strongest effect was observed in the severely compacted wheel tracks where air and water conductivities were reduced permanently to 10% or even lower of the original conductivities of undisturbed soils. Very slow drainage in combination with a dramatically reduced gas permeability led to unfavorable soil conditions in severely disturbed traffic lanes reflecting the changes in the total bacterial community structures at both soil depths. Additionally, microbial biomass C tended to be lower in compacted soil. Our results indicate that the type of severe treatments imposed at these forest sites may have strong adverse effects on long-term soil sustainability.  相似文献   

Correction: Erhebungen zur Anwendung von chemischen Pflanzenschutzmitteln in Zuckerrüben     

Dietmar Roßberg  Nelia Aeckerle  Nicol Stockfisch 《Gesunde Pflanzen》2018,70(1):55-55

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