The native South American crayfishes (Crustacea,Parastacidae): state of knowledge and conservation status

相似文献   

Effects of poultry manure amendment on phosphorus uptake by ryegrass,soil phosphorus fractions and phosphatase activity

Poultry manure (PM) contains a large proportion of phosphorus (P) in mineral-associated forms that may not be readily available for plant uptake. In addition, PM application influences both chemical and biotic processes, and can affect the lability of native soil P. To investigate the effects of PM on soil P availability, we grew ryegrass (Lolium perenne) in greenhouse pots amended with poultry manure. Biomass was harvested at 4, 8, and 16 weeks following PM application, with soil separated into rhizosphere and bulk fractions. Soil was sequentially extracted by H₂O, 0.5 M NaHCO₃, 0.1 M NaOH, and 1 M HCl, and inorganic P (P_i) and enzymatically hydrolyzable organic P (P_oe) were quantitated. Root P concentrations were 37% higher and total P uptake 59% higher with PM application than Control. At week 16, there was 30% more labile-P_i (H₂O- plus NaHCO₃-P_i) in the rhizosphere with PM than in Control. Phosphodiesterase activity increased with PM application. Furthermore, acid phosphomonoesterase, alkaline phosphomonoesterase, and phosphodiesterase activities were all higher in the rhizosphere than in bulk soil at week 16 with PM, indicating that increased labile-P_i was due primarily to stimulation of soil phosphatases to mineralize NaOH-P_oe. Soil pH increased with PM application and plant growth, and may have promoted P availability by decreasing sorption of Al- and Fe-associated inorganic and organic phosphates. These results demonstrate that whereas PM application may initially increase NaOH and HCl-P_i, these fractions can be readily changed into labile-P and do not necessarily accumulate as stable or recalcitrant P in soil.     

A 13C tracer study to identify the origin of dissolved organic carbon in forested mineral soils

The relative contributions of sources of carbon in soils, such as throughfall, litter, roots, microbial decay products and stable organic fractions, to dissolved organic C are controversial. To identify the origin of dissolved organic C, we made use of a 4‐year experiment where spruce and beech, growing on an acidic loam and on a calcareous sand, were exposed to increased CO₂ that was depleted in ¹³C. We traced the new C inputs from trees into dissolved organic C, into water‐extractable organic C, and into several particle‐size fractions. In addition, we incubated the labelled soils for 1 year and measured the production of dissolved organic C and CO₂ from new and old soil C. In the soil solutions of the topsoil, the dissolved organic C contained only 5–10% new C from the trees. The δ¹³C values of dissolved organic C resembled those of C pools smaller than 50 µm, which strongly suggests that the major source of dissolved organic C was humified old C. Apparently, throughfall, fresh litter and roots made only minor contributions to dissolved organic C. Water‐extractable organic C contained significantly larger fractions of new C than did the natural dissolved organic C (25–30%). The δ¹³C values of the water‐extractable organic C were closely correlated with those of sand fractions, which consisted of little decomposed organic carbon. The different origin of dissolved and water‐extractable organic C was also reflected in a significantly larger molar UV absorptivity and a smaller natural ¹³C abundance of dissolved organic C. This implies that the sampling method strongly influences the characteristics and sources of dissolved organic C. Incubation of soils showed that new soil C was preferentially respired as CO₂ and only a small fraction of new C was leached as dissolved organic C. Our results suggest that dissolved organic C is produced during incomplete decomposition of recalcitrant native C in the soils, whereas easily degradable new components are rapidly consumed by microbes and thus make only a minor contribution to the dissolved C fraction.     

Use of multipurpose trees in hill farming systems in Western Nepal

A large number of multipurpose trees and shrubs are deliberately retained or incorporated on farms in the subsistence farming systems on the steep slopes in parts of Nepal. Woody perennials are maintained in contour strips across the slopes and around the fields. The contribution of these trees is the production of foder and firewood and their protective function in reducing the erosion hazards and thereby making crop production possible in those steep slopes where profitable cropping would otherwise be extremely difficult. Based on a case study in two villages of the Western Development Region, this paper presents some data on basic farm management aspects, production of crops and other components, etc. of the system. The performance of the system is assessed and its merits and weakness highlighted.Although the hill farming system extends over quite a large area and accounts for a large number of Nepal's population, it has not received any research attention nor benefitted by any scientific innovations. Improvement possibilities in terms of component technologies as well as farming systems including the incorporation of the several locally available medicinal plants are indicated.     

Gattungsgrenzen bei höheren Discomyceten

Zusammenfassung An Hand besonderer Discomyceten-Funde aus dem Jahre 1961 werden einige Nachbargattungen miteinander verglichen und ihre gegenseitigen Grenzen kritisch erörtert. Danach erweist sich die Sonderstellung vonPtychoverpa Boud. nur mikroskopisch als ausreichend begründet.Helvella Quéletii Bres. kann vonAcetabula sulcata (Pers. ex Fr.) Fuck. nicht gattungsmäßig getrennt werden, sondern ist alsAcetabula Quéletii (Bres.) Bx. nov. comb. zu bezeichnen, wenn beide Gattungen nebeneinander bestehen bleiben.Paramitra ochreoides Bx. nov. gen. et nov. spec. wird erstmalig beschrieben und stellt vermutlich einen Übergang von derOtidea-Gruppe (Wynnella Boud.) zu den Aleurieen dar.

---

Summary Starting from rare findings ofDiscomycetes in 1961 some closely related genera are compared and their limits discussed critically. The special position ofPtychoverpa Boud. is sufficiently proved only by microscopic characters. To discernHelvella Quéletii Bres. fromAcetabula sulcata (Pers. ex Fr.) Fuck. generically is not possible, it must be designated asAcetabula Quéletii (Bres.) Bx. nov. comb. if both genera shall be maintained. The new describedParamitra ochreoides Bx. nov. gen. et nov. spec. presumably is a transitional fungus between theOtidea-group (Wynnella Boud.) and theAleurieae.

---

, 1961 . . Ptychoverpa Boud. .Helvella Quéletii Bres. Acetabula sulcata (Pers. ex Fr.) Fuck. Acetabula Quéletii (Bres.) Bx. nov. comb., .Paramitra ochreoides Bx. nov. gen. et nov. spec. ; Otidea (Wynnella Boud.) Aleurieae.

     

Grundsätzliches zur Taumessungsfrage

Ohne Zusammenfassung     

Der Brotkäfer aus der freien Natur

Ohne Zusammenfassung     

Verfuch einer Bestimmung des allgemeinen objektiven forstlichen Zinsfuszes

Ohne Zusammenfassung     

Beitrag zum Crassieren von Waldbahnen und Straszen

Ohne Zusammenfassung