La présence de plantes accélère la décomposition de la matière organique du sol (MOS) au travers de l’apport de composés riches en énergie (rhizodépôts et litières) stimulant les microorganismes ; un phénomène appelé « rhizosphere priming effect » (RPE). Une augmentation de la photosynthèse, activité pourvoyeuse d'énergie rhizodéposée, pourrait augmenter le RPE et l’offre du sol en nutriments. Récemment, le modèle SYMPHONY couplant activités photosynthétiques et microbiennes du sol suggère un ajustement de l'offre du sol en nutriments (delta minéralisation-immobilisation) à la demande des plantes. Cependant, le rôle clé de la photosynthèse sur cet ajustement offre-demande reste à étudier expérimentalement.L’objectif général de la thèse est d'étudier le rôle des interactions des activités photosynthétiques et microbiennes du sol dans les régulations des flux de carbone (C) et d'azote (N) des écosystèmes. Trois écosystèmes types ont été étudiés : la prairie, la monoculture de blé et un nouveau système de culture (NSC) associant blé et plantes pérennes de la prairie. Nous émettons l’hypothèse que les plantes pérennes, via une activité photosynthétique pourvoyant les microorganismes en énergie tout au long de l'année, sont essentielles à l'ajustement offre-demande en N. De nombreux défis techniques ont été relevés afin de construire une plateforme expérimentale de 40 mésocosmes sous éclairage et température naturels. Cette plateforme permet de coupler marquage 13C des plantes, mesures continues des échanges de CO2, du RPE, de la production végétale, du stockage de C du sol, le taux de minéralisation-immobilisation d'N et du lessivage d'N. Ce dispositif nous a permis de déterminer la contribution du RPE dans les flux de C des écosystèmes comprenant la production nette de l’écosystème (NEP), la production primaire brute (GPP) et la respiration de l’écosystème (RE) exprimées en g C m-2 24h-1. Nous avons montré une relation positive linéaire entre (1) RPE et GPP et (2) RPE et biomasse aérienne (AGB) (g C m-2). A partir de ces relations, le RPE peut être prédit en utilisant les équations suivantes : (...). Nous montrons un ajustement offre-demande de l’N au cours des saisons : une forte activité photosynthétique (printemps) est liée à un RPE et un delta minéralisation-immobilisation d’N élevés alors qu’une faible activité photosynthétique (automne) est liée à un RPE et un delta minéralisation-immobilisation d’N faibles. Cet ajustement était observé dans la prairie et dans le NSC mais pas en monoculture de blé. Logiquement, la lixiviation d’N était importante en monoculture de blé alors qu’elle était quasi nulle en prairie et dans le NSC. Après deux années de maintien des trois écosystèmes types, la production aérienne totale du NSC était équivalente à la prairie, tous deux étant supérieurs d’environ un facteur deux à la monoculture de blé. Ces résultats confirment l’importance des plantes pérennes dans la synchronisation offre-demande de l’N. L’ensemble de ces investigations souligne l’importance des activités des plantes et des processus rhizosphériques dans la régulation des cycles CN des écosystèmes. Ces régulations pourront être étudiées in situ et à l'échelle globale grâce aux proxys de ces processus rhizosphériques (RPE, ajustement offre-demande) déterminés dans la thèse. Des activités photosynthétiques et rhizosphériques tout au long de l'année sont essentielles à l'ajustement offre-demande en nutriments conduisant à une forte production primaire, à la fermeture des cycles des nutriments et au stockage de MOS. Ces découvertes offrent l'opportunité de construire de nouveaux systèmes de culture, à l'image de l’association blé-plantes pérennes étudiée, à hautes performances agro-environnementales. / The presence of plants accelerates the decomposition of soil organic matter (SOM) through the supply of energy-rich compounds (rhizodeposits and litter) stimulating microorganisms; a phenomenon called rhizosphere priming effect (RPE). An increase of photosynthesis, supplying soil with rhizodeposited energy, could increase the RPE and soil nutrients offer. Recently, the SYMPHONY model coupling photosynthesis and soil microbial activities suggested an adjustment of the soil nutrient offer (delta mineralization-immobilization) to plant demand. However, the key role of photosynthesis in this offer-demand adjustment needs to be investigated experimentally.The general objective of the thesis is to study the role of interactions between photosynthesis and soil microbial activities in the regulation of carbon (C) and nitrogen (N) fluxes of ecosystems. Three ecosystem types were studied: grassland, wheat monoculture and a new cropping system (NSC) where wheat and perennial grassland species were intercropped. We hypothesize that perennial species, through a continuous photosynthetic activity supplying microorganisms with energy over the year, are essential for offer-demand adjustment.Many technical challenges were overcame to build an experimental platform of 40 mesocosms under natural light and temperature. This platform allows to couple 13C labeling of plants, continuous CO2-exchange measurements, RPE, plant production, soil C storage, N mineralization-immobilization turnover and N leaching.This experimental platform allowed us to determine the contribution of RPE to C fluxes of ecosystems including net ecosystem production (NEP), gross primary production (GPP) and ecosystem respiration (ER) expressed in g C m-2 24h-1. We found positive linear relationships between (1) RPE and GPP and (2) RPE and aboveground biomass (AGB) (g C m-2). Using these relationships, the RPE can be predicted with the following equations: (...).We show an adjustment of soil N-offer to plant N-demand across seasons: a high photosynthetic activity (spring) is linked to high RPE and delta mineralization-immobilization of N whereas a low photosynthetic activity (autumn) is linked to low RPE and delta mineralization-immobilization of N. This adjustment was observed in grassland and NSC but not in wheat monoculture. Consistently, N leaching was high in wheat monoculture while it was almost null in grassland and NSC. After two years of establishment of the three ecosystems, the total aboveground production of the NSC was equivalent to the grassland, each being about twice as high as the wheat monoculture. These results confirm the importance of perennial species in the offer-demand adjustment of N.Our findings underline the importance of plant activities and rhizosphere processes in the regulation of ecosystems C N cycles. Using the proxies of rhizosphere processes (RPE, offer-demand adjustment) provided in the thesis, further studies could investigate these regulations in situ and at the global scale. The presence of photosynthetic and rhizospheric activities over the year are essential for offer-demand adjustment of nutrients leading to high primary production, closing nutrient cycles and SOM storage. These findings offer the opportunity to build new cropping systems such as the wheat-perennial species studied, with high agro-environmental performances.

Zwischen 1630 und 1650 vollzog sich ein Wandel in Athanasius Kirchers Vermittlung des musikalischen Wissens: Musik konzipierte er im Zusammenhang der Universalwissenschaft immer mehr als Zeichen des Weltbildes im Kontext einer christlich-neuplatonischen Pansemiose. Die Studie arbeitet dies am Beispiel der "Institutiones mathematicae" (ca. 1630), der "Mathematica curiosa" (ca. 1640) und der "Musurgia universalis" (1650) heraus. Besonderes Augenmerk gilt Kirchers Umgang mit seinen Quellen, insbesondere Nikolaus von Kues, Robert Fludd und der Tradition der Philosophia perennis. / Between 1630 and 1650, a change in Athanasius Kircher's way to communicate the knowledge of music took place: Within the context of universal science, he conceptualised music increasingly as a symbol for his world view and its Christian-Neoplatonic pansemiosis. This study discusses these issues based on Kircher's "Institutiones mathematicae" (c1630), "Mathematica curiosa" (c1640), and "Musurgia universalis" (1650). Special emphasis lies on Kircher's use of his sources, particularly Nicholas of Cusa, Robert Fludd, and the tradition of Perennial philosophy.

Zwischen 1630 und 1650 vollzog sich ein Wandel in Athanasius Kirchers Vermittlung des musikalischen Wissens: Musik konzipierte er im Zusammenhang der Universalwissenschaft immer mehr als Zeichen des Weltbildes im Kontext einer christlich-neuplatonischen Pansemiose. Die Studie arbeitet dies am Beispiel der "Institutiones mathematicae" (ca. 1630), der "Mathematica curiosa" (ca. 1640) und der "Musurgia universalis" (1650) heraus. Besonderes Augenmerk gilt Kirchers Umgang mit seinen Quellen, insbesondere Nikolaus von Kues, Robert Fludd und der Tradition der Philosophia perennis. / Between 1630 and 1650, a change in Athanasius Kircher's way to communicate the knowledge of music took place: Within the context of universal science, he conceptualised music increasingly as a symbol for his world view and its Christian-Neoplatonic pansemiosis. This study discusses these issues based on Kircher's "Institutiones mathematicae" (c1630), "Mathematica curiosa" (c1640), and "Musurgia universalis" (1650). Special emphasis lies on Kircher's use of his sources, particularly Nicholas of Cusa, Robert Fludd, and the tradition of Perennial philosophy.

Soil contamination with heavy metals is a problem of worldwide concern that is still unsolved. The analysis of the current methods of soil cleaning from heavy metals leads to conclusions that phytoremediation, i.e. soil decontamination by using plants, is one of the best methods. Although this method has not received a wide application yet and possibilities of its application are still being analysed, it is one of the most prospective soil cleaning methods due to low cost and a rather efficient cleaning of the upper surface of soil. Three kinds of Poaceae f. Species – Lolium perenne L., Poa pratensis L. and Festuca pratensis Huds. – have been chosen in this work for decontaminating soil from heavy metals. These plants were grown under artificial laboratory conditions in soil which was once and periodically contaminated with heavy metals. It was established that it is the Lolium perenne L. that most efficiently removes heavy metals and cleans soil. The results of experiments show that the selected grassy plants (perennial ryegrass, meadow-grass and fescue-grass) efficiently clean soil from heavy metals (copper, lead, manganese, zinc, nickel and chromium) when soil contains both low (0.5–120 mg/kg) and high (up to 6,850 mg/kg) concentrations of these metals. Since the perennial ryegrass absorbs the highest amount of heavy metals, the highest efficiency of soil cleaning is achieved using this plant, therefore, 80 % of the mixture of grassy plants was formed of the perennial... [to full text] / Dirvožemio tarša sunkiaisiais metalais visame pasaulyje aktuali problema iki šiol neturinti universalaus sprendimo. Išanalizavus šiuo metu dirvožemio valymui nuo sunkiųjų metalų naudojamus metodus, galima daryti išvadą, kad vienas iš tinkamiausių metodų yra fitoremediacija, t. y. dirvožemio valymas nuo teršalų panaudojant augalus. Šis metodas dar nėra plačiai taikomas ir jo taikymo galimybės dar tik tiriamos tačiau, tai vienas iš perspektyviausių dirvožemio valymo metodų dėl sąlyginai mažos kainos ir pakankamai efektyvaus paviršinio dirvožemio sluoksnio išvalymo. Atliktų eksperimentinių tyrimų rezultatai parodė, kad pasirinkta žolinė augalija – daugiametė svidrė, pievinė miglė ir tikrasis eraičinas efektyviai valo dirvožemį nuo sunkiųjų metalų (vario, švino, mangano, cinko, nikelio, chromo) tiek esant mažoms (0,5–120 mg/kg), tiek didelėms (iki 6850 mg/kg) jų koncentracijoms dirvožemyje. Kadangi daugiausiai sunkiųjų metalų iš dirvožemio sorbuoja svidrė, tai dirvožemio valymo efektyvumas naudojant šią žolinės augalijos rūšį yra efektyviausias ir sudarant žolinės augalijos mišinį 80  sudarė svidrė ir po 10  eraičinas bei miglė. Eksperimentų metu tirta, kaip sunkiųjų metalų mišinio koncentracijos kenkia hidrobiontams ir nustatyta, kad didinat sunkiųjų metalų mišinio koncentracijas (iki 0,198–5,12 g/l) jos tampa letalinėmis vaivorykštiniam upėtakiui, tuo pačiu ir kitiems vandens gyvūnams.Pagal tyrimų su vaivorykštiniais upėtakiais rezultatus nustatyta, kad stebimų... [toliau žr. visą tekstą]

Dirvožemio tarša sunkiaisiais metalais visame pasaulyje aktuali problema iki šiol neturinti universalaus sprendimo. Fitoremediacija – naujai atsirandanti ir daug žadanti technologija nestipriai užterštiems dirvožemiams valyti naudojant augalus. Šiame darbe dirvožemio valymui nuo sunkiųjų metalų pasirinktos trys žolinės augalijos rūšys – svidrė, miglė ir eraičinas, augintos modelinėmis laboratorinėmis sąlygomis vieną kartą ir periodiškai sunkiaisiais metalais teršiamuose dirvožemiuose. Nustatyta, kad geriausiai sunkiuosius metalus iš dirvožemio sorbuoja ir didžiausias dirvožemio valymo efektyvumas pasiekiamas naudojant svidrę. Augalijai sorbuojant sunkiuosius metalus iš dirvožemio dalis šių metalų (Cu, Cr, Zn, Pb, Mn, Ni) koncentruojasi žolinės augalijos šaknyse, tačiau didžioji dalis ten susikaupiančių metalų (iki 90 proc.) pereina į antžeminę augalo dalį. Didžiausios sunkiųjų metalų koncentracijos augale (iki 60 proc. ir daugiau) ir atitinkamai efektyviausias dirvožemio valymas nustatytas svidrės atveju, todėl sudarant mišinį didžiąją dalį (80 proc.) jame sudaro svidrė. Sunkiųjų metalų mišinys daro neigiamą įtaką vaivorykštinio upėtakio jauniklių fiziologiniams ir morfologiniams rodikliams, todėl didinat sunkiųjų metalų mišinio koncentracijas (iki 0,198–5,12 g/l) jos tampa letalinėmis vaivorykštiniams upėtakiams, tuo pačiu ir kitiems vandens gyvūnams. Pagal tyrimų su vaivorykštiniais upėtakiais rezultatus nustatyta, kad stebimų upėtakių, gyvenusių akvariume, užterštame 5,7... [toliau žr. visą tekstą] / Soil contamination with heavy metals is a problem of worldwide concern that is still unsolved. The analysis of the current methods of soil cleaning from heavy metals leads to conclusions that phytoremediation, i.e. soil decontamination by using plants, is one of the best methods. Although this method has not received a wide application yet and possibilities of its application are still being analysed, it is one of the most prospective soil cleaning methods due to low cost and a rather efficient cleaning of the upper surface of soil. Three kinds of Poaceae f. Species – Lolium perenne L., Poa pratensis L. and Festuca pratensis Huds. – have been chosen in this work for decontaminating soil from heavy metals. These plants were grown under artificial laboratory conditions in soil which was once and periodically contaminated with heavy metals. It was established that it is the Lolium perenne L. that most efficiently removes heavy metals and cleans soil. The results of experiments show that the selected grassy plants (perennial ryegrass, meadow-grass and fescue-grass) efficiently clean soil from heavy metals (copper, lead, manganese, zinc, nickel and chromium) when soil contains both low (0.5–120 mg/kg) and high (up to 6,850 mg/kg) concentrations of these metals. Since the perennial ryegrass absorbs the highest amount of heavy metals, the highest efficiency of soil cleaning is achieved using this plant, therefore, 80 % of the mixture of grassy plants was formed of the perennial... [to full text]

Crop rotation may be used to prevent the continuous selection of particular weed species adapted to one crop type. This might be useful for weed management, economy in herbicide applications and promoting biodiversity. Common simple crop sequences might be diversified by introducing perennial forage crops. Impacts of such perennial crops on weeds were studied with four approaches : 1) Large-scale weed surveys in 632 fields in western France showed that weed species composition differed most strongly between perennial alfalfa crops and annual crops. Comparisons of fields before, during and after perennial alfalfa suggested that community composition varies in a cyclic way during such crop rotations. Several weed species problematic in annual crops were suppressed during and after perennial crops, but the appearance of other species led to equal or even higher plant diversities. 2) A 3-year field experiment with contrasting crop management options allowed an investigation of the underlying mechanisms for this: The absence of soil tillage reduced weed emergence but increased the survival of established plants. The permanent vegetation cover and frequent hay cuttings reduced weed growth, plant survival and seed production. 3) Greenhouse experiments testing the regrowth ability of individual plants after cutting showed strong differences between species and functional groups. An two-factorial experiment suggested that the negative impacts of cutting and competition on weed growth were mainly additive. 4) Special measurements of weed seed predation in the field experiment showed positive correlations with vegetation cover, indicating that this ecosystem service may be particularly fostered by perennial crops. Consistent preferences of seed predators for certain weed species indicates that seed predation may be another cause of the observed weed community shifts.

Soil P fractionation was used to examine changes in soil inorganic and organic P under grazed irrigated pasture in a long-term field trial at Winchmore in Mid-Canterbury. The soil P fractionation scheme used involved sequential extractions of soil with O.5M NaHCO₃ @ pH 8.5 (NaHCO₃ P), 0.1M NaOH (NaOH I P), 1M HCl (HCl P) and 0.1M NaOH (NaOH II P). The Winchmore trial comprised 5 treatments: control (no P since 1952), 376R (376 kg superphosphate ha⁻¹ yr⁻¹ 1952-1957, none since), 564R (564 kg superphosphate ha⁻¹ yr⁻¹ 1952-1957, none since) 188PA (188 kg superphosphate ha⁻¹ yr⁻¹ since 1952) and 376PA (376 kg superphosphate ha⁻¹ yr⁻¹ since 1952: Topsoil (0-7.5cm) samples taken from the different treatments in 1958, 1961, 1965, 1968, 1971, 1974 and 1977 were used in this study. Changes in soil P with time showed that significant increases in soil inorganic P occurred in the annually fertilised treatments (l88PA, 376PA). As expected, the overall increase in total soil inorganic P between 1958 and 1977 was greater in the 376PA treatment (159 µg P g⁻¹) than that in the 188PA treatment (37 µg P g⁻¹). However, the chemical forms of inorganic P which accumulated in the annually fertilised treatments changed with time. Between 1958 and 1971 most of the increases in soil inorganic P in these treatments occurred in the NaHCO₃ and NaOH I P fractions. On the other hand, increases in soil inorganic P in the annually fertilised treatments between 1971 and 1977 were found mainly in the HCl and NaOH II P fractions. These changes in soil P forms were attributed to the combined effects of lime addition in 1972 and increased amounts of sparingly soluble apatite P and iron-aluminium P in the single superphosphate applied during the 1970's. In the residual fertiliser treatments (376R, 564R) significant decreases in all of the soil inorganic P fractions (i.e. NaHCO₃ P, NaOH I P, HCl P, NaOH II p) occurred between 1958 and 1977 following the cessation of P fertiliser inputs in 1957. This was attributed to continued plant uptake of P accumulated in the soil from earlier P fertiliser additions. However, levels of inorganic P in the different soil P fractions in the residual fertiliser treatments did not decline to those in the control which indicated that some of the inorganic P accumulated in the soil from P fertiliser applied between 1952 and 1957 was present in very stable forms. In all treatments, significant increases in soil organic P occurred between 1958 and 1971. The overall increases in total soil organic P were greater in the annually fertilised treatments (70-86 µg P g⁻¹) than those in the residual fertiliser (55-64 µg P g⁻¹) and control (34 µg P g⁻¹) treatments which reflected the respective levels of pasture production in the different treatments. These increases in soil organic P were attributed to the biological conversion of native and fertiliser inorganic P to organic P in the soil via plant, animal and microbial residues. The results also showed that annual rates of soil organic P accumulation between 1958 and 1971 decreased with time which indicated that steady-state conditions with regard to net 'organic P accumulation were being reached. In the residual fertiliser treatments, soil organic P continued to increase between 1958 and 1971 while levels of soil inorganic P and pasture production declined. This indicated that organic P which accumulated in soil from P fertiliser additions was more stable and less available to plants than inorganic forms of soil P. Between 1971 and 1974 small (10-38 µg P g⁻¹) but significant decreases in total soil organic P occurred in all treatments. This was attributed to increased mineralisation of soil organic P as a result of lime (4 t ha⁻¹) applied to the trial in 1972 and also to the observed cessation of further net soil organic P accumulation after 1971. Liming also appeared to affect the chemical nature of soil organic P as shown by the large decreases in NaOH I organic P(78-88 µg P g⁻¹) and concomitant smaller increases in NaOH II organic P (53-65 µg P g⁻¹) which occurred in all treatments between 1971 and 1974. The chemical nature of soil organic P in the Winchmore long-term trial was also investigated using 31p nuclear magnetic resonance (NMR) spectroscopy and gel filtration chromatography. This involved quantitative extraction of organic P from the soil by sequential extraction with 0.1M NaOH, 0.2M aqueous acetylacetone (pH 8.3) and 0.5M NaOH following which the extracts were concentrated by ultrafiltration. Soils (0-7.5cm) taken from the control and 376PA annually fertilised treatments in 1958, 1971 and 1983 were used in this study. 31p NMR analysis showed that most (88-94%) of the organic P in the Winchmore soils was present as orthophosphate monoester P while the remainder was found as orthophosphate diester and pyrophosphate P. Orthophosphate monoester P also made up almost all of the soil organic P which accumulated in the 376PA treatment between 1958 and 1971. This indicated that soil organic P in the 376PA and control treatments was very stable. The gel filtration studies using Sephadex G-100 showed that most (61-83%) of the soil organic P in the control and 376PA treatments was present in the low molecular weight forms (<100,000 MW), although the proportion of soil organic P in high molecular weight forms (>100,000 MW) increased from 17-19% in 1958 to 38-39% in 1983. The latter was attributed to the microbial humification of organic P and indicated a shift toward more complex and possibly more stable forms of organic P in the soil with time. Assuming that the difference in soil organic P between the control and 376PA soils sampled in 1971 and 1983 represented the organic P derived from P fertiliser additions, results showed that this soil organic P was evenly distributed between the high and low molecular weight fractions. An exhaustive pot trial was used to examine the relative availability to plants of different forms of soil inorganic and organic P in long-term fertilised pasture soils. This involved growing 3 successive crops of perennial ryegrass (Lolium perenne) in 3 Lismore silt loam (Udic Ustochrept) soils which had received different amounts of P fertiliser for many years. Two of the soils were taken from the annually fertilised treatments in the Winchmore long term trial (188PA, 376PA) and the third (Fairton) was taken from a pasture which had been irrigated with meatworks effluent for over 80 years (65 kg P ha⁻¹ yr⁻¹). Each soil was subjected to 3 treatments, namely control (no nutrients added), N100 and N200. The latter treatments involved adding complete nutrient solutions with different quantities of N at rates of 100kg N ha⁻¹ (N100) and 200kg N ha⁻¹ (N200) on an area basis. The soil P fractionation scheme used was the same as that used in the Winchmore long-term trial study (i.e. NaHCO₃ P, NaOH I P, HCl P, NaOH II p). Results obtained showed that the availability to plants of different extracted inorganic P fractions, as measured by decreases in P fractions before and after 3 successive crops, followed the order: NaHCO₃ P > NaOH I P > HCl P = NaOH II P. Overall decreases in the NaHCO₃ and NaOH I inorganic P fractions were 34% and 16% respectively, while corresponding decreases in the HCl and NaOH II inorganic P fractions were small «10%) and not significant. However, a significant decrease in HCl P (16%) was observed in one soil (Fairton-N200 treatment) which was attributed to the significant decrease in soil pH (from 6.2 to 5.1) which occurred after successive cropping. Successive cropping had little or no effect on the levels of P in the different soil organic P fractions. This indicated that net soil organic P mineralisation did not contribute significantly to plant P uptake over the short-term. A short-term field experiment was also conducted to examine the effects of different soil management practices on the availability of different forms of P to plants in the long-term fertilised pasture soils. The trial was sited on selected plots of the existing annually fertilised treatments in the Winchmore long-term trial (188PA, 376PA) and comprised 5 treatments: control, 2 rates of lime (2 and 4 t ha⁻¹ ) , urea fertiliser (400kg N ha⁻¹ ) and mechanical cultivation. The above ground herbage in the uncultivated treatments was harvested on 11 occasions over a 2 year period and at each harvest topsoil (0-7.5 cm) samples were taken from all of the treatments for P analysis. The soil P fractionation scheme used in this particular trial involved sequential extractions with 0.5M NaHCO₃ @ pH 8.5 (NaHCO₃ P), 0.1M NaOH (NaOH P), ultrasonification with 0.1M NaOH (sonicate-NaOH p) and 1M HCl (HCl P). In addition, amounts of microbial P in the soils were determined. The results showed that liming resulted in small (10-21 µg P g⁻¹) though significant decreases in the NaOH soil organic P fraction in the 188PA and 376PA plots. Levels of soil microbial P were also found to be greater in the limed treatments compared with those in the controls. These results indicated that liming increased the microbial mineralisation of soil organic P in the Winchmore soils. However, pasture dry matter yields and P uptake were not significantly affected. Although urea significantly increased dry matter yields and P uptake, it did not appear to significantly affect amounts of P in the different soil P fractions. Mechanical cultivation and the subsequent fallow period (18 months) resulted in significant increases in amounts of P in the NaHCO₃ and NaOH inorganic P fractions. This was attributed to P released from the microbial decomposition of plant residues, although the absence of plants significantly reduced levels of microbial P in the cultivated soils. Practical implications of the results obtained in the present study were presented and discussed.

La rotation de cultures peut être utilisée pour empêcher la sélection continue d’espèces adventices adaptées à un type de culture. Elle pourrait favoriser la gestion des adventices, l’économie d’herbicides et la biodiversité. Les successions de cultures simples d’aujourd’hui pourraient être diversifiées par des cultures fourragères pérennes. Les impacts des ces cultures sur les adventices ont été étudié utilisant quatre approches : 1) Des relevés d’adventices sur 632 champs dans l’ouest de la France ont montré que la composition spécifique varie le plus entre des cultures fourragères pérennes et des cultures annuelles. Une comparaison des champs avant, pendant, et après des cultures fourragères pérennes a suggéré que la composition des communautés varie d’une manière cyclique pendant ces rotations. Plusieurs espèces problématiques dans des cultures annuelles ont été supprimées pendant et après les cultures pérennes, mais l’apparition d’autres espèces a produit une diversité de plantes comparable, voire supérieure. 2) Une expérimentation au champ de trois ans avec des modes de gestion contrastés a permis d’étudier les mécanismes sous-jacents: L’absence de travail du sol a réduit la levée des adventices, mais a augmenté la survie des plantes adultes. Le couvert végétal permanent et les fauches fréquentes ont réduit la croissance, la survie des plantes et la production de graines. 3) Des expérimentations sous serre analysant la croissance poste fauche de plantes individuelles ont montré des différences importantes entre espèces et groupes fonctionnels. Une expérimentation à deux facteurs a suggéré que les impacts négatifs de la fauche et de la compétition sur la croissance des adventices ont été additifs. 4) Des mesures spéciales de prédation de graines d’adventices sur l’expérimentation au champ ont montré des corrélations positives avec le couvert végétal et la prédation, indiquant une importance particulière de ce service écosystémique dans des cultures pérennes. La préférence des graines de certaines espèces montre que la prédation de graines peut être une autre cause des changements de communautés d’adventices. / Crop rotation may be used to prevent the continuous selection of particular weed species adapted to one crop type. This might be useful for weed management, economy in herbicide applications and promoting biodiversity. Common simple crop sequences might be diversified by introducing perennial forage crops. Impacts of such perennial crops on weeds were studied with four approaches : 1) Large-scale weed surveys in 632 fields in western France showed that weed species composition differed most strongly between perennial alfalfa crops and annual crops. Comparisons of fields before, during and after perennial alfalfa suggested that community composition varies in a cyclic way during such crop rotations. Several weed species problematic in annual crops were suppressed during and after perennial crops, but the appearance of other species led to equal or even higher plant diversities. 2) A 3-year field experiment with contrasting crop management options allowed an investigation of the underlying mechanisms for this: The absence of soil tillage reduced weed emergence but increased the survival of established plants. The permanent vegetation cover and frequent hay cuttings reduced weed growth, plant survival and seed production. 3) Greenhouse experiments testing the regrowth ability of individual plants after cutting showed strong differences between species and functional groups. An two-factorial experiment suggested that the negative impacts of cutting and competition on weed growth were mainly additive. 4) Special measurements of weed seed predation in the field experiment showed positive correlations with vegetation cover, indicating that this ecosystem service may be particularly fostered by perennial crops. Consistent preferences of seed predators for certain weed species indicates that seed predation may be another cause of the observed weed community shifts. / Fruchtfolgen können dazu dienen, die kontinuierliche Selektion von Unkrautarten zu verhindern, die an eine bestimmte Kultur angepasst sind. Dies könnte dem Unkrautmanagement, der Einsparung von Herbiziden, und der Biodiversität dienen. Heutige, sehr einfache Furchtfolgen könnten durch mehrjährige Futterkulturen diversifiziert werden. Die Einflüsse solcher mehrjähriger Kulturen auf Unkräuter wurden in vier Ansätzen untersucht : 1) Vegetationsaufnahmen auf 632 Feldern in Westfrankreich zeigten, dass die Unkrautzusammensetzung zwischen mehrjährigen Futterkulturen und einjährigen Kulturen stark variiert. Der Vergleich von Feldern vor, während und nach mehrjährigen Futterkulturen legte nahe, dass die Pflanzengemeinschaft während solcher Fruchtfolgen zyklisch variiert. Mehrere problematische Unkrautarten wurden während und nach den mehrjährigen Kulturen zurückgedrängt. Das Auftauchen anderer Arten führte jedoch zu einer gleichbleibenden oder leicht erhöhten Pflanzenvielfalt. 2) Ein dreijähriger Feldversuch mit verschiedenen Bearbeitungsoptionen ermöglichte es, die zugrunde liegenden Mechanismen zu untersuchen: Die fehlende Bodenbearbeitung hat das Auflaufen der Unkräuter reduziert und das Überleben der adulten Pflanzen erhöht. Die permanente Vegetationsbedeckung und die häufigen Heuschnitte haben das Wachstum, das Überleben und die Samenproduktion vermindert. 3) Gewächshausexperimente zum Nachwachsen von Unkrautpflanzen nach Heuschnitten zeigten große Unterschiede zwischen verschiedenen Arten und funktionellen Gruppen. Ein Experiment mit zwei Faktoren lässt vermuten, dass die negativen Effekte der Schnitte und der Konkurrenz auf das Unkrautwachstum sich addieren. 4) Spezielle Messungen der Prädation von Unkrautsamen auf den untersuchten Feldern zeigten positive Korrelationen mit der Vegetationsbedeckung, was auf eine besondere Wichtigkeit dieser Ökosystemdienstleistung in ausdauernden Kulturen hindeutet. Die Präferenz von bestimmten Samenarten deutet darauf hin, dass Samenprädation ein weiterer Grund für die beobachteten Änderungen der Unkrautgemeinschaften sein kann.

Zwischen 1630 und 1650 vollzog sich ein Wandel in Athanasius Kirchers Vermittlung des musikalischen Wissens: Musik konzipierte er im Zusammenhang der Universalwissenschaft immer mehr als Zeichen des Weltbildes im Kontext einer christlich-neuplatonischen Pansemiose. Die Studie arbeitet dies am Beispiel der 'Institutiones mathematicae' (ca. 1630), der 'Mathematica curiosa' (ca. 1640) und der 'Musurgia universalis' (1650) heraus. Besonderes Augenmerk gilt Kirchers Umgang mit seinen Quellen, insbesondere Nikolaus von Kues, Robert Fludd und der Tradition der Philosophia perennis. / Between 1630 and 1650, a change in Athanasius Kircher''s way to communicate the knowledge of music took place: Within the context of universal science, he conceptualised music increasingly as a symbol for his world view and its Christian-Neoplatonic pansemiosis. This study discusses these issues based on Kircher''s 'Institutiones mathematicae' (c1630), 'Mathematica curiosa' (c1640), and 'Musurgia universalis' (1650). Special emphasis lies on Kircher''s use of his sources, particularly Nicholas of Cusa, Robert Fludd, and the tradition of Perennial philosophy.

Zwischen 1630 und 1650 vollzog sich ein Wandel in Athanasius Kirchers Vermittlung des musikalischen Wissens: Musik konzipierte er im Zusammenhang der Universalwissenschaft immer mehr als Zeichen des Weltbildes im Kontext einer christlich-neuplatonischen Pansemiose. Die Studie arbeitet dies am Beispiel der 'Institutiones mathematicae' (ca. 1630), der 'Mathematica curiosa' (ca. 1640) und der 'Musurgia universalis' (1650) heraus. Besonderes Augenmerk gilt Kirchers Umgang mit seinen Quellen, insbesondere Nikolaus von Kues, Robert Fludd und der Tradition der Philosophia perennis. / Between 1630 and 1650, a change in Athanasius Kircher''s way to communicate the knowledge of music took place: Within the context of universal science, he conceptualised music increasingly as a symbol for his world view and its Christian-Neoplatonic pansemiosis. This study discusses these issues based on Kircher''s 'Institutiones mathematicae' (c1630), 'Mathematica curiosa' (c1640), and 'Musurgia universalis' (1650). Special emphasis lies on Kircher''s use of his sources, particularly Nicholas of Cusa, Robert Fludd, and the tradition of Perennial philosophy.