Effets du climat et des conditions météorologiques locales sur les changements de masse saisonniers du mouflon d'Amérique (Ovis Canadensis)

Comprendre de quelle façon les populations animales répondent aux conditions qui prévalent dans leur environnement revêt une grande importance. Les conditions climatiques et météorologiques sont une source importante de variabilité dans l'environnement et celles-ci ont des répercussions sur les espèces sauvages, en affectant leur physiologie, leur comportement et leurs ressources. Les ongulés alpins et nordiques font face à une succession annuelle de conditions environnementales favorables et défavorables, entraînant chez ceux-ci d'importants changements de masse saisonniers. Chez ces grands herbivores, la masse est importante puisqu'elle est positivement corrélée à la survie et à la reproduction. C'est pourquoi il est essentiel d'investiguer les paramètres affectant les changements de masse saisonniers. L'objectif principal de ma maîtrise était donc d'identifier et de mieux comprendre l'effet des conditions climatiques et météorologiques sur les changements de masse estivaux et hivernaux d'un ongulé alpin: le mouflon d'Amérique (Ovis canadensis). Pour atteindre cet objectif, j'ai utilisé les données du suivi à long terme de la population de mouflons de Ram Mountain, Alberta. Les mesures de masse répétées prises lors des captures permettent d'estimer la masse printanière et automnale des individus, ainsi que leur gain de masse estival et leur changement de masse hivernal. En affectant les coûts énergétiques de la thermorégulation et des déplacements et en influençant la végétation, les conditions climatiques et météorologiques peuvent avoir d'importantes conséquences sur les changements de masse des ongulés alpins. La température, les précipitations et un indice de climat global (le «Pacific Decadal Oscillation»; PDO) ont donc été utilisés afin de caractériser les conditions environnementales et d'investiguer les effets de ces variables sur les changements de masse saisonniers des individus de différentes classes d'âge et de sexe. Des températures froides au printemps ont engendré de plus grands gains de masse estivaux. Des printemps froids peuvent ralentir la maturation des plantes, engendrant une plus grande période où il est possible de s'alimenter de jeunes plantes nutritives, ce qui explique probablement cet effet positif des printemps froids. Cet effet doit toutefois être nuancé puisque les changements de masse hivernaux étaient également influencés par la température printanière, avec des printemps chauds menant à de plus faibles pertes de masse. Il semble que cet effet était dû à une apparition hâtive de la végétation, menant à une prise de masse des mouflons avant qu'ils ne soient capturés au printemps. Cela suggère qu'en affectant la disponibilité et la qualité de la végétation, les conditions printanières ont des répercussions à la fois sur le gain de masse estival, mais également sur les changements de masse hivernaux des mouflons. Le PDO au printemps a un effet positif important sur le gain de masse des adultes mâles lorsque la densité est faible. Des températures chaudes à l'automne engendrent de plus grands gains de masse pendant l'hiver chez les agneaux mâles (la plupart des agneaux gagnent de la masse l'hiver), potentiellement en augmentant la période possible de prise de masse pour ces jeunes individus. Les femelles de deux ans et les mâles adultes ont perdu plus de masse lors d'hivers avec beaucoup de précipitations et des températures froides, respectivement. Finalement, ce projet de recherche a permis d'identifier les variables climatiques et météorologiques clés affectant les changements de masse saisonniers d'un ongulé alpin. Cette étude a également mis en évidence des effets du PDO sur les changements de masse saisonniers, soulignant que de tels indices peuvent s'avérer utiles afin de les mettre en lien avec la variation phénotypique chez les espèces sauvages, et ce sans qu'il n'y ait nécessairement de fortes corrélations entre ces indices et les variables météorologiques locales.

Regional habitat needs of a nationally listed species, Canada Warbler (Cardellina canadensis), in Alberta, Canada

Understanding factors that affect the distribution and abundance of species is critical to developing effective management plans for conservation. Our goal was to quantify the distribution and abundance of Canada Warbler (Cardellina canadensis), a threatened old-forest associate in Alberta, Canada. The Canada Warbler has declined across its range, including in Alberta where habitat loss and alteration from urban expansion, forestry, and energy development are changing the forest landscape. We used 110,427 point count survey visits from 32,287 unique survey stations to model local-level (150-m radius circular buffers) and stand-level (564-m radius circular buffers) habitat associations of the Canada Warbler. We found that habitat supporting higher densities of Canada Warblers was locally concentrated yet broadly distributed across Alberta’s boreal forest region. Canada Warblers were most commonly associated with older deciduous forest at the local scale, particularly near small, incised streams, and greater amounts of deciduous forest at the stand scale. Predicted density was lower in other forest types and younger age classes measured at the local scale. There was little evidence that local-scale fragmentation (i.e., edges created by linear features) influenced Canada Warbler abundance. However, current forestry practices in the province likely will reduce the availability of Canada Warbler habitat over time by cutting old deciduous forest stands. Our results suggest that conservation efforts aimed at Canada Warbler focus on retaining large stands of old deciduous forest, specifically stands adjacent to streams, by increasing the width of deciduous retention buffers along streams during harvest and increasing the size and number of old forest residual patches in harvested stands.

Comparative Efficacy of Diquat for Control of Two Members of the Hydrocharitaceae: Elodea and Hydrilla

The submersed plants hydrilla (Hydrilla verticillata (L.f.) Royle) and elodea (Elodea canadensis Rich.) are both members of the Hydrocharitaceae family and cause problems in waterways throughout the world. Diquat (6,7-dihydrodipyrido[1,2-α:2’,1’-c]pyrazinediium dibromide) is a contact herbicide used to control nuisance submersed and floating aquatic macrophytes. There is no readily available information in the literature on the control of elodea under various diquat concentration and exposure times (CET) and other than a study by Van et. al 1987, little on hydrilla. Since CET relationships are critical in controlling submersed plants in areas influenced by water exchange, this study was designed to evaluate the efficacy of diquat on hydrilla and elodea under various CET scenarios. (PDF has 3 pages.)

Endothall species selectivity evaluation: northern latitude aquatic plant community

Species selectivity of the aquatic herbicide dipotassium salt of endothall (Aquathol® K) was evaluated on plant species typically found in northern latitude aquatic plant communities. Submersed species included Eurasian watermilfoil (Myriophyllum spicatum L.), curlyleaf pondweed (Potamogeton crispus L.), Illinois pondweed (Potamogeton illinoensis Morong.), sago pondweed (Potamogeton pectinatus L.), coontail (Ceratophyllum demersum L.), elodea (Elodea canadensis Michx.) and wildcelery (Vallisneria americana L.). Emergent and floating-leaf plant species evaluated were cattail (Typha latifolia L.), smartweed (Polygonum hydropiperoides Michx.), pickerelweed (Pontederia cordata L.) and spatterdock (Nuphar advena Aiton). The submersed species evaluations were conducted in 7000 L mesocosm tanks, and treatment rates included 0, 0.5 1.0, 2.0, and 4.0 mg/L active ingredient (ai) endothall (dipotassium salt of endothall). The exposure period consisted of a 24-h flow through half-life for 7 d. The cattail and smartweed evaluation was conducted in 860 L mesocosm tanks, and the spatterdock and pickerelweed evaluations were conducted in 1600 L mesocosm tanks. Treatment rates for the emergent and floating-leafed plant evaluations included 0, 0.5, 2.0 and 4.0 mg/L ai endothall, and the exposure period consisted of removing and replacing half the water from each tank, after each 24 h period for a duration of 120 h. Biomass samples were collected at 3 and 8 weeks after treatment (WAT). Endothall effectively controlled Eurasian watermilfoil and curlyleaf pondweed at all of the application rates, and no significant regrowth was observed at 8 WAT. Sago pondweed, wildcelery, and Illinois pondweed biomass were also significantly reduced following the endothall application, but regrowth was observed at 8 WAT. Coontail and elodea showed no effects from endothall application at the 0.5, 1.0, and 2.0 mg/L application rates, but coontail was controlled at 4.0 mg/L rate. Spatterdock, pickerelweed, cattail, and smartweed were not injured at any of the endothall application rates.

The Impact of Endothall on the Aquatic Plant Community of Kress Lake, Washington

CA dense mat-forming population of Eurasian watermilfoil ( Myriophyllum spicatum L . ) was interfering with fishing and recreation in a small western Washington lake. A low concentration (1.5 mg/L active ingredient) of the herbicide endothall formulated as Aquathol® K was used in 2000 to attempt to selectively control the Eurasian watermilfoil. Aquatic plant biomass and frequency data were collected before treatment, ten weeks after treatment and during the growing season for 3 additional years. Macrophyte data were analyzed to assess the herbicide’s impacts on Eurasian watermilfoil as well as the rest of the aquatic plant community. Results showed a significant decrease in Eurasian watermilfoil biomass and frequency 10 weeks after treatment. The Eurasian watermilfoil continued to be present, but at a significantly reduced level through the remainder of the study (3 years after treatment). Of the native plant species, large-leaf pondweed ( Potamogeton amplifolius Tucker . ) frequency and biomass was significantly reduced after treatment. Common elodea ( Elodea canadensis Rich.), muskgrass ( Chara sp. Vallaint.) and bladderwort ( Utricularia sp. L.) all increased significantly after treatment. (PDF has 6 pages.)

Análise cladística de táxons atribuídos aos peixes euteleósteos basais

Os teleósteos são o grupo mais diversificado entre os vertebrados e seu registro mais antigo data do Jurássico. Sua atual classificação inclui quatro clados, dentre os quais Euteleostei é o mais avançado e variado. Apesar de todos os trabalhos a respeito do grupo, ele ainda não possui diagnose, definição e composição precisas. A discordância entre autores é ilustrada pelas nove diferentes propostas filogenéticas elaboradas nos últimos 30 anos. Muitos fósseis do Cretáceo são classificados como euteleósteos basais por falta de conhecimento morfológico, enquanto outros fósseis possuem classificação sistemática controversa ou compartilham aspectos estruturais com euteleósteos basais. Nesse contexto, os objetivos da presente dissertação são avaliar o monofiletismo de euteleósteos basais e recuperar relações filogenéticas de táxons do Nordeste do Brasil, África, Europa, Ásia e América do Norte atribuídos aos euteleósteos basais. Sete táxons brasileiros (i.e., Beurlenichthys ouricuriensis, Britoichthys marizalensis, Clupavus brasiliensis, Santanasalmo elegans, Santanichthys diasii, Scombroclupeoides scutata e novo euteleósteo da Bacia de Pelotas) e 14 táxons de localidades estrangeiras (i.e., Avitosmerus canadensis, Barcarenichthys joneti, Chanoides macropoma, Clupavus maroccanus, Gaudryella gaudryi, Humbertia operta, Kermichthys daguini, Leptolepides spratiiformis, Lusitanichthys characiformis, Nybelinoides brevis, Orthogonikleithrus leichi, Pattersonella formosa, Wenzichthys congolensis e Tchernovichthys exspectatum) foram analisados através de observação direta, fotografias, desenhos e descrições e submetidos a uma análise de Sistemática Filogenética utilizando o princípio da parcimônia. Três espécies recentes (i.e., Elops saurus, Hoplias malabaricus e Salmo trutta) foram usadas como grupo externo. Sessenta e dois caracteres foram selecionados e, como resultado, seis árvores igualmente parcimoniosas foram obtidas com 325 passos, índice de consistência (CI) de 0,2523 e índice de retenção (RI) de 0,4309. O consenso estrito é representado pela seguinte topologia: ((C. marocanus), (C. brasiliensis, (H. malabaricus + S. diasii))) ((G. gaudryi, (C. macropoma + L. characiformis)), (K. daguini), ((A. canadensis, (novo euteleósteo, (S. elegans + W. congolensis), (B. ouricuriensis + B. marizalensis)), (L. spratiiformis, (S. scutata, (N. brevis + P. formosa))), (B. joneti), (O. leichi), (H. operta + T. exspectatum), indicando que euteleósteos basais não formam um grupo monofilético e que as atuais sinapomorfias propostas são insuficientes para suportar o grupo.

我国严重威胁性外来入侵植物入侵与扩散历史过程重建及其潜在分布区的预测

外来生物入侵已经在世界范围内造成严重的危害，它不仅导致生物多样性的减少和丧失而且威胁着全球的生态环境和经济发展。入侵种在入侵区域的种群扩散是入侵种带来风险的最根本问题，也是其造成危害的重要原因。研究入侵物种的扩散规律可以了解其在入侵地的入侵状况和扩散趋势，这对制定合理的控制措施具有重要意义。本研究选取14种在我国具有较强威胁性的外来入侵植物，通过对其入侵历史动态的分析，判断其在我国的入侵与扩散阶段，进而预测其在我国的潜在分布区。这14种外来植物为紫茎泽兰（Ageratina adenophora）、土荆芥 （Chenopodium ambrosioides.）、喜旱莲子草（Alternanthera philoxeroides）、反枝苋（Amaranthus retroflexus）、刺苋（Amaranthus spinosus）、皱果苋（Amaranthus viridis）、北美独行菜（Lepidium virginicum）、藿香蓟（Ageratum conyzoides）、钻形紫菀（Aster subulatus）、小蓬草（Conyza canadensis）、一年蓬（Erigeron annuus）、牛膝菊（Galinsoga paviflora）、飞机草（Eupatorium odorata）和北美商陆（Phytolacca americana）。 　　紫茎泽兰最早于20世纪40年代入侵我国，经过1940—1960年长达20年的时滞期，紫茎泽兰开始在云南及其临近的省份如四川、贵州和广西迅速扩散。其中，紫茎泽兰在南亚热带和中亚热带气候条件下的扩散速度为20公里/年，而在垂直地带性北亚热带地区的扩散速度为6.8公里/年。紫茎泽兰仍没有入侵到垂直地带性暖温带地区。尽管1990年后，紫茎泽兰在云南基本停止扩散，但其在邻近省（市）的快速传播表明紫茎泽兰在我国仍处在扩散阶段，还没有达到饱和阶段。生态位模型预测结果和紫茎泽兰在已经入侵地区扩散的地理生态式样基本相符。我国南部及中南部地区的气候条件十分适合紫茎泽兰生长。而在华中地区，由于环境条件不太适宜，其扩散速度会相对较慢。我国北部和西北部的气候条件完全不适合紫茎泽兰生存。因此，我国南部和中南部广大未入侵地区将会受到紫茎泽兰入侵和快速扩散的严重威胁，对此应该立即采取紧急措施。 　　自从紫茎泽兰于1978年首次入侵四川省以来，已经在四川、重庆和湖北大面积扩散。紫茎泽兰在此新近入侵区域主要沿河流、公路、铁路扩散。其中沿安宁河、108国道和成昆铁路向北扩散的平均速度为19公里/年，而沿金沙江－长江向东北扩散的平均速度为33公里/年。特别是2000年以后，紫茎泽兰沿金沙江－长江的扩散速度达到了88公里/年。紫茎泽兰得以如此迅速扩散是其本身生物学特性和当地地理生态特点多种因素之间一系列耦合关系共同作用的结果。人类活动和1998年金沙江－长江特大洪水也促进了紫茎泽兰在该地区的扩散。另一方面，紫茎泽兰在新近入侵地区的垂直分布范围说明随海拔高度上升所引起的垂直地带性气候变冷是紫茎泽兰入侵和扩散的自然限制条件。 　　此外，通过对其余13种外来入侵植物入侵历史过程重建发现，除了牛膝菊、反枝苋和皱果苋最早入侵地位于内陆地区以外，其余10种外来入侵植物的最早入侵地都位于我国的东部、南部沿海和西南边境地区。这13种外来植物通常不是通过单一途径传入，而是通过两种或多种途径传入不同的地点。相应地，入侵后也呈现不同的扩散模式。这13种外来植物在我国大体上包括5种入侵和扩散式样即1）从南部沿海和西南边境分别向内陆扩散，如霍香蓟、飞机草，北美商陆;2）从东部沿海向内陆扩散，例如钻形紫菀，小蓬草、北美独行菜和喜旱莲子草;3）从东部沿海、南部沿海和西南边境分别向内陆扩散，如刺苋;4）从南部沿海向内陆扩散，如土荆芥;5）从最早入侵的内陆地区向周边地区扩散，如反枝苋、牛膝菊和皱果苋。分布区动态分析显示当前这13种外来入侵植物在我国都还处在扩散阶段，而且有些外来植物还处在快速扩散阶段，如飞机草。 　　在上述研究基础上，我们对这13种外来入侵植物开展了生态位模型适生区预测和比较分析。并且结合其扩散动态和当前分布现状，我们对其潜在的分布区及扩散趋势进行了系统分析和预测。飞机草、土荆芥、霍香蓟、牛膝菊和北美商陆，这5种外来植物的现有分布区明显小于其在我国的适生区，因此它们在我国的潜在分布区很广，应给予足够的重视。喜旱莲子草、反枝苋、皱果苋、北美独行菜、一年蓬、钻行紫菀和北美商陆在我国的入侵范围与其适生区域之间基本重合，但在其入侵范围内仍存在大面积的未入侵区域。这些未入侵地区通常被已入侵区域所包围，因此也应当给予足够的重视。刺苋和小蓬草在我国的潜在的分布区相对较小，这些植物已经基本上完全入侵了其适生区。因此，这些植物在我国向临近区域继续扩散的可能性不大。 　　

不同水生植物对滇池入湖河道污水净化效能的比较

有关水生植物净化污水的研究已有广泛报道,但现有成果多来源于静态的室内研究,所用植物多为生活型接近的物种。为了比较不同生活型植物对河道污水的原位净化效果差异,构建了由水芹菜(Oenanthe javanica)、马尾草(Equisetum flu-viatile)、伊乐藻(Elodea Canadensis Michx.)和狐尾藻(Myriophyllum verticillatum L.)等4种不同生活型水生植物组成的水生植物塘系统,研究塘中不同植物对滇池入湖河道污水中氮、磷等指标去除效能的差异。结果表明

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 December 2009-31 January 2010

This article documents the addition of 220 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Allanblackia floribunda, Amblyraja radiata, Bactrocera cucurbitae, Brachycaudus helichrysi, Calopogonium mucunoides, Dissodactylus primitivus, Elodea canadensis, Ephydatia fluviatilis, Galapaganus howdenae howdenae, Hoplostethus atlanticus, Ischnura elegans, Larimichthys polyactis, Opheodrys vernalis, Pelteobagrus fulvidraco, Phragmidium violaceum, Pistacia vera, and Thunnus thynnus. These loci were cross-tested on the following species: Allanblackia gabonensis, Allanblackia stanerana, Neoceratitis cyanescens, Dacus ciliatus, Dacus demmerezi, Bactrocera zonata, Ceratitis capitata, Ceratitis rosa, Ceratits catoirii, Dacus punctatifrons, Ephydatia mülleri, Spongilla lacustris, Geodia cydonium, Axinella sp. Ischnura graellsii, Ischnura ramburii, Ischnura pumilio, Pistacia integerrima and Pistacia terebinthus. © 2010 Blackwell Publishing Ltd.

Historical data reveal power-law dispersal patterns of invasive aquatic species.

Understanding how invasive species spread is of particular concern in the current era of globalisation and rapid environmental change. The occurrence of super-diffusive movements within the context of Lévy flights has been discussed with respect to particle physics, human movements, microzooplankton, disease spread in global epidemiology and animal foraging behaviour. Super-diffusive movements provide a theoretical explanation for the rapid spread of organisms and disease, but their applicability to empirical data on the historic spread of organisms has rarely been tested. This study focuses on the role of long-distance dispersal in the invasion dynamics of aquatic invasive species across three contrasting areas and spatial scales: open ocean (north-east Atlantic), enclosed sea (Mediterranean) and an island environment (Ireland). Study species included five freshwater plant species, Azolla filiculoides, Elodea canadensis, Lagarosiphon major, Elodea nuttallii and Lemna minuta; and ten species of marine algae, Asparagopsis armata, Antithamnionella elegans, Antithamnionella ternifolia, Codium fragile, Colpomenia peregrina, Caulerpa taxifolia, Dasysiphonia sp., Sargassum muticum, Undaria pinnatifida and Womersleyella setacea. A simulation model is constructed to show the validity of using historical data to reconstruct dispersal kernels. Lévy movement patterns similar to those previously observed in humans and wild animals are evident in the re-constructed dispersal pattern of invasive aquatic species. Such patterns may be widespread among invasive species and could be exacerbated by further development of trade networks, human travel and environmental change. These findings have implications for our ability to predict and manage future invasions, and improve our understanding of the potential for spread of organisms including infectious diseases, plant pests and genetically modified organisms.

Decomposing the mid-holocene Tsuga decline in eastern North America

The mid-Holocene decline of Tsuga canadensis (hereafter Tsuga) populations across eastern North America is widely perceived as a synchronous event, driven by pests/pathogens, rapid climate change, or both. Pattern identification and causal attribution are hampered by low stratigraphic density of pollen-sampling and radiometric dates at most sites, and by absence of highly resolved, paired pollen and paleoclimate records from single sediment cores, where chronological order of climatic and vegetational changes can be assessed. We present an intensely sampled (contiguous 1-cm intervals) record of pollen and water table depth (inferred from testate amoebae) from a single core spanning the Tsuga decline at Irwin Smith Bog in Lower Michigan, with high-precision chronology. We also present an intensively sampled pollen record from Tower Lake in Upper Michigan. Both sites show high-magnitude fluctuations in Tsuga pollen percentages during the pre-decline maximum. The terminal decline is dated at both sites ca. 5000 cal yr BP, some 400 years later than estimates from other sites and data compilations. The terminal Tsuga decline was evidently heterochronous across its range. A transient decline ca. 5350 cal yr BP at both sites may correspond to the terminal decline at other sites in eastern North America. At Irwin Smith Bog, the terminal Tsuga decline preceded an abrupt and persistent decline in water table depths by;200 years, suggesting the decline was not directly driven by abrupt climate change. The Tsuga decline may best be viewed as comprising at least three phases: a long-duration predecline maximum with high-magnitude and high-frequency fluctuations, followed by a terminal decline at individual sites, followed in turn by two millennia of persistently low Tsuga populations. These phases may not be causally linked, and may represent dynamics taking place at multiple temporal and spatial scales. Further progress toward understanding the phenomenon requires an expanded network of high-resolution pollen and paleoclimate chronologies.

Historical data reveal power-law dispersal patterns of invasive aquatic species

Understanding how invasive species spread is of particular concern in the current era of globalisation and rapid environmental change. The occurrence of super-diffusive movements within the context of Lévy flights has been discussed with respect to particle physics, human movements, microzooplankton, disease spread in global epidemiology and animal foraging behaviour. Super-diffusive movements provide a theoretical explanation for the rapid spread of organisms and disease, but their applicability to empirical data on the historic spread of organisms has rarely been tested. This study focuses on the role of long-distance dispersal in the invasion dynamics of aquatic invasive species across three contrasting areas and spatial scales: open ocean (north-east Atlantic), enclosed sea (Mediterranean) and an island environment (Ireland). Study species included five freshwater plant species, Azolla filiculoides, Elodea canadensis, Lagarosiphon major, Elodea nuttallii and Lemna minuta; and ten species of marine algae, Asparagopsis armata, Antithamnionella elegans, Antithamnionella ternifolia, Codium fragile, Colpomenia peregrina, Caulerpa taxifolia, Dasysiphonia sp., Sargassum muticum, Undaria pinnatifida and Womersleyella setacea. A simulation model is constructed to show the validity of using historical data to reconstruct dispersal kernels. Lévy movement patterns similar to those previously observed in humans and wild animals are evident in the re-constructed dispersal pattern of invasive aquatic species. Such patterns may be widespread among invasive species and could be exacerbated by further development of trade networks, human travel and environmental change. These findings have implications for our ability to predict and manage future invasions, and improve our understanding of the potential for spread of organisms including infectious diseases, plant pests and genetically modified organisms.

Effects of Elodea nuttallii on temperate freshwater plants, microalgae and invertebrates: small differences between invaded and uninvaded areas

The invasive aquatic plant species Elodea nuttallii could pose a considerable risk to European freshwater ecosystems based on its current distribution, rate of spread and potential for high biomass. However, little research has been conducted on the impacts of this species on native biota. This study takes an ecosystem-wide approach and examines the impact of E. nuttallii on selected physicochemical parameters (dissolved oxygen and pH), algae, invertebrate and macrophyte communities. Elodea nuttallii had small but significant impacts on plant, invertebrate and algal species. The richness of algal periphyton was lower on E. nuttallii than on native macrophytes. The taxonomic composition of invertebrate communities associated with E. nuttallii differed from that associated with similar native plant species, but did not differ in terms of total biomass or species richness. Macrophyte species richness and total cover were positively correlated with percentage cover of E. nuttallii. Not all macrophyte species responded in the same way to E. nuttallii invasion; cover of the low-growing species, Elodea canadensis and charophytes were negatively correlated with E. nuttallii cover, whilst floating-rooted plants were positively correlated with E. nuttallii cover. All observed differences in the macrophyte community were small relative to other factors such as nutrient levels, inter-annual variation and differences between sites. Despite this, the observed negative association between E. nuttallii and charophytes is a key concern due to the rarity and endangered status of many charophyte species.

Some ecological effects of beaver upon the watersheds in the Porcupine Hills, Alberta /

This ecological investigation of the beaver (Castor canadensis canadensis Kuhl) was part of the Eastern Slopes (Alberta) Watershed Research program conducted during the summers of 1968 . 1969 . 1970. and 1971 . A soil particle size analysis indicated that soil heavy with clay was used by the beaver for construction purposes in the Porcupine Hills . Examples were given of the beaver controlling erosion with the construction of dams . and also causing erosion to occur . However . in general . the beaver slow down soil erosion and decrease the loss of soil from this region. The beaver utilized measureable amounts of herbaceous vegetation . However, the utilization of herbs by the beaver requires further investigation. A system of ex~sures and enclosures of herbaceous vegetation plots was used to study the utilization of sedges , grasses , and forbs . The beaver indicated stronger species preference for willow as compared to aspen . The size preference for willow was in the 1.0 to 10.0 centimeters basal diameter classes , while the beaver utilization of aspen indicated a preference for the largest trees with basal diameter greater than 20.0 centimeters. Willow was the most important plant in the low lying areas with regard to distribution, abundance and to produce sustained yield. The beaver used this plant for food and construction throughout the study area. The distribution of aspen was limited. and this species did not appear to produce more than one crop in the lifetime of a beaver colony. Nine out of 15 woody plant types were sampled by the beaver in this region. A plot-intercept transect technique was used for systematic vegetation sampling of the woody vegetation in six intensively studied watersheds. The beaver population of the Porcupine Hills region of SW-Alberta is believed to depend upon the chinooks. During the 1971 ground census, a total of 60 active beaver colonies were tallied on the 930 square kilometers large study area. The beaver of the region were not found to store large food caches during fall and winter, however, they are believed to collect feed periodically throughout the winter months. It was observed that the severe winter in 1968-69, reduced by 27 per cent the number of active beaver colonies within the study area. The Porcupine Hills region had 0.07 beaver colony per square kilometer in 1971, a low density of beaver colonies due to the rough topography of the area. However, the importance of the beaver ponds was somewhat clarified as they provide increased moisture, which lessens the fire damage, and store water for wildlife and cattle in the area. Meteorological data was collected by the author in collaboration with the Department of Transport.

Bill C-373 - First Reading, 24 January 1975

"An Act to provide for the recognition of the Beaver (Castor canadensis) as a symbol of the sovereignty of the Dominion of Canada." Mr. Sean O'Sullivan worked to have this Bill passed, recognizing the Beaver as a symbol of Canadian sovereignty.