Horses Grazing Management to Promote Distribution of \u3ci\u3eLotus tenuis\u3c/i\u3e (Waldst. et Kit) in a Temperate Grassland

In a temperate grassland of the Argentine Pampa, the birdsfoot trefoil (Lotus tenuis Waldst. et Kit) distribution was analyzed as a consequence of the grazing method used. In a plot of 40 ha occupied by native grassland an area of 16 ha was implanted with reed canary grass (Phalaris aquatica L.) and L. tenuis. This area was divided into two parts that contained the same pasture and native grassland surfaces, being grazed by horses. One, under continuous grazing and another one, under a controlled grazing. In the continuous grazing the whole year the animals had permanently access to the pasture and the native grassland. In the controlled grazing the pasture and the native grassland were alternated weekly. Floristic censuses were carried out and the plant cover was determined. At the beginning of the experience, October 1994, the pasture showed a homogeneous plant cover, 15% of L. tenuis and 30% of P. aquatica, meanwhile in the native grassland their presence was not registered. At the end of the experience, October 1998, under continuous grazing, in the pasture as well as in the native grassland, both species presented the same cover, 1%. On the contrary, the cover of the L. tenuis, 20% in the pasture and 10% in the native grassland, and of P. aquatica, 30% and 10% respectively, under controlled grazing were grater. The nutritive value and the forage availability of the native grassland were improved (3,584 kg.ha-1 of DM under controlled grazing versus 1,187 kg.ha-1 under continuous grazing)

Structure and Function Vegetation Conditions by Grazing Processes in a Humid Pampean Grassland (Argentina)

Expressed changes were evaluated as consequence of the cattle grazing, or their exclusion, in the structure of plant communities of the Flooding Pampa. We center our interest in the species numbers, plant cover, species diversity and forage availability. The treatments were: a) continuous grazing, b) enclosure grazing and c) controlled grazing. The enclosure grazing area was installed two years before starting the measurements. In the continuous grazing St. Augustine grass (Stenotaphrum secundatum Walt.) holds its initial cover of 64 % and dallis grass (Paspalum dilatatum Poir.) the 15 %. In the enclosure grazing S. secundatum decreased its cover up to 15 % and in the meanwhile P. dilatatum increased its cover up to 47 %. In controlled grazing S. secundatum decreased its cover up to 30 % while P. dilatatum increased its cover up to 47 %. The great availability of the forages established was concentrated in the compartment of the gramineous (continuos grazing: 1,576 kg.ha-1; controlled grazing: 1,852 kg.ha-1 and enclosure grazing: 4,785 kg.ha-1) and the biggest contribution was given by P. dilatatum. In the condition of this trial, with a prolonged enclosure grazing, the erect gramineous like P. dilatatum increased their plant cover displacing from the grassland those ones of creeping stoloniferous habits like S. secundatum. In the meanwhile the controlled grazing started to show legumes such as birdsfoot trefoil (Lotus tenuis Waldst. et Kit) which are lost with the continuous grazing

Hundreds of genetic barcodes of the species-rich hydroid superfamily Plumularioidea (Cnidaria, Medusozoa) provide a guide toward more reliable taxonomy

Marine hydroids are important benthic components of shallow and deep waters worldwide, but their taxonomy is controversial because diagnostic morphological characters to categorize taxa are limited. Their genetic relationships are also little investigated. We tested taxonomic hypotheses within the highly speciose superfamily Plumularioidea by integrating a classical morphological approach with DNA barcoding of the 16S and COI mitochondrial markers for 659 and 196 specimens of Plumularioidea, respectively. Adding Genbank sequences, we inferred systematic relationships among 1,114 plumularioids, corresponding to 123 nominal species and 17 novel morphospecies in five families of Plumularioidea. We found considerable inconsistencies in the systematics of nominal families, genera and species. The families Kirchenpaueriidae and Plumulariidae were polyphyletic and the Halopterididae paraphyletic. Most genera of Plumularioidea are not monophyletic. Species diversity is considerably underestimated. Within our study, at least 10% of the morphologically-distinctive morphospecies are undescribed, and about 40% of the overall species richness is represented by cryptic species. Convergent evolution and morphological plasticity therefore blur systematic relationships. Additionally, cryptic taxa occur frequently in sympatry or parapatry, complicating correspondence with type material of described species. Sometimes conspecificity of different morphotypes was found. The taxonomy of hydroids requires continued comprehensive revision.This work relied on several hydrozoan samples collected from various sites, with the aid of many people. Supplementary Table S1 refers many of the people involved in the collection and/or preservation of the samples. C.J.M. acknowledges his great buddy-divers Jaime N.-Ruiz (CIMAR, Univ. Costa Rica), Axel Calderon, Nathaniel Chu, Eleni Petrou (STRI, Smiths. Inst.), Hanae Spathias, Karen Koltes (at the Belize station, Smith. Inst.), Freya Sommer (Hopkins Marine Station), Remilson Ferreira ('Costa Norte', Sao Tome), Frederico Cardigos (DOP, Univ. Azores) and others that assisted the dives. C.J.M. also acknowledges Rita Castillo (CIMAR, Univ. Costa Rica), Plinio Gondola, Ligia Calderon, Laura Geyer, Maria Castillo (STRI, Smiths. Inst.), Gregory Ruiz (SERC, Smiths. Inst.), Paul Greenhall, William Keel (MSC, Smith. Inst.), Manuel Enes, Valentina Matos (IMAR/DOP, Univ. Azores), Filipe Porteiro, Joao Goncalves (OKEANOS/IMAR, Univ. Azores), Marina Cunha, Ascensao Ravara (CESAM, Univ. Aveiro), Shirley Pomponi (Harbor Branch, Florida Atlantic Univ.), Estrela Matilde (Fundacao Principe Trust), Monica Albuquerque, Ines Tojeira (EMEPC), Diana Carvalho (Nat. Mus. Nat. Hist., Lisbon) and many others colleagues that facilitated the morphologic classifications and deposition of the samples. Peter Schuchert (Mus. d'Hist. Nat. Geneve) kindly provided some DNA extractes. Todd Kincaid and his team of GUE divers (Project Baseline - Azores) collected valuable samples from unusual depths. Joana Boavida (CIIMAR, Univ. Algarve) facilitated some samples of the 'DeepReefs' project. Jim Drewery (Marine Scotland Science Inst.) also provided few samples. Dale Calder (Royal Ontario Museum) provided some bibliography to C.J.M. and discussed/resolved some dubios taxonomic classifications. Colleagues at the L.A.B. (NMNH, Smith. Inst.) were very supportive. The APC fees for open access publication were supported by a program of the Regional Government of the Azores ("Apoio ao funcionamento e gestao dos centros de I&D regionais: 2018 - DRCT-medida 1

Efectos de la roturación del suelo, durante el agregado de fosfato diamónico, sobre la estructura y el funcionamiento de un pastizal húmedo-alcalino de la Pampa Deprimida bonaerense (ºArgentina)

La roturación de los suelos halomórficos, con la finalidad de incorporar fosfato diamónico, provocaría el deterioro de la estructura y alteraciones en el funcionamiento de las comunidades vegetales. Desde 1987 a 1989 se evaluaron seis tratamientos: tres bajo pastoreo controlado y tres con exclusión al pastoreo. En ambas situaciones los tratamientos fueron roturados y fertilizados y sin roturar ni fertilizar. En los tratamientos donde se roturó con o sin fertilización disminuyeron la cobertura vegetal, el número de especies y la diversidad específica. Excepto en el área clausurada sin roturar ni fertilizar, se redujo la disponibilidad de forraje. Un año después, esa biomasa forrajera igualó a la alcanzada por aquel tratamiento. La roturación del suelo, durante el agregado del fertilizante, neutralizó el efecto benéfico del fosfato diamónico, por lo que no se registró un aumento de la disponibilidad forrajera total, ni se modificó la de leguminosas. La cobertura y la biomasa del pastizal se recuperaron al cabo de ocho meses. No así la estructura y el funcionamiento inicial del sistema, evidenciándose la pérdida de la riqueza florística y la disminución de la diversidad específica del pastizal

Distribución de raíces en pastizales naturales y pasturas cultivadas de La Pampa Deprimida Bonaerense y su relación con la biomasa forrajera

Para desarrollar modelos que permitan un adecuado manejo de la producción vegetal es necesario el estudio del crecimiento de las raíces como parte del funcionamiento del sistema productivo. Las posibilidades de distribución de las raíces en el suelo, sean éstas de una especie nativa o de una exótica, dependen de las resistencias mecánicas que encuentren para elongarse y sus comportamientos serían determinantes de las diferentes producciones de biomasa aérea entre un pastizal y una pastura cultivada. Los objetivos del presente estudio fueron determinar, en cada estación climática, las forrajimasas de un pastizal natural, compuesto principalmente por pelo de chancho (Distichlis scoparia Kunth y D. spicata L.) y pasto miel (Paspalum dilatatum Poir.), y de una pastura implantada, compuesta por agropiro alargado (Thinopyrum ponticum Podp.) y trébol blanco (Trifolium repens L.), y relacionarlas a la distribución de las raíces, en un suelo Natracualf de la Pampa Deprimida Bonaerense. La materia seca aérea del pastizal y la pastura se obtuvo cortando y secando, en ambas situaciones, 10 muestras rectangulares de 0,5 m2 distribuidas al azar. La densidad radical se estimó extrayendo muestras cilíndricas a 0-5; 5-15; 15-25 y 25-35 cm de profundidad, en las mismasestaciones de muestreo de la biomasa aérea. Se determinó una mayor biomasa aérea de la pastura de agropiro en invierno y en primavera, respecto al pastizal. Las diferencias se correspondieron con la mayor densidad de biomasa radical a 0-5 cm de profundidad. A diferencia de lo que ocurrió en lapastura, a medida que aumentó la profundidad, fue mayor la correlación encontrada entre la densidad radical y la forrajimasa del pastizal