Etelänpartaheinä

Hyparrhenia rufa is a species of grass known by the common names jaraguá,^[3] jaraguá grass, and giant thatching grass.^[4] It is native to Africa and it is widespread in the world as a cultivated forage and fodder for livestock and a naturalized and sometimes invasive species.^[4]

Description

This is usually a perennial grass, but it sometimes grows as an annual,^[5] and it is variable in form.^[3] It usually forms dense tufts of stems from a short rhizome.^[6] The stems can be 30 centimeters to 3.5 meters tall.^[7] The leaf sheaths enclose the stem at intervals, making it appear banded.^[3] Flowering stems have sparse leaves,^[3] but grazing increases leaf production.^[8] The leaf blades are 30 to 60 centimeters long. The panicle is up to 80 centimeters long and is made up of many short, yellowish or red-tinged racemes all subtended by a narrow, reddish spathe a few centimeters long. The racemes are lined with pairs of spikelets, the red-haired fertile spikelets without stalks and the smaller sterile spikelets on stalks.^[5]

The rough-haired seeds are dispersed in the fur of animals,^[8] on the wind, and on vehicles and machinery such as graders.^[5]

Ecology

In its native range the grass grows in woodlands and seasonally flooded grasslands. It is also tolerant of drought and easily naturalizes in disturbed habitat sites.^[5]

Several species of leafcutter ants have been observed foraging on jaragua, including Atta capiguara and A. laevigata.^[9]

The grass is susceptible to the plant pathogenic nematodes Helicotylenchus pseudopaxilli, Pratylenchus brachyurus, and Longidorus laevicapitatus.^[8] It can also host the phytoplasma bacterium which causes stunting in Napier grass (Pennisetum purpureum), and its infection has been dubbed Hyparrhenia grass white leaf disease.^[10]

Feed

This grass is grown in pastures for grazing and is cut for fodder, including hay and silage. It is often used for grazing beef cattle, and it is also used to raise dairy cattle, sheep, and goats. It is not a very nutritious grass, so it is generally supplemented with legumes for nitrogen and molasses, citrus pulp, or bran for energy.^[6] One experimental supplement for goats is a mix of groundnut cake and wheat bran.^[11] Legumes that have been added as supplements include Cratylia argentea,^[12] Erythrina poeppigiana, Gliricidia sepium, and Leucaena leucocephala.^[6] The protein content and digestibility of the grass are lowest in the dry season.^[12]

As a weed

As a weed in Hawaii

Where it has been introduced into cultivation it has frequently taken hold in the local habitat, sometimes becoming an invasive component of the flora. On the Llanos of South America it has grown easily on the moist grasslands that resemble those of its original range.^[13] It was introduced to the region to feed animals because native grasses are more fibrous and less nutritious.^[14] Its ability to outcompete native grasses such as Trachypogon plumosus is thought to come from several factors, which may include higher rate of growth, photosynthesis and germination of seeds, more efficient use of water, and more resources channeled into leaf development. It better tolerates loss of foliage to herbivores.^[13] It commonly reproduces vegetatively, but it also produces large amounts of highly viable seed.^[8]

This grass is a pyrophyte, well adapted to habitat with an annual wildfire cycle. During the dry season it becomes very flammable.^[15] Wildfires in stands of native grasses are patchy and relatively limited. H. rufa forms dense monotypic stands of tall stems in the absence of grazing pressure, and these stands ignite easily, burn intensely, and spread fire into the surrounding forests. Not only does the grass make wildfire events more severe, but it increases in response to fire.^[16] Dry parts may be burned away, but living tissue near the ground is not harmed and resprouts immediately; fire damage to an established stand of the grass is "negligible".^[8]

Today this species occurs as a weed in most tropical regions. It can be found in North, Central, and South America, many Pacific Islands, Asia, parts of Africa outside its native range,^[5][6] and Australia.^[8]

Other uses

This tall grass can be used as thatching, as straw, and as pulp for making paper.^[3] In East Africa it is planted as a border grass to prevent erosion.^[10]

References

Hyparrhenia rufa (Nees) Stapf conocida popularmnete como jaraguá, es una hierba gramínea de la familia de las poáceas.

Descripción

Es una planta perenne a veces anual, macollada, que alcanza los 3 m de altura, resistente a la sequía, con tallos delgados a robustos de 3 a 25 dm de alto, con hojas de 3 a 6 dm de largo y de 2 – 8 mm de ancho. La espata de la panícula es de varios tamaños, con espátulas de 3 – 5 cm de largo, por lo general más cortas que los pedúnculos del racimo doble. Los racimos son color amarillo oscuro o rojizos, miden de 2 – 2,5 cm de largo, con 9 – 14 aristas por cada racimo y las espiguillas tienen de 3 – 5 cm de largo.

Hábitat

Ocupa el segundo lugar de importancia después del pasto gamba como forraje en Nigeria. En estado joven es valioso, pero baja su nivel nutritivo cuando florece. No persiste bajo pastoreo intenso, se establece por semilla o por divisiones de raíces.

Es originaria de África. Considerada una planta exótica, fue introducida accidentalmente en América por barcos de esclavos, y después naturalizada en algunos países como México, donde se puede encontrar formando manchones de pasto junto con pastos nativos.

Se cultiva ampliamente en África del Sur, Brasil, Centro y Sudamérica. Cultivada en México, Cuba, Nicaragua, Puerto Rico, Nigeria, Brasil, etc.

Cultivo

Si se siembra la semilla sin limpiar y con cáscara en una cama sobre el terreno puede durar hasta 2 años en establecerse. Pero si se prepara el terreno, se le fertiliza, se la descascara y se siembra en hileras, y con riego por aspersión, se le podría aprovechar a los 5 meses.

Principalmente es utilizado para pastoreo directo y algunas veces henificado. Principalmente se utiliza para su fertilización compuestos nitrogenados y fosforados, ya que el potasio no causa ningún aumento en la productividad. Para mantener a este pasto frondoso se recomienda un pastoreo frecuente y continuo, pero no a una altura menor de 30 cm.

Se utiliza para la producción de carne; una ha de pastura se considera adecuada para un novillo.

En México en 2 años los rendimientos de carne durante la temporada de lluvia fueron de 147 kg/ha por novillo, pastoreado con pasto sin fertilizar y de 205 kg/ha cuando se aplicaron 100 kg/ha de nitrógeno.

La semilla se colecta a mano de prados usados para forraje y pastoreo, la mejor distancia para siembras es en hileras de 50 a 60 cm. El tiempo entre la floración y la maduración de la semilla es de 35 días y la viabilidad de la semilla es de 14 meses a una temperatura de 10 °C y una humedad relativa muy baja.

Nombres comunes

• Inglés: giant thatching grass, jaragua grass (Source: World Econ Pl ).
• Afrikáans: geelaartamboekiegras.
• Alemán: braunes Deckgras, Jaraguagras.
• Portugués: capim-jaraguá, jaraguá.
• Español: yaragua, jaraguá.^[1]​

Sinonimia

• Trachypogon rufus Nees
• Andropogon rufus (Nees) Kunth
• Cymbopogon rufus (Nees) Rendle^[2]​

Referencias

Hyparrhenia rufa est une espèce d'herbes du genre Hyparrhenia. Cette graminée a des tiges atteignant 3 m de haut, se développe dans les régions tropicales avec une bonne pluviométrie et se présente sous forme de touffes.

Notes et références

O jaraguá (Hyparrhenia rufa (Ness)Stapf.) é uma gramínea forrageira perene, cespitosa, com um sistema radicular superficial. Vegeta bem desde o nível do mar até 1.800 m de altitude, principalmente em regiões onde a precipitação oscila entre 800 e 1.400 mm/ano. Apresenta crescimento bastante lento, alongando o caule muito tardiamente. Com até cerca de três meses de idade a gramínea não mostra qualquer indício visual de diferenciação morfológica, isto é, toda a planta se apresenta como sendo constituída somente por folhas, não permitindo a determinação de nós. A partir dessa idade começa a processar-se o alongamento dos entrenós, iniciando-se ao mesmo tempo, o aumento de concentração de lignina e fibra nas diversas partes da planta. É uma gramínea de crescimento de verão, tendo um crescimento inverno bastante reduzido. Quando em crescimento livre, pode atingir até 6 m de altura, incluindo as hastes florais. As hastes são muito resistentes, bastante lenhosas e lignificada após a floração. Folhas mais ou menos densas com 44 cm de comprimento, 2 cm de largura e 12 mm de espessura, longas e estreitas lígula grande de forma aproximadamente triangular, tendo nas ápices da base um tufo de pêlos muito comprido. Não forma rizomas nem estolões.^[1]

Etimologia

"Jaraguá" procede do tupi yara'wa.^[2]

Referências

Hyparrhenia rufa là một loài cỏ bản địa châu Phi, song đã du nhập đến nhiều nơi để làm thức ăn cho gia súc và có khi là loài xâm hại.^[3]

Mô tả

Đây thường là cây lâu năm, song tùy theo giống và dạng^[4] có thể là cây thường niên.^[5] Nó hay mọc thành bụi, túa ra từ một thân rễ.^[6]

Hạt cây được lan truyền nhờ lông thú,^[7] gió, hay những máy móc như máy san.^[5]

Sinh thái

Trong khu vực bản địa, loài này thường mọc trong rừng thưa và đồng cỏ ngập nước theo mùa. Nó chịu hạn tốt và dễ sống sót trong nhiều điều kiện tự nhiênn.^[5]

Nhiều loài kiến xén lá, gồm Atta capiguara và A. laevigata, được ghi nhận tỉa lá H. rufa.^[8]

Chúng thường mắc bệnh giun tròn Helicotylenchus pseudopaxilli, Pratylenchus brachyurus, và Longidorus laevicapitatus.^[7] Nó cũng là vật chủ trung gian của loại khuẩn phytoplasma gây còi cọc ở cỏ Napier (Pennisetum purpureum).^[9]

Chú thích

Liên kết

红苞茅（学名：Hyparrhenia rufa）为禾本科苞茅属下的一个种。

参考文献

扩展阅读

1. ^ Hyparrhenia rufa. Integrated Taxonomic Information System (ITIS).
2. ^ Hyparrhenia rufa. The Plant List.