Seed Biology and Ecology of Natalgrass (Melinis repens)

Abstract

Natalgrass is an invasive species that has become increasingly problematic in natural areas in Florida and other subtropical and tropical regions around the world. Natalgrass is a prolific seed producer, but little information is available regarding its seed biology and ecology. Research was conducted to determine levels of seed dormancy and to examine the effects of light, temperature, pH, water stress, and depth of burial on natalgrass seed germination. In addition, seed persistence under field conditions was examined both on the soil surface and while buried. Seeds appeared to undergo afterripening. Seed germination was not light dependent and occurred from 15 to 35 C, with optimum germination occurring at 20 to 35 C. Germination occurred at pH levels of 6 and 8 and was affected by water stress; no germination was observed at osmotic potentials less than −0.2 MPa. Seeds emerged from depths of at least 5 cm. Under field conditions, germination was reduced after burial; however, burial lengths of 3 to 15 mo did not result in differences in germination levels. Seedling numbers from seed deposits on the soil surface were greatly reduced after 1 mo, and no seedling emergence was observed after 4 mo.

Biología del pasto rosado Melinis repens (Willd.) e implicaciones para su aprovechamiento o control

“…El pasto rosado fue introducido a Florida en Estados Unidos de América como planta ornamental en 1866 (4) ; aunque otro reporte de su arribo es en 1893 (5) . A partir del año de 1903, esta especie se introdujo al suroeste de Estados Unidos de América; y ahora es reportada como invasora, tanto en esta zona como en el norte de México (6) y naturalizada en los estados de Florida, Nuevo México y Arizona (7) .…”

“…Natal grass was introduced to Florida in the United States as an ornamental plant in 1866 (4) ; another report of its arrival is from 1893 (5) . Starting on 1903, this species was introduced to the Southeast of the United States; now it is reported as an invasive species, both in this area and in the North of Mexico (6) and as a naturalized plant in the states of Florida, New Mexico and Arizona (7) .…”

“…Además, esta especie se puede establecer en áreas recuperadas de minas de fosfato y en suelos recién cultivados; sin embargo, tiende a desaparecer al aumentar la acidez del suelo a niveles cercanos a pH 5 (4) . Por su amplia adaptabilidad, el pasto rosado se ha convertido en un componente and in Tamaulipas may well date from the 60s, assuming that probably it entered Mexico through this last State.…”

“…Natal grass may establish in different environments such as temperate and arid zones, low elevation deciduous forests, crop areas and next to highways (5,21) . In addition, this species may establish in areas recovered from phosphate mines and recently sowed soils; however, it tends to disappear when the soil's acidity increases to levels close to pH 5 (4) . Due to its wide adaptability, natal grass has become a common component in many vegetable communities, and it may potentially represent ecological problems similar to buffel grass (Cenchrus ciliare), which is also an African invasive species from warm regions.…”

“…Natal grass may produce 113.5 kg ha -1 of seed in its first year, when it behaves as a perennial plant (4) . At the central part of Mexico it was found a production of 112.8 to 206.5 kg ha -1 ; in addition, the high production was obtained in years with below average rainfall (20) .…”