Comparative spatial distribution, size, biomass and growth rate of two varieties of bracken fern (Pteridium aquilinum L. Kuhn) in a neotropical montane habitat

Abstract

Comparative spatial distribution, size, biomass and growth rate of two varieties of bracken fern (Pteridium aquilinum L. Kuhn) in a neotropical montane habitat AbstractA comparative field study of caudatum and arachnoideum, the two Pteridium aquilinum varieties of the caudatum subspecies known to grow in the neotropics, was performed in a montane savanna habitat of the Venezuelan Andes that was affected by wildfire. Frond size, ramet density and spatial distribution, blade and rhizome biomass, and frond elongation and expansion rates were measured in separate, isolated stands each containing only one bracken variety and covering approximately the same area (,-~540 m2). In addition to clearly discernible morphological differences, caudatum and arachnoideum were found to possess distinct features: caudatum tends to develop open stands of relatively shorter blades of 76.6 4-0.89 cm(# -t-SE) of rachis length and lower ramet density (1.6 fronds m -2, max. = 7 fronds m -2) whereas arachnoideum grows into longer, more expanded fronds 124 -I-1.6 cm tall and significantly higher ramet density (5.1 fronds/m 2, max. = 14.6 fronds m-z). The sum of aerial and underground biomass was found to be notably larger for arachnoideum (8522 4-614 Kg/ha) than for caudatum (1929 4-131 Kg ha -1) in stands growing under the same habitat conditions. Therefore the spatial distribution of arachnoideum appeared considerably more compact than that of caudatum. Blade growth rates and development time were also very different. Newly emerged caudatum croziers developed into mature blades within 42 to 48 days following an inverse exponential curve whereas arachnoideum blades required 70 to 75 days to reach maturity following a linear development. All the above dissimilarities are interpreted as the hitherto unreported indication of diverging growth strategies of two cohabitant bracken varieties following fire.

Interference of Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) on the establishment of rainforest trees

“…is a weed widely distributed throughout the world (Page, 1976), and its harmful attributes are well known (Watt, 1940;Alonso-Amelot and Rodulfo-Baechler, 1996;Humphrey and Swaine, 1997). Pteridium produces a large frond and rhizome biomass, large accumulations of litter which can compete directly with other species, especially developing seedlings.…”

“…The underground rhizome structure is fire resistant and contains a large carbohydrate store and a large number of frond-producing buds (Watt, 1940;Glass, 1976;Glass and Bohm, 1969;Lowday and Marrs, 1992;Snow and Marrs, 1997;Marrs et al, 1998;Johnson 2001). Pteridium has been described as a typical aggressive inflammable pioneer species, occurring in burnt or deforested sites (Alonso-Amelot and Rodulfo-Baechler, 1996;Humphey and Swaine, 1997;Snow and Marrs, 1997). Moreover, Pteridium produces what may be allelopathic compounds affecting the establishment and growth of other plant species (Gliessman and Muller, 1978;den Ouden, 2000;Gliessman, 1976apud den Ouden, 2000Marrs and Watt, 2006).…”

Kinetics of the Natural Evolution of Hydrogen Cyanide in Plants in Neotropical Pteridium arachnoideum and its Ecological Significance

“…P. arachoideum grows in dense thickets in open areas affected by fire or cattle husbandry, and in natural grasslands in the Andes mountain range of western Venezuela. Plants can persist for many years without further human intervention (Alonso-Amelot and Rodulfo, 1996). Voucher specimens were collected and stored in the laboratory herbarium, and also sent to the New South Wales Botanical Gardens in Sydney, Australia (NSW 361276 (30-40 cm long) were cut at ground level, stored in plastic clip bags, and brought to the laboratory within 2 hr.…”

Bracken adaptation mechanisms and xenobiotic chemistry

“…This robust underground system, comprising up to 79.8% of the live biomass and 5648 ± 390 kg/hectare (arachnoideum) [6], is not only long-lived, lasting perhaps several hundred years, but also provides various advantages over seed-based plants of the early succession. It stores nutrients that become readily available for new frond growth that develop quickly earlier than other seedlings.…”

“…Among these are the N 3 of adenine bases of uncoiled DNA that form a covalent adduct (6). Adenine-dienone adducts have been shown to promote depurination by beta-elimination on the ribose nucleus and breackage of the phosphoribose polymer, leading to severe DNA disruption (Scheme 1) [14].…”