Feral horses dung piles as potential invasion windows for alien plant species in natural grasslands |
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Authors: | Alejandro Loydi Sergio Martín Zalba |
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Institution: | (1) Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS)-CONICET, Universidad Nacional del Sur, Camino La Carrindanga Km. 7, 8000 Bahia Blanca, Buenos Aires, Argentina;(2) GEKKO-Grupo de Estudios en Conservación y Manejo, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000 Bahia Blanca, Buenos Aires, Argentina |
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Abstract: | Small scale disturbances could act as patches that provide sites for the colonization of competitively inferior species, promoting
the establishment of non-native species in some cases. We analyzed the vegetation associated with feral horse dung piles in
montane pampas grasslands in Mid-East Argentina and described the changes following their abandonment, evaluating whether
dung piles act as invasion windows, allowing the entrance of alien plant species. We estimated the portion of the study area
directly covered by horse manure and dung height was used to estimate the time elapsed after the abandonment of each pile.
Vegetation replacement on dung piles of different ages was assessed and compared with grassland controls using discriminant
analysis. We used regression analysis to look for changes in vegetation cover, species richness, species diversity and evenness
in response to height (age) of the dung piles, and principal component analyses (PCA) to identify groups of plants associated
with different successional stages. We compared cover of alien plant species on dung piles with grassland controls using one-way
ANOVA. On average, 2.5% of the study area was covered by horse dung. Total vegetation cover, species richness, diversity and
evenness increased after the piles were abandoned. Characteristic plant groups were associated with initial, middle and last
phases of the studied succession. Vegetation on the dung piles significantly differed from that in grassland controls and
two species were consistently associated with dung piles: the invasive Red Star Thistle, Centaurea calcitrapa, and a native grazing-intolerant grass, Nassella clarazii. Non-native species cover was also higher in dung piles than in control plots. Dung piles cover a significant portion of
grassland area in our study site, produce significant changes in the vegetation and are associated with some invasive alien
plants that could eventually colonize more pristine areas in the vicinity. On the other hand, they might represent refuges
for palatable species, since horses seem to avoid them for grazing. |
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Keywords: | Conservation Invasive alien species Natural grasslands Refuges Stud pile Manure |
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