Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas
Woody encroachment in savannas is a worldwide concern, and there is growing consensus that anthropogenic activities play a central role in changing tree – grass interactions. We evaluated the influence of livestock grazing and neighborhood interactions on seedling emergence and survival of the nativ...
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| Format: | info:ar-repo/semantics/artículo |
| Language: | Inglés |
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2018
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| Online Access: | https://www.sciencedirect.com/science/article/pii/S1439179114001303 http://hdl.handle.net/20.500.12123/2875 https://doi.org/10.1016/j.baae.2014.09.008 |
| _version_ | 1855035042619719680 |
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| author | Macias, Daniel Mazía, Noemí Jacobo, Elizabeth Juliana |
| author_browse | Jacobo, Elizabeth Juliana Macias, Daniel Mazía, Noemí |
| author_facet | Macias, Daniel Mazía, Noemí Jacobo, Elizabeth Juliana |
| author_sort | Macias, Daniel |
| collection | INTA Digital |
| description | Woody encroachment in savannas is a worldwide concern, and there is growing consensus that anthropogenic activities play a central role in changing tree – grass interactions. We evaluated the influence of livestock grazing and neighborhood interactions on seedling emergence and survival of the native tree Acacia caven in wet savannas of northeastern Argentina. We hypothesized that grazing and grass competition act as biotic barriers limiting tree recruitment, but the relative magnitude of such barriers differs according to grass patch type. In two consecutive years (cohort 1 and 2) we sowed seeds and transplanted seedlings of Acacia in two grass patch types (prostrate/palatable and tussock/unpalatable grasses) in both, grazed and ungrazed plots. Each grass patch type was further manipulated to create three levels of grass competition (unclipped control, above-ground biomass removal and total biomass removal).
Cattle grazing diminished seedling emergence of both cohorts and seedling survival of cohort 1. The effect of grass competition changed according to grass patch type. Prostrate grass cover enhanced emergence but lowered early survival, while tussock grass cover and also its total biomass removal facilitated early survival. During the second year, a severe drought drastically reduced Acacia recruitment, and it was strong enough to eliminate any grazing effects although the effect of grass competition on seedling establishment remained significant.
Our results suggest that grazing and grass competition additively diminished the risk of woody establishment in this wet savanna. However, the stocking rate should be carefully balanced, thus contributing to the maintenance of a competitive grass cover to limit tree recruitment. |
| format | info:ar-repo/semantics/artículo |
| id | INTA2875 |
| institution | Instituto Nacional de Tecnología Agropecuaria (INTA -Argentina) |
| language | Inglés |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| record_format | dspace |
| spelling | INTA28752019-06-13T15:32:07Z Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas Macias, Daniel Mazía, Noemí Jacobo, Elizabeth Juliana Pastoreo Plantas Leñosas Invasión Sabanas Zona Subtropical Grazing Woody Plants Encroachment Savannas Subtropical Zones Woody encroachment in savannas is a worldwide concern, and there is growing consensus that anthropogenic activities play a central role in changing tree – grass interactions. We evaluated the influence of livestock grazing and neighborhood interactions on seedling emergence and survival of the native tree Acacia caven in wet savannas of northeastern Argentina. We hypothesized that grazing and grass competition act as biotic barriers limiting tree recruitment, but the relative magnitude of such barriers differs according to grass patch type. In two consecutive years (cohort 1 and 2) we sowed seeds and transplanted seedlings of Acacia in two grass patch types (prostrate/palatable and tussock/unpalatable grasses) in both, grazed and ungrazed plots. Each grass patch type was further manipulated to create three levels of grass competition (unclipped control, above-ground biomass removal and total biomass removal). Cattle grazing diminished seedling emergence of both cohorts and seedling survival of cohort 1. The effect of grass competition changed according to grass patch type. Prostrate grass cover enhanced emergence but lowered early survival, while tussock grass cover and also its total biomass removal facilitated early survival. During the second year, a severe drought drastically reduced Acacia recruitment, and it was strong enough to eliminate any grazing effects although the effect of grass competition on seedling establishment remained significant. Our results suggest that grazing and grass competition additively diminished the risk of woody establishment in this wet savanna. However, the stocking rate should be carefully balanced, thus contributing to the maintenance of a competitive grass cover to limit tree recruitment. Das Vordringen von Gehölzen in Savannen wird weltweit mit Besorgnis registriert, und es gibt eine zunehmende Übereinstimmung, dass menschliche Aktivität eine zentrale Rolle bei der Veränderung von Baum-Gras-Interaktionen spielt. Wir ermittelten den Einfluss von Beweidung durch Vieh und Nachbarschaftsinteraktionen auf das Auftreten von Sämlingen und das Überleben der einheimischen Baumart Acacia caven in Feuchtsavannen im nordöstlichen Argentinien. Wir erwarteten, dass Beweidung und Konkurrenz von Gräsern als biotische Barrieren fungieren, die den Aufwuchs von Bäumen limitieren, aber das relative Ausmaß dieser Barrieren sollte mit dem Grastyp variieren. In zwei aufeinander folgenden Jahren (Kohorten 1 und 2) säten wir Akazien-Samen und verpflanzten Jungpflanzen in zwei unterschiedlichen Grasbeständen (niederliegend/genießbar und horstartig/ungenießbar), jeweils mit und ohne Beweidung. Alle Grastypen wurden desweiteren manipuliert, um drei Stufen von Konkurrenz durch Gräser herzustellen: unbehandelte Kontrolle, Erntfernung der oberirdischen Grasbiomasse, Entfernung der gesamten Biomasse. Die Beweidung durch Rinder verminderte das Auftreten von Sämlingen in beiden Kohorten und das Überleben der Sämling in Kohorte 1. Der Einfluss der Konkurrenz durch Gräser variierte mit dem Grastyp. Niederliegendes Gras begünstigte das Auftreten von Keimlingen, verringerte aber das frühe Überleben, während Horstgräser aber auch ihre vollständige Entfernung das frühe Überleben begünstigten. Im zweiten Jahr reduzierte eine strenge Dürreperiode den Nachwuchs der Akazien, und sie war stark genug, Beweidungseffekte zu eliminieren, obwohl der Effekt der Konkurrenz durch Gräser signifikant blieb. Unsere Ergebnisse legen nahe, dass Beweidung und Konkurrenz durch Gräser zusammengenommen das Risiko einer Verwaldung in dieser Feuchtsavanne verringerten. Indessen sollte die Besatzdichte mit Vieh sorgfältig ausbalanciert werden, so dass eine wettbewerbsfähige Grasbedeckung erhalten bleibt, um die Rekrutierung von Bäumen einzugrenzen. EEA Mercedes Fil: Macias, Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Mercedes; Argentina Fil: Mazía, Noemí. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina Fil: Jacobo, Elizabeth. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina 2018-07-25T14:49:53Z 2018-07-25T14:49:53Z 2014-12 info:ar-repo/semantics/artículo info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion https://www.sciencedirect.com/science/article/pii/S1439179114001303 http://hdl.handle.net/20.500.12123/2875 1439-1791 https://doi.org/10.1016/j.baae.2014.09.008 eng info:eu-repo/semantics/restrictedAccess application/pdf Basic and Applied Ecology 15 (8) : 661-668 (December 2014) |
| spellingShingle | Pastoreo Plantas Leñosas Invasión Sabanas Zona Subtropical Grazing Woody Plants Encroachment Savannas Subtropical Zones Macias, Daniel Mazía, Noemí Jacobo, Elizabeth Juliana Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title | Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title_full | Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title_fullStr | Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title_full_unstemmed | Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title_short | Grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| title_sort | grazing and neighborhood interactions limit woody encroachment in wet subtropical savannas |
| topic | Pastoreo Plantas Leñosas Invasión Sabanas Zona Subtropical Grazing Woody Plants Encroachment Savannas Subtropical Zones |
| url | https://www.sciencedirect.com/science/article/pii/S1439179114001303 http://hdl.handle.net/20.500.12123/2875 https://doi.org/10.1016/j.baae.2014.09.008 |
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