Wyniki wyszukiwania

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Distribution of the nurse species Pycnophyllum molle J.Remy and P. weberbaueri Muschl. in the Andean dry puna (Arequipa district - Southern Peru): role of topographic-soil variability and disturbance regime

100%

Catorci A., Piermarteri K., Tardella F. M.

Polish Journal of Ecology

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2014

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tom 62

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nr 2

The dry Puna is the widest pastoral ecosystem of the tropical alpine Andes, characterized by harsh environmental conditions (long and intense drought stress periods and unfertile soils) and grazed by wild and domestic camelids. In these conditions, facilitation is of key importance in plant diversity conservation. Indeed, facilitation is a positive plant-plant interaction by which the so called nurse species provide environmental amelioration of harsh conditions and/or refuge to other plants (beneficiary species), which otherwise might fail to establish. The research aims were to understand which ecological variables affect the distribution of the potential nurse cushion species Pycnophyllum molle J. Rémy and P. weberbaueri Muschl., and if these species are affected by grazing disturbance. The study area (4000–4900 m a.s.l.) is located in the southern Peruvian Andes. Data of species cover, topographic and soil features, besides type of disturbance were collected along transects. We used canonical redundancy analysis to understand the relations between the cover of the two Pycnophyllum species and the above mentioned constraining variables. Results indicate that both the Pycnophyllum species grow on sandy loam, moderately acid soils, with low organic matter and very poor nitrogen content, and avoid high disturbance intensities. P. molle is more sensitive than P. weberbaueri to disturbance, and grows on relatively more fertile soils, also at higher altitudes and on steeper slopes characterized by greater rockiness.

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Criteria to distinguish between periglacial, proglacial and paraglacial environments

100%

Slaymaker O.

Quaestiones Geographicae

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2011

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tom 30

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nr 1

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Functional differentiation of Central Apennine grasslands under mowing and grazing disturbance regimes

80%

Catorci A., Ottaviani G., Ballelli S., Cesaretti S.

Polish Journal of Ecology

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2011

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tom 59

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nr 1

This research dealt to two grasslands potentially developing the same vegetation type because sited in the same environmental contest (bioclimate, substratum, soil, slope, altitude) but under diverse management regimes (grazing and mowing) for many decades. The evidenced differentiation between the two pastoral vegetations can be attributed to disturbance type and the statistical functional analysis performed through seven plant traits (prostrate form, early flowering, storage organs, clonal ability, basal meristems, chemical defences and hairs), revealed the distinguishing patterns. Discriminant analysis pointed out typical biological attributes for each disturbance conditions, while from correlation analysis emerged different possible traits combinations which do not follow the previous traits separation. Such outcomes are explainable because both grazing and mowing provoke aboveground phytomass removal, although grazing is a selective pressure, while mowing gives to all the species the same development chances. It is reasonable to conclude that convergent strategies within the two systems are possible and frequent.

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Ecotones of riverine ecosystems: Role and typology, spatio-temporal dynamics, and river regulation

80%

Ward J. V., Wiens J. A.

International Journal of Ecohydrology and Hydrobiology

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2001

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tom 01

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nr 1-2

Natural riverine ecosystems are characterized by a high level of heterogeneity manifest across a range of spatio-temporal scales. Ecotonal habitats are both the result of and contributors to the spatio-temporal dynamics of riverine ecosystems. Natural disturbances play an important rôle in maintaining a diversity of ecotonal habitats. A typology of riverine ecotones is developed that provides an expansive perspective scaled along four dimensions (longitudinal, lateral, vertical, and temporal) and that encompasses environmental gradients and boundaries as well as distinct transition zones between adjacent patches. From this broad perspective it is apparent that riverine ecotones play important rôles relating to speciation, evolutionary invasion of fresh waters, biodiversity, bioproduction, and ecological connectivity. River regulation disrupts the natural disturbance regime downstream, thereby reducing the diversity of ecotonal habitats and their connectivity with the main river channel. The altered rôle of ecotonal habitats induced by regulation is especially pronounced in alluvial floodplaing rivers, which are characterized by a mosaic of habitat patches that collectively occupy a wide range of successional stages. Downstream hydrologic changes, such as truncated sediment transport and reductions in the frequency and intensity of flooding, typically lead to altered successional trajectories, desiccated floodplain waterbodies, severed migration pathways, and reduced exchange rates of nutrients and organic detritus across ecotone boundaries. Effective management of regulated rivers should focus on maintaining or restoring the important rôles of ecotones by re-establishing interactive pathways and by reconstituting a disturbance regime that leads to a diversity of habitat patches and successional stages.

Ograniczanie wyników

2 Polish Journal of Ecology

1 International Journal of Ecohydrology and Hydrobiology

1 Quaestiones Geographicae

2 Catorci A.

1 Ballelli S.

1 Cesaretti S.

1 Ottaviani G.

1 Piermarteri K.

1 Slaymaker O.

1 Tardella F. M.

1 Ward J. V.

1 Wiens J. A.

1 2014

2 2011

1 2001

Distribution of the nurse species Pycnophyllum molle J.Remy and P. weberbaueri Muschl. in the Andean dry puna (Arequipa district - Southern Peru): role of topographic-soil variability and disturbance regime

Criteria to distinguish between periglacial, proglacial and paraglacial environments

Functional differentiation of Central Apennine grasslands under mowing and grazing disturbance regimes

Ecotones of riverine ecosystems: Role and typology, spatio-temporal dynamics, and river regulation