Establishment of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients

The plant associations of the phytogeographic province of Tehuacán-Cuicatlán Valley are described and classified according to the species dominance and physiognomy based on field samplings of 500 m2. The altitudinal distribution of the associations was determined conducting 250 m2 samplings located every 100 m altitude in throughout five environmental gradients. A total of 29 plant associations were recognized including nine associations dominated by columnar cacti, four types of deciduous forests, three types of Izotal, and six type of shrublands. Mountainous arboreal vegetation includes five types of forests, as well as a Mountainous lzotal. The vegetation associated to aquatic environments along rivers and springs include Galery forests and "Tulares". The pronounced heterogeneity of Tehuacan-Cuicatlán Valley determines the diversity and the distribution of the vegetation associations.

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An individual-based forest model links canopy dynamics and shade tolerances along a soil moisture gradient

Royal Society Open Science ◽

10.1098/rsos.150589 ◽

2016 ◽

Vol 3 (2) ◽

pp. 150589 ◽

Cited By ~ 10

Author(s):

Jean Liénard ◽

Nikolay Strigul

Keyword(s):

Soil Moisture ◽

Multiple Scales ◽

Environmental Gradients ◽

Spatial Competition ◽

Climatic Changes ◽

Moisture Gradient ◽

The North ◽

Trade Offs ◽

Shade Tolerant Species ◽

Closed Canopy

Understanding how forested ecosystems respond to climatic changes is a challenging problem as forest self-organization occurs simultaneously across multiple scales. Here, we explore the hypothesis that soil water availability shapes above-ground competition and gap dynamics, and ultimately alters the dominance of shade tolerant and intolerant species along the moisture gradient. We adapt a spatially explicit individual-based model with simultaneous crown and root competitions. Simulations show that the transition from xeric to mesic soils is accompanied by an increase in shade-tolerant species similar to the patterns documented in the North American forests. This transition is accompanied by a change from water to sunlight competitions, and happens at three successive stages: (i) mostly water-limited parkland, (ii) simultaneously water- and sunlight-limited closed canopy forests featuring a very sparse understory, and (iii) mostly sunlight-limited forests with a populated understory. This pattern is caused by contrasting successional dynamics that favour either shade-tolerant or shade-intolerant species, depending on soil moisture and understory density. This work demonstrates that forest patterns along environmental gradients can emerge from spatial competition without physiological trade-offs between shade and growth tolerance. Mechanistic understanding of population processes involved in the forest–parkland–desert transition will improve our ability to explain species distributions and predict forest responses to climatic changes.

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EMPIRICAL SUPPORT FOR THE POSSIBLE APPLICATION OF MODIFIED ELLENBERG INDICES TO THE STUDY OF ENVIRONMENTAL GRADIENTS ON DYNAMIC IRISH WETLANDS— EVIDENCE FROM SKEALOGHAN TURLOUGH, COUNTY MAYO

Biology & Environment Proceedings of the Royal Irish Academy ◽

10.3318/bioe.2011.02 ◽

2011 ◽

Vol 111 (1) ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Christopher D. Williams ◽

Boudewijn Beltman ◽

James Moran ◽

Micheline Sheehy Skeffington ◽

Michael J. Gormally

Keyword(s):

Environmental Gradients ◽

Empirical Support ◽

County Mayo

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Drivers of diversity gradients of a highly mobile marine assemblage in a mesoscale seascape

Marine Ecology Progress Series ◽

10.3354/meps13264 ◽

2020 ◽

Vol 638 ◽

pp. 149-164

Author(s):

GM Svendsen ◽

M Ocampo Reinaldo ◽

MA Romero ◽

G Williams ◽

A Magurran ◽

...

Keyword(s):

Environmental Gradients ◽

Regression Tree ◽

Demersal Fish ◽

Open Ocean ◽

Shared Resources ◽

Thermal Front ◽

Boosted Regression Tree ◽

Diversity Gradients ◽

Α Diversity ◽

Bottom Depth

With the unprecedented rate of biodiversity change in the world today, understanding how diversity gradients are maintained at mesoscales is a key challenge. Drawing on information provided by 3 comprehensive fishery surveys (conducted in different years but in the same season and with the same sampling design), we used boosted regression tree (BRT) models in order to relate spatial patterns of α-diversity in a demersal fish assemblage to environmental variables in the San Matias Gulf (Patagonia, Argentina). We found that, over a 4 yr period, persistent diversity gradients of species richness and probability of an interspecific encounter (PIE) were shaped by 3 main environmental gradients: bottom depth, connectivity with the open ocean, and proximity to a thermal front. The 2 main patterns we observed were: a monotonic increase in PIE with proximity to fronts, which had a stronger effect at greater depths; and an increase in PIE when closer to the open ocean (a ‘bay effect’ pattern). The originality of this work resides on the identification of high-resolution gradients in local, demersal assemblages driven by static and dynamic environmental gradients in a mesoscale seascape. The maintenance of environmental gradients, specifically those associated with shared resources and connectivity with an open system, may be key to understanding community stability.

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