Nurse effect of <i>Bolax gummifera</i> cushion plants in the alpine vegetation of the Chilean Patagonian Andes

Cavieres, Lohengrin A.; Arroyo, Mary T. K.; Peñaloza, Alejandro; Molina‐Montenegro, Marco A.; Torres, Cristián

doi:10.1111/j.1654-1103.2002.tb02081.x

Cited by 164 publications

(142 citation statements)

References 43 publications

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“…) or shelter from wind (Cavieres et al. ; le Roux & McGeoch , ). Therefore, stress gradients in alpine ecosystems have been proposed to be preferentially unrelated to resources (Maestre et al.…”

Section: Discussionmentioning

confidence: 99%

Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment

Anthelme

Buendia

Mazoyer

et al. 2011

J Vegetation Science

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International audienceQuestions : Does facilitation among plants increase with elevation in a humid tropical alpine system in which climatic and ecological conditions differ from other alpine environments? What mechanisms are involved in the interactions? Location : Volcano Antisana, Eastern Cordillera of the Ecuadorian Andes (00°28′S, 78°09′W). Methods : We selected the cushion-forming Azorella aretioides as a potential nurse plant along an altitudinal gradient (4400, 4550 and 4700 m) in the high tropical Andes. We quantified its effects on other plants at species and community levels by comparing the product vegetation cover × number of individuals of every vascular species found inside and outside 265 cushions, using the relative interaction index. We inferred potential mechanisms behind the interactions through analysis of microclimate, soil moisture and soil nutrient measurements inside and outside cushions. Results : Predictions of the stress gradient hypothesis (SGH) were corroborated at community level, with transition from competitive or neutral effects of A. aretioides at 4400 and 4550 m to facilitative effects at 4700 m. Strong species-specific effects were observed along the altitudinal gradient, with a substantial effect of local habitat disturbance on the outcome of plant-plant interactions. Surprisingly, cushions lowered air and soil temperatures and air humidity, which reduced at higher elevations. Facilitation appeared to be caused by higher soil moisture and nutrient content beneath cushions. Conclusions : Our data extend the framework of the SGH by corroborating it for the first time in a tropical alpine system. However, the mechanisms underlying plant-plant interactions differed from those generally reported from alpine environments, with facilitation varying according to resource-mediated stress (nutrients). It remains to be tested whether this is specific to tropical alpine systems

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Section: Discussionmentioning

confidence: 99%

Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment

Anthelme

Buendia

Mazoyer

et al. 2011

J Vegetation Science

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“…in the NE and SE transects), particularly at higher altitudes, providing evidence for a nurse effect. Indeed, other cushion plants in the same family (from the genera Azorella, Laretia and Bolax) are also known to act as nurse plants to other vascular species Cavieres et al 2002;Cavieres et al 2007;Molina-Montenegro et al 2000). Because Agrostis abundance and biomass are low on the soil at higher elevations, the grasses growing on Azorella represent the majority of the population.…”

Section: Discussionmentioning

confidence: 99%

“…Azorella facilitates the successful establishment of other species within its canopy (sensu e.g. Cavieres et al 2002)], which results from its capacity to ameliorate local environment conditions by buffering soil temperatures, reducing wind speed, enhancing soil nutrient levels and providing a stable and moist substrate (Hugo et al 2004;le Roux and McGeoch 2008c;le Roux et al 2005;McGeoch et al 2008;Nyakatya and McGeoch 2007).…”

Section: Study Speciesmentioning

confidence: 99%

Interaction intensity and importance along two stress gradients: adding shape to the stress-gradient hypothesis

2009

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The stress-gradient hypothesis (SGH) predicts that the community-wide prevalence of positive interactions, relative to negative interactions, is greater under more severe environmental conditions. Because the frequency of positive and negative interactions within a community is the aggregate of multiple pair-wise interactions, one approach to testing the SGH is to examine how pair-wise interactions vary along severity gradients. While the SGH suggests that the net outcome of an interaction should monotonically become more positive with increasing environmental severity, recent studies have suggested that the severity-interaction relationship (SIR) may rather be unimodal. We tested which of the proposed shapes of the SIR best fits the variation in the interaction between two species along two types of severity gradients on sub-Antarctic Marion Island. This was done by comparing the performance of the grass Agrostis magellanica in the presence and absence of the cushion plant Azorella selago, along both species' entire altitudinal ranges (transects spanning 4-8 km), and along a shorter (transect = 0.4 km) wind exposure gradient. Along the altitudinal transects the relative intensity, but not the absolute intensity or the importance, of the Azorella selago-Agrostis magellanica interaction increased with altitude, consistently forming a plateau-shaped SIR with a positive asymptote. Thus, while the performance of Agrostis magellanica was negatively affected by Azorella selago at low altitudes, the grass benefited from growing on the cushion plant under greater environmental severity. Along the wind exposure gradient the intensity of the interaction also became more positive with increasing environmental severity for most performance measures. This suggests that the switch from a net negative to a net positive interaction can occur across both short and long distances. Therefore, this study provides strong evidence for a plateau-shaped SIR, and confirms that the SIR is unimodal along the particular non-resource severity gradients of this study.

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“…With increasing habitat loss due to climate change, cushion plants can thus be a critical first step in assessing the responsiveness of a community to change. Cushions consistently increase species richness at the entire plant community level and can similarly increase biomass [24], [25]. Less frequently tested, cushion plants can also positively influence other taxa such as ladybird abundance in the Andes [26], [27].…”

Section: Introductionmentioning

confidence: 99%

The Alpine Cushion Plant Silene acaulis as Foundation Species: A Bug’s-Eye View to Facilitation and Microclimate

Molenda

Reid²,

Lortie³

2012

PLoS ONE

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Alpine ecosystems are important globally with high levels of endemic and rare species. Given that they will be highly impacted by climate change, understanding biotic factors that maintain diversity is critical. Silene acaulis is a common alpine nurse plant shown to positively influence the diversity and abundance of organisms–predominantly other plant species. The hypothesis that cushion or nurse plants in general are important to multiple trophic levels has been proposed but rarely tested. Alpine arthropod diversity is also largely understudied worldwide, and the plant-arthropod interactions reported are mostly negative, that is,. herbivory. Plant and arthropod diversity and abundance were sampled on S. acaulis and at paired adjacent microsites with other non-cushion forming vegetation present on Whistler Mountain, B.C., Canada to examine the relative trophic effects of cushion plants. Plant species richness and abundance but not Simpson’s diversity index was higher on cushion microsites relative to other vegetation. Arthropod richness, abundance, and diversity were all higher on cushion microsites relative to other vegetated sites. On a microclimatic scale, S. acaulis ameliorated stressful conditions for plants and invertebrates living inside it, but the highest levels of arthropod diversity were observed on cushions with tall plant growth. Hence, alpine cushion plants can be foundation species not only for other plant species but other trophic levels, and these impacts are expressed through both direct and indirect effects associated with altered environmental conditions and localized productivity. Whilst this case study tests a limited subset of the membership of alpine animal communities, it clearly demonstrates that cushion-forming plant species are an important consideration in understanding resilience to global changes for many organisms in addition to other plants.

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Nurse effect of Bolax gummifera cushion plants in the alpine vegetation of the Chilean Patagonian Andes

Cited by 164 publications

References 43 publications

Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment

Unexpected mechanisms sustain the stress gradient hypothesis in a tropical alpine environment

Interaction intensity and importance along two stress gradients: adding shape to the stress-gradient hypothesis

The Alpine Cushion Plant Silene acaulis as Foundation Species: A Bug’s-Eye View to Facilitation and Microclimate

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