Spatial Associations, Size–Distance Relationships and Population Structure of Two Dominant Life Forms in a Semiarid Enclave of the Venezuelan Andes

Larrea-Alcázar, Daniel M.; Soriano, Pascual J.

doi:10.1007/s11258-006-9118-3

Cited by 17 publications

(18 citation statements)

References 43 publications

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“…The columnar cactus Trichocereus atacamensis is know to be associated with Larrea divaricata, Prosopis ferox, and Aphyllocladus spartioides (de Viana et al 2001). It is generally accepted that columnar cacti (which were not observed in this study) usually need a nurse to recruit (Turner et al 1969;FloresMartínez et al 1994;Larrea-Alcázar and Soriano 2006). The pattern of distribution of other growth forms of Cactaceae observed in this study suggest both the existence of nurse associations as well as some recruitment in the open.…”

Section: Discussionmentioning

confidence: 47%

The role of nurse plants in the establishment of shrub seedlings in the semi-arid subtropical Andes

et al. 2007

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In the nurse plant syndrome, or nurse association, seedlings (beneficiaries) are associated with adult shrubs/trees (benefactors). This phenomenon has been documented in several regions of the planet. Abiotic stress amelioration (one mechanism of facilitation) is one of the causes of this association. Most of the studies addressing the nurse syndrome have been conducted on spatial scales of a few hectares and have focused on only one or a few species. Moreover, there is an almost complete lack of studies addressing the incidence and characteristics of the nurse phenomenon in the arid Andes of South America. We undertook a first approximation to the study of facilitation in these ecosystems. The study was conducted at local and regional scales and involved the assessment of the spatial distribution of juveniles (seedlings and saplings) of 51 populations of 16 shrub and 12 cactus species in relation to shrub cover at 20 localities of the Prepuna (subtropical Andes of Bolivia and Argentina, 20-26 degrees S). In terms of spatial distribution, the juveniles of most of the populations of shrubs studied were distributed both under the shrubs and in open spaces, thereby showing an apparent indifference to microhabitat. Globose and opuntioid cacti were preferentially distributed below the canopies of shrubs and were usually more associated with the dominant shrub species, which stood out as better potential nurses. The pattern was consistent throughout the region, including the more mesic and arid localities. The fact that Prepuna woody species are capable of establishing in open spaces would confer this region a greater resilience. Our findings further suggest that community dynamics in arid and semi-arid environments are more variable than previously thought.

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Section: Discussionmentioning

confidence: 47%

The role of nurse plants in the establishment of shrub seedlings in the semi-arid subtropical Andes

et al. 2007

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“…Although our data suggest that P. juliflora is a benefactor plant for the establishment of S. griseus, field assessment focused on isolated mimosoid shrubs also shows that individuals of S. griseus and C. repandus may be spatially associated to A. farnesiana (Larrea-Alcázar and Soriano 2006). This suggests isolated A. farnesiana individuals may also be important in determining spatial community structure and the establishment of columnar cacti.…”

Section: Discussioncontrasting

confidence: 53%

“…Benefactor plants (or species) can influence recruitment, growth and spatial associations of beneficiary species through a variety of pathways, both direct and indirect (Valiente-Banuet and Ezcurra 1991;Valiente-Banuet et al 1991a, 1991bArriaga et al 1993;de Viana 2001;Godínez-Á lvarez et al 2003). Nevertheless, there is little information on the occurrence of the nurse plant phenomenon in the Andean tropical semiarid environments (Larrea-Alcá-zar et al 2005;Larrea-Alcázar and Soriano 2006;). Moreover, few authors have examined if the occurrence of the nurse-plant phenomenon varies within a semidesert plant community which may exhibit different replicates from the same xerophyllous plant community (Pugnaire et al 1996;Pugnaire and Luque 2001;Tewksbury and Lloyd 2001;Tirado and Pugnaire 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The prevailing vegetative elements of these semi-arid valleys are thorny mimosoid shrubs and long-lived columnar cacti species, which cover a mosaic of cactus thickets and thornscrubs. The so-called ''nurse plant phenomenon'' and the effect of these mimosoid shrubs on spatial distribution of the columnar cacti has been demonstrated (Larrea-Alcázar and Soriano 2006). However, studies on local variations of cactishrub associations and comparative analysis between both habitats on a local scale are still absent in the Venezuelan Andes and variations in the importance of mimosoid species, as nurse plants for natural regeneration of columnar cacti have not been sufficiently probed.…”

Section: Introductionmentioning

confidence: 99%

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Columnar cacti-shrub relationships in an Andean semiarid valley in western Venezuela

Larrea-Alcázar

Soriano

2007

Plant Ecol

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Spatial associations between columnar cacti and mimosoid shrubs were evaluated in an Andean semidesert enclave. An analysis on the capacity of other deciduous shrub species and medium-sized ephemeral plants to modify the spatial distribution of cacti was also included. The number of Stenocereus griseus (Haw.) F. Buxb., Cereus repandus (L.) Backeb. and Pilosocereus tillianus Gruber & Schaftzl that grow below the canopies of perennial plants were assessed and compared with open areas. Comparison of observed and expected number of cactus individuals shows a positive spatial association between S. griseus and Prosopis juliflora DC. Moreover, abundance of C. repandus and P. tillianus under the canopies of mimosoid shrubs were not statistically different from what was expected by chance. Positive spatial association between S. griseus and Capparis odoratissima Jacq., Cassia emarginata L., Cordia curassavica (Jacq.) Roem. & Schult., Croton rhamnifolius H.B.K. and Jatropha gossypifolia L. was also found. Evidence suggests that positive columnar cacti-shrub spatial association may occur either in the cactus thickets or in the thornscrubs. Due to the clumped distributions of S. griseus beneath P. juliflora and other perennial plants, we here postulate that S. griseus is the primary nursed columnar cactus of the enclave. The presence of cacti in open areas suggests that facilitation may be less important for establishment of columnar cacti species in this Andean semidesert landscape than in other temperate and tropical semiarid zones. We here discuss the importance of the nurse syndrome phenomenon for recruitment of S. griseus and for the conservation of this Andean semiarid environment.

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“…water or temperature-limited regions) has been to study patterns in local spatial relationships, with spatial segregation suggesting net competitive effects, and spatial aggregation indicating net positive effects (e.g. Tirado and Pugnaire 2003;Kikvidze et al 2005;Larrea-Alcázar and Soriano 2006;Dullinger et al 2007;Llambí et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Shrubs as foundation species in a high tropical alpine ecosystem: a multi-scale analysis of plant spatial interactions

Cáceres

Llambí

Rada

2014

Plant Ecology & Diversity

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Background: Studies on plant-plant interactions in alpine ecosystems show a strong bias for temperate vs. tropical latitudes and pay limited attention to the implications of biophysical heterogeneity beyond the local plant scale. Aims: To evaluate the effects of a dominant shrub (Hypericum laricifolium) on community organisation, integrating multiple scales of analysis, in a high Andean páramo in Venezuela. Methods: We compared plant cover, species richness and Shannon diversity between plots placed under the shrub and outside (plant scale); quantified the spatial relations of Hypericum with its conspecifics, heterospecifics and rocks at different radial distances, using covariance functions (patch scale); analysed the effects of Hypericum shrubs on total species richness in the community (site scale); and evaluated the consistency of our results among four sites within the same region (between-site scale). Results: Average species richness, Shannon diversity, and the abundance of common forbs and conspecific shrubs were consistently higher inside the Hypericum shrub, while the exotic Rumex acetosella was more abundant in open areas. However, the aggregated spatial distribution of conspecifics and other species extended beyond the local plant scale and there were no clear effects of Hypericum shrubs on community-level species richness. Conclusions: Shrubs can function as foundation species in tropical alpine environments, modifying local community structure and alpha diversity, but not necessarily the species richness of the overall community. Our results stress the need of analysing multiple spatial scales to interpret the role of plant-plant interactions (facilitation/competition) in heterogeneous alpine ecosystems.

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Spatial Associations, Size–Distance Relationships and Population Structure of Two Dominant Life Forms in a Semiarid Enclave of the Venezuelan Andes

Cited by 17 publications

References 43 publications

The role of nurse plants in the establishment of shrub seedlings in the semi-arid subtropical Andes

The role of nurse plants in the establishment of shrub seedlings in the semi-arid subtropical Andes

Columnar cacti-shrub relationships in an Andean semiarid valley in western Venezuela

Shrubs as foundation species in a high tropical alpine ecosystem: a multi-scale analysis of plant spatial interactions

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