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Christopher J Lortie - One of the best experts on this subject based on the ideXlab platform.
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A systematic review dataset describing the studies of positive interactions and the niche in deserts.
2018Co-Authors: Christopher J Lortie, Alessandro Filazzola, Diego SotomayorAbstract:To synthesize the breadth of concepts and approaches used to concurrently study niche and positive Plant interactions in deserts, we conducted a formalized systematic review. in early 2018, we conducted a search of the peer-reviewed literature using the Web of Science with the following terms: “niche“ AND (“Plant facilitat*” OR “Nurse Plant” OR “positive interact*) AND (“arid” OR “desert”). After removing duplicates, the following data were extracted to categorize the studies. The code and full list of studies are provided on GitHub: https://cjlortie.github.io/desert.niche.facilitation
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a systematic review and conceptual framework for the mechanistic pathways of Nurse Plants
Global Ecology and Biogeography, 2014Co-Authors: Alessandro Filazzola, Christopher J LortieAbstract:Aim To conceptualize the mechanistic pathways of the Nurse-Plant syndrome by life-form and to identify the implications of positive Plant–Plant interactions for landscape and evolutionary ecology. Location Global. Methods We conducted a quantitative review examining 298 articles to categorize the literature on Nurse-Plant interactions based on geographic region, mechanism of facilitation, ecological hypothesis and Nurse life-form. Results A total of nine different Nurse mechanisms were identified and two were classified as meta-mechanisms. We found that shrubs were the dominant Nurse life-form (46% of total studies) and that studies of positive Plant interactions were most frequent in areas of high abiotic stress. Nurse-Plant studies were also distributed unevenly around the globe with nearly a quarter in the South American Andes and Spain. Studies testing the direct Nurse–protege interactions were the most frequently performed, including the ecophysiological responses of protege species (32.2%). Research gaps identified in the Nurse-Plant literature included indirect interactions and seed trapping as well as the large-scale implications for landscape ecology and evolution. Main conclusions Nurse Plants are often considered keystone species because they commonly structure Plant communities. This is an important confirmatory finding in many respects, but it is also novel in that it challenges traditional Plant ecology theory and has important implications for landscape-level dynamics over time. The categorization of mechanisms proposed provides a conceptual framework useful for organizing the research to date and can accelerate linkages with theory and application by identifying important connections. It is becoming increasingly apparent that future studies of the Nurse-Plant syndrome must decouple and consider multiple mechanisms of interaction to explain the processes that influence community structure, particularly in high-stress conditions, given a changing climate and potential shifts in biodiversity.
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Nurse Plant effects on the seed biology and germination of desert annuals
Austral Ecology, 2014Co-Authors: Diego A. Sotomayor, Christopher J Lortie, Laurent J. LamarqueAbstract:Nurse-Plants generally have positive effects on understorey species by creating more suitable conditions for stress-intolerant Plants relative to open micro-habitats. However, long-term effects of this Plant-Plant facilitation system have been rarely examined. Seeds of five desert annual species from Atiquipa coastal desert in Southern Peru were used to examine whether different microenvironmental conditions under the Nurse-Plants Caesalpinia spinosa Molina (Kuntze) lead to differences in seed biology and germinability of annual Plants relative to open, canopy-free conditions. Seeds collected from Plants associated with Nurse-Plants were predicted to be (i) larger due to more favourable growing conditions, (ii) more viable and with greater germination rates, (iii) less variable in size and viability due to reduced environmental heterogeneity, and (iv) to germinate faster to avoid apparent competition with other annuals. Seed attribute measurements and germination trials in growth chambers were used to test these predictions. Although the Plant abundance of only 2 of 5 species was strongly facilitated by the Nurse-Plant, no significant differences were found in seed mass, viability or relative variability between understorey and open micro-habitats for any of the species. Contrary to our predictions, final seed germination rates of seeds from open micro-habitats were higher, and the open micro-habitat treatment was more favourable for germination of seeds from both open and understorey environments. Taken together, these results suggest that Plant-Plant facilitation does not necessarily affect seed biology traits. Further studies addressing larger distribution ranges and/or density gradients of understorey species will illuminate the potential evolutionary effects of Nurse-Plants.
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Nurse‐Plant effects on the seed biology and germination of desert annuals
Austral Ecology, 2014Co-Authors: Diego A. Sotomayor, Christopher J Lortie, Laurent J. LamarqueAbstract:Nurse-Plants generally have positive effects on understorey species by creating more suitable conditions for stress-intolerant Plants relative to open micro-habitats. However, long-term effects of this Plant-Plant facilitation system have been rarely examined. Seeds of five desert annual species from Atiquipa coastal desert in Southern Peru were used to examine whether different microenvironmental conditions under the Nurse-Plants Caesalpinia spinosa Molina (Kuntze) lead to differences in seed biology and germinability of annual Plants relative to open, canopy-free conditions. Seeds collected from Plants associated with Nurse-Plants were predicted to be (i) larger due to more favourable growing conditions, (ii) more viable and with greater germination rates, (iii) less variable in size and viability due to reduced environmental heterogeneity, and (iv) to germinate faster to avoid apparent competition with other annuals. Seed attribute measurements and germination trials in growth chambers were used to test these predictions. Although the Plant abundance of only 2 of 5 species was strongly facilitated by the Nurse-Plant, no significant differences were found in seed mass, viability or relative variability between understorey and open micro-habitats for any of the species. Contrary to our predictions, final seed germination rates of seeds from open micro-habitats were higher, and the open micro-habitat treatment was more favourable for germination of seeds from both open and understorey environments. Taken together, these results suggest that Plant-Plant facilitation does not necessarily affect seed biology traits. Further studies addressing larger distribution ranges and/or density gradients of understorey species will illuminate the potential evolutionary effects of Nurse-Plants.
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A global meta-analytic contrast of cushion-Plant effects on Plants and on arthropods
PeerJ, 2014Co-Authors: Amanda R. Liczner, Christopher J LortieAbstract:Nurse Plant facilitation is a commonly reported Plant–Plant interaction and is an important factor influencing community structure in stressful environments. Cushion Plants are an example of alpine Nurse Plants that modify microclimatic conditions within their canopies to create favourable environments for other Plants. In this meta-analysis, the facilitative effects of cushion Plants was expanded from previous syntheses of the topic and the relative strength of facilitation for other Plants and for arthropods were compared globally.The abundance, diversity, and species presence/absence effect size estimates were tested as Plant responses to Nurse Plants and a composite measure was tested for arthropods. The strength of facilitation was on average three times greater for arthropods relative to all Plant responses to cushions. Plant species presence, i.e., frequency of occurrence, was not enhanced by Nurse-Plants. Cushion Plants nonetheless acted as Nurse Plants for both Plants and arthropods in most alpine contexts globally, and although responses by other Plant species currently dominate the facilitation literature, preliminary synthesis of the evidence suggests that the potential impacts of Nurses may be even greater for other trophic levels.
Francisco I Pugnaire - One of the best experts on this subject based on the ideXlab platform.
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Facilitation mediates species presence beyond their environmental optimum
Perspectives in Plant Ecology Evolution and Systematics, 2019Co-Authors: Michael O'brien, Luis Fernando Tavares De Menezes, Kari Anne Bråthen, Gianalberto Losapio, Francisco I PugnaireAbstract:Abstract Species distributions are driven by abiotic conditions that filter species with specific traits and physiological tolerances and match them with their suitable environment. Plant–Plant interactions can constrict (through competition) or loosen (through facilitation) the strength of these environmental filters, which in turn inhibit or enhance establishment and recruitment of Plant species at a finer spatial scale. Although competition is often the focus of community assembly processes that further impede the entry of Plant species into a site, facilitation is also important for potentially loosening environmental filters (especially climatic filters such as temperature and precipitation), ultimately enhancing species occurrence beyond their physiological optimum. We used multiple data sets from the arid site of Rambla del Saltador Valley to test the hypothesis that facilitation by a Nurse-Plant promotes the presence of herbaceous, beneficiary species beyond their environmental optimum relative to open sites. Furthermore, we propose that the median elevation and community composition of herbaceous species expands with the age of the Nurse-Plant, and we tested this hypothesis by examining 105 beneficiary species under 50 Nurse-Plant shrubs varying in age from 6 to 48 years old. We found Nurse-Plants both facilitate herbaceous species occurrence beyond their median elevation and support more diverse and a distinctly different composition of species in contrast to open sites. Specifically, herbaceous species that originate from a median elevation more than 600 to 700 m above the site only existed beneath Nurse-Plants, and below this median elevation, half the species only occurred below the Nurse-Plant. Moreover, the richness and elevation provenance of the herbaceous species increased with increasing Nurse-Plant age. Our results highlight the importance of facilitation for alleviating physiological strain (in support of the strain hypothesis) and mediating regional species distributions, which has implications for understanding species movements and community assembly at larger-scales under hotter and drier climates.
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Plant life history stage and Nurse age change the development of ecological networks in an arid ecosystem
Oikos, 2018Co-Authors: Christian Schöb, Gianalberto Losapio, Francisco I Pugnaire, Michael ObrienAbstract:Understanding how ecological networks are organised over the course of an organism’s lifetime is crucial for predicting the dynamics of interacting populations and communities across temporal scales. However, most studies so far considered only one life history stage at a time, such as adult, when studying networks of interacting species. Therefore, knowledge about how multiple life history stages affect the development and stability of Plant–Plant association networks is lacking. We measured the understory adult Plant community and the soil seed bank across a Plant age gradient of the Nurse shrub Retama sphaerocarpa in an arid ecosystem in Spain. Using a multilayer network approach, we built adult understory–Nurse and seed bank–Nurse networks and analysed how network nestedness, species’ role, and species specificity varied between them and with Nurse Plant age. We found that seed bank and adult understory networks changed depending on Nurse Plant age in two different ways. With increasing Nurse Plant age, adult understory networks became significantly more nested than seed bank networks. The nested architecture of seed bank networks was therefore a poor predictor of adult understory network nestedness. The contribution and specificity of species to network nestedness increased with increasing Nurse Plant age more in the adult understory than in seed bank networks, despite high species turnover. Our data show that life history and ontogeny affect the development of Plant–Plant association networks. Niche construction and environmental filtering along Nurse ontogeny seem pivotal mechanisms structuring adult understory networks while the assembly of seed bank networks seems rather stochastic. We highlight the importance of mature Plant communities for maintaining rare species populations and supporting the stability of ecological communities through time.
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The shift from Plant–Plant facilitation to competition under severe water deficit is spatially explicit
Ecology and Evolution, 2017Co-Authors: Michael O'brien, Susana Rodríguez-echeverría, Cristina Armas, Francisco I Pugnaire, Christian SchöbAbstract:The stress-gradient hypothesis predicts a higher frequency of facilitative interactions as resource limitation increases. Under severe resource limitation, it has been suggested that facilitation may revert to competition, and identifying the presence as well as determining the magnitude of this shift is important for predicting the effect of climate change on biodiversity and Plant community dynamics. In this study, we perform a meta-analysis to compare temporal differences of species diversity and productivity under a Nurse Plant (Retama sphaerocarpa) with varying annual rainfall quantity to test the effect of water limitation on facilitation. Furthermore, we assess spatial differences in the herbaceous community under Nurse Plants in situ during a year with below-average rainfall. We found evidence that severe rainfall deficit reduced species diversity and Plant productivity under Nurse Plants relative to open areas. Our results indicate that the switch from facilitation to competition in response to rainfall quantity is nonlinear. The magnitude of this switch depended on the aspect around the Nurse Plant. Hotter south aspects under Nurse Plants resulted in negative effects on beneficiary species, while the north aspect still showed facilitation. Combined, these results emphasize the importance of spatial heterogeneity under Nurse Plants for mediating species loss under reduced precipitation, as predicted by future climate change scenarios. However, the decreased water availability expected under climate change will likely reduce overall facilitation and limit the role of Nurse Plants as refugia, amplifying biodiversity loss.
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Facilitative Plant interactions and climate simultaneously drive alpine Plant diversity
Ecology Letters, 2014Co-Authors: Lohengrin A. Cavieres, Bradley J. Cook, Richard Michalet, Bradley J. Butterfield, Rob W Brooker, Christopher J Lortie, Christian Schöb, Francisco I Pugnaire, Zaal Kikvidze, Sa XiaoAbstract:Interactions among species determine local-scale diversity, but local interactions are thought to have minor effects at larger scales. However, quantitative comparisons of the importance of biotic interactions relative to other drivers are rarely made at larger scales. Using a data set spanning 78 sites and five continents, we assessed the relative importance of biotic interactions and climate in determining Plant diversity in alpine ecosystems dominated by Nurse-Plant cushion species. Climate variables related with water balance showed the highest correlation with richness at the global scale. Strikingly, although the effect of cushion species on diversity was lower than that of climate, its contribution was still substantial. In particular, cushion species enhanced species richness more in systems with inherently impoverished local diversity. Nurse species appear to act as a ‘safety net’ sustaining diversity under harsh conditions, demonstrating that climate and species interactions should be integrated when predicting future biodiversity effects of climate change.
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soil microbial community under a Nurse Plant species changes in composition biomass and activity as the Nurse grows
Soil Biology & Biochemistry, 2013Co-Authors: Sara Hortal, Yudi M Lozano, Cristina Armas, Felipe Bastida, Jose L Moreno, C Garcia, Francisco I PugnaireAbstract:Abstract Shrubs in semiarid ecosystems facilitate the establishment of other Plant species under their canopies and promote changes in the understory Plant communities as they grow. To better understand whether Plant community dynamics are linked to changes in soil microbes, we characterized soil microbial communities in gaps (open spaces) and under Retama sphaerocarpa shrubs of three different size classes. Different methodological approaches including pyrosequencing of 16S rDNA, phospholipid-fatty acid (PLFA) analysis and microbial activity indicators were combined to characterize both the structure and function of soil microbial communities in the different treatments. Soil microbial communities under small shrubs showed higher microbial biomass and activity, as well as different relative abundance of several bacterial groups, than communities in gaps. Shrubs were associated with a higher relative abundance of Bacteroidetes , Betaproteobacteria and Gammaproteobacteria in detriment of Actinobacteria and Firmicutes without changes in overall bacterial diversity. Soil microbial community changed with shrub size, being most different in gaps and under the canopy of large shrubs. We suggest that changes in composition and function of soil microbial communities may promote the increase in the understory Plant growth and species richness previously reported for this shrub species. Our data emphasize the importance of Plant–soil interactions in defining the structure and composition of both Plant and soil microbial communities and their impact on ecosystem functioning.
Richard Michalet - One of the best experts on this subject based on the ideXlab platform.
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Facilitative Plant interactions and climate simultaneously drive alpine Plant diversity
Ecology Letters, 2014Co-Authors: Lohengrin A. Cavieres, Bradley J. Cook, Richard Michalet, Bradley J. Butterfield, Rob W Brooker, Christopher J Lortie, Christian Schöb, Francisco I Pugnaire, Zaal Kikvidze, Sa XiaoAbstract:Interactions among species determine local-scale diversity, but local interactions are thought to have minor effects at larger scales. However, quantitative comparisons of the importance of biotic interactions relative to other drivers are rarely made at larger scales. Using a data set spanning 78 sites and five continents, we assessed the relative importance of biotic interactions and climate in determining Plant diversity in alpine ecosystems dominated by Nurse-Plant cushion species. Climate variables related with water balance showed the highest correlation with richness at the global scale. Strikingly, although the effect of cushion species on diversity was lower than that of climate, its contribution was still substantial. In particular, cushion species enhanced species richness more in systems with inherently impoverished local diversity. Nurse species appear to act as a ‘safety net’ sustaining diversity under harsh conditions, demonstrating that climate and species interactions should be integrated when predicting future biodiversity effects of climate change.
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positive associations involving the tussock grass panicum turgidum forssk in the air tenere reserve niger
Journal of Arid Environments, 2007Co-Authors: Fabien Anthelme, Richard Michalet, M. SaadouAbstract:In the Saharan mountain range of the Air, Niger, the tussock-grass Panicum turgidum Forssk. was hypothesized to act as a Nurse Plant for a number of species. Multiple spatial positive associations involving P. turgidum were detected along an aridity gradient with an index comparing species richness inside vs. outside tussocks. Associated Plants were annuals and young and/or small perennials. Comparative abiotic measurements inside tussocks and in openings showed that P. turgidum diminished seriously the stress induced by vapor pressure deficit (VPD) during the harshest periods of the day (p<0.001, randomization test). This trait identified it as a potential Nurse Plant. The preference for hosted Plants to develop inside dead tussocks rather than in living tussocks at the driest site may indicate that the Nurse Plant potential of P. turgidum tussocks declined in the presence of extreme water stress. Further experimental work, especially removal experiments, should improve the understanding of the underlying mechanisms of facilitation processes in this particularly harsh environment.
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Positive associations involving the tussock grass Panicum turgidum Forssk. in the Air-Tenere Reserve, Niger
Journal of Arid Environments, 2007Co-Authors: Fabien Anthelme, Richard Michalet, M. SaadouAbstract:In the Saharan mountain range of the Air, Niger, the tussock-grass Panicum turgidum Forssk. was hypothesized to act as a Nurse Plant for a number of species. Multiple spatial positive associations involving P. turgidum were detected along an aridity gradient with an index comparing species richness inside vs. outside tussocks. Associated Plants were annuals and young and/or small perennials. Comparative abiotic measurements inside tussocks and in openings showed that P. turgidum diminished seriously the stress induced by vapor pressure deficit (VPD) during the harshest periods of the day (p
Gerald P Quinn - One of the best experts on this subject based on the ideXlab platform.
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Nurse Plant effects of a dominant shrub duma florulenta on understorey vegetation in a large semi arid wetland in relation to flood frequency and drying
Journal of Vegetation Science, 2015Co-Authors: Cassandra James, Samantha J. Capon, Gerald P QuinnAbstract:Questions: Do Nurse Plant interactions significantly influence understorey vegetation diversity in a large, semi-arid, shrub-dominated wetland? How do the modes and net effects of Nurse Plant interactions vary spatially along a flood frequency gradient, and temporally in response to drying? Location: Narran Lakes Ramsar site, New South Wales, Australia. Methods: Microhabitat characteristics, understorey vegetation and germinable soil seed banks were investigated in shrub and open habitats across a flood frequency gradient in a large, semi-arid wetland dominated by open shrubland under productive conditions following floodwater recession and again following 6 mo of drought. Split-plot ANOVA and multivariate analyses were used to determine the effects of shrubs on microhabitat character, understorey vegetation cover, species diversity, richness and composition and germinable soil seed banks. Results: Microhabitat characteristics, including canopy cover, litter cover and soil character, all differed between shrub and open habitats, especially in the most frequently flooded sites. Under productive conditions following flooding, lignum shrubs suppressed understorey vegetation cover but increased species richness at the site scale across the flood frequency gradient and, in the most frequently flooded sites, supported higher species density at a microhabitat scale. Under dry conditions, lignum shrubs had a positive effect on understorey vegetation cover, species richness and species density across the flood frequency gradient, but particularly in frequently flooded sites. A significant difference in soil seed bank composition between shrub and open habitats was only observed in frequently flooded sites. Conclusions: Nurse Plant interactions appear to play an important role in determining understorey vegetation diversity in the lignum shrubland of the Narran Lakes wetland system. The modes and net effects of these Nurse Plant interactions vary in space and time in relation to flood history and drying. Positive interactions, probably involving microhabitat amelioration, appear to be particularly important to Plant diversity and abundance under dry conditions. Under more favourable wetter conditions, lignum shrubs also contribute to understorey vegetation diversity by facilitating the establishment of different species than those dominating open habitats. Our findings have implications for the management of perennial shrubs and hydrological regimes in such wetlands.
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Nurse Plant effects of a dominant shrub (Duma florulenta) on understorey vegetation in a large, semi‐arid wetland in relation to flood frequency and drying
Journal of Vegetation Science, 2015Co-Authors: Cassandra James, Samantha J. Capon, Gerald P QuinnAbstract:Questions: Do Nurse Plant interactions significantly influence understorey vegetation diversity in a large, semi-arid, shrub-dominated wetland? How do the modes and net effects of Nurse Plant interactions vary spatially along a flood frequency gradient, and temporally in response to drying? Location: Narran Lakes Ramsar site, New South Wales, Australia. Methods: Microhabitat characteristics, understorey vegetation and germinable soil seed banks were investigated in shrub and open habitats across a flood frequency gradient in a large, semi-arid wetland dominated by open shrubland under productive conditions following floodwater recession and again following 6 mo of drought. Split-plot ANOVA and multivariate analyses were used to determine the effects of shrubs on microhabitat character, understorey vegetation cover, species diversity, richness and composition and germinable soil seed banks. Results: Microhabitat characteristics, including canopy cover, litter cover and soil character, all differed between shrub and open habitats, especially in the most frequently flooded sites. Under productive conditions following flooding, lignum shrubs suppressed understorey vegetation cover but increased species richness at the site scale across the flood frequency gradient and, in the most frequently flooded sites, supported higher species density at a microhabitat scale. Under dry conditions, lignum shrubs had a positive effect on understorey vegetation cover, species richness and species density across the flood frequency gradient, but particularly in frequently flooded sites. A significant difference in soil seed bank composition between shrub and open habitats was only observed in frequently flooded sites. Conclusions: Nurse Plant interactions appear to play an important role in determining understorey vegetation diversity in the lignum shrubland of the Narran Lakes wetland system. The modes and net effects of these Nurse Plant interactions vary in space and time in relation to flood history and drying. Positive interactions, probably involving microhabitat amelioration, appear to be particularly important to Plant diversity and abundance under dry conditions. Under more favourable wetter conditions, lignum shrubs also contribute to understorey vegetation diversity by facilitating the establishment of different species than those dominating open habitats. Our findings have implications for the management of perennial shrubs and hydrological regimes in such wetlands.
Long Yang - One of the best experts on this subject based on the ideXlab platform.
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testing the stress gradient hypothesis during the restoration of tropical degraded land using the shrub rhodomyrtus tomentosa as a Nurse Plant
Restoration Ecology, 2013Co-Authors: Nan Liu, Hai Ren, Sufen Yuan, Qinfeng Guo, Long YangAbstract:The relative importance of facilitation and competition between pairwise Plants across abiotic stress gradients as predicted by the stress-gradient hypothesis has been confirmed in arid and temperate ecosystems, but the hypothesis has rarely been tested in tropical systems, particularly across nutrient gradients. The current research examines the interactions between a pioneer shrub Rhodomyrtus tomentosa (the Nurse Plant) and seedlings of a transPlanted native woody Schima superba (the target species) in a tropical system in which position on a slope corresponds with a nutrient gradient; high soil nutrients at the slope bottom and relatively low soil nutrients at the slope top. In contrast, soil physical traits were more favorable for seedling growth under the shrub than in open spaces. The effect of R. tomentosa on S. superba survival was positive (facilitation) at the top of the slope, as indicated by the relative interaction index (RII), but negative in the bottom (competition). RII indicated a positive effect on seedling height at the top of the slope but was not at the bottom. Seedling survival was positively related to soil nutrient level and negatively related to soil acidity, but seedling growth of S. superba seemed to be enhanced by the shrub canopy. Thus, the results seem to support stress-gradient hypothesis in terms of target species survival but not growth. We suggest using the shrub as a Nurse Plant in forest restoration in tropical degraded land with caution because not all of its effects on target species are positive.
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can perennial dominant grass miscanthus sinensis be Nurse Plant in recovery of degraded hilly land landscape in south china
Landscape and Ecological Engineering, 2013Co-Authors: Long Yang, Nan Liu, Hai Ren, Jun WangAbstract:Perennial C4 grasses, especially Miscanthus sinensis, are widely distributed in the degraded lands in South China. We transPlanted native and exotic tree seedlings under the canopy of M. sinensis to assess the interaction (competition or facilitation) between dominant grass M. sinensis and tree seedlings. The results of growth, chlorophyll fluorescence, and ultrastructure showed that negative effects may be stronger in perennial dominant grass M. sinensis. Although M. sinensis buffered the air temperature, improved soil structure, and increased soil phosphorus content, these beneficial effects were outweighed by the detrimental effect, especially overshading. To ensure the establishment of target native species in M. sinensis communities in degraded lands of South China, restoration strategies should include removing aboveground vegetation, Planting target species seedlings in openings to reduce the effects of canopy shading, and/or selecting competition-tolerant target species. Also, seedlings of exotic species used in restoration engineering cannot be directly Planted under the canopy of M. sinensis.
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Testing the Stress‐Gradient Hypothesis During the Restoration of Tropical Degraded Land Using the Shrub Rhodomyrtus tomentosa as a Nurse Plant
Restoration Ecology, 2013Co-Authors: Nan Liu, Hai Ren, Sufen Yuan, Qinfeng Guo, Long YangAbstract:The relative importance of facilitation and competition between pairwise Plants across abiotic stress gradients as predicted by the stress-gradient hypothesis has been confirmed in arid and temperate ecosystems, but the hypothesis has rarely been tested in tropical systems, particularly across nutrient gradients. The current research examines the interactions between a pioneer shrub Rhodomyrtus tomentosa (the Nurse Plant) and seedlings of a transPlanted native woody Schima superba (the target species) in a tropical system in which position on a slope corresponds with a nutrient gradient; high soil nutrients at the slope bottom and relatively low soil nutrients at the slope top. In contrast, soil physical traits were more favorable for seedling growth under the shrub than in open spaces. The effect of R. tomentosa on S. superba survival was positive (facilitation) at the top of the slope, as indicated by the relative interaction index (RII), but negative in the bottom (competition). RII indicated a positive effect on seedling height at the top of the slope but was not at the bottom. Seedling survival was positively related to soil nutrient level and negatively related to soil acidity, but seedling growth of S. superba seemed to be enhanced by the shrub canopy. Thus, the results seem to support stress-gradient hypothesis in terms of target species survival but not growth. We suggest using the shrub as a Nurse Plant in forest restoration in tropical degraded land with caution because not all of its effects on target species are positive.
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The shrub Rhodomyrtus tomentosa acts as a Nurse Plant for seedlings differing in shade tolerance in degraded land of South China
Journal of Vegetation Science, 2010Co-Authors: Long Yang, Jun WangAbstract:Questions: What are the Nurse effects of Rhodomyrtus tomentosa in degraded land of South China? Are canopy or soil factors responsible for the main Nurse effect? Do facilitative effects increase with the shade tolerance of the target species? Location: Degraded shrubland in South China. Methods: Seedlings of three native climax woody species (Schima superba, Michelia macclurei, Castanopsis fissa) that differ in shade tolerance were subjected to four treatments by transPlantation: (1) under the canopy of R. tomentosa shrubs; (2) in open interspaces without vegetation cover (control); (3) under the canopy of R. tomentosa from which canopies had been removed; and (4) in open interspaces without vegetation but covered by branches and leaves of R. tomentosa. Results: At low soil nutrient levels, increased canopy shade, soil porosity and soil moisture under the canopy of R. tomentosa increased seedling survival of the climax tree species S. superba, C. fissa and M. macclurei, and shoot height of S. superba. The Nurse effect (a form of facilitation) of R. tomentosa depended more on canopy shade than on soil amelioration. The magnitude of facilitation or Nurse effect was positively correlated with shade tolerance of the target species. Conclusions: Use of Nurse Plants in restoration differs from traditional reforestation (clearing and/or burning to reduce interspecific competition between target tree species and non-target species) because it focuses on positive interactions between Nurse Plants and target Plants that increase establishment of target species and reduce time required for restoration. Because Nurse effects of R. tomentosa shrubs tended to be larger on target species with greater shade tolerance, shade-tolerant Plants are suggested as target species to accelerate restoration.
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Nurse Plant theory and its application in ecological restoration in lower subtropics of China
Progress in Natural Science, 2008Co-Authors: Long YangAbstract:Abstract Nurse Plants are those that facilitate the growth and development of other Plant species (target species) beneath their canopy because they offer benign microhabitats that are more favorable for seed germination and/or seedling recruitment than their surrounding environment. Nurse Plants have been mainly used to restore vegetation in arid and sub-arid zones in recent years. Based on summarizing the definition of Nurse Plant and target Plant, we review the nursing effect mechanisms, ecological factors that influence nursing effect, relationships between Nurse Plant and ecological restoration. This review also brings forward possible pairs of Nurse and target species at lower subtropical areas. Furthermore, we provide the potential tendency in Nurse Plant research and application.
