Facilitative Interactions Research Articles

A model for seagrass species competition: Dynamics of the symmetric case

We propose a general population dynamics model for two seagrass species growing and interacting in two spatial dimensions. The model includes spatial terms accounting for the clonal growth characteristics of seagrasses, and coupling between species through the net mortality rate. We consider both intraspecies and interspecies facilitative and competitive interactions, allowing density-dependent interaction mechanisms. Here we study the case of very similar species with reciprocal interactions, which allows reducing the number of the model parameters to just four, and whose bifurcation structure can be considered the backbone of the general case. We find that the parameter space can be divided into ten regions with qualitatively different bifurcation diagrams. These regions can be further grouped into just five regimes with different ecological interpretations. Our analysis allows the classification of all possible density distributions and dynamical behaviors of meadows with two coexisting species.

Direct and higher‐order interactions in plant communities under increasing weather persistence

Climate change is increasing the weather persistence in the mid‐latitudes, prolonging both dry and wet spells compared to historic averages. These newly emerging environmental conditions destabilize plant communities, but the role of species interactions in this process is unknown. Here, we tested how direct and higher‐order interactions (HOIs) between species may change in synthesized grassland communities along an experimental gradient of increasing persistence in precipitation regimes. Our results indicate that species interactions (including HOIs) are an important determinant of plant performance under increasing weather persistence. Out of the 12 most parsimonious models predicting species productivity, 75% contained significant direct interactions and 92% significant HOIs. Inclusion of direct interactions or HOIs respectively tripled or quadrupled the explained variance of target species biomass compared to null models only including the precipitation treatment. Drought was the main driver of plant responses, with longer droughts increasing direct competition but also HOI‐driven facilitation. Despite these counteracting changes, drought intensified net competition. Grasses were generally more involved in competitive interactions whereas legumes were more involved in facilitative interactions. Under longer drought, species affinity for nutrient rich or wet environments resulted in more negative direct interactions or HOIs, respectively. We conclude that HOIs, crucially depending on species identity, only partially stabilize community dynamics under increasing weather persistence.Keywords: drought, facilitation and competition, grasslands, higher‐order interactions, increasing weather persistence, species interactions

Warming had contrasting effects on the importance of facilitative interactions with a cushion nurse species on native and non‐native species in the high‐Andes of central Chile

Alpine habitats are regarded as particularly vulnerable to the effects of climate change. On one hand, global warming is supposed to contributes to alpine environments becoming less stressful. On the other hand, altered snowpack due to warmer temperatures can intensify the stress in these habitats. The presence of non‐native plants on some of these habitats is due to the facilitative effects exerted by native nurse plants, becoming an additional threat. According to the stress gradient hypothesis the importance of facilitative interactions with nurse species is expected to diminish as environmental harshness decreases due to climate change yet remains important if climate change heightens the stress in alpine habitats. However, the responses also depend on climate change's impact on the nurse species. We conducted an experimental warming experiment in the Andes of the central Chile to assess the effects of warmer temperatures on the growth, reproduction and photochemical efficiency of the cushion nurse plant Azorella madreporica. Further we performed a cushion removal experiment involving three native species (Gamocarpha ventosa, Nocaccea magellanica and Rytidosperma pictum) and two non‐native species (Cerastium arvense and Taraxacum officinale) to assess whether facilitative interactions changed with warming. We expected that under warmer conditions facilitation continued be important for the native species but decreased for the non‐natives as the latter are abundant at warmer low elevations. We found that warmer conditions increased the photochemical efficiency and growth of the nurse cushions. Removal of cushions resulted in high mortality rates for all species. However, under warmer conditions, native species exhibited lower survival rates, whereas non‐natives showed no significant changes compared to control groups. In summary, warmer temperatures were beneficial for the nurses maintaining the importance of facilitative interactions for native species, but not for the non‐natives.

Assessing the occurrence of soil improvement and its relationship to the dominant life form in the high mountains of Central Spain

Soil in mountainous regions is vital to the health and preservation of these unique and diverse ecosystems. In dry and semi-arid regions, vegetation patches play a crucial role in soil nutrient heterogeneity through continuous feedback with soils, acting as barriers to collect runoff water, sediments, and nutrients from bare soil regions. Soil amelioration, an enhancement of soil biogeochemical processes, results in the formation of “fertility islands,” the extent of which is contingent on the plant species in question, as well as nutrient dynamics and water availability. Here, we collected soil from across a two-peak altitudinal gradient in the Sierra de Guadarrama high-mountains, each peak featuring a different dominant vegetation type (herbs vs. cushion-like) to compare soil nutrients and properties between bare soil and vegetation-covered patches (microhabitats). Soil improvement was assessed in the microhabitats using the Relative Interaction Index (RII). Fertility islands were shown to be prevalent in high-mountain ecosystems, as soil quality and properties were higher beneath vegetation-covered regions than bare soils. There was a difference in RIIs between the transects, with greater soil improvement in the cushion-dominated transect than the herb-dominated one. Changes in nutrient levels were unrelated to patch successional stage, indicaing that plant generations may not shape the spatial variability of soil attributes. Instead, species variety or the presence of dominant clonal species increased soil nutrients and aggregate stability, highlighting the importance of root shape and high biomass in nutrient retention and soil reinforcement. Finally, our findings imply that the poor, shallow soils in the examined peaks, in comparison to other mountains, may account for the poor facilitative interactions. Competition for the scarce resources at these peaks may intensify as climate warms. Thus, while these plants may grow with minimum assistance under current climate circumstances, their associations may be especially vulnerable to climate change.

Facilitative and competitive interactions between mycorrhizal and nonmycorrhizal plants in an extremely phosphorus-impoverished environment: role of ectomycorrhizal fungi and native oomycete pathogens in shaping species coexistence.

Nonmycorrhizal cluster root-forming species enhance the phosphorus (P) acquisition of mycorrhizal neighbours in P-impoverished megadiverse systems. However, whether mycorrhizal plants facilitate the defence of nonmycorrhizal plants against soil-borne pathogens, in return and via their symbiosis, remains unknown. We characterised growth and defence-related compounds in Banksia menziesii (nonmycorrhizal) and Eucalyptus todtiana (ectomycorrhizal, ECM) seedlings grown either in monoculture or mixture in a multifactorial glasshouse experiment involving ECM fungi and native oomycete pathogens. Roots of B. menziesii had higher levels of phytohormones (salicylic and jasmonic acids, jasmonoyl-isoleucine and 12-oxo-phytodienoic acid) than E. todtiana which further activated a salicylic acid-mediated defence response in roots of B. menziesii, but only in the presence of ECM fungi. We also found that B. menziesii induced a shift in the defence strategy of E. todtiana, from defence-related secondary metabolites (phenolic and flavonoid) towards induced phytohormone response pathways. We conclude that ECM fungi play a vital role in the interactions between mycorrhizal and nonmycorrhizal plants in a severely P-impoverished environment, by introducing a competitive component within the facilitation interaction between the two plant species with contrasting nutrient-acquisition strategies. This study sheds light on the interplay between beneficial and detrimental soil microbes that shape plant-plant interaction in severely nutrient-impoverished ecosystems.

Homogeneous microenvironmental conditions under nurses promote facilitation

Abstract Biotic interactions are highly affected by species traits and micro‐environmental variability. Research on facilitation has primarily focused on how nurse species alleviate abiotic stress for beneficiary species, while the impact of the micro‐environmental variability generated by nurse plants in shaping facilitation outcomes is poorly understood. This study has two objectives: (i) To evaluate which traits define beneficiary species and (ii) to evaluate whether nurse and non‐nurse species differ in their ability to reduce abiotic stress and its variability under their canopy. We sampled recruits in two arid and stressful environments to assess (i) which species accumulate more juveniles beneath their canopy controlling for their coverage (nurse vs. non‐nurse species) and (ii) which species benefited from facilitation by determining whether they tend to recruit more beneath other species or on the bare ground (beneficiary/non‐beneficiary). First, we compared how nurse and non‐nurse species modify the physical and chemical microenvironments underneath their canopy, both in terms of magnitude and variation. Second, we compared root growth, water retention and nutrient accumulation in juvenile plants of beneficiary and non‐beneficiary species. We found that facilitation is enhanced by species that provide a more homogeneous microenvironment rather than an intense reduction of microenvironmental stress under their canopy. In addition, the juveniles of beneficiary species invest more in root development, accumulate Ca and S in their shoot tissues, and show a higher water content than non‐beneficiary species. Our findings indicate that the homogeneity of microenvironments plays a crucial role in facilitative interactions, and the juveniles of beneficiary species show a less conservative strategy, investing more in resource acquisition than juveniles of non‐beneficiary species. Read the free Plain Language Summary for this article on the Journal blog.

Better soon than never: climate change induces strong phenological reassembly in the flowering of a Mediterranean shrub community

Abstract Background and Aims Flowering is a key process in the life cycle of a plant. Climate change is shifting flowering phenologies in the Northern Hemisphere, but studies with long data series at the community level are scarce, especially those considering the consequences of phenological changes for emerging ecological interactions. In the Mediterranean region, the effects of climate change are stronger than the global average and there is an urgent need to understand how biodiversity will be affected in this area. Methods In this study, we investigated how the entire flowering phenology of a community comprising 51 perennial species from the south of the Iberian Peninsula changed from the decade of the 1980s to the 2020s. Furthermore, we have analysed the consequences of these changes for flowering order and co-flowering patterns. Key Results We have found that the flowering phenology of the community has advanced by ~20 days, which is coherent with the increasing temperatures related to climate change. Individual species have generally advanced their entire flowering phenology (start and end) and increased their flowering duration. The early flowering has resulted in a re-organization of the flowering order of the community and generated new co-flowering assemblages of species, with a slight trend towards an increase of shared flowering time among species. Conclusions The advanced flowering phenology and changes in flowering duration reported here were of unprecedented magnitude, showcasing the extreme effects of climate change on Mediterranean ecosystems. Furthermore, the effects were not similar among species, which could be attributed to differences in sensitivities of environmental cues for flowering. One consequence of these changes in flowering times is ecological mismatches, indicated by changes in the flowering order and co-flowering between decades. This new scenario might lead to new competitive or facilitative interactions and to the loss or gain of pollinators.

Non-linear and non-local plant–plant interactions in arid climate: Allometry, criticality and desertification

We present a model that considers the non-linear and non-local facilitative and competitive interactions in arid and semiarid climates. These two botanical processes are interconnected and operate at different spatial scales. Seed dispersal is modeled as a diffusion process. We consider landscapes populated by a dominant species to be isotropic.and homogeneous environmental conditions. We included the allometric factor in the modeling, considering the age classes. We show that allometry tends to move the critical and tipping points towards a low level of aridity. This alteration of aridity conditions can prevent desertification and thus avoid vegetation collapse. Unlike other interaction redistribution models, we show that even in the absence of allometry, critical and tipping points have a finite biomass. Consequently, a branch of low-biomass density is stabilized. Finally, we show that the allometric factor reduces the range of symmetry-breaking instability and favors the formation of homogeneous cover rather than vegetation patterns.

Positive interactions in shaping neighborhood diversity during secondary forests recovery: Revisiting the classical paradigm

Secondary forests recovery, following disturbances, plays a pivotal role in ecosystem dynamics and biodiversity recovery. Given the rising frequency and intensity of anthropogenic disturbances within forest ecosystems, understanding the mechanisms underlying secondary succession is vital for the effective restoration and conservation of compromised ecosystems. In the classical secondary succession paradigm, early-arriving species are gradually replaced by their later-arriving counterparts. However, over time, valuable historical insights into the involvement of pioneer species become obscured and challenging to discern, particularly in community-scale studies. Consequently, this obscurity has predominantly directed contemporary research predominantly towards examining the consequences of species replacement by later-arriving counterparts during secondary succession. Concurrently, the mechanisms by which pioneer species facilitate or impede the establishment of diversity among later-arriving species remain insufficiently clarified. In this study, we established a 6-ha dynamic forest plot within a secondary forest that has undergone nearly four decades of restoration. Specifically, we utilized the individual species-area relationship (ISAR) framework to evaluate the neighborhood diversity structure of 49 evergreen and 20 deciduous species identified within our evergreen broad-leaved forest plot. Our findings indicate that deciduous tree species undergo a transition from diversity accumulator to repeller in diversity structuring as they progress through different life history stages. On the other hand, evergreen trees either engage in diversity accumulator or neutral. Through repeated plot surveys, we established a comprehensive dataset encompassing the mortality and regeneration of evergreen and deciduous tree species from 2014 to 2020. Spatial covariance models were employed to quantify the distinct effects of density dependence on deciduous and evergreen tree species. The results demonstrate significant negative density dependence mortality and self-thinning in deciduous species at all life history stages. Conversely, adult evergreen tree species facilitate the survival of their seedlings and saplings. In contrast to the classical paradigm that primarily focuses on the replacement of pioneer species by successor species, our findings reveal: (i) self-inhibition mechanisms that shape the neighborhood diversity spatial patterns among deciduous tree species, (ii) self-promotion or neutral mechanisms that influence the diversity spatial patterns of evergreen tree species, and (iii) early-arriving tree species that play a role in facilitating the establishment and diversity of late-arriving counterparts. These results not only signify the significant role of late-arriving species in the natural recovery of secondary forests but also propose that integrating the mechanisms of facilitation, inhibition, and neutral interactions into the classic forest succession paradigm could reshape our interpretation of interactions within plant communities across historical, current, and future timeframes. Such comprehension holds implications for forest management policies and conservation practices.

What works in interventions targeting loneliness: a systematic review of intervention characteristics

BackgroundLoneliness has been linked to negative health and economic outcomes across the life course. Health effects span both physical and mental health outcomes, including negative health behaviours, lower well-being, and increased mortality. Loneliness is however preventable with effective intervention. This systematic review aims to identify what has worked in interventions for loneliness to guide the development of future interventions.MethodsEight electronic databases (Medline, Embase, PsycINFO, Social Policy and Practice, Social Sciences Citation Index, Epistemonikos, CINAHL, Cochrane Library) were systematically searched from inception to February 2022 using terms for intervention and loneliness to identify relevant interventions in the general population. No restrictions on age, socio-economic status, or geographic location were imposed. Studies were to measure loneliness as the primary outcome through a validated scale or single-item question. Case studies were excluded. Additional studies were identified through citation chasing. Extracted data included study and intervention characteristics, and intervention effectiveness for cross-study comparison. Critical appraisal was conducted using the Joanna Briggs Institute and Critical Appraisal Skills Programme tools before the studies were summarised in a narrative synthesis.ResultsSearches identified 4,734 hits, from which 22 studies were included in this review. Of these studies, 14 were effective in reducing loneliness. Additionally, five studies presented unclear findings, and three concluded no decrease in loneliness. Interventions varied between group vs. individual format, online vs. in person delivery, and regarding both intervention duration and individual session length. Furthermore, this review highlighted five key areas when considering designing an intervention for loneliness: use of between session interaction, inclusion of clear learning mechanisms, role of active participation, number of opportunities for group or facilitator interaction, and variation in teaching and learning styles.ConclusionsGroup sessions seem preferred to individual formats, and interaction through active participation and group or facilitator contact appear beneficial, however studies also recognised the importance of a person-tailored approach to delivery. Studies suggest there is no ‘quick fix’ to loneliness, but that learnt practices, behaviours, and community connection should be built into one’s lifestyle to achieve sustained intervention effectiveness. Future interventions should consider longer follow-up periods, male and populations with lower educational levels.

Let Students Work: Analysis of the Role of Differing Facilitation on Student Engagement in a Large Stadium-Style Lecture Hall.

The classroom environment is shaped by factors such as facilitation style, curricular design, and classroom layout. These factors are all inputs into student framing of the classroom environment and affect a student's comfort interacting within it. Promoting student discourse in active learning environments provides students the opportunity to explain their thinking and develop their understanding of natural phenomena. However, successfully implementing these practices in large lecture environments is often difficult. Undergraduate introductory chemistry lectures were investigated to identify the effects that instructional practices had on student engagement. Instructor facilitation, question level, and student interactions were analyzed and compared to provide insights into what instructional practices may promote or hinder student engagement in a large enrollment course. Overall instructors were positioning themselves as an authority on knowledge in the classroom by leading questions authoritatively like instructor-focused didactic lecturing that led to a decrease in student engagement. These results highlight the complexity of the classroom ecosystem related to student interactions and the role that facilitation plays in social and cognitive engagement.

Seasonal variation in the balance and strength of cooperative and competitive behavior in patches of blue mussels.

Aggregation into groups may affect performance of individuals through the balance and strength of facilitative versus competitive interactions. We studied in situ how seasonal variation in abiotic environment affects this balance for blue mussels, a semi-sessile species. We hypothesize that seasonal variation in stresses and resources affects the strength of the interaction. We expected that, in benign conditions (here: high food availability, medium temperatures, low hydrodynamic stress), performance is dominated by growth and is better at low densities, while at adverse conditions (here: low food availability, low or high temperatures, high hydrodynamic stress), performance is dominated by survival and higher at high densities. Mussels were kept in shallow subtidal exclosures at 10 different densities for a one-month period. This exact procedure was repeated seven times at the same location within a one-year period. We measured development in mussel patch shape, performance, and environmental parameters. Environmental conditions for mussels were most benign in summer and most adverse in winter. Patches developed into less complex shapes at lower densities, but also after stronger hydrodynamic disturbances. Towards summer, mussels became more active, aggregation behavior increased, and interactions became more pronounced. Towards winter, mussels became less active: aggregation behavior and growth rates declined and at the lowest temperatures survival started to decrease with mussel density. Survival and growth (by proxy of mussel condition) were both density-dependent; however, contrary to our expectations we found positive interactions between density and survival at the most benign conditions in summer and negative interactions at the most adverse conditions in winter. In between the two seasons, the strength of the interactions increased towards summer and decreased towards winter following a bell-shaped pattern. This pattern might be explained by the environmental mediated aggregation behavior of the mussels. The obvious seasonal pattern in balance and strength of density-dependent interactions demonstrates that strength and direction of intra-specific interactions are both strongly affected by environmental context.

Effect of crop combination on yield performance, nutrient uptake, and land use advantage of cereal/legume intercropping systems

ContextCrop type and temporal synchronization are crucial for improving the productivity of intercropping systems, especially with reduced inputs (nitrogen, N, and phosphorus, P). However, the effects of crop type and temporal dynamics on nutrient uptake and yield advantage of cereal/legume intercropping systems are still unclear. ObjectiveThe objective of this study was to assess the effects of different temporal dynamics of intercrops on growth, nutrient-use advantage, land productivity, and economic viability of cereal/legume intercropping systems under arid irrigated conditions. MethodsIn this field study, we used the equal land proportion for all intercrops in both intercropping systems: wheat/chickpea intercropping (wheat/chickpea), where legume (chickpea) was the first-sown crop; and wheat/soybean intercropping (wheat/soybean), with cereal (wheat) being the first-planted crop), and all strip intercropping results were compared with their sole systems: sole chickpea (SCp), sole wheat (SW), and sole soybean (SS). Results and conclusionsHere, we revealed that the improved complementarity and facilitation interactions in wheat/chickpea linked with better phenological synchronization between wheat and chickpea, which resulted in higher relative grain yields, primarily gained from greater biomass accumulation and its translocation towards ears/pods, seeds, and seed weight, than the wheat and soybean in wheat/soybean. Similarly, the intercropped wheat accumulated a significantly higher N (15%) and P (14%) under wheat/chickpea than in wheat/soybean, whereas, in legumes, the N and P uptake of chickpea in wheat/chickpea was 19% and 13% higher than that of soybean in wheat/soybean, respectively. On average, in wheat/soybean, wheat and soybean achieved 62% of SW and 58% of SS yields, while in wheat/chickpea, wheat and chickpea produced 71% and 67% of SW and SCp yields, respectively, demonstrating the advantage of sowing legumes earlier than cereals in intercropping systems. Overall, in wheat/chickpea, the system-level nutrient- and land-use advantage, measured as the land, nitrogen, and phosphorus equivalent ratios, were 1.38, 1.59, and 1.62, respectively, which increased the net profit of wheat/chickpea by 55% compared to wheat/soybean, suggesting that intercropping systems require fewer anthropogenic inputs to produce higher crop yields than sole systems. SignificanceOur results contribute to understanding the effects of crop type and temporal synchronization of intercrop species for maximizing the land productivity of cereal/legume intercropping systems in arid irrigated regions.

Plant-Plant Interdependence and Mutualism Interactions in Heterogeneous Ecosystems still hide a lot of secrets

Plant-Plant Interdependence and Mutualism Interactions in Heterogeneous Ecosystems still hide a lot of secrets

How does facilitation influence the outcome of species interactions?

Abstract Research on facilitation has not had the advantage of being explicitly underpinned by mathematical population dynamic theory. This has limited understanding of the role of facilitation on ecological dynamics and the integration of facilitation into general theory. I show that facilitative interactions can be classified into four categories likely to be dynamically similar to interaction types for which population‐dynamic theory does exist. This classification provides a useful population‐dynamic foundation for facilitation studies and reveals several fundamental questions unanswered by existing empirical work. While facilitation has typically been excluded from studies of ‘competitive’ coexistence, I also describe how coexistence theory does not always default to the assumption that species only compete; recent developments in coexistence theory fully accommodate the potentially important influence of facilitation. Simple models of multispecies population dynamics emphasize the importance of reciprocal interspecific interactions, intraspecific interactions, and density dependence for understanding the outcome of facilitative interactions. I point to approaches for aligning future empirical studies of facilitation with these features. Synthesis: Closely aligning at least some future empirical work on facilitation with existing mathematical population dynamic theory will further improve understanding of the effects of facilitation on ecological dynamics.

First record of plant-plant facilitative interaction from the Moscovian (Pennsylvanian, upper Carboniferous) of North China

Fallen logs acting as a seedbed for trees to aid the regeneration of vegetation is a common ecological strategy in modern forests. However, the origin, occurrence, and evolution of this nurse log strategy in the geological time is unclear. Here we report a ca. 310-million-year-old permineralized cordaitalean tree trunk from the Moscovian (Pennsylvanian, upper Carboniferous) Benxi Formation in Yangquan City, Shanxi Province, North China, with evidence of probable cordaitalean rootlets growing inside the trunk. The specimen is interpreted as a nurse log for regeneration of cordaitaleans in coastal lowlands. It provides the first glimpse of plant-plant facilitative interaction between Pennsylvanian cordaitaleans in Cathaysia. We interpret that the Moscovian cordaitalean seedlings preferentially established on the fallen log owing to the ability of the rotting wood to store fresh water. The nurse log provided a stable substrate in an environment with episodic salinity and/or water table variations. In combination with previous records, it is suggested that a sophisticated terrestrial ecosystem with multiple interactions between plants and other organisms have developed on the central North China Craton no later than the Middle Pennsylvanian.

The facilitation between Staphylococcus carnosus M43 and Zygosaccharomyces rouxii Y-8, and as starter on the quality of broad bean paste

Zygosaccharomyces rouxii (Z. rouxii) and Staphylococcus carnosus (S. carnosus) are fundamental taxa in spontaneous bean-based food fermentation, playing a vital role in flavor generation and macromolecule degradation. The present study aimed to investigate the biological mechanisms underlying the interaction between Z. rouxii Y-8 and S. carnosus M43 in BBP (broad bean paste) moromi by mono- and co-culture. It was found that the biomass of Z. rouxii and S. carnosus was higher in co-culture than that in mono-culture (p < 0.05), indicating that a facilitation relationship among them. Moreover, the observed intensity of facilitation (OIF) peaked at 0.479 ± 0.002 under aerobic conditions, which was higher than that under anaerobic conditions (0.147 ± 0.014). Furthermore, the facilitative microbial interaction showed the stability and robustness during co-culture with different inoculum proportions (1:3, 1:5, 1:7, 1:10) and cell passage from 1 to 4 generations. Physical separation co-culture and acetic acid tolerance test revealed that acetic acid played a crucial role in regulating the interaction between Z. rouxii (R2 = 0.6955) and S. carnosus (R2 = 0.7097), with metabolic complementarity and inhibition alleviation as the underlying mechanisms. Additionally, Z. rouxii and S. carnosus as starter could enhance the accumulation of flavor compound, and accelerate the maturity of BBP fermentation. The dissection of interaction between Z. rouxii and S. carnosus provided valuable insights for revealing the complex web of relationships among microbiota and the development of microbial starter in BBP brewing ecosystem.

Predicting dynamic trajectories of a protected plant community under contrasting conservation regimes: Insights from data-based modelling

Data-based modelling of the dynamic behaviour of ecological communities is a big challenge in systems ecology and conservation biology. Implementing such models to forecast future scenarios is key for supporting decision-making in ecological reserves, given the multiple disturbances threatening their future. Using demographic and dynamic data for three tree (or tree-like) species from the Pedregal de San Ángel Ecological Reserve (Mexico City, Mexico), we constructed a family of dynamical models (using systems of ordinary differential equations) to reconstruct their dynamic interactions. The first two models considered two native species (Pittocaulon praecox and Buddleja cordata), with either antagonistic or cooperative interactions between them. These species have been considered ecosystem engineers playing different roles in the system and determining several community attributes. These models predict the transition from a stable steady state dominated by P. praecox (as reported in the 1950s) to the current community whose structure is apparently shifting to an alternative stable state dominated by B. cordata. The second pair of models additionally incorporate the invasive tree Eucalyptus camaldulensis, which exerts negative effects on all native plant species. The prediction of these models is an E. camaldulensis-dominated state with the exclusion of the native species from the reserve, provided this invasive species follows current population growth trends, without external intervention to check this process. Bifurcation analysis of this latter model allowed us to rationally design optimal intervention strategies that could potentially divert the trajectory from converging to an E. camaldulensis-only configuration into the stable coexistence of the native species. For the two-species and three-species models we made two versions, one with only competitive interactions and another one including a facilitation interaction between B. cordata and P. praecox. This analysis shows that facilitation is a requirement to achieve stable coexistence between the two native species, even in the presence of E. camaldulensis. The models constructed here, which integrate multiple data sources, help clarify conflicting empirical information regarding potential ecological mechanisms, and allow making predictions for strengthening the future management and E. camaldulensis control programs before its effects irreversibly modify the functioning and biodiversity of the biotic community protected in the reserve.

Fine‐scale variation in the effect of the cushion plantAzorella selagoon vascular plants, mosses, hepatics and lichens in the sub‐Antarctic

AbstractQuestionPlant–plant interactions can strongly influence community structure and composition. The outcome of these interactions can vary considerably across space and is often linked to environmental conditions, with, for example, a higher prevalence of facilitative interactions typically being observed under greater environmental severity. To date, most studies have documented shifts from competitive to facilitative (or neutral) plant–plant and plant–lichen interactions along gradients of increasing environmental severity from pairwise interspecific interactions. However, few studies have examined if the outcome of these interactions for different taxonomic groups is dependent on environmental conditions across multiple environmental stress gradients.LocationSub‐Antarctic Marion Island.MethodsWe examine community‐level variation in the response of four taxa (i.e., vascular plants, hepatics, mosses, and lichens) to an interaction with a long‐lived cushion plant species (Azorella selago) that ameliorates microenvironmental conditions, testing how the effect of the cushion plant on the taxa varies along multiple stress gradients at the scale of a landform.ResultsContrary to expectations, even when considering multiple proximate predictor variables, fine‐scale spatial variation in the effect ofA. selagoon the taxa could not be explained. However, the outcome of the interaction withA. selagodiffered between taxonomic groups, with vascular plants benefitting and the non‐vascular taxa experiencing neutral or negative impacts.ConclusionsThis study highlights that the impacts of biotic interactions cannot always be generalized across plant groups, and that it is necessary to consider taxon‐specific responses when predicting community‐level impacts of biotic interactions. More generally, we demonstrate how complex spatial variation in environmental stressors can be explicitly considered when modelling variation in the outcome of plant–plant interactions.

Psychological Phenomenon of Facilitation as a Specific Type of Teacher’s Activity

the purpose of our research is to show what is facilitation; how to organize facilitative interaction to help the teacher for better guidance that can enhance performance and success for the students; to present the ways of facilitative education at the universities; to show the place of facilitation in the structure of Blocks of Cognitive Activity of students. methods of the research. The following theoretical methods of the research were used to solve the tasks formulated in the article: a categorical method, structural and functional methods, the methods of the analysis, systematization, modeling, generalization. Also, in our research we used empirical methods, such as statement experiment.the results of the research. We proved thatthe process of facilitation in educational activities cannot be understood simplistically. Participating in any form of activity and learning consciously are doing quite different things. The ac-tion, if it is imposed by a team of methodologists, teachers, pedagogues, etc., is carried out under pressure on the student, then it is perceived beyond any mea­ning as a so­called “temporary” necessity. In Psychology the following attributes of a person are recognized: a student’s consciousness and activity; attributes of the psyche, such as subjectivity, activity, adaptability; attributes of the person’s consciousness – the experience, knowledge and attitude; attributes of the acti­vity – the awareness, purposefulness, motivation.conclusions. We can unmistakably outline the role of facilitation in these interacting blocks of cognitive activity of students. Facilitation involves chan ging the teacher’s position in the learning process. Updating his/her pedagogical activity in all its directions (blocks), the teacher skillfully facilitates – manages, directs, helps students in their educational activities. As a result of pedagogical activity, a certain new formation appears. So, it is a process of facilitative inter-action, where the main figure is the student himself/herself as the subject of his/her own cognitive activity. Meanwhile, the teacher only uses all the possibilities of the educational environment, directing the activity of the student in order to further in­depth developing of his/her personality.