Aims The prediction that facilitation is the dominant interaction in physically stressful conditions has been supported by many but not all field studies.In the present paper,we tested the effects of the identity of species,the local environmental conditions and the currencies of performance measurement on such variation.Methods Using contrasting two plots,six species,and up to five multiple traits,we comprehensively explored the effects of the above factors on the assessment of plant interactions in an alpine meadow of the QingHai Tibetan Plateau.Additionally,we attempted to figure out the possible mechanisms underlying the responses observed.The data were analysed by both standard ANOVAs and multivariate statistics.Important findings Our results demonstrated that the response to the removal of neighbours was both species and trait specific,and the effect of the ocal environmental conditions was dependent on the species involved.The contrast between plots had crucial influence on the net interactions of Kobresia macrantha,but little effect on Elymus nutans.Regarding the abiotic conditions,neighbours had significant impact on soil temperature,moist and solar radiation.The results contribute to advance our knowledge on the potential underlying factors influencing the assessment of facilitation.
Chengjin ChuYoushi WangQi LiLuqiang ZhaoZhengwei RenSa XiaoJianli YuanGang Wang
Plants only interact with neighbors over restricted distances,so local conditions are of great significance for plants.In this study,a spatially-explicit,individual-based model was constructed to explore the effects of size variation and spatial structure on adaptive plasticity of plant height in response to light competition.In the model a plant maintains its height at an optimal value in order to maximize its growth rate,and this optimal height increases with the increase of the intensity of light competition experienced by the individual plant.When the spatial pattern of the population is non-uniform or there is size variation among individual plants,the height growth curves of individuals different from each other vary due to the differences in the local light environment,and there is also variation in the allocation of photosynthate to height growth among the individual plants.There is no ESS height or height growth strategy on which all plants will converge.Our results indicate that the plasticity of plants' height growth reactions to the light competition should be considered at the individual level and they argue strongly for the importance of the spatial pattern and neighborhood effects in generating the diversity of heights and height growth strategies in plant population.
CHEN ShuYan ZHANG JiaLin JIA Peng XU Jin WANG Gang XIAO Sa
Aims The process of facilitation,where a species increases the survival,growth,and fitness of another species,is becoming increasingly recognized as a critical factor in shaping the structure of plant communities.This process is particularly important in stressful environments.Yet few studies have attempted to incorporate positive interactions into community ecological theories such as the neutral theory of biodiversity.Here,we use an equalizing trade-off model as a foundation to study the potential impact of facilitation on species richness and community temporal turnover.Methods Based on a spatially explicit birth–death trade-off model,we assume that the occurrence of facilitation is dependent on the presence of interspecific neighbours.We further propose that the realized birth rate for a given individual subject to facilitation is proportional to the number of interspecific neighbours within its neighbourhood.Thus,in our model,the individuals of rare species will benefit more from the existence of heterospecific individuals than common species.Important Findings As the facilitative coefficient increased,the species richness for simulated communities at the dynamically stochastic equilibrium was also increasing.Simulations also demonstrated that facilitation could increase the replacement of species through time:communities with facilitation become more dissimilar(i.e.have smaller Bray–Curtis similarity values)than communities without or with a lower degree of facilitation after the same time interval.Facilitation from interspecific neighbours on rare species increased their population sizes and consequently made them less prone to extinction,thus enhancing species richness.Meanwhile,in a saturated community,with the increase of species richness,mean population size of entire communities decreased,making species more prone to extinction on average,and thus increased the community temporal turnover.Our results suggest that future experimental work on the effect of facilitation on community-level properties
