共查询到20条相似文献，搜索用时 15 毫秒
1.
Junmeng Lu Daniel J. Johnson Xiujuan Qiao Zhijun Lu Qinggang Wang Mingxi Jiang 《Journal of Plant Ecology》2015,8(6):568
Aims Seedlings are vulnerable to many kinds of fatal abiotic and biotic agents, and examining the causes of seedling dynamics can help understand mechanisms of species coexistence. To disentangle the relative importance of neighborhood densities, habitat factors and phylogenetic relatedness on focal seedling survival, we monitored the survival of 5306 seedlings of 104 species>15 months. We address the following questions: (i) How do neighborhood densities, habitat variables and phylogenetic relatedness affect seedling survival? What is the relative importance of conspecific densities, habitat variables and phylogenetic relatedness to seedling survival? (ii) Does the importance of the neighborhood densities, habitat variables and phylogenetic relatedness vary among growth forms, leaf habits or dispersal modes? Specially, does the conspecific negative density dependence inhibit tree and deciduous seedlings more compared with shrub and evergreen species? Does density dependence affect the wind and animal-dispersed species equally?Methods We established 135 census stations to monitor seedling dynamics in a 25-ha subtropical forest plot in central China. Conspecific and heterospecific seedling density in the 1-m 2 seedling plot and adult basal area within a 20-m radius provided neighborhood density variables. Mean elevation, convexity and aspect of every 5- × 5-m grid with seedling plots were used to quantify habitat characteristics. We calculated the relative average phylodiversity between focal seedling and heterospecific neighbors to quantify the species relatedness in the neighborhood. Eight candidate generalized linear mixed models with binominal error distribution were used to compare the relative importance of these variables to seedling survival. Akaike's information criteria were used to identify the most parsimonious models.Important findings At the community level, both the neighborhood densities and phylogenetic relatedness were important to seedling survival. We found negative effects of increasing conspecific seedlings, which suggested the existence of species-specific density-dependent mortality. Phylodiversity of heterospecific neighbors was negatively related to survival of focal seedlings, indicating similar habitat preference shared among phylogenetically closely related species may drive seedling survival. The relative importance of neighborhood densities, habitat variables and phylogenetic relatedness varied among ecological guilds. Conspecific densities had significant negative effect for deciduous and wind-dispersed species, and marginally significant for tree seedlings>10cm tall and animal-dispersed species. Habitat variables had limited effects on seedling survival, and only elevation was related to the survival of evergreen species in the best-fit model. We conclude that both negative density-dependent mortality and habitat preference reflected by the phylogenetic relatedness shape the species coexistence at seedling stage in this forest. 相似文献
2.
Seedlings are vulnerable to many biotic and abiotic agents, and studying seedling dynamics helps understand mechanisms of species coexistence. In this study, the relative importance of biotic neighbors and habitat heterogeneity to seedling survival was examined by generalized linear mixed models for 33 species in a spruce‐fir valley forest in northeastern China. The results showed that the relative importance of these factors varied with species and functional groups. Conspecific negative density dependence (CNDD) was important to the survival of Abies nephrolepis and Picea koraiensis seedling, whereas phylogenetic negative density dependence (PNDD) was critical to Pinus koraiensis and Betula platyphylla, as well as functional groups of tree, deciduous, and shade‐intolerant seedlings. For shrubs and Acer ukurunduense, habitat heterogeneity was significant. Despite of the significance of CNDD, PNDD, and habitat heterogeneity on seedling survival, large proportions of the total variance were not accounted for by the studied variables, suggesting the needs to examine the influences of other factors such as pests, diseases, herbivores, forest structure, species functional traits, and microclimatic conditions on seedling survival in the future. 相似文献
3.
密度制约对物种共存起着重要作用。随着密度制约效应研究的深入, 亲缘关系较近的物种间表现出的密度制约效应逐渐被人们认识。本研究基于2009和2014年对宝天曼1 ha落叶阔叶林样地的2次调查数据, 利用广义线性混合模型分析了重要值排名前11位的物种不同邻域尺度的密度制约效应对不同径级(小径级(1 cm ≤ DBH < 5 cm)、中径级(5 cm ≤ DBH < 10 cm)、大径级(DBH ≥ 10 cm))目标个体存活的影响。研究表明: (1) 5年间样地中DBH ≥ 1 cm的所有个体的年均死亡率和增员率分别为5.85%和0.27%; (2)有5个物种的个体存活率与同种邻体个体数及同种邻体胸高断面积显著负相关; (3)小径级个体的存活在5 m的邻域范围内受同种密度制约和谱系密度制约的影响都很显著; 中径级个体在3个尺度上受到的密度制约和谱系密度制约的影响都不大; 大径级个体在7.5 m、10 m邻域范围内受谱系密度制约影响显著。结果表明, 同种密度制约和谱系密度制约效应对宝天曼落叶阔叶林不同生长阶段的树木个体影响不同。 相似文献
4.
Paine CE Norden N Chave J Forget PM Fortunel C Dexter KG Baraloto C 《Ecology letters》2012,15(1):34-41
Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedling's mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities. 相似文献
5.
《植物生态学报》2016,40(7):711
Aims Our study aimed to understand the effects and the relative importance of biotic neighborhood and habitat heterogeneity for tree seedling survival in a secondary mixed conifer and broad-leaved forest in Changbai Mountain, north-eastern China.
Methods The generalized mixed linear model was used to examine the relative effects of biotic neighborhood and habitat heterogeneity on seedling survival over two years.
Important findings Our results showed that both biotic neighborhood and habitat heterogeneity had significant effects on the seedling survival at community level. The local environment suitable for the adult growth was also suitable for seedling survival. The soil moisture and soil available nitrogen exhibited significant positive effects on seedling survival. On the other hand, seedling density had significant negative effects on seedling survival due to the individual competition. Particularly, we found significant negative density-dependent effects on seedling survival which was caused by conspecific adult and seedling neighbors. As expected, with the increasing of seedling survival age, the habitat heterogeneity became more important on seedling survival. These results suggest that both local biotic neighborhood and habitat heterogeneity drive seedling survival in this temperate forest, and their relative importance varies with different seedling age classes and species traits. 相似文献
Methods The generalized mixed linear model was used to examine the relative effects of biotic neighborhood and habitat heterogeneity on seedling survival over two years.
Important findings Our results showed that both biotic neighborhood and habitat heterogeneity had significant effects on the seedling survival at community level. The local environment suitable for the adult growth was also suitable for seedling survival. The soil moisture and soil available nitrogen exhibited significant positive effects on seedling survival. On the other hand, seedling density had significant negative effects on seedling survival due to the individual competition. Particularly, we found significant negative density-dependent effects on seedling survival which was caused by conspecific adult and seedling neighbors. As expected, with the increasing of seedling survival age, the habitat heterogeneity became more important on seedling survival. These results suggest that both local biotic neighborhood and habitat heterogeneity drive seedling survival in this temperate forest, and their relative importance varies with different seedling age classes and species traits. 相似文献
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基于长白山次生针阔混交林样地, 以520个1 m × 1 m幼苗样方中胸径小于1 cm的乔木幼苗为研究对象, 选取2013年和2014年的幼苗调查数据, 运用广义线性混合模型(GLMM)分析了生物邻体和生境异质性对幼苗存活的影响, 探讨了次生针阔混交林幼苗存活影响因素及物种共存机制。结果表明: (1)适宜大树生长的局域生境同样也适宜幼苗的存活, 幼苗存活率与土壤含水量和有效氮等土壤养分显著正相关。(2)幼苗个体之间存在明显的竞争, 较多的幼苗邻体显著降低幼苗的存活率。同种大树邻体和同种幼苗邻体与幼苗存活显著负相关, 表明存在负密度制约效应。(3)随着幼苗年龄的增加, 生境异质性对幼苗存活的影响逐渐增大。该研究证实了密度制约效应和生境异质性对幼苗存活有着重要影响, 其相对重要性随着幼苗年龄级、功能群以及物种种类而变化。 相似文献
7.
Lei Chen Xiangcheng Mi Liza S. Comita Liwen Zhang Haibao Ren Keping Ma 《Ecology letters》2010,13(6):695-704
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Yan Yan Chunyu Zhang Yuxi Wang Xiuhai Zhao Klaus von Gadow 《Ecology and evolution》2015,5(19):4287-4299
Negative density dependence (NDD) and niche partitioning have been perceived as important mechanisms for the maintenance of species diversity. However, little is known about their relative contributions to seedling survival. We examined the effects of biotic and abiotic neighborhoods and the variations of biotic neighborhoods among species using survival data for 7503 seedlings belonging to 22 woody species over a period of 2 years in three different forest types, a half‐mature forest (HF), a mature forest (MF), and an old‐growth forest (OGF), each of these representing a specific successional stage in a temperate forest ecosystem in northeastern China. We found a convincing evidence for the existence of NDD in temperate forest ecosystems. The biotic and abiotic variables affecting seedlings survival change with successional stage, seedling size, and age. The strength of NDD for the smaller (<20 cm in height) and younger seedlings (1–2 years) as well as all seedlings combined varies significantly among species. We found no evidence that a community compensatory trend (CCT) existed in our study area. The results of this study demonstrate that the relative importance of NDD and habitat niche partitioning in driving seedling survival varies with seedling size and age and that the biotic and abiotic factors affecting seedlings survival change with successional stage. 相似文献
10.
Classical tree neighborhood models use size variables acting at point distances. In a new approach here, trees were spatially extended as a function of their crown sizes, represented impressionistically as points within crown areas. Extension was accompanied by plasticity in the form of crown removal or relocation under the overlap of taller trees. Root systems were supposedly extended in a similar manner. For the 38 most abundant species in the focal size class (10–<100 cm stem girth) in two 4‐ha plots at Danum (Sabah), for periods P1 (1986–1996) and P2 (1996–2007), stem growth rate and tree survival were individually regressed against stem size, and neighborhood conspecific (CON) and heterospecific (HET) basal areas within incremented steps in radius. Model parameters were critically assessed, and statistical robustness in the modeling was set by randomization testing. Classical and extended models differed importantly in their outcomes. Crown extension weakened the relationship of CON effect on growth versus plot species’ abundance, showing that models without plasticity overestimated negative density dependence. A significant negative trend of difference in CON effects on growth (P2−P1) versus CON or HET effect on survival in P1 was strongest with crown extension. Model outcomes did not then support an explanation of CON and HET effects being due to (asymmetric) competition for light alone. An alternative hypothesis is that changes in CON effects on small trees, largely incurred by a drought phase (relaxing light limitation) in P2, and following the more shaded (suppressing) conditions in P1, were likely due to species‐specific (symmetric) root competition and mycorrhizal processes. The very high variation in neighborhood composition and abundances led to a strong “neighborhood stochasticity” and hence to largely idiosyncratic species’ responses. A need to much better understand the roles of rooting structure and processes at the individual tree level was highlighted. 相似文献
11.
Maíra Blumer Fatoretto Rafael de Andrade Moral Clarice Garcia Borges Demétrio Christopher Silva de Pádua Vinicius Menarin Víctor Manuel Arévalo Rojas 《Biocontrol Science and Technology》2018,28(11):1034-1053
ABSTRACTProportion data from dose-response experiments are often overdispersed, characterised by a larger variance than assumed by the standard binomial model. Here, we present different models proposed in the literature that incorporate overdispersion. We also discuss how to select the best model to describe the data and present, using R software, specific code used to fit and interpret binomial, quasi-binomial, beta-binomial, and binomial-normal models, as well as to assess goodness-of-fit. We illustrate applications of these generalized linear models and generalized linear mixed models with a case study from a biological control experiment, where different isolates of Isaria fumosorosea (Hypocreales: Cordycipitaceae) were used to assess which ones presented higher resistance to UV-B radiation. We show how to test for differences between isolates and also how to statistically group isolates presenting a similar behaviour. 相似文献
12.
Hans‐Peter Piepho 《Biometrical journal. Biometrische Zeitschrift》2019,61(4):860-872
Extensions of linear models are very commonly used in the analysis of biological data. Whereas goodness of fit measures such as the coefficient of determination (R2) or the adjusted R2 are well established for linear models, it is not obvious how such measures should be defined for generalized linear and mixed models. There are by now several proposals but no consensus has yet emerged as to the best unified approach in these settings. In particular, it is an open question how to best account for heteroscedasticity and for covariance among observations present in residual error or induced by random effects. This paper proposes a new approach that addresses this issue and is universally applicable for arbitrary variance‐covariance structures including spatial models and repeated measures. It is exemplified using three biological examples. 相似文献
13.
幼苗是植物生活史中最脆弱的阶段,对幼苗存活影响因子的分析有助于我们更清楚的了解森林群落的天然更新机制。利用广义线性混合模型（GLMM）对八大公山常绿落叶阔叶混交林中影响幼苗存活的主要生物与非生物因子进行了研究。结果表明：（1）在群落水平上,幼苗存活与生物因子中的同种幼苗密度呈显著负相关,与非生物因子中的冠层开阔度呈显著正相关;（2）从年龄上看,4年生以下龄级的幼苗存活更容易受到同种幼苗密度的影响,与同种幼苗密度呈显著负相关;4年生及其以上的幼苗存活则主要受非生物因子影响;（3）从生活型上看,相对于常绿物种,落叶物种的幼苗存活率更容易受到同种幼苗密度的影响,也与冠层开阔度呈正相关;（4）在物种水平上,生物因子与非生物因子对不同物种幼苗存活率的影响也不相同。其中,宜昌润楠（Machilus ichangensis Rehd.et Wils.）的存活率与冠层开阔度呈正相关;薄叶山矾（Symplocos anomala Brand）幼苗的存活率与同种幼苗密度、异种大树胸高断面积、林冠开阔度、坡向均呈显著负相关,而与异种幼苗密度和海拔呈显著正相关。本研究表明影响幼苗存活的因子是多样的,而且不是随机发生的。在不同水平上影响幼苗存活的因子不同。 相似文献
14.
Relative Survival is the ratio of the overall survival of a group of patients to the expected survival for a demographically similar group. It is commonly used in disease registries to estimate the effect of a particular disease when the true cause of death is not reliably known. Regression models for relative survival have been described and we extend these models to allow for clustered responses by embedding them into the class of Generalized linear mixed models (GLMM). The method is motivated and demonstrated by a data set from the HALLUCA study, an epidemiological study which investigated provision of medical care to lung cancer patients in the region of Halle in the eastern part of Germany. 相似文献
15.
Modeling individual heterogeneity in capture probabilities has been one of the most challenging tasks in capture–recapture studies. Heterogeneity in capture probabilities can be modeled as a function of individual covariates, but correlation structure among capture occasions should be taking into account. A proposed generalized estimating equations (GEE) and generalized linear mixed modeling (GLMM) approaches can be used to estimate capture probabilities and population size for capture–recapture closed population models. An example is used for an illustrative application and for comparison with currently used methodology. A simulation study is also conducted to show the performance of the estimation procedures. Our simulation results show that the proposed quasi‐likelihood based on GEE approach provides lower SE than partial likelihood based on either generalized linear models (GLM) or GLMM approaches for estimating population size in a closed capture–recapture experiment. Estimator performance is good if a large proportion of individuals are captured. For cases where only a small proportion of individuals are captured, the estimates become unstable, but the GEE approach outperforms the other methods. 相似文献
16.
为探究高黎贡山中山湿性常绿阔叶林4 hm2内胸径(DBH) <1 cm的幼苗多度的关键影响因素,利用广义线性混合模型在群落水平和物种水平分析邻体密度和生境因子是否影响幼苗多度,制约强度是否因时间而异。结果显示：(1) 群落水平上的总物种幼苗多度与邻体密度和生境因子的相关性随时间增加;常见种幼苗多度与异种大树邻体密度正相关呈显著增加趋势,与环境因子无相关性;稀有种幼苗多度与邻体密度和环境因子均无显著性。(2) 在物种水平上,聚果九节Psychotria morindoides幼苗多度仅在2022年与海拔和凸度分别呈边缘显著负相关和正相关;邻体效应和环境异种性对针齿铁仔Myrsine semiserrata幼苗多度在2020～2023年有显著正效应,表明存在正密度制约效应;在较高林冠开度、海拔和土壤含钾生境下,幼苗多度较高;而铜绿山矾Symplocos stellaris var. aenea幼苗多度在4个时段与邻体密度和环境因子均无显著相关性。研究表明,高黎贡山幼苗多度格局同时受到邻体密度和生境因子影响,这种影响强度在不同水平、物种和时空格局中差异显著,影响因素的相对重要性维持着该样地群落多样性。 相似文献
17.
We introduce a new statistical computing method, called data cloning, to calculate maximum likelihood estimates and their standard errors for complex ecological models. Although the method uses the Bayesian framework and exploits the computational simplicity of the Markov chain Monte Carlo (MCMC) algorithms, it provides valid frequentist inferences such as the maximum likelihood estimates and their standard errors. The inferences are completely invariant to the choice of the prior distributions and therefore avoid the inherent subjectivity of the Bayesian approach. The data cloning method is easily implemented using standard MCMC software. Data cloning is particularly useful for analysing ecological situations in which hierarchical statistical models, such as state-space models and mixed effects models, are appropriate. We illustrate the method by fitting two nonlinear population dynamics models to data in the presence of process and observation noise. 相似文献
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Liping Wang;Junjie Wu;Yong Chai;Jiwen Sun;Xiaoli Yu;Zhe Feng;Fengxian Chen; 《Ecology and evolution》2024,14(7):e11675
Density dependence and habitat filtering have been proposed to aid in understanding community assembly and species coexistence. Phylogenetic relatedness between neighbors was used as a proxy for assessing the degree of ecological similarity among species. There are different conclusions regarding the neighborhood effect in previous studies with different phylogenetic indices or at different spatiotemporal scales. However, the effects of density dependence, neighbor phylogenetic relatedness, and habitat filtering on seedling survival with different phylogenetic indices or at different temporal and spatial scales are poorly understood. We monitored 916 seedlings representing 56 woody plant species within a 4-ha forest dynamics plot for 4 years (from 2020 to 2023) in a subtropical mid-mountain moist evergreen broad-leaved forest in the Gaoligong Mountains, Southwestern China. Using generalized linear mixed models, we tested whether and how four phylogenetic indices: total phylogenetic distance (TOTPd), average phylogenetic distance (AVEPd), relative average phylogenetic distance (APd′), and relative nearest taxon phylogenetic distance (NTPd′), three temporals (1, 2, and 3 years), and spatial scales (1, 2, and 4 ha) affect the effect of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival. We found evidence of the effect of phylogenetic density dependence in the 4-ha forest dynamics plot. The effects of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival were influenced by phylogenetic indices and temporal and spatial scales. The effects of phylogenetic density dependence and habitat filtering on seedling survival were more conspicuous only at 1-year intervals, compared with those at 2- and 3-year intervals. We did not detect any effects of neighborhood or habitat factors on seedling survival at small scales (1 and 2 ha), although these effects were more evident at the largest spatial scale (4 ha). These findings highlight that the effects of local neighborhoods and habitats on seedling survival are affected by phylogenetic indices as well as temporal and spatial scales. Our study suggested that phylogenetic index APd′, shortest time scale (1 year), and largest spatial scales (4 ha) were suitable for neighborhood studies in a mid-mountain moist evergreen broad-leaved forest in Gaoligong Mountains. Phylogenetic indices and spatiotemporal scales have important impacts on the results of the neighborhood studies. 相似文献
20.
Uriarte M Swenson NG Chazdon RL Comita LS John Kress W Erickson D Forero-Montaña J Zimmerman JK Thompson J 《Ecology letters》2010,13(12):1503-1514
Ecology Letters (2010) 13: 1503-1514 ABSTRACT: The phylogenetic structure and distribution of functional traits in a community can provide insights into community assembly processes. However, these insights are sensitive to the spatial scale of analysis. Here, we use spatially explicit, neighbourhood models of tree growth and survival for 19 tree species, a highly resolved molecular phylogeny and information on eight functional traits to quantify the relative efficacy of functional similarity and shared ancestry in describing the effects of spatial interactions between tree species on demographic rates. We also assess the congruence of these results with observed phylogenetic and functional structure in the neighbourhoods of live and dead trees. We found strong support for models in which the effects of spatial neighbourhood interactions on tree growth and survival were scaled to species-specific mean functional trait values (e.g., wood specific gravity, leaf succulence and maximum height) but not to phylogenetic distance. The weak phylogenetic signal in functional trait data allowed us to independently interpret the static neighbourhood functional and phylogenetic patterns. We observed greater functional trait similarity in the neighbourhoods of live trees relative to those of dead trees suggesting that environmental filtering is the major force structuring this tree community at this scale while competitive interactions play a lesser role. 相似文献