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1.
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
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密度制约对宝天曼落叶阔叶林锐齿栎死亡前后分布格局的影响 总被引：1，自引：0，他引：1
为了在温带和亚热带的过渡带中验证森林树木死亡是否受密度制约的影响, 我们在宝天曼国家级自然保护区选择1个100 m×100 m的暖温带落叶阔叶林样地, 用双变量函数g(r)(the pair-correlation function)研究了锐齿栎(Quercus aliena var. acuteserrata)死亡前(活树和枯木统称为死亡前树木)和死亡后(活树为死亡后树木)的分布格局。把样地中的锐齿栎分为幼树(1 cm ≤ DBH<10 cm)、小树(10 cm ≤ DBH<20 cm)和成年树(DBH≥20 cm)3个不同的生长阶段来研究密度制约对空间分布格局的影响机制。结果表明: (1)死亡前锐齿栎在r>5 m尺度呈聚集分布, 死亡后幼树(1 cm≤DBH<10 cm)和成年树(DBH≥20 cm)在1-25 m尺度呈现随机分布, 死亡后小树(10 cm≤DBH< 20 cm)在r<1.5 m和2.5-4.5 m的尺度为随机分布, 在r>5 m的尺度呈聚集分布; (2)采用随机标签零模型和案例-对照设计的方法, 排除生境异质性影响后, 将幼树和小树的分布格局作为案例, 将成年树的分布格局作为对照, 并代表生境异质性的作用, 通过小径级树木与成年树分布格局的对比发现, 密度制约效应对死亡前后的锐齿栎分布格局均具有影响; (3)幼树和小树在成年树周围的分布死亡前为显著聚集分布格局, 死亡后剩余树木的聚集强度下降; 随着与成年树之间距离的增加, 死亡后的幼树(仅包括现存的活树)逐渐向随机分布格局演替。本研究初步表明锐齿栎空间格局受生境异质性的影响并呈现出显著的聚集效应, 排除生境异质性影响后, 锐齿栎死亡前后的空间格局受到密度制约的影响, 这一结果为Janzen-Connell假说提供了支持。 相似文献
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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
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以吉林蛟河次生针阔混交林42 hm 2固定监测样地中209个幼苗监测站内的乔木幼苗为研究对象, 基于2016和2017年幼苗调查数据, 探究幼苗物种组成、数量动态等特征, 并运用广义线性混合效应模型分析了幼苗密度与生物邻体及其生境因素的相关性。结果表明: (1)该样地内所有幼苗监测站共调查到幼苗4 245株, 分属10科12属18种, 新生幼苗的数量在物种和调查年份间均有明显差异, 其中水曲柳(Fraxinus mandschurica)和紫椴(Tilia amurensis)幼苗表现出大量出生和死亡的动态特征。(2)群落水平上, 幼苗密度与局域同种成体胸高断面积之和、土壤全磷和有效钾等养分含量显著正相关, 适宜大树生长的生境同样适宜幼苗的生长。(3)水曲柳幼苗密度的影响因素与群落水平一致, 红松(Pinus koraiensis)存在明显的生境偏好, 在湿度较小、土壤全磷、有效氮和有效磷含量较低的生境中密度更高。相对于多年生幼苗, 同种成年邻体对当年生幼苗密度影响更加显著。该研究证实了扩散限制和生境过滤共同影响幼苗密度格局, 生物邻体和生境异质性的相对重要性随幼苗物种种类和年龄级变化。 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
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为探讨木本植物幼苗动态的影响因素,从功能性状多样性、系统发育多样性和环境过滤3个方面分析其对幼苗平均存活率和平均生长率的影响及其在不同幼苗密度样地间的动态变化。在云南苍山西坡4个不同幼苗密度的样地平台,设置了256个幼苗样方,收集了2020—2022年3年的幼苗数据并结合线性混合模型进行分析。结果表明,幼苗平均存活率受到功能性状多样性和系统发育多样性的影响,在低幼苗密度样地中功能性状多样性和系统发育多样性对幼苗平均存活具有显著正作用。幼苗平均生长率主要受到系统发育多样性和环境过滤的影响,在高幼苗密度样地中系统发育多样性呈显著负作用,低样方坡度和高土壤湿度是幼苗生长的关键因素。标准化系统发育多样性指数在低幼苗密度样地中较高,而功能分散性指数在高幼苗密度样地中较高。这为幼苗动态的理解和预测提供了新的视角和方法,也为森林的恢复和保护提供了实践指导。 相似文献
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本研究中用成年东方田鼠不同时间不同密度笼养后（笼内雌雄各半）,低密度配对饲养,观察各阶段东方田鼠繁殖指标的差异。试鼠144只,处理时分为LL（低密度长时间）（2只/笼,共20笼,90d）、HL（高密度长时间）（8只/笼,共5笼,90d）、HM（高密度中等时间）（8只/笼,共4笼,20d）与HS（高密度短时间）（8只/笼,共4笼,10d）4组。处理后在低密度条件下观察繁殖情况（胎仔数、怀孕率、分娩频率以及产仔间隔等）,直至180 d。实验数据按时间划分为3个部分统计：0~90 d为第一阶段(不同密度处理期),90~109 d为过渡阶段（处理后的过渡期）,109 d以后为第二阶段（正常低密度配对繁殖期）。结果表明：经过长时间高密度处理后,平均产仔数显著减少,组间平均分娩频率无显著差异。怀孕率由HL组到HM组,再到LL和HS组显著增加。在第一阶段,除了LL组之外,其余各组都未发现繁殖。过渡阶段的怀孕率组间差异显著,LL组以及HM组显著高于HL组。第二阶段的怀孕率以及胎仔数的组间差异显著,都为LL、HS两组较高,HL、HM两组较低。平均分娩频率、平均胎仔数以及产仔间隔各组间无显著差异。结论：不同持续时间的密度效应有较大差别。对于东方田鼠,20d的高密度处理相比于10d更能对其繁殖起到抑制作用。恢复低密度后,存在种群的迟滞性密度制约。 相似文献
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密度制约机制对于维护生物多样性有非常重要的作用。随着对密度制约机制的深入研究, 人们逐渐认识到: 不仅在种内存在密度制约效应, 亲缘关系相近的物种之间也可能表现出密度制约效应。Webb在2000年提出的NRI (净种间亲缘关系指数)、NTI (净最近种间亲缘关系指数)考虑了比较全面的谱系信息, 获得了广泛的应用。该文采用NRI、NTI来代表种间关系, 并用Logistic回归模型来分析了谱系因子对浙江省开化县古田山自然保护区24 hm2永久监测样地中501个幼苗样方死亡率的影响。通过对6次幼苗调查数据的分析表明: 不仅相同物种密度对于幼苗的死亡率有显著影响, 当密度达到一定水平时, 谱系因子同样也对幼苗的死亡率有显著影响——苗区中个体间的亲缘关系越近, 幼苗个体的死亡率越高。 相似文献
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为了研究种群密度对东方田鼠(Microtus fortis)内脏器官(心、肺、肝、脾、肾、肾上腺)的影响,随机选取稳定的同性别饲养群的成年东方田鼠258只,雌雄各半,分A组30笼:2只/笼,B组15笼:4只/笼,C组11笼:6只/笼和D组9笼:8只/笼共4个密度组,饲养90d后解剖,取内脏器官,称重以及测定血浆皮质醇浓度并进行比较。结果表明:在相同密度内,除B组孕鼠的肝脏重较未孕鼠有极显著差异外,其它各组(A、C、D)怀孕鼠和未孕鼠的各内脏器官重均无显著差异。在不同密度间,怀孕鼠的肝脏重有极显著差异,孕鼠与未孕鼠的其余各内脏器官均无显著差异;雄鼠的肺重、脾脏重和雌鼠的脾脏重、肾上腺重差异显著,其余各器官重在不同密度间虽未表现出显著差异,但均具有随着密度增加而器官重量逐渐增大的趋势。各个密度组中的雄性个体血浆皮质醇浓度分别显著高于雌性,且差异显著;同一性别比较,不同密度间的雌性个体血浆皮质醇浓度差异不显著,而雄性个体血浆皮质醇浓度差异则显著,随密度增大而明显增加。可见高密度压力导致内脏器官重量上有所调节,但不同脏器受密度因素影响程度不同。 相似文献
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Density dependence and habitat heterogeneity have been recognized as important driving mechanisms that shape the patterns of seedling survival and promote species coexistence in species‐rich forests. In this study, we evaluated the relative importance of density dependence by conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival in the Lienhuachih (LHC) Forest, a subtropical, evergreen forest in central Taiwan. Age‐specific effects of different variables were also studied. We monitored the fates of 1,642 newly recruited seedlings of woody plants within a 25‐ha Forest Dynamics Plot for 2 years. The effects of conspecific, heterospecific, and phylogenetically related neighbors and habitat heterogeneity on seedling survival were analyzed by generalized linear mixed models. Our results indicated that conspecific negative density dependence (CNDD) had a strong impact on seedling survival, and the effects of CNDD increased with seedling age. Heterospecific positive density dependence (HPDD) and phylogenetic positive density dependence (PPDD) had a significant influence on the survival of seedlings, and stronger HPDD and PPDD effects were detected for older seedlings. Furthermore, seedling survival differed among habitats significantly. Seedling survival was significantly higher in the plateau, high‐slope, and low‐slope habitats than in the valley. Overall, our results suggested that the effects of CNDD, HPDD, PPDD, and habitat heterogeneity influenced seedling survival simultaneously in the LHC subtropical forest, but their relative importance varied with seedling age. Such findings from our subtropical forest were slightly different from tropical forests, and these contrasting patterns may be attributed to differences in abiotic environments. These findings highlight the importance to incorporate phylogenetic relatedness, seedling age, and habitat heterogeneity when investigating the impacts of density dependence on seedling survival that may contribute to species coexistence in seedling communities. 相似文献
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Luis Darcy Verde Arregoitia Simon P. Blomberg Diana O. Fisher 《Proceedings. Biological sciences / The Royal Society》2013,280(1765)
Phylogenetic information is becoming a recognized basis for evaluating conservation priorities, but associations between extinction risk and properties of a phylogeny such as diversification rates and phylogenetic lineage ages remain unclear. Limited taxon-specific analyses suggest that species in older lineages are at greater risk. We calculate quantitative properties of the mammalian phylogeny and model extinction risk as an ordinal index based on International Union for Conservation of Nature Red List categories. We test for associations between lineage age, clade size, evolutionary distinctiveness and extinction risk for 3308 species of terrestrial mammals. We show no significant global or regional associations, and three significant relationships within taxonomic groups. Extinction risk increases for evolutionarily distinctive primates and decreases with lineage age when lemurs are excluded. Lagomorph species (rabbits, hares and pikas) that have more close relatives are less threatened. We examine the relationship between net diversification rates and extinction risk for 173 genera and find no pattern. We conclude that despite being under-represented in the frequency distribution of lineage ages, species in older, slower evolving and distinct lineages are not more threatened or extinction-prone. Their extinction, however, would represent a disproportionate loss of unique evolutionary history. 相似文献
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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
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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
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The specificity of the interactions between plants and their consumers varies considerably. The evolutionary and ecological factors underlying this variation are unclear. Several potential explanatory factors vary with latitude, for example plant species richness and the intensity of herbivory. Here, we use comparative phylogenetic methods to test the effect of latitude on host range in scale insects. We find that, on average, scale insects that occur in lower latitudes are more polyphagous. This result is at odds with the general pattern of greater host-plant specificity of insects in the tropics. We propose that this disparity reflects a high cost for host specificity in scale insects, stemming from unusual aspects of scale insect life history, for example, passive wind-driven dispersal. More broadly, the strong evidence for pervasive effects of geography on host range across insect groups stands in stark contrast to the weak evidence for constraints on host range due to genetic trade-offs. 相似文献
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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
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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
18.
Simple corrected density indices (CDIs) have been used to measure reductions in pest density in fields. In the contemporary pesticide registration system, few comprehensive statistical frameworks are available that can integrate multiple datasets to evaluate how pesticidal effects are influenced by the products' properties such as mixing multiple active ingredients and possession of systemic ability. In this study, we provide a statistical framework for evaluating pesticide efficacy from multiple field trials and applying it to contemporary pesticides. In this framework, we extended the conventional CDI to a generalized linear mixed model (GLMM), which we applied to a dataset of the pesticide registration test in Japan (n = 758). The estimated mortality of a single active ingredient in reducing pest density is 88.0%, indicating the registered pesticide satisfies the “effective” criterion (roughly 70–95%) under the current pesticide registration system in Japan. Although systemic ability additionally reduced pest population to 55.5% of the post-treatment densities, the addition of active ingredients scarcely enhances efficacy (reducing population to 74.6%), suggesting that the pesticide design resulted in broadening the spectrum of target species rather than increasing toxicity. 相似文献
19.
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