Effects of density dependence in a temperate forest in northeastern China

Yao, Jie; Zhang, Xinna; Zhang, Chunyu; Zhao, Xiuhai; Gadow, Klaus von

doi:10.1038/srep32844

Cited by 26 publications

(20 citation statements)

References 52 publications

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“…A reduction in seedling performance, productivity, and survival with increasing seedling density as evidenced in the Main Experiment would then at least partly be the result of competitive effects for space and other resources (Yao et al. , Lin et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…A second scenario, however, might be that density-dependent effects encountered were additionally brought about by intraspecific competition and not necessarily by JC effects only. A reduction in seedling performance, productivity, and survival with increasing seedling density as evidenced in the Main Experiment would then at least partly be the result of competitive effects for space and other resources (Yao et al 2016, Lin et al 2017). In the present study, this interpretation could be particularly valid for seedling performance and productivity, for both of which we found similar effects of significant reduction with increasing density of conspecific recruits in the Main Experiment and in the Common Garden Experiment.…”

Section: Density Dependencementioning

confidence: 93%

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Janzen‐Connell effects in a forest BEF experiment: Strong distance‐dependent seedling establishment of multiple species

Bruelheide

Erfmeier

2019

Ecology

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Citation: Germany, M. S., H. Bruelheide, and A. Erfmeier. 2019. Janzen-Connell effects in a forest BEF experiment: Strong distance-dependent seedling establishment of multiple species.Abstract. The Janzen-Connell (JC) hypothesis is a major ecological explanation for high species richness, in particular in tropical forest ecosystems. Central components of the JC hypothesis are noncompetitive effects of distance and density dependence, two drivers that contribute independently to species coexistence, but are ultimately linked in the field. However, although numerous studies provide evidence for either distance-or density-dependent effects based on observational data, experimental testing of simultaneous and interactive effects of distance and density has rarely been conducted, especially in a comprehensive multispecies approach. Here, we make use of the forest Biodiversity-Ecosystem Functioning project (BEF) -China to estimate distance-and density-dependent effects in a reciprocal tree seedling transplant experiment of 11 tree species. We deployed 13,490 juveniles of all 11 species in their own (home) and in all foreign monocultures (away), as well as at three different levels of planting density, thereby testing for distance and density effects, respectively. In addition, to quantify the amount to which density effects were brought about by potential additional effects of intraspecific competition, we set up a common garden experiment with different levels of planting density, where an additional "shadow" treatment controlled for effects of canopy shading. Although the "away" and "high-density" treatments significantly impaired the performance and productivity of seedlings, leaf damage and survival was exclusively affected by either the home/away or the density treatment, respectively. Negative density-dependent effects on leaf damage were less pronounced in the "home" treatment, showing that the effects were not additive. In addition, results obtained in the Common Garden Experiment showed that negative effects of high density may be also brought about by intraspecific competition as an alternative density-responsive mechanism and less by true JC effects. Overall, our results provide strong support on a multispecies basis for the influence of host-specific effects already operating in early stages of a forest plantation. However, they also emphasize the need to account appropriately for potential additional densityresponsive mechanisms such as intraspecific competition or microenvironmental conditions when addressing the role of JC effects for species coexistence.

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Section: Discussionmentioning

confidence: 99%

Section: Density Dependencementioning

confidence: 93%

Janzen‐Connell effects in a forest BEF experiment: Strong distance‐dependent seedling establishment of multiple species

Bruelheide

Erfmeier

2019

Ecology

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“…Although such inferences are possible, they are usually weak and require an extra degree of caution relative to inferences from dynamic experimental studies (Damgaard & Weiner 2017a) and appropriate statistical techniques (e.g. Bagchi et al 2011;Yao et al 2016). A major problem is that different processes and different combinations of processes can generate similar spatial patterns, which makes it difficult to distinguish between them (Detto & Muller-Landau 2013;Damgaard & Weiner 2017b;H€ ulsmann & Harting 2018).…”

Section: Static Spatial Patternsmentioning

confidence: 99%

Bias in the detection of negative density dependence in plant communities

et al. 2019

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Regression dilution is a statistical inference bias that causes underestimation of the strength of dependency between two variables when the predictors are error‐prone proxies (EPPs). EPPs are widely used in plant community studies focused on negative density‐dependence (NDD) to quantify competitive interactions. Because of the nature of the bias, conspecific NDD is often overestimated in recruitment analyses, and in some cases, can be erroneously detected when absent. In contrast, for survival analyses, EPPs typically cause NDD to be underestimated, but underestimation is more severe for abundant species and for heterospecific effects, thereby generating spurious negative relationships between the strength of NDD and the abundances of con‐ and heterospecifics. This can explain why many studies observed rare species to suffer more severely from conspecific NDD, and heterospecific effects to be disproportionally smaller than conspecific effects. In general, such species‐dependent bias is often related to traits associated with likely mechanisms of NDD, which creates false patterns and complicates the ecological interpretation of the analyses. Classic examples taken from literature and simulations demonstrate that this bias has been pervasive, which calls into question the emerging paradigm that intraspecific competition has been demonstrated by direct field measurements to be generally stronger than interspecific competition.

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“…The Janzen-Connell hypothesis (Janzen 1970;Connell 1971), for example, proposes that elevated numbers of specialist natural enemies, such as herbivores and pathogens, maintain diversity in plant communities. They reduce the survival rates of conspecific seeds and seedlings located close to reproductive adults or in areas of high conspecific density (Comita et al 2014) leading to elevated conspecific self-thinning (Yao et al 2016), i.e. a progressive decline in density in a population of growing individuals of the same species (Begon et al 2006, p. 157).…”

Section: Introductionmentioning

confidence: 99%

“…a progressive decline in density in a population of growing individuals of the same species (Begon et al 2006, p. 157). An important effect of the Janzen-Connell hypothesis is the negative density/distance dependence that occurs when nearby conspecific plants negatively affect performance through mechanisms such as intraspecific competition and pest facilitation (Wills et al 1997;Wright 2002;Piao et al 2013;Yao et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Global woodland structure from local interactions: new nearest-neighbour functions for understanding the ontogenesis of global forest structure

2020

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Background: A number of hypotheses and theories, such as the Janzen-Connell hypothesis, have been proposed to explain the natural maintenance of biodiversity in tropical and temperate forest ecosystems. However, to date the details of the processes behind this natural maintenance are still unclear. Recently two new nearest-neighbour characteristics were proposed and in this paper we demonstrate how they can contribute to a better understanding of the ontogenesis of global forest structure from localised neighbourhoods. Methods: We applied the new species and size segregation functions together with appropriate test procedures to four example woodland data sets from China at Daqingshan, Jiaohe, Jiulongshan and Xiaolongshan forest regions. In addition we quantified the morphology of the new characteristics and modelled a neighbourhood allometric coefficient linking the two functions. Results: The results revealed quite different species segregation patterns with both conspecific and heterospecific attraction. We found these to be generally matched by equivalent size segregation patterns of attraction of similar and different sizes. It was straightforward to model the size segregation function from the knowledge of the species segregation function by estimating a neighbourhood allometric coefficient. Conclusions: The new characteristics have helped to quantify the extent and rate of decline of neighbourhood interactions in terms of spatial species and size diversity. Through the allometric neighbourhood coefficient the analysis highlighted once more how closely related species and size segregation are, thus supporting the minglingsize hypothesis. Using both a traditional and a restricted random-labelling test has provided a valuable tool for understanding the exact nature of species-mingling and size-inequality relationships.

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Effects of density dependence in a temperate forest in northeastern China

Cited by 26 publications

References 52 publications

Janzen‐Connell effects in a forest BEF experiment: Strong distance‐dependent seedling establishment of multiple species

Janzen‐Connell effects in a forest BEF experiment: Strong distance‐dependent seedling establishment of multiple species

Bias in the detection of negative density dependence in plant communities

Global woodland structure from local interactions: new nearest-neighbour functions for understanding the ontogenesis of global forest structure

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