scholarly journals The Post-Fire Assembly Processes of Tree Communities Based on Spatial Analysis of a Sierra Nevada Mixed-Conifer Forest

Fire ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 72
Author(s):  
Jelveh Tamjidi ◽  
James A. Lutz
Keyword(s):  
Correlation Function ◽  
Poisson Process ◽  
Density Dependence ◽  
Spatial Patterns ◽  
Habitat Heterogeneity ◽  
Large Diameter ◽  
Dispersal Limitation ◽  
Abies Concolor ◽  
Pinus Lambertiana ◽  
Calocedrus Decurrens

Understanding the mechanisms underlying tree spatial arrangements may provide significant insights into the processes in the maintenance of species coexistence. We examined the potential role of habitat heterogeneity, dispersal limitation, negative density dependence, fire history, and unilateral intraspecific and interspecific interactions of adults on juveniles in shaping the spatial patterns of four dominant tree species (Abies concolor, Pinus lambertiana, Calocedrus decurrens, and Quercus kelloggii) after fire in the Yosemite Forest Dynamic Plot, California, USA. We used the univariate pair correlation function and implemented three point pattern processes (homogeneous Poisson process, inhomogeneous Poisson process, and homogeneous Thomas process) to evaluate the potential contributions of habitat filtering and dispersal limitation. We used a bivariate null model to evaluate unilateral intraspecific and interspecific interactions of adults on juveniles. We also used the pairwise correlation function to investigate the spatial patterns of density dependence. To understand the effect of fire, we used the univariate pair correlation function to investigate pattern changes during the six years following fire. We compared spatial pattern changes in both sprouting species (Quercus kelloggii) and seeding species (Abies concolor), and also examined the changes in patterns of large-diameter individuals of Abies concolor, Pinus lambertiana, and Calocedrus decurrens in 2013 (pre-fire), 2016 (two years post-fire), and 2019. Comparing the contributions of the homogeneous Thomas process and the inhomogeneous Poisson process at different spatial scales showed the importance of dispersal limitation and habitat heterogeneity at finer scales (0 m to 5 m) and coarser scales (5 m to 60 m), respectively, which suggests that the joint effects of dispersal limitation and habitat heterogeneity contribute to the spatial patterns of these three dominant tree species. Furthermore, the results showed that the young individuals of Abies concolor and Pinus lambertiana were more commonly found around the conspecific adults. Juvenile regeneration to the 1 cm diameter threshold was highly aggregated following the fire. Large-diameter trees of Abies concolor, Pinus lambertiana, and Calocedrus decurrens generally did not exhibit patterns different from complete spatial randomness (Calocedrus decurrens), or displayed only slight aggregation (Abies concolor and Pinus lambertiana). In addition, Abies concolor and Pinus lambertiana showed positive and negative conspecific density dependence in the immediate post-fire period, respectively.

Effects of density dependence on the spatial patterns ofQuercus alienavar.acuteserratatrees in deciduous broad-leaved forest in the Baotianman Nature Reserve, central China

2014 ◽  
Vol 22 (4) ◽  
pp. 449 ◽  
Author(s):  
Wang Ting ◽  
Ren Siyuan ◽  
Yuan Zhiliang ◽  
Zhu Yan ◽  
Pan Na ◽  
...  
Keyword(s):  
Density Dependence ◽  
Spatial Patterns ◽  
Nature Reserve ◽  
Central China ◽  
Broad Leaved Forest ◽  
Leaved Forest ◽  
Effects Of Density

scholarly journals Spatial Patterns in Different Stages of Regeneration after Clear-Cutting of a Black Locust Forest in Central China

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1066
Author(s):  
Zhang ◽  
Shen ◽  
Yang ◽  
Ma ◽  
Duan ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Stand Structure ◽  
Robinia Pseudoacacia ◽  
Spatial Relation ◽  
Dispersal Limitation ◽  
Central China ◽  
Variance Gamma ◽  
Clear Cutting ◽  
Variance Gamma Process ◽  
Underlying Mechanisms

Estimating underlying mechanisms and dynamics from observed tree patterns can provide guidance for plantation management. Robinia pseudoacacia can reproduce via clonally produced ramets, leading to a complex distribution of stems. Three second generation plots and three third generation plots (each plot 50 m × 50 m) were established across a wide age range after clear-cutting in a Robinia pseudoacacia plantation in central China. We measured spatial coordinates, diameter at breast height (DBH) or diameter at basal stem, and heights of all recruits, as well as the coordinates and base diameter of all stumps, in six plots. The spatial pattern in different plots and the spatial relation between stumps and regenerations after clear-cutting were analyzed. To estimate the underlying processes of the observed patterns, we fitted Matérn and Variance-Gamma cluster processes to the observed dataset. The results revealed that the percentage of ramets from stumps decreasing with age in the two types of stands (from 40.4% to 30.1%, from 57.6% to 35.7%), and trees exhibited an aggregated distribution in all plots, but the degree of aggregation exhibited a decreasing trend with age, and aggregation occurred at different scale. Furthermore, a large proportion of ramets had their nearest neighbor at a short distance (<1 m) based on analysis of the nearest neighbour function. The bivariate analysis revealed that the spatial relation between stumps and ramets changed with age, and a repulsion trend was found between them in all the six plots. The Variance-Gamma process with covariate of Cartesian coordinates fitted the observed patterns better than others. The observed pattern was likely driven by root dispersal limitation, seed dispersal limitation, human disturbance, and intraspecific competition. Spatial patterns are important characteristics in forest stand structure, and understanding the pattern change and its underlying mechanisms could allow for better timing of artificial disturbances to optimize stand structure and promote stand growth.

Detecting density dependence from spatial patterns in a heterogeneous subtropical forest of central China

2015 ◽  
Vol 45 (6) ◽  
pp. 710-720 ◽  
Author(s):  
Yili Guo ◽  
Zhijun Lu ◽  
Qinggang Wang ◽  
Junmeng Lu ◽  
Yaozhan Xu ◽  
...  
Keyword(s):  
Population Structure ◽  
Density Dependence ◽  
Habitat Heterogeneity ◽  
Species Traits ◽  
Subtropical Forest ◽  
Species Level ◽  
Central China ◽  
Life Stages ◽  
Natural Forests ◽  
Level Variation

Accumulating evidence suggests that density dependence, whether at early or late life stages, is an important mechanism regulating plant population structure. However, the opposing effects of habitat heterogeneity and species-level variation might have confounded the prevalence of density dependence in natural forests. These compatible ideas were rarely considered simultaneously. In this study, we applied a spatial statistical technique to examine (i) the prevalence of density dependence at late life stages after controlling for habitat heterogeneity and (ii) the relationships between species traits and the strength of density dependence in a newly established, 25 ha subtropical mountain forest plot in central China. Of the 88 (75%) tree species analyzed, 66 were found to exhibit density dependence predominantly at very close distances among neighbors in the species-rich subtropical forest. In addition, the strength of density dependence was associated with species traits. Our findings identified strong density dependence among trees that had greater stature and were rarer. We concluded that density dependence was a prevalent mechanism for regulating the population structure of most tree species and both habitat heterogeneity and species-level variation played crucial roles in shaping the strength of density dependence in natural forests.

scholarly journals Relating the strength of density dependence and the spatial distribution of individuals

2019 ◽  
Author(s):  
Micah Brush ◽  
John Harte
Keyword(s):  
Density Dependence ◽  
Spatial Patterns ◽  
Binomial Distribution ◽  
Negative Binomial ◽  
Individual Species ◽  
Spatial Patterning ◽  
Random Placement ◽  
Negative Density Dependence ◽  
Underlying Mechanisms ◽  
Spatially Explicit Data

ABSTRACTSpatial patterns in ecology contain useful information about underlying mechanisms and processes. Although there are many summary statistics used to quantify these spatial patterns, there are far fewer models that directly link explicit ecological mechanisms to observed patterns easily derived from available data. We present a model of intraspecific spatial aggregation that quantitatively relates static spatial patterning to negative density dependence. Individuals are placed according to the colonization rule consistent with the Maximum Entropy Theory of Ecology (METE), and die with probability proportional to their abundance raised to a power α, a parameter indicating the degree of density dependence. Our model shows quantitatively and generally that increasing density dependence randomizes spatial patterning. α = 1 recovers the strongly aggregated METE distribution that is consistent with many ecosystems empirically, and as α → 2 our prediction approaches the binomial distribution consistent with random placement. In between our model predicts less aggregation than METE, but more than random placement. We additionally relate our mechanistic parameter α to the statistical aggregation parameter k in the negative binomial distribution, giving it an ecological interpretation in the context of density dependence. We use our model to analyze two contrasting datasets, a 50 ha tropical forest and a 64 m2 serpentine grassland plot. For each dataset, we infer α for individual species as well as a community α parameter. We find that α is generally larger in the tightly packed forest than the sparse grassland, and the degree of density dependence increases at smaller scales. These results are consistent with current understanding in both ecosystems, and we infer this underlying density dependence using only empirical spatial patterns. Our model can easily be applied to other datasets where spatially explicit data are available.

scholarly journals Evolution of positive and negative density-dependent dispersal

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141226 ◽  
Author(s):  
António M. M. Rodrigues ◽  
Rufus A. Johnstone
Keyword(s):  
Density Dependence ◽  
Habitat Heterogeneity ◽  
Temporal Stability ◽  
Ecological Factors ◽  
Positive Density ◽  
Density Dependent ◽  
High Dispersal ◽  
Variable Environments ◽  
Negative Density Dependence ◽  
Density Dependent Dispersal

Understanding the evolution of density-dependent dispersal strategies has been a major challenge for evolutionary ecologists. Some existing models suggest that selection should favour positive and others negative density-dependence in dispersal. Here, we develop a general model that shows how and why selection may shift from positive to negative density-dependence in response to key ecological factors, in particular the temporal stability of the environment. We find that in temporally stable environments, particularly with low dispersal costs and large group sizes, habitat heterogeneity selects for negative density-dependent dispersal, whereas in temporally variable environments, particularly with high dispersal costs and small group sizes, habitat heterogeneity selects for positive density-dependent dispersal. This shift reflects the changing balance between the greater competition for breeding opportunities in more productive patches, versus the greater long-term value of offspring that establish themselves there, the latter being very sensitive to the temporal stability of the environment. In general, dispersal of individuals out of low-density patches is much more sensitive to habitat heterogeneity than is dispersal out of high-density patches.

scholarly journals Spatial patterns and associations of tree species at different developmental stages in a montane secondary temperate forest of northeastern China

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11517
Author(s):  
Jia Liu ◽  
Xuejiao Bai ◽  
You Yin ◽  
Wenguang Wang ◽  
Zhiqiang Li ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Tree Species ◽  
Habitat Heterogeneity ◽  
Temperate Forest ◽  
Developmental Stages ◽  
Northeastern China ◽  
Point Pattern Analysis ◽  
Point Pattern ◽  
Secondary Forests ◽  
Neighborhood Competition

Background Secondary forests have become the major forest type worldwide. Research on spatial patterns and associations of tree species at different developmental stages may be informative in understanding the structure and dynamic processes of secondary forests. Methods In this study, we used point pattern analysis to analyze the spatial patterns and associations of tree species at seedling, sapling and adult stages in a 4ha plot in the montane secondary temperate forest of northeastern China. Results We found that species showed similar patterns at seedling, sapling and adult stages, and aggregation was the dominant pattern. The spatial patterns of tree species were mainly affected by habitat heterogeneity. In addition, the strength of positive or negative associated pattern among tree species would decrease with developmental stages, which attributed to neighborhood competition and plant size increasing. Conclusions Our results indicated that the spatial patterns and associations of tree species at seedling and sapling stages partly reflected that at adult stage; habitat heterogeneity and neighborhood competition jointly contributed to species coexistence in this secondary forest.

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