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Effects of density dependence in a temperate forest in northeastern China

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ABSTRACT

Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.

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Analysis of conspecific density-dependent self-thinning as a function of scale in three areas.Note: (a–f) Proportion of species showing the test statistic g21(r)–g22(r) < 0 (solid circles), g21(r)–g22(r) > 0 (solid squares) and g21(r)–g22(r) = 0 (solid triangles) over scales at the HF, MF and OGF areas, (a–c) saplings as cases and (d–f) juveniles as cases. (g–i) Proportion of examined species showing density dependence at detailed scales at the HF, MF and OGF areas.
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f4: Analysis of conspecific density-dependent self-thinning as a function of scale in three areas.Note: (a–f) Proportion of species showing the test statistic g21(r)–g22(r) < 0 (solid circles), g21(r)–g22(r) > 0 (solid squares) and g21(r)–g22(r) = 0 (solid triangles) over scales at the HF, MF and OGF areas, (a–c) saplings as cases and (d–f) juveniles as cases. (g–i) Proportion of examined species showing density dependence at detailed scales at the HF, MF and OGF areas.

Mentions: In the HF observational study, for saplings, 12 of the 16 species tested exhibited additional aggregation patterns when compared with adults, three species showed random patterns and no species showed any regular patterns. For juveniles, 13 of the 16 species exhibited additional clustering relative to adults, three species showed random patterns and again not a single species showed a regular pattern. In MF, for saplings, 18 of the 21species tested exhibited additional aggregation patterns relative to adults, three species showed random patterns and no species showed any regular pattern. For juveniles, 17 of the 21 tested species exhibited additional clustering relative to adults, three species showed random patterns and two species showed regular patterns. In OGF, for saplings, all 21 species exhibited additional aggregation patterns relative to adults; no species showed a random pattern, nor did any species show a regular pattern. For juveniles, however, only 16 out of 21 species tested exhibited additional clustering relative to adults, four species showed random patterns and one species showed a regular pattern (see Supplementary Table S2). Overall, the percentage of species showing additional clustering relative to adults, decreased from saplings to juveniles over all examined scales in the MF and OGF area, but this tendency did not apply to the HF area (Fig. 4a–f, see Supplementary Table S2).


Effects of density dependence in a temperate forest in northeastern China
Analysis of conspecific density-dependent self-thinning as a function of scale in three areas.Note: (a–f) Proportion of species showing the test statistic g21(r)–g22(r) < 0 (solid circles), g21(r)–g22(r) > 0 (solid squares) and g21(r)–g22(r) = 0 (solid triangles) over scales at the HF, MF and OGF areas, (a–c) saplings as cases and (d–f) juveniles as cases. (g–i) Proportion of examined species showing density dependence at detailed scales at the HF, MF and OGF areas.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015110&req=5

f4: Analysis of conspecific density-dependent self-thinning as a function of scale in three areas.Note: (a–f) Proportion of species showing the test statistic g21(r)–g22(r) < 0 (solid circles), g21(r)–g22(r) > 0 (solid squares) and g21(r)–g22(r) = 0 (solid triangles) over scales at the HF, MF and OGF areas, (a–c) saplings as cases and (d–f) juveniles as cases. (g–i) Proportion of examined species showing density dependence at detailed scales at the HF, MF and OGF areas.
Mentions: In the HF observational study, for saplings, 12 of the 16 species tested exhibited additional aggregation patterns when compared with adults, three species showed random patterns and no species showed any regular patterns. For juveniles, 13 of the 16 species exhibited additional clustering relative to adults, three species showed random patterns and again not a single species showed a regular pattern. In MF, for saplings, 18 of the 21species tested exhibited additional aggregation patterns relative to adults, three species showed random patterns and no species showed any regular pattern. For juveniles, 17 of the 21 tested species exhibited additional clustering relative to adults, three species showed random patterns and two species showed regular patterns. In OGF, for saplings, all 21 species exhibited additional aggregation patterns relative to adults; no species showed a random pattern, nor did any species show a regular pattern. For juveniles, however, only 16 out of 21 species tested exhibited additional clustering relative to adults, four species showed random patterns and one species showed a regular pattern (see Supplementary Table S2). Overall, the percentage of species showing additional clustering relative to adults, decreased from saplings to juveniles over all examined scales in the MF and OGF area, but this tendency did not apply to the HF area (Fig. 4a–f, see Supplementary Table S2).

View Article: PubMed Central - PubMed

ABSTRACT

Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.

No MeSH data available.


Related in: MedlinePlus