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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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Conspecific density-dependent analysis of Pinus koraiensis in the MF area.Note:(a) ds(r) = g21(r)–g22(r) over scale r with saplings as cases, (b) dj(r) = g21(r)–g22(r) over scale r with juveniles as cases and (c) d(r) = dj(r)–ds(r) refers to the decline of additional aggregation from the sapling to the juvenile stage. If ds(r) < 0 and d(r) > 0, the conspecific density-dependent thinning takes place from sapling to the juvenile stage at scale r. The maximum strength of conspecific thinning (dmax) occurred at the 0 m scale (i.e., in a 1 × 1 m grid cell).
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f1: Conspecific density-dependent analysis of Pinus koraiensis in the MF area.Note:(a) ds(r) = g21(r)–g22(r) over scale r with saplings as cases, (b) dj(r) = g21(r)–g22(r) over scale r with juveniles as cases and (c) d(r) = dj(r)–ds(r) refers to the decline of additional aggregation from the sapling to the juvenile stage. If ds(r) < 0 and d(r) > 0, the conspecific density-dependent thinning takes place from sapling to the juvenile stage at scale r. The maximum strength of conspecific thinning (dmax) occurred at the 0 m scale (i.e., in a 1 × 1 m grid cell).

Mentions: We present the density dependence of Pinus koraiensis, a dominant coniferous tree species in the MF area, to illustrate the method used in this analysis (Fig. 1).


Effects of density dependence in a temperate forest in northeastern China
Conspecific density-dependent analysis of Pinus koraiensis in the MF area.Note:(a) ds(r) = g21(r)–g22(r) over scale r with saplings as cases, (b) dj(r) = g21(r)–g22(r) over scale r with juveniles as cases and (c) d(r) = dj(r)–ds(r) refers to the decline of additional aggregation from the sapling to the juvenile stage. If ds(r) < 0 and d(r) > 0, the conspecific density-dependent thinning takes place from sapling to the juvenile stage at scale r. The maximum strength of conspecific thinning (dmax) occurred at the 0 m scale (i.e., in a 1 × 1 m grid cell).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Conspecific density-dependent analysis of Pinus koraiensis in the MF area.Note:(a) ds(r) = g21(r)–g22(r) over scale r with saplings as cases, (b) dj(r) = g21(r)–g22(r) over scale r with juveniles as cases and (c) d(r) = dj(r)–ds(r) refers to the decline of additional aggregation from the sapling to the juvenile stage. If ds(r) < 0 and d(r) > 0, the conspecific density-dependent thinning takes place from sapling to the juvenile stage at scale r. The maximum strength of conspecific thinning (dmax) occurred at the 0 m scale (i.e., in a 1 × 1 m grid cell).
Mentions: We present the density dependence of Pinus koraiensis, a dominant coniferous tree species in the MF area, to illustrate the method used in this analysis (Fig. 1).

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