spaa (version 0.2.5)

sp.assoc: Analyzing species association

Description

Analyzing species association

Usage

sp.assoc(matr)

Value

Variance ratio, W, Chisq, etc, see details

pi

Species frequency

N

Number of plots

S

Number of species

Tj

Total number of species for each plot

Numspmean

Mean number of species

sigmaTsq

Variance of species relative frequency

STsq

Variance of species number

var.ratio

Variance ratio

W

W statiscit value: used in comparison with chi square.(n)

Arguments

matr

standard community matrix , with rows representing sites and columns representing species.

Author

Jinlong Zhang

Details

Computations are based on the following formula.

If, N: Number of plots.

S: Number of species.

n: Number of plots occupied by certain species.

Tj: total number of species for each plot. s t: mean species number for all the plots.

Then: Variance of species relative frequency is: sigma^{2}{T}= sum{i}=1^{s}P{i}(1-P{i}).

Variance of species number is: S^{2}{T}=({1}{N})sum{j=1}^{N}(T{j}-t)^{2} .

Species relative frequency: P{i}={n{i}}{N}.

Variance ratio:

If VR > 1 Positively associated,

If VR < 1 Negative associated

VR = {S{T}^{2}}/{sigma{T}^{2}}

W: used in comparison with chi square with n degrees of freedom.

W = VR * N

References

Zhang Qiaoying, Peng Shaolin, Zhang Sumei, Zhang Yunchun, Hou Yuping. (2008) Association of dormintant species in Guia hill Municipal Park of Macao. Ecology and Environment. 17:1541-1547

GUO zhongling, MA yuandan, ZHENG Jiping, LIU Wande , JIN Zefeng.(2004) Biodiversity of tree species,their populations'spatial distribution pattern and interspecific association in mixed deciduous broadleaved forest in Changbai Mountains. Chinese Journal of Applied Ecology. 15:2013-2018

Shi Zuomin, Liu Shirong, Cheng Ruimei, Jiang Youxu.(2001) Interspecific association of plant populations in deciduous broad leaved forest in Baotianman. Scientia Silvae Sinicae. 37:30-35

See Also

See also sp.pair for association between each pair of species.

Examples

data(testdata)
spmatrix <- data2mat(testdata)
sp.assoc(spmatrix)