Analyzing species association

sp.assoc(matr)

Arguments

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

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

Value

Variance ratio, W, Chisq, etc, see details

Species frequency

Number of plots

Number of species

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 statiscit value: used in comparison with chi square.(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

Author

Jinlong Zhang jinlongzhang01@gmail.com

Examples

data(testdata)
spmatrix <- data2mat(testdata)
sp.assoc(spmatrix)
#> $pi
#>       sp1       sp2       sp3       sp4       sp5       sp6       sp7 
#> 0.6666667 0.6666667 0.6666667 0.6666667 0.3333333 0.3333333 0.3333333 
#> 
#> $N
#> [1] 3
#> 
#> $S
#> [1] 7
#> 
#> $Tj
#> plot1 plot2 plot3 
#>     5     2     4 
#> 
#> $Numspmean
#> [1] 3.666667
#> 
#> $sigmaTsq
#> [1] 1.555556
#> 
#> $STsq
#> [1] 1.555556
#> 
#> $var.ratio
#> [1] 1
#> 
#> $W
#> [1] 3
#>