Dear All,
I am working modeling the distribution of tree parameters (Basal area per ha and Number of trees per ha) for an adult strata of a tropical forest. The modeling is being done for (1) all species present in the area, and (2) the seven economically most important species in the area. The final intention is to use the range to improve the sampling technique (if possible less plots for and approximately same precision). As the area has been intensively explored, same species are just present in less than 10 plots (from a total of 357). For the plots were they are not present, I used the number zero to represent a measured 0 m�/ha of basal area (in the first case), or 0 trees/ha (in the second case) on the plot. My questions are:
(1) How should I deal with these zeros while modeling the semivariogram? I am asking because I tried using them and the semivariograms look strange (small lags presenting sometimes higher semivariances than large lags). In this case, I also tried to interpolate (using kriging) for values between my plots. Cross validation (Jack knife) shows also an unsatisfatory result (line below the x axis). On my second try, I took the zeros out. The semivariogram looks much better. But the kriging is unsatisfatory estimating very high values for plots were there aren't trees of the studied species at all! Another problem is the number of observations that I used in this case: sometimes just 8. Can anyone give me a help?
(2) Can anyone recommend literature that deals with the use of geostatistics to help the planning of number and location of sampling units in forests?
Thank you very much!!
Valquiria
Forst-Ing. Valquiria Ferraz Quirino
Kappler Stra�e 57, Zi. 2121, 79117 Freiburg i. Br. Deutschland
Tel.: +49 761 6806-6204
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