position, followed by aspect. So, we used these four effective
variables to build and evaluate each model in three SDs (Table
2). Overall, in three SDs, the best method for model building
was DOMAIN (kappa = 0.83-0.87), followed by DT
(0.72—0.80), MAXENT (0.63—0.68), ML (0.51—0.54) and DA
(0.23—0.47) in order. SDs didn’t affect the model performance.
It is clear to realize that DOMAIN, DT and MAXENT is
efficient in converging the predicted distribution patter.
Convergence of prediction helps ecologist to reduce the
consuming of field survey.
We used the independent samples aforementioned to evaluate
the extrapolating ability, and the result is shown in Table 1. The
result reveals that when evaluating model performance by
independent samples, the kappa value of each model decreased
sharply in both SD1 and SD2. In contrast, the kappa value of
each model in SD3 declined slightly. The result in Table 3
indicated that the model prediction of SD1 and SD2 could not
extend through watershed.
5. CONCLUSIONS
The methods we adopted papered in different ratability, but the
performance efficiency of these methods should be at the same
grade. DOMAIN had the highest prediction accuracy, and the
agreement of model performance between training dataset and
test dataset in DOMAIN was also the best. Although the
performance of DT and MAXENT were slightly lower than
DOMAIN, but this three method had the same level of kappa
coefficient in this study. Hence, we suggest that DOMAIN,
DT and MAXENT a high potential in similar research and
ecological application.
The evaluation of SDs showed that it is hard to extend the
distribution pattern through spatial (e.g. watersheds and
mountain). The phenomenon is strongly established by the
result of two-way extrapolation we designed. The result
indicated that it is hard to extend the spatial patterns of JETs
from one watershed to another and vice versa. By comparing
the microclimate and micro-terrain of the two watersheds, the
humidity and sunlight affected by micro-terrain of these two
watersheds are remarkably different. ^ Consequently, the
models merely based on topographic variables performed
poorly on two-way spatial extrapolation between these two
watersheds. Not surprisingly, the kappa values of predictive
models developed from the merged samples of the two
watersheds in SD3 just declined slightly. ^ The results
suggested that the vegetation indices derived from SPOT-5
images could not improve model accuracy for a widely
distributed tree species due to the limitations of spectral
resolution and spatial resolution with SPOT-S imagery.
Follow-up studies will attempt to extract spectral information
associated with species from hyperspectral data and LIDAR
DEM and use it as variable for model development so that
models are applicable on a broader spatial scale.
Figure 2. Predicted distribution maps of SD3 included (a) DA, (b) DT, (c) MAXENT, (d) ML, and (e) DOMAIN.
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CN 6 mn 95 (AA