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2 Polish Journal of Ecology

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Altitudinal patterns of vascular plant richness in high mountains: applying of Generative Additive Model

Tu W., Gao X., Wu N., Liu S.

Polish Journal of Ecology

2010

Vol. 58, nr 2

231-240

To explore and describe the species richness patterns along altitudinal, high mountain gradients, two transects . northern exposure (YG) and southern exposure (TD) at Mt. Jiuding (1200.4200 m) in Western China (31[degrees]13'- 31[degrees]46'N, 103[degrees]29'-104[degrees]05'E) were selected. They differ from south to north in climate conditions and vegetation zonation, and each transect was sampled according to a uniform method. Every 200 m along the altitudinal gradient we set a sampling belt of 3000 m x 5 m to record the tree species, and 30 plots of 5 m x 5 m within every vegetation belt were used to investigate shrub and herb species. We compared the composition of plant species and calculated the coefficient of similarity between the two transects. A Generalized Additive Model (GAM) was used to describe the richness patterns. For the whole Mt. Jiuding, the richness at all three levels (species, genus and family) showed a monotonically decreasing pattern. As for the different growth forms, richness of the trees, shrubs and pteridophytes showed hump-shaped patterns; and herbs showed a slow decreasing pattern along the altitudinal gradients. In TD transect, the richness of species, genus and family also showed monotonically decreasing patterns; tree richness decreased with the increase of altitude; the shrub richness showed a humpshaped pattern; but pteridophytes and other herbs showed wave-like patterns. In YG transect, altitudinal gradient of richness at different taxonomic levels all showed hump-shaped patterns; and the species richness patterns for different growth forms peaked at middle attitude except for the graminoids and other herbs. The evolutionary history of the vegetation in Mt. Jiuding was quite consistent, and different richness patterns along altitudinal gradients might be resulted from different contemporary ecological conditions. Human disturbance and different range of altitudinal gradients were also important factors for different richness patterns between the two transects. In our study, species in different growth forms showed different altitudinal patterns, but those species with similar requirements to environmental conditions showed similar richness patterns along altitudinal gradients.

Effect of spatial scale on relationship between plant species richness and microclimate in a forested ecosystem

Xu M., Qi Y.

Polish Journal of Ecology

2000

Vol. 48, nr 1

77-88

This study examined how the correlation between plant species richness and microclimate varies when aggregation scales change from 10 to 3000 m. We measured soil moisture and air, soil and soil surface temperatures in the Southeastern Missouri Ozarks. Measurement were taken every 10 m along a 4250 m transect during the 1996 growing season. Plants up to 2 m above ground were sampled using 1 x 1 m^2 plots to record average height and coverage by species. We found that the correlation between understory plant species richness and temperature was, in general, highly dependent on spatial scale. The correlation coefficients were small, or even negative, at small scales, and the highest correlation occured around the 1500 m scale. Univariate linear regression analysis at 1500 m scale indicated that growing season mean temperatures of air, soil, and soil surface explained 83%, 76%, and 74% of the total variance in species richness, respectively. Microclimate variables, including seasonal mean, minimum and maximum temperatures of air, soil, and soil surface and seasonal soil moisture, explained 98% of the total variance in plant species richness (R^2=0,98, n=277, P<0,01) at 1500m scale. The results from this study suggest that the species-energy theory was adequately supported at certain spatial scales (around 1500m in this case), but less supported at other scales within the range under study. The findings indicate the necessity, feasibility, and difficulty to incorporate spatial scales explicitly into the species-energy theory.