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Kriging and splines with derivative information 总被引:2,自引:0,他引:2
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Ole R. Vetaas 《植被学杂志》1997,8(5):665-676
Abstract. Correlations between five floristic gradients at small spatial extents (10 - 20 m) and one successional gradient over a larger spatial extent (1.5 km) are analysed. Floristic data (62 taxa) were sampled on five terminal moraines of known age deposited after the ‘Little Ice Age’ (1750–1930). The floristic gradients on the moraine ridges were sampled by two or three transects on each moraine, and the successional gradient by 114 plots on all moraines. The sequential orders of species were determined by constrained and unconstrained Correspondence Analysis. The similarities between species order on the successional gradient and the exposure gradients at the same age were tested against the null hypothesis of no correlation. The null hypothesis was rejected using both Monte Carlo permutation tests and Spearman's rank correlations, except on the oldest moraine. Here a closed canopy has developed, which eliminates the environmental variability associated with ridge morphology. The similarity between the successional gradient and the moraine-ridge gradients is attributed to variation in environmental severity, mainly caused by glacier wind and related factors such as temperature and moisture. Similarity was highest on the moraines in the middle of the glacier foreland, which have many successional stages present and have a relatively exposed relief. The distribution of growth/life-forms along gradients of small spatial extent are comparable to the successional gradient, but lichens, herbs and graminoids differ in their behaviour. The resemblance between species gradients at a small spatial extent and species gradients on a larger spatial extent is interpreted as an ecological self-similar pattern, where young and old substrate are linked to exposed-xeric and protected-mesic habitats, respectively. 相似文献
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Species turnover at small scales in dune slack plant communities 总被引:1,自引:0,他引:1
Patterns of both species accumulation with increasing area and of individual species occurrences depend on the scale level considered. This study investigated community diversity and individual species turnover patterns between four scale levels within 2×2 m2 nested plots situated in a dune slack plant community. The number of species increased with plot area following a log–log function, with a slope of 0.23. However, species turnover was higher between the lowest scale levels, indicating limitations on species occurrences at the 25×25 cm2 scale level. Alpha diversity in rectangular plots was significantly higher than in square plots of the same area. There were strong differences between individual species turnover patterns. Most species occurrence patterns had a box-counting fractal dimension value between 0.8 and 1.6, which is rather low compared with other studies on larger scale levels. Analyses of occurrence probabilities and scale area plots showed that there is a systematic deviation from self-similarity at the smallest scale level. Species had a lower frequency than expected from a fractal distribution, suggesting a higher level of species aggregation. The higher species diversity turnover at the smallest scale level can be linked to a higher spatial aggregation of individual species, due to biotic or abiotic limitations on their occurrence. These results confirm the general nature of the pattern of break-down of self-similarity at the smallest scale level considered.
Zusammenfassung
Sowohl das Muster des Artenanstiegs mit zunehmender Fläche als auch das Muster des Auftretens einzelner Arten hängen vom betrachteten Skalenlevel ab. Diese Studie untersuchte die Diversität der Lebensgemeinschaft und die Muster der Fluktuationen einzelner Arten auf vier Skalenlevels innerhalb von 2×2 m2 ineinander geschachtelten Versuchsflächen in einer Pflanzengemeinschaft der Dünentäler. Die Zahl der Arten nahm mit der Versuchsfläche entsprechend einer log–log Funktion mit einer Steigung von 0.23 zu. Die Artenfluktuation zwischen den niedrigsten Skalenlevels war jedoch größer und weist darauf hin, dass es Limitierungen für das Auftreten der Arten auf dem 25×25 cm2 Skalenlevel gibt. Die Alpha-Diversität war in rechteckigen Versuchsflächen signifikant größer als in quadratischen Versuchsflächen der gleichen Größe. Es gab größe Unterschiede in den Mustern der Fluktuation einzelner Arten. Die meisten Muster des Auftretens der Arten hatten fraktale Box-Counting-Dimensions-Werte zwischen 0.8 und 1.6, was relativ gering im Vergleich zu Studien auf größeren Skalenlevels ist. Die Analysen der Auftretenswahrscheinlichkeit und der Probefläche der Skalenlevels zeigten, dass es eine systematische Abweichung von der Selbstähnlichkeit auf dem kleinsten Skalenlevel gibt. Die Arten hatten eine geringere Häufigkeit als die aufgrund einer fraktalen Verteilung erwartete, was einen höheren Level der Artaggregation vermuten lässt. Die größere Fluktuation der Artendiversität auf dem kleinsten Skalenlevel kann mit einer größeren räumlichen Aggregation einzelner Arten aufgrund von biotischen und abiotischen Beschränkungen ihres Vorkommens in Verbindung gebracht werden. Diese Ergebnisse bestätigen die generelle Natur des Musters des Zusammenbruchs der Selbstähnlichkeit auf den kleinsten betrachteten Skalenlevels. 相似文献6.
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