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Alejandro?D.?Canepuccia Maria?S.?Fanjul Eugenia?Fanjul Florencia?Botto Oscar?O.?Iribarne Consejo Nacional de Investigaciones Científicas y Técnicas Departamento de Biología Universidad Nacional de Mar del Plata Mar del Plata Argentina 《Estuaries and Coasts》2008,31(5):920-930
The role of positive and indirect interactions is often crucial in communities with intense abiotic stress such as salt marshes.
The burrowing crab, Neohelice (=Chasmagnathus) granulata, is the dominant benthic macroinvertebrate of southwest Atlantic marshes (southern Brazil to Northern Argentinean Patagonia),
having strong direct and indirect effects on marsh soil and, in consequence, on marsh vegetation and primary consumers. In
this work, we investigate if this crab indirectly modifies habitat use by the granivorous rodents, Akodon azarae and Oligoryzomys flavescens, by increasing nutrient availability and thus enhancing seed production by the marsh plant Spartina densiflora. The study was conducted at the Mar Chiquita Coastal Lagoon, Argentina (37°32′ S). Rodent frequencies in S. densiflora were positively correlated with crab densities throughout the low and middle marsh. Additionally, the highest quality of
S. densiflora and inflorescence density was recorded at the highest crab densities. Experimental manipulation of crab densities shows that
N. granulata indirectly enhances the performance of S. densiflora (e.g., decreased fiber content and C/N ratios) and increases density of seeds. Moreover, N. granulata also facilitates S. densiflora seed availability to rodents by concentrating them in sediment mound at their burrows entrances. Experimental rodent exclusions
showed that rodent species used S. densiflora seeds, a variable positively related to crab burrow density. Thus, our results show that N. granulata drives the granivorous rodent distribution and the intensity of seeds–rodent interaction trough facilitative and indirect
interactions in marsh community. 相似文献
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JuanGarcíaEscudero 《中国天文和天体物理学报》2004,4(4):343-348
Non periodic ordered sequences obtained by production rules in formal grammars are applied to the analysis of the multi-periodicity of the δ-Scuti type variable star V784 Cas. An artificial light curve for V784 Cas is generated by a non deterministic derivation in a context-sensitive grammar by concatenation of two sinusoidal fragments following certain word sequences. The two basic building blocks represent temporal segments in a golden ratio and the number of long and short segments in a word are also in a golden ratio. 相似文献
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L. V. PEREZ-ARRIBAS F. NAVARRO-VILLOSLADA M. E. LEON-GONZALEA L. M. POLO-DIEZ Departamento de Quimica Analiti Facultad de Ciencias Quimicas Universidad Complutense E- Madri Spain 《地理学报(英文版)》1993,(4)
The usefulness of the Kalman filter as an algorithm for calibration in a real system is shown. Results arecompared with classical least squares and pure component calibration. The prediction of four prioritypollutant chlorophenols in binary, ternary and quaternary mixtures was also carried out by Kalmanfiltering. The condition number, standard deviation and prediction error have been employed to choosethe most suitable wavelength range. Comparison of the standard error of prediction in the validation setshows significant differences between the evaluated chlorophenols, the best results being obtained withKalman multivariate calibration. 相似文献
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