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Near infrared (NIR) spectroscopy was used to predict the soil organic carbon (SOC) contents at local scale in eleven target sites. For that, eight spectral libraries of different sizes (ranging from 3482 to 36 samples) were used to construct national, provincial and local scale models. Inaccurate predictions were obtained except when the largest national library was used to construct the model. We also obtained SOC predictions once the models were adapted to target sites characteristics. For the models' adaptation, we used a two-step approach consisting on spiking (as first step) and extra-weighting (as second step). The effect of spiking was small in larger-sized models and high in smaller-sized models, whereas the effect of extra-weighting was small in smaller-sized models and large in larger-sized models. The very high accuracy obtained after models' adaptation (R2>0.95; RPIQ>5.48), regardless of the size of the spectral library, suggests that large spectral libraries are not needed for local scale SOC assessment. These results have important implications regarding the way that NIR spectroscopy can result highly effective for land management and how users can focus and organize the analytical efforts.

En la presente investigación: (i) se caracteriza el régimen de precipitaciones y la evolución pluviométrica durante el último medio siglo en las Cordilleras Béticas Litorales, sus tendencias y ciclos, (ii) se utiliza el método de reproducción de situaciones análogas en un gradiente pluviométrico, como una buena alternativa para el estudio comparado de procesos de degradación del suelo-desertificación en zonas próximas, con semejanzas en morfología, pero contraste climático; y (iii), se reflexiona acerca de posibles escenarios futuros, en el marco de la dinámica pluviométrica analizada., In the present research have been: (i) characterized the regime of rainfall and rainfall evolution during the last half-century in the Bethic coastlines mountains, trends or cycles included, (ii) used the method of reproduction of similar situations in a rainfall gradient, as a good alternative to the comparative study of soil degradation and desertification processes in areas, with similarities in morphology, but contrast in climate; and (iii) established different future scenarios, in the framework of the analyzed pluviometric dynamics.