Vegetation and terrain drivers of infiltration depth along a semiarid hillslope.

An improved understanding of the drivers controlling infiltration patterns in semiarid regions is of key importance, as they have important implications for ecosystem productivity, retention of resources and the restoration of degraded areas. The infiltration depth variability (ΔInf) in vegetation patches at the hillslope scale can be driven by different factors along the hillslope. Here we investigate the effects of vegetation and terrain attributes under hypothesis that these attributes exert a major control in ΔInf within the patches. We characterise the ΔInf within vegetation patches at a semiarid hillslope located at the Jornada Experimental Range at dry antecedent conditions preceding two winter frontal rainfall events. We measured these events that are typical during winter conditions, and are characterised by low intensity (0.67 and 4.48 mm h-1) and a total rainfall of 10.4 and 4.6 mm. High precision geo-referenced wetting front depth measurements were taken at various locations within the vegetation patches using differential GPS. Vegetation and terrain attributes were analysed to explain the ΔInf among the vegetation patches. The infiltration depths in the periphery of the patches were in general considerably deeper than those in the centre. The observations suggest that the upslope margin of the patches received additional water in the form of runon from upslope adjacent bare soil. Patch orientation with regard to the slope dictated the effect of the rest of the patch attributes and the distance to the hillslope crest on ΔInf. We found that primarily patch orientation, followed by shape and size modulate lateral surface water transport through their effects on overland flow paths and water retention; something that would be obscured under more simplistic characterisations based on bare versus uniform vegetated soil discrimination.

Can people feel happy and sad at the same time?

The authors investigated whether people can feel happy and sad at the same time. J. A. Russell and J. M. Carroll's (1999) circumplex model holds that happiness and sadness are polar opposites and, thus, mutually exclusive. In contrast, the evaluative space model (J. T. Cacioppo & G. G. Berntson, 1994) proposes that positive and negative affect are separable and that mixed feelings of happiness and sadness can co-occur. The authors both replicated and extended past research by showing that whereas most participants surveyed in typical situations felt either happy or sad, many participants surveyed immediately after watching the film Life Is Beautiful, moving out of their dormitories, or graduating from college felt both happy and sad. Results suggest that although affective experience may typically be bipolar, the underlying processes, and occasionally the resulting experience of emotion, are better characterized as bivariate.