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a b s t r a c tTimber plantation expansion is a significant form of landscape change with reported negative environmental and social impacts. We analyze the proximate drivers of plantation expansion in southcentral Chile, one of the countries in South America with the highest rates of afforestation and reforestation in the last decades. Satellite images from 1975, 1990 and 2007 were used to estimate autologistic regressions for the periods 1975-1990 and 1990-2007. Timber plantations (mostly Pinus radiata) increased from 29,213 ha in 1975 (5.5% of the landscape) to 224,716 ha in 2007 (42.4% of the landscape). We found a clearer pattern of expansion between 1975 and 1990 as compared to 1990-2007, associated with soils of forest suitability, steep slopes, and proximity to main cities, corporate landholding, and large farms. Between 1990 and 2007 some of these drivers lost significance as plantations expanded in all directions and became the predominant land cover. Additionally, 41.5% of new plantations in the 1975-1990 period and 22.8% in the 1990-2007 period were established by clearing secondary native forests, which corroborates that plantation expansion in Chile has been a direct cause of deforestation and biodiversity loss. Understanding the proximate drivers of plantation expansion is essential in order to advance our comprehension of the underlying patterns and causes of this landscape change, which will allow us to better predict which areas are more vulnerable to change, and help to prevent adverse environmental and social impacts as plantations expand to the southern regions of the country.

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Patterns of interannual variability of the annual water balance are explored using data from 190 MOPEX catchments across the continental U.S. This analysis has led to the derivation of a quantitative, dimensionless, Budyko-type framework to characterize the observed interannual variability of annual water balances. The resulting model is expressed in terms of a humidity index that measures the competition between water and energy availability at the annual time scale, and a similarity parameter (a) that captures the net effects of other short-term climate features and local landscape characteristics. This application of the model to the 190 study catchments revealed the existence of space-time symmetry between spatial (between-catchment) variability and general trends in the temporal (between-year) variability of the annual water balances. The MOPEX study catchments were classified into eight similar catchment groups on the basis of magnitudes of the similarity parameter a. Interesting regional trends of a across the continental U.S. were brought out through identification of similarities between the spatial positions of the catchment groups with the mapping of distinctive ecoregions that implicitly take into account common climatic and vegetation characteristics. In this context, this study has introduced a deep sense of similarity that is evident in observed space-time variability of water balances that also reflect the codependence and coevolution of climate and landscape properties.

The spatiotemporal variability of precipitation in regions of complex mountainous terrains constitutes one of the most challenging research topics of geosciences. This paper explores hourly precipitation data from a set of 25 stations spanning the period 1998 to 2005 within northwestern Colombia, in the Aburrá Valley and the neighboring San Nicolás plateau (75.16 • W−6 • N and 75.66 • W−6.6 • N) which accounts for a land area of ∼4,000 km 2. Our aim is to identify the main features of the diurnal cycle of precipitation over this complex terrain. We found that the average diurnal cycle of rainfall in the study region is bimodal at regional scale although it results from the superposition of two unimodal diurnal cycles shifting its phase throughout the seasons of the year. From October to April, average diurnal rainfall peaks in the afternoon hours (13:00-16:00 LST) but from May to September, the phase of the diurnal cycle changes to midnight hours (22:00-02:00 LST). Three low-level jets (LLJs), namely Caribbean, CHOCO, and the so-called Corriente de los Andes Orientales (CAO), are relevant to explain the seasonal shift of the diurnal cycle given their modulation of the seasonal variation of moisture sources and transport over this region. During June-July-August, moisture from afternoon evaporation processes at the bottom of the inter-Andean Magdalena Valley, located at the east of the study region, is transported by anabatic and easterly trade winds and contribute to explain the midnight and early morning peak. The life cycle of convective processes influences the orographic nature of rainfall distribution and timing in the region since deep convective cores are related with the afternoon peak, whereas wide convective cores with the early morning peak.

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