Jesús Santiago Notario del Pino

Effects of a Canary pine forest wildfire (Tenerife, Canary Islands, summer 2007) on selected soil properties and their relationship with short- to medium-term soil water repellency .

Forest fires modify the soil environment, often triggering severe soil degradation. In this paper, we studied the impact of a large northern Tenerife Canariy pine forest wildfire on a set of relevant soil properties, focusing on their evolution in time and relationship with soil water repellency. To do this, soils were sampled at four sites (burned and non-burned) and several soil physical and chemical parameters were measured. The results show significant variations for soil pH, electric conductivity (CE 1:5 ), and NH 4 + -N between burned and non-burned samples, whereas non-significant increases were found in burned soils for oxidizable carbon (C ox ), total nitrogen (N tot ) , Ca 2+ , Mg 2+ , Na + and K + , and soil hydrophobicity. The differences caused by the fire were no longer evident one year later. Furthermore, in one sampling site (Vitric Leptosols under low pine forest with a mixed heath/beech tree understory) a wide variation in the content of C ox and N tot and high water repellency was observed relative to the other sites. These differences can be attributed to the composition of the understory vegetation. Significant correlations between soil hydrophobicity with CE 1:5 , aggregate stability and the contents of C ox , N tot , NH 4 + -N, Ca 2+ , Mg 2+ , Na + and K + were found.

Pesticide distribution and movement

Dpto. de Edafologia y Geologia, Universidad de La Laguna, 30204, La Laguna, EspanaIntroductionThe first alarm signals with regardto the applicationofpesticides in agrosystems appeared in the late 50s andbecame more and more evident in the 60s. However,the control of pests and diseases is essential; globallosses in world agricultural production have been esti-mated as up to one third of the total. Therefore, theuse of pesticides in modern agriculture, despite thenegative effects on the environment, is necessary.The study of pesticides in ground waters is rel-atively new. The emphasis on the subject in theUnites States began in 1979 with multiple detectionsof aldicarb [27] and DBCP [14] in the ground water ofseveral states. By the mid 80s, at least 17 pesticideshad been found in the ground water of 23 states asa result of field use. The issue has been addressed inother countries, particularly in Canada, and in westernEurope [18].When contemplating the vulnerability of groundwater to pesticides, three factors should be taken intoaccount: (i) the properties of the pesticide itself affect-ing its mobility, (ii) the dynamics of the pesticide inthe soil system and (iii) the movement of the pesticidethrough the rocks that underly the soil. These aspectsare detailed below.Properties of pesticides affecting their mobilityThe term Pesticide is currently used to describe a widegroup of substances used to control or to eliminateplant pests and diseases. The physicochemical fea-tures of such a variety of compounds is great, but theparameters useful to describe their movement and dy-namics through soils and aquifers are relatively few.Among them, are the following:Water solubilityThis parameter is important because water is the ve-hicle in which pesticides move on their way to theground water. If a pesticide is supposed to be poten-tially hazardous, it is expected to be at least partiallysoluble in water. However, this general rule has beenshown not always to be true, because some pesti-cides whose water solubility is low can reach thegroundwater in association with solid particles [26].The n-octanol:water partition coefficient (K