ORIGIN OF HYDROPHOBIC COMPOUNDS AND THEIR EFFECTS IN Pinus AND Eucalyptus FORESTS

A hidrofobicidade pode ser entendida como a repel\ueancia do solo \ue0 \ue1gua, dificultando o seu molhamento. Esse fen\uf4meno est\ue1 associado ao recobrimento das part\uedculas do solo por subst\ue2ncias org\ue2nicas hidrof\uf3bicas, sendo que atualmente existem in\ufameros relatos de repel\ueancia \ue0 \ue1gua em \ue1reas de florestas de Eucalyptus e Pinus . Assim, este trabalho teve por objetivo revisar e elencar os aspectos relacionados \ue0 origem dos compostos hidrof\uf3bicos e os seus efeitos na din\ue2mica da \ue1gua no ambiente florestal, al\ue9m de implica\ue7\uf5es no crescimento e desenvolvimento das \ue1rvores em florestas de Eucalyptus e Pinus. Reconhece-se que a vegeta\ue7\ue3o local e algumas bact\ue9rias e fungos, em fun\ue7\ue3o da sua composi\ue7\ue3o qu\uedmica, podem liberar subst\ue2ncias org\ue2nicas hidr\uf3fobas. Outro fator condicionante \ue9 a ocorr\ueancia de inc\ueandios e queimadas, que induzem altera\ue7\uf5es nos compostos org\ue2nicos e promovem o secamento do solo. Al\ue9m disso, a composi\ue7\ue3o granulom\ue9trica e o pH do solo podem estar indiretamente associados \ue0 ocorr\ueancia de repel\ueancia \ue0 \ue1gua no solo. A exist\ueancia de hidrofobicidade exige uma aten\ue7\ue3o diferenciada, principalmente em rela\ue7\ue3o ao uso e manejo do solo, pois afeta diretamente o movimento da \ue1gua na superf\uedcie e no interior do perfil de solo. Altera\ue7\uf5es na sortividade, redu\ue7\ue3o da taxa de infiltra\ue7\ue3o, escoamento superficial elevado e ocorr\ueancia de fluxo preferencial s\ue3o os principais efeitos hidrol\uf3gicos desse fen\uf4meno. Em fun\ue7\ue3o das menores taxas de infiltra\ue7\ue3o h\ue1 aumento do escoamento superficial e redu\ue7\ue3o da quantidade de \ue1gua dispon\uedvel, potencializando o processo erosivo e, consequentemente, afetando o crescimento e o desenvolvimento das plantas.Hydrophobicity can be understood as the soil water repellency or difficulty to soil wetting. This is associated with the coating of soil particles by hydrophobic organic substances and currently there are numerous reports of water repellency in forest areas of Eucalyptus and Pinus . Thus, this study aims at reviewing and listing the aspects related to the origin of hydrophobic compounds and the effects of the water dynamics in the forest environment, as well as implications in growth and development of trees in Eucalyptus and Pinus forests. It is recognized that the local vegetation and some bacteria and fungi, depending on their chemical composition, may release hydrophobic organic substances. Another risk factor is the occurrence of burnings which induce changes in organic compounds and promote soil drying. Furthermore, the particle size distribution and the soil pH may be indirectly associated with the occurrence of soil water repellency. The occurrence of hydrophobicity requires special attention regarding the soil use and management, because this repellency affects the water movement on the surface and inside the soil profile. Changes in sorptivity, reduction in water infiltration, increase in runoff and occurrence of preferential flow are the main hydrological effects of this phenomenon. Due to their lower infiltration rates there is increased the surface flow and reducing the amount of water available, increasing the erosion and, consequently affecting the growth and development of plants