SOLOS FLORESTAIS EM FRAGMENTO DE FLORESTA URBANA NA MATA DE DOIS IRMÃOS, RECIFE, PERNAMBUCO, BRASIL

The forest remnant that composes ‘Parque Estadual Dois Irmãos’ (PEDI) is regarded as one of the largest urban forest fragments in Brazil. There are reports of frequent occurrence of healthy fall trees in the park, in natural conditions, which may compromise its natural balance and its function as an urban forest fragment. Probably, this phenomenon is associated to the chemical and physical properties of the soils comprising PEDI. So, this research aimed to evaluate PEDI soils chemical and physically, identifying, mapping and analyzing the soils in the occurrence of falling tree areas at the research locus. Twelve points of sampling in a representative area of PEDI were mapped, where deformed samples were collected at depths 0-0.10; 0.10-0.30 and 0.30-0.60 m, and not deformed samples at depths 0-0.05 and 0.10-0.15 m. The chemical attributes and part of the physical attributes were determined in the deformed samples. And other physical attributes were determined in the undisturbed samples. The soils of PEDI were low in natural fertility. They have acid reaction and high concentrations of Al3+ to 0.60 m, and this can create chemical barriers that damage the growth of the plant roots and may be the cause of the frequent tree falling in the park. The soils were classified as clayed to very clayed, very permeable to vertical and lateral water movement. They had high variability in hydraulic conductivity and sharp decrease of water volumetric content in applying small stresses in surface layers as well as higher water retention by soil in Oxisol subsurface. In order to extend the information and create a database for future studies, it is suggested the monitoring of the most vulnerable species to fall, and analyzing other chemical and physical properties of PEDI soils, also opening profiles to understand tap root dynamics