Surface energy exchange: Urban and rural forest comparison in a tropical montane cloud forest

Abstract

Topical urban expansion has undergone a great increase, affecting land cover and altering ecosystems. It is important to know physical processes alterations such as surface energy balance in ecosystems surrounded by expanding cities in order to make predictions, planning and management of urban forests. This study determines the surface energy balance of a fragment of tropical montane cloud forest surrounded by a city (urban forest) in the central region of eastern Mexico, and compares it to values obtained in a large matrix of continuous forest adjacent to the city (rural forest) with similar topography. Surface energy exchange was measured by the eddy covariance technique. The urban forest presented values of daytime latent heat flux 4% higher compared to the rural forest (equivalent to 24.7 W/m2), and values of surface heat flux 4% lower (equivalent to 6.4 W/m2). Daily values ​​of energy closure ratio​ (ECR, 0.98) and energy balance ratio (EBR, 0.96) indicated that a greater amount of energy is partitioned from the system by sensible and latent heat fluxes of a urban forests of 30 ha. Also, the urban forest presented a higher diurnal air temperature (mean differences of 0.5 °C and maximum of 1.5 °C) and evapotranspiration rate (mean differences of 0.06 mm/h and maximum of 0.12 mm/h). We believe our work is the first one to compare forests in such contrasting situations, increasing our understanding on the behavior of surface energy exchange of an urban tropical cloud forest, and the intensity of the effect of urbanization on this type of ecosystem.