Land-cover change: quantification metrics for perforation using 2-D gap features.

Perforation or gap formation in a vegetation is a major process in landscape transformation. The occurrence of gaps profoundly alters the microclimatical conditions in a vegetation. A method is proposed to quantify perforation by using the three main 2-D characteristics of the gaps: area, number and boundary length. New measures are developed by normalizing the observed values to the reference status of minimum and maximum perforation. As minimum perforation status, the presence of one single gap with area equal to the map resolution is assumed. The new measures are combined using a 3-D Euclidean distance to visualize the process and to detect changes. The method is exemplified using a field case of gaps in a tropical terra firme rainforest at Tiputini, Ecuador.

Photosynthesis and diffusion resistances to carbon dioxide in Hevea brasiliensis muel. agr. clones.

The internal resistance r i, to carbon dioxide diffusion was separated into the mesophyll and the carboxylation components, and it was shown that the mesophyll and the carboxylation resistances r m and r x had similar order of magnitude, suggesting the importance of both in the photosynthesis of Hevea brasiliensis.