Abstract
Dolines are karst formations originated by processes of dissolution. Their environmental conditions, such as air temperature and relative humidity, are different from the exterior and influence the traits of plants that grow within them. The structure of the dolines modifies the environment in a vertical gradient from the bottom to the upper slopes, influencing plant traits and limiting their outside distribution. In this study, we identified an environmental gradient (solar radiation, photosynthetic photon flux density [PPFD], soil and air relative humidity, and temperature) in two dolines, and assessed its influence on the specific leaf area, shape index and leaves' chlorophyll content of two populations, Myriocarpa longipes and Brosimum alicastrum, located at the bottom and on the slopes. There is a gradation in the environmental variables along the dolines, with lower temperature and solar radiation at the bottom and higher air and soil relative humidity. The leaves of both species showed differences between species and within dolines: The concentration of chlorophyll had higher values at the bottom of both dolines for B. alicastrum, while for M. longipes, the highest values were recorded on the slope. The specific leaf area was larger in both species at the bottom than on the slope. The PPFD gradient is the main environmental variable associated to specific leaf area and chlorophyll content in both shade-tolerant and efficient scarce light collector species as corresponds to pioneer species and limiting their presence outside due to higher solar radiation.
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