Herbivory on Young and Mature Leaves of One Temperate Deciduous and Two Tropical Evergreen Trees in the Understory and Canopy of a Mexican Cloud Forest

Abstract

Hypotheses about differences in herbivory between species, young and mature leaves, and understory and canopy leaves were tested in 1994 and 1995. The authors measured herbivory in the following three tree species representing different phytogeographical affinities in a tropical montane cloud forest in Mexico: Carpinus caroliniana (temperate deciduous), Oreopanax xalapensis (neotropical broadleaved-evergreen) and Turpinia insignis (American-Asiatic broadleaved-evergreen). Foliar buds were tagged in 20 trees per species, and randomly selected leaves were collected when young (1-2 months) or mature (6-8 months), in both the understory and canopy. A total of 5804 leaves were measured for leaf area losses (% holes plus damaged areas). Total herbivory was expressed as % area loss in mature leaves, while herbivory rate was expressed as % area loss/month. Specific leaf area and toughness were determined in subsamples. Differences in total herbivory and herbivory rates were observed among species. Total herbivore damage in mature leaves was as follows: Carpinus 2.7% ± 0.2, Oreopanax 9.7% ± 4.3, and Turpinia 8.0% ± 0.6. Overall, herbivory rates were higher in young (3.6 ± 0.5 %/month) than in mature leaves (1.9 ± 0.3 %/month), and herbivory rates were higher in understory (3.3 ± 0.5 %/month) than in canopy leaves (2.2 ± 0.3 %/month). Within a species, however, only Oreopanax showed higher rates as significant trends. Herbivore damage apparently was not related to specific leaf area and toughness; however, it may be related to foliar phenological characteristics. En un bosque de neblina en Veracruz, México, se probaron hipótesis sobre herbivoría diferencial entre especies, hojas jóvenes y maduras, y hojas del sotobosque y del dosel. En 1994 y 1995, las especies estudiadas fueron Carpinus caroliniana (templada caducifolia), Oreopanax xalapensis (neotropical perennifolia) y Turpinia insignis (Americana-Asiática perennifolia). Se marcaron yemas foliares en 20 árboles por especie; se colectaron al azar hojas jóvenes (1-2 meses) o maduras (6-8 meses) en el sotobosque y en el dosel. En 5804 hojas se midió el porcentaje de área foliar perdida (% hoyos y área dañada). La herbivoría total se expresó como % de área perdida en hojas maduras, y la tasa de herbivoría se expresó como % área perdida/mes. El area foliar específica y la dureza se determinaron en submuestras. El porcentaje de herbivoría total en hojas maduras fue: Carpinus 2.7% ± 0.2, Oreopanax 9.7% ± 4.3, y Turpinia 8.0% ± 0.6. En general, la tasa de herbivoría fue mayor en hojas jóvenes (3.6 ± 0.5 %/mes) que en hojas maduras (1.9 ± 0.3 %/mes), y también fue mayor en el sotobosque (3.3 ± 0.5 %/mes) que en el dosel (2.2 ± 0.3 %/mes). Pero al considerar especies, solo Oreopanax mostró estas tendencias significativamente. Los niveles de herbivoría, aparentemente no estuvieron relacionados con área foliar específica o dureza, pero parecen estar relacionados con características fenológicas foliares.