In a greenhouse experiment, seedling survival of two oak species (Quercus rugosa and Q. laurina) was greatly affected by the excision of cotyledons 1 mo after germination, with a greater impact on Q. laurina. The effect of seed size was also significant for both species, with a positive correlation between seed mass and survival and growth. The effect of cotyledon excision on seedling growth persisted throughout the first growing season in Q. rugosa and was not analyzed for Q. laurina due to the low number of seedlings that survived cotyledon excision. Seed size significantly affected seedling height, diameter, leaf area, and biomass at 6 mo. Seed size and cotyledon retention affected the ability of Q. rugosa to recover from herbivory, as both factors had a significant effect on relative growth rates after aerial biomass removal. The results show that seedlings originating from large seeds can better endure loss of cotyledons and aerial biomass and thus are better equipped to confront stress early in their lives.

Question: Which is the response of the evergreen Quercus ilex and the deciduous Q. cerrioides to repeated disturbances? Location: central Catalonia (northeastern Spain), in the areas affected by two of the largest historically recorded wildfires in NE Spain: the Bages-Berguedà fire (24 300 ha forested area burned in July 1994), and the Solsonès fire (14 300 ha burned in 1998). Methods: Survival and growth of individuals of Quercus ilex and Q. cerrioides were evaluated in plants subjected to different fire histories and experimental disturbances (burning, cutting or clipping) applied either before or after summer. Results: Survival was high (> 99%), with both species showing a similar high resistance to disturbances. Growth after experimental disturbance was positively related to the size of the individual before the latest forest fire occurred. Fire history had a large effect on resprout growth, as the repeated incidence of disturbances lowered the capacity of individuals to grow. The type and season of experimental disturbance experienced by plants had a large effect. Individuals that experienced total above-ground loss had lower growth rates than those with partial loss. A similar pattern was observed in individuals disturbed after the summer in relation to those disturbed before summer. Conclusions: The larger growth rates recorded in Q. cerrioides across all fire histories and experimental treatments, and the higher vulnerability of Q. ilex to increased fire frequency, intensity of experimental disturbance, and disturbance season, provide evidence for the relatively high susceptibility of the latter to repeated disturbances. This view disagrees with the larger resilience of this species compared to co-existing deciduous oaks, as reported.

In order to define the 'regeneration niche' and then promote the re-introduction of Quercus rugosa into a disturbed area we studied seed predation, germination, seedling survival and growth of this species at three different sites: the forest interior, the forest border and a disturbed site, along a disturbance gradient. Acorn removal on the ground was high at the sites, with higher removal rates from 25-seed clusters than from 5-and 1-seed clusters. More seeds were removed at the forest border than at the other two sites, although in all cases some seeds remained in the soil for periods long enough for them to germinate and produce seedlings. Seed germination and seedling establishment were more successful and similar in the forest interior and the forest border, and much less successful at the disturbed site, due to acorn desiccation. Seedling survival was strongly affected by site, with the highest survival at the forest border and the lowest survival at the disturbed site after a year.The subsequent dry season, which was particularly harsh, caused a drop in survival both at the forest border and the disturbed site. In the former, a closer analysis revealed that partially shaded microsites enhanced survival, while in the latter overall survival was very low, with approximately 5 % of the seedlings surviving, compared to 50 % final survival at the other sites. There was a positive correlation between seed size and seedling survival at the forest border. The three size variables measured (seedling height, basal diameter and crown area) did not increase noticeably during the 20-month study period at the forest interior, while growth still occurred at the forest border and the disturbed site. However, during the two dry seasons there were large drops in mean seedling height and crown area at the disturbed site, due to more frequent dieback, causing large variation in seedling size.These results show that extensive re-introduction of this species to the disturbed area will probably fail under present conditions, and that careful selection or duplication of microsites that mimic the partial shade of the forest border is a sound method for improving oak establishment at this site.

as ri b e ras de los ríos son sistemas ab i e rtos con propiedades físicas y biológicas propias, a lo largo de los cuales se redistribuye el material orgánico transportado por la corriente del río. Debido a la proximidad y la interacción con los cuerpos de agua, la vegetación ribereña tiene una forma lineal característica y constituye una zona 17 Resumen: Se analizó la estructura y la composición de la vegetación ribereña de la porción media-alta del río Tembembe, Morelos, México. Se registró la altura, el diámetro, la cobertura y la identidad taxonómica de cada individuo 1 cm D AP en 23 unidades de muestreo de 100 m 2 cada una. En total se registraron 74 especies y 516 individuos. La densidad promedio fue de 2,148 ind. ha -1 ; el área basal promedio de 88.39 m 2 ha -1 y la altura promedio (de individuos con DAP 20 cm) de 10.5 m. Con base en análisis de clasificación se distinguieron tres comunidades vegetales cuya distribución está asociada al gradiente altitudinal: la primera (G1) en la parte alta (1,700 -1,650 m s.n.m.), con especies dominantes de afinidad holártica (como Alnus acuminata); la segunda (G2) en la parte media (1,640 -1,340 m s.n.m.), dominada por Trema micrantha; y la tercera (G3) en la porción baja (1,210 -1,110 m s.n.m.), dominada por especies de afinidad neotropical, como Daphnopsis salicifolia. La diversidad, la densidad y la cobertura no difirieron significativamente entre las tres comunidades, pero el área basal fue mayor en las comunidades alta y baja que en la intermedia. La altura promedio del estrato arbóreo disminuyó con la altitud. El presente estudio cont ri bu ye al conocimiento de la vegetación ri b e reña del estado de Morelos y pro p o rciona info rmación ecológica básica para futuro s programas de restauración de la vegetación ribereña del río Tembembe. Palabras clave: composición florística, diversidad florística, estructura de la vegetación, gradiente altitudinal, vegetación ribereña.Abstract: Structure and composition of the riparian vegetation of the middle-upper basin of the Tembembe river, in the state of Morelos, was analyzed. Height, diameter at breast height, crown area and taxonomic identity of each individual having a DBH 1 cm were recorded in 23 quadrats of 100 m 2 each. A total of 74 species and 516 individuals were found. Mean density was 2,148 ind. ha -1 , mean basal area was 88.39 m 2 ha -1 , and mean height (of individuals with DBH 20 cm) w as 10.5 m. Classification analysis allowed the discrimination of three communities whose distribution was associated to the altitudinal gradient: the first (G1) in the upper part (1,700 -1,650 m a.s.l.) was dominated by species (like Alnus acuminata) having a holartic affinity; the second (G2) at an intermediate altitude (1,640 -1,340 m a.s.l.) was dominated by Trema micrantha; and the third (G3) in the lower portion (1,210 -1,110 m a.s.l.) dominated by species (like Daphnopsis salicifolia) having a tropical affinity. Diversity, density and crown cover did not differ among them, but mean basal area was largest in the highest ...

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Question: Which is the response of the evergreen Quercus ilex and the deciduous Q. cerrioides to repeated disturbances? Location: central Catalonia (northeastern Spain), in the areas affected by two of the largest historically recorded wildfires in NE Spain: the Bages‐Berguedà fire (24 300 ha forested area burned in July 1994), and the Solsonès fire (14 300 ha burned in 1998). Methods: Survival and growth of individuals of Quercus ilex and Q. cerrioides were evaluated in plants subjected to different fire histories and experimental disturbances (burning, cutting or clipping) applied either before or after summer. Results: Survival was high (> 99%), with both species showing a similar high resistance to disturbances. Growth after experimental disturbance was positively related to the size of the individual before the latest forest fire occurred. Fire history had a large effect on resprout growth, as the repeated incidence of disturbances lowered the capacity of individuals to grow. The type and season of experimental disturbance experienced by plants had a large effect. Individuals that experienced total above‐ground loss had lower growth rates than those with partial loss. A similar pattern was observed in individuals disturbed after the summer in relation to those disturbed before summer. Conclusions: The larger growth rates recorded in Q. cerrioides across all fire histories and experimental treatments, and the higher vulnerability of Q. ilex to increased fire frequency, intensity of experimental disturbance, and disturbance season, provide evidence for the relatively high susceptibility of the latter to repeated disturbances. This view disagrees with the larger resilience of this species compared to co‐existing deciduous oaks, as reported.

With the aim of providing information for ecological restoration programs, we studied reproductive phenology and seed germination of eight species from the tropical dry forest of Morelos, Mexico. With the participation of students from the local junior high school, we monitored monthly, over one year, the production of flowers and immature and mature fruits for each species. We estimated intensity, duration, seasonality, and synchrony for each fruiting phenophase and flowering duration. Germination tests were undertaken in a germination chamber (18 C-32 C) and under the environmental conditions at the local school. We applied specific pregermination treatments for each species. Two distinct peaks of mature fruit production were identified: one at the beginning and the other in the middle of the dry season. Fructification seasonality was significant in most cases. Germination was relatively high in three legumes and particularly low in two Bursera species. Four species responded to the germination environments, and differences among pregermination treatments were significant in most cases. Knowledge on fruiting patterns and seed viability and germination will allow adequate decision-making for seed collection and plant propagation of the study species. Student participation increased their interest and knowledge on local environmental problems and solutions.