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Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the Cerrado, the sequential chaining of phenological events during the dry season is a pattern observed in many plant species. In this season, many plants completely lose their leaves, and soon after deciduous, there is an expressive production of leaf buds. In this study, we investigated the effect of irrigation and early defoliation on the triggering of leaf budding of the deciduous species Peixotoa tomentosa A.Juss. in the dry season of a seasonal environment with water restrictions. Therefore, we set up an experiment with three groups of plants: control (n = 15), irrigation treatment (n = 15), and removal treatment (n = 15), and after the complete deciduousness of the plants, we carried out phenological monitoring of the development of leaf buds in these plants. From July to August 2022, the leaf budding phenology of the 45 individuals was evaluated twice a week. To test whether there is a difference in the number of leaf buds between treatments, we built generalized linear mixed models (GLMMs). Plants in the removal treatment had a statistically higher number of leaf buds produced than the plants in the irrigation and control groups (P < 0.05). However, the control group and the irrigation treatment did not differ from each other (P > 0.05). We showed that early defoliation influenced the triggering of leaf buds in P. tomentosa, increasing the production of young leaves in their individuals in a seasonal environment with water restrictions. Irrigation was not able to break the dormancy of leaf buds. Our findings contribute to a better understanding of the triggering of vegetative phenophases in deciduous Cerrado plants, showing that leaf fall may play a more important role than rain in the production of leaf buds in the dry season. [ABSTRACT FROM AUTHOR]

Systemic neonicotinoid insecticides such as imidacloprid are increasingly applied against insect pest infestations on forest trees. However, leaves falling from treated trees may reach nearby surface waters and potentially represent a neonicotinoid exposure source for aquatic invertebrates. Given imidacloprid's susceptibility towards photolysis and high water solubility, it was hypothesized that the leaves' toxicity might be modulated by UV-irradiation during decay on the forest floor, or by leaching and re-mobilization of the insecticide from leaves within the aquatic ecosystem. To test these hypotheses, the amphipod shredder Gammarus fossarum was fed (over 7 d; n  = 30) with imidacloprid-contaminated black alder ( Alnus glutinosa ) leaves that had either been pre-treated (i.e., leached) in water for up to 7 d or UV-irradiated for 1 d (at intensities relevant during autumn in Central Europe) followed by a leaching duration of 1 d. Gammarids' feeding rate, serving as sublethal response variable, was reduced by up to 80% when consuming non-pretreated imidacloprid-contaminated leaves compared to imidacloprid-free leaves. Moreover, both leaching of imidacloprid from leaves (for 7 d) as well as UV-irradiation reduced the leaves' imidacloprid load (by 46 and 90%) thereby mitigating the effects on gammarids' feeding rate to levels comparable to the respective imidacloprid-free controls. Therefore, natural processes, such as UV-irradiation and re-mobilization of foliar insecticide residues in water, might be considered when evaluating the risks systemic insecticide applications in forests might pose for aquatic organisms in nearby streams. [ABSTRACT FROM AUTHOR]

There is increasing evidence that riparian corridors have modified thermal conditions compared to non-riparian areas. However, the biological significance of this difference is less clear. Here we tested this by investigating the response of tree phenology to riparian thermal conditions. We monitored the timing of bud burst, leaf fall and growing season of riparian and non-riparian ash ( Fraxinus excelsior L.) and sycamore ( Acer pseudoplatanus L.) in the city of Sheffield over two years. We compared the phenologies between riparian and non-riparian trees and explored the relationship between tree phenologies and thermal environments. Tree phenologies varied between riparian and non-riparian areas and the effect was species specific. Bud burst and leaf fall were earlier in non-riparian than in riparian ash, but no location effects on either bud burst or leaf fall were detected for sycamore, or in the growing season for both species. Bud burst for the two species was highly correlated to spring temperature; warmer temperature resulting in earlier bud burst in ash but later bud burst in sycamore. No significant relationship between leaf fall and temperature was found for either species. A positive correlation between growing season and temperature was observed for ash but not sycamore. [ABSTRACT FROM AUTHOR]

We evaluated the uncertainty in the estimation of year-to-year variability in the timing of leaf fall detected by the analysis of red, green and blue (RGB) values extracted from daily phenological images in a deciduous broad-leaved forest in Japan. We examined (1) the spatial distribution of individual tree species within a 1-ha permanent plot and the spatio-temporal variability of leaf litter of various species for 8 years; and (2) the relationship between the year-to-year variability of leaf fall detected by leaf litter and that detected by phenological images of various species. Uncertainties were caused by (1) the heterogeneous distribution of each species within the whole forest community; (2) the year-to-year variability of the timing of leaf fall among species; and (3) differences in leaf colouring and leaf fall patterns among species. Our results indicate the importance of integrating RGB analysis of each species and of the whole canopy on the basis of spatial locations of individuals and proportions of tree species within a forest to reduce uncertainty. [ABSTRACT FROM AUTHOR]

Copyright of Biota Neotropica is the property of Biota Neotropica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Within mature deciduous forests, annual development of foliar biomass is a major component of aboveground net primary production and nutrient demand. As litterfall, this same foliage becomes a dominant annual transfer of biomass and nutrients to the detritus pathway. We report litterfall transfers of a mature bottomland hardwood forest in a minor alluvial-floodplain within the middle Coastal Plain physiographic province of central Louisiana, USA. Climate is humid subtropical. Floodplain forests of minor alluvial-streams may account for nearly half the remaining acreage of bottomland forests in the Southeastern USA and differ markedly from those of major alluvial-rivers and deep-water swamps. For a 3-year period, litterfall magnitude, components, leaf species, and timing were monitored by monthly collection of materials from litterfall collectors. Variations in litterfall transfers across 10 study-plots and their relationships to forest parameters are evaluated. Mean transfers of total litterfall, leaf fall, reproductive structures, fine wood, and other litterfall were 816, 512, 130, 98, and 76gm−2 year−1, respectively. Quercus pagoda Raf., Q. nigra L., and Liquidambar styraciflua L. accounted for an average of 49% of annual leaf fall, with 11 tree species and canopy vines accounting for 94% of total annual leaf fall. A total of 38 species and genera contributed to total leaf fall. Variation in total litterfall and leaf fall transfers across the alluvial bottom were related to size of overstory trees and their species composition. Higher and more consistent mass transfers of reproductive structures were observed than previously reported for upland hardwood stands. [Copyright &y& Elsevier]

Abstract: Canopy phenology of Acacia tortilis ssp. raddiana, a dominant semi-deciduous species of the northern Sahelian zone, was monitored for 39 mature individuals, each month and bi-weekly in the rainy season, over a 5.5-year period in North Senegal. To investigate the relationships between leaf phenology and environmental variables, soil water availability and several climatic variables were monitored. Over six rainy seasons, annual rainfall ranged between 146 and 367mm. The full canopy stage lasted between 5 and 8 months, broadly including the rainy season (July–September) and the “cool” dry season (November–January). A significant inter-annual variation, up to 2.0 months, affects both the timing of the peaks of leaf flush and leaf fall. The canopy was maintained during the dry season despite low upper soil water availability and tree roots had access to a deep water table (31m). These results support the current view that in the dry tropics, groundwater availability is the major environmental variable controlling leaf phenology. However, inter-annual variation in the peaks of leaf flush and leaf fall could not be explained by ground water, genetics or day length. In such water-controlled biome, we focused on a comparison between two additional drivers, upper soil water availability and climatic variables which contribute to evaporative demand. Models predicting changes in canopy fullness from environmental variables were investigated by polynomial logistic regression. We considered each tree and pooled all the years, distinguishing periods of leaf flush (April–August) and leaf fall (January–April). Then, the ability of such models to predict inter-annual variation in the timing of peaks of leaf flush and leaf fall was tested. Inter-annual variation in the timing of leaf flush peak was well predicted by models based on air relative humidity or vapour pressure deficit or global radiation (root mean square error=0.5 month and R 2 =0.8). Inter-annual variation of leaf fall peak was also significantly predicted by models based on atmospheric variables (temperatures or maximum value of vapour pressure deficit) however with weaker relationships (root mean square error=0.7 month and R 2 =0.7). By contrast, models based on upper soil water availability or rainfall did not predict either leaf flush or leaf fall inter-annual variation. It appears that inter-annual variation of canopy phenology is mainly tuned to atmospheric conditions. Such behaviour maximizes the duration of high photosynthetic activity below a threshold of evaporative demand. [Copyright &y& Elsevier]