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Premise of the Study Deciduous tree species remove some nutrients from their leaves during fall leaf senescence through retranslocation. Retranslocation impacts the timeline of leaf fall, amount of active chlorophyll, and overall leaf nitrogen content as fall color change occurs. Our objective was to identify interspecific differences in the timing of abscission layer formation, leaf color change, and the level of chlorophyll degradation of young trees during fall senescence. Methods Leaf relative chlorophyll content for three tree species was measured during fall 2015 by a greenness meter. These measurements were calibrated for each species through spectrophotometric determination of leaf chlorophyll concentration. Abscission layer formation was tracked using light microscopy of sampled leaves. Excised leaves were photographed on a flat white surface to track species leaf color through time. Key Results All three species had different chlorophyll declination rates throughout the fall season. The maple species started with less chlorophyll and began abscission layer formation earlier. The other two species had a similar starting chlorophyll level and onset timing of abscission layer formation. Visible leaf color change was not associated with a threshold in either chlorophyll degradation or abscission layer formation across species. Conclusions Maple species degraded less chlorophyll on average, in the fall, than did the oak and beech species. The rate of chlorophyll degradation in coordination with abscission layer formation varied by species. Color change was not a good predictor of level of chlorophyll degradation in leaves across species.

An estimated 3.4 million hectares of cocoa and 9.7 million hectares of coffee are cultivated, globally, under shade trees, i.e. in agroforestry systems. Shade canopies are characterized in terms of tree density (N, trees ha−1), tree basal area (G, m2 ha−1) and percent canopy cover (%Cov). N, G and %Cov are named shade canopy density variables (SCDV). The use of these SCDV has two important limitations: (1) different combinations of values of the three SCDV variables generate very different shade tree stands (hence very different shading levels), and (2) Additional factors modify shading under shade canopies with constant SCDV values. This article uses the software ShadeMotion (www.shademotion.net) to show how 24 different, simple, even-sized, mono-layered, Cordia alliodora shade canopies with constant N, G and %Cov display significantly different shade levels and temporal patterns of shading depending on tree stem and crown diameter ratios, tree height, spatial planting configurations (square, random and alleys) and leaf fall patterns. A minimum set of variables capable of providing a more accurate description of the shading characteristics of a cocoa or coffee shade canopy is proposed. Our findings can shed light on the current debate on the pros and cons of the definitions of cocoa agroforestry used by chocolate and certification companies, governments, non-governmental organizations, and donors, especially in West and Central Africa. In this article, emphasis is given to cocoa, but the analysis, results and conclusions are equally applicable to coffee agroforestry systems.

Leaf fall disease is a significant factor contributing to the decline in rubber plant production. Global climate change has altered temperature, humidity, and rainfall, impacting the dynamics of this disease by often increasing its severity and broadening its geographical distribution. This disease, affecting rubber plants, is primarily caused by various fungal pathogens, including Colletotrichum spp., Pestalotiopsis spp., and Phytophthora spp. The emergence and spread of these pathogens are closely associated with environmental conditions. This study investigates how climatic variables influence the development and distribution of leaf fall disease, with the goal of informing the development of effective management strategies. The research focuses on rubber plantations in Southeast Asia, specifically in Indonesia, Malaysia, and Thailand. This study synthesizes scientific literature that examines the correlation between climate change and diseases affecting rubber plants, as well as the evolutionary dynamics of the associated fungal pathogens. The literature review underscores that climate change plays a crucial role in affecting rubber plant productivity in relation to pathogen dynamics and overall plant health. Moreover, the rise in environmental temperatures linked to climate change encourages the growth and development of leaf fall disease pathogens in rubber plants. In addition, without proper mitigation efforts, the continued progression of climate change may lead to more frequent and severe outbreaks, further jeopardizing rubber production and farmer livelihoods.

The Cerrado vegetation types has the same macroclimate, but differs in the microclimatic and edaphic proprieties, which can result in contrasting phenologies among it. The vegetative phenology of five vegetation types such as woody savanna, deciduous and semideciduous forests, gallery forest, and riparian forest in Brazil Central plateau were accessed in this study. Leaf falls and leaf budding of 10 individuals of the 12 most abundant species were evaluated monthly in each vegetation type over one year. Circular statistics and the Rayleigh test were used to assess the phenology peaks. The average intensity rate of leaf fall and leaf budding were calculated for each vegetation type and chi-square test was used to analyse differences among them. Of the 53 species studies, 15 were deciduous, 17 semideciduous and 21 evergreens. All vegetation types demonstrated seasonality, reflecting the season macroclimate predominance. However, the peaks of phenophases were different between them throughout the year, which in turn reflects the effect of the microclimatic and edaphic proprieties. Our results indicated that within the same remnant a greater number of forests patches may increase phenological strategies. Thus, several vegetation types ensured resources for associated fauna and ecosystem services at different periods of the year.

Information on the onset of leaf senescence in temperate deciduous trees and comparisons on its assessment methods are limited, hampering our understanding of autumn dynamics. We compare five field proxies, five remote sensing proxies and two data analysis approaches to assess leaf senescence onset at one main beech stand, two stands of oak and birch, and three ancillary stands of the same species in Belgium during 2017 and 2018. Across species and sites, onset of leaf senescence was not significantly different for the field proxies based on Chl leaf content and canopy coloration, except for an advanced canopy coloration during the extremely dry and warm 2018. Two remote sensing indices provided results fully consistent with the field data. A significant lag emerged between leaf senescence onset and leaf fall, and when a threshold of 50% change in the seasonal variable under study (e.g. Chl content) was used to derive the leaf senescence onset. Our results provide unprecedented information on the quality and applicability of different proxies to assess leaf senescence onset in temperate deciduous trees. In addition, a sound base is offered to select the most suited methods for the different disciplines that need this type of data.

Non‐native understorey woody species have been shown to extend leaf display and inhabit vacant phenological niches in early spring and late autumn when growing with native counterparts in temperate deciduous forests across the world. Despite the potential competitive advantages, extended leaf duration also subjects non‐native species to possible hydraulic risks associated with maintaining leaves during periods of increased frost probability. It remains unclear how non‐native species are able to maintain xylem function within this context. Leaf phenology in temperate deciduous trees has been shown to be a function of xylem anatomy, with earlier bud break associated with smaller xylem vessels due to the presumed resistance of smaller vessels to freezing‐induced cavitation. We examined relationships between leaf phenology and xylem vessel traits across 82 native and non‐native understorey deciduous woody species common to eastern U.S. deciduous forests. We hypothesized that non‐native species possess xylem vessel traits associated with maximum hydraulic safety during frost‐prone spring and autumn leaf display without compromising rapid growth rate. Larger metaxylem vessels in non‐native species were associated with both faster spring growth and delayed autumn leaf fall compared to native species. Non‐native species also had smaller latewood vessel diameter, latewood vessel area percentage and a higher proportion of solitary vessels in the entire secondary xylem cross section compared to natives, potentially increasing their resistance to freezing‐ and/or drought‐induced cavitation in autumn, thus allowing for delayed autumn leaf fall. Native and non‐native species exhibited similar dates of spring bud break and leaf emergence, consistent with similar xylem vessel size and vessel area percentage within metaxylem and earlywood. Within both groups, species with earlier bud and leaf emergence had a higher total percentage of vessel area within metaxylem and earlywood. This suggests understorey species need sufficient water to support their early spring growth at the risk of freezing‐induced cavitation. Our study suggests xylem vessel properties, along with cross‐sectional spatial xylem vessel distribution, reflect the capacity of non‐native plants to thrive in a new environment and deepen our understanding of the physiological mechanisms of successful invasions of non‐native understorey woody plant species.

Rubber tree Corynespora leaf fall (CLF) disease, caused by the fungus Corynespora cassiicola, is one of the most damaging diseases in rubber tree plantations in Asia and Africa, and this disease also threatens rubber nurseries and young rubber plantations in China. C. cassiicola isolates display high genetic diversity, and virulence profiles vary significantly depending on cultivar. Although one phytotoxin (cassicolin) has been identified, it cannot fully explain the diversity in pathogenicity between C. cassiicola species, and some virulent C. cassiicola strains do not contain the cassiicolin gene. In the present study, we report high-quality gapless genome sequences, obtained using short-read sequencing and single-molecule long-read sequencing, of two Chinese C. cassiicola virulent strains. Comparative genomics of gene families in these two stains and a virulent CPP strain from the Philippines showed that all three strains experienced different selective pressures, and metabolism-related gene families vary between the strains. Secreted protein analysis indicated that the quantities of secreted cell wall-degrading enzymes were correlated with pathogenesis, and the most aggressive CCP strain (cassiicolin toxin type 1) encoded 27.34% and 39.74% more secreted carbohydrate-active enzymes (CAZymes) than Chinese strains YN49 and CC01, respectively, both of which can only infect rubber tree saplings. The results of antiSMASH analysis showed that all three strains encode ~60 secondary metabolite biosynthesis gene clusters (SM BGCs). Phylogenomic and domain structure analyses of core synthesis genes, together with synteny analysis of polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) gene clusters, revealed diversity in the distribution of SM BGCs between strains, as well as SM polymorphisms, which may play an important role in pathogenic progress. The results expand our understanding of the C. cassiicola genome. Further comparative genomic analysis indicates that secreted CAZymes and SMs may influence pathogenicity in rubber tree plantations. The findings facilitate future exploration of the molecular pathogenic mechanism of C. cassiicola.

Litter production in natural and reforested mangrove areas was measured for a one-year cycle, from July 2105 to June 2016, in three sites: Bais (Negros Oriental), Alcantara (Cebu Province), and Pangangan Island (Bohol Province). In Bais, total litter production was higher in natural mangrove forests with mean of 8.38 g m-2 day-1 (n = 12, SD = 3.75) than in reforested mangrove forests with mean of 3.45 g m-2 day-1 (n = 12, SD = 1.92). There was no significant correlation between monthly litter production and monthly rainfall (Pearson's r = 0.195; p = 0.544, n = 12). Based on quarterly data, leaf fall production was higher in natural mangrove forests than in reforested mangrove areas. Among the three sites, leaf fall production was higher in natural forest in Alcantara with mean of 7.43 g m-2 day-1 (n = 20, SD= 4.33) followed by Pangangan Island 7.06 g m-2 day-1 (n = 24, SD= 3.98) and Bais with the value of of 6.04 g m-2 day-1 (n = 24, SD = 1.89) whereas in reforested mangrove forests, the leaf fall production was observed to be higher in Pangangan Island with the value of 6.52 g m-2 day-1 (n = 24, SD = 2.78), followed by Alcantara with the value of 6.22 g m-2 day-1 (n = 20, SD = 3.29) and Bais with the value of 2.69 g m-2 day-1 (n = 32, SD =1.78). For the litter components, leaves were the main components, followed by fruits, twigs, flowers, and miscellaneous. This study showed that the natural mangrove forest has high production values of litter compared to the reforested mangrove area.

β-1,3-glucanases play a major role in combating the abnormal leaf fall disease (ALF) caused by the oomycete Phytophthora spp. in Hevea brasiliensis, the major commercial source of natural rubber. In this study, partial sequences of four novel promoters of different β-1,3-glucanase genomic forms were amplified through inverse PCR from the H. brasiliensis clone RRII 105 and sequence characterized. This is the first report showing β-1,3-glucanase genes driven by a different set of promoter sequences in a single clone of Hevea. The nucleotide sequencing revealed the presence of 913, 582, 553 and 198 bp promoter regions upstream to the translation initiation codon, ‘ATG’, and contained the essential cis-elements that are usually present in biotic/abiotic stress-related plant gene promoters along with other complex regulatory regions. The amplified regions showed strong nucleosome formation potential and in two of the promoters CpG islands were observed indicating the tight regulation of gene expression by the promoters. The functional efficiency of the isolated promoter forms was validated using promoter: reporter gene (GUS) fusion binary vectors through Agrobacterium mediated transformation in Hevea callus and tobacco. GUS gene expression was noticed in Hevea callus indicating that all the promoters are functional. The transgenic tobacco plants showed no GUS gene expression. The implication of these novel promoter regions to co-ordinate the β-1,3-glucanase gene expression can be utilized for defense specific gene expression in future genetic transformation attempts in Hevea and in a wide variety of plant systems.

Trees in urban and industrial areas significantly help to limit the amount of particulate matter (PM) suspended in the air, but PM has a negative impact on their life. The amount of PM gathered on leaves depends on quantity, size, and morphology of leaves and can also be increased by the presence of epicuticular waxes, in which PM can become stuck or immersed. In this study, we determined the ability of PM to accumulate on leaves in relation to the species of tree and PM source. We tested saplings of three common European tree species ( Betula pendula , Quercus robur , and Tilia cordata ) by experimentally polluting them with PM from different sources (cement, construction, and roadside PM), and then assessing the effects of PM on plant growth and ecophysiology. In all studied species, we have found two types of PM accumulation: a layer on the leaf surface and an in-wax layer. Results showed that the studied species accumulate PM on their leaf blade, reducing the efficiency of its photosynthetic apparatus, which in a broader sense can be considered a reduction in the plants’ normal functioning. Saplings of Q. robur suffered the least, whereas B. pendula (especially photosynthetic rate and conductivity) and T. cordata (especially increase in leader shoot length) exhibited greater negative effects. The foliage of B. pendula collected the most PM, followed by Q. robur , and then T. cordata , regardless of the dust’s source. All tested species showed a tendency for higher wax production when growing under PM pollution stress. We believe that, potentially, B. pendula best enhances the quality of the PM-contaminated environment; however, faster leaf fall, reduced productivity, and worse quality of wood should be considered in urban forest management.