Age-dependent bark photosynthesis of aspen twigs

The photosynthetic performance of trembling aspen (Populus tremula L.) twigs and leaves was studied in relation to selected structural features of aspen bark. PFD transmittance of intact periderm was reduced by about 90% in current-year twigs through peridermal thickening. However, because of drastic changes within the bark microstructure, PFD transmittance increased in 1-year-old twig segments up to 26% of the incident PFD. On a unit surface area basis, the chlorophyll content of young twigs (425 mg Chl m^-2) almost reached that of leaves (460 mg Chl m^-2). The chlorophyll content of aspen bark chlorenchyma was clearly age-dependent, even increasing in current-year twigs with advancing internodal age. The low bark chlorophyll a/b ratios (about 2.6 compared with 3.9 in leaves) indicate that bark chloroplasts are shade-adapted. Positive net photosynthesis was not found in aspen twigs, but apparent respiration was distinctly reduced in the light due to light-driven carbon refixation (bark photosynthesis) within the chlorenchymal tissues. Under constant microclimatic conditions, dark respiration rates were strongly correlated with stem-internal CO₂ refixation. In accordance with increasing dark respiration rates, the efficiency of this carbon recycling was generally greater in the metabolically more active, younger twig segments than in older segments; carbon refixation rates reached up to 80% of dark respiration values. At least in young twigs and branches and thus in the light-exposed outer parts of tree crowns, respiratory CO₂ losses by the tree skeleton could efficiently be reduced. Refixation of carbon dioxide may be of great importance for carbon budgets in the environmentally controlled or pathogen-induced leafless states of deciduous aspen trees.     

地域环境对青藏高原特有植物藏川杨生物学特性的影响

通过对西藏中、南部16个藏川杨种源地环境特征、植株和枝叶形态特征、生长习性等生物学特性的观测比较,发现藏川杨为高大、长寿乔木,株龄逾千年、株高达45 m、冠幅22 m,分布海拔高度2000～4500 m、分布区域跨越湿润、半湿润、半干旱和干旱区,随着分布区环境变化,不同种源藏川杨的树皮、枝条、芽、叶等形态特征呈现规律性变化,空气湿度增加、树干颜色变深、枝条被毛加重、顶生冬芽变窄、叶片长/宽比增加;半湿润区和灌溉区植株的叶面积、枝条长度增加,湿润区、阴湿地或环境条件恶劣地区植株叶片和枝条生长不佳,枝条干湿比相对较小。结果表明:藏川杨具有很强的环境适应能力和可塑性,耐旱,喜光、抗强光辐射,耐贫瘠、喜中性或弱碱性土壤,具有很高的生态和经济价值。     

Fallen leaves and unpalatable plants as alternative foods for sika deer under food limitation

Feeding behavior and rumen contents of sika deer (Cervus nippon Temminck) under food limitation were studied on Nakanoshima Island, Hokkaido. During the phase of population growth, the deer subsisted on tree bark and twigs, deciduous leaves and dwarf bamboos (Sasa spp.) in the winter. After a crash in population, the deer began feeding on the fallen leaves of deciduous trees and continued to do so throughout the year. They also ate unpalatable plants Cephalotaxus harringtonia var. nana Rehd., Senecio cannabifolius Less. and Cynanchum caudatum Maxim. as winter foods, which used to remain untouched by deer, and had accordingly expanded their distributions, following a decrease in the amount of dwarf bamboos available. These facts suggest that sika deer drastically shift their foods and exploit alternative foods under conditions of food limitation.     

Himalayan <Emphasis Type="Italic">Semnopithecus entellus</Emphasis> at Langtang National Park,Nepal: Diet,Activity Patterns,and Resources

Though researchers have studied lowland gray langurs extensively, there is little information about the Himalayan populations. We provide foraging data from a field study of Himalayan langurs in Langtang National Park, Nepal at 3000–4000 m elevation. Phenological records show marked seasonality in resource abundance, with extremely low availability in winter, increasing abundance in spring and monsoon, and a reduction in fall. Activity budgets indicated greater time devoted to feeding as total vegetation abundance decreased. Diet included leaf buds, ripe fruit, and evergreen mature leaves in winter; deciduous young leaves in spring; and deciduous mature leaves in the monsoon and fall. Supplemental resources, such as underground storage organs, bark, and herbaceous vegetation, were also seasonally important. Among plant part classes included in the phenological sample, abundance and consumption correlate positively for all primary food resources except evergreen mature leaves and unripe fruit. Daily path lengths varied by season and, when controlled for overall vegetation abundance, positively relate to the consumption of soft underground storage organs, fruits, and deciduous mature leaves. The results contradict the common generalization of leaves as ubiquitous or nonpatchy resources.     

The Narrow Niche hypothesis: gray squirrels shed new light on primate origins

Current hypotheses for primate origins propose that nails and primate-like grasping hands and feet were important early adaptations for feeding in fine branches. Comparative research in this area has focused on instances of convergence in extant animals, showing that species with primate-like morphology feed predominantly from terminal branches. Little has been done to test whether animals without primate-like morphology engage in similar behavior. We tested the fine-branch niche hypothesis for primate origins by observing branch use in Eastern gray squirrels, Sciurus carolinensis, a species lacking primate grasping adaptations that has been understudied in the context of primate origins. We hypothesized that because gray squirrels lack primate-like grasping adaptations, they would avoid feeding and foraging in terminal branches. Instantaneous focal animal sampling was used to examine the locomotor and postural behaviors used while feeding and foraging. Our results demonstrate habitual and effective usage of terminal branches by gray squirrels while feeding and foraging, primarily on tree seeds (e.g., oak, maple, and elm). Discriminant function analysis indicates that gray squirrels feed and forage like primates, unlike some other tree squirrel species. Given the absence of primate-like features in gray squirrels, we suggest that although selection for fine-branch foraging may be a necessary condition for primate origins, it is not sufficient. We propose an alternative model of primate origins. The Narrow Niche hypothesis suggests that the primate morphological suite evolved not only from selection pressure for fine branch use, but also from a lack of engagement in other activities.     

Epiphytic vegetation on pollarded trunks of Fraxinus excelsior in four different habitats at Grinde,Leikanger, western Norway

The epiphytic vegetation on 24 pollarded trees of Fraxinus excelsior at the farm Grinde, Leikanger, western Norway was investigated. Each trunk was divided into a basal zone, a middle zone and a top zone. In each zone the four different aspects were analysed (12 sampling units from each trunk). Within a total of 276 sampling units, 162 taxa were recorded (99 lichens, 56 bryophytes, 7 vascular plants). The trunks were covered mainly by an old, thick and occasionally swollen bark, but decaying wood did not occur. Their habitats were different, and each trunk was classified into one of four categories: open meadow, wooded hay meadow, deciduous wood, and spruce plantation. A climate station was established in each habitat to measure important parameters. The floristic and environmental data were analysed by canonical correspondence analysis (CCA). The floristic data were classified into eight TWINSPAN groups that have been taken into account in the CCA diagrams. At Grinde all the pollarded trunks grew under fairly homogeneous conditions during a more extensive agricultural period until about 1962. The deciduous wood developed by tree colonization on old meadows and wooded hay meadows, whilst spruce has been planted in a small part of the area. Floristic differences in the epiphytic vegetation between the four different habitats were found, which suggests that changes in the vegetation have developed during the last two or three decades. The spruce plantation was the most shady habitat having a very sparse epiphytic vegetation, mainly remnants from vegetation established during more open area conditions.     

The Argentine ant persists through unfavorable winters via a mutualism facilitated by a native tree

Mutualisms and facilitations can fundamentally change the relationship between an organism's realized and fundamental niche. Invasive species may prove particularly suitable models for investigating this relationship as many are dependent on finding new partners for successful establishment. We conducted field-based experiments testing whether a native tree facilitates the successful survival of the invasive Argentine ant, Linepithema humile (Mayr), through unfavorable winter conditions in the southeastern United States. We found Argentine ant nests aggregated around the native loblolly pine, Pinus taeda L., during the winter months. The bark of this tree absorbed enough radiant solar energy to reach temperatures suitable for Argentine ant foraging even when ambient temperatures should have curtailed all foraging. Conversely, foraging ceased when the trunk was shaded. The sun-warmed bark of this tree gave the Argentine ant access to a stable honeydew resource. Argentine ants were not found on or near deciduous trees even though bark temperatures were warm enough to permit Argentine ant foraging on cold winter days. Augmenting deciduous trees with sucrose water through the winter months lead to Argentine ant nests remaining at their base and Argentine ants foraging on the tree. The Argentine ant requires both foraging opportunity and a reliable winter food source to survive through unfavorable winter conditions in the southeastern United States. The loblolly pine provided both of these requirements extending the realized niche of Argentine ants beyond its fundamental niche.     

Evaluation of various parts of the paw paw tree, Asimina triloba (Annonaceae), as commercial sources of the pesticidal annonaceous acetogenins.

Various plant parts of the paw paw tree (Asimina triloba Dunal, Annonaceae) were extracted and partitioned to concentrate the mixture of acetogenins into a standardized pesticidal extract (F005). A bioassay with brine shrimp larvae (Artemia salina Leach) was used to determine the relative potencies of the various extracts. The small twigs (0-0.5 cm diameter) yielded the most potent extract (LC50 = 0.04 ppm); the stem wood (LC50 = 4.9 ppm) and leaves (LC50 = 53.7 ppm) yielded the poorest activities. The unripe fruits, seeds, root wood, root bark, and stem bark were notably potent and, generally, yielded > 2% of their dry weight as F005. The smaller diameter stems were more potent than the larger stems. We conclude that, by pollarding the trees, the entire twigs and small branches of paw paw could be processed to produce a potent acetogenin mixture; this biomass could be made available in quantities needed for commercialization of the pesticidal product and could be renewable through regrowth from the parent trunk and larger branches.     

不同林龄巨尾桉的灰分含量和热值

采用热量仪和马福炉对1～4年生4个不同林龄阶段巨尾桉的叶、枝、根、干、皮5个部位进行灰分含量和热值测定,结果表明:不同林龄巨尾桉其5个部位的平均灰分含量在(0.42±0.14)%～(4.43±1.35)%之间,以皮的最高、干的最低,各部位灰分含量的大小排列顺序无一相同且无明显的规律可循,除根外,叶、枝、干、皮在林分4个...     

Crows break off live camphor twigs: an avian disturbance effect on plants

Birds are usually considered beneficial partners for plants, acting as predators on herbivorous insects, pollinators and seed dispersal agents. However, in an urban area of central Japan, birds break off large quantities of live camphor tree ( Cinnamomum camphora ) twigs in winter. This loss of vegetative parts was examined quantitatively to estimate the impact on the trees. I also observed bird foraging behaviour to determine the species involved and the possible reasons underlying this destructive activity. Broken twigs on the forest floor were found to have numerous leaves and spring buds. The densities of leaves and buds in the litter were 288.5 and 54.4 m⁻², respectively. The jungle crow ( Corvus macrorhynchos ) may have broken off the twigs either to peck the fruits while perching on stable branches, or possibly to remove twigs obstructing access to fruit. In contrast, brown-eared bulbuls ( Hypsipetes amaurotis ), oriental turtle doves ( Streptopelia orientalis ) and rove doves ( Columba livia ) ate fruits without breaking twigs. The interaction between C. camphora and C. macrorhynchos only extends back for about 20 years in urban Japan, indicating that this is unlikely to be a stable, co-evolved relationship.     

Sex differences in giraffe foraging behavior at two spatial scales

We test predictions about differences in the foraging behaviors of male and female giraffes (Giraffa camelopardalis tippelskirchi Matchie) that derive from a hypothesis linking sexual size dimorphism to foraging behavior. This body-size hypothesis predicts that males will exhibit specific behaviors that increase their dry-matter intake rate relative to females. Foraging behavior was examined at two hierarchical levels corresponding to two spatial and temporal scales, within patches and within habitats. Patches are defined as individual trees or shrubs and habitats are defined as collections of patches within plant communities. Males were predicted to increase dry-matter intake rate within patches by taking larger bites, cropping bites more quickly, chewing less, and chewing faster. Within habitats, males were expected to increase intake rate by increasing the proportion of foraging time devoted to food ingestion as opposed to inter-patch travel time and vigilance. The predictions were tested in a free-ranging population of giraffes in Mikumi National Park, Tanzania. Males spent less total time foraging than females but allocated a greater proportion of their foraging time to forage ingestion as opposed to travel between patches. There was no sex difference in rumination time but males spent more time in activities other than foraging and rumination, such as walking. Within patches, males took larger bites than females, but females cropped bites more quickly and chewed faster. Males had longer per-bite handling times than females but had shorter handling times per gram of intake. Within habitats, males had longer average patch residence times but there was no significant sex difference in inter-patch travel times. There was no overall difference between sexes in vigilance while foraging, although there were significant sex by habitat and sex by season interactions. Although not all the predictions were confirmed, overall the results agree qualitatively with the body-size hypothesis. Sex-related differences in foraging behavior led to greater estimated intake rates for males at the within-patch and within-habitat scales. Received: 20 November 1995 / Accepted: 5 November 1996     

Changes in the δ13C values of trees during a tropical rainy season: some effects in addition to diffusion and carboxylation by rubisco?

The d13C values of deciduous and evergreen tree leaves were compared in open and closed- canopy environments throughout a rainy season in Panamá. Newly emerging leaves had higher d13C values than older leaves of all seedlings and trees at all dates sampled. This was apparently not caused by a decline in water use efficiency as leaves develop because instantaneous ci/ca was significantly higher in newly emerging than in expanded leaves on the same twigs of trees in the field as well as on seedlings growing in a controlled, unchanging environment. Higher d13C values in newly emerging leaves occurred across diverse environmental comparisons. For example, leaves emerging during the rainy season had higher d13C values than corresponding mature leaves that had emerged both during the dry season and when water was abundant. The early enrichment in 13C may thus reflect the translocation of carbon to initiate a new leaf. Furthermore, the lack of sensitivity of this enrichment to a microclimate suggests that it might be the result of processes that occur after carbon fixation by Rubisco. Other changes in d13C values as leaves developed may also have resulted from carbon translocation processes. Foliar d13C decreased significantly after most of the leaf biomass of the deciduous Apeiba membranacea had developed. The d13C values of the evergreen Cecropia insignis were lower in the open canopy than in closed-canopy forests at the end of the rainy season. These findings suggest that the d13C values of leaves can yield ecological information about the allocation of carbon within trees.     

大别山山地次生林鸟类群落集团结构的季节变化

2007年12月—2008年12月,在大别山鹞落坪,对落叶阔叶次生林鸟类的集团结构的季节变化特征进行了研究。采用连续取样法采集鸟类取食行为数据,用聚类分析法对繁殖和非繁殖季节鸟类群落进行集团划分,通过无倾向对应分析（DCA）对32种森林鸟类的两个季节资源利用特点进行了研究。结果表明,鸟类群落在非繁殖季节可以分为地面、灌丛、树干（枝）、冠层等4个取食集团,而在繁殖季节还出现空中取食集团;候鸟影响鹞落坪次生林鸟类群落取食集团的结构,产生新的取食集团。DCA的第一轴主要代表鸟类取食高度信息,第二轴主要代表鸟类取食位置信息,第三轴代表鸟类取食方式和取食基质信息;用DCA前两轴对32种鸟类排序表明,有6种鸟主要在第一轴发生变化,有4种鸟主要在第二轴发生变化。     

Foraging enrichment alleviates oral repetitive behaviors in captive red-tailed black cockatoos (Calyptorhynchus banksii)

The relationship between inadequate foraging opportunities and the expression of oral repetitive behaviors has been well documented in many production animal species. However, this relationship has been less-well examined in zoo-housed animals, particularly avian species. The expression of oral repetitive behavior may embody a frustrated foraging response, and may therefore be alleviated with the provision of foraging enrichment. In this study, we examined the effect of different foraging-based enrichment items on a group of captive red-tailed black cockatoos who were previously observed performing oral repetitive behavior. A group of six cockatoos were presented with five foraging enrichment conditions (no enrichment (control), sliced cucumber, fresh grass, baffle cages, and millet discs). Baseline activity budgets were established over a 10-day preintervention period and interventions were then presented systematically over a 25-day experimental period. This study demonstrated that the provision of foraging interventions effectively increased the median percentage of time spent foraging compared to control conditions (range, 5.0–31.7% across interventions vs. 5.0% for control), with two of the interventions; grass and millet discs, significantly decreasing the expression of oral repetitive behaviors (control = 16.6 vs. 8.3% for both grass and millet discs). Finally, a rapid-scoring method utilized by zookeepers during the study proved to be a useful proxy for the amount of time the cockatoos spent interacting with the foraging interventions and overall time spent foraging.     

Use of the forest canopy by the agile gibbon

Brachiation was the main form of locomotion and took place along branches and boughs in the upper canopy. The posture during feeding depended on the substrate, with the gibbons sitting on branches but hanging in twigs. During foraging the gibbons hung more, even on branches, but as only short stops were made this is probably to increase mobility. Feeding on fruit took place mainly in the middle canopy on small trees; feeding on leaves and foraging occurred evenly throughout the middle and upper canopies. Gibbons are light mobile animals with a rapid and direct form of locomotion that enables them to exploit dispersed food sources and to defend a large territory.     

几种树木的树皮中绿色组织的光合特性初探

测定10个树种树木上的三年生枝条树皮内绿色组织的叶绿素含量、光合速率和枝干的呼吸速率的结果表明：10个树种树皮内叶绿素含量为0.0649～0.3460mg·g^-1（FW）,叶绿素a/b为1.05～1.91,均低于叶片或针叶;树皮内绿色组织的光合速率为0.21（红松）～2.06（水曲柳）μmol（O2）·m^-2·s^-1,枝干呼吸速率1.76（红松）～3.21（落叶松）μmol（O2）·min^-1·g^-1（FW）。树皮内绿色组织的光补偿点（LCP）、光饱和点（LSP）低于叶片,而表观量子效率（AQY）高于叶片或针叶。据此认为,树皮内绿色组织适应于阴生环境,所以有较强的耐阴能力。     

Frustrated Appetitive Foraging Behavior,Stereotypic Pacing,and Fecal Glucocorticoid Levels in Snow Leopards (Uncia uncia) in the Zurich Zoo

One common visitor complaint in zoos is that the nonhuman animals are not visible. This problem needs to be resolved without compromising the animals' welfare; environmental enrichment could solve the problem. This study investigated whether enrichment would increase public exposure time of lowland tapir (Tapirus terrestris) in the Belo Horizonte Zoo in Minas Gerais, Brazil. Observations were made before (62 hr) and during (62 hr) the introduction of enrichment using focal animal sampling with instantaneous recording of behavior. The 5 enrichment items were a bamboo fence covered in vines, logs, a sandbox, dry leaves, and bamboo bushes. Before the enrichments were applied, the tapir was not visible to the public for more than 85% of the time. In addition, during the analysis of the enrichment treatment, other variables were considered—such as weekday, time of day, and weather conditions—which could influence the animals' interaction with the enrichments. The enrichments increased and decreased the expression of some behaviors; however, public viewing time of the animals did not increase. Thus, the enrichment applied was not strong enough to overcome the animals' crepuscular behavior.     

Effect of stem length to stem slender ratio of current-year twigs on the leaf display efficiency in evergreen and deciduous broadleaved trees

Aims Branches and leaves are the two main structural units of tree crown composition. Among the adaptive strategies of plants, the functional traits of branches and the relationships between branch traits and leaf traits determine the capacity of trees to access light and space. In this study, our objective is to test the hypothesis that leaf display efficiency is affected by the stem length to stem slender ratio within current-year twigs.Methods The stem length to stem slender ratios of current-year twigs were used as the proxy of stem structure traits. Leaf area ratio (total leaf area per stem mass), leaf density (leaf number per stem length) and leaf/stem mass ratio (total leaf mass per stem mass) were used as the proxies of leaf display efficiency. The relationship between stem structure traits and leaf display efficiency within current-year twigs were studied for 25 evergreen and 60 deciduous broadleaved woody species in Qingliang Mountain, Zhejiang, China. The standardized major axis estimation method was used to examine the scaling relationship between stem structural traits and leaf display efficiency within current-year twigs.Important findings The proxies of leaf display efficiency, measured by leaf area ratio, leaf density or leaf/stem mass ratio, were all significantly and negative correlated with stem length to stem slender ratio within current-year twigs in both evergreen and deciduous broadleaved woody species. This suggested that leaf display efficiency decreased with stem length to stem slender ratios within current-year twigs, which may reflect the role of mechanical safety and light within twigs. The slope of the relationship between leaf display efficiency and stem long-dimension structure traits in evergreen species was not significantly different from the one in deciduous species. In contrast, the y-intercept of the relationship between leaf density and stem long-dimension structure traits was significantly larger in evergreen species than in deciduous species, i.e. the leafing intensity of evergreen species was higher than that of deciduous species. Individual leaf area and specific leaf area were smaller in evergreen species than in deciduous species, which resulted in deciduous species have a larger leaf area per stem mass and leaf mass per stem mass at a given stem length to stem slender ratio compared to evergreen species. It may reflect the conservative adaptive strategy of high consumption and slow benefit in evergreen species. Our results demonstrated that leaf display efficiency could be affected by stem length, and would change with leaf life-span (deciduous versus evergreen).     

Hierarchical foraging by giraffe in a heterogeneous savannah,Tanzania

Understanding foraging decisions made by wildlife at different spatio‐temporal scales is important for wildlife management and conservation. We tested whether foraging decisions by Masai giraffe (Giraffa camelopardalis tippelskirchi Matschie) differed with scales; habitat, patch and tree in a heterogeneous savannah. We collected data from Arusha National Park, Tanzania, in March–May and August–October 2013. Visual observations were used to collect data on foraging behaviour. Measurements of tree height and stem height and scoring of accumulated browsing were made in 133 patches around trees where the giraffes had been seen browsing, and in a corresponding number of available patches. Giraffes selected Acacia shrub and Dodonea shrub habitats but not for water availability or predator avoidance. For patch use, giraffe selected high quantity of Acacia xanthophloea and Dodonea viscosa. Between plant species, A. xanthophloea was the most preferred and within plant species, tree quality was enhanced by tree height and high score of accumulated browsing. Generally, giraffes selected for A. xanthophloea at all scales.     

Taphonomy of the early Miocene flora, Hiwegi Formation, Rusinga Island, Kenya

A fossil flora was collected in situ from early Miocene deposits at site R117 in the Hiwegi Formation of Rusinga Island contemporaneous with and in close proximity to the sites from where the anthropoid primates were recovered. The flora exhibits a spatially and temporally patchy distribution of fruits and seeds, mixed with twigs of various sizes, fragments of wood, bark, and leaves, all with random orientations and very low depositional dips. There has been minimal transport and the flora evidently accumulated as in situ litter beneath local vegetation. Based on Nearest Living Relatives (NLR) of fruits and seeds, the vegetation represented is a deciduous broad-leaved woodland with continuous canopy, with trees, shrubs, lianas, and climbers, reminiscent of the structure of the modern vegetation in the steep-sided protected valleys in the Laetoli-Endulen area. The interpretation of the vegetation is supported by the presence of twigs, wood, and bark fragments from larger diameter axes. Climbers are represented by twining stem fragments as well as by a wide variety of distinctive fruits and seeds. The proportion of fossilised thorny twigs represents only 3% of the twig collections, and there are no unequivocal forest trees amongst the NLR. No grasses were present; monocotyledons are only represented by a single date palm stone. No conifer seeds or cones have been recovered, and there are no coniferous leafy shoots.