Influences of herbaceous vines on community characteristics in pioneer succession stages

In the continental tropics, herbaceous vines and lianas are roughly equal in abundance, and the former are even more abundant in the temperate region. However, only little attention has been paid to the study of biological and ecological characteristics of herbaceous vines. In particular, research about effects of herbaceous vines acting as a biological control on plant communities has not been carried out in depth. Herbaceous vines are widely distributed and abundant also in humid subtropical areas, especially in the early stages of forest community succession, but their ecology is little known. The aim of our study is to understand the effect of local herbaceous vines on community characteristics in pioneer succession stages. The hypothesis was tested that herbaceous vines would have predominantly negative effects on co-occurring species, thereby reducing their diversity. Based on a quadrate method, a detailed survey of shrub and herb communities covered by herbaceous vines was conducted in the Jinyun Mountain Nature Reserve of Chongqing, SW China. The sample plots were selected based on the numbers and coverage of vines, distinguishing among high vine coverage plots, middle vine coverage plots and low vine coverage plots. All species in the plots with different herbaceous vine coverage were identified and measured. The measurements for each species included number, average height and coverage. Because of abundant tree seedlings in the habitat of forest edge plots, we only recorded the number of tree seedlings in those plots to evaluate the overall effects of vines on tree seedling regeneration. After the field investigation, herbaceous vines and other species in the plots were harvested respectively, then oven dried and weighed. The results showed that herbaceous vines had high productivity and produced a lot of branches, which caused above-ground competition and mechanical stress to other species. Herbaceous vines seriously affected species composition and species importance values of self-supporting species. In all three habitats, the number of species and families in low coverage samples was larger than that in high coverage samples, and furthermore the identities of species were different between them. Species richness significantly decreased with increasing herbaceous vine coverage, illustrating that some species disappeared. Herbaceous vines reduced species diversity of communities, and as a result, community complexity was decreased, which might also decrease community stability. Biomass of communities of self-supporting species significantly decreased with increasing herbaceous vine coverage, which suggested that herbaceous vines significantly decreased community productivity. The number of seedlings also significantly decreased with increasing herbaceous vine coverage, and seedlings were mainly distributed in lower coverage samples. Herbaceous vines reduced the light exposure in the understory, which may be the mechanistic explanation for the negative influence of vines on the performance of tree seedlings. It was concluded that herbaceous vines affected seedling quantitative dynamics and distribution, and inhibited the natural succession from shrub and herb communities to tree communities. Thus herbaceous vines not only had significant influences on community characteristics in pioneer succession stages, but also on subsequent succession stages.     

Influences of herbaceous vines on community characteristics in pioneer succession stages

In the continental tropics, herbaceous vines and lianas are roughly equal in abundance, and the former are even more abundant in the temperate region. However, only little attention has been paid to the study of biological and ecological characteristics of herbaceous vines. In particular, research about effects of herbaceous vines acting as a biological control on plant communities has not been carried out in depth. Herbaceous vines are widely distributed and abundant also in humid subtropical areas, especially in the early stages of forest community succession, but their ecology is little known. The aim of our study is to understand the effect of local herbaceous vines on community characteristics in pioneer succession stages. The hypothesis was tested that herbaceous vines would have predominantly negative effects on co-occurring species, thereby reducing their diversity. Based on a quadrate method, a detailed survey of shrub and herb communities covered by herbaceous vines was conducted in the Jinyun Mountain Nature Reserve of Chongqing, SW China. The sample plots were selected based on the numbers and coverage of vines, distinguishing among high vine coverage plots, middle vine coverage plots and low vine coverage plots. All species in the plots with different herbaceous vine coverage were identified and measured. The measurements for each species included number, average height and coverage. Because of abundant tree seedlings in the habitat of forest edge plots, we only recorded the number of tree seedlings in those plots to evaluate the overall effects of vines on tree seedling regeneration. After the field investigation, herbaceous vines and other species in the plots were harvested respectively, then oven dried and weighed. The results showed that herbaceous vines had high productivity and produced a lot of branches, which caused above-ground competition and mechanical stress to other species. Herbaceous vines seriously affected species composition and species importance values of self-supporting species. In all three habitats, the number of species and families in low coverage samples was larger than that in high coverage samples, and furthermore the identities of species were different between them. Species richness significantly decreased with increasing herbaceous vine coverage, illustrating that some species disappeared. Herbaceous vines reduced species diversity of communities, and as a result, community complexity was decreased, which might also decrease community stability. Biomass of communities of self-supporting species significantly decreased with increasing herbaceous vine coverage, which suggested that herbaceous vines significantly decreased community productivity. The number of seedlings also significantly decreased with increasing herbaceous vine coverage, and seedlings were mainly distributed in lower coverage samples. Herbaceous vines reduced the light exposure in the understory, which may be the mechanistic explanation for the negative influence of vines on the performance of tree seedlings. It was concluded that herbaceous vines affected seedling quantitative dynamics and distribution, and inhibited the natural succession from shrub and herb communities to tree communities. Thus herbaceous vines not only had significant influences on community characteristics in pioneer succession stages, but also on subsequent succession stages.     

An empirical approach to the analysis of forest stratification

Natural forest communities consist of different overlapping elementary subpopulations. Using the results of forest stratification in the preceding study, the properties of mean tree height for subpopulation in a stratified forest stand were examined. Mean tree height decreased as tree density per subpopulation increased. This relation was described by a simple mathematical model consisting of a power equation of tree density and two coefficients. The first coefficient or exponent of tree density was close to −1/2 in its expectation, while the other coefficient depended on life forms, especially in tropical forests. For tropical deciduous forests which suffered from seasonal forest fires, the latter coefficient was smaller than those for tropical evergreen and Japanese forests. This difference of the coefficient was not clear between tropical evergreen and Japanese forests and between deciduous and evergreen forests in Japan. In conclusion, the proposed model is similar to the 1/2 power law of tree height in man-made forests with simple architecture, and is designated the quasi-1/2 power law of tree height.     

The role of protective understorey in the regeneration system of a heavily browsed woodland

The paper tests an apparent relationship between young understorey of Ilex aquifolium and the presence of seedlings of the canopy species Fagus sylvatica and Quercus species, in heavily browsed woodland in the New Forest, southern England. A small block of woodland was searched and mapped, and the information collected subject to graphical and statistical analyses.Regeneration, though of low frequency, is present and shows non-random patterns of distribution. Older seedlings appear to be located in or near areas of understorey, or near fallen branches, logs, etc. Principal components analysis of woodland characteristics suggests six main habitat types are available to seedlings, and predictions are made about likely regeneration patterns associated with these habitats, according to a model based on the hypothesis of a protective understorey and heavy browsing pressure. Chi-square tests of actual seedling occurrences versus habitat types demonstrate marked associations of regeneration with non-trampled areas, including young Ilex understorey but also other forms of protective barrier. The association is more marked for larger seedlings.The implications for a wider understanding of regeneration processes and community dynamics in heavily browsed forest are discussed. It is concluded that regeneration theories appropriate to such forests are required, since the dominant gap-phase theories are not successful in predicting regeneration patterns when browsing is a major factor.     

Communities of ground-living spiders in deciduous forests: Does tree species diversity matter?

The relationships between species diversity and ecosystem functions are in the focus of recent ecological research. However, until now the influence of species diversity on ecosystem processes such as decomposition or mineral cycling is not well understood. In deciduous forests, spiders are an integral part of the forest floor food web. In the present study, patterns of spider diversity and community structure are related to diversity of deciduous forest stands in the Hainich National Park (Thuringia). In 2005, pitfall trapping and quantitative forest floor sampling were conducted in nine plots of forest stands with one (Diversity Level 1), three (DL 2) and five (DL 3) major deciduous tree species. Species richness, measured with both methods, as well as spider abundance in forest floor samples were highest in stands with medium diversity (DL 2) and lowest in pure beech stands (DL 1). The Shannon-Wiener index and spider numbers in pitfall traps decreased from DL 1 to DL 3, while the Shannon-Wiener index in forest floor samples increased in the opposite direction. Spider community composition differed more strongly between single plots than between diversity levels. Altogether, no general relationship between increasing tree species diversity and patterns of diversity and abundance in spider communities was found. It appears that there is a strong influence of single tree species dominating a forest stand and modifying structural habitat characteristics such as litter depth and herb cover which are important for ground-living spiders.     

Litter-dwelling ants as bioindicators to gauge the sustainability of small arboreal monocultures embedded in the Amazonian rainforest

One of the greatest threats to biodiversity and the sustainable functioning of ecosystems is the clearing of forests for agriculture. Because litter-dwelling ants are very good bioindicators of man-made disturbance, we used them to compare monospecific plantations of acacia trees, cocoa trees, rubber trees and pine trees with the surrounding Neotropical rainforest (in contrast to previous studies on forest fragments embedded in industrial monocultures). Although the global level of species turnover was weak, species richness decreased along a gradient from the forest (including a treefall gap) to the tree plantations among which the highest number of species was noted for the cocoa trees, which are known to be a good compromise between agriculture and conservation. Species composition was significantly different between natural habitats and the plantations that, in turn, were different from each other. Compared to the forest, alterations in the ant communities were (1) highest for the acacia and rubber trees, (2) intermediate for the cocoa trees, and, (3) surprisingly, far lower for the pine trees, likely due to very abundant litter. Functional traits only separated the rubber tree plantation from the other habitats due to the higher presence of exotic and leaf-cutting ants. This study shows that small monospecific stands are likely sustainable when embedded in the rainforest and that environmentally-friendly strategies can be planned accordingly.     

Long-lived light-demanding emergents in southern temperate forests: the case of Weinmannia trichosperma (Cunoniaceae) in Chile

The prevailing paradigm of tree life histories emphasises strong interrelationships between growth, longevity and reproductive traits, attributing contrasting suites of correlated traits to pioneer and climax or non-pioneer species. In tropical and southern temperate rainforests, although many of the species that require large gaps for regeneration conform to the expectations of small size and short lifespan, a number of others are long-lived canopy or emergent trees. Age data reported here for Weinmannia trichosperma, a shade-intolerant emergent tree in the temperate rainforests of southern Chile, indicate a maximum lifespan (>730 yr) exceeding those previously reported for any other angiosperm of the region. The long lifespan of W. trichosperma is associated with relatively slow growth, reflecting investment of resources in dense wood and possibly other defensive traits. Growth rates of W. trichosperma are much slower than those of associated short-lived pioneer trees, and apparently also slower than some of its more shade-tolerant associates. The light-demanding nature of many of the longest-lived trees in southern temperate forests highlights an important limitation of the classical pioneer-climax paradigm as a framework for understanding tree life history variation and modelling forest dynamics in this biome.A longevity advantage over Nothofagus spp. may help explain the relative abundance of W. trichosperma in the lower to mid-elevation coast range forests in the Chilean lakes district, where the scarcity or absence of Nothofagus in many stands has been attributed to a low frequency of coarse-scale disturbance.p>     

Tree diversity in sacred groves of the Jaintia hills in Meghalaya, northeast India

Biodiversity of woody species was investigated in Ialong and Raliangsacred groves of the Jaintia hills in Meghalaya, northeast India. These grovesrepresent the climax subtropical broad-leaved forest of the area. A total of 738individuals belonging to 82 species, 59 genera and 39 families was identified ina 0.5 ha plot of the Ialong sacred grove, whereas the same area in theRaliang sacred grove had 469 individuals of 80 species, 62 genera and 41families. About 32% species were common to both groves. Lauraceae, with10–17 species, was the dominant family. The canopy and subcanopy stratawere respectively composed of 28 and 33% of the total tree species in theforest. The number of species as well as stem density were greater for the treesof lower dbh (5–15 cm) class compared to the higher (> 66cm) dbh class. The majority of the species showed a contagiousdistribution pattern and low frequency. The basal area varied from 57.4 to 71.4m² ha^–1. Species richness within theforest varied from 3 to 15 per 100 m² in Ialong and 3 to 12 per 100m² in Raliang. The dominance–distribution curves showed highequitability and low dominance in both groves.     

Influence of resource abundance on the structure of the insect community attracted to fermented tree sap

There has been little or no documentation of the insect community attracted to fermented tree sap, despite our familiarity with it. This study describes the influence of resource abundance (exudate quantity) on species richness, insect abundance, and diversity at the patch level in order to elucidate the mechanisms responsible for community structure. Resource abundance was positively correlated with species richness and insect abundance, negatively correlated with the equitability index (J), and not significantly correlated with diversity (Simpsons index of diversity; 1/D). Both correlation analyses and canonical correspondence analysis based on taxonomic categories indicated that responses to resource abundance were much greater in parasitoid wasps (Ichneumonoidea), drosophilid flies (Drosophilidae), and rove beetles (Staphylinidae). Field experiments showed that patches with more of the resource had greater species richness and greater hornet abundance. These results indicate that resource abundance is an important factor that affects community structure at the patch level, although it does not influence diversity directly, due to differences in the response to a resource across subgroups; drosophilid flies, the most abundant group that was heavily dependent on tree sap, make an especially large contribution to the change in J. Various factors influence the variation in the response to resource abundance, including population size, feeding habits, and resource utilization patterns (i.e. whether the species uses patches as habitat).     

Radial growth response of Pinus sylvestris L. and Fagus sylvatica L. to technological solutions applied in rope climbing parks

Vitality is a genetic preservation factor that keeps a tree in the right condition. Changes in tree vitality are a measure of the impact exerted on trees by environmental factors, such as injuries to trunks and branches, and are among the basic parameters of the state of their preservation. The dynamics of changes in the width of annual increments of trees is one of several parameters characterizing the level of their vitality. The aim of the study is to determine changes in radial increment and linking them to the level of the vitality of Scots pines (Pinus sylvestris L.) and European beeches (Fagus sylvatica L.), on which the standard (old system) and specially designed (new system) systems of fastening of wooden platforms were installed as part of adventure park infrastructure. In the old system, the platforms were installed on square wooden beams placed in milled tree trunks, while in the new system on semi-circular metal brackets matching the curvature of the trunks. The present research is aimed to determine the dynamics of incremental trends in trees with different platform systems in relation to the reference group, and to determine the impact of the tested support systems on trees with different levels of vitality. Most of the studied trees were in the optimum stage of increment. The initial tree vitality level recorded at the beginning of the experiment was clearly better for the beech stands. In the case of Scots pine, the average vitality was close to stable. Pines that were initially in better condition responded much worse to the installation of old system platforms compared to those with the specially new platform system. A similar trend was also visible in the case of beeches, but the differences were not that clear and the annual increments of the trees with platforms installed were slightly higher compared to the reference trees. The trees that were initially in worse condition, both pines and beeches on which the old system of platforms had been installed, responded by increasing the width of annual increments during the measurement period. The described response of trees most probably does not result from the lower harmfulness of the old support system, but from the defensive responses of trees subjected to stronger stress.     

Growth response of Sabina tibetica to climate factors along an elevation gradient in south Tibet

We examine the climate significance in tree-ring chronologies retrieved from Sabina tibetica Kom. (Tibetan juniper) at two sites ranging in elevation from 4124 to 4693 m above sea level (a.s.l.) in the Namling region, south Tibet. The study region is under the control of semi-arid plateau temperate climate. The samples were grouped into high- and low-elevation classes and standard ring-width chronologies for both classes were developed. Statistical analysis revealed a decreasing growth rate yet increasing chronology reliability with increasing elevation. Overall, correlation analyses showed that radial growth in S. tibetica at the study sites was controlled by similar climatic factors, regardless of elevation; these factors comprised early winter (November) and early summer (May–June) temperatures as well as annual precipitation (July–June). Slight differences in the correlation between tree growth along the elevation gradient and climate variables were examined. The correlations with early winter temperature varied from significantly positive at the low-elevation site to weakly positive at the high-elevation site, whereas the correlations between radial growth and early summer temperature increased from weakly negative at the low-elevation sites to strongly negative at the high-elevation sites. The abundant precipitation through the year may have masked variations in tree growth on different elevation aspects. Our results will aid future dendroclimatological studies of Namling tree rings in south Tibet and demonstrate the potential of S. tibetica Kom. for improving our understanding of environmental impacts on tree growth.     

Growth decline of Pinus Massoniana in response to warming induced drought and increasing intrinsic water use efficiency in humid subtropical China

Pinus Massoniana is the most widely distributed coniferous species in southern China and one of the most distributed species for plantation in China. It is not uncertain about the responses of tree growth to the combined effects of regional drying and the increase in the intrinsic water-use efficiency (iWUE) due to increased atmospheric CO₂. This study addressed this issue by comparing the tree growth patterns as represented by three tree-ring width chronologies with climate variables and three iWUE series derived from three tree-ring stable carbon isotope discrimination chronologies (Δ¹³C) from Pinus Massoniana in Daiyun Mountain, central Fujian province of China. Among these chronologies, we reported the first tree-ring carbon isotope discrimination chronologies (Δ¹³C) from Fuzhou area spanning last 210 years. It was found that tree radial growth is mainly limited by dry condition from May to October. Growth limitation by cold condition was only found in one high altitude site (780m) in early spring and late autumn. The tree-ring carbon discrimination was enhanced under conditions with low relative humidity and sufficient sunshine in late summer and autumn. In general, the iWUE showed a significantly increasing trend since the 1850s for all the sites in response to the increase in atmospheric CO₂. However, the growth promotion of the increased iWUE on tree growth could not compensate the growth limitation caused by drought. Especially since the 1960s, a growth decline was found at two drought stressed sites at low altitudes. On the other hand, the increase in temperature of spring and autumn and iWUE has most likely enhanced tree growth at the high altitude site.     

Applied dendroecology informs the sustainable management of Blue Pine forests in Bhutan

Tree ring science is a new discipline in Bhutan but has contributed substantially to our understanding of climate history and informed sustainable forest management practices in the country. This paper describes dendroecological contributions to the second aspect for Blue Pine using three case studies. i) The effects of livestock grazing impact on Blue Pine radial growth were quantified. Radial growth increment was tendentially higher after three years of livestock exclosure, as compared to continued grazing. However, differences remained statistically not significant, likely due to the brevity of the treatment period. ii) Radial growth rates of Blue Pine were characterized across a 400 m elevation gradient. Cumulative radial growth over 40 years differed by a factor of more than three between the low and the high end of the gradient. However, below 2300 m, radial growth showed a continuous decline from 1990, likely as a results of drought due to climate change. iii) Effects of three levels of prescribed thinning of pole stage (DBH 30–50 cm) Blue Pine in central Bhutan showed distinct response to thinning. Heavy thinning lead to a thinning shock in the year after harvest and did not lead to significantly higher radial growth as compared to moderate thinning, which is thus recommended for the species. A positive thinning effect remained for seven years post operation. The case studies were incorporated into national guidelines on sustainable forest management in Bhutan and prove the demand for tree ring based research to inform policy and practice.     

Correlation between trunk and branch age in trees as a new parameter in the analysis of tree architecture

A method for characterizing tree form is developed by linear regression of the age of the trunk on the average branch age at different heights. This relationship holds for a wide variety of situations, including both theoretical models and observed tree samples. The intercept of the regression, a, the ‘index of trunk distinctness’, reflects the branching pattern inherent to the species and indicates whether the trunk is erect or not. The slope, b, is termed the ‘crown thickness coefficient’, because it indicates a branching pattern. Tree forms can be classified into nine theoretical groups; three of these are physically impossible. The method was applied to real trees and a and b are shown to be useful tree form characteristics. Possible applications of the method are briefly discussed.     

Tree species richness complementarity, disturbance and fragmentation in a Mexican tropical montane cloud forest

Tropical montane cloud forest exhibits great heterogeneity in speciescomposition and structure over short geographic distances. In central Veracruz,Mexico, the conservation priority of seven cloud forest fragments was assessedby considering differences in woody plant species richness and complementarityof species among sites, forest structure, tree mortality, and timber andfirewood extraction as indicators of anthropogenic disturbance. Densities oftrees 5 cm dbh (360–1700 trees/ha) weredifferent among the sites, but basal area (35.3–89.3m²/ha) did not differ among fragments. The number of dead trees rangedfrom 10–30 to 170–200 trees/ha. The fragments'species composition was different but complementary. The Morisita–Hornindex indicated low similarity between fragments. A non-parametric estimator ofspecies richness indicated that more sampling effort would be necessary tocomplete the inventory (15 additional trees and two understory shrub species).Unfortunately, most of the fragments are threatened with deforestation. The numberof cut trees was similar among sites (0–15 cut trees/0.1 ha).Sites with immediate need for conservation were close to settlements, with highnumbers of cut trees and no legal protection. The selected sites represent thevariety of situations that exist in the region. Given the high complementarityobserved between fragments, a regional conservation approach will be required topreserve the last repositories of part of the tremendous biodiversity of theonce continuous forest in this region.     

Changing relationships between tree growth and climate in Northwest China

Recently, several studies have shown changing relationships between tree growth and climate factors, mostly in the circumpolar north. There, changing relationships with climate seem to be linked to emergent subpopulation behavior. Here, we test for these phenomena in Northwest China using three tree species (Pinus tabulaeformis, Picea crassifolia, and Sabina przewalskii) that had been collected from six sites at Qilian Mts. and Helan Mts. in Northwest China. We first checked for growth divergence of individual sites and then investigated the relationship between tree growth and climate factors using moving correlation functions (CF). Two species, Pinus and Sabina, from two sites clearly showed growth divergence, not only in the late twentieth century as reported in other studies, but also over nearly the whole record. In divergent sites, one chronology shows more stable relationships with climate factors (usually precipitation). In non-divergent sites, nearly all relationships either vary in strength or become non-significant at one point. While this might possibly be related to increased stress on some trees due to increasing temperature, the exact causes for this shift in sensitivity remain unclear. We would like to highlight the necessity for additional studies investigating possible non-stationary growth responses of trees with climate, especially at sites that are used for climate reconstruction as our sites in Northwest China.     

On an outbreak of the citrus flat-headed borer,Agrilus auriventris E. Saunders in Nagasaki Prefecture

The process of an outbreak of the citrus flat-headed borer, Agrilus auriventris in Nagasaki Prefecture was described with some ecological considerations on causative factors. This outbreak which showed a typical “Gradation”, initiated around 1958, and terminated in 1963. The peak year was seen in 1961. At first attack by the borer was restricted to old and weak trees, but it was also found in young and healthy trees in the peak year. Some environmental conditions in orchards were examined in relation to the intensity of infestation by the borer. Soil management and drought seemed to have remarkable correlations with the borer's infestations. Probably, this outbreak was caused by the weakening of citrus tree by gummosis and abnormal defoliation, aging of orchard trees, and drought in the summer of 1959∼1960. Interrelation between these causes and processes are shown schematically in Fig. 12.     

An organismal view of dendrochronology

An organism is the most basic unit of independent life. The tree-ring record is defined by organismal processes. Dendrochronology contributes to investigations far removed from organismal biology, e.g., archeology, climatology, disturbance ecology, etc. The increasing integration of dendrochronology into a diverse research community suggests an opportunity for a brief review of the organismal basis of tree rings.Trees are dynamic, competitive, and opportunistic organisms with diverse strategies for survival. As with all green plants, trees capture the energy in sunlight to make and break chemical bonds with the elements essential for life. These essential elements are taken from the atmosphere, water, and soil. The long tree-ring series of special interest to dendrochronology result from long-lived trees containing relatively little decayed wood. Both of those features result from organismal biology. While the tree-ring record tells us many things about local, regional, and even global environmental history, tree rings are first a record of tree survival.     

Succession of sessile organisms on experimental plates immersed in Nabeta Bay,Izu Peninsula,Japan IV. Temporal changes in metabolism,biomass and maturity of community

Community succession in the metabolism, biomass and maturity of sessile organisms on concrete plates immersed at depths of 1.0, 2.5, 4.0 and 5.5 m in Nabeta Bay, Shimoda, pacific coast of Japan, was investigated over a period of about 3 yr. Gross primary production of the community (Pg) and community respiration (R) showed maxima at 10 and 13 months after immersion, and then Pg decreased significantly at all depths, whereas R was reduced only at the lower two depths. A parameter of community biomass, chlorophylla (Chl.a), showed a similar successional change to Pg. Five other parameters, i.e. dry mass (DM), ash dry mass (ADM), ash-free dry mass (AFDM), organic carbon (C) and organic nitrogen (N) increased significantly throughout succession, at least at the uppermost depth, but decreased significantly in the period 13–37 months after immersion at the lowest depth. Successional changes in five indices reflecting community maturity, i.e. the ratios of estimated daily gross primary production/estimated daily respiration (Pg/R), gross primary production/organic carbon (Pg/C), gross primary production/chlorophylla (Pg/Chl.a), organic carbon/organic nitrogen (C/N) and Margalef's pigment diversity (D430/D665), also differed among the depths, especially at 37 months after immersion. Succession at the upper two depths appeared to progress toward a mature state, as opposed to retrogression to an immature state at the lower two depths. This difference in successional changes in these 13 parameters between depths agrees with the prediction of Margalef (1968) and Odum (1969), despite the tendency for Pg/R to be more heterotrophic in an open system. Contributions from the Shimoda Marine Research Center, No. 515.     

Mandibular movement patterns relative to food types in common tree shrews (Tupaia glis)

Although common tree shrews have long been considered a model system for early eutherian mastication, little information on mandibular movement patterns relative to specific food types has been reported. Detailed analysis of mandibular movement patterns when related to resulting attrition facets may permit more accurate extrapolations regarding the dietary habits of primitive mammals. Marker beads were sewn to chins of five animals that were placed in a restraint system and filmed while they fully masticated mealworm larvae and standardized pieces of banana, almond, and commercial cat chow. These sequences were divided into early, middle, and late thirds of food reduction. Mandibular positions from both frontal and lateral perspectives were digitized frame by frame to yield plots of orbits in three dimensions as well as graphic display of displacements, velocities, and accelerations. Plot coordinates were averaged to generate composite orbital shapes. Significant (p < 0.01) findings included: (1) shortest orbital durations and greatest peak closing velocities and accelerations in early third of reduction; (2) smallest maximum gape, smallest maximum lateral excursion from midline, and longest duration of powerstroke relative to orbital duration in late third of reduction; (3) shortest orbital durations and smallest maximum gape during mastication of chow; (4) greatest maximum lateral excursion during mastication of mealworm larvae; and (5) smallest peak closing accelerations during mastication of banana. Significant differences were also found among subjects for all parameters examined. Capacity for complex jaw movement may have been critical for allowing primitive molars to be used for trituration of a variety of food types, and may have preceded evolution of more specialized molar forms.