Changes in human jaw muscles with age and dental state

The effects of ageing and dental state on the cross-sectional area and density of two jaw muscles, the masseter and medial pterygoid, were investigated using computed tomography. The study involved 84 male and 70 female subjects between the ages of 20 and 90 years. The cross-sectional area of both muscles showed a significant reduction with age; values for female subjects being found in the lower range of the distribution. When consideration was given to the presence or absence of a natural dentition, the cross-sectional area of both muscles in edentulous subjects showed a greater decease throughout the age range studied. There was a significant decrease in the density of the muscles with increasing age. Previously, this has been interpreted to indicate a progressive increase in fat and fibrous tissue. Subject gender and the absence of teeth appeared to have little effect on this parameter. Changes in the cross-sectional area and density of these muscles would appear to be consistent with a general age related change of muscle tissue in the body as a whole and may specifically indicate a reduction in the masticatory forces which can be or are being utilised by ageing patients, many of whom have no remaining natural dentition.     

Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga

Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.     

Growth and nutrition of birch seedlings in relation to potassium supply rate

Summary Growth of hydroponically cultivated birch seedlings (Betula pendula Roth.) at sub- and supra-optimum potassium supply rates was investigated. Potassium was supplied either as a relative addition rate (r _k = 5, 10, 15 and 20% increase day^-1) or as fixed concentrations (0.2, 3, 6, 12 and 15 mM) in the culture solution. After an acclimation period the growth rate of the seedlings in the suboptimum treatments reached values close to the treatment variable, the relative rate of K-addition. Deficiency symptoms, in the form of chlorosis and necroses along the leaf margins, developed initially in all suboptimum treatments, but very few new symptoms appeared once the seedlings had reached the phase of steady-state nutrition and growth. At supra-optimum K-supply levels, i.e. at 0.2–15 mM K in the culture solution, no symptoms of deficiency or toxicity developed, and the relative growth rate of the seedlings remained maximum. The relative growth rate of the seedlings was linearly related to the plant K-status for K contents ranging from 0.2 to 1.0% of dry weight (DW). At higher internal K-concentrations, 1.0–3.0% DW, no further increase in relative growth rate was achieved. A shortage of K resulted in a decrease in the net assimilation rate. This effect was counterbalanced by the absence of shift in he leaf weight ratio as well as by the production of relatively thin leaves. The fraction of dry matter allocated to roots decreased in K-limited plants, as did the leaf contents of soluble carbohydrates and starch.     

燕山地区白头翁生境伴生植物资源调查与分析

调查与白头翁共存的伴生植物种类、相似性、生活型、分布区类型等,探讨其生态适应性和地理分布规律,针对性地提出白头翁资源保护利用建议,以期为燕山地区白头翁种质资源的保护和利用提供参考。采用访问调查、路线调查和典型样地调查法,对燕山地区白头翁生境伴生植物进行调查与分析。燕山地区从冀东的秦皇岛地区到冀北的承德地区都有白头翁的分布,多生于向阳的山地草坡上,喜光、耐旱、适于阳生性环境。白头翁生境伴生植物共56科128属164种,主要优势科为菊科（Compositae）、豆科（Leguminosae）、禾本科（Gramineae）、蔷薇科（Rosaceae）、唇形科（Labiatae）、百合科（Liliaceae）、毛茛科（Ranunculaceae）、萝藦科（Asclepiadaceae）等,其中乔木共5科5属7种,灌木共22科38属46种,草本植物共35科85属111种。调查的各样地间相似系数普遍较低,说明燕山地区不同地区白头翁生境差别较大,其伴生植物具有多样性的特点。伴生植物属的分布区类型可分为14个,群落具有明显温带性质。燕山地区白头翁生境多样性及伴生植物的多样性,反映出燕山地区白头翁生态适应多样性特点,有利于其引种栽培。     

Forecasting the future suitable growth areas and constructing ecological corridors for the vulnerable species Ephedra sinica in China

Ephedra sinica is a rare and vulnerable species in China, and the habitat of Ephedra sinica is seriously threatened (by climate change and human activities). Predicting the suitable growth areas and constructing ecological corridors for Ephedra sinica in China will help to protect it scientifically. Based on 306 valid distribution records and 13 selected environmental factors, the maximum entropy (MaxEnt) model was used to simulate the potential current habitat zones and future (2050 and 2070) habitat zones of Ephedra sinica under four climate change scenarios. The minimum cumulative resistance (MCR) model was applied to extract important ecological corridors of Ephedra sinica. The results indicate that: (1) Under the current environment, the total area of the suitable habitat for Ephedra sinica in China is 42.24 × 10⁵ km², mainly distributed in Northwest China and North China. (2) Suitable area increases as the RCP rises. The center of mass of the habitat zone moved northward from Shaanxi Province to Ordos City in Inner Mongolia Autonomous Region. (3) Of the 13 environmental factors selected, the primary factor was elevation (20.8 %), followed by wettest month precipitation (18.2 %) and temperature seasonality (15.2 %). (4) Built 19 ecological corridors, with a total corridor length of 430.2 km, including seven long-distance passages and 12 short-distance corridors. All corridors are far from the artificial surface, mostly near high-altitude areas. The 19 ecological corridors constructed using the MCR model will also provide considerable importance for the survival of Ephedra sinica on a longer time scale in the future.     

Two-phase species–time relationships in North American land birds

The species–time relationship (STR) is a macroecological pattern describing the increase in the observed species richness with the length of time censused. Understanding STRs is important for understanding the ecological processes underlying temporal turnover and species richness. However, accurate characterization of the STR has been hampered by the influence of sampling. I analysed STRs for 521 breeding bird survey communities. I used a model of sampling effects to demonstrate that the increase in richness was not due exclusively to sampling. I estimated the time scale at which ecological processes became dominant over sampling effects using a two‐phase model combining a sampling phase and either a power function or logarithmic ecological phase. These two‐phase models performed significantly better than sampling alone and better than simple power and logarithmic functions. Most community dynamics were dominated by ecological processes over scales <5 years. This technique provides an example of a rigorous, quantitative approach to separating sampling from ecological processes.     

North Sea cod and climate change – modelling the effects of temperature on population dynamics

In order to examine the likely impacts of climate change on fish stocks, it is necessary to couple the output from large‐scale climate models to fisheries population simulations. Using projections of future North Sea surface temperatures for the period 2000–2050 from the Hadley General Circulation Model, we estimate the likely effects of climate change on the North Sea cod population. Output from the model suggests that increasing temperatures will lead to an increased rate of decline in the North Sea cod population compared with simulations that ignore environmental change. Although the simulation developed here is relatively simplistic, we demonstrate that inclusion of environmental factors in population models can markedly alter one's perception of how the population will behave. The development of simulations incorporating environment effects will become increasingly important as the impacts of climate change on the marine ecosystem become more pronounced.     

Root/Shoot Allocation and Root Architecture in Seedlings: Variation among Forest Sites, Microhabitats, and Ecological Groups1

I analyzed patterns of variation in root mass allocation and root morphology among seedlings of woody species in relation to environmental factors in four Neotropical forests. Among forests, I explored the response of root traits to sites varying in water or nutrient availability. Within each forest, I explored the plastic response of species to different microhabitats: gaps and understory. Additionally, I explored evidence for life history correlation of root and shoot traits by comparing species differing in their successional group (light‐demanding [22 spp.] or shade tolerant [27 spp.]) and germination type (species with photosynthetic cotyledons or species with reserve cotyledons). At each forest site, young seedlings from 10 to 20 species were excavated. A total of 55 species was collected in understory conditions and 31 of them were also collected in gaps. From each seedling, six morphological ratios were determined. Allocation to roots was higher in forest sites with the lowest soil resources. Roots were finer and longer in the most infertile site, while roots were deeper in the site with the longest dry season. Seedling traits did not differ between germination types. Shade tolerant species allocated more to roots and developed thicker roots than light‐demanding species. Light‐demanding species showed stronger plastic responses to habitat than shade tolerant species, and species with photo‐synthetic cotyledons showed lower plasticity than species with reserve cotyledons. Overall, these results suggest that among Neotropical species, root allocation and root morphology of seedlings reflect plant adjustments to water or nutrient availability at geographic and microhabitat scales. In addition, life history specialization to light environments is suggested by differences among groups of species in their allocation to roots and in their root morphology.     

广西龙虎山猕猴种群生态特征

１９８８～１９９５年,采用定点观察法和绝对计数与相对计数结合法对龙虎山猕猴种群生态作了调查研究。１９９０年核心区有猕猴１４群,５００只左右,猴群密度１．６群／ｋｍ２,种群密度５５．６只／ｋｍ２．猴群大小平均３３．８±２３．１（ｎ＝６）只。一般每隔４～５年分群一次,猴群群体年均增长率１４．８％,种群年均增长率为９．７％。猴群中成年猴性比为７．６±６．５（ｎ＝１２）,１～３岁组的性比为０．７４±０．６１（ｎ＝４）,群内未成年猴比例为６７．７±３．１％（ｎ＝１２）。发情交配期最早１１月１２日,最晚次年１月２０日,高峰期１２月上旬,持续３个月．产仔期最早４月１日,最晚８月１４日,高峰期５月上旬,持续时间４个半月．繁殖率４５．５％～１００％,平均７５．４±１３．２％（ｎ＝２１）。新生猴死亡率较低,新生猴性比（雌：雄）平均０．７４±０．３４（ｎ＝５）。     

DISCOVERY OF VERTEBRATE FOSSILS AND PALEOLITHIC ARTIFACTS IN DANJIANG SUBMERGING AREA AND ITS IMPLICATIONS

IntheareatobefloodedinthesecondengineeringstagefortheDanjiangreservoir,wediscovered16vertebratefossillocalitiesand52Paleolithicsitesin1994,andcollected603artifactsandmanyfossils.Ofthel6new1yfoundvertebratefossillocalities,threearereptilesitesrepresentedbydinosaureggsandlimbbones,andl3producemamma1s,including4Pale0gene,2Ne0geneand7Quaternarysites'ThemammalianlocalitiesareofPale0cene,Eocene,EarlyMiocene,andPli0ceneorEarlyPleistocene,MiddleandIntePleistocene,respectively.Theyfillinsomestrat…