Age-class Structure Research Articles

Timber Harvest Planning Using Reinforcement Learning: A Feasibility Study

This study developed a forest management plan model using reinforcement learning (Q-learning) to optimize both the economic and ecological functions of forests. Management objectives for national forests were established, and forest conditions were analyzed using GIS spatial data and administrative records. A 60-year forest management plan was formulated to predict timber production and management performance across different regions and time periods. Our analysis revealed that Scenario 3 (Carbon Storage Priority) demonstrated the highest economic value, starting at approximately KRW 576.2 billion in the initial period and escalating to KRW 775.7 billion over six 10-year periods, totaling 60 years. In addition to its economic performance, Scenario 3 effectively improved forest age class structure and ensured a stable timber supply, making it the most balanced approach for sustainable forest management. By focusing on carbon storage as a key management goal, this approach highlights the potential for achieving both economic and environmental benefits concurrently. These results suggest that reinforcement learning is a powerful tool for developing long-term forest management strategies that address multiple objectives, including economic viability, ecological sustainability, and resource optimization.

Population Structures and Dynamics of Rhododendron Communities with Different Stages of Succession in Northwest Guizhou, China.

To explore the population structures and dynamics of Rhododendron shrub communities at different stages of succession in northwest Guizhou, China, this study examined the populations of Rhododendron annae and Rhododendron irroratum shrub with two different stages. A space-for-time substitution was employed to establish the diameter class/height structures, static life tables, and survival/mortality rate/disappearance rate curves of both Rhododendron populations with different orders of succession. Their structural and quantitative dynamics were analyzed, and their development trends were predicted. The results showed that, quantitatively, the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession were dominated by age classes one, two, and three as well as height classes i, ii, and iii. The number of Rhododendron plants at the three age classes and the three height classes accounted for 97.61-100% of the total. The quantitative dynamic indices of R. annae and R. irroratum were both greater than 0, with and without considering external interference. In terms of age class and height structures, both Rhododendron populations were expanding populations, presenting "inverted-J-shaped" and irregular pyramid patterns. There was a sufficient number of young individuals, but few or no old individuals. Both survival curves of the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession belonged to the Deevy-II type. In the late stage of succession, the mortality curves and disappearance curves of both Rhododendron populations in these communities presented a trend of increasing first and then decreasing with increasing age class. This result indicates that at each age class, R. annae and R. irroratum showed a trend of gradual increase after two, four, and six years. In brief, the populations of R. annae and R. irroratum have rich reserves of seedlings and saplings, but high mortality and disappearance rates. In this context, it is necessary to reduce human interference and implement targeted conservation measures to promote the natural renewal of Rhododendron populations.

What Causes Differences in the Age-Class Structure between Suburban and Forest Populations of Anolis homolechis?

Although growing urbanization has direct negative consequences for local biodiversity, several native species have been observed maintaining populations in urban environments. Understanding which factors influence the ability of native species to persist in urban environments is crucial, both for the study of biological adaptation and of urban planning. The quantification of the proportion of juvenile individuals can be a good proxy for assessing the long-term persistence of urban populations. We present comparative data about spatial and temporal variations in the age-class structure in two suburban and two forest populations of the Cuban endemic lizard Anolis homolechis, obtained during a 20-month survey. We found a four-fold lower proportion of juveniles in the suburban habitat compared to the forest one. There was, however, no evidence for differential female fecundity between the two habitats, as assessed by the proportion of gravid females. Conversely, the rate of tail autotomy (an antipredator behavior) was significantly higher in the suburban juveniles compared to the forest ones, possibly reflecting a higher exposure to predators and, particularly, inter- and intraspecific cannibalism. However, tail loss at initial capture or habitat type had no effect on the probability of recapture of juveniles. We discuss the potential causes and consequences of a modified age-class structure in urbanized environments.

Efficiency of enhanced capture methods and age-class structure of dispersing boreal woodpeckers

Efficiency of enhanced capture methods and age-class structure of dispersing boreal woodpeckers

Feasibility and application of using Texas horned lizard scat to predict lizard size and age class

AbstractTexas horned lizards (Phrynosoma cornutum; hereafter THL) were once abundant throughout Texas; however, their distribution and abundance have decreased, and currently they are listed as a threatened species in the state. Detection of THL can be difficult because of their cryptic nature and sporadic distribution. Using indirect signs such as fecal pellets (i.e., scat) to determine occupancy is a widely practiced survey technique. However, it is unknown if scat size can be used to determine the age structure of THL. Our objectives were to determine 1) if THL scats were consistently produced and at consistent size in relation to lizard snout‐vent length (SVL), 2) if THL scats remain intact in the environment, and 3) if scat length and diameter could be used as an indicator of THL size, which could be used to determine population age structure. We tested the feasibility of using scat morphometrics to estimate age class ratios, body size, and population estimates for THL. Data collection was conducted in 3 phases, which occurred from 2001–2019. Scats were collected daily for 6 days from 6 hatchling, 10 juvenile, and 10 adult THL collected from southern Texas. Texas horned lizards were measured for snout‐to‐vent length (mm) and categorized as either hatchling, juvenile, or adults based on estimates from the literature. On average, THL produced one scat/day, typically in the morning. Scat length and width increased as lizard size (i.e., SVL) increased with each age class. Scat size of each age class of THL was consistent between days; thus, objective one was met. Scats were measured for length and width (mm) and placed in direct sunlight for 90 days, submerged in water for 2 days, and placed in typical summer weather conditions of southern Texas. Texas horned lizard scat did not shrink or swell in size or decay due to environmental conditions during the 90‐day experiment. Thus, THL scats do remain intact in the environment. We collected scat from 70 known‐size THL from south‐central Texas. Simple log‐log regression models demonstrated a linear relationship (r2 = 0.89) between loge (SVL) and loge (scat length, mm). Slopes were similar among age classes, but intercepts differed as expected. We tagged individual THL to follow growth rates through time. Thirteen of 20 tagged females produced 178 hatchlings, of which 56, 23, 19, and 6 were recaptured during their hatchling, 2nd, 3rd, and 4th year, respectively. Models for growth rates of known‐age THL were not equal (F6,69 = 44.6, P < 0.0001) among age classes. Growth rates were faster in year 1 (0.101 ± 0.003 mm d−1) and year 2 (0.099 ± 0.007 mm day−1) and slowed (0.076 ± 0.009 mm day−1) during their 3rd year. Scat from THL reliably can be used to estimate population age class structure, body size, and population estimates. However, our growth rate analyses suggest that THL appear to experience slower growth rates than during previous decades, and thus, THL require reevaluation as to what SVL size constitutes an adult THL.

Aboveground live tree carbon stock and change in forests of conterminous United States: influence of stand age

BackgroundSequestration of carbon on forest land is a common and practical component within many climate action plans developed by state or municipal governments. Initial planning often identifies the general magnitude of sequestration expected given the scope of the project. Because age plays a key role in forest carbon dynamics, we summarize both the carbon stock and accumulation rates in live trees by age class and region, allowing managers and policymakers to assess the influence of forest age class structure on forest carbon storage as represented in current inventories. State-level information is provided in supplementary tables.ResultsAverage regional aboveground live tree carbon stocks (represented on a per area basis) range from 11.6 tC/ha in the Great Plains to 130 tC/ha in the Pacific Northwest West (west-side of Cascades) and increase with age in all regions, although in three regions carbon stock declined in the oldest age class. Regional average annual net change in live aboveground tree carbon varies from a low of − 0.18 tC /ha/yr in the Rocky Mountain South region to a high value of 1.74 tC/ha/yr in Pacific Northwest West. In all regions except Rocky Mountain South, accumulation rates are highest in the younger age classes and decline with age, with older age classes in several western regions showing negative rates. In the Southeast and Pacific Northwest West, intermediate age classes exhibit lower rates, likely due to harvesting activity.ConclusionsAboveground live tree carbon stocks increase and rates of average change decrease with age with few exceptions; this pattern holds when examining hardwood and softwood types individually. Because multiple forest management objectives are often considered and tradeoffs need to be assessed, we recommend considering both measures—standing stock and average annual change—of carbon storage. The relative importance of each component depends on management and policy objectives and the time frame related to those objectives. Harvesting and natural disturbance also affect forest carbon stock and change and may need to be considered if developing projections of potential carbon storage. We present forest carbon summaries at a scale and scope to meet information needs of managers and policymakers.

Vegetation Structure and Regeneration status of Rhododendron arboreum sp. in the forests of Western Himalayas: Study of Van-Panchayat and Reserve forests in Chamoli District of Uttarakhand, India

One of the known indicators of forest health is regeneration of trees, their diversity and the age class structure. Forests which are subjected to unsustainable harvest of its products are in particular vulnerable and stressed. The present study was conducted to study the vegetation structure and regeneration status of Rhododendron arboreum in the van-panchayat and reserve forests of Uttarakhand, Western Himalaya. R.arboreum (Family Ericaceae) is an important keystone species in the region, and any significant change in the species composition due to anthropogenic pressures may also impact the forest community structure. Regeneration status of this species in the study area was enumerated with relative density of seedlings, saplings and mature tree individuals. Regeneration with viable seedling population indicates good forest health and is also a critical part of forest management. Vegetation analysis revealed a total of 13 tree species belonging to 10 families in the forest sites of the study area. Species density (ind/ha) varied from 469-525 (trees), from 322-385 (saplings), and from 435-464 (seedlings) in the van-panchayat forests and 525-572 (trees), 325-350 for (saplings) and 108-275 for seedlings in the reserve forests. Species diversity (H’) value in the van-panchayat forests ranged from 2.04-2.16 (trees), 1.52-1.86 (saplings), 1.32-1.54 (seedling) and from 2.36-2.45 (trees), 2.04-2.18 (saplings), 1.22-1.34 (seedling) in the reserve forest sites.The tree species richness and density in the reserve forests were found to be marginally higher than the van panchayat forests due to low anthropogenic pressure and limitations on the community’s extraction of forest-resources. However, fewer number of individuals of seedlings and saplings indicate less regeneration capacity of Rhododendron sp. in the reserve forest sites, which might be due to reduced seed germination of canopy species or maturation of the forests.

The fate of rescued Manx Shearwaters following grounding

Manx Shearwaters Puffinus puffinus, like other procellariiform seabirds, spend most of their lives at sea and are encountered on land only when breeding at colonies or if they are grounded due to unfavourable weather conditions or exposure to artificial light. Here, we used historical ringing data to explore the age class structure and spatial patterns of Manx Shearwater groundings and examined ringing and recovery data to identify records of post-grounding survival for first-year and adult birds. We noted 35 cases, out of 6,381 ringed grounded shearwaters, where a bird went on to be recaptured, including two individuals that were later recorded as having successful breeding attempts. While this constitutes only a small number of birds confirmed to have survived following grounding, it is likely to be a considerable underestimate of survival considering the low probability of recapturing a surviving shearwater. Finally, we found that a greater proportion of grounded birds were first-years compared to adult shearwaters, and that adults were found to be grounded further away from colonies than first-year birds. This may be indicative of differential impacts of light pollution at different life stages.

Economic and Ecological Impacts of Adjusting the Age-Class Structure in Korean Forests: Application of Constraint on the Period-to-Period Variation in Timber Production for Long-Term Forest Management

South Korea’s successful reforestation efforts over the past 50 years have led to abundant forest resources. However, intensive reforestation during the 1970s and 1980s skewed the forests’ age distribution towards forest stands aged 30 years or older, which results in an unbalanced distribution of age-class, requiring redistribution with harvest and effective regeneration plans to produce a sustained yield of timber as well as long term ecological benefits. During this conversion process, variations in timber production can occur, causing economic and ecological risks if excessive. To prevent these likely risks, permissible levels of increase and decrease in timber production can be restricted in the planning phase. In determining the appropriate variation rate in timber production, it is necessary to understand the impacts of variation in timber production on forest management. This study performed a sensitivity analysis to evaluate the economic and ecological impacts of constraining the period-to-period variation in timber production. A multi-objective linear programming (MOLP) forest management planning model was utilized to study forests in Mt. Gari, South Korea. Nine management alternatives were set with different levels of variation rate in timber production and further constraints. The total volume and net present value (NPV) of timber production, carbon storage, and water storage were analyzed for each alternative. As timber production variation rates decreased, the amount of timber production increased and forest carbon storage decreased; furthermore, NPV diminished as variation constraints strengthened. These differences were mainly caused by selection of regeneration species according to the constraint on variation in timber production. If the variation rate was strictly restricted, the area of timber species with short rotation age increased during conversion period, in order to reduce the gap of timber production between periods. At the latter part of planning horizon, the area of broad-leaved trees was enlarged as the burden of adjusting age-class structure reduced. The appropriate variation rate in timber production was determined to be 30%, based on considerations regarding the economic and ecological impact of the variation on the forest.

Climate-Mediated Recruitment Failure in a Turtle Population and Its Bearing on Northern Limits of Distribution

The eruption of Mount Pinatubo in the Philippines in June 1991 reduced global temperatures over the following 2 yrs. The greatest suppression (apart from Antarctica) was centered in the northern Great Plains of North America, directly over my long-term turtle study site. Temperatures at that site in 1992 and 1993 were the coldest in at least 50 yrs. Normal annual hatchling recruitment of yellow mud turtles (Kinosternon flavescens) in the spring following incubation at that site averaged 375; however, only 3 hatchlings emerged in 1993 (1992 incubation cohort), and none emerged in 1994 (1993 incubation cohort). The depressed temperatures apparently prolonged incubation times to such an extent in 1992 and 1993 that hatching was nearly impossible before winter mortality. The result was a gap in the age class structure that was still evident 26 yrs later. This site is at the northern range limit of this species, and this event suggests that incubation temperatures (i.e., summer season length) may be responsible for that limit.

The effect of seabird presence and seasonality on ground-active spider communities across temperate islands.

Seabirds influence island ecosystems through nutrient additions and physical disturbance. These influences can have opposing effects on an island's invertebrate predator populations. Spiders (order: Araneae) are an important predator in many terrestrial island ecosystems, yet little is known about how seabird presence influences spider communities at the intraisland scale, or how they respond to seasonality in seabird colony attendance.We investigated the effects of seabird presence and seasonality on ground-active spider community structure (activity-density, family-level richness, age class, and sex structure) and composition at the family-level across five short-tailed shearwater breeding islands around south-eastern Tasmania, Australia. Using 75 pitfall traps (15 per island), spiders were collected inside, near, and outside seabird colonies on each island, at five different stages of the short-tailed shearwater breeding cycle over a year. Pitfall traps were deployed for a total of 2674 days, capturing 1592 spiders from 26 families with Linyphiidae and Lycosidae the most common. Spider activity-density was generally greater inside than outside seabird colonies, while family-level richness was generally higher outside seabird colonies. For these islands, seabird breeding stage did not affect activity-densities, but there were some seasonal changes in age class and sex structures with more adult males captured during winter. Our results provide some of the first insights into the spatial and temporal influences seabirds have on spider communities. We also provide some of the first records of spider family occurrences for south-eastern Tasmanian islands, which will provide an important baseline for assessing future change.

Formation of Age Class Structures of the Primary Boreal Spruce Forests in European Russia

Formation of Age Class Structures of the Primary Boreal Spruce Forests in European Russia

A Multidimensional Matrix Model for Predicting the Effects of Male-Biased Sex Ratios on Fish Populations.

Laboratory experiments have established that exposure to certain endocrine-active substances prior to and/or during the period of sexual differentiation can lead to skewed sex ratios in fish. However, the potential long-term population impact of biased sex ratio depends on multiple factors including the life history of the species and whether the ratio is male or female-biased. In the present study, we describe a novel multidimensional, density-dependent matrix model that analyzes age class-structure of both males and females over time, allowing for the quantitative evaluation of the effects of biased sex ratio on population status. This approach can be used in conjunction with field monitoring efforts and/or laboratory testing to link effects on sex ratio due to chemical and/or nonchemical stressors to adverse outcomes in whole organisms and populations. For demonstration purposes, we applied the model to evaluate population trajectories for fathead minnow (Pimephales promelas) exposed to prochloraz, an aromatase inhibitor, during sexual differentiation. The model also was used to explore the population impact in a more realistic exposure scenario in which both adult and early life stages of fish are exposed concurrently to prochloraz, which, in addition to altering sex ratio during development, can decrease vitellogenin and egg production in adult females. For each exposure scenario, the model was used to analyze total population size, numbers of females and of males, and sex specific recruitment of the F1 generation. The present study illustrates the utility of multidimensional matrix population models for ecological risk assessment in terms of integrating effects across a population of an organism even when chemical effects on individuals are manifested via different pathways depending on life stage. Environ Toxicol Chem 2022;41:1066-1077. Published 2022. This article is a U.S. Government work and is in the public domain in the USA.

长白山阔叶红松林紫椴种群结构与动态特征

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山阔叶红松林紫椴种群结构与动态特征 DOI: 10.5846/stxb202106191629 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技基础资源调查项目(2019FY101602) Population structure and dynamic characteristics of Tilia amurensis in broad-leaved Korean pine mixed forest in Changbai Mountain Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:紫椴(Tilia amurensis)为国家二级重点保护野生植物。以长白山北坡阔叶红松林内的紫椴种群为研究对象,通过建立种群静态生命表、绘制存活曲线、计算数量动态指数并引入生存函数和时间序列预测模型定量描绘其结构与动态特征。结果表明:1)种群年龄结构呈不规则金字塔形,幼龄阶段(Ⅰ-Ⅳ龄级)个体数之和占个体总数的67.26%。2)种群存活曲线接近Deevey-Ⅲ型,表明植株在幼龄阶段死亡率高。3)总体数量动态变化指数Vpi>V'pi>0,表明紫椴种群为增长型,但V'pi趋近于0,结合死亡率(qx)和消失率(Kx)曲线呈现出连续性先增后降的复杂动态变化趋势,可知该种群不稳定且在干扰情况下增长趋势不明显。4)生存函数分析显示,种群在Ⅲ-Ⅳ龄级间达到平衡状态,尔后进入衰退期且从第Ⅷ龄级开始进入生理衰退。5)时间序列预测分析表明,在未来2、3、4、5、6、7、8、9、10龄级时间后,紫椴幼龄个体数逐渐减小,而中、成和老龄个体数量将逐渐增加,说明未来紫椴种群的增长主要依靠后者。生物学特性和生境是限制紫椴种群增长的主要原因。建议加强幼苗抚育工作,提高幼苗和小树的存活率,保护和改善生存环境,从而促进紫椴种群的自然更新和恢复。 Abstract:Tilia amurensis is the second-class national protection species. In this study, the population structure and dynamic characteristics of T. amurensis distributed in Changbai Mountain were analyzed by population statistics, including static life table, survival curve, the quantity dynamic index, survival function, and time series prediction model. The results showed that:1) the age-class structure of T. amurensis population was irregular pyramid type, and the sum of number of young individuals (I-IV age class) accounted for 67.26% of the total individuals. 2) The survival cure was close to Deevey-Ⅲ type, which showed that the number of young individuals was abound while their survival rate was low. 3) The population dynamics index was Vpi>V'pi>0, indicating that T. amurensis population belonged to the increasing type. However, the index V'pi closed to 0, and the curve of mortality rate (qx) and vanish rate (Kx) showed a complex dynamic trend of continuous increase first and then decrease, which indicated that the population stability was poor and the growth trend was not obvious in the case of disturbance. 4) The analysis of survival function showed that the population reached a balance between the age classes of Ⅲ-Ⅳ, and then entered the decline period. From the age class of Ⅷ, the population entered a physiological decline phase. 5) Time series prediction analysis showed that in the next 2, 3, 4, 5, 6, 7, 8, 9, 10 age classes, the number of young individuals would gradually decrease, while the number of middle-aged, adult and old individuals would gradually increase, indicating that the maintenance of T. amurensis population mainly depends on the latter in the future. The biological characteristics and habitat are the main factors limiting the population growth of T. amurensis. We suggest that the seedling raising should be strengthened to improve the survival rate of the seedlings and small trees, and the habitat should also be protected to enhance natural regeneration and restoration of the T. amurensis population. 参考文献 相似文献 引证文献

Using a Simple Model to Determine the Best Management Regimes for Plantations at the Stand Level: A Case Study of Moshao Forest Farm in the Red-Soil Hilly Region of Southern China

Plantations in Southern China are experiencing several major problems concerning even-aged forest structures and dwindling ecosystem services under traditional forest management. The objective of this study was to determine the best management regimes (BMRs) for sustainable forest management using the Moshao forest farm as a case study. We constructed a framework for BMR modeling characterized by highly scheduled timber production (STP), low fluctuations in periodically scheduled timber harvest levels (FPS), and age class structure (ACS) at the end of the planning horizon. A paired analysis was conducted between the three indicators to identify suitable management planning for long-term timber production. Our results suggest that STP, FPS, and ACS are correlated, enabling the control of these forest performance indicators by setting various harvesting intensities in a planning horizon. We found that management regimes (MRS) with cutting area percentages from 20% to 40% and a cutting period of 10 years combined with small-area clear-cutting (≤5 ha) are optimal (MR6–MR10) for the Moshao forest farm in Southern China. In particular, MR with a cutting area percentage of 35% is the best option (MR9). These findings suggest that an applicable MR is designed by identifying the optimal harvesting intensity. The current local harvesting intensity can be properly increased to balance between timber production and ecological impacts on plantations.

Economic impacts of partial harvesting: Mitigating mid-term timber supply shortages as a result of pest outbreaks

Natural disturbances such as pest outbreaks have a significant impact on forest dynamics and services, including the loss of mature stands. From a wood production perspective, these disturbances can lead to long-lasting imbalances in the overall age-class structure of the forest, potentially resulting in a shortage of mature harvestable stands. Researchers from Natural Resources Canada’s (NRCan) Canadian Forest Service (CFS) have made a timber supply analysis of the Dunière forest located in the centre of the Gaspé Peninsula (Québec). This region suffers from an age-class structure imbalance caused by an eastern spruce budworm (ESB) outbreak that ended in 1984, and is consequently facing a reduced annual allowable cut, leading to long- term implications for the regional forest sector. The authors suggest that partial harvesting – the removal of a proportion of timber in a mature stand several years before a final cut is carried out – is a promising opportunity in the ESB-affected area for mitigating mid-term timber supply shortages by smoothing the fibre supply over time.

Population status and protection evaluation of Syzygium album, a species with extremely small population.

Syzygium album is a plant species with extremely small population and endemic to Yun-xiao County, Fujian Province. We examined its population status and conservation evaluation. The results showed that there were 25 individuals of S. album, with only one mother tree. Except for the mother tree and one small tree, the others were all young seedlings, which was rare in abundance and lack of age stage of middle and strong trees. The spatial distribution of young seedlings was not uniform, with most of individuals within the range of 10-25 m from the mother tree. The age class structure of the population was not continuous and the population development was unsustainable. The competition mainly came from other species. Cryptocarya chinensis accounted for 66.6% of the total competition index, which was much higher than other species. We established a comprehensive evaluation index system for the protection of rare and endangered plants with extremely small populations and evaluated the protection of S. album from three aspects, i.e., endangered degree, protection value, and protection priority. The endangered degree of S. album was level Ⅰ (the endangered degree index was 4.510), belonging to extremely endangered species, the protection value was level Ⅰ (the protection value index was 4.052), which was of great value, and the protection priority was level Ⅰ (the protection priority index was 4.016), which should be listed as the highest priority protection level.

濒危树种五莲杨种群结构与动态特征

五莲杨（Populus wulianensis）为山东特有种，属于极小种群野生植物。以昆嵛山国家级自然保护区内的五莲杨种群为研究对象，旨在通过建立静态生命表，绘制种群存活曲线来描述其种群的结构特征，使用4个生存函数进行种群的生存分析，运用数量动态指数定量描述种群的数量动态特征，并采用谱分析方法揭示种群年龄结构更替过程的周期性和结构的波动性。结果表明：（1）五莲杨种群龄级结构呈基部极宽顶部狭窄的金字塔形，种群存活曲线趋近于Deevey-Ⅲ型，幼龄个体数量丰富但存活率极低，种群增长性低；（2）死亡率和消失率曲线呈现"降低-增长-降低-增长"的复杂动态变化，种群在Ⅰ龄级死亡率最高；（3）生存分析表明该种群生存力低，具有前期锐减，中期和后期衰退的特点，呈现衰退特征；（4）种群数量动态指数显示种群呈增长趋势，但种群稳定性差且抗干扰能力弱；（5）谱分析表明该种群除受到基波影响外还受到个别小周期波动的显著影响。繁殖策略、有限的空间和资源是限制五莲杨种群增长的主要因素。建议对五莲杨种群进行原地保护的同时，通过输入实生苗防止种群在多个世代后因无性繁殖而导致抗性和遗传多样性降低。;Populus wulianensis, a wild plant species with extremely small population, is endangered and endemic in Shandong Province, China. In this study, the structural characteristics of P. wulianensis population distributed in Kunyu Mountain National Nature Reserve was investigated by establishing a static life table and drawing population survival curves. Four survival functions, number dynamic index, and the spectral analysis were used to describe survival status, population dynamics and the periodicity and structural volatility of the population-age-structure replacement process of P. wulianensis, respectively. The results are as follows. Firstly, the age-class structure of P. wulianensis population was a pyramid type with a very wide base and a narrow top. Its population survival curve appeared as Deevey-Ⅲ type. The number of young individuals was abundant but the survival rate was at an extremely low level. The population growth rate was very low. Secondly, the tendency of mortality and vanish curves was decrease-increase-decrease-increase, which showed the mortality rate of P. wulianensis population was the highest at age class Ⅰ. Thirdly, its survival analysis revealed that P. wulianensis population was at an extremely low viability level in the whole life cycle with the characteristics of a sharp decrease in the early stage and decline in the middle and late stages. Fourthly, although population dynamic index suggested that the population was increasing, its population stability was poor and the anti-interference ability was weak. Fifthly, spectral analysis demonstrated that the population was not only affected by the fundamental wave but also significantly affected by some separated small periodic fluctuations. Reproduction strategy, limited space and resource conditions are the major factors limited the growth of P. wulianensis population. Given these, in situ conservation should be introduced and seedlings importation is also recommended so as to avoid the population from decreasing resistance and genetic diversity due to asexual reproduction after multiple generations.

Understanding growth and age of red tree corals (Primnoa pacifica) in the North Pacific Ocean.

Massive, long-lived deep-sea red tree corals (Primnoa pacifica) form a solid, layered axis comprised of calcite and gorgonin skeleton. They are abundant on the outer continental shelf and upper slope of the Northeast Pacific, providing habitat for fish and invertebrates. Yet, their large size and arborescent morphology makes them susceptible to disturbance from fishing activities. A better understanding of their growth patterns will facilitate in-situ estimates of population age structure and biomass. Here, we evaluated relationships between ages, growth rates, gross morphological characteristics, and banding patterns in 11 colonies collected from depths of ~141–335 m off the Alaskan coast. These corals ranged in age from 12 to 80 years old. They grew faster radially (0.33–0.74 mm year-1) and axially (2.41–6.39 cm year-1) than in previously measured older colonies, suggesting that growth in P. pacifica declines slowly with age, and that basal diameter and axial height eventually plateau. However, since coral morphology correlated with age in younger colonies (< century), we developed an in-situ age estimation technique for corals from the Northeast Pacific Ocean providing a non-invasive method for evaluating coral age without removing colonies from the population. Furthermore, we determined that annual bands provided the most accurate means for determining coral age in live-collected corals, relative to radiometric dating. Taken together, this work provides insight into P. pacifica growth patterns to inform coastal managers about the demographics of this ecologically important species. With this new ability to estimate the age of red tree corals in-situ, we can readily determine the age-class structure and consequently, the maturity status of thickets, using non-invasive video survey techniques when coupled with mensuration systems such as lasers or stereo-cameras. Enhanced surveys could identify which populations are most vulnerable to disturbance from human activities, and which should be highlighted for protection.

Urbanization is associated with differences in age class structure in black-capped chickadees (Poecile atricapillus)

Urbanization has a tremendous impact on the environment from landscape features to distribution of food resources. Such drastic environmental changes can result in community, population, and individual differences between urban and non-urban animals. Urbanization has been associated with differential mortality and reproduction and therefore, differences in age structure may also be expected across urban gradients. Additionally, many traits studied along urban gradients, such as morphology, can also differ across age classes, and as such, age is an important factor to consider. Despite this, differences in age structure along urbanization gradients have only rarely been examined. Here, we use black-capped chickadee (Poecile atricapillus) age, morphological, and feeder visitation data to address whether age structure, morphology, and age-related winter survival differ across a gradient of urban land use in and around Ottawa, ON. We test the hypothesis that urbanization is associated with higher proportions of juveniles, because of an increased exploratory tendency by juveniles against the hypothesis that urbanization favors higher proportions of adults because of a slower pace of life. We further hypothesize that urban chickadees will be smaller than non-urban ones, because anthropogenic environments will attract both younger and worse quality individuals. We found that urban environments were associated with significantly higher proportions of first year individuals and these proportions remained stable from late fall through all of winter. We did not, however, find evidence that age related differences explained variation in morphology. Instead variation in morphology was small and inconsistently associated with both urbanization and age. The results stand in contrast to results for two species of European birds. The present study calls for using broadly available but under-exploited data to better understand urbanization-related differences in age structure and its implications for population-level processes such as disease transmission and information flow.