Viability of mountain caribou in British Columbia, Canada: Effects of habitat change and population density

Population viability analyses (PVA) are frequently employed to develop recovery plans and inform management of endangered species. Translating results from PVA into meaningful management recommendations often depends on an understanding of how population parameters change with environmental conditions as well as population density. The decline of mountain caribou (Rangifer tarandus caribou) in British Columbia, Canada, is believed to be caused by apparent competition with alternative prey species following changes to the forest age structure from timber harvest and wildfire. In addition, populations have been shown to decline at faster rates at low population density. To evaluate the potential effects of habitat change and population density on population persistence, we used stochastic projection models for 10 distinct populations varying in initial size from <10 to approximately 150 females. In an initial model, we used estimates of vital rates based on information sampled from >350 radiocollared caribou between 1984 and 2004. We then compared the results of the initial model to a set of models that evaluated the effects of habitat conditions and population density via their expected relationships to female adult survival. Assuming that vital rates remain constant over a 200-year time frame, only three populations have high probabilities (>0.95) of extinction. When models incorporate the declines in adult female survival know to occur with increasing proportions of young forest and declining population densities, all 10 populations are predicted to decline to extinction within <200 years. Based on our results, we suggest that PVA models that fail to incorporate the effects of changes in vital rates with habitat and population density may lead to overly optimistic assessments of the probability of population persistence in endangered species.     

种群生存力分析及其在自然保护区设计中的应用

论述了种群生存力分析(PVA)的定义、原理及其在自然保护区设计中的应用,讨论了种群分析法与分析模型在自然保护区设计中的应用问题,应用旋涡模型(Vortex Model)对关键种黄腹角雉种群生存力进行了模拟分析,并以模拟结果为例,重点探讨了在自然保护区设计中如何确定面积大小能满足关键种的保护需要以及如何进行功能分区等热点问题.     

Cost-efficient conservation for the white-banded tanager (Neothraupis fasciata) in the Cerrado, central Brazil

Population viability analyses are widely used to support decisions for the management of single species, but there are few studies that explicitly take into account realistic economic costs. In this study we determine the most cost-efficient conservation management options for the white-banded tanager (Neothraupis fasciata) in the protected areas of the Cerrado in central Brazil. We use the PVA model VORTEX to simulate the ability of different management options to improve population persistence and then assess the effectiveness of each option given a fixed budget. We discover that the best strategy for improving the viability of white-banded tanager populations is to use fire management and nest protection to increase fecundity. In small reserves and a low budget then fire management alone is the best strategy, but if the budget is larger fire management with nest protection as a mixed strategy is better. In large reserves the best strategy is to do nest protection and with large budgets there is a negligible difference between spending all the money on nest protection versus a mixed strategy. If we had not included financial considerations in our analysis of management options then we would have discarded fire management as an option, even though it can be the best strategy.     

聚吡咯/纤维素导电复合织物的制备及表征

以亚麻和棉织物为基底材料,利用原位吸附聚合法和吸附胶团聚合法制备聚吡咯(PPy)/纤维素导电复合织物.采用SEM、FTIR、XRD和XPS研究并对比分析了两种方法制得的复合织物的表面形貌、界面结合、组织结构和元素原子数分数,并测定了表面电阻率.结果发现原位吸附聚合法在织物表面沉积的聚吡咯有一部分松散地分布于表层上,牢度较差;而添加了聚乙烯醇(PVA)的吸附胶团聚合法在织物表面沉积的聚吡咯则非常均匀、致密;两种方法制备的导电织物均为PPy与纤维素织物的复合产物,界面结合无明显差异.在复合的过程中,基底织物中的纤维素的化学结构和结晶状态未发生改变;吸附胶团聚合法中,PVA起到了模板的作用;添加PVA的吸附胶团聚合法比原位吸附聚合法所制得的复合织物的表面电阻率低,是较好的制备导电织物的方法.     

Nanocellulose reinforced PVA composite films: Effects of acid treatment and filler loading

Nanocellulose was prepared by acid hydrolysis of microcrystalline cellulose (MCC) at different hydrobromic acid (HBr) concentrations. Polyvinyl alcohol (PVA) composite films were prepared by the reinforcement of nanocellulose into a PVA matrix at different filler loading levels and subsequent film casting. Chemical characterization of nanocelluloses was performed for the analysis of crystallinity (X_c), degree of polymerization (DP), and molecular weight (M_w). The mechanical and thermal properties of the nanocellulose reinforced PVA films were also measured for tensile strength and thermogravimetric analysis (TGA). The acid hydrolysis decreased steadily the DP and M_w of MCC. The crystallinity of MCC with 1.5 M and 2.5 M HBr showed a significant increase due to the degradation of amorphous domains in cellulose. Higher crystalline cellulose showed the higher thermal stability than MCC. From X-ray diffraction (XRD) analysis, nanocellulose samples showed the higher peak intensity than MCC cases. Reduction of MCC particle by acid hydrolysis was clearly observed from scanning electron microscope (SEM) images. The tensile and thermal properties of PVA composite films were significantly improved with the increase of the nanocellulose loading.     

一种复合型成膜剂的成膜性能测定及其对生防菌抑菌活性的影响

制备了不同比例的聚乙烯醇-羧甲基纤维素钠-钠基膨润土共混膜。结果表明:以质量浓度2%的聚乙烯醇(PVA)、1%的羧甲基纤维素钠(SCMC)及0.3%的钠基膨润土(Na-B)制得PVA-SCMC-Na-B共混膜,其成膜时间为7 min、粘度为480 mPa · s,对棉种的包衣均匀度为98%,包衣脱落率为 0.15%,并具有良好的水溶性和吸水溶胀性,而且共混膜对微生物的生长及抑菌活性、种子发芽率几乎无影响,可为新型绿色生物种衣剂的应用及推广提供参考。     

PVA复合剂对苹果等采后保鲜及生理效应

通过对苹果、碰柑等自然低温下和桃货架温度下涂 PVA复合剂贮藏和贮期跟踪测定发现,PVA复合剂分别可减少两类贮温下果实贮期失水70%、50%以上,保鲜率提高5.3%～24.8%。贮期处理果的呼吸强度不同程度得以降低。经该剂处理的桃对贮放环境O₂的消耗量始终低于对照,而CO₂的积累量则始终高于对照,果实内部CO₂浓度增长较快。伴随着Vc氧化酶活性的下降,处理果Vc含量持续大于对照。     

Minimum viable population and conservation status of the Atlantic Forest spiny rat Trinomys eliasi

A population viability analysis (PVA) was conducted to assess the minimum viable population (MVP) of the Atlantic Forest spiny rat Trinomys eliasi, a species threatened by habitat loss and restricted geographical distribution. Objectives were to suggest quasi-extinction thresholds, estimate minimum areas of suitable habitat (MASH) and MVPs, and compare results with the species’ current status. The computer package VORTEX was used. The model predicted sizes of 200 animals to achieve demographic stability, but buffering declines in genetic variability required populations of 2000 animals. Estimated MASHs were approximately 250 and 2500 ha for demographic and genetic stability, respectively. Mortality rate and mean litter size were the most sensitive parameters to changes in model assumptions. The protection of known populations and the search for extant populations are the first steps in conservation. T. eliasi's issue could help protecting the coastal shrubland ecosystem of Rio de Janeiro state. Observing IUCN's criteria for listing threatened species, it is suggested that T. eliasi should be ranked as vulnerable in red lists.     

Probable consequences of high female mortality for speckled warblers living in habitat remnants

The effects of habitat fragmentation on the Australian avifauna have been widespread with species richness and abundance declining with reduced remnant size and habitat quality and increased habitat isolation. The speckled warbler, Chthonicola sagittata is one species from the highly fragmented temperate woodlands of eastern Australia that has declined across its range and populations that remain appear to be patchily distributed in habitat remnants. Specific causes of decline are unknown but several aspects of its biology make the species particularly vulnerable to decline in fragmented landscapes. Here, we analyse survey data (presence/absence) of speckled warblers in a large sample of habitat remnants from three regions to identify patterns of occupancy. We explore the effects of patch size on extinction risk using population viability analyses (PVA) and detailed demographic data from a behavioural study of individuals in the Australian Capital Territory, south-eastern Australia. Patch size was a strong predictor of the persistence of speckled warblers in habitat remnants. High density populations had higher probabilities of persisting, and inclusion of an Allee effect during drought decreased the probability of persistence. In the absence of an Allee effect, only high density populations in patches greater than 300 ha and low density populations in patches greater than700 ha had more than an 80% probability of persisting over 100 years. The accelerating decrease in population persistence below approximately 200-400 ha suggests that small populations were particularly vulnerable to stochastic demographic and environmental events. Adult female mortality was the single most important factor in driving population extinction. Our PVA model predictions matched the survey data for the Australian Capital Territory region remarkably well, but failed to predict occupancy rates in remnants in other regions. Differences in occupancy patterns between regions may, however, have resulted from inbreeding depression. This study demonstrates both the strengths and limitations of PVA analysis. PVA can predict occupancy patterns with reasonable accuracy, given good demographic data, but data for one region cannot be used universally for all regions. We highlight the need for studies of demography in different regions to interpret regional patterns of occupancy and to identify mechanisms of decline in remnant habitat.     

PVA包膜缓释肥料在旱稻上施用效果

对自行研制的3种包膜缓释肥料(PG、PGg、PG f)的肥效进行旱稻盆栽试验。试验结果表明:所研制的包膜肥料具有较好的养分缓释效果,能使土壤中长时间保持较高的养分含量,包膜肥料缓释效果PGg型优于PG型和PG f型。相同试验条件下,PGg处理株高和生物量比对照处理(CK)分别增加了15.7%和12%,氮素利用率比CK提高了7.5%,减少了氮素损失。