Spatial and temporal trends in abundance of Atlantic salmon, Salmo salar, in Newfoundland with emphasis on impacts of the 1992 closure of the commercial fishery

Closure of the Newfoundland commercial Atlantic salmon, Salmo salar L., fishery in 1992 was the most restrictive measure introduced to help rebuild depressed local stocks of salmon. Here, the effects of the closure are evaluated by analysing trends in abundance since 1984, and estimates of survival in both freshwater and marine environments derived from enumeration of salmon at fish counting facilities. While freshwater production of smolts generally has been maintained, marine survival rates remain low (2–10%), and highly variable. Overall, total stock size differs little from that prior to the closure of the commercial salmon fishery. Spawning escapements have increased by a factor of 2 or 3 in some rivers, but in other areas total returns are lower on average than those prior to the fishery closure. Factors other than exploitation are contributing to lack of stock recovery, resulting in continued conservation concerns.     

伊乐藻对污染水体中氮、磷的净化效果及其克藻效应

为了科学评价伊乐藻在水生态修复中的实际应用价值,在模拟条件下初步研究了沉水植物伊乐藻（Elodea nuttallii）对污染水体中氮、磷的净化效果及其克藻效应。结果表明,伊乐藻对总氮、氨态氮、硝态氮和总磷均具有一定的净化效果,并且水体中氮、磷起始浓度越高,其去除效果越明显;不同生物量伊乐藻对河水中其他藻类均具有较强抑制作用,并且随着生物量增加,其克藻效应更加明显。     

水柏枝的根系特征及固沙效果研究

[目的]为西藏砂质土和河滩区水土保持林建设提供理论基础。[方法]在西藏尼洋河滩区选取样地合标准木,采用整株挖掘法,每10cm为1层挖掘土壤,水冲法获取根系,测定不同级别根系的直径、长度和生物量。同时测定土样的有机质含量和土壤水稳性指数。[结果]各级别根系总长度顺序为2级〉3级〉4级〉1级;生物量顺序为：1级〉2级〉3级〉4级,其中2级根系的伸展能力最强。随着土层深度增加,水柏枝根系的生物量和长度均减小。水柏枝林地土壤抗侵蚀性能小于绣线菊和连翘,大于荒坡地。水柏枝具有提高林下土壤有机质含量的作用。[结论]水柏枝根系具有很好的固沙和保持水土的作用,可用于河滩区营造水土保持林。     

60Coγ射线辐照对野牛草坪用性状的诱变效应

[目的]对60Coγ射线辐照对野牛草坪用性状的诱变效应进行研究。[方法]以经不同辐照强度的60Coγ射线处理后的野牛草[Bu-chloe dactyloides(Nutt.)Engelm.]为试验材料,对其进行坪用相关性状的测定,分析不同γ射线不同辐照强度(1 200、1 400、1 600、1 800、2 000 Gy)对野牛草当代植株草坪相关性状的诱变效应。[结果]各辐照处理的野牛草发芽率变化趋势不一致,种苗的根长和芽长均小于对照;与对照相比,辐照处理后幼苗的高度显著变小,分蘖数、株高、叶长和叶宽均小于对照;匍匐茎长度、匍匐茎粗和匍匐茎节数与对照差异不显著。[结论]该研究为确定野牛草诱变育种的适宜γ射线辐射剂量及筛选有益突变体奠定基础。     

基于RS的徐州市地表温度与植被指数关系研究

以Landsat TM影像为数据源研究徐州市市区地表温度与植被指数的关系。研究表明,徐州市的地表温度存在明显的中心城区高、郊区低的热岛效应。而徐州市的归一化植被指数则表现为城市中心区总体偏小,植被覆盖较低。除水体外,植被指数与地表温度有明显的负相关关系。植被覆盖越高,地表温度越低,反之,则地表温度越高。     

红锥人工幼林施肥试验研究

试验研究表明，合理施肥能促进红锥人工幼林的生长，施肥量水平不同，其促生效果也不同，N、P、K肥对红锥人工幼林的生长具有同等重要的特性。综合本试验结果，红锥人工幼林的初步合理施肥量为每株尿素100g、钙镁磷150g、氯化钾50g，养分配比为2：3：1(尿素：钙镁磷：氯化钾)，超过该施肥量，已没有增产效益。特别应指出的是，在本试验的立地条件下，当每株施肥量尿素超过300g或钙镁磷肥超过450g或氯化钾超过150g时，均有可能发生肥害，需引起重视。     

生物化学复合防腐剂在橙汁防腐保鲜中的协同增效作用

该文以天然生物防腐剂乳酸链球菌素(Nisin)、化学防腐剂山梨酸钾、乙二胺四乙酸(EDTA)以及食品抗氧化剂异Vc钠为原料,对通过复配后得到的各组复合型防腐剂在橙汁保鲜中的协同增效作用进行研究,并且与单一的防腐剂保鲜效果进行比较,得出一组适合在橙汁中使用的高效复合型防腐剂。结果表明,上述各种抑菌剂单独使用时均不能完全抑制橙汁中微生物的生长;正交试验结果表明,当选择0.05 g/kg Nisin、0.1 g/kg山梨酸钾、0.01 g/kg异Vc钠、0.03 g/kg EDTA作为复配型抑菌剂的最佳添加配比时,能显著地抑制橙汁中微生物的生长,第14、17、21 d对菌落总数的抑制率分别达到99.9%、99.9%和99.6%,其抑菌效果显著优于单一防腐剂的抑菌效果。因此,Nisin与三者复合使用时具有协同增效性,该复合防腐剂添加至橙汁中可起到良好的防腐保鲜效果。     

Static home-based versus dynamic mobility-based assessments of exposure to urban green space

There is growing interest in urban green space exposure estimated dynamically by accounting for individuals’ mobility during daily life. We aimed to explore if daily green space exposure estimates based on individuals’ mobility substantially differ from static home-based exposure estimates, and to examine potential effect modification by personal (sex and work status) and temporal (weekends versus weekdays) characteristics. To assess the association between daily exposure to urban green space, we used home address and time-activity data collected from 1911 participants in western New York, US, using their GPS-enabled mobile phones. We abstracted both individuals’ home address based (home-based) and daily time activity based (mobility-based) green space exposures from the Normalized Difference Vegetation Index (NDVI). Then, we assessed the association between mobility-based and home-based exposure estimates using linear mixed effect regression models with subject-specific random effects. We also explored whether this effect was modified by individual-level characteristics, including work status and sex, as well as whether assessments took place on weekdays versus weekends. We found that daily dynamic exposure to urban green space based on individuals’ mobility was not substantially different from static exposure estimates based on one’s residence, but that there were statistically significant effect modifiers. Specifically, the correspondence between mobility-based and home-based exposure to green space was relatively lower for employed compared to unemployed participants, whereas their correspondence during weekends increased compared to weekdays. Our findings suggest that there is a strong correspondence between mobility-based and home-based exposure to urban green space, but that their associations are modified by personal and temporal characteristics. Further research is needed to confirm our finding for general population in other settings, such as different seasons and other regions.     

Can parkland mitigate mental health burden imposed by the COVID-19? A national study in China

The worldwide coronavirus disease 2019 (COVID-19) pandemic has seriously affected not only physical health but also mental wellbeing (i.e mental stress and suicide intention) of numerous urban inhabitants across the globe. While many studies have elucidated urban parkland enhances and mental wellbeing of urban residents, the potential for parkland to mitigate mental health burden imposed by the COVID-19 has received no attention. This nationwide study systematically explored the association between parkland, the COVID-19 pandemic situation and mental wellbeing from 296 cities in China. The study innovatively used big data from Baidu Search Engine to assess city-level mental wellbeing, thereby enabling comparisons among cities. The results show that the provision of parkland is positively associated with mental wellbeing during the COVID-19 epidemic. For COVID-19-related indicators, the geographical distance to Wuhan city, work resumption rate, and travel intensity within the city are also positively associated with mental wellbeing, while the number of COVID-19 infections and the proportion of migrants from Hubei Province for each city are negatively associated with mental wellbeing. Last, the most important finding is that parkland reduces the negative effect of COVID-19 on mental wellbeing during the COVID-19 epidemic. To achieve the goal of promoting mental wellbeing through urban planning and design during the future pandemics, policymakers and planners are advised to provide more well-maintained and accessible parkland and encourage residents to use them with proper precautions.     

Wealth and land use drive the distribution of urban green space in the tropical coastal city of Haikou,China

Urban green spaces (UGSs) provide a plethora of ecosystem services that benefit humans and wildlife within cities. UGS both promotes and is affected by overall urban ecological health, which can be measured by a wide range of indices. In this study, we investigated the distribution patterns and drivers of UGS within the tropical coastal city of Haikou, Hainan, China over the past decade using a combination of remote sensing data and field work. We interpreted Google earth images from 2010 and 2020 to determine the land cover of UGS within Urban Functional Units (UFUs). We collected socioeconomic variables to test if wealth, site age, and land use determine the proportion of UGS in the city. We found that the proportion of UGS in parks was the highest among all UFUs in 2010 and 2020. In general, UGS increased with maintenance frequency and housing price, which are proxies for the luxury effect. However, land use also played a role in UGS distribution across UFUs, especially in transportation areas, recreation and leisure districts, and residential districts. Haikou is similar to other cities in showing a positive luxury effect on the distribution of UGS. Our results highlight the key roles that parks, colleges and universities, and research institute areas have played in maintaining stable green space within Haikou over the past decade. We suggest that relatively recently implemented governmental programs to increase green space elsewhere in the city may not yet have achieved success within the time span that we analyzed.