Potential seasonal ecological challenge of heat strain among Australian Aboriginal people practicing traditional subsistence methods: a computer simulation

It has been largely accepted that Australian Aboriginal people practicing hunting and gathering traditionally underused their objective economic possibilities by working short hours relative to nonhunter-gatherer populations. However, the possibility that their subsistence quest might have been limited by potential heat strain has not been considered for Australian hunter-gatherers. In this article the influence of work and heat load on the potential for heat strain among adult male Australian Aboriginal people is modelled. The possibility that the short working day of Arnhem Land adults reported in the literature might reflect ecologically limited work scheduling by way of potential heat strain is examined. Three climatic regions of the North of Western Australia and the Northern Territory were identified, using data available from the Australian Bureau of Meteorology. Data from the months of January, April, July, and October were used with the United States Army Heat Strain Model, along with assumptions with respect to work load and time scheduling. Predictive modelling indicates that a late start to the working day could carry considerable risks of potential heat strain during the summer, when humidity and maximum daily temperature are highest for all three climatic regions, but especially in the tropical coastal region. While extended work times may have been needed to acquire adequate food under traditional conditions, work output could have been limited by potential heat strain under some conditions likely to have prevailed.     

Demand for sucrose in the genetically obese Zucker (fa/fa) rat

Obese Zucker rats (fa/fa) eat more food than lean controls in free-feeding conditions, which strongly influences their phenotypic expression. Few studies, however, characterize their food consumption in environments that are more representative of foraging conditions, e.g., how effort plays a role in food procurement. This study examined the reinforcing efficacy of sucrose in obese Zucker rats by varying the responses required to obtain single sucrose pellets. Male Zucker rats (15 lean, 14 obese) lever-pressed under eight fixed ratio (FR) schedules of sucrose reinforcement, in which the number of lever-presses required to gain access to a single sucrose pellet varied from 1 to 300. Linear and exponential demand equations, which characterize the value of a reinforcer by its sensitivity to price (FR), were fit to the number of food reinforcers and responses made. Free food consumption was also examined. Obese Zuckers, compared to leans, consumed more food under free-feeding conditions. Moreover, they had higher levels of consumption and response output, but only at low FR values. Both groups were equally sensitive to price increases at higher FR values. This suggests that environmental conditions may interact with genes in the expression of food reinforcer efficacy.     

Recent book

In the present study, the overall economic impact of hull fouling on a mid-sized naval surface ship (Arleigh Burke-class destroyer DDG-51) has been analyzed. A range of costs associated with hull fouling was examined, including expenditures for fuel, hull coatings, hull coating application and removal, and hull cleaning. The results indicate that the primary cost associated with fouling is due to increased fuel consumption attributable to increased frictional drag. The costs related to hull cleaning and painting are much lower than the fuel costs. The overall cost associated with hull fouling for the Navy's present coating, cleaning, and fouling level is estimated to be $56M per year for the entire DDG-51 class or $1B over 15 years. The results of this study provide guidance as to the amount of money that can be reasonably spent for research, development, acquisition, and implementation of new technologies or management strategies to combat hull fouling.     

Mixed crop–livestock farming systems: a sustainable way to produce beef? Commercial farms results,questions and perspectives

Mixed crop–livestock (MC–L) farming has gained broad consensus as an economically and environmentally sustainable farming system. Working on a Charolais-area suckler cattle farms network, we subdivided the 66 farms of a constant sample, for 2 years (2010 and 2011), into four groups: (i) ‘specialized conventional livestock farms’ (100% grassland-based farms (GF), n=7); (ii) ‘integrated conventional crop–livestock farms’ (specialized farms that only market animal products but that grow cereal crops on-farm for animal feed, n=31); (iii) ‘mixed conventional crop–livestock farms’ (farms that sell beef and cereal crops to market, n=21); and (iv) organic farms (n=7). We analyse the differences in structure and in drivers of technical, economic and environmental performances. The figures for all the farms over 2 years (2010 and 2011) were pooled into a single sample for each group. The farms that sell crops alongside beef miss out on potential economies of scale. These farms are bigger than specialized beef farms (with or without on-farm feed crops) and all types of farms show comparable economic performances. The big MC–L farms make heavier and consequently less efficient use of inputs. This use of less efficient inputs also weakens their environmental performances. This subpopulation of suckler cattle farms appears unable to translate a MC–L strategy into economies of scope. Organic farms most efficiently exploit the diversity of herd feed resources, thus positioning organic agriculture as a prototype MC–L system meeting the core principles of agroecology.     

New seed morphological features in Moehringia L. (Caryophyllaceae) and their taxonomic and ecological significance

Abstract

Relative growth rate (RGR) is a fundamental trait for comparative plant ecology but cannot be measured in situ, leading to problems in interpreting vegetation function. However, the components of RGR (net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), and specific leaf area (SLA)) can be calculated for wild plants from morphological measurements (leaf area, leaf dry mass, whole plant dry mass), which potentially reflect RGR. Seeds of 19 species from Italian prealpine calcareous grasslands were collected and seedlings were cultivated under controlled conditions. RGR, NAR, LAR, LWR and SLA were analysed. The results demonstrated that RGR was positively correlated with SLA and LAR (p < 0.01). Furthermore, LAR was positively correlated with LWR and negatively with NAR (p < 0.05). Monocotyledons showed significantly higher LAR, LWR and NAR than dicotyledons, as the latter allocated a greater proportion of biomass to stems, but RGR and SLA showed no such phylogenetic constraint. Therefore SLA is the most reliable indicator of RGR in ecological and functional surveys of prealpine calcareous grasslands, and has the additional advantage that it can be measured from leaf material alone. Lower mean RGR and SLA for calcareous grassland species suggests that this vegetation is less likely to recover from the effects of disturbance than meadows and dry meadows.     

Patterns of intraspecific trait variation along an aridity gradient suggest both drought escape and drought tolerance strategies in an invasive herb

Background and AimsIn water-limited landscapes, some plants build structures that enable them to survive with minimal water (drought resistance). Instead of making structures that allow survival through times of water limitation, annual plants may invoke a drought escape strategy where they complete growth and reproduction when water is available. Drought escape and resistance each require a unique combination of traits and therefore plants are likely to have a suite of trait values that are consistent with a single drought response strategy. In environments where conditions are variable, plants may additionally evolve phenotypically plastic trait responses to water availability. Invasive annual species commonly occur in arid and semi-arid environments and many will be subject to reduced water availability associated with climate change. Assessing intraspecific trait variation across environmental gradients is a valuable tool for understanding how invasive plants establish and persist in arid environments.MethodsIn this study, we used a common garden experiment with two levels of water availability to determine how traits related to carbon assimilation, water use, biomass allocation and flowering phenology vary in California wild radish populations across an aridity gradient.Key ResultsWe found that populations from arid environments have rapid flowering and increased allocation to root biomass, traits associated with both drought escape and tolerance. Early flowering was associated with higher leaf nitrogen concentration and lower leaf mass per area, traits associated with high resource acquisition. While trait values varied across low- and high-water treatments, these shifts were consistent across populations, indicating no differential plasticity across the aridity gradient.ConclusionsWhile previous studies have suggested that drought escape and drought resistance are mutually exclusive drought response strategies, our findings suggest that invasive annuals may employ both strategies to succeed in novel semi-arid environments. As many regions are expected to become more arid in the future, investigations of intraspecific trait variation within low water environments help to inform our understanding of potential evolutionary responses to increased aridity in invasive species.     

江苏沿海滩涂围垦与社会经济发展的耦合关系

沿海滩涂湿地是脆弱的生态敏感区,滩涂围垦是沿海国家和地区拓展土地资源的重要方式之一。近年,沿海地区快速城市化下的滩涂围垦导致了沿海湿地生态系统退化等一系列环境问题。基于环境库兹涅茨曲线（Environmental Kuznets Curve,EKC）模型,以江苏北部沿海湿地为研究区,结合遥感影像和社会经济数据,刻画滩涂围垦过程、强度及社会经济发展过程,揭示近40年江苏沿海滩涂围垦主要类型、阶段性变化特征,阐述滩涂围垦与社会经济发展的耦合关系。研究结果显示,养殖水体扩张是近40年江苏滩涂围垦利用的主要方式;相比养殖水体聚集发展的盐城市,以启东为典型代表的南通市经历了相对较完整的养殖水体的滩涂围垦过程,其养殖水体面积与区域渔业产值存在指数关系,即当人均地区产值达到约9.55万元时,区域渔业产值的增长不再以通过围垦增加养殖水体面积为主要途径;从江苏沿海滩涂围垦来看,滩涂围垦与社会经济发展之间存在典型倒U型曲线关系。苏北滩涂围垦可分为3个阶段,初期阶段（1980-2005年）,滩涂围垦随着经济发展而急剧增加;中期（2005-2014年）,当人均GDP约为3.64×10⁴元时滩涂围垦速度达最大;后期（2014-2018年）,滩涂围垦随着经济发展呈现下降趋势。3个阶段中,单位滩涂围垦面积与人均GDP增长关系由4.11元/km²,17.08元/km²增加至60.77元/km²,呈显著增加的趋势。经济发展,农业和农村经济改革以及国家和地方各级政策均对滩涂围垦具有重要影响。严格的国家环境保护政策将是有效控制滩涂围垦、保护生态环境的重要手段。     

武夷山49种木本植物叶片与细根经济谱

植物经济谱能够阐述维管植物在资源获取和储存之间的权衡策略, 为理解生态位分化和物种共存机制等提供科学依据。该研究通过对武夷山49种木本植物的单叶面积(ILA)、比叶面积(SLA)、叶碳含量(LCC)、叶氮含量(LNC)和叶磷含量(LPC)等5个叶片性状以及根组织密度(RTD)、比根长(SRL)、比根面积(SRA)、根碳含量(RCC)、根氮含量(RNC)和根磷含量(RPC)等6个细根性状进行测定, 探讨木本植物叶片与细根经济谱是否存在以及常绿和落叶物种间的植物经济谱差异。结果表明: 沿着性状贡献率相对较大的PC1轴, 能够定义出叶经济谱(LES)、根经济谱(RES)和整株植物经济谱(WPES)。大部分常绿物种分布在经济谱保守的一侧, 而大部分落叶物种聚集在获取的一侧。此外, 叶片PC1、细根PC1和整株植物PC1的两两得分之间均存在显著正相关关系, 常绿和落叶物种具有共同的异速指数, 但不存在共同的异速常数。这些结果揭示了亚热带物种叶片与细根的策略遵循着WPES的协调整合, 表明叶片、细根以及整株植物之间是采取协同变化的资源策略, 而分布于经济谱两端的常绿和落叶物种则是通过不同的方式来构建WPES。     

Linking root respiration to chemistry and morphology across species

Root respiration is a critical physiological trait involved in root resource acquisition strategies, yet it is less represented in root trait syndrome. Here we compiled a large dataset of root respiration associated with root chemical and morphological traits from 245 plant species. Our results demonstrated that root respiration correlated positively with root nitrogen concentration (RNC) and negatively with root tissue density (RTD) across and within woody and non‐woody species. However, the relationships between root respiration and specific root length (SRL) and root diameter (RD) were weak or even insignificant. Such root respiration–traits relationships were not completely in line with predictions by the root economics spectrum (RES). Furthermore, the principal component analysis showed that root trait syndrome was multidimensional. Root respiration was associated more strongly with the RNC‐RTD axis (the classical RES) than with the orthogonal SRL‐RD axis for woody species, but not for non‐woody species. Collectively, the linkages of root physiological, chemical, and morphological traits provide a better understanding of root trait covariation and root resource acquisition strategies.