Competition between heather and grasses on Scottish moorlands: Interacting effects of nutrient enrichment and grazing regime

Abstract. Considerable losses and degradation of heathlands (in moorlands and lowlands) have been reported across Europe, with Calluna vulgaris (heather) being replaced by other species, often grasses. Increasing atmospheric nitrogen deposition and overgrazing have been suggested as the driving factors behind this change. This possibility was investigated in a study of the interacting effects of nutrient inputs and grazing on heather and three grass species (Nardus stricta, Deschampsia cespitosa and D. flexuosa) in the field, on a moorland in northeastern Scotland. In addition, the interacting effects of increasing nutrients and Calluna canopy height on N. stricta and D. cespitosa were studied using turves in an outdoor experimental area. In the field, fencing had a larger effect than fertilizer on the growth of all species, except for N. stricta, the species most unpalatable to herbivores. Fencing led to an increase in the height of the Calluna canopy, which may reduce light availability for the grasses. In the turf experiment, the height of the Calluna canopy affected the diameter of the grass tussocks and percentage of green matter (i.e. live leaf material), with plants under the more closed Calluna canopies being smaller. This study suggests that the slow‐growing, evergreen Calluna is a more effective competitor than the faster growing grasses when it has a tall, intact canopy, even at increased levels of nutrient supply. However, overgrazing promotes gap formation in the Calluna canopy, providing an opportunity for grasses to take advantage of increased nutrients. Thus the conservation of heather moorlands requires an understanding of the grazing level which allows Calluna to maintain sufficient canopy structure to outcompete grasses for light.     

龙脑型阴香截顶采收技术研究

以2年生龙脑型阴香Cinnamomum burmannii chvar. Borneol幼林为研究对象,开展截顶采收技术试验,试验设置4个截顶高度,每个截顶高度内又采用3种下部枝条处理模式。通过对2个年度3次调查数据进行分析,结果表明树高、地径、冠幅和可蒸生物量4个性状不同区组间本底差异不大,处理后4个性状不同处理间差异显著加大,且均达极显著水平;多重比较也从本底的2个DUNNCAN分组提升至3～4个分组,且可以看出随着截干高度的提升,4个性状指标逐渐提升;在留枝方面,保留枝条越少,4个性状指标数值越小。因此,采收以120 cm高度截顶后保留下部枝条(H4-T1组合)为最佳处理。     

潮汐作用下干湿交替对黄河三角洲盐沼湿地净生态系统CO2交换的影响

潮汐作用作为盐沼湿地独特的水文特征能在短时间内强烈影响盐沼湿地的碳平衡.利用涡度相关和微气象监测技术,对黄河三角洲盐沼湿地净生态系统CO₂交换(NEE)和环境因子进行监测,并同步监测潮汐变化,探究潮汐过程及潮汐作用下干湿交替对NEE的影响.结果表明: 潮汐过程促进了白天生态系统CO₂的吸收但未对夜晚CO₂的释放产生显著影响,潮汐淹水成为影响白天NEE的主要因子.干旱阶段和湿润阶段NEE的日平均动态均呈“U”型曲线,但干旱阶段NEE的变幅较小.干湿交替增强了白天生态系统CO₂的吸收,干旱阶段最大光合速率(A_max)、表观量子产量(α)和生态系统呼吸(R_eco)的均值均高于湿润阶段.此外,干湿交替减少了盐沼湿地夜晚NEE释放的同时增强了其温度敏感性.     

Gauging resource exploitation by juvenile Chinook salmon (Oncorhynchus tshawytscha) in restoring estuarine habitat

In the context of delta restoration and its impact on salmonid rearing, success is best evaluated based on whether out‐migrating juvenile salmon can access and benefit from suitable estuarine habitat. Here, we integrated 3 years of post‐restoration monitoring data including habitat availability, invertebrate prey biomass, and juvenile Chinook salmon (Oncorhynchus tshawytscha) physiological condition to determine whether individuals profited from the addition of 364 ha of delta habitat in South Puget Sound, Washington, United States. Productivity in the restored mudflat was comparable to reference sites 3 years after dike removal, surpassing a mean total of 6 million kJ energy from invertebrate prey. This resulted from the development of a complex network of tidal channels and a resurgence in dipteran biomass that was unique to the restoration area. Consequently, a notable shift in invertebrate consumption occurred between 2010 and 2011, whereby individuals switched from eating primarily amphipods to dipteran flies; however, dietary similarity to the surrounding habitat did not change from year to year, suggesting that this shift was a result of a change in the surrounding prey communities. Growth rates did not differ between restored and reference sites, but catch weight was positively correlated with prey biomass, where greater prey productivity appeared to offset potential density‐dependent effects. These results demonstrate how the realized function of restoring estuarine habitat is functionally dependent. High prey productivity in areas with greater connectivity may support healthy juvenile salmon that are more likely to reach the critical size class for offshore survival.     

Genetic variation of salt-stressed durum wheat (Triticum turgidum subsp. durum Desf.) genotypes under field conditions and gynogenetic capacity

Agriculture has new challenges against the climate change: the preservation of genetic resources and the rapid creation of new varieties better adapted to abiotic stress, specially salinity. In this context, the agronomic performance of 25 durum wheat (Triticum turgidum subsp. durum Desf.) genotypes (nineteen landraces and six improved varieties), cultivated in two semi-arid regions in the center area of Tunisia, were assessed. These sites (Echbika, 2.2?g?l^?1; Barrouta, 4.2?g?l^?1) differ by their degree of salinity of the water irrigation. The results showed that most of the agronomic traits (e.g. spike per meter square, thousand kernels weight and grain yield) were reduced by salinity. Durum wheat landraces, Mahmoudi and Hmira, and improved varieties, Maali and Om Rabia showed the widest adaptability to different quality of irrigation water. Genotypes including Jneh Kotifa and Arbi were estimated as stable genotypes under adverse conditions. Thereafter, salt-tolerant (Hmira and Jneh Khotifa) and the most cultivated high-yielding (Karim, Razzak and Khiar) genotypes were tested for their gynogenetic ability to obtain haploids and doubled haploid lines. Genotypes with good induction capacity had not necessarily a good capacity of regeneration of haploid plantlets. In our conditions, Hmira and Khiar exhibited the best gynogenetic ability (3.1% and 2.9% of haploid plantlets, respectively).     

Eco-Floristic studies of native plants of the Beer Hills along the Indus River in the districts Haripur and Abbottabad,Pakistan

The present study was conducted to elaborate vegetation composition structure to analyze role of edaphic and topographic factors on plant species distribution and community formation during 2013–14. A mixture of quadrat and transect methods were used. The size of quadrat for trees shrubs and herbs were 10 × 5, 5 × 2, 1 × 1 meter square respectively. Different phytosociological attribute were measured at each station. Primary results reported 123 plant species belong to 46 families. Asteraceae and Lamiaceae were dominant families with 8 species each. PCORD version 5 were used for Cluster and Two Way Cluster Analyses that initiated 4 plant communities within elevation range of 529–700 m from sea level. Indicator species analyses (ISA) were used to identify indicator species of each community. CANOCO Software (version 4.5) was used to measure the influence of edaphic and topographic variables on species composition, diversity and community formation. Whereas Canonical Correspondence Analysis (CCA) was used to measure the effect of environmental variables which showed elevation and aspect were the stronger environmental variable among topographic and CaCO₃ contents, electric conductivity, soil pH were the stronger edaphic factors in determination of vegetation and communities of the Bheer Hills. Grazing pressure was one of the main anthropogenic factors in this regard.     

Spillover of Drosophila suzukii between noncrop and crop areas: implications for pest management

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Trade-off between height growth and stem diameter growth for an evergreen Oak, Quercus glauca, in a mixed hardwood forest

1. Patterns of stem growth of a mid-successional evergreen Oak species ( Quercus glauca ) in a mixed hardwood forest were examined to explore the trade-off relationship between stem-diameter growth and height growth.
2. The mean cross-sectional area (and the corresponding mean diameter) of a stem at a point in time was defined as the stem volume divided by tree height. Based on this definition, a simple equation representing the trade-off relationship between the height growth and mean diameter growth was formulated.
3. In the long term, allocation to height growth was encouraged at the seedling stage and it gradually declined with time, with the decline in the suppressed seedlings being more pronounced than in the dominant trees.
4. However, both the suppressed and the dominant trees showed acceleration of height growth at various ages. Such a fluctuation in the allocation of biomass to height growth is likely to have been caused by chronological changes in light conditions, and meandered the trajectory of allometry between the height and mean diameter.
5. The observed stem growth patterns of the individual trees could explain the chronological changes in the diameter–height relationship of the population.     

Body build structure of neonates

The paper presents anthropometric data on 292 healthy neonates delivered of normal births at the Women's Hospital of Tartu University (150 boys and 142 girls). The parameters of the neonates' physical development measured included height, weight, sitting height, length of sternum and abdomen, shoulder width, upper and lower width and depth of thorax, width and depth of abdomen, D. cristarum, D. trochanterica, pelvic depth, 12 circumferences, foot length and two skinfolds (on abdomen and back). The mean weight of a neonate was 3620.5 g±448.7 g (minimum 2400 g and maximum 4854 g). Boys were somewhat heavier than girls (3684.7 g and 3551.3 g respectively). The average height of the infants was 49.9 cm±1.9 cm (minimum 44 cm and maximum 54.5 cm). Correlation analysis of the characteristics showed that body structure is a system of wellcorrelated anthropometric measurements where the leading role belongs to height and weight. The changes in the relation between height and weight (height-weight classification in 3×3SD classes) cause systemic changes in other measurements. Therefore, in further micropaediatric and clinical research, the height-weight classification could be used as the primary model of the body as a whole.     

内蒙古锡林河流域三种草原蝗虫对植物高度选择的观察

在实验条件下,观察了发生期及个体大小不一致的3种草原蝗虫对植物高度选择情况．结果表明：蝗虫对植物高度的选择与其本身发生时期及个体大小相关,是物种长期进化的结果,同时,还探讨了蝗虫对植物高度的选择与温度、温度及光照强度之间的关系．