Changes in plant species richness and productivity in response to decreased nitrogen inputs in grassland in southern England

Biomass production and plant species diversity in grassland in southern England was monitored before and after a change from conventional to organic farming. Our 18-year study, part of the UK's Environmental Change Network long-term monitoring programme, showed that the cessation of artificial fertiliser use on grassland after conversion to organic farming resulted in a decrease in biomass production and an increase in plant species richness. Grassland productivity decreased immediately after fertiliser application ceased, and after two years the annual total biomass production had fallen by over 50%. In the subsequent decade, total annual grassland productivity did not change significantly, and yields reached 31–66% of the levels recorded pre-management change. Plant species richness that had remained stable during the first 5 years of our study under conventional farming, increased by 300% over the following 13 years under organic farm management. We suggest that the change in productivity is due to the altered composition of species within the plots. In the first few years after the change in farming practice, high yielding, nitrogen-loving plants were outcompeted by lower yielding grasses and forbs, and these species remained in the plots in the following years. This study shows that grassland can be converted from an environment lacking in plant species diversity to a relatively species-rich pasture within 10–15 years, simply by stopping or suspending nitrogen additions. We demonstrate that the trade-off for increasing species richness is a decrease in productivity. Grassland in the UK is often not only managed from a conservation perspective, but to also produce a profitable yield. By considering the species composition and encouraging specific beneficial species such as legumes, it may be possible to improve biomass productivity and reduce the trade-off.     

The spatial pattern in a natural population of goldenrod (Solidago altissima L.), with particular reference to its change during the shoot growth

In a natural population of Solidago altissima L., the changes in the spatial pattern of shoots in the course of growth were studied. The results obtained were summarized as follows:

1. The spatial pattern changed from clumped to random distribution as plants grew. The change seemed to be resulted from some density-dependent process acting at a small spatial scale, probably the competition for space.
2. Large plants tended to distribute themselves more uniformly over the space than the small ones but at the mature stage of growth such a difference was not obviously recognized. The process of appearance of the small-sized plants during successive periods also seemed to be dependent on local density.
3. Large plants at the early stage of growth tended to survive better, and there was a positive correlation between initial size and the size at maturity.
4. From these results, it is inferred that the change of spatial pattern from clumped to random distribution is largely due to the elimination of small shoots as the result of competition for space among individual shoots.

     

Elevated CO2 and drought alter tissue water relations of birch (Betula populifolia Marsh.) seedlings

The effect of increasing atmospheric CO₂ concentrations on tissue water relations was examined in Betula populifolia, a common pioneer tree species of the northeastern U.S. deciduous forests. Components of tissue water relations were estimated from pressure volume curves of tree seedlings grown in either ambient (350 l l^–1) or elevated CO₂ (700 l l^–1), and both mesic and xeric water regimes. Both CO₂ and water treatment had significant effects on osmotic potential at full hydration, apoplasmic fractions, and tissue elastic moduli. Under xeric conditions and ambient CO₂ concentrations, plants showed a decrease in osmotic potentials of 0.15 MPa and an increase in tissue elastic moduli at full hydration of 1.5 MPa. The decrease in elasticity may enable plants to improve the soil-plant water potential gradient given a small change in water content, while lower osmotic potentials shift the zero turgor loss point to lower water potentials. Under elevated CO₂, plants in xeric conditions had osmotic potentials 0.2 MPa lower than mesic plants and decreased elastic moduli at full hydration. The increase in tissue elasticity at elevated CO₂ enabled the xeric plants to maintain positive turgor pressures at lower water potentials and tissue water contents. Surprisingly, the elevated CO₂ plants under mesic conditions had the most inelastic tissues. We propose that this inelasticity may enable plants to generate a favorable water potential gradient from the soil to the plant despite the low stomatal conductances observed under elevated CO₂ conditions.     

成人胫骨平台骨折的流行病学特征及其变化趋势的回顾性研究

摘要 目的：回顾性研究成人胫骨平台骨折的流行病学特征及其变化趋势。方法：以我院2014年1月至2019年12月期间收治的1193例成人胫骨平台骨折患者为调查研究对象,根据患者收治的时间将患者分为A组(2014年1月~2015年12月收治,n=369)、B组(2016年1月~2017年12月收治,n=394)、C组(2018年1月~2019年12月收治,n=430)。对三组患者进行统一的问卷调查,并对三组患者的年龄、职业、致伤原因、骨折分型进行归纳统计,分析探讨成人胫骨平台骨折的流行病学特征及其变化趋势。结果：2014年~2019年成人胫骨平台骨折总体流行病学特征：男性患者数量多于女性患者,年龄主要在40~59岁,以从事体力劳动患者居多,骨折致伤原因中主要以交通事故和室内活动跌倒损伤为主,骨折Schatzker分型中以II型、IV型为主。三组年龄对比有差异性,年龄有逐年升高的趋势(P<0.05)。三组性别比例有显著性差异,男女性别比例差异在逐年缩小(P<0.05)。三组患者在职业类型方面也有显著性差异（P<0.05）,但均以体力劳动者居多。在致伤原因中,A组患者以交通事故致伤为主,C组患者以室内活动跌倒损伤为主,组间对比有显著差异(P<0.05)。在骨折分型中,A组以IV型为主,C组以II型为主(P<0.05)。结论：2014年至2019年成人胫骨平台骨折中男性较多,年龄以40~59岁为主,体力劳动者为高发职业,交通事故和室内活动跌倒损伤是最常见的致伤原因,好发骨折分型为Schatzker II型、IV型。变化趋势表现为骨折发病人数逐年上升,发病年龄有老龄化趋势,致伤原因和骨折分型也在逐渐变化。     

Research Symposium—Aberdeen

ABSTRACT

Background: Climate change may increase the risk of biological invasions. However, current knowledge of this interaction is limited.

Aims: We aimed to quantify (1) the effect of climate change on the potential distribution of invasive plant species in Spain, (2) the importance of the area of origin of such species and (3) the vulnerability of different biogeographic provinces to future changes in climatic suitability for invaders.

Methods: We applied six methods of species distribution modelling to assess the variation of climatically suitable areas for 40 alien plants. We developed a Potential Area Change Index and used it as the response variable in modelling for three future emissions scenarios and three global circulation models over three time periods. The area of origin and biogeographic province in Spain were also considered.

Results: We found a highly specific response for each plant species rather than a clear trend for the entire set of species. Predicted climate suitability increased over higher emission scenarios and longer projected time lags. Neotropical species showed the greatest potential climatic range expansion. We detected a strong interaction between the geographic origin of a species and the biogeographic province.

Conclusions: Special attention should be given to the areas where aridification of climate is projected and where introduced neotropical species are likely to expand their range. Future work should develop accurate species-specific approaches that allow the management invasive plant species.     

The role of forest residues in the accounting for the global warming potential of bioenergy

Bioenergy makes up a significant portion of the global primary energy pie, and its production from modernized technology is foreseen to substantially increase. The climate neutrality of biogenic CO₂ emissions from bioenergy grown from sustainably managed biomass resource pools has recently been questioned. The temporary change caused in atmospheric CO₂ concentration from biogenic carbon fluxes was found to be largely dependent on the length of biomass rotation period. In this work, we also show the importance of accounting for the unutilized biomass that is left to decompose in the resource pool and how the characterization factor for the climate impact of biogenic CO₂ emissions changes whether residues are removed for bioenergy or not. With the case of Norwegian Spruce biomass grown in Norway, we found that significantly more biogenic CO₂ emissions should be accounted towards contributing to global warming potential when residues are left in the forest. For a 100‐year time horizon, the global warming potential bio factors suggest that between 44 and 62% of carbon‐flux, neutral biogenic CO₂ emissions at the energy conversion plant should be attributed to causing equivalent climate change potential as fossil‐based CO₂ emissions. For a given forest residue extraction scenario, the same factor should be applied to the combustion of any combination of stem and forest residues. Life cycle analysis practitioners should take these impacts into account and similar region/species specific factors should be developed.     

首发缺血性脑卒中患者血清Hcy和EPO水平的变化及临床意义

目的:探究首发缺血性脑卒中患者血清同型半胱氨酸(Hcy)和红细胞生成素(EPO)水平的变化和意义。方法:于2013年10月-2015年4月我科收治的首发缺血性脑卒中患者中随机选取98例作为观察组,另选取同期健康体检者98例作为对照组,检测患者的血小板、血浆纤维蛋白原(Fib)以及血白细胞水平,比较两组血清Hcy、EPO、血小板、Fib及血白细胞水平,使用Logistic回归分析法评价缺血性脑卒中病发的危险因素,采用Spearman法对血清Hcy与EPO间相关性进行分析。结果:观察组的Hcy(23.52±12.15)m IU/L与EPO(34.61±11.25)m IU/L水平显著高于对照组的(10.57±2.18)m IU/L、(17.54±5.83)m IU/L;观察组血小板、血浆纤维蛋白原(fibrinogen,Fib)及血白细胞水平均高于对照组;差异均有统计学意义(均P0.05)。经Logistic回归分析法分析可知,Hcy为缺血性脑卒中病发的独立因素,经Spearman相关性分析显示,首发缺血性脑卒中患者EPO水平与Hcy呈正相关。结论:缺血性脑卒中病发与血清Hcy和EPO水平升高密切相关,且Hcy是导致缺血性脑卒中病发的高危因素。     

尿液作为新型生物标志物来源的探索

机体各种变化是生物标志物研究的核心内容.因为机体固有的稳态调控机制,在血液中早期产生的变化容易被清除.而在尿液中不存在稳态调控机制,允许容纳更多的变化因素存在.尤其在疾病发生的早期阶段,从尿液中更有可能发现新型的早期生物标志物.在尿液生物标志物研究中,亦应当考虑药物的影响.使用尿液生物标志物研究路线图,能够有效规避各种影响因素对于尿液生物标志物研究的干扰;同时,结合膜处理新技术,有利于经济、高效地大规模收集尿液样本,促进尿液生物标志物的大规模研究.另外,本文介绍了最容易在尿液中体现出变化的肾脏疾病生物标志物的研究进展.尿液生物标志物的研究,将赋予人类在疾病预防、诊断、治疗及预后监测等诸多方面实现更多进步的可能性.     

Influence of age on the bioaccumulation of heavy metals in Apodemus sylvaticus at Merja Zerga lagoon,Morocco

The influence of age and sex on the bioaccumulation of heavy metals in Apodemus sylvaticus was studied in Merja Zerga lagoon in northern Morocco. Five trace metal elements (Zn, Pb, Cr, Cu and Fe) were quantitatively analyzed by Varian AA 240 atomic absorption spectroscopy with graphite furnace in three organs (Liver, Kidney and Heart) from animals of different age and sex. The maximum metal level of the analyzed samples was recorded in adults and was limited to 46.62 μg/g for Pb and 35.1 μg/g for Cu, while it reached 22.69 μg/g, 7.59 μg/g and 6.78 μg/g for Cr, Zn and Fe, respectively. Highly significant differences were found for bioaccumulation of heavy metals according to animal ages and no significant differences were observed between the two sexes among the studied animals. Our results revealed also the existence of a strong correlation (r > 0.65) between the majority of biometric parameters and the trace element concentrations. In general, we found that age is a critical factor in estimating the level of heavy metal pollution. Other characteristics such as habitat, feeding habits and anti-predator behavior of the species need to be studied.