Browsing lawns? Responses of Acacia nigrescens to ungulate browsing in an African savanna

We measured browsing-induced responses of Acacia trees to investigate "browsing lawns" as an analogy to grazing lawns in a semiarid eutrophic African savanna. During the two-year field study, we measured plant tolerance, resistance, and phenological traits, while comparing variation in leaf nitrogen and specific leaf area (SLA) across stands of Acacia nigrescens, Miller, that had experienced markedly different histories of attack from large herbivores. Trees in heavily browsed stands developed (1) tolerance traits such as high regrowth abilities in shoots and leaves, high annual branch growth rates, extensive tree branching and evidence of internal N translocation, and (2) resistance traits such as close thorn spacing. However, phenological "escape" responses were weak even in heavily browsed stands. Overall, browsing strongly affected plant morpho-functional traits and decreased both the number of trees carrying pods and the number of pods per tree in heavily browsed stands. Hence, there is experimental evidence that tolerance and resistance traits may occur simultaneously at heavily browsed sites, but this comes at the expense of reproductive success. Such tolerance and resistance traits may coexist if browsers trigger and maintain a positive feedback loop in which trees are continually investing in regrowth (tolerance), and if the plant's physical defenses (resistance) are not nutritionally costly and are long-lived. Our results confirm that chronic browsing by ungulates can maintain A. nigrescens trees in a hedged state that is analogous to a grazing lawn. Further research is needed to fully understand the long-term effects of chronic browsing on reproduction within such tree populations, as well as the overall effects on nutrient cycling at the ecosystem level.     

中国部分城市污泥中矿质元素形态与生物可利用性研究

近年来随着城市污水处理厂数目迅速增加,低成本、高效率的污泥农用受到越来越多的关注。研究从北到南的五家污水处理厂消化污泥中矿质元素的含量和形态分布,为污泥资源化的合理利用提供科学参考。结果表明：消化污泥总体呈高有机质、高氮磷、低K、高矿质元素营养的相似性,但其理化性质如阳离子交换容量(CEC)、pH等差异较大,对矿质元素的形态分布与生物可利用性有明显的影响。同种元素在不同污泥中含量的差异较大,相差数倍,甚至十倍以上。污泥中不同元素含量明显不同,Fe的浓度最高,次之是Mg、Zn、B的浓度最低。连续提取研究表明,污泥pH对污泥中矿质元素的形态分布有明显影响,酸性污泥(厦门污水处理厂)中各矿质元素酸溶／交换态百分率明显高于其他污泥。Cu主要分布在氧化态;Zn的三态分布百分率均在10％以上;Mg、Mn的酸溶／交换态含量较高;Fe主要分布在残渣态;B氧化态和还原态的百分率较高。建议在全国范围内进行一次污水处理厂污泥品质调查,为污泥合理农用提供科学依据。     

Assembling plant diversity mitigates greenhouse gas emissions and achieves high nitrogen removal when treating the low-C/N wastewater by constructed wetlands

Environmental Science and Pollution Research - The low carbon-to-nitrogen (C/N) ratio in wastewater will inhibit pollutant removal, and more seriously, it will cause an increment of nitrous oxide...     

Effect of plant-based carbon source supplements on denitrification of synthetic wastewater: focus on the microbiology

Environmental Science and Pollution Research - The effects of plant-based carbon source addition on wastewater NO3?-N removal and the involved microorganisms, especially denitrifying...     

Impacts of leachate of landfill on the groundwater hydrochemistry and size distributions and heavy metal components of colloids: a case study in NE China

Environmental Science and Pollution Research - Colloids associated with heavy metals are ubiquitous in contaminated groundwater; waste accumulation at imperfectly sealed landfills can produce large...     

Application of biochar in advanced oxidation processes: supportive,adsorptive, and catalytic role

Environmental Science and Pollution Research - The advanced oxidation processes (AOPs), especially sulphate radical (SO4•−)–based AOPs (SR-AOPs), have been considered more...     

Pyrolysis characteristics of cathode from spent lithium-ion batteries using advanced TG-FTIR-GC/MS analysis

Environmental Science and Pollution Research - Thermal treatment offers an alternative method for the separation of Al foil and cathode materials during spent lithium-ion batteries (LIBs)...     

考虑受灾点需求时间窗的应急物资配送车辆路径规划研究

为解决灾后应急物资亟待配送到灾区的现实问题,提高应急物资配送效率,考虑灾区对应急物资的需求紧迫程度的差异,建立软硬时间窗综合约束情况下以应急物资配送的总延迟时间最短、软时间窗的惩罚成本最小、硬时间窗的不满足个数最少为目标的应急物资车辆配送路径方案生成模型。前期对路网数据预处理,形成配送中心到受灾点的多对多时间最短路径集合,后期根据目标和约束进行模型构建,并利用遗传算法求解。引入算例分析对模型的有效性进行验证。结果表明:该模型可综合考虑软硬时间窗的影响,形成高效的应急物资车辆路径配送方案,可对灾后整体的应急方案制定提供帮助,具有较好的可行性和现实意义。     

三维变分在PM2.5重污染数值模拟中的应用研究

为了探讨三维变分法(3DVAR)对成渝城市群冬季PM2.5重污染模拟的改善效果,采用3DVAR对成渝城市群2017年12月至2018年1月的空气质量数值模拟结果进行资料同化,对比评估嵌套网格空气质量预报模式(NAQPMS)原始数据与同化再分析数据的准确率,并分析成渝重污染特征。研究结果显示,3DVAR在PM2.5、PM10和NO2的同化实验中均取得较好的改善效果,成渝地区检验站点各污染物相关系数(r)的平均提升比例依次为44%、90%和332%,r改善的站点占检验站点总数的比例分别为98%、100%和82%;检验站点均方根误差(RMSE)的平均下降比例分别为15%、37%和31%,RMSE改善的站点占检验站点总数的比例为65%、98%和84%。与原始模拟结果相比,同化结果能够更准确地反映成渝地区冬季重污染期间的PM2.5和PM10空间分布特征。     

Study on turbulence characteristics and sensitivity of quadrant analysis to threshold level in Lake Taihu

Environmental Science and Pollution Research - The identification of coherent structures is very important in investigating the sediment transport mechanism and controlling the eutrophication in...