Loss of forb diversity in relation to nitrogen deposition in the UK: regional trends and potential controls

In this study we investigate the impact of nitrogen (N) deposition on the diversity of three different vegetation functional groups – forbs, grasses and mosses – using a field survey of acid grasslands across Great Britain. Our aim is to identify the vegetation types that are most vulnerable to enhanced N deposition, and to shed light on the mechanisms that may be driving N‐initiated species changes in the UK. Sixty‐eight randomly selected grasslands belonging to the UK National Vegetation Classification group U4 (Festuca ovina–Agrostis capillaris–Galium saxatile grassland) were studied along a gradient of atmospheric N deposition ranging from 6 to 36 kg N ha^?1 yr^?1. At each site, vegetation was surveyed and samples were taken from the topsoil and subsoil. Aboveground plant material was collected from three species: a forb, grass and moss. Both the species richness and cover of forbs declined strongly with increasing N deposition, from greater than eight species/20% cover per m² quadrat at low levels of N to fewer than two species/5% cover at the highest N deposition levels. Grasses showed a weak but significant decline in species richness, and a trend toward increasing cover with increasing N input. Mosses showed no trends in either species richness or cover. Most of the decline in plant species richness could be accounted for by the level of ammonium deposition. Soil KCl‐extractable ammonium concentration showed a significant positive correlation with N input, but there was no relationship between N deposition and extractable nitrate. In the soil O/A horizon, there was no relationship between N deposition and %N, and only a very weak positive relationship between the level of N deposition and the C : N ratio. Finally, in the vegetation, there was no relationship between N deposition and either shoot tissue N concentration or N : P ratio for any of the three reference species. Combining our regional survey with the results of published N‐addition experiments provides compelling evidence that there has been a significant decline in the species richness and cover of forbs across Great Britain, and that the primary cause is competition due to an increase in the cover of grasses in response to enhanced deposition of reactive N, primarily NH₄⁺.     

A global assessment of forest surface albedo and its relationships with climate and atmospheric nitrogen deposition

We present a global assessment of the relationships between the short‐wave surface albedo of forests, derived from the MODIS satellite instrument product at 0.5° spatial resolution, with simulated atmospheric nitrogen deposition rates (N_dep), and climatic variables (mean annual temperature T_m and total annual precipitation P), compiled at the same spatial resolution. The analysis was performed on the following five forest plant functional types (PFTs): evergreen needle‐leaf forests (ENF); evergreen broad‐leaf forests (EBF); deciduous needle‐leaf forests (DNF); deciduous broad‐leaf forests (DBF); and mixed‐forests (MF). Generalized additive models (GAMs) were applied in the exploratory analysis to assess the functional nature of short‐wave surface albedo relations to environmental variables. The analysis showed evident correlations of albedo with environmental predictors when data were pooled across PFTs: T_m and N_dep displayed a positive relationship with forest albedo, while a negative relationship was detected with P. These correlations are primarily due to surface albedo differences between conifer and broad‐leaf species, and different species geographical distributions. However, the analysis performed within individual PFTs, strengthened by attempts to select ‘pure’ pixels in terms of species composition, showed significant correlations with annual precipitation and nitrogen deposition, pointing toward the potential effect of environmental variables on forest surface albedo at the ecosystem level. Overall, our global assessment emphasizes the importance of elucidating the ecological mechanisms that link environmental conditions and forest canopy properties for an improved parameterization of surface albedo in climate models.     

Global response patterns of plant photosynthesis to nitrogen addition: A meta‐analysis

A mechanistic understanding of plant photosynthetic response is needed to reliably predict changes in terrestrial carbon (C) gain under conditions of chronically elevated atmospheric nitrogen (N) deposition. Here, using 2,683 observations from 240 journal articles, we conducted a global meta‐analysis to reveal effects of N addition on 14 photosynthesis‐related traits and affecting moderators. We found that across 320 terrestrial plant species, leaf N was enhanced comparably on mass basis (N_mass, +18.4%) and area basis (N_area, +14.3%), with no changes in specific leaf area or leaf mass per area. Total leaf area (TLA) was increased significantly, as indicated by the increases in total leaf biomass (+46.5%), leaf area per plant (+29.7%), and leaf area index (LAI, +24.4%). To a lesser extent than for TLA, N addition significantly enhanced leaf photosynthetic rate per area (A_area, +12.6%), stomatal conductance (g_s, +7.5%), and transpiration rate (E, +10.5%). The responses of A_area were positively related with that of g_s, with no changes in instantaneous water‐use efficiency and only slight increases in long‐term water‐use efficiency (+2.5%) inferred from ¹³C composition. The responses of traits depended on biological, experimental, and environmental moderators. As experimental duration and N load increased, the responses of LAI and A_area diminished while that of E increased significantly. The observed patterns of increases in both TLA and E indicate that N deposition will increase the amount of water used by plants. Taken together, N deposition will enhance gross photosynthetic C gain of the terrestrial plants while increasing their water loss to the atmosphere, but the effects on C gain might diminish over time and that on plant water use would be amplified if N deposition persists.     

Discrimination of geographical origin and adulteration of radix astragali using fourier transform infrared spectroscopy and chemometric methods

Introduction – Radix Astragali, one of most widely used and important traditional Chinese medicines, is cultivated in different geographical regions. Because of varying growing conditions, the qualities of Radix Astragali vary, which can give rise to differences in clinical therapy. Detecting adulteration is a routine requirement in pharmaceutical practice. Objective – To develop a simple and accurate approach to discriminate the geographical origin and potential adulteration of Radix Astragali, derived from the root of Astragalus membranaceus (Fischer) Bunge var. mongholicus (Bunge) Hsiao, using Fourier transform infrared (FT‐IR) spectroscopy and chemometric methods. Methodology – To obtain characteristic IR spectra for accurate discrimination, a one‐solvent extraction method was utilised following a novel evaluation method for selecting appropriate solvents. Samples of Radix Astragali from different geographical origins were discriminated using FT‐IR spectroscopy and discriminant partial least squares (DPLS) methods. FT‐IR spectroscopy combined with Mahalanobis distance was employed to detect adulteration of Radix Astragali. Results – In comparison with other solvents, butanone was more effective at extracting samples. Radix Astragali samples were accurately assigned to their corresponding geographical origins by using FT‐IR spectroscopy and DPLS method. Most adulterated samples were detected accurately by application of FT‐IR spectroscopy combined with Mahalanobis distance. Conclusion – FT‐IR spectroscopy combined with chemometric method was developed and demonstrated to be a useful tool to discriminate geographical origin and adulteration of Radix Astragali. Copyright © 2010 John Wiley & Sons, Ltd.     

Fourier‐transform infrared spectroscopy study of dehydrated lipases from Candida antarctica B and Pseudomonas cepacia

Fourier‐transform infrared (FT‐IR) spectroscopy was employed to investigate potential lyophilization‐induced changes in the secondary structure of lipases from Candida antarctica B and Pseudomonas cepacia. The secondary structure elements were determined by curve fitting of the amide III bands of the two lipases in the lyophilized state in KBr pellets and in solution. It was found that lyophilization decreased the α‐helix and increased the β‐sheet content. However, FT‐IR analysis of crosslinked enzyme crystals of Pseudomonas cepacia lipase also indicated an increase in the β‐sheet content, which appears despite the fact that the enzyme, being in the crystallized state, should possess native conformation. This result partially questions the suitability of FT‐IR for analysis of the structure of solid proteins, at least as far as the β‐sheet content is concerned, because it is possible that the method overestimates the β‐sheets by measuring other hydrogen‐bonded nonperiodic intermolecular structures. No significant modification was observed when lipase from Pseudomonas cepacia was lyophilized in the presence of methoxypoly(ethylene glycol). © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 545–551, 1999.     

Dust accumulation due to anthropogenic impact induces anatomical and photochemical changes in leaves of Centranthus ruber growing on the slope of the Vesuvius volcano

• In Mediterranean ecosystems, some natural areas are exposed to severe anthropogenic impact. Especially in summer, the considerable number of tourists visiting such areas, often with vehicles, causes deposition of dust over the vegetation due to formation of powder clouds, also favoured by wind erosion, high temperature, low precipitation and incoherent soil structure. The main aim of this study was to analyse whether the deposition of dust can induce changes in leaf anatomical functional traits and in the efficiency of photosynthetic apparatus in Centranthus ruber, a species widespread in Mediterranean ecosystems.
• Leaf morpho‐functional traits were quantified in plants growing at sites characterised by high (HD) and low (LD) dust deposition, in periods with high anthropogenic impact. Analyses included quantification of chlorophyll fluorescence emission parameters, photosynthetic pigment concentration as well as stomatal size and frequency, leaf lamina thickness, quantification of intercellular spaces and phenolics in the mesophyll through microscopy.
• The overall analysis suggested that the different conditions of dust deposition induced different adjustment of morpho‐functional traits in leaves of C. ruber. High dust deposition shielded the leaf lamina, protecting the photosynthetic apparatus from excess light and favoured plant photochemical efficiency. Leaves exposed to low dust deposition showed higher accumulation of phenolic compounds, protecting chloroplast membranes and characterised by high thermal dissipation of excess light.
• Such adaptive phenomena can affect vegetation dynamics due to possible different species‐specific plant responses, resulting in different plant competitiveness under the limiting conditions of Mediterranean environments.

     

A comparison of techniques for studying oogenesis in the European eel Anguilla anguilla

A multi‐technique approach was used to study the changes occurring in European eel Anguilla anguilla ovaries during hormonally‐induced vitellogenesis. Aside from classic techniques used to monitor the vitellogenic process, such as ovary histology, fat content analysis, sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and vitellogenin enzyme linked immunosorbent assay (ELISA), a new technique, Fourier‐transform infrared (FT‐IR) microspectroscopy, was used to analyse A. anguilla ovaries. The results from the different techniques provided different ways of approaching the same process. Although it is considered a time consuming approach, of all the employed techniques, histology provided the most direct evidences about vitellogenesis. SDS–PAGE and ELISA were also useful for studying vitellogenesis, whereas fat analysis cannot be used for this purpose. The FT‐IR analysis provided a representative IR spectrum for each ovarian stage (previtellogenic stage, early vitellogenic stage, mid‐vitellogenic stage and late vitellogenic stage), demonstrating that it is a valid method able to illustrate the distribution of the oocytes within the ovary slices. The chemical maps obtained confirmed changes in lipid concentrations and revealed their distribution within the oocytes at different maturational stages. When the results and the accuracy of the FT‐IR analysis were compared with those of the traditional techniques commonly used to establish the vitellogenic stage, it became evident that FT‐IR is a useful and reliable tool, with many advantages, including the fact that it requires little biological material, the costs involved are low, analysis times are short and last but not least, the fact that it offers the possibility of simultaneously analysing various biocomponents of the same oocyte.     

Phytochemical Findings Evidencing Botanical Origin of New Propolis Type from North‐West Argentina

Propolis samples from north‐west Argentina (Amaicha del Valle, Tucumán) were evaluated by palynology, FT‐IR spectra, and RP‐HPTLC. In addition, the volatile fraction was studied by HS‐SPME‐GC/MS. The botanical species most visited by Apis mellifera L. near the apiaries were collected and their RP‐HPTLC extracts profiles were compared with propolis samples. In addition, GC/MS was performed for volatile compounds from Zuccagnia punctata Cav. (Fabaceae). FT‐IR spectra and RP‐HPTLC fingerprints of propolis samples showed similar profiles. In RP‐HPTLC analyses, only Z. punctata presented a similar fingerprint to Amaicha propolis. The major volatile compounds present in both were trans‐linalool oxide (furanoid), 6‐camphenone, linalool, trans‐pinocarveol, p‐cymen‐8‐ol, and 2,3,6‐trimethylbenzaldehyde. Potential variations for the Amaicha del Valle propolis volatile fraction as consequence of propolis sample preparation were demonstrated.     

滇中亚高山地带性植被凋落物分解对模拟氮沉降的响应

模拟氮（N）沉降对凋落物分解特征的影响对研究森林生态系统物质循环响应大气N沉降的内在机理和应对N沉降全球化具有重要意义。从2018年2月至2019年1月,对滇中亚高山常绿阔叶林（Evergreen broad-leaf forest）和高山栎林（Quercus semecarpifolia forest）两种地带性植被进行模拟N沉降试验,利用尼龙网袋法对两种林型凋落叶和凋落枝进行原位分解试验,N沉降处理水平分别为对照CK（Control check,0 g N m^-2 a^-1）、低氮LN（Low nitrogen,5 g N m^-2 a^-1）、中氮MN（Medium nitrogen,15 g N m^-2 a^-1）和高氮HN（High nitrogen,30 g N m^-2 a^-1）。结果表明：常绿阔叶林凋落叶和凋落枝分解率分别为44.84%和21.96%,均高于高山栎林的35.97%（凋落叶）和17.51%（凋落枝）;N沉降处理使得常绿阔叶林和高山栎林的凋落叶和凋落枝质量损失95%的时间在对照（CK）的基础上均有一定程度的增加,其中以HN处理下最为显著;经过1年的分解,两种林型凋落叶、枝纤维素和木质素降解均受到N沉降的抑制作用;两种林型中凋落物质量残留率、纤维素和木质素残留率三者间呈极显著正相关。针对滇中亚高山区域范围内的两种地带性植被,凋落物分解对N沉降的响应方向主要取决于凋落物基质质量,其中尤以纤维素和木质素为重要影响因素。     

Changes in plant taxonomic and functional diversity patterns following treeline advances in the South Urals

Background: Treeline ecotones represent environmental boundaries that fluctuate in space and time and thus induce changes in plant taxonomic and functional diversity.

Aims: To study changes through time in taxonomic and functional plant diversity patterns along the treeline ecotone.

Methods: In 2002, vegetation was sampled along a gradient from upper montane forest to the treeline–alpine transition in the South Ural Mountains, Russia. In 2014, vegetation was resampled and plant functional traits were collected. We studied spatial and temporal changes in plant species composition, functional composition and functional diversity.

Results: Species composition and diversity changed along the elevational gradient. The functional composition in height, leaf area, specific leaf area and leaf nitrogen content decreased with elevation, whereas functional composition of leaf carbon content increased. We found a temporal shift towards shorter plants with smaller leaves in treeline sites. Functional richness varied in several traits along the elevational gradient, while functional dispersion showed a trend towards increased functional dispersion in height, specific leaf area and leaf nitrogen in the treeline–tundra transition.

Conclusions: Tree encroachment across the treeline ecotone has resulted in a shift in plant species relative abundances and functional diversity, possibly affecting plant community assembly patterns.     

Attribution of seasonal leaf area index trends in the northern latitudes with “optimally” integrated ecosystem models

Significant increases in remotely sensed vegetation indices in the northern latitudes since the 1980s have been detected and attributed at annual and growing season scales. However, we presently lack a systematic understanding of how vegetation responds to asymmetric seasonal environmental changes. In this study, we first investigated trends in the seasonal mean leaf area index (LAI) at northern latitudes (north of 30°N) between 1982 and 2009 using three remotely sensed long‐term LAI data sets. The most significant LAI increases occurred in summer (0.009 m² m^?2 year^?1, p < .01), followed by autumn (0.005 m² m^?2 year^?1, p < .01) and spring (0.003 m² m^?2 year^?1, p < .01). We then quantified the contribution of elevating atmospheric CO₂ concentration (eCO₂), climate change, nitrogen deposition, and land cover change to seasonal LAI increases based on factorial simulations from 10 state‐of‐the‐art ecosystem models. Unlike previous studies that used multimodel ensemble mean (MME), we used the Bayesian model averaging (BMA) to optimize the integration of model ensemble. The optimally integrated ensemble LAI changes are significantly closer to the observed seasonal LAI changes than the traditional MME results. The BMA factorial simulations suggest that eCO₂ provides the greatest contribution to increasing LAI trends in all seasons (0.003–0.007 m² m^?2 year^?1), and is the main factor driving asymmetric seasonal LAI trends. Climate change controls the spatial pattern of seasonal LAI trends and dominates the increase in seasonal LAI in the northern high latitudes. The effects of nitrogen deposition and land use change are relatively small in all seasons (around 0.0002 m² m^?2 year^?1 and 0.0001–0.001 m² m^?2 year^?1, respectively). Our analysis of the seasonal LAI responses to the interactions between seasonal changes in environmental factors offers a new perspective on the response of global vegetation to environmental changes.     

内蒙古高原湖滨湿地优势植物功能性状特征及其适应性

受人类活动和气候变化的影响,湖泊湖滨带退化速度显著加快。植物功能性状的方法可以量化植物特征,预测植物对外界环境干扰的反应,有助于理解退化湖滨带湿地植物应对环境变化所表现出的适应机制,对湖泊湖滨湿地生态系统植被的恢复与重建具有重要意义。在内蒙古高原典型湖泊湖滨湿地选取芦苇（Phragmites australis）、赖草（Leymus secalinus）、毛茛（Ranunculus japonicus）、鹅绒委陵菜（Potentilla anserina）、碱蓬（Suaeda glauca）、盐角草（Salicornia europaea）和拂子茅（Calamagrostis epigeios）7种优势植物的叶片和根系作为研究对象,对不同湿地植物的11种功能性状变化规律及其与环境因子的关系进行研究。旨在探究环境变化影响下湖滨带湿地植物的物种分布和功能性状的差异,以及湿地植物在不同湖滨带湿地生境下的适应策略。在评估植物功能性状差异基础上,采用环境矩阵连接性状矩阵（RLQ）结合第四角分析（Fourth-Corner）的方法分析环境因子对植物功能性状的影响。结果表明,内蒙古湖滨带湿地中7种优势植物为了适应不同的环境的影响,植物的功能性状均产生不同程度的种间与种内变异,在湖滨带湿地中植物的植株高度、叶片碳含量、叶片氮含量、叶片碳氮比、比根长、根组织密度、根氮含量对环境变化的响应比较敏感,土壤pH与叶片干物质含量呈显著负相关;土壤盐分与植株高度、叶片碳含量和叶碳氮比显著负相关,与叶片氮含量、根组织密度显著正相关;土壤的总氮含量与植株高度显著正相关,与比根长显著负相关;土壤碳氮比与植株高度和叶片碳含量显著负相关,与植物比根长显著正相关;土壤容重与根氮含量显著负相关。研究表明内蒙古高原湖滨带湿地植物的功能性状受环境的作用强烈,植物采取了不同的性状策略来适应环境。     

模拟氮沉降和降雨对华西雨屏区常绿阔叶林凋落物分解的影响

从2013年11月至2015年5月,采用凋落物分解袋法,设置了对照(CK)、氮沉降(N)、减雨(R)、增雨(A)、氮沉降+减雨(NR)、氮沉降+增雨(NA)6个处理水平,研究了模拟氮沉降和降雨对华西雨屏区常绿阔叶林凋落物分解的影响。结果表明:华西雨屏区常绿阔叶林凋落叶分解较快,凋落枝分解较慢;凋落物夏季分解较快,其他季节分解较慢。经过18个月的分解后,凋落叶和枝的质量残留率分别为45.86%和86.67%,凋落叶分解50%需要的时间为1.42 a,比枝短6.19 a。各处理凋落物叶分解系数表现为:k(A)k(CK)k(NA)k(N)k(R)k(NR),凋落枝质量残留率表现为:NNRRNACKA。模拟氮沉降、减雨和增雨处理凋落叶分解50%分别需要1.79、1.94a和1.36a,凋落枝分解50%分别需要8.84、8.63 a和6.47 a。各处理凋落叶分解95%需要5.37—11.33 a,凋落枝分解95%需要27.41—33.84 a。同一氮沉降条件下,增雨处理促进凋落叶分解,减雨处理抑制凋落叶分解;同一降雨条件下,氮沉降抑制凋落叶分解。氮沉降或降雨对凋落物的分解产生显著影响(P0.05),其交互作用影响不显著(P0.05)。可见,在氮沉降持续增加和降雨格局改变的背景下,增雨促进了华西雨屏区天然常绿阔叶林凋落物的分解,氮沉降和减雨抑制了凋落物的分解,模拟氮沉降和降雨对凋落物的分解交互作用表现不明显。     

Incident radiation and the allocation of nitrogen within Arctic plant canopies: implications for predicting gross primary productivity

Arctic vegetation is characterized by high spatial variability in plant functional type (PFT) composition and gross primary productivity (P). Despite this variability, the two main drivers of P in sub‐Arctic tundra are leaf area index (L_T) and total foliar nitrogen (N_T). L_T and N_T have been shown to be tightly coupled across PFTs in sub‐Arctic tundra vegetation, which simplifies up‐scaling by allowing quantification of the main drivers of P from remotely sensed L_T. Our objective was to test the L_T–N_T relationship across multiple Arctic latitudes and to assess L_T as a predictor of P for the pan‐Arctic. Including PFT‐specific parameters in models of L_T–N_T coupling provided only incremental improvements in model fit, but significant improvements were gained from including site‐specific parameters. The degree of curvature in the L_T–N_T relationship, controlled by a fitted canopy nitrogen extinction co‐efficient, was negatively related to average levels of diffuse radiation at a site. This is consistent with theoretical predictions of more uniform vertical canopy N distributions under diffuse light conditions. Higher latitude sites had higher average leaf N content by mass (N_M), and we show for the first time that L_T–N_T coupling is achieved across latitudes via canopy‐scale trade‐offs between N_M and leaf mass per unit leaf area (L_M). Site‐specific parameters provided small but significant improvements in models of P based on L_T and moss cover. Our results suggest that differences in L_T–N_T coupling between sites could be used to improve pan‐Arctic models of P and we provide unique evidence that prevailing radiation conditions can significantly affect N allocation over regional scales.     

Changes in carotenoid content and distribution in living plant tissue can be observed and mapped in situ using NIR-FT-Raman spectroscopy

Near-infrared (NIR) excited Fourier transform (FT) Raman spectroscopy has been applied for in situ analysis of carotenoids in living plant samples. Pelargonium x hortorum leaf has been mapped using a Raman mapping technique to illustrate heterogeneous distribution of carotenoids. Mapping has also been employed for visualization of carotenoid changes induced by abiotic and biotic stress. In a tomato (Lycopersicon esculentum Mill.) fruit, inhibition of lycopene biosynthesis and accumulation of beta-carotene are demonstrated in tissue affected by sunscald physiological disorder. Raman map of diseased sugarbeet (Beta vulgaris L.) leaf shows a local carotenoid decline at infection site while the carotenoid accumulation is evident in parsley (Petroselinum crispum Mill. Nym.) as a response to Septoria petroselini infestation. Additionally, occurrence of lutein, beta-carotene and capsanthin, and changes in their relative content during bell pepper (Capsicum annum L.) fruit ripening are described by single Raman spectra. Based on these examples, the potential application of NIR-FT-Raman spectroscopy for a non-destructive analysis of carotenoids in various living plant tissues of the size ranging from about 0.01 mm² to 35 cm² is discussed.     

Can atmospheric input of nitrogen affect seed bank dynamics in habitats of conservation interest? The case of dune slacks

Questions: Does the increased atmospheric deposition of nitrogen, which can have major effects on the established vegetation of nutrient‐poor habitats, also impact germination from the soil seed bank? Location: Coastal dune slacks at Newborough Warren, Wales, UK. Methods: The effects of nitrogen addition (15 kg.ha^‐1.a^‐1) on seed germination from the soil seed bank were investigated using the seedling emergence method between September 2004 and February 2005. Results: More seedlings emerged from fertilised samples than unfertilised controls. Most species showed enhanced germination after fertilisation with nitrogen, with seedling numbers statistically significantly greater in nitrogen addition samples in a quarter of species abundant enough for analysis. Species that responded positively to fertilisation were species with low Ellenberg indicator values indicative of infertile sites. Conclusions: Most species showed increased germination after fertilisation with nitrogen, including early successional species normally growing in nutrient‐poor conditions. This suggests that the increased atmospheric deposition of nitrogen probably not only impacts on established vegetation, but also has the potential to alter seed bank dynamics.     

Forest floor vegetation response to nitrogen deposition in Europe

Chronic nitrogen (N) deposition is a threat to biodiversity that results from the eutrophication of ecosystems. We studied long‐term monitoring data from 28 forest sites with a total of 1,335 permanent forest floor vegetation plots from northern Fennoscandia to southern Italy to analyse temporal trends in vascular plant species cover and diversity. We found that the cover of plant species which prefer nutrient‐poor soils (oligotrophic species) decreased the more the measured N deposition exceeded the empirical critical load (CL) for eutrophication effects (P = 0.002). Although species preferring nutrient‐rich sites (eutrophic species) did not experience a significantly increase in cover (P = 0.440), in comparison to oligotrophic species they had a marginally higher proportion among new occurring species (P = 0.091). The observed gradual replacement of oligotrophic species by eutrophic species as a response to N deposition seems to be a general pattern, as it was consistent on the European scale. Contrary to species cover changes, neither the decrease in species richness nor of homogeneity correlated with nitrogen CL exceedance (ExCL_empN). We assume that the lack of diversity changes resulted from the restricted time period of our observations. Although existing habitat‐specific empirical CL still hold some uncertainty, we exemplify that they are useful indicators for the sensitivity of forest floor vegetation to N deposition.     

Rehabilitation of a Bauxite Tailing Substrate in Central Amazonia: The Effect of Litter and Seed Addition on Flood‐Prone Forest Restoration

Impacts of mining activity can be particularly difficult to remediate in wetland ecosystems subject to inundation pulses due to the reduced length of the plant growing season. We used a factorial experiment to test whether litter and seed addition could be used to increase the efficiency of ecological restoration on a flood‐prone forest (known as igapó) impacted by deposition of bauxite tailings. Our results clearly showed that the addition of litter collected from pristine igapó areas increased plant growth, seedling density, and seedling species richness. The increase in individual plant growth was echoed at the community level with higher leaf area index values on litter addition plots compared to controls. Litter addition can enhance reaccumulation of nutrient pools during successional development, which has been proposed as an important feature to ensure self‐sustainability of areas under restoration. The success of the seed addition treatment depended on the species used. Of the seven sown species, only Acosmium nitens (a leguminous nitrogen‐fixing species) showed high establishment. The introduction of nitrogen‐fixing species is also expected to build up the nitrogen pool in the system as has been reported for restoration programs in non‐inundated forests. These practices have the advantage, compared to direct fertilizing, of not causing eutrophication of water bodies when applied to flood‐prone vegetation.