Global change has accelerated local species extinctions and colonizations, often resulting in losses and gains of evolutionary lineages with unique features. Do these losses and gains occur randomly across the phylogeny? We quantified: temporal changes in plant phylogenetic diversity (PD); and the phylogenetic relatedness (PR) of lost and gained species in 2672 semi-permanent vegetation plots in European temperate forest understories resurveyed over an average period of 40 yr. Controlling for differences in species richness, PD increased slightly over time and across plots. Moreover, lost species within plots exhibited a higher degree of PR than gained species. This implies that gained species originated from a more diverse set of evolutionary lineages than lost species. Certain lineages also lost and gained more species than expected by chance, with Ericaceae, Fabaceae, and Orchidaceae experiencing losses and Amaranthaceae, Cyperaceae, and Rosaceae showing gains. Species losses and gains displayed no significant phylogenetic signal in response to changes in macroclimatic conditions and nitrogen deposition. As anthropogenic global change intensifies, temperate forest understories experience losses and gains in specific phylogenetic branches and ecological strategies, while the overall mean PD remains relatively stable.

El canvi global ha accelerat les extincions i colonitzacions a escala local, cosa que sovint ha suposat pèrdues i guanys de llinatges evolutius amb característiques singulars. Ara bé, aquestes pèrdues i guanys ocorren aleatòriament al llarg de la filogènia? En aquest estudi quantifiquem: els canvis temporals en la diversitat filogenètica de les plantes; i la relació filogenètica de les espècies perdudes i guanyades en 2.672 parcel·les de vegetació semi-permanent en sotaboscos temperats europeus i re-mostrejades durant un període mitjà de 40 anys. En controlar per les diferències en la riquesa d’espècies, la diversitat filogenètica va augmentar lleugerament amb el temps i entre parcel·les. A més, les espècies perdudes dins de les parcel·les presentaven un grau més alt de relació filogenètica que les espècies guanyades. Això implica que les espècies guanyades s’originaren en un conjunt de llinatges evolutius més diversos que les espècies perdudes. Certs llinatges també van perdre i van guanyar més espècies de les esperades aleatòriament: Ericaceae, Fabaceae i Orchidaceae van experimentar pèrdues i Amaranthaceae, Cyperaceae i Rosaceae van mostrar guanys. Les pèrdues i els guanys d’espècies no van mostrar cap senyal filogenètic significatiu en resposta als canvis en les condicions macro-climàtiques i la deposició de nitrogen. A mesura que s’intensifica el canvi global antropogènic, els sotaboscos temperats experimenten pèrdues i guanys en branques filogenètiques i estratègies ecològiques específiques, mentre que la diversitat filogenètica mitjana general roman relativament constant.

• Keywords
• biodiversity change, biogeography, forestREplot, global change, phylogeny, plant functional traits, time lag, vegetation resurvey,
• MeSH
• Biodiversity * MeSH
• Nitrogen * MeSH
• Phylogeny MeSH
• Climate Change MeSH
• Forests MeSH
• Plants MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen * MeSH

Plant communities are being exposed to changing environmental conditions all around the globe, leading to alterations in plant diversity, community composition, and ecosystem functioning. For herbaceous understorey communities in temperate forests, responses to global change are postulated to be complex, due to the presence of a tree layer that modulates understorey responses to external pressures such as climate change and changes in atmospheric nitrogen deposition rates. Multiple investigative approaches have been put forward as tools to detect, quantify and predict understorey responses to these global-change drivers, including, among others, distributed resurvey studies and manipulative experiments. These investigative approaches are generally designed and reported upon in isolation, while integration across investigative approaches is rarely considered. In this study, we integrate three investigative approaches (two complementary resurvey approaches and one experimental approach) to investigate how climate warming and changes in nitrogen deposition affect the functional composition of the understorey and how functional responses in the understorey are modulated by canopy disturbance, that is, changes in overstorey canopy openness over time. Our resurvey data reveal that most changes in understorey functional characteristics represent responses to changes in canopy openness with shifts in macroclimate temperature and aerial nitrogen deposition playing secondary roles. Contrary to expectations, we found little evidence that these drivers interact. In addition, experimental findings deviated from the observational findings, suggesting that the forces driving understorey change at the regional scale differ from those driving change at the forest floor (i.e., the experimental treatments). Our study demonstrates that different approaches need to be integrated to acquire a full picture of how understorey communities respond to global change.

• Keywords
• SLA, climate change, forest management, forestREplot, herbaceous layer, mesocosm experiment, nitrogen deposition, plant height, resurvey study,
• MeSH
• Nitrogen MeSH
• Ecosystem * MeSH
• Forests * MeSH
• Plants MeSH
• Trees MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen MeSH

Species turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller- by larger-ranged species across habitats. Communities shifted in parallel towards more nutrient-demanding species, with species from nutrient-rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller-ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community-scale turnover to macroecological processes such as biotic homogenisation.

• Keywords
• GLORIA, alpine, biodiversity change, forest, forestREplot, grassland, homogenization, resurvey, winner and loser species,
• MeSH
• Biodiversity * MeSH
• Ecosystem MeSH
• Forests MeSH
• Grassland * MeSH
• Plants MeSH
• Publication type
• Letter MeSH

Understorey communities can dominate forest plant diversity and strongly affect forest ecosystem structure and function. Understoreys often respond sensitively but inconsistently to drivers of ecological change, including nitrogen (N) deposition. Nitrogen deposition effects, reflected in the concept of critical loads, vary greatly not only among species and guilds, but also among forest types. Here, we characterize such context dependency as driven by differences in the amounts and forms of deposited N, cumulative deposition, the filtering of N by overstoreys, and available plant species pools. Nitrogen effects on understorey trajectories can also vary due to differences in surrounding landscape conditions; ambient browsing pressure; soils and geology; other environmental factors controlling plant growth; and, historical and current disturbance/management regimes. The number of these factors and their potentially complex interactions complicate our efforts to make simple predictions about how N deposition affects forest understoreys. We review the literature to examine evidence for context dependency in N deposition effects on forest understoreys. We also use data from 1814 European temperate forest plots to test the ability of multi-level models to characterize context-dependent understorey responses across sites that differ in levels of N deposition, community composition, local conditions and management history. This analysis demonstrated that historical management, and plot location on light and pH-fertility gradients, significantly affect how understorey communities respond to N deposition. We conclude that species' and communities' responses to N deposition, and thus the determination of critical loads, vary greatly depending on environmental contexts. This complicates our efforts to predict how N deposition will affect forest understoreys and thus how best to conserve and restore understorey biodiversity. To reduce uncertainty and incorporate context dependency in critical load setting, we should assemble data on underlying environmental conditions, conduct globally distributed field experiments, and analyse a wider range of habitat types.

• Keywords
• Biodiversity, Critical load, Herb layer, N deposition, forestREplot,
• MeSH
• Biodiversity MeSH
• Nitrogen analysis   MeSH
• Ecosystem MeSH
• Nitrogen Cycle MeSH
• Forests * MeSH
• Soil MeSH
• Plants MeSH
• Trees growth & development   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Nitrogen MeSH
• Soil MeSH

The contemporary state of functional traits and species richness in plant communities depends on legacy effects of past disturbances. Whether temporal responses of community properties to current environmental changes are altered by such legacies is, however, unknown. We expect global environmental changes to interact with land-use legacies given different community trajectories initiated by prior management, and subsequent responses to altered resources and conditions. We tested this expectation for species richness and functional traits using 1814 survey-resurvey plot pairs of understorey communities from 40 European temperate forest datasets, syntheses of management transitions since the year 1800, and a trait database. We also examined how plant community indicators of resources and conditions changed in response to management legacies and environmental change. Community trajectories were clearly influenced by interactions between management legacies from over 200 years ago and environmental change. Importantly, higher rates of nitrogen deposition led to increased species richness and plant height in forests managed less intensively in 1800 (i.e., high forests), and to decreases in forests with a more intensive historical management in 1800 (i.e., coppiced forests). There was evidence that these declines in community variables in formerly coppiced forests were ameliorated by increased rates of temperature change between surveys. Responses were generally apparent regardless of sites' contemporary management classifications, although sometimes the management transition itself, rather than historic or contemporary management types, better explained understorey responses. Main effects of environmental change were rare, although higher rates of precipitation change increased plant height, accompanied by increases in fertility indicator values. Analysis of indicator values suggested the importance of directly characterising resources and conditions to better understand legacy and environmental change effects. Accounting for legacies of past disturbance can reconcile contradictory literature results and appears crucial to anticipating future responses to global environmental change.

• Keywords
• biodiversity change, climate change, disturbance regime, forestREplot, herbaceous layer, management intensity, nitrogen deposition, plant functional traits, time lag, vegetation resurvey,
• MeSH
• Biodiversity * MeSH
• Nitrogen MeSH
• Forests MeSH
• Human Activities MeSH
• Climate MeSH
• Plants classification   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH
• Names of Substances
• Nitrogen MeSH

Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta-analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17-75 years between the two surveys) by assessing the importance of (i) coarse-resolution (i.e., among sites) vs. fine-resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local-scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among-site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse-resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine-resolution environmental conditions.

• Keywords
• Shannon diversity, atmospheric nitrogen deposition, evenness, forest management, forestREplot, game browsing, spatiotemporal resurvey data, species richness,
• MeSH
• Biodiversity * MeSH
• Herbivory * MeSH
• Time Factors MeSH
• Forestry * MeSH
• Forests * MeSH
• Climate * MeSH
• Air Pollution adverse effects   MeSH
• Publication type
• Journal Article MeSH
• Meta-Analysis MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH