Altitudinal Patterns of Native and Invasive Alien Herbs along Roadsides in the Dayao Mountain National Nature Reserve, Guangxi, China

Invasive alien plants have rapidly established and spread in nature reserves via roads and now pose a threat to biodiversity. To understand the mechanism and distribution patterns of invasive alien herbs, we compared the altitude patterns of native and invasive alien herbs based on 105 plots in the Dayao Mountain National Nature Reserve. This study also compared the distribution patterns of new (introduced to China after 1900) and old (introduced to China before 1900) invasive alien herbs. In addition, we examined the effects of climatic factors and human activities on the distribution patterns of species richness. In our study, 151 native herbs species and 18 invasive alien herbs species were observed, of which 12 were new invasive alien herbs. Old invasive alien herbs occurred more frequently and occupied a wider range of altitudes than new invasive alien herbs. The richness of native herbs tended to decrease with increasing altitude, and the altitude patterns of the richness of all invasive herbs and new invasive alien herbs were hump-shaped. Based on an analysis using the linear mixed model, the results indicated that temperature was the main factor limiting the altitude patterns of native herbs, and that temperature and human activities were essential factors in the distribution and spread of all invasive alien herbs and new invasive alien herbs. The intensity of human interference is a crucial driver of the spread of new invasive alien herbs to higher altitudes.

Assessment of Naturalness: The Response of Social Behavior Types of Plants to Anthropogenic Impact

The aims of this research are to assess the relationship between the concepts of hemeroby and naturalness of plant communities and to test the hypothesis about the ordinal nature of the response of social behavior types of plants under anthropogenic influence. Study area is the recreational zone of the Botanical Garden of Dnipro National University, named after Oles Gonchar, Dnipro City, Ukraine (48.43°N 35.05°E). Four polygons (105 relevés in each) were examined. Two polygons were in the zone after park reconstruction, and two were in the zone without reconstruction. The vegetation community ordination was performed using RLQ analysis. The Q-table was represented by eight dummy variables, which indicated social behavior types. The most important predictors of naturalness were aggressive alien species and invaders and weeds (positive dependence) and disturbance tolerants (negative dependence). The most important predictors of hemeroby were aggressive alien species (negative dependence) and ruderal competitors, invaders, and disturbance tolerants (positive dependence). Naturalness and hemeroby reflect different strategies for transforming a plant community and are not completely symmetrically opposed concepts. The response of a plant community is multivariate, so the naturalness metric based on the social behavior types is only able to distinguish well between the extreme states of a plant community, but is a poor measure for a more detailed assessment of naturalness.

Functional traits explain non-native plant species richness and occupancy on northern New Zealand islands

Plant functional traits can greatly influence invasion success on islands. However, interrelationships between traits and invasion success are rarely integrated with the island biogeography theory. Here, we explored relations between functional traits and plant distributions to assess which traits are associated with invasion success (i.e. high island occupancy), test whether non-native richness and seed mass of species with distinct growth forms and dispersal modes vary differently with island characteristics (e.g. area, isolation, exposure to ocean-borne disturbances, distance from the nearest urban area, and whether islands were managed for conservation), and whether results differ from native species. We assembled a database of 264 northern New Zealand offshore islands, amalgamating species lists from field surveys and previously published data, and comprising 822 native and 855 non-native species. Non-native graminoids occurred on islands more frequently than forbs and woody species, and long-distance dispersal modes (wind, animal, unspecialized) more than species with short-distance dispersal modes. Most differences among trait categories of non-native species were associated with human-related variables (i.e. distance from the nearest urban area, and whether islands were conservation areas). Non-native plant species with high island occupancy were less commonly associated with human-related variables than non-native species with low island occupancy. Instead, they were more similar in their distributional patterns to native species within the same trait category, suggesting comparable processes regulate both sets of species. Our results illustrate that integrating trait-based approaches in the island biogeography framework can be a useful tool in understanding and predicting plant invasions.

Estimating non-native plant richness with a species-accumulation model along roads

Monitoring non-native plant richness is important for biodiversity conservation and scientific research. The species-area model (SA model) has been used frequently to estimate the total species richness within a region. However, the conventional SA model may not provide robust estimations of non-native plant richness because the ecological processes associated with the accumulation of exotic and native plants may differ. Because roads strongly dictate the distributions of exotic plants, we propose a species-accumulation model along roads (SR model), rather than an SA model, to estimate the non-native plant richness within a region. Using 270 simulated data sets, we compared the differences in performance between the SR and SA models. A decision tree based on prediction accuracy was created to guide model application, which was validated using field data from 3 national nature reserves in 3 different provinces in China. The SR model significantly outperformed the SA model when non-native species were restricted to the roadsides and the proportion of uncommon exotic species was small. More importantly, the SR model accurately estimated the non-native plant richness in all field sites with an error of <1 species per site. We believe our new model meets the practical need to efficiently and robustly estimate non-native plant richness, which may facilitate effective biodiversity conservations and promote research on non-native plant invasion and vegetation dynamics.

Invasion windows for a global legume invader are revealed after joint examination of abiotic and biotic filters

Successful alien plant invasion is influenced by both climate change and plant-plant interactions. We estimate the single and interactive effects of competition and extreme weather events on the performance of the global legume invader Lupinus polyphyllus (Lindl.). In three experimental studies we assessed (i) the stress tolerance of seedling and adult L. polyphyllus plants against extreme weather events (drought, fluctuating precipitation, late frost), (ii) the competitive effects of L. polyphyllus on native grassland species and vice versa, and (iii) the interactive effects of extreme weather events and competition on the performance of L. polyphyllus. Drought reduced growth and led to early senescence of L. polyphyllus but did not reduce adult survival. Fluctuating precipitation events and late frost reduced the length of inflorescences. Under control conditions, interspecific competition reduced photosynthetic activity and growth of L. polyphyllus. When subjected to competition during drought, L. polyphyllus conserved water while simultaneously maintaining high assimilation rates, demonstrating increased water use efficiency. Meanwhile, native species had reduced performance under drought. In summary, the invader gained an advantage under drought conditions through a smaller reduction in performance relative to its native competitors but was competitively inferior under control conditions. This provides evidence for a possible invasion window for this species. While regions of high elevation or latitude with regular severe late frost events might remain inaccessible for L. polyphyllus, further spread across Europe seems probable as the predicted increase in drought events may favour this non-native legume over native species.

Remotely sensed indicators and open-access biodiversity data to assess bird diversity patterns in Mediterranean rural landscapes

Biodiversity monitoring at simultaneously fine spatial resolutions and large spatial extents is needed but limited by operational trade-offs and costs. Open-access data may be cost-effective to address those limitations. We test the use of open-access satellite imagery (NDVI texture variables) and biodiversity data, assembled from GBIF, to investigate the relative importance of variables of habitat extent and structure as indicators of bird community richness and dissimilarity in the Alentejo region (Portugal). Results show that, at the landscape scale, forest bird richness is better indicated by the availability of tree cover in the overall landscape than by the extent or structure of the forest habitats. Open-land birds also respond to landscape structure, namely to the spectral homogeneity and size of open-land patches and to the presence of perennial vegetation amid herbaceous habitats. Moreover, structure variables were more important than climate variables or geographic distance to explain community dissimilarity patterns at the regional scale. Overall, summer imagery, when perennial vegetation is more discernible, is particularly suited to inform indicators of forest and open-land bird community richness and dissimilarity, while spring imagery appears to be also useful to inform indicators of open-land bird richness.