Land Cover and Climate Change May Limit Invasiveness of Rhododendron ponticum in Wales

Allelopathic potential and allelochemical composition in different soil layers of Rhododendron delavayi forest, southwest China

Forests habituated by Rhododendron delavayi often lack understory vegetation, which could possibly be a consequence of allelopathy. It is a phenomenon by virtue of which certain plant species produce allelochemicals that affect the growth and behavior of surrounding plants. To elucidate the allelopathic potential and allelochemicals present in the different layers of a R. delavayi forest, extracts obtained from three layers of the forest were used for seed germination bioassays and gas chromatography-mass spectrometry (GC–MS) analysis. Aqueous extracts of the litter and humus layers significantly inhibited the seed germination of R. delavayi, Festuca arundinacea, and Lolium perenne, with the litter layer causing the strongest inhibitory effect. A total of 26 allelochemicals were identified in the litter, humus, and soil layers by GC–MS analysis. The primary allelochemicals in the soil and humus layer were organic acids, while the main allelochemicals in the litter layer were phenolic acids. The redundancy analysis revealed the significance of total nitrogen (TN) and relative water content (RWC) in explaining the distribution of the allelochemicals. The results indicated that the litter layer exerted the maximum allelopathic effect due to presence of maximum amount of allelochemical especially the phenolic acids.

Predicted range shifts of invasive giant hogweed (Heracleum mantegazzianum) in Europe

Heracleum mantegazzianum Sommier & Levier (Giant hogweed) has spread across Europe after its introduction as an ornamental from the native range in the Western Greater Caucasus. In addition to its invasive capability, H. mantegazzianum reduces the alpha diversity of native species in the non-native range and can cause second-degree burns when its phytotoxic sap contacts the skin upon exposure to sunlight. Previous studies on H. mantegazzianum distribution focused on individual countries, therefore we know little about the potential shift of the species distribution under changing climate at the continental scale. To fill that gap in the current knowledge, we aimed to (i) identify the most important climatic factors for the distribution of H. mantegazzianum in Europe, (ii) recognize areas that will be suitable and unsuitable for future climate scenarios to prioritize management action. Our study showed that the mean temperature of the coldest quarter (bio11) and temperature annual range (bio7) were the most important bioclimatic variables predicting the suitable habitat of the species in Europe. For all scenarios, we found that the majority of the range changes expected by 2100 will occur as early as 2041. We predicted an overall decrease in climatically suitable area for H. mantegazzianum under climate change with over three quarters (i.e. 94%) of the suitable area reduced under the Shared Socioeconomic Pathway (SSP) 585 in 2100. However, under the same scenario, climate conditions will likely favour the expansion (i.e. 20%) of H. mantegazzianum in northern Europe. The results from the present study will help in developing a climate change-integrated management strategy, most especially in northern Europe where range expansion is predicted.

Potential Distribution of Amphibians with Different Habitat Characteristics in Response to Climate Change in South Korea

Simple Summary

Amphibian species are one of one of the groups most vulnerable to climate change according to the International Union for Conservation of Nature (IUCN). Limited research has been conducted investigating the effects of climate change on amphibian species in South Korea. In our study, we aimed to predict the impacts of climate change on the distribution of 16 of the 18 species of amphibians currently reported in South Korea. Altogether, 30,281 occurrence points, six bioclimatic variables, and one environmental variable (altitude) were used in modeling. Moreover, we classified 16 Korean amphibians into three groups based on their habitat characteristics: wetland amphibians (Group 1), migrating amphibians (Group 2), and forest-dwelling amphibians (Group 3). Altitude has been predicted to be a major factor in present amphibian distributions in South Korea. In general, our results show that the seven species in Group 1 should be the most resistant to climate change. The five migrating amphibians (Group 2) should decline with preferred habitat reductions. The forest-dwelling amphibian species (Group 3) are the most vulnerable to climate change and their protection requires the immediate implementation of conservation strategies. We will continue to refine our model as it evolves into a useful tool for our endeavor to preserve South Korea’s amphibians as climate change progresses.

Abstract

Amphibian species are highly vulnerable to climate change with significant species decline and extinction predicted worldwide. However, there are very limited studies on amphibians in South Korea. Here, we assessed the potential impacts of climate change on different habitat groups (wetland amphibians, Group 1; migrating amphibians, Group 2; and forest-dwelling amphibians, Group 3) under future climate change and land cover change in South Korea using a maximum entropy modelling approach. Our study revealed that all amphibians would suffer substantial loss of suitable habitats in the future, except Lithobates catesbeianus, Kaloula borealis, and Karsenia koreana. Similarly, species richness for Groups 2 and 3 will decline by 2030, 2050, and 2080. Currently, amphibian species are widely distributed across the country; however, in future, suitable habitats for amphibians would be concentrated along the Baekdudaegan Mountain Range and the southeastern region. Among the three groups, Group 3 amphibians are predicted to be the most vulnerable to climate change; therefore, immediate conservation action is needed to protect them. We expect this study could provide crucial baseline information required for the government to design climate change mitigation strategies for indigenous amphibians.

Effect of Invasive Rhododendron ponticum L. on Natural Regeneration and Structure of Fagus orientalis Lipsky Forests in the Black Sea Region

Biological invasions threaten global biodiversity and forest ecosystems; therefore, it is necessary to use appropriate strategies for combating the spread of invasive species. Natural regeneration of eastern beech (Fagus orientalis Lipsky) is considerably limited by an aggressive invasive shrub, pontic rhododendron (Rhododendron ponticum L.), in the Black Sea Region of Turkey. Therefore, the future character of the region’s forests is uncertain. The aim of this research was to evaluate the structure of beech forests with different management regimes of rhododedron and to determine the interaction among tree layer, rhododendron cover, and natural regeneration in Düzce Province using the FieldMap technology. The following variants of forests were compared: without intervention (control) and three and six years after rhododendron clearance. The results showed that tree density ranged between 175–381 trees ha−1 and stand volume between 331–589 m3 ha−1. The horizontal structure of the tree layer was mostly random, and the spatial pattern of natural regeneration was aggregated. Recruit density and height in the beech stands were significantly differentiated due to the influence of presence or absence of invasive rhododendron. Rhododendron cover ranged between 81%–97%, and woody stems amounted to 72,178–86,884 ha−1 in unmanaged forests. Canopy in the overstory did not have a significant effect on the density of regeneration and rhododendron cover. Tree layer had a significant negative influence on natural regeneration within a 4 m radius on the plots without rhododendron. However, on the plots with dense rhododendron cover, tree layer had a positive influence on regeneration within a 1.5 m radius. Natural regeneration density was significantly higher when rhododendron was cleared than the plots without intervention. On the plots without woody clearance, there was an insufficient regeneration (113–619 recruits ha−1); however, they had higher mean height compared to the sites without rhododendron. After three and six years of rhododendron clearance, the numbers of recruits in natural regeneration were 63,981 ha−1 and 105,075 ha−1, respectively. In conclusion, invasive spread of rhododendron was a limiting factor of the prosperous regeneration and tree species diversity, and manual clearance of rhododendron is recommended in managed beech forests of the study region.

Evidence of ecological niche shift in Rhododendron ponticum (L.) in Britain: Hybridization as a possible cause of rapid niche expansion

Biological invasions threaten global biodiversity and natural resources. Anticipating future invasions is central to strategies for combating the spread of invasive species. Ecological niche models are thus increasingly used to predict potential distribution of invasive species. In this study, we compare ecological niches of Rhododendron ponticum in its native (Iberian Peninsula) and invasive (Britain) ranges. Here, we test the conservation of ecological niche between invasive and native populations of R. ponticum using principal component analysis, niche dynamics analysis, and MaxEnt-based reciprocal niche modeling. We show that niche overlap between native and invasive populations is very low, leading us to the conclusion that the two niches are not equivalent and are dissimilar. We conclude that R. ponticum occupies novel environmental conditions in Britain. However, the evidence of niche shift presented in this study should be treated with caution because of nonanalogue climatic conditions between native and invasive ranges and a small population size in the native range. We then frame our results in the context of contradicting genetic evidence on possible hybridization of this invasive species in Britain. We argue that the existing contradictory studies on whether hybridization caused niche shift in R. ponticum are not sufficient to prove or disprove this hypothesis. However, we present a series of theoretical arguments which indicate that hybridization is a likely cause of the observed niche expansion of R. ponticum in Britain.

Potential impact of climate change on plant invasion in the Republic of Korea

Background

Invasive plant species are considered a major threat to biodiversity, ecosystem functioning, and human wellbeing worldwide. Climatically suitable ranges for invasive plant species are expected to expand due to future climate change. The identification of current invasions and potential range expansion of invasive plant species is required to plan for the management of these species. Here, we predicted climatically suitable habitats for 11 invasive plant species and calculated the potential species richness and their range expansions in different provinces of the Republic of Korea (ROK) under current and future climate change scenarios (RCP 4.5 and RCP 8.5) using the maximum entropy (MaxEnt) modeling approach.

Results

Based on the model predictions, areas of climatically suitable habitats for 90.9% of the invasive plant species are expected to retain current ecological niches and expand to include additional climatically suitable areas under future climate change scenarios. Species richness is predicted to be relatively high in the provinces of the western and southern regions (e.g., Jeollanam, Jeollabuk, and Chungcheongnam) under current climatic conditions. However, under future climates, richness in the provinces of the northern, eastern, and southeastern regions (e.g., Seoul, Incheon, Gyeonggi, Gyeongsangnam, Degue, Busan, and Ulsan) is estimated to increase up to 292%, 390.75%, and 468.06% by 2030, 2050, and 2080, respectively, compared with the current richness.

Conclusions

Our study revealed that the rates of introduction and dispersion of invasive plant species from the western and southern coasts are relatively high and are expanding across the ROK through different modes of dispersion. The negative impacts on biodiversity, ecosystem dynamics, and economy caused by invasive plant species will be high if preventive and eradication measures are not employed immediately. Thus, this study will be helpful to policymakers for the management of invasive plant species and the conservation of biodiversity.

Scenario-led modelling of broadleaf forest expansion in Wales

Significant changes in the composition and extent of the UK forest cover are likely to take place in the coming decades. Current policy targets an increase in forest area, for example, the Welsh Government aims for forest expansion by 2030, and a purposeful shift from non-native conifers to broadleaved tree species, as identified by the UK Forestry Standard Guidelines on Biodiversity. Using the example of Wales, we aim to generate an evidence-based projection of the impact of contrasting policy scenarios on the state of forests in the near future, with the view of stimulating debate and aiding decisions concerning plausible outcomes of different policies. We quantified changes in different land use and land cover (LULC) classes in Wales between 2007 and 2015 and used a multi-layer perceptron-Markov chain ensemble modelling approach to project the state of Welsh forests in 2030 under the current and an alternative policy scenario. The current level of expansion and restoration of broadleaf forest in Wales is sufficient to deliver on existing policy goals. We also show effects of a more ambitious afforestation policy on the Welsh landscape. In a key finding, the highest intensity of broadleaf expansion is likely to shift from southeastern to more central areas of Wales. The study identifies the key predictors of LULC change in Wales. High-resolution future land cover simulation maps using these predictors offer an evidence-based tool for forest managers and government officials to test the effects of existing and alternative policy scenarios.

Linking Social Perception and Provision of Ecosystem Services in a Sprawling Urban Landscape: A Case Study of Multan, Pakistan

Urban sprawl causes changes in land use and a decline in many ecosystem services. Understanding the spatial patterns of sprawl and exploration of citizens’ perception towards the sporadic urban expansion and its impacts on an ecosystem to deliver services can help to guide land use planning and the conservation of the urban ecosystem. Here, we spatially examined land use changes in Multan, Pakistan, and investigated public perception about urban sprawl and its impacts on the quality and provision of ecosystem services, using a survey instrument. The spatial analysis of the historical land cover of Multan indicated an exponential expansion of the city in the last decade. Large areas of natural vegetation and agricultural land were converted to urban settlements in the past two decades. The citizens of Multan believe that the quality and provision of ecosystem services have declined in the recent past and strongly correlate the deteriorating ecosystem services with urban sprawl. Education and income levels of the respondents are the strongest predictors of urban ecosystem health literacy. Citizens associated with laborious outdoor jobs are more sensitive to the changes in ecosystem services. We concluded that the rapidly expanding cities, especially in the tropical arid zones, need to be prioritized for an increase in vegetation cover, and economically vulnerable settlements in these cities should be emphasized in climate change mitigation campaigns.