Exotic Woody Species Research Articles

Revegetated riparian areas are dominated by weeds, and lack structural diversity and natural recruitment: lessons for restoration practice

Riparian areas can be highly biodiverse and provide critical ecosystem services. However, they are frequently subject to anthropogenic impacts such as land clearing, agricultural use, and urban development. Restoration of riparian areas via revegetation commonly improves the health of waterways and surrounding areas, but vegetation outcomes are rarely assessed. Our study compared 10 to 14‐year‐old revegetation to remnant vegetation in riparian areas of south‐eastern Australia to determine if species composition, vegetation structure, and ecosystem function (plant recruitment) differed. We also assessed if the amount of surrounding native vegetation, browsers (including deer, rabbits, and macropods), or soil characteristics influenced native woody plant recruitment at revegetated sites. While native and exotic woody species richness did not differ, native woody plants were less abundant and exotic woody plants twice as abundant at revegetated sites. The ground layer of revegetated sites was dominated by weeds, whereas remnant sites largely comprised native herbaceous plants and leaf litter. Tree heights and tree canopy cover were similar in revegetated and remnant areas, although shrubs and ferns were lacking in revegetation. Native woody plant recruitment was lower at revegetated sites and was negatively associated with browser presence. Our results suggest that while revegetation may have similar species richness and tree cover as remnant areas, weeds often dominate and important structural components such as shrubs and ferns, and ecological processes such as plant recruitment, are lacking. Better consideration of all vegetation strata, reduced browsing pressure and weed control are likely to achieve better revegetation outcomes.

Influence of Thinning and Pruning Regime on Woody Species Density and Abundance

The revival of forests is gaining prominence, with a focus on common tree species. However, the most affected species by fragmentation are the exotic woody species; therefore attention to forest silvicultural practices is essential. Kenya is acknowledged as one of the nations that value its forest environment greatly, although there are still restrictions on the application of silvicultural regimes there. This is a result of the continued strong demand for wood. It is anticipated that silvicultural regimes would eclipse Kenya’s fragmentation tactics. Thus, the goal of this research was to evaluate the influence of thinning and pruning regime on the woody species density and abundance in Kimondi forest, Nandi County, Kenya. This study was centered on Eucalyptus saligna, Cupressus lusitanica and Pinus patula as the woody species that are harvested for timber in Kimondi forest. The island biogeography theory served as the basis for this research. The number of woody species per plot, the basal area per plot, the different types of woody species, the total number of each woody species in the study area, the diameter at breast height, soil type, plantation size, soil depth and forest pest were the intervening factors. The study employed a cross-sectional descriptive study design. The study area’s species types were observed, observation schedule was filled, 30 sample plots were randomly selected each measuring 20m by 20m, and the number of woody species in each plot counted and recorded as the primary data. To assess the appropriateness of the species chosen, Two-way Analysis of Variance was used. Based on the study’s findings, Effect size is 36.098%, hence 36.098% of the variation of the abundance and density of woody species can be explained by the thinning and pruning regime. There was a significant interaction. In thinning and pruning regime,Pinus patula was the most abundant with a mean and standard deviation of 6.433a ± 2.37, Cupressus lusitanica had 4.467b ± 1.74 while Eucalyptus saligna had 3.267c ± 1.74.There was a significant difference in the woody species abundance indicated by LSD = 0.711 and p-value = 0.001**.The importance of this research was to raise awareness about the application of silvicultural regimes to enhance the density and abundance of woody species in Kimondi Forest, Nandi County, Kenya, in order to mitigate the consequences of increasing forest fragmentation and species extinction

Las especies arbóreas exóticas en Argentina: caracterización e identificación de las especies actual y potencialmente problemáticas

Biological invasions are one of five direct drivers of global change that act synergistically threatening biodiversity and the provision of ecosystem services globally. In this work we compile the list of exotic woody species that have been introduced in Argentina, we characterize them according to their geographical origin, use, foliage phenology, reproduction, dispersal, and we analyse their geographical distribution within Argentina. Based on the bibliography, we identify those species that are currently or potentially problematic for Argentina. Most of the species are native to Eurasia and the main reason for their introduction was their ornamental use. They are mostly monoecious, with deciduous leaves, without vegetative reproduction, with fleshy fruits and dispersed by animals. The area corresponding to the Yungas, the Paranaense Forest and the Humid Chaco presents the largest number of exotic species; the area corresponding to the Espinal and Dry Chaco has the largest number of currently problematic species and, together with the Pampeana area, the largest number of potentially problematic species. Finally, we propose actual problematic species in areas without native trees and potentially problematic species with broad distribution in Argentina should be monitored and probably managed among the studied species.

Adaptação e eficiência de um índice para análise da integridade biótica em Floresta Ombrófila Densa

Diante dos diversos métodos de mensuração da integridade biótica de determinada área de floresta evidencia-se a Avaliação Ecológica Rápida (AER). Com base na AER foi desenvolvido um índice para avaliar a condição da vegetação, denominado Índice de Integridade Biótica (IIB). A aferição e precisão deste índice retratam o quão íntegro um dado ecossistema florestal se encontra no momento da análise. O alicerce para a eficiência na aplicação do IIB está na escolha correta dos indicadores de integridade biótica, ou seja, nas variáveis a serem mensuradas. O presente estudo partiu de um índice anteriormente proposto para Floresta Estacional Semidecidual (FES), e teve como objetivo adaptar o IIB para uso em área de Floresta Ombrófila Densa no Estado de São Paulo, bem como testar sua eficiência no diagnóstico da integridade de fragmentos de Floresta Ombrófila Densa (FOD) inseridos em matriz rural. Dos onze indicadores presentes no método original, alguns foram mantidos como no original ou adaptados, alguns retirados e alguns novos foram criados. O IIB adaptado foi aplicado numa área de FOD de 70 hectares. Para isso, foram utilizadas 20 parcelas de 10x10m, dentro da área amostral. Os resultados mostraram uma variação do IIB entre 28 e 47, ou seja, 2 parcelas registraram integridade baixa, 11 integridade média e 7 integridade boa. A área como um todo apresentou integridade regular, o que era esperado devido ao seu tamanho, ao entorno agrícola e ao histórico de perturbações. O IIB mostrou-se adaptado e eficiente para análise da integridade biótica da FOD, pois conseguiu mostrar a diferença de integridade entre diferentes trechos de Floresta Ombrófila Densa. Os indicadores menos eficientes foram: “cobertura de serapilheira” e “espécies exóticas lenhosas”. Os mais eficientes foram: “Euterpe edulis”, “epífitas”, “clareiras” e “cipós/lianas”.

Comparative litter decomposability traits of selected native and exotic woody species from an urban environment of north-western Siwalik region, India

Exotic plants can potentially modify ecosystem functions like cycling of nutrients by adjusting their decomposition rates. However, these effects are largely unknown for urban ecosystems, though they act as reservoirs of exotic plants. The present study evaluated the decomposition rates of five native and five exotic (three invasive and two non-invasive) species by conducting the litter bag experiment. Our study, however, did not find any significant differences in overall decomposition rates of native and exotic species but decomposition rates were strongly correlated with initial chemical quality of the litter. Further, litter carbon, lignin to nitrogen ratio and carbon to nitrogen ratio seemed to be good predictors for decomposition rates in this study. Interestingly, invasive exotic species had higher decomposition rate while non-invasive exotic species showed a slower rate as compared to the native species. In conclusion, our study indicates that invasive exotic plants try to maintain a higher chemical quality of litter than native and non-invasive exotic species which promotes their rapid decomposition. Thus, the better chemical quality of litter may facilitate the naturalisation and invasion of exotic plants irrespective of their origin.

Carbon stock and woody species diversity patterns in church forests along church age gradient in Addis Ababa, Ethiopia

Most of the Ethiopian Orthodox Churches comprise natural and planted forests and trees on their premises. A study was conducted to investigate carbon stock and woody species diversity patterns along the church age gradient in Addis Ababa city. We hypothesized that the carbon stock would relate to the church age gradient. Thus, the study was conducted in forests belonging to churches that were selected in a stratified random sampling from four age categories with the year of establishments ranging from 1897 to 1993. Counting of all the woody species and DBH and height measurement of all individuals with DBH of 5 cm and above was carried out. Carbon stock and different diversity indices were computed, and the relationships between church age and tree parameters were evaluated. Results showed that the forests were characteristically small (0.6 ± 0.57 ha), and the tree species with the highest total carbon stock were Juniperus procera, Eucalyptus globulus and E. camaldulensis. The mean amount of carbon stock contained in each church forest was 156 ± 92 t ha-1. A total of 50 indigenous and 40 exotic woody species were identified. A statistically significant difference (p < 0.05) among the four Strata was revealed for the carbon stock of native trees. Correlation analysis also revealed a significant positive relationship between church age and native trees’ carbon stock. We conclude that the church forests have a very important role in carbon sequestration and biodiversity conservation, and thus scaling up the long-term maintenance and management of such small-sized forests in urban green spaces is vital.

Exotic pine forestation shifts carbon accumulation to litter detritus and wood along a broad precipitation gradient in Patagonia, Argentina

Carbon dioxide emissions to the atmosphere from human activity continue to increase, and accordingly, strategies of biological carbon (C) sequestration in terrestrial ecosystems have been proposed. Forestation projects have garnered wide public support, and research has focused principally on how soil C storage is affected. Nevertheless, our mechanistic understanding of how forestation, particularly with exotic woody species, affects ecosystem processes is not well understood. We took advantage of a land-use change in Patagonia, Argentina, that involved the simultaneous planting of a single conifer species (Pinus ponderosa) along a broad precipitation gradient [250–2200 mm mean annual precipitation (MAP)], replacing natural ecosystems from semi-arid steppe to broadleaf forest. Comparing C fluxes and stocks in five paired natural and planted forest sites during three consecutive years demonstrated that aboveground net primary production (ANPP) was consistently greater in forested areas along the gradient, while litter decomposition markedly decreased. Dramatic increases in leaf litter detritus, coupled with increased aboveground woody biomass, contributed to identical levels of C accumulation in pine plantations from 250 mm to 1350 mm MAP, without significantly detectable differences in surface soil C. The replacement of intact forest in the most humid site resulted in large decreases in vegetation C pools. The implications for ecosystem C cycling suggest that inhibition of C turnover, along with the aboveground woody growth, are key variables contributing to the observed patterns of C accumulation from exotic pine forestation along this precipitation gradient. Given the transient nature of these C stocks, vulnerable to loss as CO2 due to climatic or anthropogenic disturbances, these changes may not contribute to long-term C sequestration in these ecosystems. The conversion of natural ecosystems as a management tool for C mitigation should include a consideration of the realized sequestration potential but also the unintended consequences for changes in both C inputs and C turnover that determine the ecosystem C balance, as well as potential effects on biodiversity and long-term ecosystem functioning.

Fire differentially affects mortality and seedling regeneration of three woody invaders in forest–grassland mosaics of the southern Western Ghats, India

Invasion by exotic woody species is a major concern in grasslands worldwide. Woody invasions pose a particularly serious threat to forest–grassland mosaics globally, but the factors influencing the success of woody species in these systems, including the role of disturbances such as fire, are not well understood. In this study, we evaluated the role of fire in influencing mortality and regeneration success of three globally widespread woody invasives, Acacia mearnsii (black wattle), Cytisus scoparius (scotch broom) and Ulex europaeus (gorse) in the montane forest–grassland mosaics of the Nilgiri Biosphere Reserve in the Western Ghats biodiversity hotspot, India. Our results indicate that mortality and regeneration responses to fire are species-specific. Fire-induced adult mortality was highest in scotch broom and lowest in gorse, and high, but variable in wattle. Burning greatly increased the abundance of gorse and wattle seedlings, but only marginally increased scotch broom seedling abundance. Fire effects on invasive seedling densities were most pronounced at the edges of invasive patches. Overall, our results indicate that fires are likely to differentially affect invasion patterns of these three species, with fire potentially encouraging invasion by gorse and wattle and discouraging invasion by scotch broom.

Predicting invasiveness of exotic woody species using a traits-based framework.

Identifying potentially invasive species and preventing their introduction and establishment are of critical importance in invasion ecology and land management. Although an extensive body of research has been dedicated to identifying traits that confer invasiveness, our current knowledge is still often inconclusive due to limitations in geographic extent and/or scope of traits analyzed. Here, using a comprehensive set of 45 traits, we performed a case study of invasive traits displayed by exotic woody plants in the United States (U.S.) by comparing 63 invasive and 794 non-invasive exotic woody plant species naturalized across the country. We found that invasive woody species often bear the following two key traits: vegetative reproduction and long-distance seed dispersal (via water, birds or mammals). Boosted classification tree models based on these traits accurately predicted species invasiveness (86% accuracy on average). Presented findings provide a generalized understanding of the relative importance of functional traits in identifying potentially invasive woody species in the U.S. The knowledge generated in this study can be used to improve current classification systems of non-native woody plants used by various U.S. governmental agencies and land managers.

RETRACTED ARTICLE: Distribution and ecological impact of exotic woody plant species inside sacred groves of Northwestern Ethiopia

The northern highlands of Ethiopia have undergone drastic forest loss and habitat degradation leaving fragmented small patches of sacred groves that have been threatened by land use changes including exotic plantation. The aim of this study was to examine the composition, distribution and impacts of exotic woody plants on vegetation dynamics inside church forests. To do these, 46 sacred groves were selected using stratified sampling based on elevation, forest size, wall, and their distance from towns. Vegetation data were collected in three transects using three compass directions. ANOVA was used to determine the effects of factors on the distribution of exotic woody plants and Regression analysis was also used to determine relationships between %exotic and vegetation dynamics. All data were analyzed using SAS in JMP-14 software. The study revealed that 38 (82.6%) out of 46 forests had exotic woody plants (924 exotic woody stems with 20 different species). The result also confirmed that sacred groves nearer to the towns, the absence of stone wall along the forest periphery and forests with high %human disturbance have high distribution of exotic woody species. These expansions of exotic woody plants significantly reduced the diversity, density, biomass and regeneration of native woody plants. The high demand for exotic trees like Eucalyptus for socio-economic importance may lead the sacred groves into mono-crop cultivation (vegetation) by substituting the existed multiple native plants. To preserve these sacred groves which are the remnant reservoirs of native plants from the exotic hazard, the traditional forest management techniques should be strengthened.

Wood and non-wood forest products of Central Java, Indonesia

ABSTRACTWe investigated herb and woody species at rehabilitated forests planted by mahogany and teak, and original, not rehabilitated forests in Yogyakarta, Indonesia. Plant species were classified into five use categories: medicine, food, fodder, ornament, and construction. We registered 142 species belonging to 54 families known as useful species with at least one, often more, use categories. The number of useful species was highest for medicine use (107 species). There was a dominance of exotic herb species used for food and annual herbs used for fodder. The number of useful herbs and exotic woody species was highest in teak stands. The number of woody species used for medicine, food, and construction was higher than those for ornament and fodder. All herb species decreased with time, except annual native, that increased. Around 50% of the useful species occurred only once in one site, and some species showed a distribution restricted to one type of stands. Overall, our results seem to show that rehabilitated stands are doing well with regard to useful herb and woody species. We suggest strategies for plant and ecosystem conservation, especially for rare native plant species and species with restricted distribution.

Contrasting Species Diversity and Values in Home Gardens and Traditional Parkland Agroforestry Systems in Ethiopian Sub-Humid Lowlands

Understanding the complex diversity of species and their potential uses in traditional agroforestry systems is crucial for enhancing the productivity of tropical systems and ensuring the sustainability of the natural resource base. The aim of this study is the evaluation of the role of home gardens and parklands, which are prominent tropical agroforestry systems, in the conservation and management of biodiversity. Our study quantified and compared the diversity of woody and herbaceous perennial species and their uses in traditional home gardens and parkland agroforestry systems under a sub-humid climate in western Ethiopia. A sociological survey of 130 household respondents revealed 14 different uses of the species, mostly for shade, fuelwood, food, and as traditional medicine. Vegetation inventory showed that the Fisher’s α diversity index and species richness were significantly higher in home gardens (Fisher’s α = 5.28 ± 0.35) than in parklands (Fisher’s α = 1.62 ± 0.18). Both systems were significantly different in species composition (Sørenson’s similarity coefficient = 35%). The differences occurred primarily because of the high intensity of management and the cultivation of exotic tree species in the home gardens, whereas parklands harbored mostly native flora owing to the deliberate retention and assisted regeneration by farmers. In home gardens, Mangifera indica L. was the most important woody species, followed by Cordia africana Lam. and Coffea arabica L. On the other hand, Syzygium guineense Wall. was the most important species in parklands, followed by C. africana and M. indica. The species diversity of agroforestry practices must be further augmented with both indigenous and useful, non-invasive exotic woody and herbaceous species, particularly in parklands that showed lower than expected species diversity compared to home-gardens.

Disturbance types, herbaceous composition, and rainfall season determine exotic tree invasion in novel grassland

Novel grasslands embedded in anthropogenic landscapes are increasingly threatened due to invasion by exotic woody species. This potential for tree invasion in grasslands can be either facilitated or hindered by disturbance agents and/or herbaceous composition. Furthermore, disturbances may depend on inter-annual rainfall modifying the chance of woody establishment. Here we determine how large- and small-scale disturbances influence the establishment of the exotic tree Gleditsia triacanthos across different herbaceous patches in an old-field pampa grassland in Argentina. Tree seeds were copiously added in all study plots and were then monitored over 4 years for seedling recruitment and growth rates in a fully factorial disturbance x patch type experimental design. We used burning (large scale) and armadillo-like burrowing (small scale) as the two levels of disturbance, and grass dominated and forb dominated patches as the two types of patches. After seed sowing, two seedling cohorts emerged during the drier and wetter summers, in March 2000 (xeric cohort) and January 2001(mesic cohort), respectively. Tree recruitment was twice as high for the mesic cohort in comparison to the xeric cohort, but for both cohorts tree recruitment was significantly higher in the forb patches than in the grass patches. For the mesic cohort, tree recruitment was enhanced for both types of disturbance, while for the xeric cohort, recruitment was depressed by the small-scale disturbance. Lastly, sapling growth rates were influenced by disturbance, with xeric cohort saplings being larger in the small-scale disturbance and mesic cohort saplings being smaller in the large-scale disturbance. Taken together, tree seedling invasion was enhanced in forb-dominated patches during an early dry season, but it was mainly enhanced by disturbance agents during a wetter season. Hence, while disturbances can promote exotic plant species, our findings emphasize the spatiotemporal aspects of woody invasions in novel grasslands.

Pine Stand Density Influences the Regeneration of Acacia saligna Labill. H.L.Wendl. and Native Woody Species in a Mediterranean Coastal Pine Plantation

Mediterranean plantations are the most suitable areas to assess vegetation dynamics and competitive interactions between native and exotic woody species. Our research was carried out in a coastal pine plantation (Sicily) where renaturalization by native species (Pistacia lentiscus L. and Olea europaea var. sylvestris) and invasion by Acacia saligna (Labill.) H.L.Wendl. simultaneously occur. The regeneration pattern of woody species in the pine understory was evaluated in six experimental plots along a stand density gradient, from 200 to approximately 700 pines per hectare. Both pine stand density and regeneration by native species had a significant negative relationship with Acacia natural regeneration. Olea regeneration was positively correlated with stand density, while Pistacia showed a non-significant relationship. Saplings of both native species were mostly less than 1 m high, whereas approximately 70% of Acacia individuals were higher than 1 m. We found that 400 pines per hectare should be considered a minimum stand density to keep Acacia under control, while favouring the establishment of native species in the understory. The successful control of Acacia requires an integrated management strategy, including different forest interventions according to stand density: thinning, control measures against Acacia, and renaturalization actions.

Are endemics functionally distinct? Leaf traits of native and exotic woody species in a New Zealand forest.

Recent studies have concluded that native and invasive species share a common set of trait relationships. However, native species in isolated regions might be functionally constrained by their unique evolutionary histories such that they follow different carbon capture strategies than introduced species. We compared leaf traits relating to resource investment, carbon return, and resource-use efficiency in 16 native (endemic) and three non-native (invasive) species in a temperate forest in Canterbury, South Island, New Zealand. Trait differences were more closely associated with leaf habit than nativity. Deciduous species (including invaders) exhibited greater maximum photosynthetic rates at similar resource costs, which resulted in greater nitrogen- and energy-use efficiencies than evergreen natives. Leaf area was the only trait that differed significantly by nativity (over two-fold larger in invaders). Invaders and deciduous natives both occupied the ‘fast return’ end of the leaf economics spectrum in contrast to the native evergreens which had comparatively slow return on investment. Dominant woody invaders in this forest are physiologically distinct from many New Zealand endemic species, which are overwhelmingly evergreen. It remains unclear whether these trait differences translate to an ecological divergence in plant strategy, but these results suggest that ecophysiological tradeoffs are likely constrained by biogeography.

Biodiversity bottleneck: seedling establishment under changing climatic conditions at the boreal–temperate ecotone

Climate change is increasing global temperatures, severe rainfall events, and the occurrence and severity of drought. Changes in global climate may have negative consequences for particular plant species and for biodiversity overall. In the short term, altered temperature and precipitation regimes may have the most severe effects on plant species near their range limits and in the earliest stages of plant development. To address these issues, we assessed seedling emergence, early survival, and growth of 18 boreal, temperate, and exotic woody species at the boreal–temperate forest ecotone in central Minnesota. We experimentally warmed forest plots to mimic projected warming by the end of the twenty-first century (+ 1.7 °C and + 3.4 °C). We also experimentally removed summer rainfall (~ 42% reduction) to simulate drought conditions in this region. We found that emergence and survival of boreal and exotic species was lower in experimentally warmed plots. This was exacerbated by drought. Temperate species emergence and survival was largely unaffected by climate manipulations (on average). Conversely, temperate seedling growth was greater in warmer conditions, but only when paired with drought. We found that overall seedling species richness was reduced by warming, mostly due to lower boreal and exotic species emergence and survival (conifers were also strongly negatively affected across species-range groups). If temperate seedling emergence and survival does not compensate for loss of boreal species, these forests may experience loss of biodiversity (and associated ecosystem functions) in the future.

Desarrollo de especies leñosas nativas y exóticas en cipresales patagónicos.

El crecimiento y la arquitectura de las especies leñosas que habitan los bosques inciden en la dinámica de estas comunidades. El objetivo principal de este estudio fue mejorar la comprensión de la dinámica de los cipresales patagónicos a partir del análisis del crecimiento longitudinal y de la arquitectura de las especies leñosas más abundantes en esas comunidades, las nativas: Aristotelia chilensis, Berberis microphylla, Lomatia hirsuta, Maytenus boaria, Myoschilos oblongum y Schinus patagonicus; y las exóticas: Juniperus communis, Prunus avium, Pseudotsuga menziesii y Rosa rubiginosa. El crecimiento longitudinal del eje principal no se relacionó necesariamente con el aumento en altura de las plantas durante el período de estudio (2012-14). Se registraron decrecimientos en altura en todas las especies excepto en P. menziesii y P. avium, exóticas para Patagonia. La mayoría de los individuos presentaron notables desviaciones de su eje principal de la vertical, las que se correlacionaron negativamente con la longitud del brote distal y con la variación en altura de las plantas. Se agruparon las especies en cuatro grupos funcionales, de acuerdo a su arquitectura y crecimiento. La invasión de los cipresales por parte de especies exóticas como P. menziesii y P. avium, asociadas a grupos funcionales distintos a los de las especies nativas más frecuentes, podría impactar significativamente en la dinámica de esas comunidades promoviendo el reemplazo de las especies nativas por las exóticas dominantes.

The influence of soil resources and plant traits on invasion and restoration in a subtropical woodland

It has been shown in some cases that nitrogen (N) addition to soil will increase abundance of plant invaders because many invaders have traits that promote rapid growth in response to high resource supply. Similarly, it has been suggested, and sometimes shown, that decreasing soil N via carbon (C) additions can facilitate native species recovery. Yet all species are unlikely to respond to resource supply in the same way. We asked how soil nutrients and competition affect native and exotic woody species in a restoration experiment where we added N or C, and crossed soil manipulation with the manipulation of dominant exotic grass abundance in a Hawaiian subtropical woodland. We related changes in survival and growth of outplanted individuals to native/exotic status and plant traits. As a group, N-fixers showed reduced survival compared to non-fixers in response to added N, with Morella faya (exotic) and Acacia koa (native) having dramatic negative responses. Among non-fixers, species with greater foliar %N had more positive survival responses to increasing soil N. Specific leaf area was not predictive of responses to nutrients or competition. In general, responses to carbon addition were weak, although reducing competition from existing exotic grasses was beneficial for all outplanted species, with N-fixers showing the most positive response. We conclude that commonly used restoration strategies to clear exotic species or lower soil resources with C addition will most greatly benefit N-fixing species, which themselves may be unwanted invaders. Thus statements about the influence of increased soil N on invasions should be carefully dissected by considering the traits (such as N-fixation status) of the regional species pool.

Observations on the Woody Wall Flora of Varanasi City, India

An observational study was conducted to explore the woody wall flora of the world’s oldest city of Varanasi, India located at the bank of sacred Ganges River. Forty one woody plants of 35 genera belonging to 18 families were recorded on the walls of the city represented exclusively by the dicotyledonous angiospermic group of plants. Fabaceae, Moraceae and Apocynaceae were the dominant families of the woody wall flora of Varanasi city. Native woody species were greater in number compared to exotic woody species on the walls of Varanasi city.

Exotic invasive plants alter thermal regimes: implications for management using a case study of a native ectotherm

Summary Exotic invasive plants can alter ecosystem structure and function, yet there is a paucity of evidence regarding broadly applicable mechanisms. We hypothesized that denser growth patterns characteristic of exotic invasive plants lead to a common effect of reduction and homogenization of environmental temperatures and that these alterations compromise thermal quality of habitat for ectotherms. We quantified thermal regimes within native and exotic plant‐dominated habitats, including monocultures of 11 exotic species as well as stratified mixed‐exotic habitats in a temperate forest landscape in the eastern US. Exotic plant‐dominated habitats exhibited reduced and less variable temperature compared to their native counterparts, with stratified mixed‐exotic habitats exhibiting the lowest temperatures overall and exotic shrubs (six species) the lowest as a structural group. Thermal effects were extended beyond the growing season of native vegetation owing to extended leaf phenology of exotic woody species. To demonstrate that these effects can alter environmental cues and adversely impact native species, we used a 4‐year radiotelemetry study and laboratory thermal preference trials to relate habitat thermal quality to multiscale resource selection by a native snake, Agkistrodon contortrix. To further test the effect of vegetation structure and the efficacy of targeted management, we removed exotic foliar cover from eight 400 m2 plots. Radio‐tagged snakes avoided exotic vegetation at multiple spatial scales. In contrast to previous studies of A. contortrix, snakes exhibited preference for sites composed of higher native vegetation density and height. Response to exotic foliage removal was also rapid – including use of sites during gestation and parturition. Together with other recent studies, our results suggest a direct, non‐trophic effect that is common to a broad range of exotic invasive plant species in a variety of ecological contexts. We further offer a mitigation technique that may be implemented when large‐scale control or eradication is not cost‐effective or ecologically sound.