Does intrinsic light heterogeneity in Ricinus communis L. monospecific thickets drive species' population dynamics?

Leaf Functional Traits Vary in Urban Environments: Influences of Leaf Age, Land-Use Type, and Urban–Rural Gradient

An increasing number of studies have focused on the response and adaptation of plants to urbanization by comparing differences in leaf functional traits between urban and rural sites. However, considerable uncertainties remain because differences in land-use type have not frequently been taken into account when assessing the effect of urbanization on leaf traits. In this study, we sampled the needles of Chinese pine (Pinus tabuliformis Carr.) in areas with three land-use types (roadsides, parks, and neighborhoods) along an urban–rural gradient in Beijing, China to determine the effect of urbanization on leaf functional traits. There were significant differences in the values of leaf functional traits between the needles of the current and previous year and across land-use types. Pines growing on roadsides had leaves with smaller length, width, and area, as well as lower stomatal density, compared with those growing in parks and neighborhoods. This implies that on roadsides, plant capacity to acquire resources (e.g., light and carbon dioxide) was degraded. Stomatal density, leaf width, and leaf P concentration increased with increasing distance from the city center, while leaf K concentration decreased with increasing distance from the city center. Importantly, there were significant differences in the urban–rural gradient of leaf functional traits between leaves of different ages, and across land-use types. Leaf age was the most important factor influencing leaf nutrient traits, while land-use type was the most important factor influencing leaf morphological traits in urban environments. Thus, considering the effects of the plant characteristic and land-use type on traits is important for assessing the urban–rural gradients of plant functional traits.

A missing cog in the wheel: an Allee effects perspective in biological invasion paradigm

Environmental stochasticity and invasive species demographical factors are considered to be fundamental aspects of species invasion. Population size, density, and intraspecific competition are the important determinants of species range expansion. Allee effects, interesting density-dependent phenomena, act as 'mechanism of population regulation' during species expansion. The study intends to understand the trend of published researches and identify research gaps pertaining to biological invasions and Allee effects with the help of bibliometric analysis. Content and citation analysis using key words 'Allee effects' AND 'biological invasion' was conducted on research articles published over a period of two and a half decades from Scopus database for global and Indian context. Understanding of Allee effects dynamics in context of biological invasion is limited, especially in India. Integrating the emerging trends pertaining to Allee effects in the biological invasion framework will strengthen the understanding on species range expansion. It is emphasized that Allee effects can emerge as an important tool to manage invasive species range expansion.