Demographic strategies of a dominant tree species in response to logging in a degraded subtropical forest in Southeast China

International audienceAbstractKey messageThe demography of pioneer tree species (Pinus massonianaLamb.) is significantly affected by logging in Southeast China. Logging negatively affects the population growth rate ofP. massoniana, which facilitates the growth of individual trees but has no effect on reproduction probability. The survival and growth of seedlings contribute the most to population growth.ContextSubtropical forest degradation caused by unreasonable disturbances is closely related to anthropogenic activities in Southeast China, and the frequent small-scale logging activity by local people was the dominated disturbance regime in forests in this region over the past several decades.AimsThe objective of this study is to evaluate the demographic consequences of logging on Pinus massoniana, a pioneer tree species, at individual level (survival, growth, and fecundity) and population level (the population growth rate and size distribution) over short-term period.MethodsThe size of tree individuals was combined with vital rates using various modeling approaches based on demographic data from three annual censuses. The integral projection model (IPM) was constructed and used to conduct comparative demographic analyses.ResultsLogging negatively affected the population growth rate: from a slight expansion before logging to a moderate decline after logging. This study found a significant reduction in seedling recruitment after logging, and plant growth and mortality were slightly enhanced. The survival of seedlings greatly contributes to population growth rate compared to other life stages for both periods (before and after logging) while its relative importance decreases after logging. Seedling growth is also important to population growth, and its relative importance increased after logging. Shrinkage and fecundity have a minimal contribution effect on the population growth rate.ConclusionGrowing plants in a nursery with a similar demography to P. massoniana could be beneficial for pioneer species regeneration in that this will improve the survival rate and growth of small individuals after logging

An analytical approach for synthesizing line actuation spaces of parallel flexure mechanisms

In this study, we present an analytical approach for synthesizing line actuation spaces of a parallel flexure mechanism (PFM) that can help designers to arrange linear actuators within the PFM in a correct and optimal way. On the basis of screw theory and upon an assumption of small deformations, an important synthesis criterion stated as “any actuation space of a flexure mechanism is always linearly independent of its constraint space” has been derived and disclosed for the first time. Guided by this criterion, a general synthesis process for the line actuation spaces of PFMs is introduced and demonstrated with several selective examples. The proposed synthesis criterion and process will enable designers to (i) systematically formulate line actuation spaces in the format of screw systems; (ii) likely yield a multiple solution to actuation spaces; and (iii) potentially determine an optimal result from those alternatives for actuator placement

Holistic digital-twin-based framework to improve tunnel lighting environment: From methodology to application

The design of the lighting environment inside the tunnel has a profound impact on the long-term operation of the tunnel. The existing field studies, full-scale experiments and simulation methods, mostly focus on the luminance level inside the tunnel, ignoring the effect of the luminaires and decorations from the visual perspective. This paper proposed a novel digital-twin-based integral method, including virtual world design (the virtual reality (VR) experiment and the numerical simulation) and real-world validation (the tunnel mock-up experiment and the field experiment), to improve the design of the luminaires and decorations in the interior zone of the tunnel. The VR experiment and numerical simulation in lighting software were firstly conducted to determine the lighting parameters. Then the obtained lighting scheme was tested and validated in the real scenarios, where tunnel mock-up experiments and field experiments were conducted respectively. According to the results from the numerical simulations and VR experiments, the double-side luminance scheme is more conducive to driving safety and once the power of the luminaires is excessive low, the driver's attention variation rate is also unsatisfied. Moreover, the use of the anti-collision lower-side luminaires enhances the luminance level of the road surface and the sidewall to a certain level. The obtained lighting scheme was applied in a newly built tunnel in Hangzhou. The statistics of accidents data indicate that the installed luminaires and decorations, which are obtained from virtual simulation, can provide a considerably safe lighting environment. Ten months of accident statistics show that the breakdown rate in this tunnel was only 10% of the similar tunnels, and the accident rate was only 3%, thus the safety and environmental performance have been proved to be significantly improved

Effects of Sidewall Brightness on LED Lighting Environment and Visual Performance in Road Tunnels

The lighting design of a road tunnel focuses on the setting of pavement luminance. As for the tunnel sidewall luminance, it simply follows the principle of no less than 60% of the pavement luminance. In fact, the sidewall is one of the important components of the tunnel lighting environment; however, the impact of the improvement of sidewall brightness on the LED lighting environment in a tunnel has not attracted enough attention. In this study, the impact of the improvement of tunnel sidewall brightness on the lighting environment and visual characteristics of human eyes were analyzed based on the lighting experiments when the tunnel sidewalls were decorated with two different types of materials and illuminated by LED lamps with five different color temperatures. The test results show that the tunnel sidewall luminance will increase if the energy-storage and luminescent coating with high reflectance is decorated on tunnel sidewalls, and the pavement luminance increases with the increasing sidewall luminance. After the improvement of the sidewall and pavement luminance, the visible distance for a small object in the tunnel will increase to a certain extent. Furthermore, there is no discomfort for drivers during driving, and the changing of eye pupil diameter is relatively stable, which indicates that the increase in tunnel sidewall luminance has a positive effect on the visual performance of drivers

Plant demography data of Pinus massoniana measured from 2011-2013 in a degraded subtropical forest in Southeast China

Subtropical forest degradation induced by unreasonable disturbance is closely related to human activities in Southeast China, frequent small-scale logging by local people was the dominated disturbance regime in the forest over the past decades. The objective of this research is to evaluate the demographic consequences of logging for Pinus massoniana, a pioneer species, at the individual scales (survival, growth and fecundity) and the population scales (population growth rate and size distribution) in short-term period. Individual's size was combined with vital rates using various modeling approaches based on demographic data from three annual censuses (2011-2013). Integral projection model (IPM) was constructed and used to conduct comparative demographic analyses. The study was performed at Changting County (25°18′40″-26°02′05′N, 116°00′45′-116°39′20′E) located in the southern Wuyi Mountain in Southeast China. In 2011, one permanent plot (25°36′48″N, 116°26′18′E) approximately 30 × 30 m size was established, in which P. massoniana was the main dominant tree species. To ease data collection, the plot was subdivided into 36 subplots of 5 × 5 m. Measurements took place in the entire plot in July 2011, 2012 and 2013. For each individuals of P. massoniana, basal diameter, total height were measured and labelled during the first census. For those individuals with heights more than 1.5m, diameter at breast height (DBH) was also measured and recorded. In subsequent years, all labelled individuals were checked and re-measured, new recruits (seedlings that germination and establishment between census periods) within the plot were searched, labelled and measured. The number of produced pinecones over the studied periods were also recorded. For each individual, plant growth was calculated via subtracting the plant size in current year by the plant size in the previous year. The sample plot was logged in October 2012 after the second census. The meteorological data of Changting County (measurement site 58911 located in 25°38′20″N，116°27′28″E) was also recorded