An Adaptive Shrinking Grid Search Chaotic Wolf Optimization Algorithm Using Standard Deviation Updating Amount

To improve the optimization quality, stability, and speed of convergence of wolf pack algorithm, an adaptive shrinking grid search chaotic wolf optimization algorithm using standard deviation updating amount (ASGS-CWOA) was proposed. First of all, a strategy of adaptive shrinking grid search (ASGS) was designed for wolf pack algorithm to enhance its searching capability through which all wolves in the pack are allowed to compete as the leader wolf in order to improve the probability of finding the global optimization. Furthermore, opposite-middle raid method (OMR) is used in the wolf pack algorithm to accelerate its convergence rate. Finally, “Standard Deviation Updating Amount” (SDUA) is adopted for the process of population regeneration, aimed at enhancing biodiversity of the population. The experimental results indicate that compared with traditional genetic algorithm (GA), particle swarm optimization (PSO), leading wolf pack algorithm (LWPS), and chaos wolf optimization algorithm (CWOA), ASGS-CWOA has a faster convergence speed, better global search accuracy, and high robustness under the same conditions.

Soil seed burial and competition with surrounding plants determine the emergence and development of seedling of an endangered species Horsfieldia hainanensis Merr. in China

Three well-conserved Horsfieldia hainanensis Merr. populations were used to investigate their soil seed bank and seedling regeneration characteristics and their relationship to environmental factors. The results showed that the seed reserves were low in the H. hainanensis soil seed bank (16.93~24.74 seed/m2). The distribution pattern for the seeds and seedlings in the H. hainanensis populations was aggregated, and they were mainly found around 2–3 m from the mother plant. The seeds in the litter layer and the 5–10 cm soil layer showed no vigor, and only 25.7%~33.3% of the total seeds in the 0–5 cm soil layer were viable affected by the high temperature and humidity, the animals’ eating and poisoning. Affected by the height and coverage of the surrounding herbaceous layer and shrub layer, the seedlings of H. hainanensis could not obtain enough light and nutrients in the competition, resulting in the survival competitiveness of 1- to 3-year-old (1–3a) seedlings in the habitat had been in a weak position and a large number of seedlings died. It would take at least four years for seedlings to develop under the current environmental constraints. It can be concluded that the low seed reserve in the soil seed bank and high mortality of seedlings of H. hainanensis lead to slow or even stagnation of population regeneration, which was an important reason for the endangered of H. hainanensis. Therefore, the next research focus is to explore the influence mechanism of environmental factors on seed germination and seedling growth of H. hainanensis.

Effect of Microenvironment on Species Distribution Patterns in the Regeneration Layer of Forest Gaps and Non-Gaps in a Subtropical Natural Forest, China

The aim of this study was to explore the effect of gap environmental factors on the plant population regeneration pattern in the Castanopsis kawakamii natural forest. We used the detrended canonical correspondence analysis (DCCA) method to study coupling relationships between species distribution in the regeneration layer and environmental factors. The results showed that: (1) The main environmental factors that influenced species distribution in the forest gaps and non-gaps were different, and the highest explanation rate of environmental factors was the soil temperature below the surface 10 cm (ST10); (2) The relationships between species distribution in the regeneration layer of the forest gaps and non-gaps were mainly restricted by environmental factors, given the environmental factors complied with the ecological niche hypothesis; and (3) For the endangered C. kawakamii population, there were positive and negative relationships between the environmental factors and the various species in the forest gaps and non-gaps, whilst the effects of such relationships were varied. Some management operations, including the creation of artificial gaps and adequate fertilization in the non-gaps, could more effectively promote the growth and regeneration of the C. kawakamii population.

An improved heat transfer search algorithm for unconstrained optimization problems

In this work, an improved heat transfer search (IHTS) algorithm is proposed by incorporating the effect of the simultaneous heat transfer modes and population regeneration in the basic HTS algorithm. The basic HTS algorithm considers only one of the modes of heat transfer (conduction, convection, and radiation) for each generation. In the proposed algorithms, however, the system molecules are considered as the search agents that interact with each other as well as with the surrounding to a state of the thermal equilibrium. Another improvement is the integration of a population regenerator to reduce the probability of local optima stagnation. The population regenerator is applied to the solutions without improvements for a pre-defined number of iterations. The feasibility and effectiveness of the proposed algorithms are investigated by 23 classical benchmark functions and 30 functions extracted from the CEC2014 test suite. Also, two truss design problems are solved to demonstrate the applicability of the proposed algorithms. The results show that the IHTS algorithm is more effective as compared to the HTS algorithm. Moreover, the IHTS algorithm provides very competitive results compared to the existing meta-heuristics in the literature. Highlights An improved Heat Transfer Search (HTS) algorithm is proposed. A novel population regenerator is integrated to the improved HTS. A set of 53 test functions is employed to test the performance of the proposed algorithm. The results are compared with several techniques in the literature.

Pruning treatment: A possible method for improving the conservation status of a Ellisella paraplexauroides Stiasny, 1936 (Anthozoa, Alcyonacea) population in the Chafarinas Islands?

In the present paper, the results of a four-year conservation study on the giant gorgonian Ellisella paraplexauroides in the Chafarinas Islands are reported. This species, currently protected in Spain, is present as isolated colonies or as a low number of them, except in the Chafarinas Islands, where higher densities can be found below a depth of 20 m. Nevertheless, as revealed by a previous study, a great number of colonies are partially covered by epibionts or totally dead. As a first objective of the present work, seven transects were performed in 2013 and 2014 to evaluate the percentage of colonies affected in areas that had not been previously sampled. Approximately between 35% and 95% of the colonies had different degrees of epibiosis or were dead. In 2015, ten transects were performed to specifically locate young colonies smaller than 15 cm, which could be indicative of population regeneration by sexual reproduction. The high number of dead colonies as well as the colonies covered by epibionts, together with the inexistence of young colonies, indicated a progressive decline of the study population. The last aim of the study consisted of testing a restoration action by means of pruning the affected colonies between 2015 and 2016. The results of this restoration action showed a substantial improvement of the colonies (growth of branches, production of new branches and a general increase in the health status of the colonies). Our results recommend the employment of this technique for the future conservation of this species in the Chafarinas Islands. Nevertheless, this is a pilot study, and further experiments with a large number of samples should be performed to truly understand the significance of this technique.