Continuous planting Eucalyptus plantations in subtropical China: Soil phenolic acid accumulation and adsorption physiognomies

Abstract

As phenolic acids accumulated in monocropping plantations, their allelopathic effects caused the soil’s fertility to decline and productivity to decrease. The effects of stand age and generational turnover of phenolic acids in soil remain unclear. Therefore, we conducted an experiment to examine the changes in phenolic acid content and accumulation characteristics in soils from Eucalyptus plantations in terms of planting years and generations. Soils were collected from three Eucalyptus plantations: a 6-year-old first-generation plantation (6a1g), 9-year-old first-generation plantation (9a1g) and 6-year-old second-generation plantation (6a2g). Seven phenolic acids were identified from different soil samples by high-performance liquid chromatography. In addition, exogenous phenolic acids were added to the soil samples to study the kinetics as well as the adsorption and desorption characteristics of soils. The total of seven phenolic compounds in 6a1g (38.451 μg g–1) was higher than that of the 9a1g and 6a2g soils, and the total of 6a2g (27.257 μg g–1) was higher than that of the 9a1g (15.536 μg g–1). In the tested soil, the p-hydroxybenzoic acid accounted for 51.6% (for 6a1g), 51.1% (for 9a1g) and 33.5% (for 6a2g) of the total amount of the seven phenolic acids, the p-hydroxybenzoic may have had a higher allelopathic capacity in these Eucalyptus plantation soils. Soil bulk density showed a strong positive correlation with vanillic and ferulic acids, and SOM also had an extremely positive correlation with p-hydroxybenzoic and coumalic acids. The findings demonstrated that the adsorption and desorption rates and amounts of each phenolic acid in the soil of 6a1g were higher than those in the soil of 9a2g and 6a2g using both a kinetic adsorption experiment and isothermal adsorption and desorption experiments. But among the three soils, 9a1g soil had the lowest adsorption rate, which resulted in the lowest accumulation capacity. It is noticed that the Pseudo-second-order kinetic model can be used to describe the kinetic adsorption better than the Pseudo-first-order kinetic model and the Elovich model, and the Freundlich model could fit the desorption isotherms better than the adsorption isotherms. However, more study of this phenomenon is essential to better understanding its mechanisms and how they function in order to address issues with soil degradation in future intergenerational Eucalyptus plantings.

Effect of Continuous Planting on Tree Growth Traits and Growth Stress in Plantation Forests of Eucalyptus urophylla × E. grandis

“…In China, some fast-growing timber tree species are planted continuously on the same forestlands, such as Chinese fir and Eucalyptus, which are representative species of successive monocropping that has gone on for multiple generations [33]. Table 3 presents the longitudinal growth strain and mean absolute values for the four directions of the sample trees in the southeast and northwest of the three generations.…”

“…(2) forests II and III sprouts grow from the root base, and as trees respond to environmental factors (light, wind, and slope) and forestry factors (planting density, interplanting, pruning), growth strain gradually accumulates; or (3) forests II and III may have formed cells characteristic of tension wood, i.e., a gelatinous layer, at sites of high strain eastward and northward, and the anatomical characteristics and chemical properties of these cells influence the magnitude of growth strain [44]. The accumulation of phenolic and allelopathic factors in soil may also account for rising growth stress in continuous planting [33].…”

A Systematic Review on the Continuous Cropping Obstacles and Control Strategies in Medicinal Plants

“…Several scientists have extracted and identified allelochemicals from various plants in recent years, primarily from monoterpenes, organic acids, flavonoids, phenolic acids, terpenoids, plant volatiles, and coumarins [84]. Phenolic acids, being the most extensively researched and actively studied compounds, have emerged as a central focus in allelopathy research concerning soil diseases [85]. Numerous studies have revealed that phenomena such as allelopathy or autotoxicity might have a negative impact on continuously grown crops [86].…”

Impact of Simulated Acid Rain on Soil Base Cations Dissolution between Eucalyptus Pure Plantations and Eucalyptus–Castanopsis fissa Mixed Plantations

“…For the timber and textile industries, Eucalyptus plantations have the potential to be a valuable resource. However, to achieve high productivity and increase economic income, forest management, such as the continuous planting of pure plantations [13], application of chemical fertilizers, and short rotation management, were widely applied to Eucalyptus plantations in most countries (including China). This caused soil acidification, fertility decline, and decreased woodland productivity, threatening the sustainability of soil fertility [14].…”