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Aim of study: Quercus variabilis (Chinese cork oak) reproduces asexually and sexually. This study aimed to determine the status and growth of asexual and sexual recruits of Q. variabilis in different forest recovery stages.Area of study: Three selective logged stands and one unlogged stand in Q. variabilis forest, Shaanxi Province, China. Material and methods:Origin, number, basal diameter, height and size structure of Q. variabilis shoots (height ≤200 cm) were investigated in the plots of 5, 10, and 20-years post-logging stands and unlogged stand. Effects of recovery stage on the density and growth of the three original recruits (stump sprouts, stem base sprouts and true seedlings) were analysis by One-way ANOVA.Main results: Sprouts dominated logged stands, whereas true seedlings dominated unlogged stand, stem base sprouts only existed in 20-years post-logging and unlogged stands. Stump sprout density and sprout number per stump both declined with extended post-logging time. True seedlings density increased from 7 to 20 shoots/100 m 2 as the postlogging time extended, and peaked in unlogged stand (94 shoots/100 m 2 ). An ongoing size structure was observed in true seedlings in all stands. Stump sprouts were taller and greater than true seedlings.Research highlights: Stump sprouts contributed more to Q. variabilis forest recovery in the early stage after disturbance. The contribution of true seedlings was limited in the same stage, but they were beneficial for population long-term development. Stem base sprouts were most likely to be a survival strategy rather than a reproductive strategy.

This study aims to detect the variety of fine root growth with branch orders in response to forest cutting. The branching ratio (R b ), root morphological indices, and biomass of up to 3 branch orders of fine roots were investigated from 2 soil depths (0 cm to 10 cm and 10 cm to 20 cm) in Chinese cork oak (Quercus variabilis Blume) plots 1 and 3 years after forest cutting, compared with those of intact trees as the control. The number of fine roots was lower in the managed plots than in the control, particularly in the first-order roots. After 1 year of cutting, the proportion of the first-order roots decreased significantly, whereas the proportion of the second-order and third-order roots increased. R b decreased significantly after forest management in the 0-10 cm soil depth of plots after 1 year of cutting. The fine roots in the plots after cutting exhibited less root length density, lower specific root length, less surface area, and higher tissue density compared with those in control plots. The mean root diameter showed no significant change. The average biomass of the first 3 orders of roots in the plots 1 and 3 years after cutting was 72% and 83% of that of the control plot, respectively. The reduction of fine root growth was influenced mainly by the lack of photosynthesis in the managed forest.

Aim of study: Quercus variabilis is a sclerophyllous oak with strong resprouting capabilities and whose regeneration is facilitated by the development of stump shoots following disturbance. During secondary forest regeneration, fine roots are important organs relative to changes in stand characteristics. Here, we aimed to provide novel insights into the chemical composition variations in roots with seasonality and root order hierarchy in a Q. variabilis forest at different periods of regeneration.Area of study: The forest is located next to the Baxianshan National Reserve in the southern part of the Yanshan Mountains, Tianjin, China.Materials and methods: Six plots were established in stands with either eight or 40 years of regeneration for the repeated sampling of fine roots during the growing season of 2019. All roots were classified by branch order. The first three root orders were collected to analyse the concentrations of nonstructural carbohydrate, carbon, and nitrogen.Main results: Short-term regeneration stands showed a reduction in soil moisture and an increase in soil temperature because of the lower canopy cover, compared to long-term stands. Soluble sugar and starch were lower in roots of short-term stands than in those of long-term stands, and the decreasing ratio of both parameters was observed in short-term stands. Less carbon and greater nitrogen concentrations of fine roots were found in short-term stands than in long-term stands, which resulted in weaker C/N ratio values. Nonstructural carbohydrate was stored more in higher order roots than terminal roots and presented greater sensitivity to forest regeneration. Redundancy discriminate analysis demonstrated that the nonstructural carbohydrate concentrations in roots were affected positively by canopy cover and negatively by soil temperature.Research highlights: The seasonal dynamics and branch allocation of chemical reserves in fine roots varied in the different periods of forest regeneration because of the discrepancy between the canopy cover and soil traits. Less nonstructural carbohydrate and a lower C/N ratio at the onset of forest regeneration may elevate the risk of root death.Keywords: soluble sugar; starch; forest regeneration; root order; C/N ratio; redundancy discriminate analysis.