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Light use efficiency (LUE) models have been widely used to estimate terrestrial gross primary production (GPP). However, the estimation of GPP still has large uncertainties owing to an insufficient understanding of the complex relationship between water availability and photosynthesis. The plant water stress index (PWSI), which is based on canopy temperature, is very sensitive to the plant stomatal opening and has been regarded as a good indicator for monitoring plant water status at the regional scale. In this study, we selected a cork oak plantation in northern China with an obvious seasonal drought as the research object. Using the ground-observed data, we evaluated the applicability of the LUE models with typical water stress scalars (MOD17, MODTEM, EC-LUE, ECM-LUE, SM-LUE, GLO-PEM, and Wang) in a GPP simulation of the cork oak plantation and explored whether the model's accuracy can be improved by applying PWSI to modify the above models. The results showed that among the seven LUE models, the water stress scalar had a greater impact on the model's performance than the temperature stress scalar. On sunny days, the daily GPP simulated by the seven LUE models was poorly matched with the measured GPP, and all models explained only 23–52% of the GPP variation in the cork oak plantation. The modified LUE models can significantly improve the prediction accuracy of the GPP and explain 49–65% of the variation in the daily GPP. On cloudy days, the performance of the modified LUE models did not improve, and the evaporative fraction was more suitable for defining the water stress scalar in the LUE models. The ECM-LUE and the modified GLO-PEM based on PWSI had optimal model structures for simulating the GPP of the cork oak plantation under cloudy and sunny days, respectively. This study provides a reference for the accurate prediction of GPP in terrestrial ecosystems in the future. [ABSTRACT FROM AUTHOR]

Amur cork-tree bark is a natural medicine in China with a large market, whereas confusion about its origin limits its cultivation and commercial value. To trace the origin, the stable isotope ratios (δ 13C, δ 15N, δ 2H, and δ 18O) and multiple elements (As, Hg, Al, Ca, Fe, K, Mg, Na, Cr, Cd, Pb, Be, Cu, Zn, Sr, and Ba) of 83 batches of Amur cork-tree bark samples from 7 habitats were determined by stable isotope mass spectrometry and inductively coupled plasma mass spectrometry. The results showed that the two-dimensional combination of δ 13C and δ 15N in the scatter diagram of stable isotopes could obviously distinguish Amur cork-tree bark from Sichuan Province from other producing areas, and multielement radar map analysis could also be used to distinguish Amur cork-tree bark from different geographical sources. In this article, the data of stable isotope ratios and multielement content were combined for principal component analysis (PCA), linear discriminant analysis (LDA) and orthogonal partial least square discriminant analysis (OPLS-DA). The results of principal component analysis showed that all samples could be preliminarily distinguished. The prediction model established and verified by linear discriminant analysis realized 100% accurate classification for known samples. The correct rate of analysis and prediction for unknown samples was 94.5%. The effective feature discriminant markers of Amur cork-tree bark caused by VIP > 1 (Ca, K, Pb, Mg, Cr, As) were found by orthogonal partial least square discriminant analysis. It could accurately identify Amur cork-tree bark from different producing areas. [Display omitted] • The stable isotopes and multi-elements of Amur Cork-tree Bark were first determined. • The method was fisrt used to study the traceability of Amur Cork-tree Bark. • A set of traceability model was established for traceability of Amur Cork-tree Bark. • The method has guiding significance for the cultivation and clinical application. [ABSTRACT FROM AUTHOR]

Compatible taper and volume models were created for Quercus variabilis Blume (cork oak) forests in North China. 174 trees were felled to obtain stem analysis data. Linear mixed effects analyses were used in modelling. Firstly, a bark thickness model was built. Then diameter at breast height over bark (DBHob) for the inner layers of the 174 trees could be calculated, based on which a total volume model was built. The estimated volume and a specific parameter restriction were then substituted into a polynomial taper model, finally the taper model was fitted and compatible taper and volume models were obtained. Four sets of models based on different data sets were separately built and compared through coefficients of determination (R²), root mean square error (RMSE), value of Akaike's information criterion (AIC), residuals plots and histograms of residuals. Models based on data of the analyzed stems without ramicorns and simultaneously with relative diameter under 1.5 were chosen as the most precise. Further testing of the chosen models using the jackknife method for the bark thickness and total volume models and a validation data set for the taper model verified that those models can be used to predict bark thickness, diameter at a specific point along the stem, merchantable volume and total stem volume of cork oak forests in North China within specific tree diameter at breast height and height ranges. [ABSTRACT FROM AUTHOR]

Quercus variabilis (Chinese cork oak) has a substantial cork in the periderm that regenerates if removed, allowing a potential sustainable production. Samples of virgin and reproduction cork of Q. variabilis from China were characterized and compared with Q. suber cork. Virgin and reproduction cork are chemically very similar: on average 0.9% ash, 9.2% extractives, 37.8% suberin, and 28.5% lignin. The suberin composition of Q. variabilis cork is reported for the first time. It is composed mostly by saturated ω-hydroxyacids and substituted ω-hydroxyacids, including mainly 22-hydroxydocosanoic acid (20–23% of the total compounds) and 18-hydroxy-9-octadecenoic acid (17–22%). Comparison with Q. suber cork shows differences, stressing that suberin composition is species specific. The lipophilic extractives include mainly triterpenes (48.6–56.9%) especially friedelin and betulinic acid. Q. variabilis cork has the typical cellular characteristics of cork tissues with radially aligned cells without intercellular voids. Cell wall undulations were conspicuous, especially in virgin cork. Q. variabilis cork may be a complementary raw-material to Q. suber cork for agglomerated products. Despite similarities with the commercial cork, Q. variabilis cork has differences that impact unfavourably on properties e.g. higher density and compressive strength. [ABSTRACT FROM AUTHOR]

• CWSI is first examined to detect water status of ecosystem in the humid conditions. • The CWSI dTe fail to monitor water status of cork oak plantation. • The work discussed the reason for the failure in establishment of NWSB. • The CWSI dTt could monitor water status in the plantation. • The optimum monitoring time was 13:00-14:00. The crop water stress index based on canopy–air temperature differences (CWSI dT) is an appropriate index for monitoring the water status of croplands but is rarely used to evaluate the water status of forest ecosystems. In this study, we selected a cork oak plantation in the lithoid mountain area of northern China as the research object and observed the canopy temperature (T c), actual evapotranspiration (ET a), and meteorological factors of the plantation continuously and synchronously during the period of canopy closure (May–September) in 2020 and 2021. Taking the crop water stress index based on the ratio of ET a to potential evapotranspiration (CWSI et) as a standard, the applicability of CWSI dT for detecting water status in the plantation was evaluated. The results showed that, under well-watered conditions, the canopy–air temperature differences (dT) and the canopy surface transpiration rate were both controlled by the net radiation received by the canopy surface (R nc), and the warming effect of R nc masked the cooling effect of latent heat on dT , resulting in a failure establishment of the non-water-stressed baseline in the plantation. Therefore, the empirical CWSI dT (CWSI dTe) is not suitable for evaluating the water status in this plantation. However, the theoretical CWSI dT (CWSI dTt), based on the energy balance and Penman–Monteith equation, captured daily variations in the water status in our plantation and showed a significant linear correlation with the measured relative available water content in the root zone (R2 = 0.59, P < 0.01) and CWSI et (R2 = 0.75, P < 0.01). The CWSI dTt showed an upward trend during the day, and midday (13:00−14:00) was the optimal time to measure dT for detecting the daily water status of the plantation. The CWSI dTt provides an effective, sensitive, and non-contact method of assessing daily water status changes in the cork oak plantation. [ABSTRACT FROM AUTHOR]

Root deformation is a common challenge in container seedlings especially for vigorous-rooted tree species. The issue is significant for Chinese cork oak ( Quercus variabilis Blume.) which is grown in cost-effective polybags. In this study we examined how copper root pruning and radicle pruning (1/3 or 2/3 of radicle length) individually and together (1/3 radicle pruning in combination with copper root pruning) affected root architecture, growth and nutrient storage of nursery seedlings, and survival, growth performance and nutrient status during the first outplanting season. Copper root pruning failed to reduce root spiraling, and decreased total root length and surface area by decreasing root length and surface area of roots with diameter <5 mm. In contrast, radicle pruning decreased root deformation and induced taproot formation. However, intensity of radicle pruning impacted seedling size at planting and 2/3 radicle pruning decreased height and stem dry mass relative to the control. Root effects of combination (radicle plus copper root pruning) treatment on root development were not superior to 1/3 radicle pruning. Combination treatment decreased roots with diameter <2 mm. Overall 1/3 radicle pruning has the best potential to modify root development for vigorous-rooted Chinese cork oak seedlings grown in polybags. [ABSTRACT FROM AUTHOR]

Aims: Fine root is an important part of the forest carbon cycle. The growth of fine roots is usually affected by forest intervention. This study aims to investigate the fine root mass, production, and turnover in the disturbed forest. Methods: The seasonal and vertical distributions of fine root (diameter ≤2 mm) were measured in a Chinese cork oak ( Quercus variabilis Blume) forest. The biomass and necromass of roots with diameters ≤1 mm and 1-2 mm in 0-40 cm soil profiles were sampled by using a sequential soil coring method in the stands after clear cutting for 3 years, with the stands of the remaining intact trees as the control. Results: The fine root biomass (FRB) and fine root necromass (FRN) varied during the growing season and reached their peak in August. Lower FRB and higher FRN were found in the clear cutting stands. The ratio between FRN and FRB increased after forest clear cutting compared with the control and was the highest in June. The root mass with diameter ≤1 mm was affected proportionately more than that of diameter 1-2 mm root. Clear cutting reduced FRB and increased FRN of roots both ≤1 mm and 1-2 mm in diameter along the soil depths. Compared with the control, the annual fine root production and the average turnover rate decreased by 30.7 % and 20.7 %, respectively, after clear cutting for 3 years. The decline of canopy cover contributed to the dramatic fluctuation of soil temperature and moisture from April to October. With redundancy discriminate analysis (RDA) analysis, the first axis was explained by soil temperature (positive) and moisture (negative) in the control stands. Aboveground stand structure, including canopy cover, sprout height, and basal area, influenced FRB and FRN primarily after forest clear cutting. Conclusions: This study suggested that the reduction of fine root biomass, production, and turnover rate can be attributed to the complex changes that occur after forest intervention, including canopy damage, increased soil temperature, and degressive soil moisture. [ABSTRACT FROM AUTHOR]