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Effects of Harvesting Methods on Primary and Net N Transformation Rates in Forest Soils
LANG Man, NIE Hao, LI Ping
, Available online  , doi: 10.12403/j.1001-1498.20220542
Objective To explore the nitrogen release and conservation capacity of forest soil under different harvesting methods, and reveal the impact of harvesting methods on forest soil N nutrient cycle. Method A laboratory incubation experiment was conducted to study the effects of selective cutting and clear cutting on primary and net N transformation rates in broad-leaved mixed forest soil in cold temperate zone, using 15N paired isotope labeling technique and FLUAZ numeric model. Result In the reserved belt without any cutting, soil gross N mineralization, net N mineralization, gross N immobilization, gross nitrification, and net nitrification rates were 4.16, 1.86, 2.32, 0.368, and 0.343 mg∙kg−1∙d−1, respectively. In comparison with the treatment of reserved belt, soil primary N mineralization rates of the selective cutting and clear cutting treatments significantly decreased by 32.2% and 61.8%, respectively, soil net N mineralization rates significantly decreased by 43.1% and 61.5%, respectively, and soil gross N immobilization rates significantly decreased by 23.3% and 63.4%. Selective cutting had no significant effects on primary and net nitrification rates in soil, while clear cutting significantly decreased soil gross and net nitrification rates by 23.6% and 33.3%, respectively. The correlation analysis indicated that soil organic C and water soluble organic C were the main factors influencing primary and net N mineralization and immobilization rates in soil, and pH was the main factor influencing primary and net nitrification rates in soil. Conclusion Our results indicate that the decrease of primary ammonium immobilization rate is greater than that of gross nitrification rate after clear cutting, leading to the significant increase of ratio of gn/ia and NO3/NH4+ in soil, which increases the risk of NO3 leaching. However, the ratio of gn/ia and NO3/NH4+ in soil under selective cutting is not significantly different from that of the reserved belt, which is a desirable way of forest harvesting.
Establishment of Plant Regeneration System from Internodes of Betula alnoides
WANG Huan, GUO Jun-jie, WANG Chun-sheng, YIN Hai-feng, ZENG Jie
, Available online  , doi: 10.12403/j.1001-1498.20230159
Objective To explore the optimal media components at stages for callus induction, adventitious bud differentiation, rooting induction of indirect organogenesis, a high-frequency regeneration system of Betula alnoides was established for providing theoretical evidence and technical support for genetic transformation and multiplication of elite cultivars of this species. Methods The internode stem segment of Betula alnoides TC2 clone was used to conduct callus induction, adventitious bud differentiation and rooting medium screening experiments, and the pre-culture conditions were optimized, revealing the fundamentals of callus induction stage. The effects of basic media, application of hormones, and dark culture at callus induction stage, hormone combination at adventitious bud differentiation stage, and preculture conditions on adventitious bud differentiation were assessed. Results (1) The suitable conditions for preculture were: 15 days under low illumination (1 000 lx), then 7 days in dark and 8 days under normal illumination (2 000 lx), and properly yellowing plantlets could be obtained under these conditions with the mean height and internode length reaching 6.57 cm and 3.07 cm, respectively; (2) The medium suitable for callus induction of internodes was WPB5 + 1.0 mg·L−1 TDZ + 0.2 mg·L−1 NAA + 20 sucrose + 5.8 g·L−1Agar (pH5.8) for the callus induction, and the optimal dark culture time was 15 days; (3) The medium suitable for callus differentiation was WPM + 0.8 mg·L−1 6-BA + 0.5 mg·L−1 GA3 + 30 sucrose + 5.8 g·L−1Agar (pH5.8); (4) Using the above optimal scheme, the differentiation rate and net proliferation coefficient of the internode segments were 88.89% and more than 6.2, respectively, and 56.8 adventitious buds were obtained eventually per preculture plantlet on average; and (5) The reasonable rooting medium was the Wood Plant Medium supplemented with 0.2 mg·L−1 NAA + 20 g·L−1 sucrose, and the rooting rate could reach 100% after 30 days. Conclusion A high-frequency regeneration system of B. alnoides is completely established with high stability and good repeatability in the study. It can not only has a high callus differentiation rate and proliferation coefficient, but also improves the efficiency of internode production. The findings can provide a technical support for tissue culture and future genetic improvement through genetic engineering of B. alnoides.
Dynamics and Stability of Biomass of Coniferous and Broad-leaved Mixed Forests in Northeast China
JIA Bo, WANG Xin-jie
, Available online  , doi: 10.12403/j.1001-1498.20230072
Objective To explore the driving factors of the dynamic processes of aboveground biomass of mixed forests in Northeast China for accurately understanding the forest services and functions. Methods Based on 110 fixed plots in Jingouling Forest Farm in Northeast China, forest dynamics processes from 1987 to 2017 were described. Piecewise structural equation models were used to assess the impact of forest structure, climate, topography and diversity on the dynamic processes (growth, recruitment and mortality) of biomass, and the effects of dynamic processes on stability were further explored. Result The results showed that the growth of biomass was positively affected by stand basal area (β=0.562), altitude(β=0.853), and mean annual temperature (β=0.820), and negatively correlated with the Gini coefficient of diameter at breast height (β=−0.274). The increment of tree recruitment was positively associated with altitude (β=0.913), mean annual temperature (β=0.944), and negatively related to the coefficient of variation of diameter at breast height (β=-0.233). The biomass loss was only significantly positively correlated with the stand basal area (β=0.467). In addition, this study also found that mortality was the most important factor affecting the biomass stability. Conclusion In general, altitude and MAT plays an important role in the biomass change. We should pay more attention to the situation of dead trees in the future for forest management.
Estimation and Uncertainty Analysis of Aboveground Carbon Storage of Pinus densata based on Random Forests and Monte Carlo
CAO Jun, ZHANG Jia-long, XIAO Qing-lin, WANG Fei-ping, HAN Xue-lian, HUANG Yi-jie
, Available online  , doi: 10.12403/j.1001-1498.20220603
Objective To study the model uncertainty induced by different types of variables on carbon storage estimation. Method Taking as the research object, Random forest joint Monte Carlo (RF-MC) was used to establish a carbon storage regression model of Shangri-La Pinus densata based on different variable combinations to determine the uncertainty of each model. Result (1) Spectral and plot data directly contributed to the estimation accuracy and uncertainty of the RF-MC model. (2) The model prediction introducing texture features was better than introducing DEM. (3) The RF-MC model that introduced both DEM and texture features performed the best (R2=0.892, RMSE=5.539 t·hm², MAE = 4.319 t·hm², rRMSE=18.7%). The model fit improved by 0.343 and the uncertainty of the model decreased by 19.43%. Conclusion The RF-MC method based on multiple characteristics performs well on carbon storage estimation. Different types of variables have certain impact on the accuracy and uncertainty of carbon storage estimation.
Effects of Desiccation on Anatomical Structure of Somatic Embryo and Expression of Cell Wall Remodelin g Gene of Picea asperata
LING Juan-juan, HU Ji-wen, WANG Jun-hui, AN San-ping, WANG Li-fang, XU Na, ZHU Tian-qing
, Available online  , doi: 10.12403/j.1001-1498.20230157
Objective To explore the effects of desiccation on the anatomical structure of somatic embryo of Picea asperata, identify the key genes that lead to the changes in anatomical structure, and preliminarily explore the reasons why desiccation promotes somatic embryo germination. Method The high embryonic cell line of Picea asperata was used to induce somatic embryogenesis. The phenotypic observation and germination rate of somatic embryos were determined after desiccation treatment for different time. Ultra depth of field microscope, scanning electron microscope and transmission electron microscope were used to observe the differences of tissue and cell structure and morphology between desiccated somatic embryos and non-desiccated somatic embryos, and transcriptome sequencing was combined to analyze the changes of gene expression between desiccated and non-desiccated somatic embryos. Results The somatic embryo morphology of spruce was significantly changed after desiccation. The radicle turned red and the cotyledon turned green after desiccation. Microscopic observation showed that the cells of the desiccated somatic embryo were shrunken and irregularly distributed. At high magnification, the cell wall was no longer rigid, showing a relaxed and twisted state. Transcriptome analysis found that several transcripts of XTHs, EXPAs and PMEs involved in cell wall remodeling and affecting the mechanical properties of cell walls were significantly differentially expressed between desiccated and non-desiccated somatic embryos, and their expressions were mostly up-regulated, which was consistent with the results of microscopic observation on the morphological changes of desiccated somatic embryos. These genes may synergically regulate the process of desiccation and affect the germination of somatic embryos. Conclusion The differential expression of cell wall remodeling genes during desiccation leads to the relaxation of somatic embryo cell wall, the disappearance of rigid structure, and the release of cell differentiation and growth restrictions, which is a potential reason for desiccation to promote somatic embryo germination.