•We firstly predicted the potential suitable areas of Magnolia wufengensi in the world.•The optimized Maxent model with climate, topography and soil variables was used.•The low temperature variables ...were the most important environmental variables.•The suitable area of M. wufengensis was mainly located in eastern and central Asia.•The suitable areas will be greatly reduced and shifted northeast in the future.
Magnolia wufengensis, a new species of the subgenus Magnolia, has extremely high ornamental and scientific value due to its rich morphological diversity. The wild population of M. wufengensis has a narrow habitat and a sparse population, and is in a critically endangered state. Currently, the potential suitable areas for the introduction of M. wufengensis and the limiting factors affecting its distribution and the response to global warming are unclear. Hence, an optimized MaxEnt model in the ENMeval package based on 49 M. wufengensis occurrence records and 16 environmental variables were used to simulate the potential suitable areas for M. wufengensis under current and future (2041–2080) climate change scenarios, including four representative concentration pathways (RCP2.6, RCP4.5, RCP6.0 and RCP8.5), to provide a scientific basis for the precise introduction, cultivation and expansion of suitable areas of M. wufengensis. The MaxEnt model was highly accurate, with an average training area under the curve (AUC) value of 0.9895 ± 0.0011 after 10 repetitions. The results indicated that the mean temperature of the coldest quarter (-6.75–14.31 °C), mean diurnal range (≤14.29 °C), min temperature of the coldest month (-13.73–10.77 °C), mean temperature of the warmest quarter (≥12.93 °C), precipitation of the wettest month (40.99–715.42 mm) and annual mean temperature (4.47–24.56 °C) were the most important environmental variables (threshold) limiting the distribution of suitable areas for M. wufengensis. In the current climate, areas of 146.15 × 104 km2, 119.88 × 104 km2 and 224.87 × 104 km2 were projected as potential areas with high, medium, and low suitability for M. wufengensis, respectively. These areas were mainly located in eastern and central Asia, the Mediterranean coast of southern Europe, and western America. Under future climate change, the potential suitable areas for M. wufengensis in the world will be greatly reduced, and the degree of fragmentation will increase. In addition, the reduction in suitable areas of different classes will be approximately 4.75%-39.14%, the suitable areas in western America and southern Europe will disappear, and the centroids of suitable areas for M. wufengensis will tends shift northeast.
Magnolia wufengensis is a new species of Magnolia L. and has considerable ornamental and economic value due to its unique characteristics. However, because of its characteristic of poor low ...temperature resistance, M. wufengensis is hardly popularization and application in the north of China. Furthermore, the mechanisms of gene regulation and signaling pathways involved in the cold-stress response remained unclear in this species. In order to solve the above-mentioned problems, we performed de novo transcriptome assembly and compared the gene expression under the natural (25 °C) and cold (4 °C) conditions for M. wufengensis seedlings.
More than 46 million high-quality clean reads were produced from six samples (RNA was extracted from the leaves) and were used for performing de novo transcriptome assembly. A total of 59,764 non-redundant unigenes with an average length of 899 bp (N50 = 1,110) were generated. Among these unigenes, 31,038 unigenes exhibited significant sequence similarity to known genes, as determined by BLASTx searches (E-value ≤1.0E-05) against the Nr, SwissProt, String, GO, KEGG, and Cluster of COG databases. Based on a comparative transcriptome analysis, 3,910 unigenes were significantly differentially expressed (false discovery rate FDR < 0.05 and |log
FC (CT/CK)| ≥ 1) in the cold-treated samples, and 2,616 and 1,294 unigenes were up- and down-regulated by cold stress, respectively. Analysis of the expression patterns of 16 differentially expressed genes (DEGs) by quantitative real-time RT-PCR (qRT-PCR) confirmed the accuracy of the RNA-Seq results. Gene Ontology and KEGG pathway functional enrichment analyses allowed us to better understand these differentially expressed unigenes. The most significant transcriptomic changes observed under cold stress were related to plant hormone and signal transduction pathways, primary and secondary metabolism, and photosynthesis. In addition, 113 transcription factors, including members of the AP2-EREBP, bHLH, WRKY, MYB, NAC, HSF, and bZIP families, were identified as cold responsive.
We generated a genome-wide transcript profile of M. wufengensis and a de novo-assembled transcriptome that can be used to analyze genes involved in biological processes. In this study, we provide the first report of transcriptome sequencing of cold-stressed M. wufengensis. Our findings provide important clues not only for understanding the molecular mechanisms of cold stress in plants but also for introducing cold hardiness into M. wufengensis.
•C emissions of stem respiration from 16, 25, 41 years old forest were estimated.•Air temperature and moisture are the primary climatic factor affecting RS.•The general model of RS using Q10 may ...underestimated the RS of young trees.•Q10 of RS peaked at a temperature within the range of 0–5°C.•Temperature-corrected Q10 of RS should be considered to estimate C emissions.
Stem respiration is a critical yet unavailable component of forest ecosystem carbon cycle dynamics. It is therefore necessary to study the variation in stem respiration at different time scales, especially regarding the response of the temporal variation in stem respiration to climatic factors. However, stem respiration is commonly measured only a few times a year during the daytime. In this study, we investigated the stem respiration of Larix principis-rupprechtii Mayr at different time scales, including hours, days, months, and seasons, and in forests of different ages as well as its connection with climatic factors using a soil carbon flux system (Li-8100) in North China during the growing season (May to September) and the non-growing season (October) from 2013 to 2015. The maximum daily stem respiration rate (abbreviated as RS) occurred between 14:00 and 18:00, and the minimum occurred between 4:00 and 8:00 (2.01–4.24, 1.71–4.25 and 1.02–1.72 vs. 10.83–2.93, 1.08–2.28 and 0.51–1.17μmolm−2s−1, respectively) for three forestry ages, which was in accordance with single-peak curves. The seasonal respiration was highest in late July and lowest in late October (3.84 vs. 0.27μmolm−2s−1, respectively). Calculation of RS indicated that the annual CO2 efflux per unit area was ranked by forest age as follows: 25 (11.53±2.08tha−1)>16 (7.45±1.02)>41 (4.87±0.66)years of age. The average annual Q10 values were 3.85 (16 years of age), 3.41 (25), and 2.23 (41). The Q10 value of the 16-year-old forest peaked (9.89) during low temperature (0–5°C) and subsequently decreased with increasing air temperature. These results not only clarify the response of RS to climatic factors at different time scales but also reveal the relationship between stem respiration in forests of different ages and their temperature sensitivity. These results suggest that the sensitivity of RS to temperature is negatively correlated with stand age and air temperature. Methodologically, incorporating stand age and air temperature into the conventional method would improve the accuracy of annual stem respiration estimates.
The CO
2
efflux of branches and leaves plays an important role in ecosystem carbon balance. Using a carbon flux system, the efflux of
Larix gmelinii
var.
principis-rupprechtii
(Dahurian larch) was ...investigated in 27 years (immature), 31 years (near-mature), and 47 years (mature) stands at diurnal, seasonal, and spatial scales (direction and height) as well as its connection with environmental factors from May to October 2020. Diurnal variation in efflux was a single peak, and the maximum occurring between 14:00 and 16:00. Seasonal variation also exhibited a single peak, with the maximum in late July and the minimum in early October. From May to September, efflux on the south side was the largest among the three stands, and mean values on the south side of 27 year-old, 31 year-old, and 47 year-old trees were 0.50, 0.97 and 1.05 μmol·m
–2
·s
–1
, respectively. The minimum occurred on the north side. Except for the maximum in July and September in the 27 year-old stand in the middle of the canopy, the maximum efflux in the upper canopy, and the means in the 27 year-old, 31 year-old, and 47 year-old stands were 0.49, 0.96 and 1.04 μmol·m
–2
·s
–1
, respectively; the minimum occurred in the lower canopy. Temperatures and relative humidity influenced seasonal variations in efflux. Seasonal variation in temperature sensitivity coefficient (Q
10
) was opposite that of temperature, increasing with decreasing temperature. At the spatial scale, maximum Q
10
occurred in the mid canopy. With the efflux and temperature data in different locations, it is possible to better estimate efflux variations in each stand.
Magonlia denudata is an important perennial tree species of the Magnoliaceae family, known for its ornamental value, resistance to smoke pollution and wind, role in air purification, and robust cold ...tolerance. In this study, a high-throughput transcriptome analysis of leaf buds was performed, and gene expression following artificial acclimation 22 °C, 4 °C and 0 °C, was compared by RNA sequencing.
Over 426 million clean reads were produced from three libraries (22 °C, 4 °C and 0 °C). A total of 74,503 non-redundant unigenes were generated, with an average length of 1173.7 bp (N50 = 1548). Based on transcriptional results, 357 and 235 unigenes were identified as being upregulated and downregulated under cold stress conditions, respectively. Differentially expressed genes were annotated using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes pathway analyses. The transcriptomic analysis focused on carbon metabolism and plant hormone signal transduction associated with cold acclimation. Transcription factors such as those in the basic helix-loop-helix and AP2/ERF families were found to play an important role in M. denudata cold acclimation.
M. denudata exhibits responses to non-freezing cold temperature (4 °C) to increase its cold tolerance. Cold resistance was further strengthened with cold acclimation under freezing conditions (0 °C). Cold tolerance genes, and cold signaling transcriptional pathways, and potential functional key components for the regulation of the cold response were identified in M. denudata. These results provide a basis for further studies, and the verification of key genes involved in cold acclimation responses in M. denudata lays a foundation for developing breeding programs for Magnoliaceae species.
The effects of varieties, concentrations, and number of applications of plant growth retardants (PGRs) on the morphological, physiological, and endogenous hormones of Magnolia wufengensis L.Y. Ma et ...L. R. Wang were assessed to obtain the most suitable dwarfing protocol for M. wufengensis and to provide theoretical support and technical guidance for the cultivation and promotion of this species. One-year-old M. wufengensis ‘Jiaohong No. 2’ grafted seedlings served as the experimental materials. In the first part of the experiment, three PGRs (uniconazole, paclobutrazol, prohexadione calcium), three concentrations (500, 1000, 1500 ppm), and three applications (one, three, and five applications) were applied in dwarfing experiments to perform L9 (34) orthogonal tests. In the second part of the study, dwarfing experiments were supplemented with different high uniconazole concentrations (0, 1500, 2000, 2500 ppm). Spraying 1500 ppm uniconazole five times achieved the best M. wufengensis dwarfing effect, related indicators of M. wufengensis under this treatment were better than other treatment combinations. Here, M. wufengensis plant height, internode length, scion diameter, and node number were significantly reduced by 56.9%, 62.6%, 72.8%, and 74.4%, respectively, compared with the control group. This treatment increased superoxide dismutase (SOD) activity by 66.0%, peroxidase (POD) activity by 85.0%, soluble protein contents by 43.3%, and soluble sugar contents by 27.6%, and reduced malondialdehyde (MDA) contents by 32.1% in leaves of M. wufengensis compared with the control. The stress resistance of M. wufengensis was enhanced. The treatment also reduced gibberellin (GA3) levels by 73.0%, auxin (IAA) by 58.0%, and zeatin (ZT) by 70.6%, and increased (abscisic acid) ABA by 98.1% in the leaves of M. wufengensis. The uniconazole supplementation experiment also showed that 1500 ppm was the optimal uniconazole concentration. The leaves exhibited abnormalities such as crinkling or adhesion when 2000 or 2500 ppm was applied. Given the importance of morphological indicators and dwarfing for the ornamental value of M. wufengensis, the optimal dwarfing treatment for M. wufengensis was spraying 1500 ppm uniconazole five times.
•ES was greater near the crown and the root than at the middle stem positions.•Nitrogen was the primary nutrient element affecting ES.•Sapwood width was the primary wood structure affecting ES.•C ...emissions from older tree was underestimated without the vertical variation in ES.•A model of ES for each stem position was established.
Stem CO2 efflux (ES) plays an essential role in the carbon balance of forest ecosystems. Therefore, it is necessary to study the vertical and seasonal variations in ES in forests with different ages, especially in response to factors associated with temperature, nutrients and wood structure. In this study, we investigated ES and its association with temperature factors using a carbon flux system (Li-8100A) at monthly intervals during the growing season (May to September) and the non-growing season (October) from 2013 to 2015. In addition, we collected data on nutrients and wood structure in August 2016 from 16- (young), 25- (immature), and 41-year-old (mature) Larix principis-rupprechtii Mayr stands in North China. Our analysis showed that the ES values at stem positions near the crown and the root system were generally higher than those in the middle and that the minimum ES values in July occurred at 2.0 m (3.61 μmol m−2 s−1), 3.0 m (2.42 μmol m−2 s−1), and 5.0 m (4.03 μmol m−2 s−1) in the young, immature, and mature forests, respectively. Air temperature and wood temperature influenced the vertical variation in ES, as did stem nitrogen concentration and sapwood width. Compared to the method that uses the vertical ES gradient to determine tree-scale CO2 effluxes for 16-, 25- and 41-year-old L. principis-rupprechtii forests, the method that uses the ES value at the 1.3-m stem position underestimated the CO2 effluxes by 5%, 6%, and 24%, respectively. The ES and Q10 models for each stem position for the three forest ages in this study can be used to accurately estimate tree-scale CO2 effluxes. These results not only clarified the relationships between the vertical variation in ES and temperature, nutrient content and wood structure, but also revealed the likely response mechanisms of ES to these factors. Methodologically, incorporating the vertical variation in ES and the associated drivers into conventional models would improve the accuracy of annual ES estimates.
To improving the understand of the accumulation pattern of soluble sugars in
Magnolia wufengensis
during natural cold acclimation, the dynamics of freezing tolerance, the content of various soluble ...sugars in the shoots of
M. wufengensis
seedlings treated with salicylic acid, and the correlation between them were analyzed from September 2017 to March 2018. Salicylic acid advanced the natural cold acclimation and ultimately enhanced mid-winter hardiness by promoting the accumulation of total soluble sugars. Improved freezing tolerance highly correlated with enhanced glucose, fructose, and raffinose accumulation. The enhanced accumulation of these sugars by elevated amylase, sucrose synthase, and sucrose-P-synthase activities may contribute to advanced natural cold acclimation.
Magnolia wufengensis is a newly discovered rare and endangered species endemic to China. The primary objective of this study is to find the most suitable species distribution models (SDMs) by ...comparing the different SDMs to predict their habitat distribution for protection and introduction in China under climate change. SDMs are important tools for studying species distribution patterns under climate change, and different SDMs have different simulation effects. Thus, to identify the potential habitat for M. wufengensis currently and in the 2050s (2041–2060) and 2070s (2061–2080) under different climate change scenarios (representative concentration pathways RCP2.6, RCP4.5, RCP6.0, and RCP8.5) in China, four SDMs, Maxent, GARP, Bioclim, and Domain, were first used to compare the predicted habitat and explore the dominant environmental factors. The four SDMs predicted that the potential habitats were mainly south of 40° N and east of 97° E in China, with a high distribution potential under current climate conditions. The area under the receiver operating characteristic (ROC) curve (AUC) (0.9479 ± 0.0080) was the highest, and the Kappa value (0.8113 ± 0.0228) of the consistency test and its performance in predicting the potential suitable habitat were the best in the Maxent model. The minimum temperature of the coldest month (−13.36–9.84 °C), mean temperature of the coldest quarter (−6.06–12.66 °C), annual mean temperature (≥4.49 °C), and elevation (0–2803.93 m), were the dominant factors. In the current climate scenario, areas of 46.60 × 104 km2 (4.85%), 122.82 × 104 km2 (12.79%), and 96.36 × 104 km2 (10.03%), which were mainly in central and southeastern China, were predicted to be potential suitable habitats of high, moderate, and low suitability, respectively. The predicted suitable habitats will significantly change by the 2050s (2040–2060) and 2070s (2060–2080), suggesting that M. wufengensis will increase in high-elevation areas and shift northeast with future climate change. The comparison of current and future suitable habitats revealed declines of approximately 4.53%–29.98% in highly suitable habitats and increases of approximately 6.45%–27.09% and 0.77%–21.86% in moderately and lowly suitable habitats, respectively. In summary, these results provide a theoretical basis for the response to climate change, protection, precise introduction, cultivation, and rational site selection of M. wufengensis in the future.
Urban heat island (UHI) attenuation is an essential aspect for maintaining environmental sustainability at a local, regional, and global scale. Although impervious surfaces (IS) and green spaces have ...been confirmed to have a dominant effect on the spatial differentiation of the urban land surface temperature (LST), comprehensive temporal and quantitative analysis of their combined effects on LST and surface urban heat island intensity (SUHII) changes is still partly lacking. This study took the plain area of Beijing, China as an example. Here, rapid urbanization and a large-scale afforestation project have caused distinct IS and vegetation cover changes within a small range of years. Based on 8 scenes of Landsat 5 TM/7ETM/8OLI images (30 m × 30 m spatial resolution), 920 scenes of EOS-Aqua-MODIS LST images (1 km × 1 km spatial resolution), and other data/information collected by different approaches, this study characterized the interrelationship of the impervious surface area (ISA) dynamic, forest cover increase, and LST and SUHII changes in Beijing’s plain area during 2009–2018. An innovative controlled regression analysis and scenario prediction method was used to identify the contribution of ISA change and afforestation to SUHII changes. The results showed that percent ISA and forest cover increased by 6.6 and 10.0, respectively, during 2009–2018. SUHIIs had significant rising tendencies during the decade, according to the time division of warm season days (summer days included) and cold season nights (winter nights included). LST changes during warm season days responded positively to a regionalized ISA increase and negatively to a regionalized forest cover increase. However, during cold season nights, LST changes responded negatively to a slight regionalized ISA increase, but positively to an extensive regionalized ISA increase, and LST variations responded negatively to a regionalized forest cover increase. The effect of vegetation cooling was weaker than ISA warming on warm season days, but the effect of vegetation cooling was similar to that of ISA during cold season nights. When it was assumed that LST variations were only caused by the combined effects of ISA changes and the planting project, it was found that 82.9% of the SUHII rise on warm season days (and 73.6% on summer days) was induced by the planting project, while 80.6% of the SUHII increase during cold season nights (and 78.9% during winter nights) was caused by ISA change. The study presents novel insights on UHI alleviation concerning IS and green space planning, e.g., the importance of the joint planning of IS and green spaces, season-oriented UHI mitigation, and considering the thresholds of regional IS expansion in relation to LST changes.
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