Tree Species In Subtropical Forest Research Articles

Effects of drought and moisture stress on the growth and ecophysiological traits of Schima superba seedlings.

Changes in rainfall patterns are important environmental factors affecting plant growth, especially when larger precipitation events and prolonged drought periods occur in subtropical regions. There are many studies on how drought reduces plant biomass through drought-sensitive functional traits, but how excess water affects plant growth and ecophysiology is still poorly understood. Therefore, a greenhouse experiment was conducted on Schima superba (Theaceae), a dominant tree species in subtropical forests and commonly used in forestry, in a closed chamber under control (25% soil water content (SWC) as in local forests), drought stress (D, 15% SWC) and moisture stress (W, 35% SWC). Plant growth and ecophysiological traits related to morphology, leaf gas exchange, water potential and structural traits were measured. Compared to control, S. suberba under dry conditions significantly decreased its aboveground biomass, photosynthetic rate (A), leaf water potential and nitrogen use efficiency, but increased intrinsic water use efficiency, root to shoot ratio and specific root length. S. superba under wet conditions also significantly decreased its total biomass, aboveground biomass and specific root length, while W had no effect on A and leaf water potential. Our results indicate that S. superba shows a decrease in carbon gain under drought stress, but less response under wet conditions. This emphasizes the need to consider the strength and frequency of rainfall pattern changes in future studies because rainfall may either alleviate or intensify the effects of drought stress depending on the moisture level, thus suitable water conditions is important for better management of this tree species in subtropical China.

Comparison of Algorithms and Optimal Feature Combinations for Identifying Forest Type in Subtropical Forests Using GF-2 and UAV Multispectral Images

The composition and spatial distribution of tree species are pivotal for biodiversity conservation, ecosystem productivity, and carbon sequestration. However, the accurate classification of tree species in subtropical forests remains a formidable challenge due to their complex canopy structures and dense vegetation. This study addresses these challenges within the Jiangxi Lushan National Nature Reserve by leveraging high-resolution GF-2 remote sensing imagery and UAV multispectral images collected in 2018 and 2022. We extracted spectral, texture, vegetation indices, geometric, and topographic features to devise 12 classification schemes. Utilizing an object-oriented approach, we employed three machine learning algorithms—Random Forest (RF), k-Nearest Neighbor (KNN), and Classification and Regression Tree (CART)—to identify 12 forest types in these regions. Our findings indicate that all three algorithms were effective in identifying forest type in subtropical forests, and the optimal overall accuracy (OA) was more than 72%; RF outperformed KNN and CART; S12 based on feature selection was the optimal feature combination scheme; and the combination of RF and Scheme S12 (S12) yielded the highest classification accuracy, with OA and Kappa coefficients for 2018-RF-S12 of 90.33% and 0.82 and OA and Kappa coefficients for 2022-RF-S12 of 89.59% and 0.81. This study underscores the utility of combining multiple feature types and feature selection for enhanced forest type recognition, noting that topographic features significantly improved accuracy, whereas geometric features detracted from it. Altitude emerged as the most influential characteristic, alongside significant variables such as the Normalized Difference Greenness Index (NDVI) and the mean value of reflectance in the blue band of the GF-2 image (Mean_B). Species such as Masson pine, shrub, and moso bamboo were accurately classified, with the optimal F1-Scores surpassing 89.50%. Notably, a shift from single-species to mixed-species stands was observed over the study period, enhancing ecological diversity and stability. These results highlight the effectiveness of GF-2 imagery for refined, large-scale forest-type identification and dynamic diversity monitoring in complex subtropical forests.

Response of leaf functional traits to soil nutrients in the wet and dry seasons in a subtropical forest on an island.

Island ecosystems often have a disproportionate number of endemic species and unique and fragile functional characteristics. However, few examples of this type of ecosystem have been reported. We conducted a comprehensive field study on Neilingding Island, southern China. The leaf samples of 79 subtropical forest tree species were obtained and their functional traits were studied in the dry and wet seasons to explain the relationships between plant functional traits and soil nutrients. We found a greater availability of soil moisture content (SMC) and nutrients in the wet season than in the dry season. The values of wet season soil available phosphorus (5.97 mg·kg-1), SMC (17.67%), and soil available potassium (SAK, 266.96 mg·kg-1) were significantly higher than those of the dry season. The leaf dry matter content, specific leaf weight, leaf density, leaf total carbon, leaf total nitrogen, leaf total calcium, and the N/P and C/P ratios of leaves were all significantly higher in the dry season than in the wet season, being 18.06%, 12.90%, 12.00%, 0.17%, 3.41%, 9.02%, 26.80%, and 24.14% higher, respectively. In contrast, the leaf area (51.01 cm2), specific leaf area (152.76 cm2·g-1), leaf water content (0.59%), leaf total nitrogen (1.31%), leaf total phosphorus (0.14%), and leaf total magnesium (0.33%) were much lower in the dry season than in the wet one. There were significant pairwise correlations between leaf functional traits, but the number and strength of correlations were significantly different in the dry and wet seasons. The SAK, soil total phosphorus (STP), and pH impacted plant leaf functional traits in the dry season, whereas in the wet season, they were affected by SAK, STP, pH, and NO3- (nitrate). Both soil nutrients and water availability varied seasonally and could cause variation in a number of leaf traits.

Vein hierarchy mediates the 2D relationship between leaf size and drought tolerance across subtropical forest tree species.

Previous studies have observed a 2D relationship (i.e. decoupled correlation) between leaf size (LS) and leaf economics as well as a tight correlation between leaf economics and drought tolerance. However, the underlying mechanism maintaining the relationship between LS and drought tolerance remains largely unknown. Here, we measured LS, water potential at 50% loss of hydraulic conductance, hydraulic safety margin and different orders of vein traits across 28 tree species in a subtropical forest in Southern China. We found that LS and drought tolerance were in two independent dimensions (R2=0.00, P>0.05). Primary and secondary vein traits (i.e. vein diameter and density) explained the variation of LS, with R2 ranging from 0.37 to 0.70 (all Ps<0.01), while minor vein traits accounted for the variation of leaf drought tolerance, with R2 ranging from 0.30 to 0.43 (all Ps<0.01). Our results provide insight into the 2D relationship between LS and drought tolerance and highlight the importance of vein hierarchy in plant leaf functioning.

Community structure of soil fauna under different tree species in subtropical forests

Soil fauna play an important role in key functions of ecosystem such as material cycling. Litter quality and microenvironment of different tree species may regulate soil fauna community structure. In this study, we investigated soil fauna community structure, the differences of taxonomic and functional groups, and the regulatory factors under eight dominant tree species in August 2022. We captured 567 soil fauna (except for termites and ants), belonging to 3 phyla, 10 classes, 26 orders, and 99 families, with Achipteriidae, Trygoniidae, Poduridae, and Isotomidae as the dominant species. Tree species significantly affected soil fauna abundance, following an order: Michelia macclurei > Elaeocarpus decipiens > Castanopsis carlesii > Cunninghamia lanceolata > Lindera communis > Schima superba > Pinus massoniana > Liquidambar formosana. However, the richness, evenness, and diversity of soil fauna under different tree species were significantly different. Richness and diversity of M. macclurei, C. lanceolatas soil fauna were relatively high, while L. formosana, C. carlesii were relatively low. The evenness of meso-microfauna of L. formosana was the highest, which was significantly higher than that of M. macclureis and E. decipiens. The evenness of macrofauna and total soil fauna was not significantly different among the eight tree species. In addition, the abundance of omnivores and herbivores soil fauna was relatively high under M. macclurei, but relatively low under E. decipiens. The abundance of saprophages and predators soil fauna of E. decipiens, M. macclurei was higher than L. formosana, while saprophages was mainly meso-microfauna. Results of redundancy analysis showed that litter N, C:N, and K were the main factors affecting soil fauna community structure. The results indicated that the tree species with thicker litter layer and higher N and K contents may be conducive to enhancing the diversity of soil fauna community and affecting the distribution of different functional groups, thus contributing to the maintenance of forest biodiversity.

Dynamic changes of the contents of photoprotective substances and photosynthetic maturation during leaf development of evergreen tree species in subtropical forests.

Many studies have investigated the photoprotective and photosynthetic capacity of plant leaves, but few have simultaneously evaluated the dynamic changes of photoprotective capacity and photosynthetic maturation of leaves at different developmental stages. As a result, the process between the decline of photoprotective substances and the onset of photosynthetic maturation during plant leaf development are still poorly understood, and the relationship between them has not been quantitatively described. In this study, the contents of photoprotective substances, photosynthetic pigment content and photosynthetic capacity of leaves at different developmental stages from young leaves to mature leaves were determined by spatio-temporal replacement in eight dominant tree species in subtropical evergreen broadleaved forests. The correlation analysis found that the data sets of anthocyanins, flavonoids, total phenolics and total antioxidant capacity were mainly distributed on one side of the symmetry axis (y=x), while the data sets of flavonoids, total phenolics and total antioxidant capacity were mainly distributed on both sides of the symmetry axis (y=x). In addition, the content of photoprotective substances in plant leaves was significantly negatively correlated with photosynthetic pigment content and photosynthetic capacity but was significantly positively correlated with dark respiration rate (Rd). When chlorophyll accumulated to ~50% of the final value, the photoprotective substance content and Rd of plant leaves reached the lowest level, and anthocyanins disappeared completely; in contrast, the photosynthetic capacity reached the highest level. Our results suggest that anthocyanins mainly play a light-shielding role in the young leaves of most plants in subtropical forests. In addition, 50% chlorophyll accumulation in most plant leaves was the basis for judging leaf photosynthetic maturity. We also believe that 50% chlorophyll accumulation is a critical period in the transition of plant leaves from high photoprotective capacity (high metabolic capacity, low photosynthetic capacity) to low photoprotective capacity (low metabolic capacity, high photosynthetic capacity).

Tree Species Classifications of Urban Forests Using UAV-LiDAR Intensity Frequency Data

The accurate classification of tree species is essential for the sustainable management of forest resources and the effective monitoring of biodiversity. However, a literature review shows that most of the previous unmanned aerial vehicle (UAV) light detection and ranging (LiDAR)-based studies on fine tree species classification have used only limited intensity features, accurately identifying relatively few tree species. To address this gap, this study proposes developing a new intensity feature—intensity frequency—for the LiDAR-based fine classification of eight tree species. Intensity frequency is defined as the number of times a certain intensity value appears in the individual tree crown (ITC) point cloud. In this study, we use UAV laser scanning to obtain LiDAR data from urban forests. Intensity frequency features are constructed based on the extracted intensity information, and a random forest (RF) model is used to classify eight subtropical forest tree species in southeast China. Based on four-point cloud density sampling schemes of 100%, 80%, 50% and 30%, densities of 230 points/m2, 184 points/m2, 115 points/m2 and 69 points/m2 are obtained. These are used to analyze the effect of intensity frequency on tree species classification accuracy under four different point cloud densities. The results are shown as follows. (1) Intensity frequencies of trees are not significantly different for intraspecies (p &gt; 0.05) values and are significantly different for interspecies (p &lt; 0.01) values. (2) The intensity frequency features of LiDAR can be used to classify different tree species with an overall accuracy (OA) of 86.7%. Acer Buergerianum achieves a user accuracy (UA) of over 95% and a producer accuracy (PA) of over 90% for four density conditions. (3) The OA varies slightly under different point cloud densities, but the sum of correct classification trees (SCI) and PA decreases rapidly as the point cloud density decreases, while UA is less affected by density with some stability. (4) The priori feature selected by mean rank (MR) covers the top 10 posterior features selected by RF. These results show that the new intensity frequency feature proposed in this study can be used as a comprehensive and effective intensity feature for the fine classification of tree species.

Vertical Variation in Leaf Traits and Crown Structure Promote the Coexistence of Forest Tree Species

Vertical stratification in trees may respond to selective pressures to enhance light interception and utilization; therefore, the vertical functional variation in leaf traits may indicate niche partitioning within forests. In this study, vertical variations in leaf and crown structure traits of seven common tree species were analysed with respect to differences between species in different height groups, within the same height range, in the same species across tree height, and different parts of the individual tree crown to reveal coexistence mechanisms in subtropical forest tree species. There were multiple levels of trait variation in the vertical dimension, validating the existence of vertical niche differentiation in subtropical forest species. The functional trait differences arose among different height groups, among species co-occurring within the same height range, in the same species across tree height, and among different parts of the individual tree crown. Variation in comparative advantages, which was characterised by those traits between species across different height ranges, was also one of the manifestations of niche differentiation in the vertical dimension. Moreover, contrasting results between lower height ranges and higher ranges in the relationship between species’ differences in functional traits and species’ difference of abundance were found, further confirming that there was obvious vertical niche separation in the community. This study emphasised the importance of vertical variation in species’ performances in elucidating the mechanisms of tree species coexistence in subtropical forests.

三个亚热带森林优势种凋落物非结构性碳水化合物含量的季节动态

PDF HTML阅读 XML下载 导出引用 引用提醒 三个亚热带森林优势种凋落物非结构性碳水化合物含量的季节动态 DOI: 10.5846/stxb202103050606 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32022056，31800521，31922052） Seasonal variations of non-structural carbohydrates in fresh litters of three dominant tree species in subtropical forests Author: Affiliation: Fund Project: National Natural Science Foundation of China (32022056, 31800521, 31922052). 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:非结构性碳水化合物（NSC）是凋落物中的易分解组分，在凋落物分解早期快速释放进入土壤并被微生物利用，参与森林土壤生物地球化学循环，因此新鲜凋落物中NSC变化规律是认识森林土壤碳和养分循环的关键之一。选取亚热带常绿阔叶林优势树种米槠（Castanopsis carlesii）和主要造林树种杉木（Cunninghamia lanceolata）、马尾松（Pinus massoniana）为研究对象，分析其新鲜凋落叶和凋落枝中NSC （可溶性糖和淀粉）含量的动态变化规律。结果表明：凋落物中NSC含量在不同月份表现出明显的时间动态，米槠、杉木和马尾松凋落叶和凋落枝中NSC含量总体上在11-12月呈上升趋势，而在2-6月呈缓慢下降趋势。不同类型的凋落物NSC含量存在显著差异，米槠、杉木和马尾松凋落叶中NSC含量分别为3.03%-3.56%、2.18%-4.37%、3.38%-4.89%，凋落枝中NSC含量分别为1.87%-4.22%、2.88%-4.28%、2.75%-5.27%，米槠和马尾松凋落叶中NSC含量高于凋落枝，而杉木凋落枝中NSC含量高于凋落叶。不同树种凋落物NSC含量差异显著，米槠和马尾松凋落叶中NSC含量显著高于杉木，而马尾松凋落枝中NSC含量显著高于米槠。这些结果表明，凋落物中NSC含量受凋落物类型、树种和凋落物生产节律的影响，且亚热带常绿阔叶林转换为杉木和马尾松人工林将改变凋落物中NSC等易分解组分归还，进而影响森林地表生物地球化学过程。 Abstract:Forests retain large amounts of organic carbon mainly through the accumulation of photosynthetic products and the sequestration of soil organic carbon. Plant litter transfers carbon from plants to soils as a more stable pool with high resistance time. Non-structural carbohydrates (NSC), such as soluble sugars and starch, are labile components in plant litter and could be released quickly from decomposing litter and utilized by soil microorganisms. Therefore, the NSC in plant litter could involve in soil biogeochemical cycles and is a key driver for carbon and nutrient cycling in forest soils. In this study, we collected monthly fresh leaf and twig litters of Castanopsis carlesii (a dominant tree species in subtropical evergreen broad-leaved forest), Cunninghamia lanceolata and Pinus massoniana (two main planted trees in subtropical China) in a natural Castanopsis carlesii forest and the Cunninghamia lanceolata and Pinus massoniana plantations over one year to assess the seasonal dynamics of the NSC (including soluble sugars and starch) in fresh litters. The results showed that the NSC content in fresh litter varied significantly among seasons for all studied litter species and between litter types (leaf versus twig). In general, the NSC content in the leaf and twig litters of Castanopsis carlesii, Cunninghamia lanceolate, and Pinus massoniana greatly increased in November and December but decreased dramatically from February to June of the following year. The NSC content differed significantly between litter types:the NSC content in leaf litters of Castanopsis carlesii, Cunninghamia lanceolata and Pinus massoniana showed average values of 3.03%-3.56%, 2.18%-4.37%, 3.38%-4.89%, respectively, while those in the twig litters were 1.87%-4.22%, 2.88%-4.28%, 2.75%-5.27%, for the three litter species, respectively. The NSC contents in leaf litters of Castanopsis carlesii and Pinus massoniana were generally higher than those in the twig litters, and the NSC content in twig litter of Cunninghamia lanceolata was higher than that in the leaf litter. The NSC content in fresh litter also varied significantly among tree species:the NSC contents in leaf litters of Castanopsis carlesii and Pinus massoniana were significantly higher than that of Cunninghamia lanceolata, and the NSC content in twig litter of Pinus massoniana was significantly higher than that of Castanopsis carlesii. The results suggest that the NSC content in fresh litter varied significantly between litter types, tree species and litterfall rhythms. The conversion of subtropical evergreen broad-leaved forests to Cunninghamia lanceolata and Pinus massoniana plantations may change the input of easily decomposable components from seasonal litterfall, and this change in labile carbon input from fresh litterfall may affect soil microbial turnover and microbially mediated biogeochemical cycles in forest soils of subtropical China. 参考文献 相似文献 引证文献

Interpretation of the difference in shade tolerance of two subtropical forest tree species of different successional stages at the transcriptome and physiological levels.

Differences in plant shade tolerance constitute a major mechanism driving the succession of forest communities in subtropical forests. However, the indirect effects of differences in light requirements on the growth of mid- and late-successional tree species are unclear, and this potential growth effect has not been explained at the transcriptome level. Here, a typical mid-successional dominant tree species, Schima superba Gardn. et Champ, and a typical late-successional dominant tree species, Cryptocarya concinna Hance were used as materials and planted under 100% full light (FL) and 30% FL (low light, LL) to explore the responses of tree species in different successional stages of subtropical forests to different light environments. Transcriptome sequencing was used to analyze the expression changes in genes related to growth and photoprotection under different light environments. The young leaves of S. superba accumulated more malondialdehyde (MDA) and superoxide radicals (${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$) under LL. A lower hormone content (auxin, cytokinin, gibberellin) in the young leaves, a weaker photosynthetic capacity in the mature leaves and significant downregulation of related gene expression were also found under LL, which resulted in the total biomass of S. superba under LL being lower than that under FL. The young leaves of C. concinna had less MDA and ${\mathrm{O}}_2^{{{}^{\bullet}}^{-}}$, and a higher hormone contents under LL than those under FL. There was no significant difference in photosynthetic capacity between mature leaves in contrasting light environments. Although the biomass of C. concinna under LL was less than that under FL, the height of C. concinna under LL was higher than that under FL, indicating that C. concinna could grow well under the two light environments. Our results describing the acclimatization of light at the physiological, molecular and transcriptome levels are important for a complete understanding of successional mechanisms.

Neighborhood effects and environmental variables drive sapling growth in a young subtropical tree plantation

We established a forest biodiversity and ecosystem functioning experiment in southern China by planting 20,480 saplings of eight subtropical tree species in 320 plots in monocultures and mixtures of two, four and eight species to explore the biodiversity-ecosystem functioning (BEF) relationships and the underlying coexistence determinants. In this study, we aimed to report the growth of these planted saplings and explore its abiotic and biotic driving factors. Specifically, we analyzed the relative importance of sapling species identity, initial size, neighborhood interactions, neighborhood diversity, and environmental factors to sapling growth in the early stage of our BEF experiment. We found that the species of Ilex rotunda, Pinus massoniana and Elaeocarpus sylvestris grew much faster than other five species, followed by Castanopsis carlesii, Cinnamomum camphora and Schima superba. Erythrophleum fordii and Castanopsis fissa had the lowest growth rates in ground diameter and height. In addition, the relative growth rates of saplings were positively related to the neighborhood interactions, neighborhood diversity and soil nutrients, but were negatively related to initial size. Our study stresses the importance of better understanding the effects of environmental and local neighborhood conditions on initial growth of subtropical forest tree species in a mixed plantation, and provides reference for other BEF experiments in China and elsewhere.

Differential determinants of growth rates in subtropical evergreen and deciduous juvenile trees: carbon gain, hydraulics and nutrient-use efficiencies.

Growth rate varies across plant species and represents an important ecological strategy for competition, resource-use and fitness. However, empirical studies often show a low predictability of functional traits to tree growth. We measured stem diameter and height growth rates (DGRs and HGRs) of 96 juvenile trees (2-5m tall) of eight evergreen and eight deciduous broadleaf tree species over three consecutive years in a subtropical forest in south-western China. We examined the relationships between tree growth rates and 20 leaf/stem traits that are associated with carbon gain, stem hydraulics and nutrient-use efficiency, as well as the difference between evergreen and deciduous trees. We found that cross-species variations of stem DGR/HGR can be predicted by leaf photosynthetic capacity, leaf mass per area, xylem-theoretical-specific hydraulic conductivity, wood density (WD) and photosynthetic-nutrient-use efficiencies. Higher leaf carbon assimilation and lower leaf/stem constructing costs facilitate deciduous species to be more resource acquisitive and consequently faster growth within a relatively shorter growing season, whereas evergreen species exhibit more conservative strategies and thus slower growth. Furthermore, stem growth rates of evergreen species showed were more dependence on leaf carbon gains, whereas stem hydraulic efficiency was more important for deciduous tree growth. Our results suggest that physiological traits (photosynthesis, hydraulics and nutrient-use efficiency) can predict tree diameter and height growth of subtropical tree species. The differential resource acquisition and use strategies and their associations with tree growth between evergreen and deciduous trees provide insights into explaining the coexistence of evergreen and deciduous tree species in subtropical forests.

Mixing with broad-leaved trees shapes the rhizosphere soil fungal communities of coniferous tree species in subtropical forests

Although replanting broad-leaved trees in coniferous forest has been proven to increase stand soil quality, it is unclear how this prevalent forest management regime affects the soil fungal communities of individual conifers in mixed forest. Herein, we chose two representative coniferous tree species (Pinus massoniana and Pinus elliottii) and employed high-throughput sequencing and quantitative PCR to investigate fungal community composition and function in rhizosphere soils under monoculture and in mixed forests (replanted with Schima superba for 13 years) in subtropical China. Mixing with broad-leaved trees resulted in increased rhizosphere soil organic carbon (SOC) and nutrient (total nitrogen, NH4+ and available phosphorus). Rhizosphere soil fungal abundance (ITS gene copy numbers) and community diversity of conifers were increased after mixing. Meanwhile, the soil fungal abundance and ACE richness index in Masson pine were higher compared with slash pine whether in monoculture or mixed forests. Ascomycota, Basidiomycota, Mortierellomycota and Glomeromycota were the dominant phyla in soils. Mixing with broad-leaved trees decreased the relative abundance of Ascomycota, while it increased Basidiomycota and Glomeromycota in the rhizosphere soil of conifers. Moreover, there was a decrease in the relative abundance of animal pathogens and wood saprotrophic fungi, while soil saprotrophic fungi, ectomycorrhizal and arbuscular mycorrhizal fungi were increased in rhizosphere soil of conifers after mixing, suggesting changes from saprotrophic fungi to symbiotrophic fungi to increase soil nutrient supply and enhance tree nutrient uptake. Principal coordinates analysis showed that the fungal communities in mixed forests clustered closely and were separated from monoculture forests. Fungal community composition and function were mainly dependent on SOC. Our results indicate that mixing with broad-leaved trees increases fungal abundance, alters fungal community composition and function and thus potentially contributes to soil quality improvement and tree nutrient acquisition of conifers. Masson pine is more adaptable than slash pine to establish mixed forest in subtropical China.

The relationship between anthocyanin accumulation and photoprotection in young leaves of two dominant tree species in subtropical forests in different seasons.

Increasing amounts of experimental evidence show that anthocyanins provide physiological protection to plants under stress. However, the difference in photoprotection mediated by anthocyanins and other photoprotective substances in different seasons is still uncertain. To determine the relationship between anthocyanin accumulation and the photoprotective effects in different seasons, Castanopsis chinensis and Acmena acuminatissima, whose anthocyanin accumulation patterns differ in different seasons, were used as materials to explain how plants adapt to different seasons; as such, their physiological and biochemical responses were analyzed. Young leaves of C. chinensis and A. acuminatissima presented different colors in the different seasons. In summer, the young leaves of C. chinensis were purplish red, while those of A. acuminatissima were light green. In winter, the young leaves of C. chinensis were light green, while those of A. acuminatissima were red. Compared with the young red leaves, the young light green leaves that did not accumulate anthocyanins had higher flavonoid and phenolics contents, total antioxidant capacity, non-photochemical quenching (NPQ), and relative membrane leakage, and a slower recovery rate in the maximum photochemical efficiency (Fv/Fm) after high-light treatment. In addition, the net photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (gs), and the effective quantum yield of PSII (ΦPSII) of the young leaves in winter were significantly lower than those in summer, while the activities of catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), and superoxide dismutase (SOD, EC 1.15.1.1) were significantly higher than those in summer. These data indicate that to adapt to seasonal changes anthocyanins, other antioxidative substances and antioxidative enzymes, as well as components involved in the safe dissipation of excitation energy as heat need to cooperate with one another.

Application of Terrestrial Close-Range Photogrammetry for Estimating Stem Volume of Tree Species in Subtropical Forest in Okinawa, Japan

Application of Terrestrial Close-Range Photogrammetry for Estimating Stem Volume of Tree Species in Subtropical Forest in Okinawa, Japan

Variation in the functional traits of fine roots is linked to phylogenetics in the common tree species of Chinese subtropical forests

The phylogenetic variations of fine root traits, which are related to plant growth and development as well as to physiological and ecological processes, are not fully understood. This study aimed to: (1) examine how tree species and sampling methodology affect the anatomical, morphological and nutrient traits of fine roots; and (2) determine whether phylogenetic signals affect fine root trait relationships and influence comparison of root traits between the branch order-based and diameter-based cut-off sampling categories. Fine root samples of 16 subtropical forest tree species were obtained and their anatomical, morphological and nutrient traits were studied. The phylogenetic signals of trait variations were calculated to determine trait relationships. Tree species and sampling methodology significantly affected fine root traits (p < 0.05). Mean root diameters, root tissue density (RTD) and carbon-to-nitrogen ratio were the lowest in the first-order category and highest in the ≤2 mm category. The reverse pattern was found for specific root length, specific root area and nitrogen concentration. Morphological traits showed significant phylogenetic signals; however, nutrient traits did not reflect phylogenetic conservatism. Phylogenetic factors influenced correlations between traits for the first-order root economics spectrum. Root traits were multidimensional and RTD was loaded on a novel phylogenetic principal component analysis. Functional traits of fine roots are multidimensional for subtropical tree species and closely linked to phylogeny. Morphological traits of first order roots showed a much stronger phylogenetic signal than those of roots ≤2 mm (traditionally defined fine roots). The findings improve understanding of root trait strategies in response to environmental changes.

Differential Responses of Stomata and Photosynthesis to Elevated Temperature in Two Co-occurring Subtropical Forest Tree Species.

Global warming could increase leaf transpiration and soil evaporation, which can potentially cause water deficit to plants. As valves, leaf stomata can control plant water loss and carbon gain, particularly under water stress conditions. To investigate the responses of stomata to elevated temperature in Schima superba and Syzygium rehderianum, two co-occurring subtropical forest dominant tree species, functional traits related to gas exchange, stomatal anatomy, and drought resistance were measured under control and warming environment (ca. 2°C higher). We found that leaf water potential at both predawn and midday significantly decreased for the two species grown under warming conditions compared with those grown in the control environment. Warming resulted in significant decrease of stomatal size in S. rehderianum, but had no obvious effect on that of S. superba. By contrast, stomatal density of S. superba significantly decreased under warming conditions, while non-significant change was observed for S. rehderianum. In addition, warming significantly reduced photosynthetic rate, stomatal conductance, and stomatal sensitivity to leaf water potential of S. superba, but had non-significant effects on those of S. rehderianum. Overall, our results demonstrated that, confronting water deficit caused by elevated temperature, the two co-occurring subtropical tree species responded differently through the adjustment of stomatal morphology and photosynthetic function. Consequently, S. rehderianum was able to maintain similar carbon assimilation as under control environment, while S. superba showed a decrease in carbon gain that might bring adverse effect on its dominancy in subtropical forest community under future climate change.

Functional characteristics of phenolic compounds accumulated in young leaves of two subtropical forest tree species of different successional stages.

The abundance of phenolic compounds (including anthocyanins) in leaves is associated with photosynthetic performance, but the regulatory mechanism is unclear. Schima superba Gardn. et Champ. and Cryptocarya concinna Hance., which exhibit distinct anthocyanin accumulation patterns, are dominant tree species in the early- and late-successional stages, respectively, of subtropical forests in China. RNA-seq and analyses of phenolic concentrations, antioxidant capacity and photosynthetic characteristics were performed on young and mature leaves of these two species under contrasting light conditions. The high-light-acclimated young leaves of S. superba and C. concinna and low-light-acclimated young leaves of C. concinna were red. These red leaves had higher ratios of electron transport rate to gross photosynthesis (ETR:Pgross) and total antioxidant capacity to chlorophyll (TAC:Chl) than did the green leaves, regardless of light conditions. In addition, the red leaves had a higher expression level of the UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene than did the green leaves, irrespective of light conditions. Total antioxidant capacity was positively correlated with flavonoid content in C. concinna leaves and with total phenolic content in leaves of both species under both high and low light. Consistent with the measurements of photosynthetic performance and flavonoids:Chl ratio, photosynthesis-related genes were extensively downregulated and flavonoid-pathway-related genes were extensively upregulated in young leaves relative to mature leaves. Under high and low light, both non-photochemical quenching and TAC:Chl, which serve as different types of photoprotective tools, were enhanced in young leaves of S. superba, whereas only TAC:Chl was enhanced in young leaves of C. concinna. Our results indicate that the biosynthesis of phenolic compounds in young leaves is likely enhanced by an imbalance between photosynthetic electron supply and demand and that flavonoids play a larger role in meditating photoprotection in late-successional species than in early-successional ones.

Regeneration responses to climate and land-use change of four subtropical tree species of the southern Central Andes

Abstract Land-use and climate change are impacting species and ecosystems around the world. The reproductive phase of plants is especially vulnerable to environmental change. Global environmental changes normally act collectively with nonlinearities and synergistic interactions being reported. Here we combined two techniques (i.e. a space-for-time substitution approach and a full factorial experiment) to assess the combined effects of climate and land-use change on the regeneration (seed production, seed germination and seedling survival and growth) of four subtropical forest tree species of the southern Central Andes (Yungas forest) in Argentina. We focus on temperature and precipitation changes and on decreased shading at the forest floor, a likely impact of changing land-use and management. We detected species-specific and phase-specific responses. Seed mass and quality was influenced by elevation (here used as a proxy for temperature change) while germination, seedling survival and growth were mainly affected by changes in the seedbed conditions (i.e. changes in shading and in moisture related to precipitation change). Despite the influence of environmental conditions on all the phases of plant regeneration studied here, we show that the major bottleneck of the regeneration phase of these species is germination. Interactive effects between the elevation of the seeds’ provenance, precipitation and shading underpin the importance of studying the effects of different environmental changes collectively on plant regeneration to better forecast the effects of climate and land-use change on the Yungas forest.

Tree-Species Classification in Subtropical Forests Using Airborne Hyperspectral and LiDAR Data

Accurate classification of tree-species is essential for sustainably managing forest resources and effectively monitoring species diversity. In this study, we used simultaneously acquired hyperspectral and LiDAR data from LiCHy (Hyperspectral, LiDAR and CCD) airborne system to classify tree-species in subtropical forests of southeast China. First, each individual tree crown was extracted using the LiDAR data by a point cloud segmentation algorithm (PCS) and the sunlit portion of each crown was selected using the hyperspectral data. Second, different suites of hyperspectral and LiDAR metrics were extracted and selected by the indices of Principal Component Analysis (PCA) and the mean decrease in Gini index (MDG) from Random Forest (RF). Finally, both hyperspectral metrics (based on whole crown and sunlit crown) and LiDAR metrics were assessed and used as inputs to Random Forest classifier to discriminate five tree-species at two levels of classification. The results showed that the tree delineation approach (point cloud segmentation algorithm) was suitable for detecting individual tree in this study (overall accuracy = 82.9%). The classification approach provided a relatively high accuracy (overall accuracy &gt; 85.4%) for classifying five tree-species in the study site. The classification using both hyperspectral and LiDAR metrics resulted in higher accuracies than only hyperspectral metrics (the improvement of overall accuracies = 0.4–5.6%). In addition, compared with the classification using whole crown metrics (overall accuracies = 85.4–89.3%), using sunlit crown metrics (overall accuracies = 87.1–91.5%) improved the overall accuracies of 2.3%. The results also suggested that fewer of the most important metrics can be used to classify tree-species effectively (overall accuracies = 85.8–91.0%).