Trees最新文献

Key message

N addition positively affected the growth of C. pachystachya (shade-intolerant) in the sun but not in the shade, while the growth of C. estrellensis (shade-tolerant) wasn’t affected.

Abstract

The Brazilian Atlantic Forest is a highly biodiverse and threatened ecosystem, subjected to intense deforestation and N deposition levels that may exceed the critical N load supported by this ecosystem. The objective of this study was to evaluate in green house conditions how 10 weekly applications of N (28 kg N ha⁻) affects the gas exchange, the amino acid and protein concentrations in the tissues, and the growth of seedlings two tree species: Cecropia pachystachya (Urticaceae; shade-intolerant) and Cariniana estrellensis (Lecythidaceae; shade-tolerant). Plant responses to N addition were compared on sun and on shade. While Cecropia pachystachya improved the total plant dry mass and the relative growth rate with N addition in the sun, but not in the shade, C. estrellensis increased the stomatal conductance, net photosynthesis, and instantaneous carboxylation efficiency in the shade, although without any change on the plant total biomass. The results of the study indicate that the deposition of n can have differential effects on different species.

Key message

Experimentally elevated CO₂ does not significantly alter the overall leaf reflectance of mature Quercus robur L., but increases Plant Senescence Reflectance Index (PSRI) suggesting a change in the ratio of chlorophyll to carotene content.

Rising atmospheric CO₂ concentrations, driven by anthropogenic emissions, are projected to reach 550 ppm by 2050. Elevated CO₂ (eCO₂) is expected to have a fertilisation effect on forests, influencing productivity, water relations, and phenology. However, the impact of eCO₂ on leaf reflectance in mature forests remains poorly understood, despite its critical role in radiative transfer processes and remote sensing of forest health. Utilising the Birmingham Institute of Forest Research (BIFoR) Free-Air CO₂ Enrichment (FACE) experiment, we investigated the hyperspectral leaf reflectance of 180-year-old Quercus robur L. trees exposed to eCO₂ for 7 years. Our results demonstrate that overall leaf reflectance under eCO₂ is similar to that of leaves exposed to ambient CO₂, but the Plant Senescence Reflectance Index (PSRI) is significantly higher under eCO₂. This index relates to the ratio of foliar chlorophyll and carotene pigments. These findings suggest that Q. robur reflectance will not significantly shift under future CO₂ conditions, but the relative content of pigments will change, altering the reflectance of specific wavelengths and providing insights into the leaf level physiological and phenological responses of mature trees to eCO₂.

Stem CO₂ efflux is an important component of forest carbon emission. The response of stem CO₂ efflux rate (Es) in Betula platyphylla secondary forests at different phenological stages and environmental factors, however, has been inadequately explored. We used an LI-6800 gas analyzer to measure Es from Betula platyphylla secondary forests in northern China in four diameter classes (D₁:6–10, D₂:10–14, D₃:14–18, and D₄:18–22 cm) throughout the year and during different phenological periods. The study reveals that daily Es across all diameter classes exhibited single-peak trends per phenological stage, peaking at 13:00–19:00 (1.95–0.08 μmolm⁻² s⁻¹) and bottoming at 23:00–07:00 (0.81–0.01 μmolm⁻² s⁻¹). The Es values of D₃ and D₄ showed a unimodal trend throughout the year, with peaks at the full leaf period (1.34 and 1.48 μmolm⁻² s⁻¹), while D₁ and D₂ showed a fluctuating downward trend, peaking at the leaf spreading stage (0.87 and 0.93 μmolm⁻² s⁻¹), and then reaching a minimum at the leafless period. Air temperature (Ta) and photosynthetically active radiation (PAR) were the dominant drivers of Es across diameter classes, while soil volumetric water content (VWC) exhibited weaker effects. The responses of Es to Ta and PAR differed phenologically: in leaf spreading and leaf fall periods, Es increased with Ta and decreased with PAR; during full leaf period, Es was strongly temperature-dependent but PAR-insensitive; in leafless period, Es showed a quadratic response to PAR but minimal temperature sensitivity. These findings suggest that stem CO₂ efflux in boreal Betula platyphylla forests will increase under warming climates and extended leafy periods, with secondary modulation by soil moisture dynamics.

Key message

Continuing drought from winter to spring delayed the spring bud phenology of seedlings, and seedlings experiencing colder winter previously were less influenced by the severe drought.

Abstract

Water availability at the beginning of the growth phase, and even before it, is decisive in the phenology and annual cycle of forest trees, consequently affecting carbon sequestration and forest ecosystem balance. This is a novel experimental study on the effects of continuous drought throughout winter and early spring on tree performance. Two groups of Pinus sylvestris var. mongolica seedlings were overwintered in a Chinese solar greenhouse (BIG seedlings) and a plastic tunnel (SMALL seedlings). The seedlings were subjected to continuing droughts from winter to an extra 0 (control), 15 (D15), 30 (D30) and 45 days without irrigation (D45) after soil thawing next spring. Bud phenology, tree growth and physiology were examined. Bud phenological development, tree aboveground growth and root biomass growth were delayed in treatments D30 and D45 in both seedling types. SMALL seedlings had earlier bud phenology and were less influenced by drought than BIG seedlings. The drought-induced changes in spring phenology were associated with higher ABA and lower GA3 concentrations of needles. The phenology and growth differences between the seedling types might relate to soluble sugar concentrations of roots, needle chlorophyll content, needle chlorophyll fluorescence and acclimated morphological changes, such as root-shoot ratio. We suggest that in forest management, a big seedling size does not guarantee growth success, but attention should be paid to the proper conditions in overwintering and storing of the seedlings prior planting. Prolonged drought throughout winter and early spring should be avoided especially before planting the seedlings in an area prone to drought.

Wood-decay fungi (WDF) are vital for forest ecosystem functioning but can also cause tree diseases, leading to significant economic impacts on forest management. Here, we characterize WDF and investigate damage severity of infected trees in anthropogenically disturbed sites in Mount Makiling Forest Reserve (MMFR), Philippines. Forty fruiting bodies from 10 fungal species were collected in two anthropogenically influenced sites (PFLA1 and CAMP) in MMFR, with all 10 species recorded in PFLA1 and only 2 in CAMP. Genera of WDF recorded in both sites include Ganoderma, Phellinus, Earliella, Microporus, Fomitopsis, Funalia, Inonotus, Skeletocutis, and Abundisporus. Wallaceodendron celebicum and Swietenia macrophylla trees with and without wood-decay fungi in CAMP were further assessed using Arbotom 2D Sonic Tree Tomography to reveal the damage severity in the presence of WDF. Mean stress wave velocities in the infected W. celebicum (1212.32 m/s) and S. macrophylla (1533.99 m/s) trees were lower, though not significantly, than those with no signs of decay (W. celebicum: 1397.80 m/s; S. macrophylla: 1732.68 m/s), suggesting reduced wood density in trees affected by wood-decay fungi. Acoustic tomography also revealed indications of internal decay among trees without fruiting bodies. Findings from this study can help improve understanding of WDF composition and their impact on trees across different land use types. Further research is needed to examine their interactions with trees under varying environmental and host conditions.

Key message

This study highlights significant drought tolerance variations among seedlings from different provenances of beneh in the Zagros forests, with dry–warm southern genotypes showing superior morphophysiological and molecular responses.

Abstract

Drought poses a significant threat to the growth and stability of forest ecosystems globally. Beneh (Pistacia atlantica subsp. kurdica), an important tree species in the Zagros forests of western and southern Iran, has been increasingly affected by drought in recent years. In this study, we assessed the morpho-physiological and gene expression responses of 14-month-old seedlings sourced from the climatic edges of the species' distribution in Zagros forests with the aim of provenance-specific recommendations to enhance afforestation success and promote adaptation to future challenges. Significant variation in drought tolerance was revealed among provenances. Temperate northern provenances exhibited a more pronounced decline in shoot and root growth (45–62%), accompanied by significant variations in carbon (C) and nitrogen (N) levels. The dry–warm southern provenances showed more growth suppression in shoots compared to roots. In addition, they exhibited significantly higher rates of photosynthesis (An), chlorophyll fluorescence (Fv/Fm), and intrinsic water use efficiency (iWUE). In drought, levels of malondialdehyde (MDA) and protective osmolytes, as well as the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) enzymes, increased in seedlings, with a more pronounced effect observed in drier provenances. The expression patterns of CTD, GST, MKK5, WRKY, CYP90, SDH, P5CS genes differed between temperate northern and dry–warm southern provenances, suggesting key roles in stress response pathways. In conclusion, the drier provenances exhibited enhanced drought tolerance, improved morphology and physiology, and distinct root gene expression patterns. This study enhances understanding of local adaptation of beneh trees to drought, crucial for climate change strategies and predicting drought impacts on beneh forests.

Gibberellins (GAs) are key plant growth regulators, but their regulatory mechanisms in woody plants remain to be explored. In this study, Populus davidiana × P. bolleana (Shanxin poplar) plants were treated with GA₃ for different times. The results revealed that exogenous GA₃ increased the fresh weight, stem internode length, plant height, stem diameter, chlorophyll content, and the width and length of leaves. Xylogenesis was enhanced under GA₃ treatment, as evidenced by the staining of transverse stem sections with toluidine blue, phloroglucinol-HCl, and calcofluor white. In addition, the total contents of endogenous GA, auxin, and cytokinin were increased. Furthermore, RNA-seq analysis indicated that 112, 2473, and 3773 genes were differentially expressed under GA₃ treatment for 0.5 h, 48 h, and 7 d. The differentially expressed genes (DEGs) were mainly related to plant hormone signal transduction, phenylpropanoid biosynthesis, diterpenoid biosynthesis, and photosynthesis processes. Further analysis suggested that GA₃ treatment enhanced plant biomass by regulating the expression of DEGs involved in cell elongation, xylem formation, and stress tolerance. Furthermore, our research has demonstrated that the overexpression of the DEGs MYB52 and bHLH71 can significantly enhance the salt tolerance of poplar plants by improving their capacity to scavenge reactive oxygen species (ROS). These findings provide insight into the regulatory mechanisms of GA₃ and identify the key genes associated with high salt tolerance in Shanxin poplar.

Key message

Local hydroclimatic conditions influenced black spruce xylem anatomy in boreal treed fens. Earlywood cells were sensitive to early summer temperature, indicating that future warmer climates could negatively impact the xylem structure.

Abstract

Black spruce (Picea mariana) growing in treed boreal fens in North America face significant challenges due to anticipated warming and moisture deficits. To assess site and climate influence on black spruce xylem anatomy, we investigated two treed fens at different elevations (740 m and 320 m a.s.l.) in Alberta, Canada. We examined key xylem traits – cell number, cell lumen area, and cell wall thickness – comparing the two sites to assess the effects of local conditions. Additionally, we correlated these anatomical features with long-term temperature, precipitation, and vapor pressure deficit (VPD) data to evaluate the impact of inter-annual climate variability. We observed larger cell lumens and thinner cell walls in trees at the lower-elevation fen. Xylem climate responses were clearer at the higher-elevation fen, characterized by a more stable water table. Here, previous year summer temperatures were negatively associated with cell number. High temperatures and VPD during the current year late spring and early summer reduced earlywood lumen size. Precipitation showed marginal associations at both sites. This study demonstrates the utility of quantitative wood anatomy in understanding environmental influences on tree xylem anatomy in treed fens. Differences in climatic responses between nearby sites highlight the importance of local hydroclimatic conditions in shaping xylem structure. Notably, observed sensitivity of cell lumen area to spring and early summer temperature and VPD suggests that climate warming could significantly impact the xylem structure and water transport efficiency of black spruce in treed boreal fens.