Broad-leaved Research Articles

Enhanced Foliar Litter Decomposition Rate of Pinus massoniana When Admixed with Broadleaf Species

In the global ecosystem, the slow decomposition of coniferous forest litter has caused a number of ecological problems, among which is the decay of China’s Pinus massoniana litter. It has been pointed out that converting pure P. massoniana plantations into mixed forests with broadleaf species can improve ecosystem services. Therefore, the selection of mixed species is key for the success or failure of the conversion of near-natural forests. In this study, from the perspective of apoplastic decomposition, the leaf litter of P. massoniana was mixed with three common native broadleaf species, namely Choerospondias axillaries, Cinnamomum camphora, and Cyclobalanopsis glauca, using an indoor incubation method to systematically analyse the differences in the decomposition rates of apoplastic material in each mixture, and to provide a theoretical basis for the selection and mixing of tree species for the management of near-natural forests in P. massoniana forests. After 175 days of indoor incubation of the foliar litter under dark conditions at 25 °C, the residual dry matter of the mixed apoplastic litter of P. massoniana and the three broadleaf trees was lower than that of P. massoniana. It indicated that the incorporation of broadleaf apoplastic foliage promoted litter decomposition, with the most pronounced effect in the case of admixture with C. Camphora. Compared with the group of pure P. massoniana alone, the remaining mass and residual rate decreased by 0.56 g and 9.45%, respectively. The regression equation of Olson’s negative exponential decay model showed that the P. massoniana + C. Camphora mixture had the fastest decomposition rate (k) of 1.305, an increase of 0.237, a decrease in half-life of 0.11 years, and a decrease in turnover period of 0.49 year, compared to the P. massoniana alone group. Most of the measured values throughout the incubation period were significantly lower than the predicted values, suggesting that there was a non-additive and synergistic effect of litter mixing.

Sodium alumino silicate (SAS) neem nanocomposite – A novel seed storage tool against toxigenic Aspergillus flavus causing deterimental effects on seeds health and quality of rice

Infection of rice grains in the field during harvest and storage by Aspergillus flavus, a toxigenic mold causes significant losses to market acceptability of seeds due to its detrimental effects on seed health and quality parameters. Production of aflatoxin by A. flavus interferes with physiological factors affecting the quality of seeds during storage in addition to nutritional losses to the grains. Chemical seed treatments are generally not recommended during storage due to their adverse effects on seed germination and vigor. Leaves of the neem tree (Azadirachta indica) are well known for antifungal properties against phytopathogenic fungi such as A. flavus. The paper presents the effect of neem leaf extract adsorbed onto sodium alumino-silicate (SAS) nanoparticles against A. flavus in rice seeds during storage. SAS-Neem nanocomposite, a novel unexplored seed storage material against toxigenic A. flavus, was synthesized for augmented antitoxin and seed invigorating potential. The nanocomposite was characterized using an array of microscopic and spectroscopic methods to evaluate the adsorption of neem leaf extract components on SAS nanoparticles. The antifungal mechanism of the nanocomposite was evaluated via scanning electron microscope, phase contrast, and fluorescence microscopy. The toxin analysis of pathogen-inoculated seeds was carried out at monthly intervals for 6 months during storage of two rice varieties, i.e. PR114 and Pusa-Basmati 1121. The results indicated that the nSAS-Neem composite used as seed coating material maintained significantly higher seed germination (86.23 and 81.49%) and minimized seed rot (6.70 and 5.30%, respectively) in the two varieties under study than the control after 6 months of storage. There was a notable decrease in toxin concentration from 20.58 to 11.19 μg/kg and 19.16 to 12.58 μg/kg in seeds of the two varieties i.e. PR114 and Pusa Basmati 1121, respectively. The nano-composite proved effective against toxigenic A. flavus during seed storage of rice without compromising the seed quality parameters.

First report of Diaporthe tulliensis causing leaf spot on Millettia speciosa in China.

Millettia speciosa Champ, renowned for its diverse applications in traditional medicine, is extensively cultivated in the Guangxi region of China, spanning roughly 5,973 hectares. In July 2021, a plantation in Yulin, Guangxi, China (22°64'N; 110°29'E), exhibited severe leaf spot disease on M. speciosa. Notably, a 46,690 square meters area had over 40% leaf spot incidence. Initially, symptoms appeared as small, circular, pale-yellow lesions on the leaves, then turned into irregular, dark brown spots with yellow halos, leading to the wilt and defoliation of leaves. To identify the responsible pathogen, a total of five symptomatic leaves were collected and sterilized systematically. Small tissue segments (5×5 mm) from lesion peripheries were aseptically excised, then surface sterilized with 75% ethanol for 10 s, and 1% sodium hypochlorite (NaClO) for 3 min. Following this, the sterilized tissues were triple-rinsed with sterile water and cultured on potato dextrose agar (PDA) at 28 °C in the dark for 7 d. A total of seven isolates were obtained through single-spore isolation, and one representative isolate, N2-3, was selected for further analysis. After 7 d of incubation, colonies displayed flat, white, and extensively branched aerial hyphae. Over time, the reverse side of the colony changed from white to yellowish-white. The pycnidia were black with conidial droplets ranging from cream to pale yellow exuding from their ostioles. The α-conidia were one-celled, hyaline, ovoid to cylindrical, typically with one or two droplets, 2.6 to 5.9 ×1.4 to 3.9 μm (n=50). These morphological traits align with those of the genus Diaporthe, as reported by Li et al. (2022) and Crous et al. (2015). To identify the species, isolate N2-3 underwent sequencing of the internal transcribed spacer (ITS), β-tubulin (BT), and translation elongation factor 1 alpha (EF1-α) sections (Huang et al. 2021). Obtained sequences of ITS, BT and EF1-α (Genebank accessions nos. OR600532, OR662169 and OR662168) displayed a 99% similarity to Diaporthe tulliensis (Genebank accessions nos. OP219651, ON932382, OL412437, respectively). Based on the concatenated ITS, BT and EF1-α, a neighbor-joining phylogenetic analyses using MEGA7.0 clustered with D. tulliensis. Therefore, the fungus was identified as D. tulliensis (teleomorph name) based on morphological and molecular features. A pathogenicity test was conducted on 1-year-old M. speciosa seedlings by gently abrading healthy leaves with sterilized toothpicks to create superficial wounds. Wounded leaves were then inoculated with 5 mm diameter mycelial plugs, while control seedlings received PDA plugs. Three leaves per plant and five plants per treatment were selected for assessment. All seedlings were kept in a controlled greenhouse (12/12h light/dark, 25 ± 2 °C, 90% humidity). After 7 d, the inoculated leaves showed symptoms like those in the field, while control plants remained healthy. The fungus was consistently reisolated from the infected leaves, satisfying Koch's postulates. Notably, D. tulliensis has caused Boston ivy leaf spot, bodhi tree leaf spot, cacao pod rot, and jasmine stem canker (Huang et al. 2021; Li et al. 2022; Serrato-Diaz et al. 2022; Hsu et al. 2023). This discovery is significant as it marks the first report of Diaporthe tulliensis causing leaf spot on Millettia speciossa in China, which has direct implications for the development of diagnostic tools and research into potential disease management strategies.

Tracing 40,000 years of vegetation change in the Baetic-Rifan biodiversity hotspot

This study presents a 40,000-year-old pollen record from Los Tollos Lake in the Baetic-Rifan region of southernmost Spain. The data offer insights into the past ecosystems of a current biodiversity hotspot situated at the ecotone between the Atlantic and the Mediterranean. This new sequence encompasses Mediterranean and Ibero-North African sclerophylls, broad-leaf trees, conifers, and Tertiary relicts. The full-glacial abundance of mesothermophytes, particularly oaks, is among the highest recorded for the European Quaternary. Notably, the presence of ecologically significant pollen taxa, which are poorly dispersed and currently occur outside the study area, suggests that this biodiversity hotspot was more extensive in the Pleistocene. During the period of c. 40.8–36.5 ka, three Artemisia maxima at 40.6, 38.9, and 36.9 ka coincide with decreases in Quercus, indicating the spread of steppes in response to the abrupt coolings of the GS10, GS9 (HS4), and GS8 events. Similarly, increases in Quercus around 41, 40, and 37.2–38.3 ka parallel the GI10, GI9, and GI8 warm events. A forested period from 36.5–32 ka includes oak expansions during the GI7 and GI6 interstadials. From 32 to 19.2 ka, more xerophytic vegetation is observed, including the HS3, GS5-GS3, HS2, and GS2.1b-c cold spells, although the correlation with vegetation changes is not synchronous. As early as approximately 21 ka, Artemisia definitively declines, while the region was reforesting, likely due to the presence of stationary populations of broadleaf trees and conifers in the southern Baetic mountains. From approximately 12 ka onwards, the highest values of angiosperm trees are recorded, with oaks dominating throughout most of the Holocene. The pollen record and the correlation with marine records suggest a more intense hydrological regime during the first half of the Holocene, but there is also archaeobotanical evidence for human activity during the second half, resulting in a more open landscape, making it difficult to discriminate the impact of each factor. Some abrupt aridity events during the Holocene coincide with small variations in tree cover, particularly at 9.2, 8.2, 6.8, 5.5–4.8, 4.2, and 2.8 ka. Since the Neolithic and during the metallurgic stages, forest species, especially broad-leaf trees, experienced range retraction accompanied by population extinctions. The region's plant communities have been subject to fire regimes since the Pleistocene, seemingly dependent on the available tree biomass.

Modeling the Impacts of Climate Change on Potential Distribution of Betula luminifera H. Winkler in China Using MaxEnt

Betula luminifera H. Winkler, a fast-growing broad-leaved tree species native to China’s subtropical regions, possesses significant ecological and economic value. The species’ adaptability and ornamental characteristics make it a crucial component of forest ecosystems. However, the impacts of global climate change on its geographical distribution are not well understood, necessitating research to predict its potential distribution shifts under future climate scenarios. Our aims were to forecast the impact of climate change on the potential suitable distribution of B. luminifera across China using the MaxEnt model, which is recognized for its high predictive accuracy and low sample data requirement. Geographical coordinate data of B. luminifera distribution points were collected from various databases and verified for redundancy. Nineteen bioclimatic variables were selected and screened for correlation to avoid overfitting in the model. The MaxEnt model was optimized using the ENMeval package, and the model accuracy was evaluated using the Akaike Information Criterion Correction (delta.AICc), Training Omission Rate (OR10), and Area Under the Curve (AUC). The potential distribution of B. luminifera was predicted under current and future climate scenarios based on the Shared Socio-economic Pathways (SSPs). The optimized MaxEnt model demonstrated high predictive accuracy with an AUC value of 0.9. The dominant environmental variables influencing the distribution of B. luminifera were annual precipitation, minimum temperature of the coldest month, and standard deviation of temperature seasonality. The potential suitable habitat area and its geographical location were predicted to change significantly under different future climate scenarios, with complex dynamics of habitat expansion and contraction. The distribution centroid of B. luminifera was also predicted to migrate, indicating a response to changing climatic conditions. Our findings underscore the importance of model optimization in enhancing predictive accuracy and provide valuable insights for the development of conservation strategies and forest management plans to address the challenges posed by climate change.

Tree species-mediated soil properties shape soil fauna community structure more strongly in the soil layer: Evidence from a common garden experiment

Soil fauna plays a crucial role in the soil biogeochemical cycles of forest ecosystems, with tree species composition regulating their diversity and functionality through alterations in habitat conditions and nutrient availability. However, identifying the impacts of tree species on soil faunal communities remains challenging due to the difficulty in distinguishing the effects of tree species-induced habitat changes from those of historical environmental conditions. Here, we conducted a field study in a common garden established in 2015, with consistent climate, soil, and land-use conditions to clarify the response of the soil faunal community to changes in tree species. After 5 years of plantation growth, we evaluated the differences in tree species identities and soil faunal community structures between the litter and soil layers in four closed-canopy broadleaf forests (Cinnamomum septentrionale, Cinnamomum camphora, Cinnamomum longepaniculatum and Toona sinensis). We found that the soil faunal communities differed significantly among the four broad-leaved tree species, with 18.7 % being dominated by Collembola and 67.2 % by Acari, with a relatively high proportion of microbivores (65.5 %). Compared with that of the other stands, the C. longepaniculatum stand had the most notable differences in taxa composition, while the T. sinensis stand exhibited the greatest soil biological quality, with a QBS value 1.25 times greater than that of other stands. The greatest total soil faunal abundance was observed in C. camphora, and this high abundance was due to a greater proportion of microbivores (75.4 %), whereas the detritivores, herbivores, and predators exhibited greater abundance in T. sinensis than in the other stands due to the high-quality litter input (low C/P and C/N ratios) and low tree biomass. The distribution of soil fauna across the habitat layers was significantly influenced by tree species changes, with the most pronounced differences occurring in the soil layer rather than in the litter layer. Finally, soil properties, rather than litter and plant conditions, were the primary factors explaining interspecific variations in total abundance and total diversity of the soil fauna and the QBS index, accounting for 61.6 %, 71.7 %, and 34.4 % of the variation, respectively. The results from the common garden experiment suggest that the change in the soil faunal community due to tree species identity was greater in the soil layer than in the litter layer, with the crucial determinant being tree-species-mediated soil properties. These insights enhance our understanding of the effect of tree species on soil faunal communities, which is essential for biodiversity conservation in artificial forests and for guiding tree species selection.

Pollen evidence of enhanced Yellow River provenance into the South Yellow Sea after the Middle Pleistocene Transition

Quaternary sediment of the South Yellow Sea (SYS) is usually assumed to record climatic changes, tectonic activities and major river evolutions. However, as an important terrigenous indicator, a long sequence of pollen proxy in the SYS lacks for studies of river provenance and climate changes. In this study, we focused on a 150-m pollen record in the SYS that covered most of the Quaternary period over the past 1.8 Ma. The most significant changes of pollen assemblage were caused by river provenance, that high pollen percentages of broadleaved trees such as Castanea/Castanopsis reflect a dominant provenance of the Yangtze River since ca. 1.8 Ma, with a decline trend during the Mid-Pleistocene transition (MPT) mainly between 1.1 and 0.8 Ma. The sharp increase in coniferous pollen, particularly Picea, originated from the Yellow River drainage areas, suggesting a major alteration in terrigenous pollen source from the Yangtze River to the Yellow River at ∼0.8 Ma, which agrees well with the timing of the final integration of the modern Yellow River. The high pollen quantities of Artemisia and Ephedra also shows the enhanced Yellow River provenance where most landscape was covered by semi-arid open vegetation (e.g. steppe). The alternate appearances of marine foraminifera and dinoflagellate cysts, and freshwater wetland plants (Cyperaceae, Poaceae) through the interglacial intervals from MIS 19/21 demonstrate different estuary sedimentary environments and diverse salinity, associated with the sea-level fluctuations. The pollen concentration suggests an increase in terrigenous materials towards the interglacial MIS 11 and the preliminary delta formation of the Yellow River. We propose that the terrigenous input from the Yellow River accelerated after the MPT, and combined effects of tectonic movement drove the evolution of the river delta plains in eastern China. Our data also reveal some secondary periodic changes in evergreen broadleaved forest during the past 1.8 Ma and cold-tolerant coniferous forest since particularly the MPT, which are generally linked with the 400-ka long eccentricity cycle and the variability of monsoon climate.

Effects of Neem Tree Leaf Extract (Azadirachta I Ndica A. Juss) as Defaunating Agent of Sheep (Ovis Aries L.) Fed Napier Grass (Pennisetum Purpureum Schumach)

The effectiveness of neem tree leaf extract (NTLE) as defaunating agent was compared with sodium lauryl sulphate (SLS). Ten (10) sheep was used in the comparison of defaunating agents, the neem tree leaf extract was found to cause fluctuations in ruminal pH, similar to that of sodium lauryl sulphate, effectively reducing protozoal counts (from 296,000 cells/ml to 1,000 cells/ml) and increasing bacterial population (from 10,780 colony forming units/ml to 950,000 colony forming units /ml) in the rumen of sheep. It is therefore strongly advised to use neem tree extract as defaunating agents for sheep fed Napier grass to defaunated sheep in order to maximize food utilization and animal performance.

Mulching tree leaves improve the growth, yield, and yield components of hybrid maize

The experiment was carried out at the Agroforestry Farm, Department of Agroforestry, Bangladesh Agricultural University, Mymensingh from November 2019 to March 2020 to assess the impact of tree leaf mulching on the growth, yield attributes, and yield of maize. The study used a Randomized Complete Block Design with three replications and six treatments. These treatments were: T0=Control (no mulch), T1=Akashmoni (Acacia auriculiformis) tree leaf mulch, T2=Segun (Tectona grandis) tree leaf mulch, T3=Kalo koroi (Albizia lebbeck) tree leaf mulch, T4=Jhau (Casuarina equisetifolia) tree leaf mulch, and T5=Jackfruit (Artocarpus heterophyllus) tree leaf mulch. The results showed that the Kalo koroi tree leaf mulch (T3) led to the highest values for various parameters such as plant height, number of effective tillers per plant, number of leaves per plant, leaf length, leaf diameter, number of cobs per plant, length, and diameter of cob, the weight of single cob, number of grains per cob, grain weight per cob, 100-grain weight, and grain yield of maize (221.18 cm, 0.93, 17.29, 79.26 cm, 7.30 cm, 4.18, 1.70, 21.11 cm, 6.08 cm, 212.12 g, 453.85 g, 138.91 g, 30.60 g, and 11.81 t/ha). Conversely, the lowest values were obtained in the control (T0) (no mulch), followed by T2 and T1 treatments (209.39 cm, 0.37, 12.5, 72.48 cm, 4.62 cm, 1.50, 15.03 cm, 4.44 cm, 202.19 g, 421.56 g, 111.55 g, 26.46 g, and 8.35 t/ha). Among the various tree leaf mulch treatments, it was found that the Kalo koroi tree leaf mulch performed better for vegetative growth, yield, and yield-contributing attributes in maize compared to the no mulch treatment. Therefore, it was suggested that tree leaf mulches could be a potential alternative to traditional mulches in maize cultivation. Res. Agric. Livest. Fish. Vol. 11, No. 2, August 2024: 205-214

Effects of Tree Leaves, Tannins, and Water Color on Chlorophyll Concentrations in Ponds

Leaf litter is an important input to freshwater systems. Leaves provide carbon, nutrients, and secondary compounds. We examined the effects of tree leaf species on chlorophyll a concentration—a proxy for phytoplankton biomass. We found that an input of Chinese tallow (Triadica sebiferum, invasive in the southeastern USA) and red maple (Acer rubrum) leaves resulted in lower chlorophyll concentrations than controls and other native species. These leaf species also leached tannins, resulting in a darker water color, and either may have caused the patterns observed. To separate these potential mechanisms (darker water leading to light limitation and tannin toxicity), we conducted a second experiment with a fully factorial design manipulating tannins and water color. We found that darker water resulted in the lowest chlorophyll concentration, suggesting light limitation. In the clear-water treatment, the addition of tannic acid lowered chlorophyll concentrations but also resulted in moderately darker water by the end of the experiment. The tannic acid may have been toxic to the algae, or there may have been some light limitation. Our results suggest that tannins that darken water color may substantially suppress phytoplankton and that tree species composition may influence both phytoplankton and the brownification of freshwater.

Tree architecture and leaf morphometry of Qualea grandiflora Mart. (Vochysiaceae) in a fragment of dry forest and pasture in the State of Goiás, Brazil

Investigating the functional traits of plant communities is extremely important for conserving habitats and plant species. This study aimed to evaluate the tree architecture and leaf morphometry of Qualea grandiflora (Vochysiaceae) in a fragment of semideciduous dry forest and pasture in the Boa Esperança settlement, municipality of Piracanjuba, State of Goiás, Brazil. Environmental, tree architecture, and foliar morphometry data were collected for seven trees in the semideciduous dry forest and five in the pasture area. We used the Shapiro-Wilk test to assess the normality of the collected data. The student t-test was used to compare the means of the functional traits between the two environments (forest and pasture). The average value of canopy cover was 85% for the semideciduous dry forest and 0% for the pasture. The mean values for leaf length and width were lower in the pasture. There was no significant difference in the petiole length in the two evaluated environments and for none of the functional traits related to the tree architecture. However, individuals of Qualea grandiflora grow better in the seasonal semideciduous dry forest, probably as a response to less stressful environmental conditions for this species. Thus, for sustainable exploitation by the local community, it is recommended that the tree matrices be chosen within the semideciduous dry forest area.

Leaf stomatal configuration and photosynthetic traits jointly affect leaf water use efficiency in forests along climate gradients.

Water use efficiency (WUE) represents the trade-off between carbon assimilation and water loss in plants. It remains unclear how leaf stomatal and photosynthetic traits regulate the spatial variation of leaf WUE in different natural forest ecosystems. We investigated 43 broad-leaf tree species spanning from cold-temperate to tropical forests in China. We quantified leaf WUE using leaf δ13C and measured stomatal traits, photosynthetic traits as well as maximum stomatal conductance ( ) and maximum carboxylation capacity ( ). We found that leaves in cold-temperate forests displayed 'fast' carbon economics, characterized by higher leaf nitrogen, Chl, specific leaf area, and , as an adaptation to the shorter growing season. However, these leaves exhibited 'slow' hydraulic traits, with larger but fewer stomata and similar , resulting in higher leaf WUE. By contrast, leaves in tropical forests had smaller and denser stomata, enabling swift response to heterogeneous light conditions. However, this stomatal configuration increased potential water loss, and coupled with their low photosynthetic capacity, led to lower WUE. Our findings contribute to understanding how plant photosynthetic and stomatal traits regulate carbon-water trade-offs across climatic gradients, advancing our ability to predict the impacts of climate changes on forest carbon and water cycles.

EFS-Former: An Efficient Network for Fruit Tree Leaf Disease Segmentation and Severity Assessment

Fruit is a major source of vitamins, minerals, and dietary fiber in people’s daily lives. Leaf diseases caused by climate change and other factors have significantly reduced fruit production. Deep learning methods for segmenting leaf diseases can effectively mitigate this issue. However, challenges such as leaf folding, jaggedness, and light shading make edge feature extraction difficult, affecting segmentation accuracy. To address these problems, this paper proposes a method based on EFS-Former. The expanded local detail (ELD) module extends the model’s receptive field by expanding the convolution, better handling fine spots and effectively reducing information loss. H-attention reduces computational redundancy by superimposing multi-layer convolutions, significantly improving feature filtering. The parallel fusion architecture effectively utilizes the different feature extraction intervals of the convolutional neural network (CNN) and Transformer encoders, achieving comprehensive feature extraction and effectively fusing detailed and semantic information in the channel and spatial dimensions within the feature fusion module (FFM). Experiments show that, compared to DeepLabV3+, this method achieves 10.78%, 9.51%, 0.72%, and 8.00% higher scores for mean intersection over union (mIoU), mean pixel accuracy (mPA), accuracy (Acc), and F_score, respectively, while having 1.78 M fewer total parameters and 0.32 G lower floating point operations per second (FLOPS). Additionally, it effectively calculates the ratio of leaf area occupied by spots. This method is also effective in calculating the disease period by analyzing the ratio of leaf area occupied by diseased spots. The method’s overall performance is evaluated using mIoU, mPA, Acc, and F_score metrics, achieving 88.60%, 93.49%, 98.60%, and 95.90%, respectively. In summary, this study offers an efficient and accurate method for fruit tree leaf spot segmentation, providing a solid foundation for the precise analysis of fruit tree leaves and spots, and supporting smart agriculture for precision pesticide spraying.

Xylem embolism induced by freeze-thaw and drought are influenced by different anatomical traits in subtropical montane evergreen angiosperm trees.

Subtropical evergreen broadleaved forests distributed in montane zones of southern China experience seasonal droughts and winter frost. Previously, studies have recognized that xylem anatomy is a determinant of its vulnerability to embolism caused by drought and freezing events. We hypothesized that there is a coordination of xylem resistance to freeze-thaw and drought-induced embolism for the subtropical montane evergreen broadleaved tree species because they are influenced by common xylem structural traits (e.g., vessel diameter). We examined the branch xylem anatomy, resistance to drought-induced embolism (P50), and the percent loss of branch hydraulic conductivity after a severe winter frost (PLCwinter) for 15 evergreen broadleaved tree species in a montane forest in South China. Our results showed that P50 of the studied species ranged from -2.81 to -5.13 MPa, which was not associated with most xylem anatomical properties except for the axial parenchyma-to-vessel connectivity. These tree species differed substantially in PLCwinter, ranging from 0% to 76.41%. PLCwinter was positively related to vessel diameter and negatively related to vessel density, vessel group index, and vessel-to-vessel connectivity, but no coordination with P50. This study suggests that hydraulic adaptation to frost is important to determine the distributional limit of subtropical montane evergreen woody angiosperms.

Analysis of the genetic diversity and population structure of Tilia amurensis from China using SSR markers: Implications for conservation

Tilia amurensis is a deciduous broad-leaved tree in the Malvaceae family. It is one of the second-class key protected wild plants in China. The evaluation of genetic polymorphisms of crucial protected species is necessary for conserving germplasm resources. In this study, 15 pairs of highly polymorphic SSR primers were used to analyse the genetic diversity of eight T. amurensis populations and the population structure of nine Tilia populations distributed in China. At the population level (Na = 6.050, Ne = 2.930, I = 1.123, HO = 0.485, HE = 0.523), there was a high level of genetic diversity. The AMOVA results showed that 12 % and 88 % of the total variation occurred among and within populations, respectively. The degree of genetic differentiation was moderate (FST = 0.124), and the level of gene flow was high (Nm = 1.763). The results of UPGMA cluster analysis, PCoA and structure analysis (ΔK = 2) revealed different degrees of gene introgression between the eight T. amurensis populations and Tilia japonica as the outgroup. These findings have important implications for formulating appropriate conservation strategies.

Assisted migration outcomes for oak species and seed sources in southern Ontario, Canada

IntroductionForest assisted migration has been proposed as a means to align tree populations with shifting climate habitats under climate change. Here we report on the growth and survival of oak species and seed sources at five assisted migration trials in southern Ontario – an important transition zone between boreal and temperate ecosystems.MethodsEach trial featured one or more oak species – including red oak (Quercus rubra), white oak (Q. alba), burr oak (Q. macrocarpa), and swamp white oak (Q. bicolor) – and seed sources from Ontario, Pennsylvania, and/or Tennessee. The trials were measured for survival and height at between 7 and 13 years after planting.ResultsFor several trials and species, southern seed sources performed nearly as well as local sources. However, southern seed sources of burr oak performed significantly worse than local sources at 2 trials in eastern Ontario. These outcomes may have been influenced by reduced quality of southern seed source planting stock at these trials.DiscussionOur findings generally support previous work that suggests northward movements of seed sources of several hundred kilometers may be safe for assisted migration efforts involving broadleaf tree species. Notably, the trial sites were located at the northern range limits of two oak species in this study (Q. alba and Q. bicolor), suggesting the potential for modest range expansions in this boreal-temperate transition zone. These findings help forest managers to better understand potential assisted migration outcomes under climate change.

Rhizosphere microbial roles in phosphorus cycling during successive plantings of Chinese fir plantations

The rhizosphere, a critical interface involving soil, plant roots, and microorganisms, plays a vital role in the feedback processes between plants and soil, especially under phosphorus (P) limiting conditions typical of subtropical forests. This study used a chronosequence design to investigate first-fourth successive planting rotations of Chinese fir (Cunninghamia lanceolata) plantations in Fujian Province, China, with stands around 17 years old. We employed a modified P fractionation assay and metagenomic sequencing to explore P cycling in the rhizosphere across different plantation rotations. Rhizosphere labile P concentrations increased significantly in the fourth rotation, alongside a consistent upward trend in moderately labile P throughout successive plantings. Conversely, stable P and residual P concentrations declined during successive plantings, signaling a shift toward more accessible P forms. From metagenomic analyses, the proportion of P transport processes (transportation of phosphonate, phosphate, and inorganic phosphate) gradually increased. Notably, abundances were significantly higher in the rhizosphere soil of the fourth Chinese fir planting rotation of the K01126 gene (involved in phosphate ester mineralization), the phnD gene (associated with phosphonate transport), functional genes related to the solubilization of inorganic phosphate, such as pqqB, pqqC, pqqE, and ppa, and the phoB gene (linked to P-starvation response regulation). The results indicate that functional microbes of the rhizosphere, dominated by Proteobacteria and Acidobacteria, are instrumental in changing P cycling processes during successive plantings. The successive planting rotations of Chinese fir plantations significantly and positively impacted on the gene abundance related to the activation and uptake of P in the rhizosphere. Based on these insights, specific strategies, such as regular monitoring and application of phosphate fertilizer and adjusting rotation timing based on the soil rhizosphere P status, and incorporating native broad-leaved tree species are suggested to promote efficient P cycling, thus supporting sustainable forest management practices.

Introduction of broadleaf tree species can promote the resource use efficiency and gross primary productivity of pure forests.

Long-term pure forest (PF) management and successive planting has result resulted in "low-efficiency artificial forests" in large areas. However, controversy persists over the promoting effect of introduction of broadleaf tree species on production efficiency of PF. This study hypothesised that introduced broadleaf tree species can significantly promote both water-nutrient use efficiency and gross primary productivity (GPP)of PF. Tree ring chronologies, water source, water use efficiency and GPP were analysed in coniferous Cunninghamia lanceolata and broadleaved Phoebe zhennan growing over the past three decades. The introduction of P. zhennan into C. lanceolata plantations resulted in inter-specific competition for water, probably because of the similarity of the main water source of these two tree species. However, C. lanceolata absorbed more water with a higher nutrient level from the 40-60-cm soil layer in mixed forests (MF). Although the co-existing tree species limited the basal area increment and growth rates of C. lanceolata in MF plots, the acquisition of dissolved nutrients from the fertile topsoil layer were enhanced; this increased the water use efficiency and GPP of MF plots. To achieve better ecological benefits and GPP, MFs should be constructed in southern China.

Assessment of climatic influences on net primary productivity along elevation gradients in temperate ecoregions

Elevation gradients significantly influence net primary productivity (NPP), but the relationship between elevation, climate variables, and vegetation productivity remains underexplored, particularly in diverse ecological zones. This study quantifies the impact of elevation and climatic variables on NPP in northern Pakistan, hypothesizing that elevation modulates NPP through its influence on temperature and precipitation patterns. Using remote sensing data (MODIS ERA5) and advanced ecological models like the Eddy Covariance-Light Use Efficiency (EC-LUE) model and the Thornthwaite Memorial Model (TMM), we analyzed Gross Primary Productivity (GPP) dynamics across various vegetation types and elevations from 2001 to 2023. Our findings show a mean annual NPP of 323.46 g C m-2 a-1, with an annual increase of 5.73 g C m-2 a-1. Significant elevation-dependent variations were observed, especially in mid-elevation zones (401 to 1600 meters), where NPP increased at a rate of 0.174 g C m-2 a-1 per meter (R² = 0.808, p < 0.01). In contrast, higher elevations (2800-5200 meters) exhibited a decline in NPP, decreasing by -0.171 g C m-2 a-1 per meter (R² = 0.905, p < 0.001). Temperature and precipitation were key drivers, with precipitation positively correlating with NPP across all vegetation types, particularly in Evergreen Needleleaf and Broadleaf Trees. The EC-LUE model's GPP estimates closely matched MODIS data (R² = 0.82), demonstrating the model's reliability. These findings highlight the critical role of elevation and climatic factors in vegetation productivity and underscore the need for targeted ecological management and conservation strategies. The insights from this research are vital for global climate adaptation policies and sustainable development goals, contributing to ecological resilience and carbon sequestration efforts worldwide.

Determinants of tree population temporal stability in a temperate mixed forest over a gradient of nitrogen addition

Nitrogen (N) deposition is a significant threat to the functioning of forests and negatively impacts the delivery of forest goods and services. Contemporary management approaches seek to adapt forests to such N-deposition stressors, but to date how plant populations in natural forests respond to N deposition and what factors determine the contrasting responses among populations are still unclear. Here, we investigated the impact of N-addition (control: 0 kg ha−1 yr−1; low: 25 kg ha−1 yr−1; medium: 50 kg ha−1 yr−1; high: 75 kg ha−1 ha yr−1) on tree population temporal stability and how initial tree size, mycorrhizal type, and leaf N content (LNC; as a surrogate for functional trait composition) mediate tree population responses to N-addition in a Korean pine and mixed broadleaved dominated temperate forest in northern China. We quantified tree species population temporal stability as the ratio of mean to standard deviation of the year-by-year stem increments recorded in individual trees from 2015 to 2022 experimental period. The results showed different temporal stabilities of tree species among four N-addition levels, with the highest population stability observed within the high N-addition plots. Furthermore, initial tree size had significantly (p < 0.001) positive effects on population temporal stability. The effect of LNC and initial tree size were also contingent on the level of N applied. Specifically, increase in tree population LNC reduced population temporal stability in all plots where N was added. Our results imply that retention of large-sized trees and species with resource-conservative strategies (e.g., low LNC) could enhance forest stability under N deposition.