Review

Prevalence and underlying mechanisms of phylosymbiosis in land plants
Li-Qun Lin, Luke R. Tembrock, Li Wang
2024, 17 (6): rtae051.
doi:10.1093/jpe/rtae051
Abstract ( 137 )   PDF（pc） (1941KB) ( 104 )   Save
Phylosymbiosis, the congruence of microbiome composition with host phylogeny, is a valuable framework for investigating plant–microbe associations and their evolutionary ecology. This review assesses the prevalence of phylosymbiosis across the plant kingdom, elucidates the fundamental ecological and evolutionary processes contributing to its occurrence based on previous research and explores commonly used methods for identifying phylosymbiosis. We find that the presence of phylosymbiosis may be influenced by both phylogenetic distance and the taxonomic level at which host plants are examined, with the strength of associations potentially decreasing as the taxonomic scale becomes finer. Notably, the endophytic microbiome exhibits a stronger phylosymbiosis signal compared with the epiphytic or rhizosphere-associated microbiomes. Microorganisms such as fungi and bacteria can yield highly variable evidence for phylosymbiosis due to differences in colonization, transmission or functional characteristics. We also outline how the four community assembly processes (dispersal, selection, diversification and drift) contribute to the establishment and maintenance of host–microbe phylosymbiosis. Furthermore, we highlight the diversity of methods employed to detect phylosymbiosis, which involves three key processes: constructing host phylogenies, assessing microbial data and statistically evaluating the correlation between host phylogeny and microbial composition. Remarkably different methodologies across studies make comparisons between findings challenging. To advance our understanding, future research is expected to explore phylosymbiosis at lower taxonomic levels and investigate different microbial communities coexisting synergistically within the same host. Understanding the relative importance of community assembly processes in driving phylosymbiosis will be critical for gaining deeper insights into the ecology and evolution of host–microbe interactions.

Perspective

Integrating dehydration tolerance and avoidance in drought adaptation
Xingyun Liang and Qing Ye
2024, 17 (6): rtae073.
doi:10.1093/jpe/rtae073
Abstract ( 84 )   PDF（pc） (498KB) ( 43 )   Save

Method

PPDC: an online platform for the prediction of plant distributions in China
Jinshui Qiu, Jianwen Zhang, Yanan Wang, Huifu Zhuang
2024, 17 (6): rtae094.
doi:10.1093/jpe/rtae094
Abstract ( 74 )   PDF（pc） (1449KB) ( 37 )   Save
The survival and reproduction of plants in a particular region are closely related to the local ecological niche. The use of species distribution models based on the ecological niche concept to predict potential distributions can effectively guide the protection of endangered plants, prevention and control of invasive plants, and plant introduction and ex-situ conservation. However, traditional methods and processes for predicting potential distributions of plants are tedious and complex, requiring the collection and processing of large amounts of data and the manual operation of multiple tools. Therefore, it is difficult to achieve large-scale prediction of the potential distributions of plants. To address these limitations, by collecting and organizing a large amount of basic data, occurrence records, and environmental data and integrating species distribution models and mapping techniques, a workflow to automatically predict the potential distributions of Chinese plants was established, thus the innovative work of predicting the potential distributions of 32 000 species of plants in China was completed. Furthermore, an online platform for predicting plant distributions in China based on visualization technology was developed, providing a basis for sharing the prediction results across a wide range of scientists and technologists. Users can quickly access information about the potential distributions of plants in China, providing a reference for the collection, preservation, and protection of plant resources. In addition, users can quickly predict the potential distribution of a certain plant in a certain region across China according to specific needs, thus providing technical support for biodiversity conservation.

Research Articles

Sex-specific phosphorus (P)-use and -acquisition in dioecious Populus euphratica under different soil moisture levels
Shengwei Si, Yue He, Zongpei Li, Zhichao Xia
2024, 17 (6): rtae064.
doi:10.1093/jpe/rtae064
Abstract ( 98 )   PDF（pc） (2785KB) ( 61 )   Save
Dioecious plants show sexual dimorphism in their phosphorus (P) availability responses. However, the understanding of sex-specific strategies for P utilization and acquisition under varying soil moisture levels remains unclear. Here, we assessed a range of root functional traits, soil P properties, total foliar P concentration ([P]) and leaf chemical P fractions—inorganic P ([Pi]), metabolite P ([PM]), lipid P ([PL]), nucleic acid P ([PN]) and residual P ([PR])—as well as other leaf functional traits in female and male trees under different soil moisture levels (25% for high and 7% for low). Our results showed that females had larger specific root length under well-watered conditions, resulting in greater root foraging capacity. This led to a 36.3% decrease in soil active [Pi] in the rhizosphere and a 66.9 % increase in total foliar [P], along with all five foliar chemical P fractions ([Pi], [PM], [PL], [PN] and [PR]) compared with males. However, males exhibited significantly higher photosynthetic P utilization efficiency than females. Especially under low soil moisture levels, males exhibited a significant reduction in soil active organic P, coupled with a large increase in the exudation of soil phosphatases and carboxylates. Furthermore, the proportion of [PM] in total foliar [P] was 42.0% higher in males than in females. Mantel and Spearman correlation analyses revealed distinct coordination and trade-offs between foliar P fraction allocation and below-ground P acquisition strategies between the two sexes. Leveraging these sex-specific strategies could enhance the resilience of dioecious populations in forest plantations facing climate-induced variability.

Comparison on stress memory of two Hypnaceae moss species to haze
Binyang Liu, Xinru Zhang, Gaoming Jiang
2024, 17 (6): rtae066.
doi:10.1093/jpe/rtae066
Abstract ( 50 )   PDF（pc） (3241KB) ( 28 )   Save
Industrialization and the rapid growth of economies have caused severe environmental pollution, which might impact the survival of sensitive species. In this study, we investigated the defense responses of two common mosses with varying anti-haze capacities, Hypnum callichroum and Homomallium incurvatum, in response to simulated haze pollution. Photoprotection and antioxidant mechanisms of both mosses were measured immediately after the first exposure to the haze treatment, followed by the initial recovery stage and again after exposure to secondary stress and secondary recovery. Haze exposure caused severe oxidative stress and photodamage in both H. callichroum and H. incurvatum. Metabolic processes such as photorespiration, the ascorbate–glutathione cycle and secondary metabolism—which play roles in defense responses—were significantly activated in both moss species after haze treatment. During the recovery following haze stress, H. callichroum exhibited a significant stress memory response, as evidenced by the greater accumulation of several memory substances, including xanthophylls and phenolic acids. However, H. incurvatum did not exhibit a strong stress memory response, which might explain its relatively inferior anti-haze capacity in the natural environment.

Clonal plasticity and trait stability facilitate knotweed invasion in Europe
Pei-Pei Cao, Wan-Dong Yin, Jing-Wen Bi, Tian-Tian Lin, Sheng-Yu Wang, Hang Zhou, Zhi-Yong Liao, Lei Zhang, Madalin Parepa, Rui-Ting Ju, Jian-Qing Ding, Ming Nie, Oliver Bossdorf, Christina L. Richards, Ji-Hua Wu and Bo Li
2024, 17 (6): rtae067.
doi:10.1093/jpe/rtae067
Abstract ( 81 )   Save
Invasive plant species pose signifcant ecological and economic threats due to their establishment and dominance in non-native ranges. Previous studies have yielded mixed results regarding the plants’ adaptive mechanisms for thriving in new environments, and particularly, little is known about how the phenotypic plasticity of growth and defense-related traits may facilitate plant invasion. This study addressed these uncertainties by employing the aggressive weed Reynoutria japonica as a study model. We examined the differences in growth, defenserelated traits and biomass allocation between R. japonica populations from native and introduced ranges grown in two common gardens with distinct climate conditions. Our results demonstrated that while the introduced populations did not exhibit increases in height and total dry mass, nor reductions in leaf defense levels, their investment in leaf production was signifcantly higher compared to the native populations. Additionally, introduced populations displayed greater phenotypic plasticity in clonal ramet but less phenotypic plasticity in biomass production than native populations across varying environments. These fndings highlight the roles of phenotypic plasticity and specifc trait adaptations, such as clonality, in the successful invasion of R. japonica. This study has important implications for managing invasive plant species under changing environmental conditions.

Differential phenological responses to temperature among various stages of spring vegetation green-up
Nan Jiang, Miaogen Shen and Zhiyong Yang
2024, 17 (6): rtae063.
doi:10.1093/jpe/rtae063
Abstract ( 109 )   PDF（pc） (4220KB) ( 58 )   Save
Vegetation green-up is occurring earlier due to climate warming across the Northern Hemisphere, with substantial infuences on ecosystems. However, it is unclear whether temperature responses differ among various green-up stages. Using high-temporal-resolution satellite data of vegetation greenness and averaging over northern vegetation (30–75° N), we found the negative interannual partial correlation between the middle green-up stage timing (50% greenness increase in spring–summer) and temperature (R_P = −0.73) was stronger than those for the onset (15% increase, R_P = −0.65) and end (90% increase, R_P = −0.52) of green-up during 2000–2022. Spatially, at high latitudes, the middle green-up stage showed stronger temperature responses than the onset, associated with greater low-temperature constraints and stronger control of snowmelt on green-up onset as well as greater spring frost risk. At middle latitudes, correlations with temperature were similar between the onset and middle stages of green-up, except for grasslands of the Mongolian Plateau and interior western USA, where correlations with temperature were weaker for the middle stage due to water limitation. In contrast, the end of the green-up showed weaker temperature responses than the middle due to insuffcient water and high climatic temperature during the end of the green-up in most of the study region, except for cold regions in the interior western USA, western Russia and the Tibetan Plateau, where temperature was still a main driver during end of green-up. Our fndings underscore the differences in temperature responses among green-up stages, which alters the temporal alignment between plants and environmental resources.

Effects of thinning and ground cover plants on soil bacterial community composition and diversity in Picea asperata plantations within giant panda habitats
Xiang Tao, Qiuju Xiao, Huanhuan Shao, Weiguo Tu, Ling Li, Yuanbin Zhang, Hao Jiang
2024, 17 (6): rtae069.
doi:10.1093/jpe/rtae069
Abstract ( 99 )   PDF（pc） (1950KB) ( 45 )   Save
Forest thinning and ground cover plant management play crucial roles in habitat enhancement, yet their effects on soil microbiota remain poorly understood. This study examines their impact on soil properties and bacterial communities in artifcial spruce forests (Picea asperata) within China’s Huangtuliang ecological corridor, a crucial habitat for giant pandas. Thinning signifcantly alters soil pH and total phosphorus (TP) levels, with minimal changes observed in total nitrogen (TN), microbial biomass carbon (MBC) and nitrogen (MBN). The combined effect of thinning and ground cover presence increases soil organic carbon (SOC) to 65.47 g/kg, contrasting with its absence. Thinning enhances the abundance of Proteobacteria, Acidobacteria and Chlorofexi while reducing Actinobacteria. Conversely, ground cover removal decreases Proteobacteria and Bacteroidetes but increases Chlorofexi, Verrucomicrobia and Rokubacteria. These changes lead to reduced bacterial community diversity, as indicated by a lower Shannon diversity index and distinct community composition differences demonstrated through beta-diversity analysis. Soil pH, TP and MBN are crucial in maintaining bacterial community structure, with pH and TP exhibiting the strongest correlations. Network analysis confrms the signifcant infuence of TP and pH on bacterial genera across various phyla. This study reveals the role of stochastic processes in highelevation, low-temperature ecological corridors (R² = 0.817), with thinning’s impact varying depending on the ground cover presence, thus enhancing effects post-removal by reducing dispersal limitation (migration rate, m = 0.96). These fndings highlight the ecological implications of habitat management in sensitive ecosystems and advance our understanding of microbial dynamics in critical habitats.

Effects of leguminous green manure–crop rotation on soil enzyme activity and stoichiometry
Meixia Liu, Zonghao Hu, Yi Fan, Bin Hua, Wei Yang, Shuang Pang, Rong Mao, Yang Zhang, Keyu Bai, Carlo Fadda, Paola De Santis, Nadia Bergamini, Aziza Usmankulova, Buriyev Salimjan Samedjanovich and Ximei Zhang
2024, 17 (6): rtae065.
doi:10.1093/jpe/rtae065
Abstract ( 53 )   PDF（pc） (2577KB) ( 29 )   Save
As a crucial strategy for sustainable agricultural production, green manure–crop rotation can regulate soil nutrient cycling and decrease the reliance on nitrogen fertilizers. However, we still lack a comprehensive understanding of the changes in soil eco-enzyme activities, microbial metabolism and nutrient limitations caused by leguminous green manure–crop rotation. Here, we conducted field experiments of leguminous green manure–crop rotation across China to analyze soil extracellular enzyme activities, specifically β-glucosidase (BG), N-acetyl-β-d-glucosaminidase (NAG), leucine aminopeptidase (LAP) and acid phosphatase (AP). The study revealed that long-term green manure–crop rotation increased carbon and nitrogen accumulation in farmland, with a significant average increase of 20.1% and 36.4% in BG, AP enzyme activities in topsoil, while showing a decrease in ln(NAG + LAP):ln(AP) ratios. The ratios of ln(BG):ln(NAG + LAP) and ln(NAG + LAP):ln(AP) in soil across various regions were typically below 1:1, indicating that soil microbial activity is more constrained by nitrogen and phosphorus nutrients rather than by carbon. Precipitation, temperature, soil total carbon (TC) and total nitrogen (TN) were identified as key environmental factors for extracellular enzyme activities and stoichiometric ratios. Our study highlights that the green manure–crop rotation alleviates nitrogen limitation while enhancing phosphorus limitation, and is closely related to the accumulation of TC and TN in the soil.

Increasing biochar diversity promotes the impacts of plant diversity on remediating cadmium in soil
Hao-Ming Yuan, Wei Xue , Sergio Roiloa Jun Yao and Fei-Hai Yu
2024, 17 (6): rtae068.
doi:10.1093/jpe/rtae068
Abstract ( 64 )   PDF（pc） (1340KB) ( 40 )   Save
Biochar is a promising material for soil remediation. However, most studies testing the roles of biochar in soil remediation have considered the use of single types of biochar, and the role of biochar diversity, as well as its interaction with species diversity of plant communities, has rarely been considered. We hypothesize that biochar diversity can infuence the impacts of plant diversity on soil remediation. We grew grassland communities consisting of three or six plant species in cadmium (Cd)-contaminated soil mixed with one, two or four types of biochar, with no grassland community and no biochar addition as the controls. Without plant communities or with communities consisting of three species, total Cd was signifcantly lower in the soil mixed with four types of biochar than in the soil without biochar or mixed with one or two types of biochar. With communities consisting of six species, total Cd decreased with the increasing number of biochar types. Without biochar addition, soil total Cd was not infuenced by species richness, but with biochar addition, it was lower in the presence of communities with six species than in the absence of plant communities irrespective of how many types of biochar were added. Also, soil total Cd was lower in the presence of communities with six than with three plant species when two or four types of biochar were added. Our study indicates that increasing biochar diversity can promote the impact of plant diversity on remediating soil contaminated by heavy metals such as Cd.

Precipitation-induced soil properties and plant communities mediate root strategies in an alpine meadow
Yi-Heng Li, Xin-Di Zhang, Min Liu, Chang-Ting Wang, Lerdau Manuel, and Lei Hu
2024, 17 (6): rtae072.
doi:10.1093/jpe/rtae072
Abstract ( 50 )   PDF（pc） (1579KB) ( 26 )   Save
Plant roots show flexible traits to changing precipitation, but the factors driving root trait covariation remain poorly understood. This study investigated six key root traits and explored the potential driving factors, including plant community characteristics and soil properties, in the Zoige alpine meadow across five precipitation gradients: natural precipitation (1.0P), a 50% increasing precipitation (1.5P), and 30%, 50% and 90% decreasing precipitation (0.7P, 0.5P and 0.1P, respectively). Our results demonstrated distinct root trait responses to changes in precipitation. Both increasing (1.5P) and decreasing precipitation (0.1P, 0.5P and 0.7P) inhibited root diameter (RD), specific root length (SRL) and specific root area compared with 1.0P. Conversely, root tissue density and root nitrogen content increased under decreasing precipitation but declined under 1.5P. With increasing precipitation, root foraging strategies shifted with thinner RD and larger SRL to that with a larger diameter. Shifts in root strategies were primarily influenced by soil properties, specifically soil water content and available nitrogen. Additionally, root strategies in surface soils (0–10 cm) were mainly related to the grass and sedge coverage, whereas in deeper soils (10–20 cm) root strategies were related to overall plant community coverage and biomass. Our findings indicate that root trait variations and strategies in alpine meadows are co-driven by soil properties and plant communities in response to changing precipitation.

Divergent hydraulic and gas-exchange strategies in two closely related Salix species
Muhammad Waseem, Guang-Qian Yao, Md Mahadi Hasan, Yan-Ru Li, Shi-Hua Qi, Lin Cai, Di Yang, Xiang-Wen Fang
2024, 17 (6): rtae075.
doi:10.1093/jpe/rtae075
Abstract ( 79 )   PDF（pc） (2049KB) ( 6 )   Save
Understanding the physiological mechanisms that trees employ to cope with drought-induced mortality is crucial for predicting their responses to a changing climate. Salix species exhibit distinct habit distributions, with Salix babylonica growing in wet habitats and Salix matsudana growing in relatively dry habitats. The objective of this study was to compare hydraulic and gas-exchange traits between these two closely related Salix species with contrasting natural habitats. S. matsudana had lower photosynthesis (A_max), lower stomatal conductance (g_s) and lower stem and leaf hydraulic conductance, but it exhibited higher water use efficiency (WUE_i), higher hydraulic safety and wider leaf-to-stem vulnerability segmentation as well as narrower, shorter and denser conduits and a lower ratio of leaf area to sapwood area than S. babylonica. These findings suggest that variations in hydraulic vulnerability and gas-exchange traits enable closely related Salix species to adapt to different habitats.

Planting environment affects effectiveness of genotype diversity in increasing biomass and yield of a spring wheat mixture
Cong Zhang, Yanlei Du, Tong Yang, Christian Schöb, Fengmin Li
2024, 17 (6): rtae076.
doi:10.1093/jpe/rtae076
Abstract ( 108 )   PDF（pc） (1730KB) ( 10 )   Save
Genotype diversity is an important component of biodiversity, and has potential positive effects on ecological processes, such as primary productivity. Recent studies suggest that crop cultivar mixtures can improve biomass or yield, however, the generality and size of this effect, as well as the underlying mechanisms are unclear. We selected nine genotypes of spring wheat (Triticum aestivum L.), and tested monocultures (of one genotype) and mixtures (of nine genotypes) to verify whether the positive effect of genotype diversity could be observed. Meanwhile, we arranged two planting environments, real field and artificial pot conditions, to clarify how the effect of genotype diversity depends on environmental conditions. Results showed that the effect of genotype diversity was highly dependent on the planting environment; compared with monocultures, mixtures significantly improved aboveground biomass and grain yield of spring wheat in pots by 14.5% and 8.2%, respectively, while no improvements were observed in the field. In pots, positive complementarity effects dominated the positive net effect by offsetting negative sampling effects, while no significant diversity effects were observed in the field. The greater trait differences in pots were more favorable for resource-use complementarity and reducing intraspecific competition, which might be the main reason for the large positive complementary effect in pots. Our results suggest that increasing the biomass and grain yield of spring wheat by providing genotypic diversity was supported by specific ecological mechanisms and could be achievable. However, environmental conditions in actual production may limit its efficacy, and more extensive field experiments are thus needed to verify the effectiveness of genotype diversity.

Association between CH₄ uptake and N₂O emission in grassland depends on nitrogen inputs
Yiming Ren, Yangxinzi Zao, Ying Zhao, Rui Su, Guowei Yang, Xiran Li, Jingru Kang, Yiyu Shi, Yuru Xie, Nannan Wang, Yunjiang Zuo, Kexin Li, Liyuan He, Xiaofeng Xu, Lihua Zhang
2024, 17 (6): rtae078.
doi:10.1093/jpe/rtae078
Abstract ( 49 )   PDF（pc） (2080KB) ( 5 )   Save
Increasing nitrogen (N) input has been recognized as one of the important factors influencing methane (CH₄) uptake and nitrous oxide (N₂O) emission in arid and semiarid grasslands. Numerous studies have examined the spatiotemporal variations of CH₄ and N₂O fluxes in various ecosystems; however, the variation of the interplay between CH₄ uptake and N₂O emission with increasing N has not yet been well understood. This study explored the relationship between CH₄ uptake and N₂O emission in a semiarid grassland in Inner Mongolia, northern China, under a gradient of 12-year N additions. We found a synergistic relationship at low-N levels, where CH₄ uptake and N₂O emission are positively correlated. Conversely, an antagonistic interaction emerged with a negative correlation between CH₄ uptake and N₂O emission observed at high-N levels, which was evidenced by a 33.62% decrease in CH₄ uptake and a 264.91% increase in N₂O emission. Further independent analysis, covering at least five N addition levels across grassland ecosystems in China, confirmed the general pattern: three of four cases showed a synergistic relationship at low-N levels and an antagonistic relationship at high-N levels. Given the increasing N deposition in the future, the dynamics between CH₄ uptake and N₂O emission are critical for understanding the impact of external N input on net greenhouse gas emission and consequent global climate change.

Abundance and diversity of the culturable nectar mycobiome in Rhododendron catawbiense varies with elevation
Daniel A Barker, Ayesha Khan, Ekaterina Kaverina, Carlos Martel, Gerardo Arceo-Gómez
2024, 17 (6): rtae079.
doi:10.1093/jpe/rtae079
Abstract ( 40 )   PDF（pc） (893KB) ( 14 )   Save
The nectar microbiome can influence pollinator choice and plant fitness. Previous research has shown that changes in environmental conditions at large spatial scales can influence nectar microbiome composition. However, little is known about how changes in climate with increasing elevation affect nectar microbiome abundance and composition. Here, we describe the culturable nectar mycobiome (CNMB) of Rhododendron catawbiense (Ericaceae) by quantifying colony abundance, identity and richness of fungal genera. We further evaluate how the CNMB abundance, diversity and composition (i.e. the fungal species within the nectar microbiome) varies at two different elevations. Nectar samples were collected from R. catawbiense individuals at a high and low elevation and were cultured on yeast agar with 0.01% chloramphenicol media. Fungal colonies were categorized morphologically, quantified and then identified using DNA barcoding. In total, 2822 fungal colonies were recorded belonging to six genera across both elevations. Elevation did not influence CNMB diversity (Simpson’s diversity index) or genera richness per flower, however only three genera were found at the high elevation while six were found at the low elevation. Elevation had a significant effect on colony abundance with a 95% increase in the number of colonies in nectar samples at low compared with the high elevation. Variation in abundance and the overall genera composition of fungal colonies across elevations may have the potential to affect nectar quantity and quality and ultimately pollination success. This study adds to our understanding of the drivers of CNMB composition across spatial scales and its potential implications for plant–pollinator interactions.

Cyclical drought and herbivore threats are potential causes of leaf variegation dimorphism in Cypripedium forrestii
Lie-Wen Lin, Hua Huang, Wei-Wei Liu, Wei-Bang Sun
2024, 17 (6): rtae081.
doi:10.1093/jpe/rtae081
Abstract ( 20 )   PDF（pc） (3068KB) ( 10 )   Save
Leaf variegation, the mosaic of colors on the leaf surface, can be developed by certain plant species without external influence. Although it may be associated with a variety of functions, the stable existence of different leaf color morphs within a plant species has not been fully explained by previous studies. This study focuses on the two leaf morphs of Cypripedium forrestii, an endangered lady slipper orchid, and compares their micromorphological structure, photosynthetic potential, differentially expressed genes (DEGs), and ecological features to gain a comprehensive understanding of the underlying leaf variegation polymorphism. Our findings demonstrate that leaf variegation is not pathological and does not affect photosynthetic potential. Additionally, it significantly reduces herbivory damage. We found that the probability of herbivory and leaf area loss for variegated leaves was notably higher under drought conditions. Therefore, variegated individuals may be more adaptive under such conditions, while non-variegated ones may be more cost-effective in normal years. These results suggest that different leaf color morphs may be favored by varying environmental conditions, and leaf polymorphism may be a legacy of ancient climate and herbivore fluctuations.

Are shade tolerance and canopy gradient affecting twig-leaf trait scaling relationships in temperate forests?
Tao Zeng, Hongkun Fan, Guangze Jin, Zhili Liu
2024, 17 (6): rtae082.
doi:10.1093/jpe/rtae082
Abstract ( 43 )   PDF（pc） (1564KB) ( 8 )   Save
Scaling relationships among twig size, leaf size and leafing intensity is pivotal in understanding plant resource allocation and carbon investment strategies. However, it remained unclear how these relationships might maintain stability across genetic traits (shade tolerance) and canopy gradients (microclimates). We investigated eight different shade-tolerant tree species within five mixed broad-leaved-Korean pine (Pinus koraiensis) forests in Northeast China. Employing linear mixed-effects models and phylogenetically independent contrasts, we examined the scaling relationships between twig-leaf size and leafing intensity. Shade tolerance altered the scaling relationships between twig and leaf size, as well as leafing intensity. We discovered that the scaling relationships between twig cross-sectional area and individual leaf area, leafing intensity and between individual leaf mass and leafing intensity were allometric (slope ≠ −1 or 1). However, the relationship between individual leaf area and individual leaf mass was isometric (slope = 1). Moreover, these scaling relationships exhibited consistent trends across canopy gradients, with shade tolerance playing a critical role in the coordinated evolution of twigs and leaves across these gradients. These results emphasized the significant role of shade tolerance in coordinating the covariation patterns between plant leaves and twigs, adopting conservative strategies in heterogeneous microclimates.

Climate warming advances plant reproductive phenology in China’s northern grasslands
Lu Bai, Lei Tian, Zhiguo Ren, Xiaohui Song, Kailiang Yu, Lin Meng, Zhanfeng Hou, Haiyan Ren
2024, 17 (6): rtae080.
doi:10.1093/jpe/rtae080
Abstract ( 55 )   PDF（pc） (2208KB) ( 26 )   Save
Despite much recent progress, our understanding of plant phenology response to climate change remains incomplete. In particular, how and to what extent climate warming affects the vegetative and reproductive phenology of different plant functional groups in northern grassland ecosystems remains largely unexplored. Here, we compiled data of 1758 observations from 25 individual studies and carried out a meta-analysis of plant phenology in relation to temperature changes across a range of plant species and functional groups in northern China. We show that climate warming tended to extend the duration of reproductive phenology while having no effect on the duration of vegetative phenology. We also identified specific temperature sensitivities for different phenological stages: 1.73 days °C⁻¹ for budding, −3.38 days °C⁻¹ for leaf spreading and 0.56 days °C⁻¹ for yellow withered stage, respectively. Notably, warming resulted in earlier leaf spreading in shrubs and semi-shrubs, but caused a delay in the budding time of sedges. In terms of reproductive phenology, temperature sensitivity was −1.73 days °C⁻¹ for flowering time, −2.53 days °C⁻¹ for fruit ripening and −0.11 days °C⁻¹ for fruit shedding, respectively. Warming advanced the flowering and fruit repining time of all functional groups except for legumes. Our results indicate that elevated temperatures advanced reproductive phenology and extended its duration in northern grasslands, while showing no impact on vegetative phenology. Our findings demonstrate the differential responses of different functional groups to warming, highlighting the diverse growth strategies and adaptation of grassland plants in a warming world.

Intraspecific variation of multi-elements in seeds of Euptelea pleiospermum and its association with soils, climate, and leaf elements
Hao Wu, Hongjie Meng, Mingxi Jiang, Xinzeng Wei
2024, 17 (6): rtae090.
doi:10.1093/jpe/rtae090
Abstract ( 27 )   PDF（pc） (2139KB) ( 7 )   Save
Seed mineral nutrition is essential for early seedling establishment, and varies under different environmental conditions. However, the intraspecific variation of multi-elements in seeds and the relative effects of climate and soil on seed elements remain unclear, even though understanding these factors is crucial for predicting plant reproductive responses to global changes. Here, we sampled seeds from Euptelea pleiospermum across 18 populations in China. We quantified the inter-population variation of 12 elements in the seeds and analysed their relationship with soil characteristics and climatic variables. We also explored the relationship of N and P concentrations between seeds and leaves. Results showed that seed elements were highly variable across different populations, with macroelements exhibiting lower variability than most of the microelements. Along the latitudinal gradient, the concentrations of K, Ca, Fe and Al in seeds increased, while the concentrations of C and Mn decreased. The stoichiometry of seed elements did not significantly correlate with latitude. Seed element concentrations were associated with both soil and climatic variables, and the influence of soil conditions on intraspecific variations is comparable to or even greater than climatic factors. However, seed stoichiometry was less related to environmental factors. Seeds had higher P but lower N than leaves, with no correlation between seed elements and leaf elements. Our findings suggest that mountain tree species respond to different local environments by adjusting seed element concentrations while maintaining relatively stable seed stoichiometry. We emphasize that, in addition to climate change, soil conditions should be considered when predicting the influence of environmental changes on the elemental composition of plant reproductive organs.

Intraspecific variation in leaf morphology of three widespread woody species along climatic gradients
Rong Tang, Yanpei Guo, Zhiyao Tang
2024, 17 (6): rtae091.
doi:10.1093/jpe/rtae091
Abstract ( 39 )   PDF（pc） (1121KB) ( 13 )   Save
The variation and plasticity of leaf morphology play a pivotal role in the response to environmental changes for plant individuals. Discovering the large-scale pattern of such variation can reveal plants’ general adaptive strategies. We analysed leaf morphology of three widespread woody species in the northern hemisphere using specimen data from the iDigBio and GBIF databases, to investigate the variations in the individual mean traits, in the inter- and intra-individual variability of traits, and in the allometry between traits, along climatic gradients. We found that larger and wider leaves were associated with warmer, wetter and low-sunlight habitats, while smaller but wider leaves are linked to higher wind speed, indicating the response of leaf morphology to multiple climate stresses. The inter-individual variation in leaf area was smaller in colder and windier conditions, suggesting the trait convergence among individuals under environmental filtering, while the intra-individual variation in leaf relative width (RW) was smaller in warmer habitats, indicating the similar growth optimum of leaves within one individual in more favourable conditions. Finally, the allometric exponent between leaf length (X-axis) and width (Y-axis) became greater under lower solar radiation and higher wind speed, while the squared correlation coefficient (r²) indicating phenotypic integration showed a decoupling trend under colder conditions, indicating that climate affected the variation tendency of leaf RW during leaf enlargement. These results reveal the common patterns of leaf morphology responding to climate variation spatially and underscore the necessity to consider inter- and intra-individual variability when examining plant responses to environmental changes.

Aridity-dependent resistance but strong resilience of grassland ANPP to naturally occurring precipitation extremes
Shijie Ning, Tao Yan, Wentao Luo, Shengli Tao, Xiaoming Zou, Yujiang Li, Zijian Shangguan, Yunna Wu, Zhenhua Zhang, Jin-Sheng He
2024, 17 (6): rtae084.
doi:10.1093/jpe/rtae084
Abstract ( 48 )   PDF（pc） (2389KB) ( 12 )   Save
Increasing intensity and frequency of climate extremes under climate change are expected to affect rainfall-constrained ecosystems, particularly grassland ecosystems in arid and semi-arid zones. However, our understanding of the effects of precipitation extremes (extreme drought or wetness) on grassland productivity, especially under naturally occurring conditions, remains limited. Here, we assembled a dataset of aboveground net primary productivity (ANPP) measurements from long-term (26–54 years) observational studies conducted in 13 grasslands worldwide to investigate the direct and legacy responses of grassland ANPP to naturally occurring precipitation extremes. We further examined changes in plant community structure (species richness, life history, growth form and photosynthetic pathway) before, during and after precipitation extremes. We found that extreme drought decreased ANPP by an average of 40%, while extreme wetness had a neutral effect on ANPP. The direct effects of both extreme drought and wetness on ANPP were aridity-dependent, with grassland vulnerability increasing with site aridity. However, we did not detect widespread legacy effects of extreme drought or wetness on ANPP. This is mainly attributable to reorganized plant community structure, which favored rapid recovery of community biomass. The aridity-dependent response of ANPP to precipitation extremes demonstrates the ambient climate-dependent resistance of grasslands to these events. Moreover, the minimal legacy effects of precipitation extremes on ANPP highlight the strong resilience of grasslands. These findings underscore the importance of integrating extreme climate conditions into forecasts of future grassland productivity and stability in a changing climate.

Regeneration and colonization abilities of invasive and native Myriophyllum species under different fragment types and lengths
Min Zou, Xiao-Wen Lin, Xiao-Dong Wu, Yuan Qin, Xu-Guang Ge, Jian-Jun Hou, Xiao-Xia Li, Shuang Peng
2024, 17 (6): rtae085.
doi:10.1093/jpe/rtae085
Abstract ( 28 )   PDF（pc） (1751KB) ( 8 )   Save
Alien invasive species usually have strong regeneration and colonization abilities. However, whether invasive species have advantages in terms of regeneration and colonization abilities over native species requires further exploration. In this study, the effects of fragment types (with and without apical tips) and lengths (5, 10 and 15 cm) on the regeneration and colonization abilities of the invasive Myriophyllum aquaticum and native M. spicatum in China were studied. Fragments of M. aquaticum and M. spicatum without apical tips had an advantage in branch formation, and their regeneration ability was stronger than that of fragments with apical tips. With longer initial fragments, the root length of M. aquaticum was longer and its colonization ability was stronger. This resulted in an increase in plant length, stem node number and biomass, with an increase in fragment length. However, the colonization ability of M. spicatum was not stronger with longer fragments. On the whole, native M. spicatum had stronger regeneration and colonization abilities than the invasive species M. aquaticum. However, M. aquaticum had a higher survival rate and plant length, enabling it to quickly occupy living spaces. Our results suggest that management needs to be strengthened for both M. aquaticum and M. spicatum to avoid biological invasion.

Depth-dependent effects of leguminous crops on soil nitrogen-fixing microbial communities
Yi-Heng Tao, Yi Fan, Shuang Pang, Shu-Han Zhang, Jing-Kuan Wang, Hong-Tao Zou, Jiu-Bo Pei, Xi-Mei Zhang
2024, 17 (6): rtae092.
doi:10.1093/jpe/rtae092
Abstract ( 35 )   PDF（pc） (3463KB) ( 12 )   Save
Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity. Current research on the effects of legumes predominantly focuses on surface soil, lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms. Here, the community structure of soil nitrogen-fixing microorganisms in three soil layers (0–20 cm, 20–50 cm and 50–100 cm) under legume and non-legume cultivation was investigated through metagenomic sequencing. We found that only in topsoil (0–20 cm) legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment. Under legume cultivation, the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers, whereas non-legume treatment displayed an inverse depth-dependent pattern. Combining soil physicochemical properties, the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture, total carbon (TC), and dissolved organic carbon (DOC) content. Both TC and DOC were identified as key drivers of these genes. Subsequently, a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops. The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually, distinct from non-legume treatment. Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation, providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.

Increasing tree phylogenetic diversity stimulates microbial functional potential in a subtropical forest
Yuantian Fang, Xunyang He, Qingquan Xie, Dejun Li
2024, 17 (6): rtae096.
doi:10.1093/jpe/rtae096
Abstract ( 33 )   PDF（pc） (3136KB) ( 7 )   Save
Soil microbial functions are closely related to ecosystem productivity, carbon sequestration and their responses to global change. Tree phylogenetic diversity (TPD) has been found to impact microbial community composition, diversity and functions, but how it modulates the linkage between microbial community facets and functions remains unclear. Here, 45 plots covering a natural gradient of TPD were selected in a subtropical forest of southwest China to explore how increasing TPD impacts soil microbial community facets and microbial functional potential. The microbial functional potential was evaluated based on the abundances of carbon, nitrogen and phosphorus cycling-related functional genes. Soil fungal alpha diversity increased significantly, but bacterial alpha diversity did not change as TPD increased. Both soil microbial network complexity and stability improved significantly with increasing TPD. Ultimately, increasing TPD promoted soil microbial functional potential by stimulating soil carbon and nitrogen availability, microbial keystone diversity and network stability collectively. These findings emphasize the critical roles of keystone taxa and network stability as microbial factors in stimulating soil microbial function in response to increasing TPD. Therefore, it is strongly recommended to increase TPD so as to stimulate soil microbial functions and other ecosystem functions when implementing afforestation or ecological restoration projects.

Spatial pattern and ecological adaptation of heterostylous and homostylous species of Primula in China
Shunqiu Li, Lisha Lyu, Tong Lyu, Dimitar Dimitrov, Yunyun Wang
2024, 17 (6): rtae089.
doi:10.1093/jpe/rtae089
Abstract ( 39 )   PDF（pc） (1026KB) ( 10 )   Save
Floral syndrome is one of the key components of plant pollination syndromes, affecting variety of evolutionary and ecological processes in angiosperms. The evolutionary transition from self-incompatible heterostyly to self-compatible homostyly occurred repeatedly in angiosperm families. Although the evolution of heterostyly and homostyly has been deeply studied, our understanding on their differences in ecological strategies is still lacking. In this work, using the floral syndrome and distributions of the Primula in China we compared the spatial pattern of floral syndrome frequency and its climatic determinants. Our results reveal that distylous and homostylous Primula have similar primary centers of species diversity in southwest China, while distylous species have larger range size than homostylous ones. Temperature seasonality is the dominant climate factor of these geographic patterns, but its effect is much stronger in distylous than in homostylous Primula. Distylous species have larger flower size and number, and fruit size than homostylous ones. Climate, especially temperature seasonality mainly influenced species range size via its effects on floral syndrome. Our study suggests that homostyly is likely derived from heterostylous ancestors in similar geographical context, and larger reproductive investment in floral phenotype may provide compensatory mechanisms for obligate out-breeding heterostyly. Future investigations regarding the evolutionary history and tolerance or resistance to environmental change between distyly and homostyly may greatly advance our understanding of their spatial pattern and adaptative differences.

Impacts of nitrogen deposition on Zanthoxylum bungeanum and intercropped plants: assessing growth, chlorophyll fluorescence and yields across diverse cultivation systems
Zilong Li, Kaiwen Pan, Xiyang Li, Sizhong Wang, Xue Tan, Dan Huang
2024, 17 (6): rtae097.
doi:10.1093/jpe/rtae097
Abstract ( 43 )   PDF（pc） (1000KB) ( 8 )   Save
The study aimed to thoroughly investigate the effects of nitrogen deposition on the growth, chlorophyll fluorescence and yield of Zanthoxylum bungeanum Maxim. in both monoculture and intercropping systems with Capsicum annuum L. and Glycine max. The research provided a detailed evaluation of how nitrogen deposition influenced soil and plant parameters within these intercropping systems. Key findings include: (i) In the Z. bungeanum monoculture, nitrogen deposition led to a 346.5% increase in soil NO₃⁻ levels, significantly affecting chlorophyll fluorescence parameters and decreasing soil pH. (ii) In the Z. bungeanum–C. annuum intercropping system, nitrogen deposition influenced the growth and chlorophyll fluorescence of both crops and resulted in a 261.5% increase in the root length of C. annuum. (iii) In the Z. bungeanum–G. max system, nitrogen deposition negatively impacted the chlorophyll fluorescence of G. max, reduced Z. bungeanum yields by 89.3% and altered its chlorophyll fluorescence parameters. These changes likely hindered the nitrogen-fixing capacity of G. max due to altered soil conditions. Overall, the Z. bungeanum–C. annuum system showed superior performance by enhancing soil NO₃⁻-N content. In contrast, the Z. bungeanum–G. max system experienced reduced yields due to the adverse effects of nitrogen deposition on symbiotic nitrogen fixation. These findings are crucial for developing agricultural strategies aimed at improving crop adaptability and yield in response to environmental changes.

Asymmetric effects of planting pattern and density on leaf-height traits of Glycine max and Amaranthus retroflexus
Ping Lu, Yan Pang, Huai-Jing Wang, Zi-Han Zhang, Xin Dai, Xue-Wei Bing, Qiu-Yu Yuan
2024, 17 (6): rtae101.
doi:10.1093/jpe/rtae101
Abstract ( 18 )   PDF（pc） (5981KB) ( 3 )   Save
Environmentally sustainable weed management is crucial to meet the increasing demand for food. Previous studies have demonstrated that improving spatial uniformity and planting density can effectively suppress weeds. However, research on how planting patterns (PPs) affect the functional traits of crops and weeds is limited. In 2019 and 2021, we conducted a field experiment to compare the functional traits and biomass of Glycine max and Amaranthus retroflexus in two PPs—row (R) and equidistant (E)—with varying combinations of G. max and A. retroflexus densities. We found that the equidistant planting pattern (EPP) amplified the competitive ability of G. max in size-asymmetric competition with A. retroflexus, and this advantage increased alongside higher G. max density, primarily due to functional traits related to light acquisition. In the EPP, G. max established a closed canopy during the early growth stage, reducing light availability to A. retroflexus. This advantage was reflected in higher leaf area index (LAI) and leaf dry weight for G. max in the EPP than in the row planting pattern (RPP), while A. retroflexus experienced reduced LAI and plant height due to increased shading in the EPP. Consequently, the EPP enhanced the total biomass and yield of G. max by an average of 40.8% and 37.7%, respectively, while the biomass of A. retroflexus decreased by an average of 34.5% compared with the RPP. These results suggest that adopting an EPP with a high density of G. max, could be an effective strategy for suppressing A. retroflexus and improving crop yield.

Effects of nitrogen and phosphorus addition on soil respiration in a soybean cropping system
Jingyuan Yang, Qi Xu, Yuxuan He, Meiguang Jiang, Minglu Ji, Linyu Qi, Huan Qi, Cancan Zhao, Yuan Miao, Shasha Liu, Yanfeng Sun
2024, 17 (6): rtae093.
doi:10.1093/jpe/rtae093
Abstract ( 45 )   PDF（pc） (2802KB) ( 19 )   Save
Soil respiration is an important pathway of carbon release from the terrestrial biosphere to the atmosphere, which plays a key role in ecosystem carbon cycling. However, the response and mechanism of soil respiration to nitrogen and phosphorus addition in legume plants are still unclear. Here, a pot experiment planted with soybean (Glycine max (L.) Merr.) was conducted to investigate the effects of nitrogen (N) and phosphorus (P) addition on soil respiration. Four treatments were designed: control, N addition, P addition, and both N and P addition. Soil respiration was measured twice a month from June to September in 2022. Our results showed that nutrient addition treatments presented significantly negative effects on soil respiration. In particular, nitrogen addition not only directly affected soil respiration, but also indirectly impacted soil respiration by altering soil nitrate nitrogen content. Elevated soil nitrate nitrogen content could inhibit soybean root nodule number and reduce biomass allocation to roots, thereby decreasing soil respiration. Furthermore, phosphorus addition and nitrogen–phosphorus co-addition strongly inhibited soybean nodulation by changing soil pH value, thus inhibiting soil respiration of soybean. The findings provide baseline information for optimizing nutrient management in legume crops.

Increasing plant species diversity aggravates microbial phosphorus limitation but alleviates microbial carbon limitation in a subtropical forest
Kun Gao, Hu Du, Zihong Zhu, Yuantian Fang, Dejun Li
2024, 17 (6): rtae100.
doi:10.1093/jpe/rtae100
Abstract ( 22 )   PDF（pc） (2948KB) ( 12 )   Save
The relative limitation of microbes by soil organic carbon (SOC), nitrogen (N) and phosphorus (P) is linked with soil microbial activities, so how change of plant species diversity (PSD) affects microbial resource limitation would partly determine its impacts on SOC dynamics and nutrient cycling. However, the responses of microbial resource limitation to increasing PSD have poorly explored. Here, 45 plots covering a natural PSD gradient were used to investigate the effects of PSD on microbial resource limitation in a subtropical forest. Extracellular enzymatic stoichiometry along with a laboratory N and P addition experiment were used to determine microbial resource limitation. Contents of microbial biomass C, N and P significantly increased, but C:P and N:P ratios in microbial biomass were unchanged as PSD increased. Soil microbes were generally co-limited by C and P, but not by N across the 45 plots. Increasing PSD did not alter microbial N limitation, alleviated microbial C limitation and aggravated microbial P limitation. The alleviated microbial C limitation or aggravated microbial P limitation was attributed to increased soil C availability but decreased P availability, which resulted in stimulated soil C:P and N:P ratios and in turn greater C:P and N:P imbalance between soil and microbial biomass under higher PSD. Our results highlight the divergent effects of increasing PSD on microbial resource limitation. Considering that microbial C and P limitations are widespread, the patterns observed in the current study should be applicable broadly.

Coordination between leaf pH and other leaf traits are divergent among life-forms and eco-geographic regions in plants of northern China
Sining Liu, Jiashu Chen, Yan Luo, Junpeng Ren, Yahan Chen, Zhengbing Yan, Wenxuan Han
2024, 17 (6): rtae103.
doi:10.1093/jpe/rtae103
Abstract ( 34 )   PDF（pc） (3767KB) ( 16 )   Save
As a key functional trait affecting many physiological processes, leaf pH is closely related to other leaf traits at the local scale. Nevertheless, whether and how leaf pH is linked with other leaf functional traits across geographic scales remains unclear. A field survey in northern China was conducted to investigate the relationships between leaf pH and some key leaf structural (specific leaf area, SLA; leaf dry matter content, LDMC) and chemical traits (elemental concentrations; total dissolved solids, TDS; practical salinity), as well as the effects of environmental factors on these relationships. Our results showed that the trait coordination may vary in degree or direction across eco-geographic regions (arid vs. non-arid regions) and life-forms (woody vs. herbaceous plants). Generally, leaf pH was negatively related to SLA, but positively related to TDS and salinity. However, leaf pH and LDMC were negatively correlated in arid regions but positively correlated in non-arid regions; leaf pH covaried with N (similarly, with Ca, Mg and Na) in the same direction for both herbaceous and woody plants in arid regions, but not in non-arid regions. Climatic factors mainly influenced the relationships of leaf pH with leaf Ca and Fe concentrations, while soil factors mostly affected those with leaf P, Ca and Mn concentrations. Our findings highlight the divergent coordination between leaf pH and other leaf traits across life-forms and eco-geographic regions and may shed light on the in-depth understanding of the role of acid-base balance in plant eco-physiological processes and ecological adaptation over biogeographic scales.

Short Communication

Plant stoichiometry in relation to relative growth rate
Göran I Ågren
2024, 17 (6): rtae095.
doi:10.1093/jpe/rtae095
Abstract ( 31 )   PDF（pc） (790KB) ( 14 )   Save
Plants need certain proportions between elements for proper growth and functioning. These proportions vary with growth conditions and it has generally been found that with increasing relative growth rates P:N should increase (the growth rate hypothesis). However, the proportions between N and other elements change with growth rates, and how this determines which element is limiting growth is not well studied, but it is possible that limitations of other elements could restrain plant growth more than N. Using results from nine studies with birch plants (Betula pendula) with different limiting elements (N, P, K, S, Mg, Zn, Mn, Fe and Cu) under steady-state growth, I have investigated how the switch, defined as the ideal proportion, between which element is limiting growth varies with relative growth rate. The ideal proportion of element:N increases with increasing relative growth rate for K, P, Zn and Mn but a slight decline for Mg and S. The changes in element:N ratios are strongest at low relative growth rates. The consequences of these results for plant properties under global change are discussed.