Current Issue
  • Volume 12 Issue 4
    The picture displays subtropical forests with high beta diversity in Qianjiangyuan National Park. Photo taken by Yunquan Wang and Xiaoxia Yi. See Cao et al. in this issue.
      
    Research Articles
    Shuai Fang, Marc William Cadotte, Zuoqiang Yuan, Fei Lin, Ji Ye, Zhanqing Hao and Xugao Wang
    2019, 12 (4): 593-602.
    Abstract ( 87 )   PDF   Save
    Aims

    Intraspecific trait variation (ITV) has been increasingly recognized to play an important role in understanding the underlying processes influencing community assembly. However, gaps remain in our understanding of how incorporating ITV will influence the relative importance of deterministic (e.g. habitat filtering, limiting similarity) and stochastic processes in driving community assembly at different successional stages.

    Methods

    We used data for eight functional traits from 55 woody species in early (24 ha) and late (25 ha) successional temperate forest plot in northeast China. We employed an approximate Bayesian computation approach to assess the relative contribution of stochastic processes, habitat filtering and limiting similarity in driving community structure. We then compared the results with and without intraspecific trait variation to investigate how ITV influences the inferred importance of each process.

    Important Findings

    We found that when analyzing interspecific trait variation only (i.e. without ITV), stochastic processes were observed most frequently in driving community composition, followed by habitat filtering and limiting similarity in both forests. However, ITV analyses showed that the relative importance of both deterministic processes (habitat filtering and limiting similarity) increased in early successional forest, but remained virtually unchanged in late successional forest. Our study reveals the distinctive influence of ITV on the inference of underlying processes in a context of succession and reinforces the need to estimate ITV for making correct inferences about underlying ecological processes.


    Robert L. Fitch, Erin J. Questad and Edward G. Bobich
    2019, 12 (4): 603-614.
    Abstract ( 51 )   PDF   Save
    Aims

    The objectives of this study were to (i) determine the importance of soil moisture and soil nitrogen availability as resource requirements for the establishment of Stipa pulchra, (ii) to examine how changes in slope within a local habitat can affect the accumulation of soil moisture and soil nitrogen and (iii) to measure the physiological responses of S. pulchra among such slope locations.

    Methods

    The field experiment occurred in the San José Hills of Southern California on the California State Polytechnic University, Pomona campus. Plots were established within three different slope locations (shallow, moderate and steep) within four separate canyons. Three nitrogen treatments (ambient, addition and removal) were replicated within each slope location for all four canyons, and five S. pulchra plants were planted in each plot. Soil nitrogen accumulation and soil moisture, as well as other abiotic variables, were measured across the varied slope locations and nitrogen treatments. We measured the cover, stress, and reproduction of S. pulchra plants for 2 years and used a mesocosm experiment to determine how S. pulchra responds to varying water and nitrogen availability.

    Important Findings

    Stipa pulchra had a strong positive response to the wettest watering treatment and a weak response to nitrogen addition in the mesocosm experiment. In the field experiment, S. pulchra responded positively in moderate slope locations and did not respond to nitrogen treatments, possibly due to drought. Field patterns of soil moisture were driven by slope, soil compaction and solar radiation. Soil nitrogen accumulation did not vary among slope locations. For restoration of S. pulchra, priority should be placed on managing soil moisture availability and determining suitable edaphic factors.

    Tao Yan, Jiaojun Zhu, Huanhuan Song and Kai Yang
    2019, 12 (4): 615-623.
    Abstract ( 63 )   PDF   Save
    Aims

    Larch is the dominant timber species in Northeast China. However, compared with the adjacent secondary forests, soil available nitrogen (N) significantly declined in ~40-year-old larch plantations. Thus, it is of great importance to determine how N use strategies in larch change in response to declining soil N availability.

    Methods

    We investigated the changes in N concentration and 15N natural abundance (δ15N) from 18 August to 25 October in the leaves, stems, branches and roots of 1-year-old Larix kaempferi seedlings under nutrient-sufficient (NSu) and nutrient-starvation (NSt) conditions with a pot experiment in Northeast China.

    Important Findings

    Stem and branch N concentrations exhibited upward trends, and leaf N concentration exhibited a downward trend. Root N concentration exhibited an upward trend under NSu conditions, but a downward trend under NSt conditions. These results suggested that stems and branches were served as N storage organs, but roots shifted from storage to resorption organs when switched from NSu to NSt. Leaf nutrient resorption was intensely occurred on 11 October, as indicated by the sharply decreased leaf N concentration and increased stem, root and branch N concentrations. The δ15N of roots, branches and leaves overlapped between NSu and NSt approximately on 11 October, which may be regulated by isotope discrimination during N resorption. Leaf N resorption efficiency under NSt (76.33%) was significantly higher than that of NSu (56.76%), indicating that nutrient stress stimulates leaf N resorption. Taken together, larch seedlings enhance leaf nutrient resorption and shift roots from nutrient storage to nutrient resorption to adapt to NSt conditions. These changes might relieve the adverse effects of declining soil nutrient availability on seedling survival and regeneration.

    Bi-Cheng Dong, Li-Min Zhang, Kai-Yu Li, Xiao-Ting Hu, Pu Wang, Yong-Jian Wang, Fang-Li Luo, Hong-Li Li and Fei-Hai Yu
    2019, 12 (4): 624-635.
    Abstract ( 59 )   PDF   Save
    Aims

    Clonal integration, i.e. resource sharing between interconnected ramets, can help clonal plants tolerate abiotic stress. However, few studies have directly examined the ecological significance of clonal integration in the ability of clonal plants to tolerate biotic stress such as herbivory.

    Methods

    We grew clonal fragments of an invasive clonal plant Alternanthera philoxeroides, each consisting of an apical part (relatively young) and a basal part (relatively old), at two levels (low and high) of soil nitrogen (N). For each fragment, the apical part was subjected to either no herbivory or herbivory for 2 weeks by a specialist insect, Agasicles hygrophila, and was either connected with or disconnected from the basal part not subjected to herbivory.

    Important Findings

    Herbivory in the apical part severely reduced leaf growth (leaf mass, leaf number or leaf area) and ramet production of both apical and basal parts, and increased root to shoot ratio of the apical part. Irrespective of herbivory and soil N, stem connection between the apical and the basal part decreased root to shoot ratio of the apical part, but did not change its growth measures. Meanwhile, connection increased stem N concentration of the apical part growing under high-N supply and decreased stem carbon (C) concentration of the apical part under low-N supply. By contrast, connection increased root to shoot ratio of the basal part, but reduced its leaf and ramet production. Connection also increased leaf and stem C concentrations of the basal part under low-N supply. Thus, clonal integration can be beneficial for the early development of young A. philoxeroides ramets, but not for their local adaptation to herbivory damage by A. hygrophila.

    Ke Cao, Xiangcheng Mi, Liwen Zhang, Haibao Ren, Mingjian Yu, Jianhua Chen, Jintun Zhang and Keping Ma
    2019, 12 (4): 636-644.
    Abstract ( 79 )   PDF   Save
    Aims

    The relative roles of ecological processes in structuring beta diversity are usually quantified by variation partitioning of beta diversity with respect to environmental and spatial variables or gamma diversity. However, if important environmental or spatial factors are omitted, or a scale mismatch occurs in the analysis, unaccounted spatial correlation will appear in the residual errors and lead to residual spatial correlation and problematic inferences.

    Methods

    Multi-scale ordination (MSO) partitions the canonical ordination results by distance into a set of empirical variograms which characterize the spatial structures of explanatory, conditional and residual variance against distance. Then these variance components can be used to diagnose residual spatial correlation by checking assumptions related to geostatistics or regression analysis. In this paper, we first illustrate the performance of MSO using a simulated data set with known properties, thus making statistical issues explicit. We then test for significant residual spatial correlation in beta diversity analyses of the Gutianshan (GTS) 24-ha subtropical forest plot in eastern China.

    Important Findings

    Even though we used up to 24 topographic and edaphic variables mapped at high resolution and spatial variables representing spatial structures at all scales, we still found significant residual spatial correlation at the 10 m × 10 m quadrat scale. This invalidated the analysis and inferences at this scale. We also show that MSO provides a complementary tool to test for significant residual spatial correlation in beta diversity analyses. Our results provided a strong argument supporting the need to test for significant residual spatial correlation before interpreting the results of beta diversity analyses.

    Jian Li, Nan Cong, Jiaxing Zu, Yuqin Xin, Ke Huang, Quan Zhou, Yaojie Liu, Lin Zhou, Li Wang, Yang Liu and Ge Zhang
    2019, 12 (4): 645-652.
    Abstract ( 55 )   PDF   Save
    Aims

    Vegetation dynamics are simultaneously regulated by climate change and anthropogenic activities. Since the 1980s, climate has been warming on the Tibetan Plateau (TP) at a rate higher than North Hemisphere average. Anthropogenic activities, including grazing, farming, and urbanization, are also influencing the alpine ecosystem on the TP. Especially, an ensemble of large engineering projects, such as power transported from west to east by State Grid, has been in operation on the TP. While studies disentangling effects of climate and anthropogenic activities interference are still lacking for the forest ecosystems on the TP. The overarching objectives of this study were to separate effects of natural climates and human interferences on forest ecosystem dynamics on the TP.

    Methods

    We compared vegetation activities of two typical natural reserves (Gongbu natural reserve, GNR, and Yarlung zangbo river grand canyon natural reserve, YNR) and their surroundings in southeastern Tibet (outside of the natural reserves, ONR) using long-term satellite normalized difference vegetation index (NDVI) dataset. Linear regression and partial correlation analyses were constructed for the relationship between vegetation activity and climates to evaluate the distinct climate effects on the two natural reserves.

    Important Findings

    The two natural reserves were established at different time, which were related to anthropogenic activities impact durations. The results showed that the annual mean NDVI fluctuated between 0.5 and 0.6 in the relatively longer reserved YNR, which was remarkably higher than those in other regions (with NDVI lower than 0.45). The vegetation vigor in the YNR showed neither a significant temporal trend nor significant relationship with climate. Nevertheless, vegetation vigor exhibited a significant increasing trend during the last three decades (0.012/decade) at the GNR. The inter-decadal analysis turned out positive relationships between vegetation vigor and annual temperature since late 1990s until early 2000s when the GNR was officially established. This study underlined the importance of considering human interference duration when assessing the relationships between vegetation dynamics and climates.

    Joshua S. Lynn and Jason D. Fridley
    2019, 12 (4): 653-661.
    Abstract ( 61 )   PDF   Save
    Aims

    Geographic patterns of the intensity of plant herbivory in relation to climate factors have garnered little general support and appear to be species specific. However, plant–herbivore interactions are also driven by resource availability, such as soil nutrient content, and it remains unclear whether broad-scale variation in soil factors is reflected in herbivore consumption rates across species’ ranges. Additionally, we know little of how intraspecific variation in tissue quality associates with edaphic and climatic factors, and how this variation controls herbivore consumption. The resource availability hypothesis (RAH) predicts that plant individuals growing in low-resource environments will have lower leaf nutritional quality and more constitutive defenses, which will result in lower rates of leaf consumption.

    Methods

    We collected leaves from the old-field dominant species, Solidago altissima L., from 20 sites across 10 degrees of latitude in the Eastern USA to determine the percentage leaf area consumed by insect folivores. We obtained soil and climate data for each site, as well as plant functional and defensive traits, including specific leaf area (SLA), leaf carbon:nitrogen (C:N), and trichome density.

    Important Findings

    Although we found no significant latitudinal trend of leaf consumption rate, there was strong evidence that leaf herbivory decreased with leaf C:N and trichome density, which themselves decreased with soil N, supporting our hypothesis that the RAH applies for intraspecific variation across spatial gradients. Additionally, high precipitation seasonality and soil nitrogen predicted decreased herbivory. The results suggest that spatial variation in herbivory can be driven by factors other than herbivore communities and climatic gradients, and that bottom-up processes, where plant traits and soil fertility control leaf consumption, must be incorporated into spatial predictions of herbivory.

    Rubén Portela, Bi-Cheng Dong, Fei-Hai Yu, Rodolfo Barreiro and Sergio R. Roiloa
    2019, 12 (4): 662-672.
    Abstract ( 51 )   PDF   Save
    Aims

    The plant–herbivore interaction is one of the most fundamental interactions in nature. Plants are sessile organisms, and consequently rely on particular strategies to avoid or reduce the negative impact of herbivory. Here, we aimed to determine the defense strategies against insect herbivores in the creeping invasive plant Alternanthera philoxeroides.

    Methods

    We tested the defense response of A. philoxeroides to herbivory by a leaf-feeding specialist insect Agasicles hygrophila and a polyphagous sap-feeding insect Planococcus minor. We also tested the mechanisms triggering defense responses of A. philoxeroides by including treatments of artificial leaf removal and jasmonic acid application. Furthermore, we examined the effect of physiological integration on these defense strategies.

    Important Findings

    The combination of artificial leaf removal and jasmonic acid application produced a similar effect to that of leaf-feeding by the real herbivore. Physiological integration influenced the defense strategies of A. philoxeroides against herbivores, and increased biomass allocation to aboveground parts in its apical ramets damaged by real herbivores. Our study highlights the importance of physiological integration and modular plasticity for understanding the consequences of herbivory in clonal plants.

    Chika Egawa, Takeshi Osawa, Tomoko Nishida and Yasuto Furukawa
    2019, 12 (4): 673-681.
    Abstract ( 35 )   PDF   Save
    Aims

    The invasion success of alien plants is strongly affected by both biological and human-associated factors. Evaluation of the relative contribution of each factor is important not only for the further understanding of invasion processes but also for the better management of invasion risk, particularly in protected areas of high conservation priority. Here, we quantified the relative importance of species biological traits and association with a human activity, i.e. agriculture, in explaining the invasion success of alien plants across the entire region and in protected areas in Hokkaido, Japan.

    Methods

    As a quantitative measure of invasion success, the distribution extent of naturalized populations across the entire prefecture and in protected areas was calculated for 63 alien species with equal residence time based on species occurrence records at a spatial resolution of 5-km mesh grid units. For each species, we identified seven biological traits (seed mass, dispersal mode, maximum plant height, capability of vegetative reproduction, flowering start time and period and life span) and two human-associated factors (introduction purpose and cultivation frequency for agricultural use). Cultivation frequency was determined based on the frequency of seed-sowing in pastures: (1) not sown, (2) accidentally sown as a seed contaminant and (3) intentionally sown for commercial cultivation. The importance of biological traits and human-associated factors in explaining the distribution extent was determined using an information-theoretic approach.

    Important Findings

    In explaining the distribution extent across the entire prefecture, species biological traits and human-associated factors showed comparable importance; cultivation frequency exhibited the highest importance value closely followed by seed mass, maximum height and flowering period. In contrast, when focusing on protected areas, human association was more important than biological traits, as indicated by the greatest importance of cultivation frequency and much lower values for most biological traits. The results demonstrated that species biological traits and human association almost equally contributed to invasion success across the entire region, while invasions into protected areas were more attributable to human association than to biological traits. We highlight that the control of propagule pressure associated with artificial cultivation may be key to preventing further invasions into protected areas.

    Fan Ding, Shuangyi Li, Xiao-Tao Lü, Feike A. Dijkstra, Sean Schaeffer, Tingting An, Jiubo Pei, Liangjie Sun and Jingkuan Wang
    2019, 12 (4): 682-692.
    Abstract ( 71 )   PDF   Save
    Aims

    Crop nitrogen (N) and phosphorus (P) stoichiometry can influence food nutritive quality and many ecosystem processes. However, how and why N and P stoichiometry respond to long-term agricultural management practices (e.g. N fertilization and film mulching) are not clearly understood.

    Methods

    We collected maize tissues (leaf, stem, root and seed) and soil samples from a temperate cropland under 30-year continuous N fertilization and plastic film mulching treatments, measured their C, N and P concentrations (the proportion (%) relative to the sample mass), and used structural equation models to uncover the responding mechanisms for crop N and P contents (the total amount (g/m2) in crop biomass).

    Important Findings

    Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tissues (leaf, stem and root), thereby reducing their C/N ratio and increasing C/P and N/P ratios. The drop in P concentration in vegetative tissues was due to the dilution effect by biomass increment and the priority of P supply for seed production. In contrast, film mulching decreased N concentration but increased P concentrations in most crop tissues, thereby increasing C/N ratio and reducing C/P and N/P ratios. Film mulching increased crop P content by increasing soil temperature and moisture; whereas, mulching showed little effect on crop N content, because a positive effects of soil temperature may have canceled out a negative effect by soil moisture. This indicated a decoupling of P and N uptake by crops under film mulching. In conclusion, N fertilization and plastic film mulching showed opposite effects of on crop N and P stoichiometry.

    Fei Chen, Xiang Liu and Shurong Zhou
    2019, 12 (4): 693-702.
    Abstract ( 51 )   Save
    Aims

    Nitrogen enrichment may affect ‘community invertebrate herbivory’ (hereafter ‘herbivory’) directly by changing plant species’ specific herbivory, or indirectly by altering the composition of natural plant communities. Here, we investigated how community composition altered the community herbivory in natural ecosystems and compared the relative importance of direct and indirect effects of nitrogen addition on community herbivory.

    Methods

    We conducted a 7-year nitrogen addition experiment in an alpine meadow to evaluate the effects of fertilization on both herbivory frequency and severity, and we divided plants into four functional groups to investigate how changes in plant community functional composition affect community herbivory frequency. To separate the relative importance of direct and indirect effects of fertilization on community herbivory frequency, we build a serious of generalized models to select variables and used SEM methods to estimate relative contributions of the direct and indirect effects.

    Important findings

    We found that nitrogen addition increased community herbivory frequency, but not community herbivory severity in our 7-year nitrogen addition experiment. Although the most parsimonious model for explaining the variation in community herbivory frequency included fixed average of herbivory frequency and nitrogen addition, community fixed average of herbivory was the best single predictor for community herbivory frequency in our study. Changes in fixed average of herbivory frequency mediated by plant community composition (indirect effect) outperformed changes in species-specific herbivory frequency (direct effect) under fertilization in driving community herbivory frequency. Our research suggested that indirect effects caused by changes in plant community composition played a more important role in invertebrate herbivory under the condition of anthropogenic nitrogen enrichment.

    José Luiz Alves Silva, Alexandre Fadigas Souza and Louis Stephen Santiago
    2019, 12 (4): 703-712.
    Abstract ( 40 )   PDF   Save
    Aims

    Trait-based approaches are increasingly being used in ecology due to their potential to explain and predict community structure and dynamic regardless of species identities. Here, we asked whether coastal heath vegetation established in stressful habitats could be assembled by quasi-neutral mechanisms based on functional trait distribution. Communities are organized through quasi-neutral dynamics if abiotic gradients and/or species interactions impose sorting on functional traits and species performances, but not on species phylogenetic relatedness and occurrence.

    Methods

    The study was conducted in a coastal area containing tall dunes near the sea, and relatively flat areas punctuated by short palaeodunes further inland, Northeastern South America. We evaluated 10 traits of the 21 most abundant species, as well as eight abiotic variables in 70 plots (25?m2) established in dune tops, valleys, flat and steep microenvironments. The effect of environmental filter was tested by linear mixed models (LMM) between each community-weighted mean (CWM) trait and the abiotic variables, and by two indices of environmental filtering based on intra- and interspecific-trait variability relative to null models. To evaluate the effect of species interactions, we used an index of niche overlap relative to null models, and LMMs between this index and the species richness of plots.

    Important Findings

    The environmental filtering index did not deviate from null expectations for any trait. Models that included individual variability performed similarly to models that used species mean traits. However, the explicit consideration of environmental gradients by CWM analyses revealed functional patterns that would remain undetected if trait distribution was analyzed only. In addition, intraspecific variation in the stem length was an important driver of species diversity as suggested by the relationship between species richness and the niche overlap index. Based on the occurrence and phylogenetic relatedness of species, previous work in the same system found neutral community assembly. We concluded that to ignore functional traits may lead to underestimations of niche-based processes, and that analyses of species occurrence and phylogenetic relatedness should be complemented with functional traits to reinforce our interpretation of processes underpinning community assembly. In this regard, the study heath vegetation is influenced by quasi-neutral effects on functional trait distribution.

    Wagner A. Chiba de Castro, Rafael O. Xavier, Federico H. L. Garrido, Jair H. C. Romero, Cleto K. Peres and Ruberval C. da Luz
    2019, 12 (4): 713-721.
    Abstract ( 60 )   PDF   Save
    Aims

    Invasive plants modify the structure and functioning of natural environments and threat native plant communities. Invasive species are often favored by human interference such as the creation of artificial forest edges. Field removal experiments may clarify if invasive plants are detrimental to native plant regeneration and how this is related to other local factors. We assessed the joint effect of environment and competition with the invasive Tradescantia zebrina on tree species recruitment in an Atlantic Forest fragment.

    Methods

    We carried out the experimental study in the Igua?u National Park, located in southern Brazil, using 30 plots distributed across five invaded sites during 6 months. We counted T. zebrina leaves and recorded the abundance and height of tree recruits over time under contrasting environmental (forest edge vs. forest interior) and removal (all aboveground biomass, only T. zebrina removal, and control) treatments. We analyzed the effects of environment and removal treatment using generalized linear mixed models.

    Important Findings

    The invasive species performed better at the forest edge than in the interior. The higher competitive pressure of T. zebrina led to higher mortality and lower height of tree recruits. Invader removal favored tree recruitment, especially in the forest interior. Our study shows that T. zebrina hampers woody species regeneration in tropical Atlantic Forests, especially at the forest edge.

    Xiaoshuai Wang, Frank Yonghong Li, Yuanheng Li, Xin Song, Xudong Guo, Xiangyang Hou and Taogetao Baoyin
    2019, 12 (4): 722-729.
    Abstract ( 52 )   PDF   Save
    Aims

    The divergent changes of plant species under land use changes are key mechanisms underlying vegetation succession. Stipa grandis steppe and Stipa krylovii steppe are two plant communities widely distributed on the Mongolian Plateau. They have been speculated to be able to succeed into each other under different land use types and intensities based on the observations on their presence and abundance at the sites with different land use history. However, no direct evidence, neither the underlying mechanisms, have been reported for this speculation. Here, we verified this speculation and explored the underlying mechanisms in the typical steppe region of Inner Mongolia.

    Methods

    We investigated the abundance and reproductive behavior of S. krylovii and S. grandis under different land use types and intensities. We used 18 grassland paddocks to run a 6-year experiment with 6 management treatments (T0—unused, T1—grazing monthly in plant growing season, T2, T4, T6—grazing in different months in plant growing season, and T8—mowing) replicated three times. We measured the relative density and cover of S. krylovii and S. grandis using line sampling method and examined their number and biomass of vegetative and reproductive tillers using quadrat method in each paddock after treatments for 4 and 6 years. We also determined these plant attributes in 14 pairs of heavily versus lightly used grassland plots in a wide area (150 km × 200 km) of the typical steppe region.

    Important Findings

    1. Grazing largely and mowing moderately decreased the density ratio and coverage ratio of S. grandis to S. krylovii in grasslands (P < 0.05), and the differences in these ratios between grazed and unused grasslands increased with time.

    2. Grazing, but not mowing, significantly enhanced the relative density (Nrep = reproductive tiller number/total tiller number) of, and biomass allocation (Brep = reproductive tiller biomass/total biomass) to, reproductive tillers of S. krylovii (P < 0.05), but not S. grandis. This grazing enhancement to sexual reproduction of S. krylovii, and additionally inhibition to Nrep of S. grandis (P < 0.05), were found across the 14 pairs of heavily versus lightly used plots.

    3. Seasonal pattern of grazing affected sexual reproduction of S. krylovii. The Nrep and Brep was higher under grazing in July and September (T4) than in July and August (T6) or in May and July (T2) (P < 0.05), suggesting a relatively positive effect of grazing on sexual reproduction in July (tasseling phenophase) than in May or August.

    Our results provide direct evidence to the reciprocal change of S. grandis and S. krylovii in steppe communities under different management and indicate that gazing or mowing enhancement of sexual reproduction of S. krylovii relative to S. grandis is one of the mechanisms for the change.

    Maria Šurinová, Věroslava Hadincová, Vigdis Vandvik and Zuzana Münzbergová
    2019, 12 (4): 730-741.
    Abstract ( 49 )   PDF   Save
    Aims

    Knowledge of genetic structure of natural populations and its determinants may provide key insights into the ability of species to adapt to novel environments. In many genetic studies, the effects of climate could not be disentangled from the effects of geographic proximity. We aimed to understand the effects of temperature and moisture on genetic diversity of populations and separate these effects from the effects of geographic distance. We also wanted to explore the patterns of distribution of genetic diversity in the system and assess the degree of clonality within the populations. We also checked for possible genome size variation in the system.

    Methods

    We studied genetic variation within and among 12 populations of the dominant grass Festuca rubra distributed across a unique regional-scale climatic grid in western Norway, Europe and explored the importance of temperature, precipitation and geographic distance for the observed patterns. We also explored the distribution of genetic diversity within and among populations, identified population differentiation and estimated degree of clonality. The analyses used microsatellites as the genetic marker. The analyses were supplemented by flow cytometry of all the material.

    Important Findings

    All the material corresponds to hexaploid cytotype, indicating that ploidy variation does not play any role in the system. The results indicate that temperature and precipitation were better predictors of genetic relatedness of the populations than geographic distance, suggesting that temperature and precipitation may be important determinants of population differentiation. In addition, precipitation, alone and in interaction with temperature, strongly affected population genotypic diversity suggesting increased clonality towards the coldest and especially the coldest wettest climates. At the same time, individuals from the coldest and wettest climates also had the highest individual genetic diversity, suggesting that only the most heterozygous individuals survive under these harsh climates. Most of the genetic variation was distributed within populations, suggesting that most populations have sufficient genetic diversity to adapt to novel climatic conditions. The alpine populations, i.e. populations which are likely the most endangered by climate change, however, lack this potential due to the high levels of clonality as detected in our study.

    Yang Li, Longyu Hou, Bing Song, Shiqiang Wan, Xiaoqin Sun and Linghao Li
    2019, 12 (4): 742-750.
    Abstract ( 42 )   PDF   Save
    Aims

    Precipitation is predicted to increase in arid and semiarid regions under climate change, with greater changes in intra- and inter-annual distribution in the future. As a major limiting factor in these regions, changes in precipitation undoubtedly influence plant growth and productivity. However, how the temporal shifts in precipitation will impact plant populations are uncertain.

    Methods

    A 3-year field experiment and a greenhouse experiment were conducted in a temperate grassland in northern China to examine the impacts of seasonal (spring and summer) increased precipitation on offspring performance of a common species, Potentilla tanacetifolia.

    Important Findings

    Our results showed that the amounts and timing of increased precipitation both played important roles in regulating offspring performance of P. tanacetifolia in the temperate steppe ecosystem. Increased precipitation in spring at maternal stage stimulated seed production, germination percentage and seedling biomass, whereas increased precipitation in summer at maternal stage stimulated seedling biomass. The timing of increased precipitation influenced seed attributes, whereas the amount of increased precipitation influenced offspring seedling biomass. Our results indicate that population development of P. tanacetifolia may be underestimated under future increased precipitation regime, if the transgenerational effect is not taken into account.

    Ming Wang, Chuanhua Wang, Lin Yang and Hua Guo
    2019, 12 (4): 751-758.
    Abstract ( 56 )   PDF   Save
    Aims

    To better understand whether and how nitrogen addition impacts the epiphytic lichens in the Shennongjia Nature Reserve (China).

    Methods

    Five dominant epiphytic lichen species, including Usnea longissimaU. luridorufaRamalina calicaris var. japonicaU. dasopoga and U. betulina, were selected as materials, and then field and laboratory nitrogen addition experiments were performed. The phosphomonoesterase (PME) activity and nitrogen (N) and phosphorus (P) content of these lichens were measured, and then the effects of nitrogen addition on thallus nutrient balance and PME activity were discussed.

    Important Findings

    Our results showed that with an increased N deposition from 0.6 to 50 kg N ha?1 a?1, the thallus N content of the five lichen species increased significantly, suggesting that those lichens had strong ability to take up and accumulate N, and an universality of N intolerance in epiphytic lichens. Meanwhile, the P content of five lichens increased slower than N content among N treatments, indicating the supply of P was deteriorated when the supply of N increased. The N addition also led to the N:P ratios of five lichens increased from about 10 to 20, and reached a maximum at 50 kg N ha?1 a?1, and the PME activity of the five lichen species was upregulated by the N addition, indicated that the balance between N and P was deteriorated in these lichens. We concluded that increases in N deposition will lead to nutrient imbalance in lichens and that nitrogen enrichment will change these five lichen species from being N limited to being P limited. Our research will be of value in the conservation of lichen diversity in the Shennongjia Nature Reserve (China).

    Mengjun Hu and Shiqiang Wan
    2019, 12 (4): 759-768.
    Abstract ( 57 )   PDF   Save
    Aims

    Fire and atmospheric nitrogen (N) deposition have the potential to influence growth and productivity of forest canopy. However, their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored. This study was conducted to examine the effects of burning and N addition on foliar N content, net photosynthesis and growth traits of three dominant shrub species (Vitex negundoLindera glauca and Symplocos chinensis) in a temperate forest in Central China.

    Methods

    The experiment used a pair-nested design, with four treatments (control, burning, N addition and burning plus N addition) and five replicates. Leaf mass area (LMA), area-based concentrations of foliar N and chlorophyll (Narea and Chlarea), net photosynthesis (An), stomatal conductance (gs), maximum photosynthetic rate (Amax) and maximal carboxylation rate (Vcmax), basal diameter, height and branch length (BL) of the three species were measured.

    Important Findings

    Across the three species, burning stimulated LMA, Narea, ChlareaAngsAmax and Vcmax, and consequently enhanced basal diameter, height and BL. Nitrogen addition increased An and gs but did not affect LMA, Narea, ChlareaAmaxVcmax, basal diameter, height or BL. However, N addition strengthened the positive effects of burning on gsVcmaxAn and BL. The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

    Jing Wang, Qingsong Yang, Yang Qiao, Deli Zhai, Lifen Jiang, Guopeng Liang, Xiaoying Sun, Ning Wei, Xihua Wang and Jianyang Xia
    2019, 12 (4): 769-780.
    Abstract ( 61 )   PDF   Save
    Aims

    Dead plant material (i.e. litter) is the major source of soil organic matter and thus plays a fundamental role in regulating soil carbon cycling in global forest ecosystems. The storage of litter is jointly determined by its production from plants and decomposition in a given environment. However, only few studies have explored the relative importance of environmental (i.e. abiotic) and plant (i.e. biotic) factors in driving the spatial variation of litter mass. The objective of this study is to quantify the relative contributions of biotic and abiotic factors in affecting the spatial variation of aboveground litter stock in a mature subtropical forest.

    Methods

    The aboveground litter mass was sampled in 187 grids of a 20-hm forest dynamics plot in a subtropical broad-leave forest in eastern China. The contributions of environmental variables, topographical and species variables on litter stocks were quantified by the boosted regression tree analysis.

    Important Findings

    The mean aboveground litter stock was 367.5 g m?2 in the Tiantong dynamics forest plot across all the 187 grids. The litter stock ranged from 109.2 to 831.3 g m?2 and showed a large spatial variation with the coefficient of variance as 40.8%. The boosted regression tree analysis showed that slope elevation and soil moisture were the most influential variables on the spatial variation of litter stock. The relatively influence of abiotic factors (environmental and topographical factors) was 71.4%, which is larger than biotic factors (28.6%). Overall, these findings suggest that abiotic factors play a more important role than plants in driving the spatial variation of aboveground litter stock in the subtropical forest. Given that the global carbon-cycle models have been aiming to refine from the hundred kilometers to sub-kilometer scale, this study highlights the urgency of a better understanding of the spatial variation of litter stock on the fine scale.

    Short Communication
    Zhe Wang, Chunyan Pi, Xiaoming Li and Weikai Bao
    2019, 12 (4): 781-786.
    Abstract ( 38 )   PDF   Save
    Aims

    The nutrient uptake, requirement and releasing rates of bryophytes are very different from those of tracheophytes. However, it is difficult to make a quantitative evaluation of bryophytes’ roles in nutrient cycling and their specific eco-physiological adaptations due to lack of knowledge of their concentrations and stoichiometric ratios of carbon (C), nitrogen (N) and phosphorus (P). To fill this gap, the present study aims to investigate: (i) what are the elevational trends of C, N and P concentrations and stoichiometric ratios of bryophytes? (ii) whether C, N and P concentrations and stoichiometric ratios of bryophytes differ between different bryophyte types (in terms of the growth form and living substrate)? and (iii) how do the exponent scalings of N and P of bryophytes change along the elevational gradient?

    Methods

    We measured and calculated the C, N, P concentrations and stoichiometric ratios of bryophytes from four elevations on the eastern slope of Gongga Mountain (22 species in total). Differences in these traits among elevations, and between different bryophyte types were compared. The log-log allometric regression parameters of N and P at each elevation were also determined and compared.

    Important Findings

    The C, N and P concentrations of bryophytes showed decreasing trends with increasing elevations. More specifically, erect bryophytes possessed higher C and N concentrations than those of prostrate species, and terricolous species had higher P concentration than that of corticolous and saxicolous species. Bryophytes from different elevations had an invariant allometric regression slope for P versus N. Future research at a larger scale is in need for a more generalized law of bryophytes.

    Corrigendum
    Kuber Prasad Bhatta, Harry John Betteley Birks, John-Arvid Grytnes and Ole Reidar Vetaas
    2019, 12 (4): 787-789.
    Abstract ( 59 )   PDF   Save
Impact Factor
1.833
5 year Impact Factor
2.299
Editors-in-Chief
Wen-Hao Zhang
Bernhard Schmid