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  • Volume 8 Issue 5
    Norway spruce (Picea abies) successfully invading montane grasslands in the western Carpathians (Pol'ana Biosphere Reserve) by frontier expansion and by advanced individuals and small groups. Photos taken by Karol Ujházy.
    Research Articles
    Rafael Jaime, Julio M. Alcántara, Jesús M. Bastida, Pedro J. Rey
    2015, 8 (5): 457-467.
    Abstract ( 44 )   PDF   Save
    Aims This study explores the patterns of niche differentiation in a group of seven closely related columbines (genus Aquilegia, Ranunculaceae) from the Iberian Peninsula. Populations of these columbines are subject to complex patterns of divergent selection across environments, which partly explain the taxonomic structure of the group. This suggests the hypothesis that niche divergence must have occurred along the process of diversification of the group.
    Methods We used MaxEnt to build environmental niche models of seven subspecies belonging to the three species of Aquilegia present in the Iberian Peninsula. From these models, we compared the environmental niches through two different approaches: ENMtools and multivariate methods.
    Important findings MaxEnt distributions conformed closely to the actual distribution of the study taxa. ENMtools methods failed to uncover any clear patterns of niche differentiation or conservatism in Iberian columbines. Multivariate analyses indicate the existence of differentiation along altitudinal gradients and along a gradient of climatic conditions determined by the summer precipitation and temperatures. However, climatic conditions related to winter temperature and precipitation, as well as soil properties, were equally likely to show conservatism or divergence. The complex patterns of niche evolution we found suggest that Iberian Columbines have not been significantly constrained by forces of niche conservatism, so they could respond adaptively to the fast and profound climate changes in the Iberian Peninsula through the glacial cycles of the Pleistocene.
    Martin Dovčiak, Richard Hrivnák, Karol Ujházy, Dušan Gömöry
    2015, 8 (5): 468-479.
    Abstract ( 40 )   PDF   Save
    Aims Woody invasions into grasslands have increased globally due to changing land use, climate and introduced woody species, but spatial processes generating and sustaining these invasions are not well understood. To gain insight into the patterns of spread of tree populations within grasslands, and to propose a full spatial analytical toolbox for studying native and non-native woody species spread when long-term data are not available, we tested if 50 years of grassland invasion in Western Carpathians by Norway spruce (Picea abies Karst.) proceeded by one of the two traditionally competing hypotheses of species spread: (i) by frontier expansion, or (ii) by advanced groups established ahead of the population frontier. We also tested whether the pattern of invasion changed over time.
    Methods We analyzed the spatial demographic and genetic patterns of a Norway spruce population invading a Western Carpathian grassland using Ripley's L (t) and genetic kinship coefficients (F ij). We mapped and genotyped spruce trees across the invasion front (from the invasion leading edge to fully colonized grassland near the source population) using three demographic classes (adults, juveniles and seedlings) to approximate the temporal aspects of the invasion. We studied how the spatial patterns of invasion by individual demographic classes and their genetic kinship varied among adjacent plots established at different distances from the source population (ranging from 0 to 160 m, in 40-m distance increments).
    Important findings Juveniles were positively genetically related to adults on fine scales (<4 m), suggesting that adults within the grassland acted as a seed source and accelerated early invasion. However, adults did not act as nucleation centers for the formation of advanced juvenile groups. Instead, genetically unrelated juveniles formed groups independently of adults. These groups were small and separate at the leading edge but they increased in size and graded into a continuous zone near the source population. Thus, juvenile recruitment occurred as a frontier expansion near the source population and as advanced groups controlled by environmental variation at the leading edge. Unlike juveniles, seedlings were clustered on all scales across the invasion front and formed groups around adult crowns at the invasion leading edge. The bulk of seedling establishment occurred at intermediate distances from the source population, independently from the adults, suggesting that the invasion front continued to expand as a frontier, gradually coalescing with the advanced groups at the leading edge. Thus, the grassland invasion was driven by a gradual frontier expansion of the original population during the first 50 years, with advanced groups enhancing but not driving the invasion process. Frontier expansion appeared more important as a mechanism of woody species spread early in the invasion process in this study, while advanced groups may play a larger role over longer temporal scales.
    Futao Guo, John L. Innes, Guangyu Wang, Xiangqing Ma, Long Sun, Haiqing Hu, Zhangwen Su
    2015, 8 (5): 480-490.
    Abstract ( 59 )   PDF   Save
    Aims The pattern and driving factors of forest fires are of interest for fire occurrence prediction and forest fire management. The aims of the study were: (i) to describe the history of human-caused fires by season and size of burned area over time; (ii) to identify the spatial patterns of human-caused fires and test for the existence of 'hotspots' to determine their exact locations in the Daxing'an Mountains; (iii) to determine the driving factors that determine the spatial distribution and the possibility of human-caused fire occurrence.
    Methods In this study, K -function and Kernel density estimation were used to analyze the spatial pattern of human-caused fires. The analysis was conducted in S-plus and ArcGIS environments, respectively. The analysis of driving factors was performed in SPSS 19.0 based on a logistic regression model. The variables used to identify factors that influence fire occurrence included vegetation types, meteorological conditions, socioeconomic factors, topography and infrastructure factors, which were extracted and collected through the spatial analysis mode of ArcGIS and from official statistics, respectively.
    Important findings The annual number of human-caused fires and the area burnt have declined since 1987 due to the implementation of a forest fire protection act. There were significant spatial heterogeneity and seasonal variations in the distribution of human-caused fires in the Daxing'an Mountains. The heterogeneity was caused by elevation, distance to the nearest railway, forest type and temperature. A logistic regression model was developed to predict the likelihood of human-caused fire occurrence in the Daxing'an Mountains; its global accuracy attained 64.8%. The model was thus comparable to other relevant studies.
    Shishir Paudel, Loretta L. Battaglia
    2015, 8 (5): 491-500.
    Abstract ( 44 )   PDF   Save
    Aims Understanding relationships between the distributions of species and their surrounding environment provides a basis for forecasting how species will respond to future environmental changes. In this study, we examined the effects of environmental factors and human developmental features associated with disturbances on probability of occurrence of juveniles of invasive Triadica sebifera and three native plant species, Baccharis halimifolia, Ilex vomitoria and Morella cerifera within a typical coastal transition in coastal Mississippi, USA.
    Methods We recorded presence of juveniles of focal species and measured environmental factors (soil salinity, canopy openness, soil texture and soil carbon to nitrogen ratio) along an 11.3 km transect located at Grand Bay National Estuarine Research Reserve. Further, we documented anthropogenic features and associated activities as a proxy for human disturbance.
    Important findings With the exception of I. vomitoria, all other species occurrences were significantly influenced by an interaction between soil salinity and canopy openness. The occurrence of I. vomitoria sharply decreased with salinity. B. halimifolia occurrence peaked at moderate levels of salinity and low to moderate levels of canopy openness. Occurrences of M. cerifera and the invasive T. sebifera were highest at low levels of salinity and canopy openness. These results indicate that salinity is a strong driver that limits distribution of juvenile native and invasive species in coastal transitions. Logistic regression confirmed the positive effects of anthropogenic disturbances on T. sebifera and I. vomitoria occurrence. It appears that while soil salinity is likely to drive retreat of the seaward boundaries of woody plant species distributions, increased human developments along the coast likely enhance the inland spread of species, in particular the invasive T. sebifera by increasing disturbances and facilitating dispersal. Results from this study can offer insight for the development of T. sebifera management and preventive measures for further spread along coastal areas of the southeastern USA.
    Pandi Vivek, Narayanaswamy Parthasarathy
    2015, 8 (5): 501-512.
    Abstract ( 42 )   PDF   Save
    Aim Lianas are abundant and diverse throughout the world and constitute an important structural and functional component of tropical forests. This study aims to investigate liana diversity, abundance and their functional traits in Indian tropical dry evergreen forest (TDEF).
    Methods A total of ten 1-ha plots, one each in 10 Indian TDEF sites were demarcated. Each 1-ha plot was divided into one-hundred 10- × 10-m quadrats to facilitate woody species inventory. All lianas ≥1cm diameter measured at 130cm from the rooting point and all trees ≥10-cm girth at breast height (gbh) were recorded from the study sites to analyze the patterns of liana diversity and abundance and also to compare the contribution of lianas to the total woody species richness, density and basal area. Liana variables across the study sites were compared using one-way analysis of variance. The qualitative functional traits of inventoried lianas and trees were assessed on the field and referring to pertinent field manuals.
    Important findings A total of 9237 liana individuals (ranged from 408–1658 individuals ha-1) representing 52 species, 45 genera and 28 families were encountered from the 10 study sites. Liana species richness ranged from 11–31 species ha-1 in 10 sites, which averaged 23.4 (±5.7) species ha-1. The total basal area of lianas in the study sites was 7. 3 m 2 (0.20–1.76 m 2 ha-1). There was a significant variation in liana species richness, density and basal area across the studied sites. On the whole, lianas contributed 52%, 49.3% and 4.1% to the total woody species (lianas and trees) richness, density and basal area, respectively. Liana trait analysis revealed the majority (50%) of lianas belonged to brevi-deciduous type. Stem twining was the chief climbing mechanism, exhibited by 21 species (52.6% of total abundance). More than half of the liana species (34 species; 6925 individuals) had microphyllous leaves. Fleshy-fruited lianas mostly bearing berries and drupes constituted the major fruit type in the studied sites. Zoochory was the predominant dispersal mode observed in 63.4% of species. Considering the ecological and functional role of lianas in Indian TDEF, the need for conservation is emphasized.
    Wei Li, Jimin Cheng, Kailiang Yu, Howard E. Epstein, Guozhen Du
    2015, 8 (5): 513-522.
    Abstract ( 49 )   PDF   Save
    Aims The relationship between biodiversity and ecosystem functioning has intrigued ecologists for several decades, but the effect of loss of a dominant species on community structure and functioning along a nutrient gradient remains poorly understood. The aim of this paper was to test the effect of a dominant species on community structure and function by conducting a species removal experiment along a fertilization gradient.
    Methods We removed the population of a dominant species (Elymus nutans) in a long-term fertilization field in an alpine meadow on the Tibetan Plateau, China. Univariate general linear models were used to evaluate the effects of fertilization and removal on above-ground vegetation characteristics, including photosynthetically active radiation in the understory, species richness, Shannon–Weiner diversity index, Simpson's dominance index, above-ground biomass (including different functional groups) and seedling richness and density.
    Important findings Results revealed that after two plant growing seasons, there was no significant effect of the removal of a dominant species on species richness and diversity of the remaining vegetation, but the biomass of forbs and seedling recruitment were significantly increased indicative of the potential for long-term effects. Moreover, removal had a large effect at high fertilization levels, but little effect when fertilization levels were low. Our studies indicated that community response to loss of a dominant species was mainly dependent on resource availability and the remaining functional group identities. We also found seedling recruitment was usually more sensitive to the influence of competition of dominant species than the established vegetation in the short term.
    Zhenzhong Sun, Anping Chen, Junhua Ma, Chune He, Zhu Ouyang, Zhenrong Tian
    2015, 8 (5): 523-529.
    Abstract ( 39 )   PDF   Save
    Aims Understanding the effect of long-term fertilization on the sensitivity of grain yield to temperature changes is critical for accurately assessing the impact of global warming on crop production. In this study, we aim to assess the impacts of temperature changes on grain yields of winter wheat (Triticum aestivum L.) under different fertilization treatments in a long-term manipulative experiment in North China.
    Methods We measured grain yields of winter wheat under four fertilization treatments at the Yucheng Comprehensive Experimental Station each year from 1993 to 2012. We also measured air temperature at 0200, 0800, 1400 and 2000h each day since 1 January 1980. We then used the first-difference method and simple linear regression models to examine the relationship of crop yield changes to mean air temperature, mean daytime and nighttime air temperature in crop growing seasons.
    Important findings We found that increases in mean daily temperature, mean daytime temperature and mean nighttime temperature each had a positive impact on the grain yield of winter wheat. Grain yield increased by 16.7–85.6% for winter wheat in response to a 1°C increase in growing season mean daily temperature. Winter wheat yield was more sensitive to variations of nighttime temperature than to that of daytime temperature. The observed temperature impacts also varied across different fertilization treatments. Balanced fertilization significantly enhanced grain yields for winter wheat under a warming climate. Wheat plots treated with nitrogen and phosphorous balanced fertilization (NPK- and NP-treated plots) were more responsive to temperature changes than those without. This report provides direct evidence of how temperature change impacts grain yields under different fertilization treatments, which is useful for crop management in a changing global climate.
    Jianhua Zhang, Zhiyao Tang, Yongkai Luo, Xiulian Chi, Yahan Chen, Jingyun Fang, Haihua Shen
    2015, 8 (5): 530-538.
    Abstract ( 42 )   PDF   Save
    Aims To explore resorption efficiency of nitrogen (NRE) and phosphorus (PRE) of woody plants in relation to soil nutrient availability, climate and evolutionary history, in North China.
    Methods We measured concentrations of nitrogen ([N]) and phosphorus ([P]) in both full expanded mature green and senescent leaves of the same individuals for 88 woody species from 10 sites of Mt. Dongling, Beijing, China. We built a phylogenetic tree for all these species and compared NRE and PRE among life forms (trees, shrubs and woody lianas) and between functional groups (N-fixers and non-N-fixers). We then explored patterns of NRE and PRE along gradients of mean annual temperature (MAT), soil inorganic N and available P, and phylogeny using a general linear model.
    Important findings Mass-based NRE (NRE m) and PRE (PRE m) averaged 57.4 and 61.4%, respectively, with no significant difference among life forms or functional groups. Neither NRE m nor PRE m exhibited significant phylogenetic signals, indicating that NRE m and PRE m were not phylogenetically conserved. NRE m was not related to [N] in green leaves; PRE m was positively correlated with [P] in green leaves; however, this relationship disappeared for different groups. NRE m decreased with [N] in senescent leaves, PRE m decreased with [P] in senescent leaves, for all species combined and for trees and shrubs. NRE m decreased with soil inorganic N for all species and for shrubs; PRE m did not exhibit a significant trend with soil available P for all species or for different plant groups. Neither NRE m nor PRE m was significantly related to MAT for overall species and for species of different groups.
    Meng Gao, Xinxiu Wang, Cang Hui, Huapeng Yi, Chuanqi Zhang, Xiaoqing Wu, Xiaoli Bi, Yong Wang, Luxiang Xiao, De Wang
    2015, 8 (5): 539-548.
    Abstract ( 43 )   PDF   Save
    Aims The mechanisms of plant community assembly are hypothesized to vary at different stages of succession. Here, we explore the local assemblage structure of a herbaceous plant community at its early stage of succession in a supratidal wetland. Specifically, we assess the role of Chinese saltcedar (Tamarix chinensis), the lone dominant shrub species, in shaping the spatial structure and species composition in the local plant community, after landscape alteration.
    Methods We used the multivariate trend-surface analysis for analyzing the spatial structure of the community composition. A null model was also used to detect potential biotic interactions between species. Statistical significance was derived from a permutation test by randomizing the presence-absence matrix and functional traits independently. Sensitivity analysis by randomly selecting 50 subplots and repeating the null model tests was also done. Finally, rank correlation analysis was used to study the relationship between effect sizes and distance to nearest T. chinensis individuals.
    Important findings The herbaceous plant community was highly structured and shaped by the presence of T. chinensis. At local scale, two functional traits, plant height and leaf area, were found to be significantly convergent. Dispersal, environmental stress and interspecific competition played a trivial effect on the local community assembly. The facilitating effect of T. chinensis on the pioneering herbaceous plants, through acting as a wind shelter, was put forward as the dominant community assembly process.
    Debra Zuppinger-Dingley, Dan F. B. Flynn, Helmut Brandl, Bernhard Schmid
    2015, 8 (5): 549-557.
    Abstract ( 37 )   PDF   Save
    Aims In grassland biodiversity experiments, positive biodiversity effects on primary productivity increase over time. Recent research has shown that differential selection in monoculture and mixed-species communities leads to the rapid emergence of monoculture and mixture types, adapted to their own biotic community. We used eight plant species selected for 8 years in such a biodiversity experiment to test if monoculture and mixture types differed in metabolic profiles using infrared spectroscopy.
    Methods Fourier transform infrared spectroscopy (FTIR) was used to assess metabolic fingerprints of leaf samples of 10 individuals of each species from either monocultures or mixtures. The FTIR spectra were analyzed using multivariate procedures to assess (i) whether individuals within species could be correctly assigned to monoculture or mixture history based on the spectra alone and (ii) which parts of the spectra drive the group assignment, i.e. which metabolic groups were subject to differential selection in monocultures vs. mixtures.
    Important findings Plant individuals within each of the eight species could be classified as either from monoculture or mixture selection history based on their FTIR spectra. Different metabolic groups were differentially selected in the different species; some of them may be related to defense of pathogens accumulating more strongly in monocultures than in mixtures. The rapid selection of the monoculture and mixture types within the eight study species could have been due to a sorting-out process based on large initial genetic or epigenetic variation within the species.
Impact Factor
5 year Impact Factor
Wen-Hao Zhang
Bernhard Schmid