The role of plant–soil feedbacks and land-use legacies in restoration of a temperate steppe in northern China

Plant–soil feedbacks affect plant performance and plant community dynamics; however, little is known about their role in ecological restoration. Here, we studied plant–soil feedbacks in restoration of steppe vegetation after agricultural disturbance in northern China. First, we analyzed abiotic and biotic soil properties under mono-dominant plant patches in an old-field restoration site and in a ‘target’ steppe site. Second, we tested plant–soil feedbacks by growing plant species from these two sites on soils from con- and heterospecific origin. Soil properties generally did not differ between the old-field site and steppe site, but there were significant differences among mono-dominant plant patches within the sites. While soil species origin (i.e., the plant species beneath which the soil was collected) affected biomass of individual plant species in the feedback experiment, species-level plant–soil feedbacks were ‘neutral’. Soil site origin (old-field, steppe) significantly affected biomass of old-field and steppe species. For example, old-field species had higher biomass in old-field soils than in steppe soils, indicating a positive land-use legacy. However, soil site origin effects depended on the plant species beneath which the soils were collected. The predictive value of abiotic and biotic soil properties in explaining plant biomass differed between and within groups of old-field and steppe species. We conclude that the occurrence of positive land-use legacies for old-field species may retard successional replacement of old-field species by steppe species. However, high levels of idiosyncrasy in responses of old-field and steppe plant species to con- and heterospecific soils indicate interspecific variation in the extent to which soil legacies and plant–soil feedbacks control successional species replacements in Chinese steppe ecosystems.     

Some progress in the study of plant–soil interactions in China

Plants and soil are the base for sustainably surviving human beings on the globe as the role of materials, energy, resources and environment (Shao & Chu 2008; Shao et al. 2008, 2009, 2010, 2012a,b; Liu & Shao, 2010; Ruan et al. 2010; Xu et al. 2010, 2012; Shao 2012; Huang et al. 2013). This topic has been extensively investigated for 100 years with more achievements in many sectors and practical significance in conducting high-efficient agriculture and eco-environmental construction. The plant–soil interaction is the core issue of this topic, which has been given much attention for the past 30 years (Wu et al. 2007, 2010; Zhang et al. 2011, 2013; Xu et al. 2012, 2013).     

Do forest soil microbes have the potential to resist plant invasion? A case study in Dinghushan Biosphere Reserve (South China)

Successful invaders must overcome biotic resistance, which is defined as the reduction in invasion success caused by the resident community. Soil microbes are an important source of community resistance to plant invasions, and understanding their role in this process requires urgent investigation. Therefore, three forest communities along successional stages and four exotic invasive plant species were selected to test the role of soil microbes of three forest communities in resisting the exotic invasive plant. Our results showed that soil microbes from a monsoon evergreen broadleaf forest (MEBF) (late-successional stage) had the greatest resistance to the invasive plants. Only the invasive species Ipomoea triloba was not sensitive to the three successional forest soils. Mycorrhizal fungi in early successional forest Pinus massonina forest (PMF) or mid-successional forest pine-broadleaf mixed forest (PBMF) soil promoted the growth of Mikania micrantha and Eupatorium catarium, but mycorrhizal fungi in MEBF soil had no significant effects on their growth. Pathogens plus other non-mycorrhizal microbes in MEBF soil inhibited the growth of M. micrantha and E. catarium significantly, and only inhibited root growth of E. catarium when compared with those with mycorrhizal fungi addition. The study suggest that soil mycorrhizal fungi of early-mid-successional forests benefit invasive species M. micrantha and E. catarium, while soil pathogens of late-successional forest may play an important role in resisting M. micrantha and E. catarium. The benefit and resistance of the soil microbes are dependent on invasive species and related to forest succession. The study gives a possible clue to control invasive plants by regulating soil microbes of forest community to resist plant invasion.     

Which components of plant diversity are most correlated with ecosystem properties? A case study in a restored wetland in northern China

The relationship between plant diversity and ecosystem services is a controversial topic in ecology that may be due, at least in part, to the variety of methods used to define and quantify diversity. This study examined the relationship between plant diversity and 11 ecosystem properties of a restored wetland in northern China by considering four primary components of diversity (dominance, richness, evenness, and divergence). Each diversity component was expressed by eight taxonomic and functional diversity indices respectively. Results showed that trait-based functional diversity had a stronger correlation with ecosystem processes than non-trait taxonomic diversity did. Among the four components of diversity, dominance (in terms of mean trait value index) was the best in explaining the variation in ecosystem processing. Richness and divergence also had significant correlations with ecosystem properties in some instances. By contrast, evenness had no significant correlation with most of the studied ecosystem properties. Our results indicated that wetland ecosystem properties are significantly related to certain traits of the dominant species. Thus, the dominant species and functional traits should be considered before the number of species in managing diversity and enhancing certain ecosystem functions of wetlands, especially in the case of conservation.     

Do anthropogenic corridors homogenize plant communities at a local scale? A case studied in Tenerife (Canary Islands)

Biological homogenization is defined as a process that occurs when native species are replaced by common and dominant exotic species or due to depletion and expansion of native species, reducing the beta diversity between areas or habitats. Islands are particularly vulnerable to plant invasion, and as a consequence, homogenization is a process that can become faster and more intense in islands than in continental areas. We recorded vascular plant species composition in roadside communities along a strong altitudinal gradient using plots beside the road and at two distances from the road (0–50 and 50–100 m). We analyzed the results separately for each group of plots with a Detrended Correspondence Analysis (DCA) including and excluding exotic species. The results revealed that where exotic species were most abundant, i.e., at the road edge, they can create an effect of floristic homogenization where three similar roads are compared. At a distance of >50 m from the road, where exotic species are less frequent, this effect has already disappeared, indicating that it is a local phenomenon, closely related to the highly disturbed roadside environment. Furthermore, floristic homogenization seems to be more important at higher altitudes (>1000 m), probably related to higher diversity in native plant communities and lower levels of human disturbances. Roads allow humans to reach relatively remote and sometimes well-conserved areas, and, at the same time, facilitate the spread of exotic plants and the most common native species which can locally create floristic homogenization in roadside communities on this oceanic island. A deeper understanding of the effects of these anthropogenic corridors at the local and regional scales is therefore required to integrate road planning and management with the aim of conserving the value of the natural areas.     

Do museum specimens accurately represent wild birds? A case study of carotenoid,melanin, and structural colours in long‐tailed manakins Chiroxiphia linearis

Museum specimens continue to be an invaluable resource for taxonomic, systematic, and comparative studies, and are increasingly relied upon for novel research purposes. Evaluating variation in the colour of avian study skins forms the basis for a broad range of research questions, yet few studies have investigated whether the plumage colouration of museum specimens accurately reflects colouration in wild birds. In this study, we use reflectance spectrometry to compare the plumage reflectance of avian museum skins and wild birds. We use long-tailed manakins Chiroxiphia linearis , to investigate these potential differences in colour. Long-tailed manakins are ideal for this type of study as their colourful plumage patches result from three primary plumage colouration mechanisms found in birds: melanin pigmentation, carotenoid pigmentation, and structural colouration. These features of their plumage allowed us to independently assess variation in each plumage colouration mechanism. Reflectance spectra obtained from museum specimens were very similar to those obtained from wild birds, and the colouration of specimens was usually well within the range of variation observed in wild birds. As such, museum specimens can accurately represent the colouration of wild birds. Nevertheless, we found significant differences in colouration between museum skins and wild birds. We documented differences in brightness, hue, saturation, and chroma, although the direction and magnitude of these differences varied by mechanism of colouration. Multivariate analyses revealed that the age of museum specimens and the time of year at which they were collected contributed to some of these differences. We discuss potential proximate causes of these changes in colour, many of which apply to both museum specimens and wild birds, and identify the types of studies that are likely to be most sensitive to these changes.     

Latitudinal changes in species diversity of permafrost wetland plant communities in Great Xing’an Mountain valleys of Northeast China

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude (P < 0.01), but decreased significantly in the shrub layer (P < 0.01). Species composition and the orders of dominant species in the plant communities by importance value changed along latitude. Latitudinal changes of α-diversity in permafrost wetland plant communities were different in the herb and shrub layers. With decreasing latitude, species richness and species diversity increased in the herb layer; but decreased in the shrub layer. The opposite patterns were found for species dominance. Species evenness in the shrub layer decreased with decreasing latitude. ?-diversity in the herb and shrub layers decreased first, and then increased, and finally decreased with increasing latitude. Species composition in the herb layer was similar among the plots at higher latitudes.     

Latitudinal changes in species diversity of permafrost wetland plant communities in Great Xing’an Mountain valleys of Northeast China

Studying the changes of species diversity in plant communities along latitude gradients is important to discover the correlation between biodiversity and environmental factors. Along the main ridges of the Great Xing’an Mountains, 12 natural permafrost wetlands in the valleys were investigated from north to south. Latitudinal changes in species diversity were analyzed with regressive analysis. About 150 plant species were recorded and were found to be in the 12 permafrost wetland plant communities. Most plants belong to the Compositae or Gramineae. The number of family, genus and species increased significantly in the herb layer with decreasing latitude (P < 0.01), but decreased significantly in the shrub layer (P < 0.01). Species composition and the orders of dominant species in the plant communities by importance value changed along latitude. Latitudinal changes of α-diversity in permafrost wetland plant communities were different in the herb and shrub layers. With decreasing latitude, species richness and species diversity increased in the herb layer; but decreased in the shrub layer. The opposite patterns were found for species dominance. Species evenness in the shrub layer decreased with decreasing latitude. ?-diversity in the herb and shrub layers decreased first, and then increased, and finally decreased with increasing latitude. Species composition in the herb layer was similar among the plots at higher latitudes.     

Do plant populations on distinct inselbergs talk to each other? A case study of genetic connectivity of a bromeliad species in an Ocbil landscape

Here, we explore the historical and contemporaneous patterns of connectivity among Encholirium horridum populations located on granitic inselbergs in an Ocbil landscape within the Brazilian Atlantic Forest, using both nuclear and chloroplast microsatellite markers. Beyond to assess the E. horridum population genetic structure, we built species distribution models across four periods (current conditions, mid‐Holocene, Last Glacial Maximum [LGM], and Last Interglacial) and inferred putative dispersal corridors using a least‐cost path analysis to elucidate biogeographic patterns. Overall, high and significant genetic divergence was estimated among populations for both nuclear and plastid DNA (Φ_ST(n) = 0.463 and Φ_ST(plastid) = 0.961, respectively, p < .001). For nuclear genome, almost total absence of genetic admixture among populations and very low migration rates were evident, corroborating with the very low estimates of immigration and emigration rates observed among E. horridum populations. Based on the cpDNA results, putative dispersal routes in Sugar Loaf Land across cycles of climatic fluctuations in the Quaternary period revealed that the populations’ connectivity changed little during those events. Genetic analyses highlighted the low genetic connectivity and long‐term persistence of populations, and the founder effect and genetic drift seemed to have been very important processes that shaped the current diversity and genetic structure observed in both genomes. The genetic singularity of each population clearly shows the need for in situ conservation of all of them.     

Do species converge during adaptation? A case study in Drosophila

Adaptation to novel environments is a crucial theme in evolutionary biology, particularly because ex situ conservation forces populations to adapt to captivity. Here we analyze the evolution of life-history traits in two closely related species, Drosophila subobscura Collin and Drosophila madeirensis Monclus, during adaptation to the laboratory. Drosophila madeirensis, an endemic species from Madeira, is here shown to have less ability to adapt to the laboratory. Early fecundity was the only trait where this species showed a significant improvement with time. By comparison, D. subobscura improved in most traits, and its early fecundity increased faster than that of D. madeirensis. Our findings suggest that different species, even closely related ones, may adapt at different rates to the same environment.     

Do changes in rainfall patterns affect semiarid annual plant communities?

Question: Climate change models forecast a reduction in annual precipitation and more extreme events (less rainy days and longer drought periods between rainfall events), which may have profound effects on terrestrial ecosystems. Plant growth, population and community dynamics in dry environments are likely to be affected by these changes since productivity is already limited by water availability. We tested the effects of reduced precipitation and fewer rain events on three semiarid plant communities dominated by annual species. Location: Three semiarid plant communities from Almería province (SE Spain). Methods: Rain‐out shelters were set up in each community and watering quantity and frequency were manipulated from autumn to early summer. Plant productivity, cover and diversity were measured at the end of the experimental period. Results: We found that a 50% reduction in watering reduced productivity, plant cover and diversity in all three communities. However, neither the 25% reduction in watering nor changes in the frequency of watering events affected these parameters. Conclusions: The lack of response to small reductions in water could be due to the identity and resistance of the plant communities involved, which are adapted to rainfall variability characteristic of arid environments. Therefore, a rainfall reduction of 25% or less may not affect these plant communities in the short term, although higher reductions or long‐term changes in water availability would probably reduce productivity and diversity in these communities.     

Are ecological communities the seat of endosymbiont horizontal transfer and diversification? A case study with soil arthropod community

Maternally inherited endosymbionts of arthropods are one of the most abundant and diverse group of bacteria. These bacterial endosymbionts also show extensive horizontal transfer to taxonomically unrelated hosts and widespread recombination in their genomes. Such horizontal transfers can be enhanced when different arthropod hosts come in contact like in an ecological community. Higher rates of horizontal transfer can also increase the probability of recombination between endosymbionts, as they now share the same host cytoplasm. However, reports of community‐wide endosymbiont data are rare as most studies choose few host taxa and specific ecological interactions among the hosts. To better understand endosymbiont spread within host populations, we investigated the incidence, diversity, extent of horizontal transfer, and recombination of three endosymbionts (Wolbachia, Cardinium, and Arsenophonus) in a specific soil arthropod community. Wolbachia strains were characterized with MLST genes whereas 16S rRNA gene was used for Cardinium and Arsenophonus. Among 3,509 individual host arthropods, belonging to 390 morphospecies, 12.05% were infected with Wolbachia, 2.82% with Cardinium and 2.05% with Arsenophonus. Phylogenetic incongruence between host and endosymbiont indicated extensive horizontal transfer of endosymbionts within this community. Three cases of recombination between Wolbachia supergroups and eight incidences of within‐supergroup recombination were also found. Statistical tests of similarity indicated supergroup A Wolbachia and Cardinium show a pattern consistent with extensive horizontal transfer within the community but not for supergroup B Wolbachia and Arsenophonus. We highlight the importance of extensive community‐wide studies for a better understanding of the spread of endosymbionts across global arthropod communities.     

The effect of hay blowing instead of hay raking on plant biodiversity – a case study of a dry meadow in a Swiss mountain region

Low-input dry meadows are habitats of high nature value. More and more, less time-consuming harvesting techniques replace different steps of the traditional hay making process. The use of leaf blowers instead of rakes for hay making became popular in the last ten years in Switzerland. Thus, we set up a case study to test effects on the conservation value. The studied dry meadow of high nature value is located in the municipality of Stans (Switzerland). After five years no significant differences between blown and raked plots in species richness, richness of target an indicator species, medium plant-indicator values, i.e. nutrients, humidity, light or in the species assemblages were observed. From 2010 until 2014 the moss cover increased in all plots. The differences between raked and blown plots were not significant. In 2015, however, the difference between the two treatments increased to 13%. While the moss cover of the blown plots remained at 20%, the moss cover of the raked plots dropped to 7%. These results from only one case study and only a short observation period of five years do not allow a generalization, but they give a first impression of the short-term effects. We recommend managers of dry meadows with high nature values to keep an eye on the change of moss cover and potential changes of conservation values when leaf blowers instead of rakes are used for hay harvesting.     

Can soil temperature direct the composition of high arctic plant communities?

Abstract. Low temperatures exert a primary constraint on the growth of high arctic vascular plants. However, investigations into the impact of temperature on high arctic plants rarely separate out the role of air and soil temperatures, and few data exist to indicate whether soil temperatures alone can significantly influence the growth of high arctic vascular plants in a manner that might direct community composition. We examined the response of high arctic plants of three functional types (grasses, sedges/rushes and non‐graminoids) to manipulated soil temperature under common air temperature conditions. Target plants, within intact soil cores, were placed in water baths at a range of temperatures between 4.9 and 15.3 °C for one growing season. Grasses responded most rapidly to increased soil temperature, with increased total live plant mass, above‐ground live mass and total below‐ground live mass, with non‐graminoids having the lowest, and sedges/rushes an intermediate degree of response. The ratio of above‐ground live mass to total live mass increased in all growth forms. Grasses, in particular, responded to enhanced soil temperatures by increasing shoot size rather than shoot number. In all growth forms the mass of root tissue beneath the moss layer increased significantly and to a similar extent with increasing soil temperature. These results clearly indicate that different growth forms, although collected from the same plant community, respond differently to changes in soil temperature. As a consequence, factors influencing soil temperature in high arctic ecosystems, such as global climate change or herbivory (which leads to reduced moss depth and increased soil temperatures), may also direct changes in vascular plant community composition.     

Impact of land use on plant biodiversity and measures for biodiversity conservation in the Loess Plateau in China – a case study in a hilly-gully region of the Northern Loess Plateau

The Loess Plateau is a special natural–cultural unit in northern China. Intensive land use in the past has had, and forestation and grass planting at present will have inevitable impacts on plant biodiversity in the Loess Plateau. Based on the analysis of floristic features within three sampling sites with different land use practices and analysis of species richness among different land use types, we discuss impacts of land use on species richness and floristic features in the Northern Loess Plateau. The results drawn from this case study are as follows: (1) It appears that forestation and grass planting have had a positive influence on the local species diversity, but they have contributed little to the native vegetation in terms of conserving its floristic features. (2) Caragana intermedia shrubland, Pinus tabulaeformis forestland, and natural grassland have made important contributions to supporting indigenous species and maintaining local plant biodiversity. (3) There is a significant positive correlation between land use diversity and species richness. These results imply that practicing biodiversity conservation in situ is feasible and the suitable choice for the Loess Plateau. Concrete measures for biodiversity conservation in the area can include setting up small nature reserves and diversifying land use patterns to maintain as much habitat as possible for native vegetation. The artificial Hippophae rhamnoides shrubland should not be further promoted, considering its negative influence on biodiversity conservation.     

Do all inter-patch movements represent dispersal? A mixed kernel study of butterfly mobility in fragmented landscapes

1. In times of ongoing habitat fragmentation, the persistence of many species is determined by their dispersal abilities. Consequently, understanding the rules underlying movement between habitat patches is a key issue in conservation ecology. 2. We have analysed mark-release-recapture (MRR) data on inter-patches movements of the Dusky Large Blue butterfly Maculinea nausithous in a fragmented landscape in northern Bavaria, Germany. The aim of the analysis was to quantify distance dependence of dispersal as well as to evaluate the effect of target patch area on immigration probability. For statistical evaluation, we apply a 'reduced version' of the virtual migration model (VM), only fitting parameters for dispersal distance and immigration. In contrast to other analyses, we fit a mixed dispersal kernel to the MRR data. 3. A large fraction of recaptures happened in other habitat patches than those where individuals were initially caught. Further, we found significant evidence for the presence of a mixed dispersal kernel. The results indicate that individuals follow different strategies in their movements. Most movements are performed over small distances, nonetheless involving travelling between nearby habitat patches (median distance c. 480 m). A small fraction (c. 0·025) of the population has a tendency to move over larger distances (median distance c. 3800 m). Further, immigration was positively affected by patch area (I～A(ζ) ), with the scaling parameter ζ = 0·5. 4. Our findings should help to resolve the long-lasting dispute over the suitability of the negative exponential function vs. inverse-power one for modelling dispersal. Previous studies on various organisms found that the former typically gives better overall fit to empirical distance distributions, but that the latter better represents long-distance movement probabilities. As long-distance movements are more important for landscape-level effects and thus, e.g. for conservation-oriented analyses like PVAs, fitting inverse-power kernels has often been preferred. 5. We conclude that the above discrepancy may simply stem from the fact that recorded inter-patch movements are an outcome of two different processes: daily routine movements and genuine dispersal. Consequently, applying mixed dispersal kernels to disentangle the two processes is recommended.     

Do interactions between plant and soil biota change with elevation? A study on Fagus sylvatica

Theoretical models predict weakening of negative biotic interactions and strengthening of positive interactions with increasing abiotic stress. However, most empirical tests have been restricted to plant-plant interactions. No empirical study has examined theoretical predictions of interactions between plants and below-ground micro-organisms, although soil biota strongly regulates plant community composition and dynamics. We examined variability in soil biota effects on tree regeneration across an abiotic gradient. Our candidate tree species was European beech (Fagus sylvatica L.), whose regeneration is extremely responsive to soil biota activity. In a greenhouse experiment, we measured tree survival in sterilized and non-sterilized soils collected across an elevation gradient in the French Alps. Negative effects of soil biota on tree survival decreased with elevation, similar to shifts observed in plant-plant interactions. Hence, soil biota effects must be included in theoretical models of plant biotic interactions to accurately represent and predict the effects of abiotic gradient on plant communities.     

Do asynchronies in extinction debt affect the structure of trophic networks? A case study of antagonistic butterfly larvae–plant networks

Habitat loss and fragmentation affect species richness in fragmented habitats and can lead to immediate or time‐delayed species extinctions. Asynchronies in extinction and extinction debt between interacting species may have severe effects on ecological networks. However, these effects remain largely unknown. We evaluated the effects of habitat patch and landscape changes on antagonistic butterfly larvae–plant trophic networks in Mediterranean grasslands in which previous studies had shown the existence of extinction debt in plants but not in butterflies. We sampled current species richness of habitat‐specialist and generalist butterflies and vascular plants in 26 grasslands. We assessed the direct effects of historical and current patch and landscape characteristics on species richness and on butterfly larvae–plant trophic network metrics and robustness. Although positive species‐ and interactions–area relationships were found in all networks, structure and robustness was only affected by patch and landscape changes in networks involving the subset of butterfly specialists. Larger patches had more species (butterflies and host plants) and interactions but also more compartments, which decreased network connectance but increased network stability. Moreover, most likely due to the rescue effect, patch connectivity increased host‐plant species (but not butterfly) richness and total links, and network robustness in specialist networks. On the other hand, patch area loss decreased robustness in specialist butterfly larvae–plant networks and made them more prone to collapse against host plant extinctions. Finally, in all butterfly larvae–plant networks we also detected a past patch and landscape effect on network asymmetry, which indicates that there were different extinction rates and extinction debts for butterflies and host plants. We conclude that asynchronies in extinction and extinction debt in butterfly–plant networks provoked by patch and landscape changes caused changes in species richness and network links in all networks, as well as changes in network structure and robustness in specialist networks.     

Do endogeic earthworms change plant competition? A microcosm study

Plants compete for limited resources. Although nutrient availability for plants is affected by resource distribution and soil organisms, surprisingly few studies investigate their combined effects on plant growth and competition. Effects of endogeic earthworms (Aporrectodea jassyensis), root-knot nematodes (Meloidogyne incognita) and the spatial distribution of ¹⁵N labelled grass litter on the competition between a grass (Lolium perenne), a forb (Plantago lanceolata) and a legume (Trifolium repens) were investigated in the greenhouse. Earthworms promoted N uptake and growth of L. perenne. Contrastingly, shoot biomass and N uptake of T. repens decreased in the presence of earthworms. P. lanceolata was not affected by the earthworms. We suggest that earthworms enhanced the competitive ability of L. perenne against T. repens. Nematodes increased the proportion of litter N in each of the plant species. Litter distribution (homogeneous vs. patch) did not affect the biomass of any plant species. However, P. lanceolata took up more ¹⁵N, when the litter was homogeneously mixed into the soil. The results suggest that endogeic earthworms may affect plant competition by promoting individual plant species. More studies including decomposers are necessary to understand their role in determining plant community structure.