Effects of three coniferous plantation species on plant-soil feedbacks and soil physical and chemical properties in semiarid mountain ecosystems

Background:Large-scale afforestation can significantly change the ground cover and soil physicochemical properties,especially the soil fertility maintenance and water conservation functions of artificial forests,which are very important in semi-arid mountain ecosystems.However,how different tree species affect soil nutrients and soil physicochemical properties after afforestation,and which is the best plantation species for improving soil fertility and water conservation functions remain largely unknown.Methods:This study investigated the soil nutrient contents of three different plantations(Larix principis-rupprechtii,Picea crassifolia,Pinus tabuliformis),soils and plant-soil feedbacks,as well as the interactions between soil physicochemical properties.Results:The results revealed that the leaves and litter layers strongly influenced soil nutrient availability through biogeochemical processes:P.tabuliformis had higher organic carbon,ratio of organic carbon to total nitrogen(C:N)and organic carbon to total phosphorus(C:P)in the leaves and litter layers than L.principis-rupprechtii or P.crassifolia,suggesting that higher C:N and C:P hindered litter decomposition.As a result,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved soil nutrients and clay components,compared with the P.tabuliformis plantation forest.Furthermore,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved the soil capacity,soil total porosity,and capillary porosity,decreased soil bulk density,and enhanced water storage capacity,compared with the P.tabuliformis plantation forest.The results of this study showed that,the strong link between plants and soil was tightly coupled to C:N and C:P,and there was a close correlation between soil particle size distribution and soil physicochemical properties.Conclusions:Therefore,our results recommend planting the L.principis-rupprechtii and P.crassifolia as the preferred tree species to enhance the soil fertility and water conservation functions,especially in semi-arid regions mountain forest ecosystems.

Mechanism of plant-soil feedback in a degraded alpine grassland on the Tibetan Plateau

Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics,their interactive effects have yet to be fully considered in grassland degradation.Herein,we tested how soil nutrients and microbes regulated plant-soil feedback(PSF)in a degraded alpine grassland.Our results indicated that soil total carbon(STC;from 17.66 to 12.55 g/kg)and total nitrogen(STN;from 3.16 to 2.74 g/kg)exhibited significant(P<0.05)decrease from non-degraded(ND)to severely degraded(SD).Despite higher nutrients in ND soil generating significantly(P<0.05)positive PSF(0.52)on monocots growth when the soil was sterilized,a high proportion of pathogens(36%)in ND non-sterilized soil resulted in a strong negative PSF on monocots.In contrast,the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes(70%)strongly promoted their survival and growth in SD with infertile soil.Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil.The emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland.

Similarity in fine-to-total root mass ratio leads to comparative plant-soil feedbacks between co-occurring native and invasive plants

Aims Soil biota can affect plant-plant interactions and non-native plant invasions via plant-soil feedback(PSF).Understanding the drivers underlying interspecific variations in PSF is im portant for predicting the role of soil biota in non-native plant invasions.Recent studies found that PSF could be predicted by plant traits.The success of plant invasions is also linked with plant traits,suggesting a potential linkage between PSF and plant invasion via plant traits,but has not yet been tested.Here,we compared PSF between six phylogenetically paired co-occurring native and invasive plants,and explored the potential linkage between PSF with plant root traits.Methods We conducted a two-phase PSF experiment.Field collected soils were conditioned by the six plant species for 3 months firstly,then seedllings of these plants were grown in living or sterilized soils that had been conditioned by conspecific vs.heterospecific(the conge ner/confamilial species)individuals.We estimated effects of biota in conspecific(conspecific PSF)or heterospecific(heterospecific PSF)soils relative to sterilized soils,and the relative effects of biota in conspecific vs.heterospecific soils(PSF-away)on plant biomass.Important Findings In general,soil biota suppressed plant growth,and there were no differences in conspecific PSF,heterospecific PSF and PSF-away between native and invasive plants.PSF increased with rising plant fineto-total root mass ratio in the presence of soil biota,and its value was comparable between native and invasive plants.Our results indicate that similarity in plant fine-to-total root mass ratio that predicted PSF may have partially led to the comparable PSFs between these native and invasive plants.Studies exploring the linkages among plant traits,PSF and plant invasions with more plants,in particular phylogenetically distant plants,are needed to improve our understanding of the role of soil biota in plant invasions.

Invasive grasses consistently create similar plant-soil feedback types in soils collected from geographically distant locations

Aims Plants of similar life forms and closely related species have been observed to create similar types of plant–soil feedbacks(PSFs).However,investigations of the consistency of PSFs within species have not yielded clear results.For example,it has been reported that species create different types of PSFs in their native and introduced ranges.The aim of this project is to examine if four species create similar PSF types from soils collected from widely distributed areas within their introduced range.The soil for this project was collected from three areas in western North America.With this design,we aim to determine species-and site-specific ability to create PSFs and if the type of PSF created is consistent in all soil from all three collection areas.The species examined are Agropyron cristatum,Centaurea solstitialis,Poa pratensis and Taeniatherum caput-medusae.Methods We used three-field collected soils(from northern Nevada,western Montana and eastern Montana)in a two-phase greenhouse experiment to quantify the type of PSFs created by four invasive species.The first phase was a conditioning phase wherein each invasive species created species-specific changes to the soil.The second phase of the experiment was the response phase wherein both the conditioning species and a native phytometer were grown in the conditioned soil and in unconditioned(control)soil.The final aboveground biomass was used to evaluate the effect of conditioning and to determine the type of PSF created by each invasive species.Important Findings Our results suggest that three of our four study species did show consistency in relation to PSF.Two species A.cristatum and T.caputmedusae consistently created PSF types that benefit conspecifics more than heterospecifics(and thus are‘invasive’PSF types)and P.pratensis consistently exhibited no,or‘neutral’,feedbacks.The fourth species(C.solstitialis)was inconsistent:in one soil,no feedback was created;in other soil,an invasive PSF was created and in the last soil,a feedback that relatively benefited the native phytometer was created.Thus,PSFs appear to uniformly contribute to the success of two species(A.cristatum and T.caput-medusae)but not C.solstitialis nor P.pratensis.

Soil legacy effects and plant-soil feedback contribution to secondary succession processes

Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.

A comprehensive review on coupled processes and mechanisms of soil-vegetation-hydrology, and recent research advances

Research on the coupling of soil,vegetation,and hydrological processes is not only a research hotspot in disciplines such as pedology,ecohydrology and Earth system science but also important for achieving sustainable development.However,scientists from different disciplines usually study the coupling mechanism of soil-vegetation-hydrological processes at very different space and time scales,and the mechanistic connections between different scales are quite few.This article reviewed research advances in coupled soil-vegetation-hydrological processes at different spatial scales—from leaf stomata to watershed and regional scales—and summarized the spatial upscaling methods and modeling approaches of coupled soil-vegetationhydrological processes.We identify and summarize the following coupling processes:(1)carbon-water exchange in leaf stomata and root-soil interface;(2)changes in soil aggregates and profile hydraulic properties caused by plant roots and water movement;(3)precipitation and soil moisture redistribution by plant canopy and root;(4)interactions between vegetation patches and local hydrological process;(5)links between plant community succession and soil development;and(6)links between watershed/regional water budget and vegetation phenology and production.Meanwhile,the limitations and knowledge gaps in the observations,mechanisms,scaling methods,and modeling approaches of coupled soil-vegetation-hydrological processes were analyzed.To achieve a deep integration of various coupling processes across different spatiotemporal scales,future work should strengthen multiscale,multifactor and multiprocess soil-vegetation-hydrology coupling observations and mechanism studies,develop new scaling methods,identify different feedback pathways,and take time-variable plant behavior and soil hydraulic properties into account during modeling.

An invading annual plant benefits less from soil biota and has reduced competitive power with a resident grass

Aims Interactions between plants and their soil biota,arbuscular mycorrhizal fungi(AMF)in particular,may play a vital role in the establishment and the range expansion of exotic plants in new environments.However,whether there are post-introduction shifts in dependence on AMF and how dependency interacts with competition remains poorly understood.Methods We conducted a common garden greenhouse experiment to examine how native(USA)and invasive(China)populations of the plant species Plantago virginica,respond to soil biota,and whether these responses change in the presence of a competitor.Important Findings We found that while native populations consistently had a higher AMF colonization rate and benefited from AMF in both biomass and seed production,invasive populations received less benefit from AMF,and even showed reduced biomass with AMF in the presence of a competitor.This low mycorrhizal dependency in invasive populations correlated with greater suppression by an indigenous competitor for the invader.The different responses of the invasive and native populations to AMF suggest that alteration of mycorrhizal dependency has occurred during the invasion of P.virginica into China.Our findings suggest that this reduced dependency incurs a cost during interspecific competition.

No consistent legacy effects of invasion by giant goldenrod(Solidago gigantea)via soil biota on native plant growth

Aims Changes in soil microbial communities after occupation by invasive alien plants can represent legacy effects of invasion that may limit recolonization and establishment of native plant species in soils previously occupied by the invader.In this study,for three sites in southern Germany,we investigated whether invasion by giant goldenrod(Solidago gigantea)leads to changes in soil biota that result in reduced growth of native plants compared with neighbouring uninvaded soils.Methods We grew four native plant species as a community and treated those plants with soil solutions from invaded or uninvaded soils that were sterilized,or live,with live solutions containing different fractions of the soil biota using a decreasing sieve mesh-size approach.We measured aboveground biomass of the plants in the communities after a 10-week growth period.Main FindingsAcross all three sites and regardless of invasion,communities treated with<20μm soil biota or sterilized soil solutions had significantly greater biomass than communities treated with the complete soil biota solution.This indicates that soil biota>20μm are more pathogenic to the native plants than smaller organisms in these soils.Across all three sites,there was only a non-significant tendency for the native community biomass to differ among soil solution types,depending on whether or not the soil was invaded.Only one site showed significant differences in community biomass among soil solution types,depending on whether or not the soil was invaded;community biomass was significantly lower when treated with the complete soil biota solution than with soil biota<20μm or sterilized soil solutions,but only for the invaded soil.Our findings suggest that efforts to restore native communities on soils previously invaded by Solidago gigantea are unlikely to be hindered by changes in soil microbial community composition as a result of previous invasion.