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Soil Feedbacks (soil + feedback)
Selected AbstractsPlant,soil feedbacks: a meta-analytical reviewECOLOGY LETTERS, Issue 9 2008Andrew Kulmatiski Abstract Plants can change soil biology, chemistry and structure in ways that alter subsequent plant growth. This process, referred to as plant,soil feedback (PSF), has been suggested to provide mechanisms for plant diversity, succession and invasion. Here we use three meta-analytical models: a mixed model and two Bayes models, one correcting for sampling dependence and one correcting for sampling and hierarchical dependence (delta-splitting model) to test these hypotheses. All three models showed that PSFs have medium to large negative effects on plant growth, and especially grass growth, the life form for which we had the most data. This supports the hypothesis that PSFs, through negative frequency dependence, maintain plant diversity, especially in grasslands. PSFs were also large and negative for annuals and natives, but the delta-splitting model indicated that more studies are needed for these results to be conclusive. Our results support the hypotheses that PSFs encourage successional replacements and plant invasions. Most studies were performed using monocultures of grassland species in greenhouse conditions. Future research should examine PSFs in plant communities, non-grassland systems and field conditions. [source] Microscale vegetation-soil feedback boosts hysteresis in a regional vegetation,climate systemGLOBAL CHANGE BIOLOGY, Issue 5 2008RUUD H. H. JANSSEN Abstract It has been hypothesized that a positive feedback between vegetation cover and monsoon circulation may lead to the existence of two alternative stable states in the Sahara region: a vegetated state with moderate precipitation and a desert state with low precipitation. This could explain the sudden onset of desertification in the region about 5000 years ago. However, other models suggest that the effect of vegetation on the precipitation may be insufficient to produce this behavior. Here, we show that inclusion of the microscale feedback between soil and vegetation in the model greatly amplifies the nonlinearity, causing alternative stable states and considerable hysteresis even if the effect of vegetation on precipitation is moderate. On the other hand, our analysis suggests that self-organized vegetation patterns known from models that only focus at the microscale plant,soil feedback will be limited to a narrower range of conditions due to the regional scale climate-feedback. This implies that in monsoon areas such as the Western Sahara self-organized vegetation patterns are predicted to be less common than in areas without monsoon circulation such as Central Australia. [source] Influence of plant species and soil conditions on plant,soil feedback in mixed grassland communitiesJOURNAL OF ECOLOGY, Issue 2 2010Kathryn A. Harrison Summary 1.,Our aim was to explore plant,soil feedback in mixed grassland communities and its significance for plant productivity and community composition relative to abiotic factors of soil type and fertility. 2.,We carried out a 4-year, field-based mesocosm experiment to determine the relative effects of soil type, historic management intensity and soil conditioning by a wide range of plant species of mesotrophic grassland on the productivity and evenness of subsequent mixed communities. 3.,The study consisted of an initial soil conditioning phase, whereby soil from two locations each with two levels of management intensity was conditioned with monocultures of nine grassland species, and a subsequent feedback phase, where mixed communities of the nine species were grown in conditioned soil to determine relative effects of experimental factors on the productivity and evenness of mixed communities and individual plant species performance. 4.,In the conditioning phase of the experiment, individual plant species differentially influenced soil microbial communities and nutrient availability. However, these biotic effects were much less important as drivers of soil microbial properties and nutrient availability than were abiotic factors of soil type and fertility. 5.,Significant feedback effects of conditioning were detected during the second phase of the study in terms of individual plant growth in mixed communities. These feedback effects were generally independent of soil type or fertility, and were consistently negative in nature. In most cases, individual plant species performed less well in mixed communities planted in soil that had previously supported their own species. 6.,Synthesis. These findings suggest that despite soil abiotic factors acting as major drivers of soil microbial communities and nutrient availability, biotic interactions in the form of negative feedback play a significant role in regulating individual plant performance in mixed grassland communities across a range of soil conditions. [source] Plant,soil feedback induces shifts in biomass allocation in the invasive plant Chromolaena odorataJOURNAL OF ECOLOGY, Issue 6 2009Mariska Te Beest Summary 1. ,Soil communities and their interactions with plants may play a major role in determining the success of invasive species. However, rigorous investigations of this idea using cross-continental comparisons, including native and invasive plant populations, are still scarce. 2. ,We investigated if interactions with the soil community affect the growth and biomass allocation of the (sub)tropical invasive shrub Chromolaena odorata. We performed a cross-continental comparison with both native and non-native-range soil and native and non-native-range plant populations in two glasshouse experiments. 3. ,Results are interpreted in the light of three prominent hypotheses that explain the dominance of invasive plants in the non-native range: the enemy release hypothesis, the evolution of increased competitive ability hypothesis and the accumulation of local pathogens hypothesis. 4. ,Our results show that C. odorata performed significantly better when grown in soil pre-cultured by a plant species other than C. odorata. Soil communities from the native and non-native ranges did not differ in their effect on C. odorata performance. However, soil origin had a significant effect on plant allocation responses. 5. ,Non-native C. odorata plants increased relative allocation to stem biomass and height growth when confronted with soil communities from the non-native range. This is a plastic response that may allow species to be more successful when competing for light. This response differed between native and non-native-range populations, suggesting that selection may have taken place during the process of invasion. Whether this plastic response to soil organisms will indeed select for increased competitive ability needs further study. 6. ,The native grass Panicum maximum did not perform worse when grown in soil pre-cultured by C. odorata. Therefore, our results did not support the accumulation of local pathogens hypothesis. 7. ,Synthesis. Non-native C. odorata did not show release from soil-borne enemies compared to its native range. However, non-native plants responded to soil biota from the non-native range by enhanced allocation in stem biomass and height growth. This response can affect the competitive balance between native and invasive species. The evolutionary potential of this soil biota-induced change in plant biomass allocation needs further study. [source] Plant species and functional group effects on abiotic and microbial soil properties and plant,soil feedback responses in two grasslandsJOURNAL OF ECOLOGY, Issue 5 2006T. MARTIJN BEZEMER Summary 1Plant species differ in their capacity to influence soil organic matter, soil nutrient availability and the composition of soil microbial communities. Their influences on soil properties result in net positive or negative feedback effects, which influence plant performance and plant community composition. 2For two grassland systems, one on a sandy soil in the Netherlands and one on a chalk soil in the United Kingdom, we investigated how individual plant species grown in monocultures changed abiotic and biotic soil conditions. Then, we determined feedback effects of these soils to plants of the same or different species. Feedback effects were analysed at the level of plant species and plant taxonomic groups (grasses vs. forbs). 3In the sandy soils, plant species differed in their effects on soil chemical properties, in particular potassium levels, but PLFA (phospholipid fatty acid) signatures of the soil microbial community did not differ between plant species. The effects of soil chemical properties were even greater when grasses and forbs were compared, especially because potassium levels were lower in grass monocultures. 4In the chalk soil, there were no effects of plant species on soil chemical properties, but PLFA profiles differed significantly between soils from different monocultures. PLFA profiles differed between species, rather than between grasses and forbs. 5In the feedback experiment, all plant species in sandy soils grew less vigorously in soils conditioned by grasses than in soils conditioned by forbs. These effects correlated significantly with soil chemical properties. None of the seven plant species showed significant differences between performance in soil conditioned by the same vs. other plant species. 6In the chalk soil, Sanguisorba minor and in particular Briza media performed best in soil collected from conspecifics, while Bromus erectus performed best in soil from heterospecifics. There was no distinctive pattern between soils collected from forb and grass monocultures, and plant performance could not be related to soil chemical properties or PLFA signatures. 7Our study shows that mechanisms of plant,soil feedback can depend on plant species, plant taxonomic (or functional) groups and site-specific differences in abiotic and biotic soil properties. Understanding how plant species can influence their rhizosphere, and how other plant species respond to these changes, will greatly enhance our understanding of the functioning and stability of ecosystems. [source] Plant,soil feedbacks: a meta-analytical reviewECOLOGY LETTERS, Issue 9 2008Andrew Kulmatiski Abstract Plants can change soil biology, chemistry and structure in ways that alter subsequent plant growth. This process, referred to as plant,soil feedback (PSF), has been suggested to provide mechanisms for plant diversity, succession and invasion. Here we use three meta-analytical models: a mixed model and two Bayes models, one correcting for sampling dependence and one correcting for sampling and hierarchical dependence (delta-splitting model) to test these hypotheses. All three models showed that PSFs have medium to large negative effects on plant growth, and especially grass growth, the life form for which we had the most data. This supports the hypothesis that PSFs, through negative frequency dependence, maintain plant diversity, especially in grasslands. PSFs were also large and negative for annuals and natives, but the delta-splitting model indicated that more studies are needed for these results to be conclusive. Our results support the hypotheses that PSFs encourage successional replacements and plant invasions. Most studies were performed using monocultures of grassland species in greenhouse conditions. Future research should examine PSFs in plant communities, non-grassland systems and field conditions. [source] Plant,soil feedbacks and invasive spreadECOLOGY LETTERS, Issue 9 2006Jonathan M. Levine Abstract Plant invaders have been suggested to change soil microbial communities and biogeochemical cycling in ways that can feedback to benefit themselves. In this paper, we ask when do these feedbacks influence the spread of exotic plants. Because answering this question is empirically challenging, we show how ecological theory on ,pushed' and ,pulled' invasions can be used to examine the problem. We incorporate soil feedbacks into annual plant invasion models, derive the conditions under which such feedbacks affect spread, and support our approach with simulations. We show that in homogeneous landscapes, strong positive feedbacks can influence spreading velocity for annual invaders, but that empirically documented feedbacks are not strong enough to do so. Moreover, to influence spread, invaders must modify the soil environment over a spatial scale larger than is biologically realistic. Though unimportant for annual invader spread in our models, feedbacks do affect invader density and potential impact. We discuss how future research might consider the way landscape structure, dispersal patterns, and the time scales over which plant,soil feedbacks develop regulate the effects of such feedbacks on invader spread. [source] Conspecific plant,soil feedbacks reduce survivorship and growth of tropical tree seedlingsJOURNAL OF ECOLOGY, Issue 2 2010Sarah McCarthy-Neumann Summary 1.,The Janzen,Connell (J,C) Model proposes that host-specific enemies maintain high tree species diversity by reducing seedling performance near conspecific adults and promoting replacement by heterospecific seedlings. Support for this model often comes from decreased performance for a species at near versus far distances from conspecific adults. However, the relative success of conspecific versus heterospecific seedlings recruiting under a given tree species is a critical, but untested, component of the J,C Model. 2.,In a shade-house experiment, we tested plant,soil feedbacks as a J,C mechanism in six tropical tree species. We assessed effects of conspecific versus heterospecific cultured soil extracts on seedling performance for each species, and we compared performance of conspecific versus heterospecific seedlings grown with soil extract cultured by a particular tree species. Additionally, we tested whether soil microbes were creating these plant,soil feedbacks and whether low light increased species vulnerability to pathogens. 3.,Among 30 potential comparisons of survival and mass for seedlings grown in conspecific versus heterospecific soil extracts, survival decreased in seven and increased in two, whereas mass decreased in 13 and increased in 1. To integrate survival and growth, we also examined seedling performance [(mean total mass × mean survival time)/(days of experiment)], which was lower in 16 and higher in 2 of 30 comparisons between seedlings grown with soil extract cultured by conspecific versus heterospecific individuals. Based on performance within a soil extract, conspecific seedlings were disadvantaged in 15 and favoured in 7 of 30 cases relative to heterospecific seedlings. 4.,Species pairwise interactions of soil modification and seedling performance occurred regardless of sterilization, suggesting chemical mediation. Microbes lacked host-specificity and reduced performance regardless of extract source and irradiance. 5.,Synthesis. These results, along with parallel research in temperate forests, suggest that plant,soil feedbacks are an important component of seedling dynamics in both ecosystems. However, negative conspecific feedbacks were more prevalent in tropical than temperate species. Thus, negative plant,soil feedbacks appear to facilitate species coexistence via negative distance-dependent processes in tropical but not temperate forests, but the feedbacks were mediated through chemical effects rather than through natural enemies as expected under the J,C Model. [source] Carbon flux from plants to soil: roots are a below-ground source of phenolic secondary compounds in an alpine ecosystemJOURNAL OF ECOLOGY, Issue 3 2008Courtney L. Meier Summary 1Phenolics are an important, biologically reactive component of the carbon (C) pool that moves from plants to soil. Once in soil, phenolics can regulate plant,soil feedbacks because of their influence on soil nitrogen biogeochemistry. 2Roots are a largely overlooked potential source of below-ground phenolic C. We examined phenolic fluxes from plants to soil in an alpine ecosystem, where phenolics are associated with slow rates of nutrient cycling. Using a phenolic-rich forb (Acomastylis rossii) and a grass with low tissue phenolics (Deschampsia caespitosa), we asked whether leaves, leaf litter or roots are the dominant source of soil phenolics during the growing season. We also determined whether the composition of root-derived phenolics differed from that of leaf litter. 3Both labile low molecular weight phenolics and tannins disappeared from A. rossii leaf litter over the winter. Evidence from this study and others indicates litter phenolics are not a significant source of labile C for soil microbes throughout the growing season. 4In the field, levels of phenolics were higher under A. rossii canopies than under D. caespitosa canopies throughout the growing season. We also estimated significantly higher phenolic fluxes into soils for A. rossii than for D. caespitosa in the glasshouse. Field and glasshouse results suggest roots are an important source of these compounds. Furthermore, the phenolic chemistry of roots was different from that of leaf litter, indicating that the effects of root phenolics on soil processes and neighbouring plant growth may differ from those associated with leaves. 5Synthesis. Based on our results, labile phenolic inputs from roots are likely to have a more important influence on soil nutrient dynamics during the alpine growing season than phenolic inputs from leaf litter. We suggest that roots may be the dominant input of labile phenolics to soil during the growing season in other ecosystems with seasonal patterns of plant growth and senescence. These observations are critical to our understanding of how phenolic-rich species may interact with soil microbes to influence soil nutrient cycling and shape the soil resource environment. [source] Activated Carbon as a Restoration Tool: Potential for Control of Invasive Plants in Abandoned Agricultural FieldsRESTORATION ECOLOGY, Issue 2 2006Andrew Kulmatiski Abstract Exotic plants have been found to use allelochemicals, positive plant,soil feedbacks, and high concentrations of soil nutrients to exercise a competitive advantage over native plants. Under laboratory conditions, activated carbon (AC) has shown the potential to reduce these advantages by sequestering organic compounds. It is not known, however, if AC can effectively sequester organics or reduce exotic plant growth under field conditions. On soils dominated by exotic plants, we found that AC additions (1% AC by mass in the top 10 cm of soil) reduced concentrations of extractable organic C and N and induced consistent changes in plant community composition. The cover of two dominant exotics, Bromus tectorum and Centaurea diffusa, decreased on AC plots compared to that on control plots (14,8% and 4,0.1%, respectively), and the cover of native perennial grasses increased on AC plots compared to that on control plots (1.4,3% cover). Despite promising responses to AC by these species, some exotic species responded positively to AC and some native species responded negatively to AC. Consequently, AC addition did not result in native plant communities similar to uninvaded sites, but AC did demonstrate potential as a soil-based exotic plant control tool, especially for B. tectorum and C. diffusa. [source] | ||||||||||