Summary
Plant–soil feedbacks is becoming an important concept for explaining vegetation dynamics, the invasiveness of introduced exotic species in new habitats and how terrestrial ecosystems respond to global land use and climate change. Using a new conceptual model, we show how critical alterations in plant–soil feedback interactions can change the assemblage of plant communities. We highlight recent advances, define terms and identify future challenges in this area of research and discuss how variations in strengths and directions of plant–soil feedbacks can explain succession, invasion, response to climate warming and diversity-productivity relationships.
While there has been a rapid increase in understanding the biological, chemical and physical mechanisms and their interdependencies underlying plant–soil feedback interactions, further progress is to be expected from applying new experimental techniques and technologies, linking empirical studies to modelling and field-based studies that can include plant–soil feedback interactions on longer time scales that also include long-term processes such as litter decomposition and mineralization.
Significant progress has also been made in analysing consequences of plant–soil feedbacks for biodiversity-functioning relationships, plant fitness and selection.
To further integrate plant–soil feedbacks into ecological theory, it will be important to determine where and how observed patterns may be generalized, and how they may influence evolution.
Synthesis. Gaining a greater understanding of plant–soil feedbacks and underlying mechanisms is improving our ability to predict consequences of these interactions for plant community composition and productivity under a variety of conditions. Future research will enable better prediction and mitigation of the consequences of human-induced global changes, improve efforts of restoration and conservation and promote sustainable provision of ecosystem services in a rapidly changing world.

https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1111/1365-2745.12054

Plant–soil feedbacks: the past, the present and future challenges

Summary 1. Plant–soil feedbacks is becoming an important concept for explaining vegetation dynamics, the invasiveness of introduced exotic species in new habitats and how terrestrial ecosystems respond to global land use and climate change. Using a new conceptual model, we show how critical alterations in plant–soil feedback interactions can change the assemblage of plant communities. We highlight recent advances, define terms and identify future challenges in this area of research and discuss how variations in strengths and directions of plant–soil feedbacks can explain succession, invasion, response to climate warming and diversity-productivity relationships. 2. While there has been a rapid increase in understanding the biological, chemical and physical mechanisms and their interdependencies underlying plant–soil feedback interactions, further progress is to be expected from applying new experimental techniques and technologies, linking empirical studies to modelling and field-based studies that can include plant–soil feedback interactions on longer time scales that also include long-term processes such as litter decomposition and mineralization. 3. Significant progress has also been made in analysing consequences of plant–soil feedbacks for biodiversity-functioning relationships, plant fitness and selection. 4. To further integrate plant–soil feedbacks into ecological theory, it will be important to determine where and how observed patterns may be generalized, and how they may influence evolution. 5. Synthesis. Gaining a greater understanding of plant–soil feedbacks and underlying mechanisms is improving our ability to predict consequences of these interactions for plant community composition and productivity under a variety of conditions. Future research will enable better prediction and mitigation of the consequences of human-induced global changes, improve efforts of restoration and conservation and promote sustainable provision of ecosystem services in a rapidly changing world.

PLANT-SOIL FEEDBACKS IN A CHANGING WORLD Plant-soil feedbacks: the past, the present and future challenges

Natural disturbances such as lava flows, landslides and glacial moraines, and human-damaged sites such as pavement, road edges and mine wastes often leave little or no soil or biological legacy. This 2003 book provided the first comprehensive summary of how plant, animal and microbial communities develop under the harsh conditions following such dramatic disturbances. The authors examine the basic principles that determine ecosystem development and apply the general rules to the urgent practical need for promoting the reclamation of damaged lands. Written for ecologists concerned with disturbance, landscape dynamics, restoration, life histories, invasions, modeling, soil formation and community or population dynamics, this book will also serve as an authoritative text for graduate students and a valuable reference for professionals involved in land management.

/pdf/primary-succession-and-ecosystem-rehabilitation-46xfnlnrj7.pdf

Primary Succession and Ecosystem Rehabilitation

In an age of accelerating biodiversity loss, this timely and critical volume summarizes recent advances in biodiversity-ecosystem functioning research and explores the economics of biodiversity and ecosystem services. The book starts by summarizing the development of the basic science and provides a meta-analysis that quantitatively tests several biodiversity and ecosystem functioning hypotheses. It then describes the natural science foundations of biodiversity and ecosystem functioning research including: quantifying functional diversity, the development of the field into a predictive science, the effects of stability and complexity, methods to quantify mechanisms by which diversity affects functioning, the importance of trophic structure, microbial ecology, and spatial dynamics. Finally, the book takes research on biodiversity and ecosystem functioning further than it has ever gone into the human dimension, describing the most pressing environmental challenges that face humanity and the effects of diversity on: climate change mitigation, restoration of degraded habitats, managed ecosystems, pollination, disease, and biological invasions.However, what makes this volume truly unique are the chapters that consider the economic perspective. These include a synthesis of the economics of ecosystem services and biodiversity, and the options open to policy-makers to address the failure of markets to account for the loss of ecosystem services; an examination of the challenges of valuing ecosystem services and, hence, to understanding the human consequences of decisions that neglect these services; and an examination of the ways in which economists are currently incorporating biodiversity and ecosystem functioning research into decision models for the conservation and management of biodiversity. A final section describes new advances in ecoinformatics that will help transform this field into a globally predictive science, and summarizes the advancements and future directions of the field. The ultimate conclusion is that biodiversity is an essential element of any strategy for sustainable development.

Biodiversity, Ecosystem Functioning, and Human Wellbeing: An Ecological and Economic Perspective

Plant roots may be linked by shared or common mycorrhizal networks (CMNs) that constitute pathways for the transfer of resources among plants. The potential for water transfer by such networks was examined by manipulating CMNs independently of plant roots in order to isolate the role(s) of ectomycorrhizal (EM) and arbuscular mycorrhizal fungal (AMF) networks in the plant water balance during drought (soil water potential -5.9 MPa). Fluorescent tracer dyes and deuterium-enriched water were used to follow the pathways of water transfer from coastal live oak seedlings (Quercus agrifolia Nee; colonized by EM and AMF) conducting hydraulic lift (HL) into the roots of water-stressed seedlings connected only by EM (Q. agrifolia) or AMF networks (Q. agrifolia, Eriogonum fasciculatum Benth., Salvia mellifera Greene, Keckiella antirrhinoides Benth). When connected to donor plants by hyphal linkages, deuterium was detected in the transpiration flux of receiver oak plants, and dye-labelled extraradical hyphae, rhizomorphs, mantles, and Hartig nets were observed in receiver EM oak roots, and in AMF hyphae of Salvia. Hyphal labelling was scarce in Eriogonum and Keckiella since these species are less dependent on AMF. The observed patterns of dye distribution also indicated that only a small percentage of mycorrhizal roots and extraradical hyphae were involved with water transfer among plants. Our results suggest that the movement of water by CMNs is potentially important to plant survival during drought, and that the functional ecophysiological traits of individual mycorrhizal fungi may be a component of this mechanism.

Common mycorrhizal networks provide a potential pathway for the transfer of hydraulically lifted water between plants

On the volcanically devastated Pumice Plain of Mount St. Helens, plant species colonized microsites differentially. Peak colonization did not occur in the same microsites as peak establishment and growth. In addition, observed microsite colonization patterns differed between years. Two studies were conducted. The first assessed seedling establishment and growth from seeds sown at different microsites. The second assessed colonization into four microsite types that were constructed on the Pumice Plain. Hypochaeris radicata was the most common species to survive when the same number of seeds of four species were planted; however, Anaphalis margaritacea was the most common colonizer of microsites. Microsites with the largest biomass plants in the first study generally had the highest colonization in the second study. Sites that do not possess features to trap seeds, such as flats and ridges, are not opportune places for a plant to grow since there is little microclimatic or substrate amelioration. Thus, flat microsites had low biomass in the establishment experiment due to the lack of amelioration and contained few plants in the colonization experiment due to a lack of seed trapping mechanisms. These results show that in the primary successional landscape of Mount St. Helens microsites are critical to revegetation dynamics. Changes in the pattern of microsite colonization between years emphasizes the dynamic nature of the landscape and the important influences of climate, substrate amelioration and seed rain to plant establishment.

https://faculty.washington.edu/moral/publications/1998%20Titus%20del%20Moral%20Plant%20Ecology.pdf

Seedling establishment in different microsites on Mount St. Helens, Washington, USA

We examined the factors that control seedling es- tablishment on barren substrates on the pyroclastic flows from Mount St. Helens. From June to September in 1993, we monitored seedling and microhabitat changes in 240 20 cm x 20 cm quadrats on the Pumice Plain. Seedlings emerged in 104 quadrats (43.3 %). The most abundant species were Anaphalis margaritacea, Hypochaeris radicata, Lupinus lepidus and Epilobium angustifolium. Measured site charac- teristics included topography, particle size distribution, ground surface movements, soil water content, organic matter, pH, and presence or absence of dead lupines. Quadrats with seed- lings had higher cover of dead lupines, higher amount of rock and gravel substrate, and a greater cover of rills. More seed- lings emerged where eroded material accumulated. Compared to coarse-textured surfaces, silt surfaces had higher organic matter, held more water, and showed higher pH. However, seedlings became established more frequently on coarse-tex- tured surfaces. In greenhouse experiments, a higher percent- age of Hypochaeris seeds germinated on silt than on sand or gravel. The germination of Anaphalis and Epilobium did not differ with soil texture, but was higher at higher moisture levels. Seedling colonization is more dependent on ground surface microtopography, particle size, and ground movement than on the chemical status of these volcanic deposits.

https://faculty.washington.edu/moral/publications/1997%20Tsuyuzaki%20et%20al.pdf

Seedling establishment patterns on the Pumice Plain, Mount St. Helens, Washington

This study was designed to examine the role of vesicular-arbuscular mycorrhizae (VAM) and microsites on the growth of pioneer species. Flat, rill, near-rock, and dead lupine microsites were created in plots in barren areas of the Pumice Plain of Mount St. Helens. VAM propagules were added to the soil in half of the plots. Six pioneer species were planted into both VAM and non-VAM inoculated microsites. Plants in dead lupine microsites were greater in biomass than those in flat, rill, and near-rock microsites. Significant effects of VAM on plant biomass did not occur. Microsites continue to be important to plant colonization on the Pumice Plain, but VAM do not yet appear to play an important role. This may be due to limited nutrient availability and the facultatively mycotrophic nature of the colonizing plant species. It is unlikely that VAM play an important role in successional processes in newly emplaced nutrient-poor surfaces. In the stressful environments on Mount St. Helens it is known that microsite patterns play a crucial role in plant colonization (del Moral and Bliss, 1993). However, little is known about how vesicular-arbuscular mycorrhizae (VAM) affect primary successional processes on volcanic surfaces. This study was conducted to determine the role of VAM in plant growth on Mount St. Helens and how they may interact with microsites prevalent on barren surfaces. During primary succession on new volcanic substrates, pioneer species are expected to be nonmycorrhizal (Allen 1991). Only nonmycotrophic and facultatively mycorrhizal species usually inhabit these sites. Obligately mycotrophic species would be prevented from establishing in a site until a population of VAM fungi had built up. Thus, the seral sequence could reflect the mycorrhizal dependencies of the colonizing species, and the rate of succession may be related to the increase of mycorrhizal inoculum over time. Species of early-successional stages are nonmycotrophic, followed by facultatively mycotrophic species in the intermediate stages of succession, and obligately mycotrophic species dominate later seral communities (Doerr, Redente, and Reeves 1984; Gange, Brown, and Farmer, 1990; Allen, 1991; Boerner, 1992). Although mycorrhizae are considered to be important determinants of plant successional sequences, our knowledge of their role during early primary succession is scant. Also, the dispersal patterns of mycorrhizal fungi onto barren, new landscapes and the influence these patterns have on initial establishment have received little

https://www.jstor.org/stable/pdfplus/2446330.pdf

The role of mycorrhizal fungi and microsites in primary succession on Mount St. Helens.

The 1980 eruption of Mount St. Helens deposited new substrates upon which wetlands are now developing. We collected soil from five wetlands south of Spirit Lake, Mount St. Helens, Washington, to examine the seed banks. Seedling emergence density in the top 5 cm was highly variable, and ranged from (mean±s.d.) 15,700±15,200 to 38,000±31,500 per m2. Seedling emergence from soil at 5 to 10 cm depth varied from 800±600 to 18,000±24,800 per m2, and averaged 1/3 as many seeds as the surface. The high proportion of buried seeds may be due to continuing deposition of upland sediments. We identified 17 taxa from the wetland soil samples withEpilobium ciliatum, Juncus bufonius, Agrostis exarata andJuncus ensifolius being the dominant species. Wetland vegetation was dominated byEquisetum arvense, Salix sitchensis, Typha latifolia and the four dominant species in the seed bank. Correlations between vegetation and seed bank were not significant for four of the five wetlands, and the dominance byTypha latifolia in two wetlands contributed to the low correlations. Thus, vegetation of these early successional wetlands generally was not similar to seed bank composition. Canonical correspondence analysis was used to relate soil parameters to vegetation and seed bank data. The vegetation was correlated primarily with soil particle size and secondarily to water temperature, while the seed bank was correlated to pH, texture and temperature.

https://faculty.washington.edu/moral/publications/1998%20Tu%20et%20al.pdf

Composition and dynamics of wetland seed banks on Mount St. Helens, Washington, USA

The slopes of Mt Koma in Japan are undergoing primary succession as a result of a 1929 eruption Understory vegetation below a non-native invasive tree species, Larix kaempferi, a native tree, Betula ermanii, and in the open were compared to determine if the non-native tree species was influencing species composition Larix canopies are significantly larger than Betula canopies Vegetation under Larix canopies had significantly greater richness and diversity than vegetation in the open, vegetation under Betula was intermediate but was significantly greater than the open in diversity Vegetation cover was highest under Betula and significantly lower in the open Larix canopy size was positively correlated with size and number of Salix reinii shrubs Betula canopy size was positively correlated with size but not with number of Salix reinii shrubs Species assemblages in the three sites are slightly different as shown by DCA Due to the limited species pool on Mt Koma the greatest possible extent of differences between the three microsites is not large At this point Larix certainly appears to be accelerating succession for the non-tree species If Larix persists on the slopes then succession would be permanently deflected towards a Larix forest This would be a case of succession being deflected towards dominance by the introduced species

Jonathan H. Titus

Papers

Seedling establishment in different microsites on Mount St. Helens, Washington, USA

Seedling establishment patterns on the Pumice Plain, Mount St. Helens, Washington

The role of mycorrhizal fungi and microsites in primary succession on Mount St. Helens.

Composition and dynamics of wetland seed banks on Mount St. Helens, Washington, USA

Influence of a non-native invasive tree on primary succession at Mt. Koma, Hokkaido, Japan