What factors cause grasslands to develop instead of forests?

GRASSLAND SOILS

J.A. Stonemason , C.W. Zanner , in Encyclopedia of Soils in the Environment, 2005

Environment of Pedogenesis in Grasslands

The distinctive characteristics of grassland soils in part reverberate the influence of the climatic conditions under which grassland vegetation predominates. The frequent soil-moisture deficits in many grassland regions inhibit silicate mineral weathering and organic matter oxidation, and favor precipitation of secondary carbonates within the soil profile.

Ecologic processes likewise influence grassland soil development. Net chief productivity (biomass product by photosynthesis minus biomass consumed through respiration by the photosynthesizers themselves) is relatively modest in about grasslands, relative to many forest ecosystems. The total standing biomass in grasslands is also small-scale compared with mature forests. A larger proportion of the total biomass produced by photosynthesis is transferred to institute roots in grasslands than in forests, nevertheless. In many grasslands, underground plant biomass is greater than aboveground biomass, in some cases by a cistron of 5 or more. As a outcome, the fraction of the total organic matter input that is added to the soil belowground is larger in grasslands than in forest, where well-nigh input occurs in the form of surface litter.

Consistent with the relative importance of belowground biomass, burrowing activity by animals appears to be greater in grasslands than in other ecosystems, although the difference is difficult to quantify. In that location are many observations of remarkably all-encompassing burrowing by earthworms, insects (specially ants and cicadas), and rodents in N American and Eurasian grasslands. Termite-burrowing and mound structure is extensive in tropical and subtropical savannas and grasslands.

Geomorphic processes that interact with pedogenesis may besides differ between grasslands and other ecosystems. As noted above, eolian sand and loess deposits are widespread in grassland regions, indicating the potential for by truncation or upbuilding of soil profiles by wind erosion and dust deposition. This potential is quite evident in grass-covered dune fields, where excavations normally reveal multiple buried soils. The potential for reworking of soil material past slopewash is also higher in most grasslands than in forest.

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Sustainable direction of grassland soils

1000.J. McTavish , ... E.J. Sayer , in Soils and Landscape Restoration, 2021

4.2 Threats to grassland soils and management challenges

Grassland soils are threatened by several, primarily anthropogenic, factors that have contributed to their historical, present day, and potential future deposition and disappearance. We accept summarized three of the primary threats to grassland soils:

one.

Land-utilise alter:

Amid global biomes, temperate grasslands, savannas, and shrublands have the greatest disparity betwixt the amount of land use (c. 46%) and extent of habitat protection (c. 4.6%), and many global grasslands have been heavily modified and converted for human purposes (Hoekstra et al., 2005).

The primary anthropogenic utilise of grasslands is nutrient production; grasslands have been exploited throughout human history for hunting and gathering, herding and grazing of livestock, and sedentary agriculture (Ramankutty et al., 2008; Suttie et al., 2005; White et al., 2000). Grasslands are integral to electric current global nutrient security and will be nether increasing force per unit area as human populations continue to grow (O'Mara, 2012). In improver to providing food, grasslands are a user-friendly source of fuel and building materials and are relatively easy to develop. Equally a result, grasslands have been heavily developed for human settlement; approximately twice every bit many people are estimated to alive on erstwhile grasslands compared to forests (White et al., 2000) (Fig. 4.one).

Figure 4.ane. Black-faced sheep grazing in the Scottish Highlands. Scotland's upland grasslands are idea to cover less than ane% of the country's land area.

Photo: H. Cray.

Unfortunately, this preferential exploitation of grasslands contributes to their continuing degradation and disappearance. The development of agriculture or settlement removes whole grassland habitats. Harvesting of constitute biomass (e.1000., animal forage, biofuel feedstock) or grazing animals (due east.g., meat, milk) tin can negatively impact soil carbon stocks and consign other essential nutrients from the landscape. Intensive cultivation through tillage, grazing, or harvesting can besides disrupt soil physical and chemical processes, breaking downwardly soil structure and aggregates, exposing previously less accessible carbon species to microbial decomposition, and altering the multifariousness of soil biotic communities (Frey et al., 1999; Menta et al., 2011).

two.

Climatic change:

Anthropogenic climate change is a complex ecology claiming that threatens grassland soils through warming temperatures, atmospheric carbon dioxide (CO_two) enrichment, and changes in the intensity and frequency of rainfall and fires (Pachauri and Mayer, 2014).

Warming temperatures generally increase rates of organic affair decomposition and soil respiration leading to higher net losses of soil carbon (Rey et al., 2011; Schuerings et al., 2013; Wang and Fang, 2009), though these furnishings are non universal (Stiff et al., 2017). Atmospheric CO₂ enrichment in grasslands can enhance institute growth just may also stimulate increased heterotrophic denitrification in the underlying soils through higher root turnover, raising emissions of the strong and long-lived greenhouse gas nitrous oxide (N₂O) (Niboyet et al., 2011). Drought or irregular rainfall can reduce aboveground productivity (Felton et al., 2020) but may as well increment carbon storage every bit microbial decomposition is reduced and plants allocate increasing biomass to roots (Martí-Roura et al., 2011), while college intensity rainfall may alter soil hydraulic properties (Caplan et al., 2019) and variably increment the release or storage of carbon from water-stressed and wetter systems, respectively (Vargas et al., 2012; Wang and Fang, 2009). Higher intensity and more frequent fires could release large amounts of both carbon and nitrogen, only the incorporation of remaining ash and expressionless organic matter to the soil may too increment plant growth and carbon storage (Martí-Roura et al., 2011).

Overall, these diverse potential climate change impacts interact to produce circuitous trade-offs between higher rates of both decomposition and cyberspace primary product (NPP), leaving researchers in agreement that climate change could accept stiff impacts on grasslands but uncertain whether it will increment or decrease carbon storage in grassland soils (Jones and Donnelly, 2004). Climate change is also expected to have other poorly understood furnishings on grassland plant litter quality, soil organisms, soil structure, and nutrient cycling (Barnett and Facey, 2016; Walter et al., 2013).

3.

Woody encroachment and biological invasion:

Grassland soils and soil biota are also contradistinct by changes in the aboveground establish community (Hedlund et al., 2003; Virágh et al., 2011). Changes in vegetation can create contest with desired plant species for light and soil resources (Hautier et al., 2009; Sperry et al., 2006; Zhang et al., 2014); alter burn regimes (Vasquez et al., 2008); and alter the quality, quantity, and timing of organic inputs through the soil from roots and litter (Reed et al., 2005). The two primary sources of changing vegetation in grasslands are woody encroachment and the invasion of exotic forbs or grasses.

Woody inroad is one of the main challenges facing global grasslands and is generally a result of changes in disturbance regimes, including anthropogenic burn suppression, loss of grazing herbivores, or even overgrazing that disrupts fuel and fire connectivity (Archer et al., 2017; Case and Staver, 2017; Daskin et al., 2016; Joubert et al., 2012). These changes in disturbance authorities let woody vegetation (native or exotic) from contiguous habitat to constitute and spread, mostly decreasing grassland plant diversity (Ratajczak et al., 2012). Although woody encroachment may or may not back up higher rates of carbon sequestration on an ecosystem scale (Smith and Johnson, 2003), encroachment can also result in increased fluxes of trace gases (due east.g., NO _ten ), greater susceptibility to higher severity wildfires, and loss of grassland ecosystem traits (Liao et al., 2006; Liao and Boutton, 2008; Porqueddu et al., 2016).

Although the study of biological invasions and the implications of exotic species for conservation have been the subjects of extensive and ongoing debate (run across Chew, 2015; Crowley et al., 2017; Guerin et al., 2018; Kuebbing and Nuñez, 2018; Russell and Blackburn, 2017), it is clear that the introduction of exotic species tin can crusade ecological changes that are both difficult to predict and frequently undesirable (Jeschke et al., 2014; Mack et al., 2000). Considering grassland vegetation community structure is often strongly driven by disturbance and contest for fundamental limiting nutrients (e.grand., N), altered disturbance regimes or higher nutrient loading from sources such as fertilization or atmospheric deposition tin can provide a competitive reward to exotic species over locally adapted taxa (Sperry et al., 2006; Vasquez et al., 2008). Grasslands worldwide have been invaded by many exotic species such as Cheatgrass (Bromus tectorum) in the arid and semiarid rangelands of the western US steppe (Sperry et al., 2006; Vasquez et al., 2008), alligator weed (Alternanthera philoxeroides) in Chinese annual grasslands (Zhang et al., 2014), and South African Lovegrass (Eragrostis plana) in the Pampas grasslands of southern Brazil, Uruguay, and Argentina (Fonseca et al., 2013). In addition to changing the aboveground vegetation community, these exotic species can alter many belowground properties and processes, including soil carbon storage, food cycling, soil structure, hydrology, and flora and faunal variety.

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Nitrogen Dynamics in Grasslands

P.K. Ghosh , ... S.N. Ram , in The Indian Nitrogen Cess, 2017

Grassland Nitrogen: Uptake of N

Grassland soils receive nitrate and/or ammonium ions through the application of fertilizer. Nevertheless, the ii ions differ in the reactions they undergo in the soil, and in the mechanisms by which they are taken up past plants roots. Nitrate is not adsorbed past the colloidal material (clay and organic mattes) in the soil and is therefore mobile in the soil solution, readily attainable to plant roots but also susceptible to leaching and dentrification. On the contrary, ammonium is retained past cation exchange on the clay and organic affair. Thus it is less mobile than nitrate, less attainable to roots, and less susceptible to loss. Ammonium, although, is converted slowly to nitrate by nitrification procedure. In the soil, nitrate moves mainly past mass flow with the movement of h2o and partly by diffusion, whereas ammonium moves mainly past diffusion and merely slightly by mass flow ( Fig. xiii.1) (Whitehead, 1995). When plants were grown in solution civilisation it was observed that both ammonium and nitrate ions are utilized simply usually plants accept upwardly nitrate rather more readily than ammonium, and show greater growth responses to nitrate. Grasses, however, often show a greater uptake of ammonium than of nitrate when the 2 ions are supplied in equal amounts. Again the charge per unit of uptake of both nitrate and ammonium by roots is influenced by temperature and pH, but differently for the two ions. Studies with perennial ryegrass in solution culture indicated that absorption of nitrate increased with increasing temperature over the range of five–35°C and was highest at pH 6.2, while assimilation of ammonium was highest at a temperature of nearly 22°C and was only slightly influenced by pH over the range 4.0–7.5. In another study with perennial ryegrass grown in nutrient solution containing NH₄NO_iii, the proportion taken up as ammonium was always greater than that of nitrate merely was inversely related to root temperature, declining from 93% equally ammonium at iii°C to 65% at 25°C. Other establish species had a smaller effect of temperature on the ratio between ammonium and nitrate uptakes. Thus grasses also blot a considerable quantity of N in the form of nitrate, but it is reduced by the institute in order to be alloyed.

Figure 13.1. Transformations of nitrogen in a grassland organization (Whitehead, 1995).

In grasslands, the almanac uptake of nitrogen was reported to vary based on ecoclimatic zones, beingness maximum, on an average, in a dry subhumid zone (25.58   g/kⁱⁱ) and minimum in a semiarid zone (2.93   g/one thousand²). Information technology was observed that 53–66% uptake of nitrogen is retained in the underground net production in semiarid and humid grasslands, while 53–73% of the full uptake is associated with the above ground internet production in subhumid and dry subhumid grasslands. Thus recycling of N was promoted through underground parts in semiarid and boiling climatic conditions. The proportion of N absorbed by vegetation that is afterward returned to the soil ranged from 63% to 78%, being comparatively college in humid and semiarid grasslands than in the zones of intermediate moisture supply. Again, it was reported that the rate of Northward uptake by plants is highest in the rainy season in all the climatic zones except the boiling zone and ranged from 56% of the annual transfer in dry subhumid grasslands to 71% in the semiarid zone. Nevertheless, the charge per unit of release back to the soil is greatest during winter, when from 47% to 64% of this transfer takes identify (Coupland, 1979).

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Evolution of the Earth

G.J. Retallack , in Treatise on Geophysics (2d Edition), 2015

9.ten.3.9 Mollic Epipedon

The mollic epipedon is a unique surface horizon of grassland soils (Mollisols), which presents a number of paradoxes. It is rich in base-rich clay such as smectite yet does not ball up or shear into unwieldy clods and flakes. It is rich in organic affair still well aerated with cracks and channels in which organic matter should be oxidized. It tin can exist well tuckered still still maintains soil moisture. Information technology is fertile with phosphorus and other mineral nutrients despite long periods (thousands of years) of soil development. Mollic epipedons achieve these highly desirable agricultural qualities through a unique construction of fine (2–3  mm) ellipsoidal (crumb) clods (peds), which consist of clay stabilized by organic matter. The geologically oldest fossilized mollic epipedons are Early Miocene (19   Ma) and known from the Anderson Ranch Formation, near Agate, Nebraska, and the upper John Day Formation, near Kimberly, Oregon, the Usa (Retallack, 2004b). Zilch similar a mollic epipedon has been reported from the Moon, Venus, Mars, or meteorites.

The temporal range and micromorphology of mollic epipedons suggest that they are created by grassland ecosystems. Some of the rounded nibble peds are excrements of earthworms common in these soils; other peds are products of the three-dimensional network of the slender adventitious roots of sod-forming grasses (Retallack, 2001a). The organic matter is partly from root exudates and earthworm slimes, simply block-like dung of large ungulates also plays a role in soil conditioning. The mollic epipedon can be considered a trace fossil of sod-grassland ecosystems, even afterwards destruction by desertification or burying (Retallack, 2004b).

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Surface and Footing Water, Weathering, and Soils

R. Amundson , in Treatise on Geochemistry, 2003

5.01.5.1.one Modeling carbon movement into soils

The soil carbon mass remainder is hypothesized to be, for grassland soils, a function of plant inputs (both surface and root), transport, and decomposition:

(10) $\frac{\text{d}C}{\text{d}t}=\underset{\text{downwardadvectivetransport}}{\underbrace{‐5\frac{\text{d}C}{\text{d}z}}}-\underset{\text{decomposition}}{\underbrace{kC}}+\underset{\text{plantinputsdistributedexponentially}}{\underbrace{\frac{F}{L}{\text{east}}^{‐z/\mathrm{Fifty}}}}$

where −ν is the advection rate (cm   yr⁻¹), z the soil depth (cm), F the total plant carbon inputs (g   cm^−twoyr⁻¹), and L the due east-folding depth (cm). For the boundary conditions that C=0 at z=∞ and −ν(dC/dz)=F _A at z=0 (where F _A are aboveground and F_B the belowground found carbon inputs), the steady-land solution is

(11) $C\left(z\right)=\underset{\text{above}\text{–}\text{groundinput}/\text{transport}}{\underbrace{\frac{F_{\text{A}}}{\mathrm{five}}{\text{e}}^{‐\mathrm{chiliad}z/v}}}+\underset{\text{root input}/\text{send}}{\underbrace{\frac{F_{\text{B}}}{\mathrm{one\; thousand}L‐v}{\text{e}}^{‐kz/v}\left({\text{e}}^{z\left(kL‐v\right)/vL}‐1\right)}}$

This model forms the framework for examining soil carbon distribution with depth. Information technology contains numerous simplifications of soil processes such equally steady state, constant advection and decomposition rates versus depth, and the supposition of one soil carbon puddle. Recent enquiry on soil carbon cycling, particularly using ^fourteenC, has revealed that soil carbon consists of multiple pools of differing residence times (Trumbore, 2000). Therefore, in modeling grassland soils in California, Baisden et al. (2002) modified the soil carbon model above past developing linked mass residue models for three carbon pools of increasing residence time. Estimates of carbon input parameters came from direct surface and root production measurements. Estimates of transport velocities came from ¹⁴C measurements of soil carbon versus depth, and other parameters were estimated by iterative processes. The result of this try for a $\sim$ 2×10⁵  twelvemonth former soil (granitic alluvium) in the San Joaquin Valley of California is illustrated in Effigy 15. The goodness of fit suggests that the model captures at least the cardinal processes distributing carbon in this soil. Model plumbing equipment to observed data became more hard in older soils with dumbo or cemented soil horizons, presumably due to changes in send velocities versus depth (Baisden et al., 2002).

Figure fifteen. Measured total organic C versus depth and modeled amounts of 3 fractions of differing residence time (∼10⁰  year, ten^two  yr, and x³  yr) for a ∼600   ka soil formed on granitic alluvium in the San Jaoquin Valley of California (source Baisden, 2000).

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Perspectives for Agronomy

Konrad Mengel , in Developments in Crop Scientific discipline, 1997

4 Organic phosphate and mycorrhiza in soil cropping systems

In arable state the concentration of organic phosphate is in the gild of 50% of total phosphate in the upper soil layer and in grassland soils the proportion of organic phosphate may be fifty-fifty higher ( Sharpley, 1985). A substantial function of organic phosphate, up to 100 kg P/ha, may be stock-still in microbial biomass (Brookes et al., 1984). Phosphate thus immobilized may easily be mineralized and hence become available for crops. Sharpley (1985) reported that in that location is a seasonal variation in available organic soil phosphate decreasing in spring with crop growth and increasing in late autumn and wintertime. This pattern was peculiarly singled-out in soils not treated with inorganic phosphate fertilizer showing that the plants drew phosphate from this organic pool. In calcareous soils, the phosphate of the soil solution is mainly present in organic form (Dalal, 1977) and therefore in these soils phosphate transport to constitute roots is mainly brought near by organic phosphates which may exist easily mineralized in the plant rhizosphere enriched with phosphatases (Tarafdar and Claassen, 1988; Dou and Steffens, 1993). Nigh half of the organic phosphates in soils is nowadays as myo-inositol-phosphates from which the inositol-hexaphosphate is adsorbed to sequioxides similar every bit inorganic phosphate (Dalal, 1977). The adsorption of inositol-hexaphosphate is relatively stiff since the molecule has half dozen phosphate groups which may exist spring to soil particles. Diminishing the numbers of phosphate groups bound to inositol decreases the possibility of phosphate adsorption and thus improves phosphate availability (Evans, 1985). Myo-inositol-2-monophosphate is virtually not adsorbed (Evans, 1985), and quite mobile in soils (Dou and Steffens, 1993). In addition inositol-hexaphosphate tin also course rather insoluble salts with Ca^{2   +} and Mg^{2   +}, a process which may affect phosphate availability. Other organic phosphates such as phospholipids and nucleotide phosphates practice not accrue in soils as they are easily mineralized (Dalal, 1977; Tarafdar and Claassen, 1988). Hence the large pool of organic soil phosphate is potentially available for plants. This is as well true for the non-soluble organic phosphate from which a keen office is present in the class of microbial biomass and which will exist mineralized afterward the death of microorganisms. Therefore, in contrast to the fixed inorganic phosphate the immobilized organic phosphate represents a potential puddle of available phosphate and measures which promote the formation of organic phosphate in soils and may restrict the fixation of inorganic phosphate and thus contribute to an efficient use of soil phosphates.

Sources of organic phosphates in soils are plant residues, green manure, microbial biomass, and farm g manure (FYM). For this reason cropping systems have a distinct touch on on the content of organic phosphates in soils besides as on the assimilation of inorganic phosphates by fungi and bacteria and the mineralization of organic phosphates past phosphatases. Oberson et al., 1993, 1996; reported that regular application of FYM to soil increased the organic phosphate content. This effect may be due to organic phosphate present in the FYM but also to inorganic phosphate existence assimilated by soil microorganisms after FYM awarding. The latter especially raised the ATP concentration which, co-ordinate to the authors means an increment in microbial biomass. The affect of FYM on the concentration of ATP in the upper soil layer is shown in Table 3, from the piece of work of Oberson et al. (1993). It is evident that in all treatments receiving FYM the ATP concentration was significantly increased which means that FYM had a benign effect on microbial biomass development and hence on the storage of potentially bachelor phosphate. Parallel with the increase of microbial biomass the acrid phosphatase activity was increased past FYM application which means that also the enzyme activity rendering organic phosphate into a form directly taken up by establish roots was promoted. The positive outcome of FYM on the efficient use of soil and fertilizer phosphate availability is enhanced by organic anions produced during the decomposition of organic matter. They compete with inorganic phosphate for adsorption sites and thus reduce the fixation of phosphate (Werner and Scherer, 1995). In addition FYM may improve soil structure and favor root growth and thus the exploitation of soil phosphates by roots (Keita and Steffens, 1989). Farms producing FYM frequently also grow arable forage crops such as crimson clover and alfalfa which not only contribute to the nitrogen status of soils by symbiotic N_ii fixation just they as well may exploit fixed soil phosphate past the excretion of root exudates as was shown for red clover excreting citrate which mobilizes adsorbed soil phosphate (Gerke, 1994). Rotations with diverse crop species more often than not will contribute to a improve exploitation of soil phosphates. Mycorrhization of plant roots may considerably improve the accessibility of soil phosphate to plants mainly by increasing the contact surface betwixt the soil matrix and the mycorrhized plant root. This is particularly truthful for leguminous species (Barea and Acon-Aguilar, 1983). The problem with mycorrhiza exploiting soil phosphate for the host plant is the high specificity between the host plant and the endomycorrhizal fungi (Lioi and Giovannetti, 1987; Diederichs, 1991). Inoculation of soils with the appropriate fungi still meets with difficulty (Hall, 1987). If the fungi/root symbiosis is efficient remarkable crop yield increases may be obtained due to a amend exploitation of soil phosphate (Hall, 1984).

Table iii. Effect of FYM on the ATP concentration in soils. Soil samples taken at ear emergence of wintertime wheat (Oberson et al., 1993)

P fertilizer kg P/ha	Rate of P appl. kg P/ha per year	ATP μg/kg soil*
No	–	843a
FYM	28	1217c
80% FYM + 20%	31	1160bc
mineral P
40% FYM + threescore%	47	1006abc
@@@mineral P
100% mineral P	46	945ab

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Free-Air CO2 Enrichment: Responses of Cotton and Wheat Crops

Paul J. PinterJr., ... Robert Fifty. LaMorte , in Carbon Dioxide and Terrestrial Ecosystems, 1996

Acknowledgments

This research was supported by the Agricultural Enquiry Service, U. S. Department of Agriculture, including the U. South. H2o Conservation Laboratory (Phoenix, AZ), the Grassland Soil and H2o Research Laboratory (Temple, TX), and the Plant Stress and Protection Group (Gainesville, FL). It has besides been partially supported by the Carbon Dioxide Research Programme of the U. S. Section of Free energy, Environmental Sciences Sectionalisation. Contributions toward operational support were made by the Potsdam Institute for Climate Impact Research (Potsdam, Germany), the NASA Goddard Space Flight Eye (Greenbelt, Physician), the Natural Resource Environmental Laboratory at Colorado Country University (Ft. Collins, CO), and the Section of Soil Science, University of Alberta (Edmonton, Alberta, Canada). We also acknowledge the helpful cooperation of Dr. Roy Rauschkolb and his staff at the University of Arizona, Maricopa Agricultural Eye. The FACE apparatus was furnished by Brookhaven National Laboratory, and we are grateful to Mr. Keith Lewin, Dr. John Nagy, and Dr. George Hendrey for their engineering science expertise. This work contributes to the Global Change Terrestrial Ecosystem (GCTE) Core Research Programme, which is role of the International Geosphere Biosphere Programme (IGBP). We capeesh the specialized communication provided past the many scientists and graduate students listed in the Appendix and the technical assist of Grand. Baker, T. Brooks, O. Cole, G. Gerle, D. Johnson, C. O'Brien, L. Olivieri, J. Olivieri, R. Osterlind, R. Rokey, R. Seay, L. Smith, S. Smith, and Thou. West. Dr. Gary Richardson, ARS biometrician, provided valuable assist in the statistical assay of the data.

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Biogeographical patterns in myxomycetes

Martin Schnittler , ... Yuri Grand. Novozhilov , in Myxomycetes (Second Edition), 2022

Steppes and prairie

At a kickoff glance, due to a lack of woody debris, grasslands would not seem to provide good habitats for myxomycetes, despite evidence from studies showing that amoeboflagellates are more than mutual in grassland soils than in wood soils ( Feest and Madelin, 1988). However, studies carried out in the steppe regions of Russia (Novozhilov et al., 2010, 2006), Mongolia (Novozhilov and Schnittler, 2008), Kazakhstan (Zemlyanskaya et al., 2020), and the midwestern United States (Rollins and Stephenson, 2013) reported a surprisingly loftier multifariousness of myxomycetes. Recently, Fiore-Donno et al. (2016) analyzed soil samples from a temperate grassland in Frg by ePCR and institute that the most abundant OTUs belonged to the genera Lamproderma and Didymium. A special assemblage of species in grasslands often abundantly grazed past herbivores such as horses and cattle includes coprophilous species (Eliasson and Lundqvist, 1979). Typical examples include Kelleromyxa fimicola and Perichaena liceoides associated with dung and D. squamulosum, Echinostelium minutum, Fuligo cinerea, and P. pseudonotabile (Novozhilov et al., 2013b) that are associated with grass litter.

At the grassland–forest transition zone, species diversity tends to increment toward the latter. Looking at the species/genus ratio, Rollins and Stephenson (2013) found a tendency of increasing taxonomic diversity moving eastward from short to tall grass prairie. In the Russian Altay (Novozhilov et al., 2010) a pronounced trend of increasing species richness was found when moving from dry steppe (half-dozen species, H′=1.half-dozen) over nighttime coniferous taiga and secondary mixed aspen and birch forests (99 species, H′=four.1) to mixed forests (116 species, H′=four.two); diversity decreased again toward the forest-steppe zone (65 species, H′=3.7). Overall species dominance in the treeless dry out steppe was found to be higher (D=0.26) when compared to the forest steppe, where lignicolous myxomycetes occur in forest islands most streams (D=0.05). Equally would be expected, the occurrence of woody debris causes pronounced differences between the assemblages of myxomycetes associated with open grasslands and adjacent gallery forests (Rollins and Stephenson, 2013).

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Volume 3

Javier Loidi , ... John Janssen , in Encyclopedia of the World'due south Biomes, 2020

Fauna

For creature species most heathlands are an extreme and dynamic environs, with potent fluctuations in temperature and water supply and limited availability of nutrients. The larger fauna commonly operates on a landscape scale, and characteristic species in heathlands may prefer mosaics with open soil, grassland, tall-herb vegetation and forest. Typical birds related to such heathland landscapes are among others Black Grouse (Tetrao tetrix), Common Stonechat (Saxicola rubicola), Dartford Warbler (Sylvia undata), European Curlew (Numenius arquata), European Aureate Plover (Pluvialis apricaria), Northern Wheatear (Oenanthe oenanthe), Whinchat (Saxicola rubetra) and Woods lark (Lullula arborea). The European Nightjar (Caprimulgus europaeus) is a ground breeder of the transition zone between woods and heathlands. Smaller animals often adopt a mosaic of different vegetation structures within the heathlands, and in many cases they crave unlike (micro)habitats in different life stages. Typical reptiles are amongst others Slowworm (Anguis fragilis), Viviparous lizard (Zootoca vivipara), Sand lizard (Lacerta agilis), Smooth snake (Coronella austriaca), and in wet heathland Common European viper (Vipera berus). Amphibians are always related to wet heathlands or fens inside the heathland landscape, including the Moor frog (Rana arvalis) and Natterjack Toad (Epidalea calamita).

The highest diversity of insects seems to exist related with diverseness in vegetation construction rather than in species diversity (Conductor, 1992; Stuijfzand et al., 2004), although some species depend on i plant species or genus in their larval stage. Many butterflies, spiders, grasshoppers, beetles, wasps, bees and ants have concentrations of their distribution in heathland areas. Some examples are the butterflies Silver-studded Blue (Plebejus argus), Green Hairstreak (Callophrys rubi), Grayling (Hipparchia semele), Argent-spotted Skipper (Hesperia comma), Tree Grayling (Hipparchia statilinus), Grizzled Skipper (Pyrgus malvae) and—characteristic for moisture heathlands—Alcon Blueish (Phengaris alcon), which larvae live on Gentiana pneumonanthe. In the Alps Asian Fritillary (Hypodryas intermedia) is characteristic, while in subalpine and boreal heathlands Cranberry blueish (Plebeius optilete) is a typical butterfly species. Among the grasshoppers we mention Wart-biter (Decticus verrucivorus), Heath-bush Cricket (Gampsocleis glabra), Blue-winged Grasshopper (Oedipoda caerulescens) and the Field Cricket (Gryllus campestris). It is also worth mentioning the ground protrude Callisthenes reticulatus which lives in the west European heathlands. A last species that should be mentioned in detail is the Heather Beetle (Lochmaea suturalis). Both larvae and adults swallow heather (leaves, stem apices and bark) and cause regular outbreaks that may destroy entire dry heath patches (Gillingham et al., 2015). The beetle occurs in the dry Calluna dominated heaths of Western Europe.

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Associative Nitrogen Fixation

Anne Van Dommelen , Jos Vanderleyden , in Biology of the Nitrogen Wheel, 2007

12.3.5 Klebsiella

Klebsiella can frequently be isolated from the root surfaces of various plants. K. pneumoniae, K. oxytoca and K. planticola are all capable of fixing Northward₂ and are classified as associative N₂ fixers. Isolations of N₂-fixing Klebsiella were reported from rice leaves, rhizosphere, grassland soil, sweet irish potato [ xxx], [31]. The Klebsiella-type strain, Yard. pneumoniae, is a model organisation in Due north₂ fixation, but other strains of this same species are feared pathogens. Institute-growth-promoting strains of G. pneumoniae are able to colonize the rhizosphere and interior of seedlings of legumes like alfalfa (Medicago sativa) and Medicago truncatula, merely colonize Arabidopsis thaliana, wheat (Triticum aestivum) and rice (Oryza sativa) in much college numbers [32].

K. pneumoniae was shown to set Due north₂, relieve N-deficiency symptoms and increase total Due north and N concentration in wheat (Triticum aestivum L.). N derived from N₂ fixation was found in plant tissues and in chlorophyll, every bit shown past the ¹⁵N isotope dilution technique. Nitrogenase reductase is produced in the intercellular space of the root cortex. The Northward₂-fixation phenotype is dependent on the wheat cultivar [33]. For maize, One thousand. pneumoniae was not capable of relieving the North-deficiency symptoms of non-fertilized maize in either the field or the greenhouse, although the yield of N-fertilized maize was significantly enhanced [34].

Although K. pneumoniae was found to reside in the intercortical layers of the stem and in the root of maize, nitrogenase reductase was but found in the roots when the leaner were supplied with an exogenous C-source, as shown by immunolocalization with an antibody against purified nitrogenase reductase [35].

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