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\"Prepare to set aside what you think you know about yourself and microbes. Good health--for people and for plants--depends on Earth's smallest creatures. [This book] tells the story of our tangled relationship with microbes and their potential to revolutionize agriculture and medicine, from garden to gut\"--Dust jacket flap.

— The history of the development of the concept of urban soil services, their current list, anthropocentric and pedocentric approaches to their assessment, and experience of application in various cities are considered. At present, the concept of ecosystem services is a comprehensive tool that allows, by analogy, to translate soil information into the sphere of management decision-making, as well as to maintain the sustainability of urban ecosystems by introducing measures to preserve urban soil services. Despite the accumulated experience in methods for assessing ecosystem services and examples of their application in urban planning in individual cities, there is no unified approach to assessing the services of urban soils. The widespread application of this concept is often hampered by insufficient knowledge of the properties of urban soils with their high spatiotemporal variability, as well as by the insufficient development of the approach itself for assessing soil services. However, the active development of theoretical and practical approaches to integrating information about soil characteristics into management is a prerequisite for optimizing the system of soil resource management in cities and towns.

1 Root competition is defined as a reduction in the availability of a soil resource to roots that is caused by other roots. Resource availability to competitors can be affected through resource depletion (scramble competition) and by mechanisms that inhibit access of other roots to resources (contest competition, such as allelopathy). 2 It has been proposed that soil heterogeneity can cause size-asymmetric root competition. Support for this hypothesis is limited and contradictory, possibly because resource uptake is affected more by the amount and spatial distribution of resource-acquiring organs, relative to the spatial distribution of resources, than by root system size per se. 3 Root competition intensity between individual plants generally decreases as resource availability (but not necessarily habitat productivity) increases, but the importance of root competition relative to other factors that structure communities may increase with resource availability. 4 Soil organisms play important, and often species-specific, roles in root interactions. 5 The findings that some roots can detect other roots, or inert objects, before they are contacted and can distinguish between self and non-self roots create experimental challenges for those attempting to untangle the effects of self/non-self root recognition, self-inhibition and root segregation or proliferation in response to competition. Recent studies suggesting that root competition may represent a 'tragedy-of-the-commons' may have failed to account for this complexity. 6 Theories about potential effects of root competition on plant diversity (and vice versa) appear to be ahead of the experimental evidence, with only one study documenting different effects of root competition on plant diversity under different levels of resource availability. 7 Roots can interact with their biotic and abiotic environments using a large variety of often species-specific mechanisms, far beyond the traditional view that plants interact mainly through resource depletion. Research on root interactions between exotic invasives and native species holds great promise for a better understanding of the way in which root competition may affect community structure and plant diversity, and may create new insights into coevolution of plants, their competitors and the soil community.

The soil characteristics are critical for crop health and its yield and therefore for agriculture. The soil properties are spatially variable and therefore soil resources should be managed as per location-specific requirements. An integrated spatial analysis of the soil resources of Mewat district was conducted to identify the soil resource management zones to develop site-specific soil management plan which might lead to sustained and enhanced crop yield. Spatial analysis of soil resources was conducted by modeling soil fertility and erosion which determines the crop productivity in the region. Soil fertility of the region was modeled using weighted overlay approach using 10 soil parameters, namely nitrogen, phosphorus, potassium, sulfur, iron, zinc, manganese, organic carbon, electrical conductivity, and pH. Each parameter was assigned weights based on their relative importance to agricultural productivity. The modeled soil fertility was classified into three fertility zones, low, medium, and high. Soil fertility was found to be low to moderate in 65% of the area, largely because of the low nitrogen, soil organic carbon, phosphorus concentration, and excessive salinity. Soil erosion was modeled using the universal soil loss equation (USLE) model by estimating rainfall erosivity factor (R), the soil erodibility factor (K), the topographic factors (L and S), cropping factor (C), and the conservation practice factor (P). Soil erosion problems were limited to areas having high elevation with barren land and areas with minimal management practices. The severity of soil erosion was found high in 15% of the region, while the remaining 85% showed low to moderate erosion. Soil fertility and erosion were integrated using the multivariate clustering method to identify soil management zones. The region was delineated into three soil management zones. Zone I (29%) which covers majorly Tarou block, was characterized by high soil fertility and low soil erosion. Zone II (18%) with medium soil fertility and high erosion covers villages of Taoru, Nuh, Nagina, FP Jhirka, and Punhana, which are located in the foothills of Aravalli ranges. Zone III represents the major part of the region, covering Nuh, Nagina, and FP Jhirka blocks (54%) with low soil fertility and erosion conditions. Thus, within the study area, the soil management domains are spatially variable in terms of fertility and soil erosion, and thus zone-specific soil management measures are required to improve the soil condition in order to sustain and improve agriculture production. The study would help the policy makers to design site-specific planning for identified soil resource management zones.

Background, Aim and Scope Historically, built areas were ignored in soil mapping and in studies of soil formation and behaviour. It is now recognized that these areas, and therefore their soils, are of prime importance to human populations. Another trend is the large increase in reclaimed lands and new uses for old industrial areas. In several countries there are active projects to map such areas, either with locally-developed classification systems or ad-hoc names. Soil classification gives unique and reproducible names to soil individuals, thereby facilitating correlation of soil studies; this should be possible also for urban soils. The World Reference Base for Soil Resources (WRB) is the soil classification system endorsed by the International Union of Soil Science (IUSS). The 2006 edition has important enhancements which allow urban and industrial soils to be described and mapped, most notably a new reference group, the Technosols. Main Features Urban soils are first defined, followed by the philosophical basis of soil classification in general and the WRB in particular. WRB 2006 added a new Technosols reference soil group for soils whose properties and function are dominated by technical human activity as evidenced by either a substantial presence of artefacts, or a impermeable constructed geomembrane, or technic hard rock. Technosols are one of Ekranic, Linic, Urbic, Spolic or Garbic; further qualifiers are added to show intergrades to other groups as well as specific soil properties. Soils from fill are recognized as Transportic Regosols or Arenosols. Toxic soils are specifically recognized by a qualifier. Results - Discussion The limit between Technosols and other groups may be difficult to determine, because of the requirement that the technic nature dominate any subsequent pedogenesis. Conclusions - Perspectives The WRB should certainly be used in all urban soil studies to facilitate communication and correlation of results. In the period leading up to the next revision in 2010, the quantitative results from urban soil studies should be used to refine class definitions.

Background and aims The encroachment of halophytic shrubs including tamarisk into saline meadows is accelerating with global warming in the northern Tarim Basin, Xinjiang, China. However, the role of tamarisk in the spatial heterogeneity of soil resources in different desertification stages remains unclear. Methods The influences of tamarisk on soil resources were assessed via soil salinity and soil organic matter (SOM) measurements under tamarisk canopies and in interspaces. Geostatistical methods were applied to compare the spatial heterogeneity of these soil properties in three regions representing different desertification stages: 1) a meadow with shrubs, 2) a shrubland and 3) shrub duneland. Results The highest coefficient of variation (CVs) of the soil analytes and most developed \"resource islands\" were observed in the shrubland. The overall variation of most of the soil variables was lower in the shrub duneland than in the shrubland and similar to that in the meadow with shrubs. The distribution of SOM and most soil salinity ions were moderately spatially dependent in the meadow with shrubs but highly spatially dependent in the shrubland and shrub duneland. The autocorrelation distances of the most of soil salinity ions were approximately 6- to 15- fold and 2- to 4-fold highest than the tamarisk shrub size in the meadow with shrubs and shrubland, respectively. In contrast, the distribution range of total soil salinity (TSS) and soil K+, Na+ and Cl− in the shrub duneland were 1/5 ∼ 2/3 of the tamarisk size. Conclusions 1 ) Compared with the effect of tamarisk on soil resource heterogeneity in the meadow with shrubs, that in the shrubland was enhanced due to the larger shrub size and more open and scattered canopy in the latter.2) Although the largest shrub size were observed in the shrub duneland, the role of tamarisk in redistributing soil resources was overriden by those of physical processes due to the loose canopy. 3) The spatial heterogeneity of soil resources is determined by not only tamarisk but also environmental factors, such as the connectivity of bare areas and topography.

Resource availability and heterogeneity are recognized as two essential environmental aspects to determine species diversity and community abundance. However, how soil resource availability and heterogeneity determine species diversity and community abundance in highly heterogeneous and most fragile karst landscapes is largely unknown. We examined the effects of soil resource availability and heterogeneity on plant community composition and quantified their relative contribution by variation partitioning. Then, a structural equation model (SEM) was used to further disentangle the multiple direct and indirect effects of soil resource availability on plant community composition. Species diversity was significantly influenced by the soil resource availability in shrubland and woodland but not by the heterogeneity in woodland. Abundance was significantly affected by both soil resource availability and heterogeneity, whereas variation partitioning results showed that soil resource availability explained the majority of the variance in abundance, and the contribution of soil resource heterogeneity was marginal. These results indicated that soil resource availability plays a more important role in determining karst plant community composition than soil resource heterogeneity. Our SEMs further found that the multiple direct and indirect processes of soil resource availability in determining karst species diversity and abundance were different in different vegetation types. Soil resource availability and heterogeneity both played a certain role in determining karst plant community composition, while the importance of soil resource availability far exceeded soil resource heterogeneity. We propose that steering community restoration and reconstruction should be highly dependent on soil resource availability, and multiple direct and indirect pathways of soil resource availability for structuring karst plant communities need to be taken into account. Both limited resource availability and significant resource heterogeneity are key features of karst landscapes. Our study first considered simultaneously resource availability and heterogeneity in karst regions and then quantified and compared the effects of resource availability and heterogeneity on community abundance and species diversity from the relevance‐theoretic perspective. More importantly, our study has important guiding significance to the vegetation restoration.

Background In the Mediterranean climate, plants have evolved under conditions of low soil-water and nutrient availabilities and have acquired a series of adaptive traits that, in turn exert strong feedback on soil fertility, structure, and protection. As a result, plant-soil systems constitute complex interactive webs where these adaptive traits allow plants to maximize the use of scarce resources. Scope It is necessary to review the current bibliography to highlight the most know characteristic mechanisms underlying Mediterranean plant-soil feed-backs and identify the processes that merit further research in order to reach an understanding of the plant-soil feedbacks and its capacity to cope with future global change scenarios. In this review, we characterize the functional and structural plant-soil relationships and feedbacks in Mediterranean regions. We thereafter discuss the effects of global change drivers on these complex interactions between plants and soil. Conclusions The large plant diversity that characterizes Mediterranean ecosystems is associated to the success of coexisting species in avoiding competition for soil resources by differential exploitation in space (soil layers) and time (year and daily). Among plant and soil traits, high foliar nutrient re-translocation and large contents of recalcitrant compounds reduce nutrient cycling. Meanwhile increased allocation of resources to roots and soil enzymes help to protect against soil erosion and to improve soil fertility and capacity to retain water. The long-term evolutionary adaptation to drought of Mediterranean plants allows them to cope with moderate increases of drought without significant losses of production and survival in some species. However, other species have proved to be more sensitive decreasing their growth and increasing their mortality under moderate rising of drought. All these increases contribute to species composition shifts. Moreover, in more xeric sites, the desertification resulting from synergic interactions among some related process such as drought increases, torrential rainfall increases and human driven disturbances is an increasing concern. A research priority now is to discern the effects of long-term increases in atmospheric CO₂ concentrations, warming, and drought on soil fertility and water availability and on the structure of soil communities (e.g., shifts from bacteria to fungi) and on patching vegetation and root-water uplift (from soil to plant and from soil deep layers to soil superficial layers) roles in desertification.

Periodic and regular assessment of land degradation in arid regions of the world is essential for implementing suitable corrective measures in time. Assessment of soil properties based on soil sampling from hot arid tracts followed by laboratory analysis is a formidable task. Reflectance spectroscopy appears to be an emerging technology for the assessment of soils in extreme environment. In this study, soil spectral library of 138 soil samples from hot arid western Rajasthan have been created in visible, near-infrared and short wave infrared (350–2500 nm) region of the electromagnetic spectrum along with the measurements of basic soil properties. Further, spectral reflectance-based algorithms have been developed for rapid assessment of soil resources of arid regions. Results showed that sand and clay content may be satisfactorily estimated from linear models involving principal components (PCs) or derived band reflectance as the input variables (R ² = 0.41–0.43). Organic carbon (OC) content of soil was also found satisfactorily correlated with spectral data (R ² = 0.27). Derived band reflectance corresponding to Operational Land Imager bands of Landsat-8 has been found best to predict soil properties. Soil OC content has been found to be best estimated by derived spectral band data corresponding to spectral bands of IRS-P6 satellite. Partial least square regression-based models were found even better than the PCs-based and band reflectance-based multiple regression models for estimating soil properties. Thus, the present study indicates that soil spectral reflectance data captured by remote sensing satellites may have a great potential for rapid assessment of soil resources in arid regions.

Soil resource heterogeneity has clear effects on plant root development and overall plant performance. Here we test whether contrasting vegetation types have similar or different responses to soil patches of differing resource availability. We examined the fine root responses of grassland and forest vegetation at the northern edge of the Great Plains to transplanted patches of resource-poor and resource-rich soils, using rhizotron imaging. Every aspect of measured root behavior, including root length, production, mortality, turnover, variability and size distribution, varied significantly between patch types, and most aspects also varied between vegetation types. Most importantly, differential responses to patches between grassland and forest were shown by significant interactions between patch type and vegetation for two response variables. First, root length variability was significantly lower in resource-rich compared to resource-poor patches in forest but not grassland. Second, the proportion of very fine roots was significantly greater in resource-rich than resource-poor patches in forests but not grassland. Thus, compared to grassland, forest more fully occupied resource-rich patches relative to resource-poor patches by allocating more growth to very fine roots. We report the first example of significant differences between vegetation types (grassland and forest) in root responses to soil resource heterogeneity measured in a field experiment. The relatively high ability of forest roots to more fully occupy resource-rich patches is consistent with the global expansion of woody vegetation and associated increases in soil heterogeneity.