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Plant Effects on Soils in Drylands: Implications for Community Dynamics and Ecosystem Restoration

DOI: 10.1007/1-4020-3447-4_6
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    ABSTRACT: The adaptation of plants to particular soil types has long intrigued biologists. Gypsum soils occupy large areas in many regions of the world and host a striking biological diversity, but their vegetation has been much less studied than that developing over serpentine or saline soils. Herein, we review all aspects of plant life on gypsum ecosystems, discuss the main processes driving their structure and functioning, and highlight the main conservation threats that they face. Plant communities in gypsum habitats typically show distinctive bands at very small spatial scales, which are mainly determined by topography. Plants living on gypsum soils can be classified into three categories: (i) wide gypsophiles are specialists that can penetrate the physical soil crust during early life stages and have physiological adjustments to cope with the chemical limitations imposed by gypsum soils; (ii) narrow gypsophiles are refugee plants which successfully deal with the physical soil crust and can tolerate these chemical limitations but do not show specific adaptations for this type of soils; and (iii) gypsovags are non-specialist gypsum plants that can only thrive in gypsum soils when the physical crust is absent or reduced. Their ability to survive in gypsum soils may also be mediated by below-ground interactions with soil microorganisms. Gypsophiles and gypsovags show efficient germination at low temperatures, seed and fruit heteromorphism within and among populations, and variation in seed dormancy among plants and populations. In gypsum ecosystems, spatio-temporal changes in the composition and structure of above-ground vegetation are closely related to those of the soil seed bank. Biological soil crusts (BSCs) dominated by cyanobacteria, lichens and mosses are conspicuous in gypsum environments worldwide, and are important drivers of ecosystem processes such as carbon and nitrogen cycling, water infiltration and run-off and soil stability. These organisms are also important determinants of the structure of annual plant communities living on gypsum soils. The short-distance seed dispersal of gypsophiles is responsible for the high number of very narrow endemisms typically found in gypsum outcrops, and suggests that these species are evolutionarily old taxa due to the time they need to colonize isolated gypsum outcrops by chance. Climate change and habitat fragmentation negatively affect both plants and BSCs in gypsum habitats, and are among the major threats to these ecosystems. Gypsum habitats and specialists offer the chance to advance our knowledge on restrictive soils, and are ideal models not only to test important evolutionary questions such as tolerance to low Ca/Mg proportions in soils, but also to improve the theoretical framework of community ecology and ecosystem functioning.
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    ABSTRACT: Semiarid areas host several hotspots of biodiversity, and provide vital ecosystem services. Afforestation has been extensively used to restore these areas. However, studies on the impact of afforestation on the provision of ecosystem goods and services are scarce. We have evaluated changes in the provision of ecosystem services after afforestation in a semiarid area in southeastern Spanish. Through a multi-criteria analysis, Pinus halepensis plantations were compared to four unrestored landscape units (grasslands, Stipa tenacissima steppes, shrublands and abandoned agricultural fields), using six ecological and socioeconomic criteria and fourteen indicators. The weights of criteria and indicators were obtained from the opinion of 38 stakeholders. The values of each indicator per landscape unit were obtained from empirical data and bibliographic sources. From the stakeholders’ perspective, regulating and supporting services and biodiversity were more important than provisioning, cultural and economical services. Pine plantations enhanced ecosystem services as hydrological and climatic regulation, and aesthetic value, but decreased the provision of other services as forage productivity, water availability, and small and big game habitat. Pine plantations provided the highest levels of ecosystem services. The multi-criteria and participatory assessment allowed managers to check the overall impact of their decisions, and it represents an efficient tool for reciprocal learning and negotiation.
    Ecological Indicators 08/2014; 43:56–68. DOI:10.1016/j.ecolind.2014.02.017 · 3.23 Impact Factor

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