Environmental impacts of utility-scale solar energy Hernandez, R.R.; Easter, S.B.; Murphy-Mariscal, M.L. ...
Renewable & sustainable energy reviews,
January 2014, 2014, 2014-1-00, 20140101, Letnik:
29
Journal Article
Recenzirano
Odprti dostop
Renewable energy is a promising alternative to fossil fuel-based energy, but its development can require a complex set of environmental tradeoffs. A recent increase in solar energy systems, ...especially large, centralized installations, underscores the urgency of understanding their environmental interactions. Synthesizing literature across numerous disciplines, we review direct and indirect environmental impacts – both beneficial and adverse – of utility-scale solar energy (USSE) development, including impacts on biodiversity, land-use and land-cover change, soils, water resources, and human health. Additionally, we review feedbacks between USSE infrastructure and land-atmosphere interactions and the potential for USSE systems to mitigate climate change. Several characteristics and development strategies of USSE systems have low environmental impacts relative to other energy systems, including other renewables. We show opportunities to increase USSE environmental co-benefits, the permitting and regulatory constraints and opportunities of USSE, and highlight future research directions to better understand the nexus between USSE and the environment. Increasing the environmental compatibility of USSE systems will maximize the efficacy of this key renewable energy source in mitigating climatic and global environmental change.
Theoretical models predict that the relative importance of facilitation and competition may vary inversely across gradients of abiotic stress. However, these predictions have not been thoroughly ...tested in the field, especially in semi-arid environments. In this study, we evaluated how the net effect of the tussock grass Stipa tenacissima on the shrub Pistacia lentiscus varied across a gradient of abiotic stress in semi-arid Mediterranean steppes. We fitted the relationship between accumulated rainfall and the relative neighbour index (our measures of abiotic stress and of the net effect of S. tenacissima on P. lentiscus, respectively), which varied across this gradient, to a quadratic model. Competitive interactions dominated at both extremes of the gradient. Our results do not support established theory. Instead, they suggest that a shift from facilitation to competition under high abiotic stress conditions is likely to occur when the levels of the most limiting resource are so low that the benefits provided by the facilitator cannot overcome its own resource uptake.
Current theoretical models and field evidence suggest that facilitation and interference act simultaneously in the field, but there is little information on their joint dynamics under varying abiotic ...conditions. We evaluated spatial and temporal variations in the positive, negative, and net effects of the tussock grass Stipa tenacissima on the shrub Pistacia lentiscus in Mediterranean semiarid grasslands. We performed a field experiment in which positive (microclimatic amelioration and water inputs from runoff) and negative (belowground competition) effects were experimentally manipulated under contrasting levels of stress. The environment provided by S. tenacissima (tussock treatment) improved the survival and physiological status of planted P. lentiscus seedlings. The elimination of shade and competition from S. tenacissima significantly decreased and increased, respectively, seedling performance as compared to the tussock treatment. We found evidence that microclimatic amelioration is the main positive factor involved in the interaction under study, and that it can balance the negative effects of belowground competition. The latter was also important, especially after major rainfall events. In contrast with previous studies, both the water inputs from runoff and the soil chemical fertility were found to have a relatively weak effect in the interaction under study. The net effect of S. tenacissima on P. lentiscus was always facilitative, but the magnitude of this effect increased with the harshness of the environmental conditions in both space and time. Despite this, the mechanisms underlying plant-plant interaction responded unequally to small-scale environmental variation. Our results agree with models suggesting that the magnitude of facilitation may increase under stressful conditions, and provide evidence of the dynamic nature of positive and negative interactions in the field.
Semi-arid ecosystems are privileged sites to address the effects of plant interactions on community structure and dynamics because environmental conditions are demanding and may change quickly, ...altering in significant ways the balance between positive and negative effects among neighboring plants. Plant interaction processes have been well documented in the semi-arid region of Southeast Spain over the last 15 years. In this article we review the growing body of research on plant–plant interactions available from this area, highlighting its importance in increasing our knowledge on this field of study. This review has been organized in five sections, i) facilitation mechanisms; ii) the nurse effect; iii) the balance of interactions and environmental, ontogenic, temporal, and spatial gradients; iv) the effects of facilitation on biodiversity; and, v) facilitation and ecosystem functioning. Mechanisms of facilitation in these systems are relatively well known, but not completely explored. In these environments competition, mainly for water, is intense between neighbors and switches in intensity from belowground to aboveground as productivity increases. By contrast, facilitation may decrease quickly with increasing productivity, although the balance between facilitation and competition is not fully understood, and is further complicated because shifts can also be driven by factors such as life history or physiology of interacting species. Positive interactions are critical for maintaining biodiversity in some ecosystems in SE Spain, but their role as a driver of ecosystem functioning is less clear. Research on plant–plant interactions in this region has been highly influential and has contributed to our overall understanding of plant community dynamics. Despite the important progress achieved during the last 15 years, there is still substantial scope for exploring the effects of plant interactions at the ecosystem level, and their role as modulators of disturbances such as the current global environmental change.
► Semi-arid ecosystems are privileged sites to address the effects of plant interactions. ► Plant interactions have been well documented in semi-arid SE Spain over the years. ► Competition switches in intensity from below- to aboveground as productivity increases. ► Facilitation decreases with increasing productivity. ► There is still substantial scope for exploring interactions balance and their effects.
Biological soil crusts (BSCs), composed of lichens, cyanobacteria, mosses, liverworts and microorganisms, are key biotic components of arid and semi-arid ecosystems worldwide. Despite they are ...widespread in Spain, these organisms have been historically understudied in this country. This trend is beginning to change as a recent wave of research has been identifying BSCs as a model ecological system. Many studies and research projects carried out in Spain have explored the role of BSCs on water, carbon and nitrogen fluxes, the interactions between BSCs and vascular plants, their dynamics after disturbances, and their response to global change, among other topics. In this article we review the growing body of research on BSCs available from semi-arid areas of Spain, highlighting its importance for increasing our knowledge on this group of organisms. We also discuss how it is breaking new ground in emerging research areas on the ecology of BSCs, and how it can be use to guide management and restoration efforts. Finally, we provide directions for future research on the ecology of BSCs in Spain and abroad.
► Biological soil crusts (BSCs) are key components, but historically understudied, of Spanish semi-arid ecosystems. ► We review the growing body of research on BSCs available from these ecosystems. ► BSCs are proving to be an excellent model system to foster new ways of thinking about key community and ecosystem ecology topics. ► The study of these organisms is opening new and highly promising research lines.
Semi-arid landscapes in the western Mediterranean have been used for millennia, resulting in large-scale transformations and widespread degradation. In some instances, these degraded environments ...have been unable to recover spontaneously, and ambitious restoration programs have been launched over the last decades to improve landscape conditions. Ecological restoration may speed up succession, promote more complex communities and increase their functionality. But uncertainty in the definition of restoration objectives, failure to identify most efficient practices and, particularly, socio-economic and cultural constrains may compromise future actions. Here, we review recent advances in the restoration of semi-arid vegetation cover in the Iberian southeast, discuss future challenges and suggest two key steps towards increasing the consistency and efficiency of restoration programs: emphasis on ecosystem services, and implementation of participative and adaptive management practices.
► We review past and current restoration practices in the semi-arid Iberian southeast. ► Restoration is compromised by uncertain objectives and inefficient practices. ► But the main constraints to successful restoration are socio-economical and cultural. ► To solve this, projects should be evaluated on composition, function and services. ► Projects should also incorporate principles of participative and adaptive management.
Models derived from satellite image data are needed to monitor the status of terrestrial ecosystems across large spatial scales. However, a remote sensing‐based approach to quantify soil ...multifunctionality at the global scale is missing despite significant research efforts on this topic. A major constraint for doing so is the availability of suitable global‐scale field data to calibrate remote sensing indicators (RSI) and, to a lesser extent, the sensitivity of spectral data of available satellite sensors to soil background and atmospheric conditions. Here, we aimed to develop a soil multifunctionality model to monitor global drylands coupling ground data on 14 soil functions of 222 dryland areas from six continents to 18 RSI derived from a time series (2006–2013) Landsat dataset. Among the RSI evaluated, the chlorophyll absorption ratio index was the best predictor of soil multifunctionality in single‐variable‐based models (r = 0.66, P < 0.01, NMRSE = 0.17). However, a multi‐variable RSI model combining the chlorophyll absorption ratio index, the global environment monitoring index and the canopy‐air temperature difference improved the accuracy of quantifying soil multifunctionality (r = 0.73, P < 0.01, NMRSE = 0.15). Furthermore, the correlation between RSI and soil variables shows a wide range of accuracy with upper and lower values obtained for AMI (r = 0.889, NMRSE = 0.05) and BGL (r = 0.685, NMRSE = 0.18) respectively. Our results provide new insights on assessing soil multifunctionality using RSI that may help to monitor temporal changes in the functioning of global drylands effectively.
The work highlights the potential for estimating soil multifunctionality from satellite data in drylands on a global scale. The work comprises field campaigns for soil composition measurements, multispectral satellite image information and modelling approaches. A multi‐variable RSI model combining the chlorophyll absorption ratio index, the global environment monitoring index and the canopy‐air temperature difference improved the overall accuracy in the quantification of soil multifunctionality. Our results provide new insights on assessing soil multifunctionality with artificial intelligence that may help to monitor temporal changes across global drylands.
The influence of biological soil crusts (BSCs) on the small-scale spatial distribution of inorganic nitrogen (N) in drylands is largely unknown, despite their known impact and importance on the N ...cycle in these environments. We evaluated how perennial plants and BSCs affected small-scale spatial patterns of soil inorganic N (ammonium and nitrate) availability in a semiarid grassland from Spain. The data were analyzed by using geostatistical methods. The range of semivariograms for ammonium and nitrate, and the coefficient of variation of nitrate, were lower in BSC-dominated microsites than in plant-dominated microsites. Our results suggest that BSCs modulate the small-scale spatial pattern of inorganic N, producing more homogeneous conditions for spatial distribution of inorganic N forms than microsites provided by plants. These results may have important repercussions for the foraging strategies and ability of plant roots to uptake N.
► It is largely unknown how biological soil crusts (BSCs) affect the small-scale spatial pattern of inorganic N in soils. ► We evaluated how BSCs and vascular plants influence the spatial pattern of inorganic N in a semiarid grassland. ► BSCs modulate the small-scale spatial patterns of ammonium and nitrate. ► BSC produce a more homogeneous spatial distribution of inorganic N than plant microsites.
Spiking is a useful approach to improve the accuracy of regional or national calibrations when they are used to predict at local scales. To do this, a small subset of local samples (spiking subset) ...is added to recalibrate the initial calibration. If the spiking subset is small in comparison with the size of the initial calibration set, then it could have little noticeable effect and a small improvement can be expected. For these reasons, we hypothesized that the accuracy of the spiked calibrations can be improved when the spiking subset is extra‐weighted. We also hypothesized that the spiking subset selection and the initial calibration size could affect the accuracy of the recalibrated models. To test these hypotheses, we evaluated different strategies to select the best spiking subset, with and without extra‐weighting, to spike three different‐sized initial calibrations. These calibrations were used to predict the soil organic carbon (SOC) content in samples from four target sites. Our results confirmed that spiking improved the prediction accuracy of the initial calibrations, with any differences depending on the spiking subset used. The best results were obtained when the spiking subset contained local samples evenly distributed in the spectral space, regardless of the initial calibration's characteristics. The accuracy was improved significantly when the spiking subset was extra‐weighted. For medium‐ and large‐sized initial calibrations, the improvement from extra‐weighting was larger than that caused by the increase in spiking subset size. Similar accuracies were obtained using small‐ and large‐sized calibrations, suggesting that incipient spectral libraries could be useful if the spiking subset is properly selected and extra‐weighted. When small‐sized spiking subsets were used, the predictions were more accurate than those obtained with ‘geographically‐local’ models. Overall, our results indicate that we can minimize the efforts needed to use near‐infrared (NIR) spectroscopy effectively for SOC assessment at local scales.
1. Theoretical and modelling studies highlight the importance of the spatial patterns of organisms for ecosystem functioning, stability and dynamics. However, there is little empirical evidence as to ...their importance as drivers of such ecosystem attributes. 2. We evaluated the relationships between different biological soil crust attributes (spatial pattern, cover and diversity) and ecosystem functioning in two semiarid areas differing in the developmental stage of these crusts. 3. We found a significant direct relationship between spatial pattern and both soil bulk density and respiration (surrogates of ecosystem infiltration and nutrient cycling, respectively) at one of our study sites. However, the strength of such a relationship was lower than that found between attributes such as cover and evenness and the same ecosystem functioning surrogates. 4. Our results represent, to our knowledge, some of the first empirical evidence linking the spatial pattern of a community and ecosystem functioning. They also suggest that the importance of spatial pattern as a driver of ecosystem functioning may depend on community attributes such as cover and diversity, and that its importance may be lower than that of these attributes.
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