ChapterPDF Available

Capítulo 5- Suelos- informe pais estado del medio ambiente en chile 2018

Authors:

Abstract

Tradicionalmente se asocia al suelo como el sustento de la vegetación, y por ende como un componente esencial de los sistemas productivos agrícolas y forestales. Sin embargo, el valor del suelo y la importancia de su conservación van mucho más allá de su rol más evidente, la producción de alimentos, existiendo un sinnúmero de bienes y servicios que el suelo provee y que se relacionan con la calidad del ambiente. Por ejemplo, el potencial de biodiversidad del suelo es enorme, si se toma en consideración que la mayoría de los antibióticos se han obtenido de organismos del suelo, incluyendo la penicilina. Además, el suelo cumple un rol fundamental con respecto al cambio climático, por cuanto es reconocido como un reservorio de carbono, que almacena este elemento en mayor contenido que la atmósfera y toda la vegetación en su conjunto. Se estima que el suelo podría contribuir a capturar 20.000 megatoneladas de carbono en 25 años, lo que constituye un 10% de las emisiones mundiales de gases de efecto invernadero. Esta ambiciosa meta sólo es posible aplicando prácticas de manejo sustentable que favorezcan la captura e incorporación de carbono al suelo. Probablemente, uno de los roles más desconocidos, pero esenciales del suelo, es su función en el ciclo hidrológico, llegando a contener dos tercios del agua dulce del planeta, transformándolo en el mayor reservorio de este vital elemento. Además, dadas sus propiedades mineralógicas, químicas y físicas, el suelo constituye un verdadero filtro para sedimentos, pesticidas, metales pesados y microorganismos patógenos, entre otros. Un manejo apropiado de los recursos hídricos contenidos en el suelo, es esencial para el mantenimiento de sus funciones y servicios ecosistémicos. El suelo es además el sostén de gran parte de las actividades humanas incluyendo la vivienda, el transporte y gran cantidad de emplazamientos industriales y productivos no agrícolas, las que muchas veces se llevan de manera no sustentable sobre este recurso. A nivel mundial, los suelos sufren una creciente presión por la intensificación de su uso para la agricultura, el pastoreo, la silvicultura y la urbanización. Esta demanda creciente se debe principalmente al explosivo aumento de la población mundial, lo que combinado con usos y prácticas no adecuadas genera una degradación importante del recurso suelo. En el país existe la necesidad urgente de hacerse cargo de estos problemas, ya que el suelo es un recurso natural no-renovable a escala humana, cuya pérdida y degradación son generalmente irreversibles. A pesar de ser una nación pequeña, Chile cuenta con una enorme diversidad de suelos, contando con diez de los doce órdenes de suelo hasta ahora descritos por la taxonomía de suelos (USDA). Esta diversidad está dada por un extraordinario gradiente climático, que permite que en el Desierto de Atacama existan suelos únicos, inexistentes en otras partes del planeta, que la Depresión intermedia de la zona Central se encuentre dentro de las áreas más productivas del planeta, y que los remotos fiordos de la Patagonia cuenten con un manto casi continuo de suelos orgánicos, constituyendo una reserva de carbono de nivel mundial. Este patrimonio edáfico único merece ser conocido por la nación para poder generar medidas y prácticas que ayuden a su sostenibilidad en el largo plazo. Chile enfrenta numerosos desafíos en cuanto al recurso suelo. La zona más crítica en cuanto a las amenazas es la zona central. Por un lado esta zona del país cuenta con un pujante sector agropecuario y forestal, concentrado en los fértiles valles centrales y la Cordillera de la Costa respectivamente, y por otro, aquí se sustenta uno de los ecosistemas más amenazados del país, los que se ven continuamente presionados por el cambio de uso de suelo motivados por el desplazamiento de las actividades agrícola y forestal hacia suelos marginales, y por la expansión urbana descontrolada que está sellando para siempre con cemento los suelos más productivos del país. Solo considerando ocho ciudades de la zona central, se ha perdido más de 30.000 hectáreas de suelo agrícola de alta calidad los últimos 25 años, una cifra alarmante si se considera que Chile tiene solo un 3.3% de su superficie cubierta con suelos altamente productivos, sumando un total de 2.526.723 hectáreas (apenas 0,14 hectáreas por habitante). Además, no se ha logrado eliminar el flagelo de la erosión, siendo esta la principal causa de degradación de los suelos, afectando sobre todo y con mayor intensidad a aquellos de las laderas de la Cordillera de la Costa. A esto se suma una serie de malas prácticas agrícolas y una laxa regulación ambiental que provoca una continua degradación del recurso. Es así como en casi todas las regiones del país se han detectado problemas de contaminación de suelos de diversa índole. La falta de conocimiento del recurso es probablemente uno de los factores más críticos en Chile. Solo el 25% del territorio tiene cartografía oficial de suelos. Apenas se conocen los suelos que están más allá de las zonas de explotación agrícola intensiva, siendo la mayoría de las investigaciones a escala nacional existentes basadas en herramientas satelitales y muy pocos datos de terreno. En este sentido, es crítico que se tome responsabilidad frente a la realización de los estudios necesarios para conocer los suelos que van más allá de las zonas de actual uso intensivo, ya que no se podrá protegerlos y aprovecharlos debidamente si es que aún no se conocen. Por último, se requiere urgente de una acción concreta del Estado para asegurar la sostenibilidad a largo plazo del recurso, principalmente a través de dos acciones: la primera es contar con una institucionalidad única que maneje los aspectos relacionados al recurso, hoy dispersos en una serie de organismos del Estado; y la segunda es contar con una legislación de ordenamiento territorial que incluya al suelo como un componente esencial dentro de las políticas de gestión del territorio. Chile es uno de los pocos países de la OCDE y de Latinoamérica que no cuenta con una legislación que proteja el recurso. En el país se debe asegurar hoy la generación de acciones conjuntas que permitan que siga existiendo suelo para las futuras generaciones.
A preview of the PDF is not available
ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
Aluminum (Al) is a major constraint for plant growth by inducing inhibition of root elongation in acid soils around the world. Besides, drought is another major abiotic stress that adversely affects growth and productivity of agricultural crops. The plant growth–promoting (PGP) rhizobacterial strains are useful choice to decrease these stressful effects and is now extensively in practice. However, the use of bacterial inoculation has not been attempted for the mitigation of Al stress in plants growing at high Al levels under drought stress. Therefore, in the present study, Al- and drought-tolerant bacterial strains were isolated from Lactuca sativa and Beta vulgaris rhizospheric soils. Among the bacterial isolates, two strains, CAM12 and CAH6, were selected based on their ability to tolerate high levels of Al (8 mM) and drought (15% PEG-6000, w/v) stresses. The bacterial strains CAM12 and CAH6 were identified as Bacillus megaterium and Pantoea agglomerans, respectively, by 16S rRNA gene sequence homology. Moreover, both strains showed multiple PGP traits even in the presence of abiotic stresses. In the pot experiments, inoculation of the strains CAM12 and CAH6 as individually or as included in a consortium improved the Vigna radiata growth under abiotic stress conditions and reduced Al uptake in plants. However, the most effective treatment was seen with bacterial consortium that allowed the plants to tolerate abiotic stress effectively and achieved better growth. These results indicate that bacterial consortium could be used as a bio-inoculant for enhancing V. radiata growth in soil with high Al levels subjected to drought conditions.
Article
Full-text available
Microplastics are emerging as a steadily increasing environmental threat. Wastewater treatment plants efficiently remove microplastics from sewage, trapping the particles in the sludge and preventing their entrance into aquatic environments. Treatment plants are essentially taking the microplastics out of the waste water and concentrating them in the sludge, however. It has become common practice to use this sludge on agricultural soils as a fertilizer. The aim of the current research was to evaluate the microplastic contamination of soils by this practice, assessing the implications of successive sludge applications by looking at the total count of microplastic particles in soil samples. Thirty-one agricultural fields with different sludge application records and similar edaphoclimatic conditions were evaluated. Field records of sludge application covered a ten year period. For all fields, historical disposal events used the same amount of sludge (40 ton ha ⁻¹ dry weight). Extraction of microplastics was done by flotation and particles were then counted and classified with the help of a microscope. Seven sludge samples were collected in the fields that underwent sludge applications during the study period. Soils where 1, 2, 3, 4, and 5 applications of sludge had been performed had a median of 1.1, 1.6, 1.7, 2.3, and 3.5 particles g ⁻¹ dry soil, respectively. There were statistical differences in the microplastic contents related to the number of applications that a field had undergone (1, 2, 3 < 4, 5). Microplastic content in sludge ranged from 18 to 41 particles g ⁻¹ , with a median of 34 particles g ⁻¹ . The majority of the observed microplastics were fibers (90% in sludge, and 97% in soil). Our results indicate that microplastic counts increase over time where successive sludge applications are performed. Microplastics observed in soil samples stress the relevance of sludge as a driver of soil microplastic contamination.
Article
Full-text available
Several studies have demonstrated the relevance of endophytic bacteria on the growth and fitness of agriculturally-relevant plants. To our knowledge, however, little information is available on the composition, diversity, and interaction of endophytic bacterial communities in plants struggling for existence in the extreme environments of Chile, such as the Atacama Desert (AD) and Patagonia (PAT). The main objective of the present study was to analyze and compare the composition of endophytic bacterial communities associated with roots and leaves of representative plants growing in Chilean extreme environments. The plants sampled were: Distichlis spicate and Pluchea absinthioides from the AD, and Gaultheria mucronata and Hieracium pilosella from PAT. The abundance and composition of their endophytic bacterial communities was determined by quantitative PCR and high–throughput sequencing of 16S rRNA, respectively. Results indicated that there was a greater abundance of 16S rRNA genes in plants from PAT (1013 to 1014 copies g−1 DNA), compared with those from AD (1010 to 1012 copies g−1 DNA). In the AD, a greater bacterial diversity, as estimated by Shannon index, was found in P. absinthioides, compared with D. spicata. In both ecosystems, the greater relative abundances of endophytes were mainly attributed to members of the phyla Proteobacteria (14% to 68%), Firmicutes (26% to 41%), Actinobacteria (6 to 23%) and Bacteroidetes (1% to 21%). Our observations revealed that most of operational taxonomic units (OTUs) were not shared between tissue samples of different plant species in both locations, suggesting the effect of the plant genotype (species) on the bacterial endophyte communities in Chilean extreme environments, where Bacillaceae and Enterobacteriacea could serve as keystone taxa as revealed our linear discriminant analysis.
Article
Full-text available
Phyllosphere bacteria have received little attention despite their important roles in shaping plant performance traits. In this study, we characterize the bacterial communities on leaves of native trees inhabiting sclerophyllous forests in central Chile, one of the world's biodiversity hotspots. Additionally, we provide profiles of bacterial communities on grape leaves and berries of organic and conventional vineyards. Results of 16S rRNA gene amplicon sequence analysis showed that 45% of OTUs were shared across forest leaves, grape leaves, and grape berries. Conventional management had higher number of OTUs shared with forest leaves than organic management. In addition, grape leaves subjected to conventional management had higher alpha diversity than those with organic management, while no significant effect of agricultural management was observed in grape berries. Indicator analysis showed that Bdellovibrio, Beijerinckia, and Spirosoma were typical for forest leaves, whereas Enhydrobacter, Delftia, Proteiniclasticum, Arsenicicoccus, and Alkaliphilus were typical for the vineyard phyllosphere. Regarding agricultural managements, Beijerinckia, Sedimentibacter, Nesterenkonia, Gluconobacter, Conexibacter, and Anaeromyxobacter were typical for conventional grape leaves, whereas no genus‐level indicator was found for organic vineyard leaves. These results provide new insights of the diversity patterns of the phyllosphere microbiome in native and cultivated lands and suggest that both of these microbiomes are connected and integrated systems. Bacterial communities on leaves of native trees inhabiting sclerophyllous forests in central Chile were characterized. Results of 16S rRNA gene amplicon sequence analysis showed that 45% of OTUs were shared across all habitats.Forest and vineyard microbiomes are connected and integrated systems.
Article
Full-text available
The Atacama Desert is a highly complex, extreme ecosystem which harbors microorganisms remarkable for their biotechnological potential. Here, a soil bacterial prospection was carried out in the high Altiplano region of the Atacama Desert (>3,800 m above sea level; m a.s.l.), where direct anthropogenic interference is minimal. We studied: (1) soil bacterial community composition using high-throughput sequencing of the 16S rRNA gene and (2) bacterial culturability, by using a soil extract medium (SEM) under a factorial design of three factors: temperature (15 and 30°C), nutrient content (high and low nutrient disposal) and oxygen availability (presence and absence). A total of 4,775 OTUs were identified and a total of 101 isolates were selected for 16S rRNA sequencing, 82 of them corresponded to unique or non-redundant sequences. To expand our view of the Altiplano landscape and to obtain a better representation of its microbiome, we complemented our Operational Taxonomic Units (OTUs) and isolate collection with data from other previous data from our group and obtained a merged set of OTUs and isolates that we used to perform our study. Taxonomic comparisons between culturable microbiota and metabarcoding data showed an overrepresentation of the phylum Firmicutes (44% of isolates vs. 2% of OTUs) and an underrepresentation of Proteobacteria (8% of isolates vs. 36% of OTUs). Within the Next Generation Sequencing (NGS) results, 33% of the OTUs were unknown up to genus, revealing an important proportion of putative new species in this environment. Biochemical characterization and analysis extracted from the literature indicated that an important number of our isolates had biotechnological potential. Also, by comparing our results with similar studies on other deserts, the Altiplano highland was most similar to a cold arid desert. In summary, our study contributes to expand the knowledge of soil bacterial communities in the Atacama Desert and complements the pipeline to isolate selective bacteria that could represent new potential biotechnological resources.
Article
Full-text available
Acidic ash derived volcanic soils (Andisols) support 50% of cereal production in Chile. Nitrogen (N) is essential for cereal crops and commonly added as urea with consequent environmental concerns due to leaching. Despite the relevance of N to plant growth, few studies have focused on understanding the application, management and ecological role of N2-fixing bacterial populations as tool for improve the N nutrition of cereal crops in Chile. It is known that N2-fixing bacteria commonly inhabits diverse plant compartments (e.g., rhizosphere and root endosphere) where they can supply N for plant growth. Here, we used culture-independent and dependent approaches to characterize and compare the putative N2-fixing bacteria associated with the rhizosphere and root endosphere of wheat plants grown in an Andisol from southern Chile. Our results showed significantly greater bacterial loads in the rhizosphere than the root endosphere. Quantitative PCR results indicated that the copy number of the 16S rRNA gene ranged from 1012~1013 and 107~108 g−1 sample in rhizosphere and root endosphere, respectively. The nifH gene copy number ranged from 105~106 and 105 g−1 sample in rhizosphere and root endosphere, respectively. The total culturable bacteria number ranged from 109~1010 and 107~108 CFU g−1 sample in rhizosphere and 104~105 and 104 CFU g−1 sample in root endosphere using LB and NM-1 media, respectively. Indirect counts of putative N2-fixing bacteria were 103 and 102~103 CFU g−1 sample in rhizosphere and root endosphere using NFb medium, respectively. Sequencing of 16S rRNA genes from randomly selected putative N2-fixing bacteria revealed the presence of members of Proteobacteria (Bosea and Roseomonas), Actinobacteria (Georgenia, Mycobacterium, Microbacterium, Leifsonia, and Arthrobacter), Bacteroidetes (Chitinophaga) and Firmicutes (Bacillus and Psychrobacillus) taxa. Differences in 16S rRNA and putative nifH-containing bacterial communities between rhizosphere and root endosphere were shown by denaturing gradient gel electrophoresis (DGGE). This study shows a compartmentalization between rhizosphere and root endosphere for both the abundance and diversity of total (16S rRNA) and putative N2-fixing bacterial communities on wheat plants grown in Chilean Andisols. This information can be relevant for the design and application of agronomic strategies to enhance sustainable N-utilization in cereal crops in Chile.
Article
Full-text available
Agriculture is one of the main drivers of land conversion, and agriculture practices can impact on microbial diversity. Here we characterized the phyllosphere fungal diversity associated with Carménère grapevines under conventional and organic agricultural management. We also explored the fungal diversity present in the adjacent sclerophyllous forests to explore the potential role of native forest on vineyard phyllosphere. After conducting D2 and ITS2 amplicon sequencing, we found that fungal diversity indices did not change between conventional and organic vineyards, but community structure was sensitive to the agricultural management. On the other hand, we found a high proportion of shared fungal OTUs between vineyards and native forests. In addition, both habitats had similar levels of fungal diversity despite forest samples were derived from multiple plant species. In contrast, the community structure was different in both habitats. Interestingly, the native forest had more unidentified species and unique OTUs than vineyards. Forest dominant species were Aureobasidium pullulans and Endoconidioma populi , whereas Davidiella tassiana , Didymella sp. , and Alternaria eichhorniae were more abundant in vineyards. Overall, this study argues that a better understanding of the relationship native forests and agroecosystems is needed for maintaining and enhancing ecosystem services provided by natural ecosystems. Finally, knowledge of microbial communities living in the Chilean Mediterranean biome is needed for appropriate conservation management of these biomes and their classification as biodiversity hotspots.
Article
Full-text available
Over the last two decades, a considerable effort has been made to decipher the biogeography of soil microbial communities as a whole, from small to broad scales. In contrast, few studies have focused on the taxonomic groups constituting these communities; thus, our knowledge of their ecological attributes and the drivers determining their composition and distribution is limited. We applied a pyrosequencing approach targeting 16S ribosomal RNA (rRNA) genes in soil DNA to a set of 2173 soil samples from France to reach a comprehensive understanding of the spatial distribution of bacteria and archaea and to identify the ecological processes and environmental drivers involved. Taxonomic assignment of the soil 16S rRNA sequences indicated the presence of 32 bacterial phyla or subphyla and 3 archaeal phyla. Twenty of these 35 phyla were cosmopolitan and abundant, with heter ogeneous spatial distributions structured in patches ranging from a 43-to 260-km radius. The hierarchy of the main environmental drivers of phyla distribution was soil pH > land management > soil texture > soil nutrients > climate. At a lower taxonomic level, 47 dominant genera belonging to 12 phyla aggregated 62.1% of the sequences. We also showed that the phylum-level distribution can be determined largely by the distribution of the dominant genus or, alternatively, reflect the combined distribution of all of the phylum members. Together, our study demonstrated that soil bacteria and archaea present highly diverse biogeographical patterns on a nationwide scale and that studies based on intensive and systematic sampling on a wide spatial scale provide a promising contribution for elucidating soil biodiversity determinism.
Article
The present study was conducted to evaluate the potential of co-inoculation of Trichoderma harzianum (Th) with the plant growth promoting rhizobacteria (PGPRs) on the growth and essential oil yield of Mentha arvensis under pot as well as field conditions. For in vitro screening of compatible strains, cross streak assays were undertaken and further assessed to confirm their ability to form biofilm help in root colonization. in vitro interaction studies showed that Trichoderma harzianum (Th) did not antagonize with Stenotrophomonas spp (Az-30), Bacillus flexus (Sd-30) and Brevibacterium halotolerans (Sd-6) strains individually, indicating the possibility of using these combinations for plant growth promotion studies. These compatible combinations were further screened in vivo under greenhouse conditions on M. arvensis seedlings. The results revealed that co-inoculation of Th and Sd-6 increased plant growth, oil content, leaf-stem ratio, photosynthetic pigments, and nutrient uptake resulting in higher oil yields over other microbial treatments. The density (colony forming unit) of Th, as well as rhizobacteria, was significantly higher when compared to the single inoculations and control in the rhizospheric soil. Scanning electron microscopy revealed significant colonization of microbial biofilms on the root surface particularly for the best combination of Th and Sd-6. These results suggest the synergistic interactions between Brevibacterium halotolerans and Trichoderma harzianum for survival and improving plant growth and yield. The association of Sd-6 and Th, when applied under field conditions showed increased plant growth which provides an evidence that Th and Sd-6 together enhance the growth promoting abilities of each other significantly improving growth and yield of the crop. A higher number of propagules of both Th and Sd-6 may exert similar crop growth benefits in the subsequent crops while higher population of Th may protect the subsequent crops from many phytopathogens.
Article
In the present study, we assessed the non-carcinogenic and carcinogenic human health risk due to exposure to trace elements in soil and indoor dust in Puchuncaví valley. We also determined the associations between trace element concentration in hair/toenails and the estimated chronic daily intake of trace elements in soil and indoor dust. We found statistically significant association between the trace element concentration in hair/toenails and the estimated chronic daily intake of soil and indoor dust. Indoor dust was more important than soil in terms of human exposure to trace elements in Puchuncaví, due to the high concentration of trace elements on this environmental media and long periods of time that the population spends at their households. With regards to non-carcinogenic risk, we found that there was no health risk associated to soil and indoor dust exposure in the Puchuncaví valley, because none of the hazard quotient values surpassed 1.0. However, carcinogenic risk due to arsenic exposure was above the threshold value of 1.0E-04 in the population of young children (from 1 to 5 years old) in all studied areas, including the control, and in the population of children (from 6 to <18 years old) in the exposed area. Such risk values are classified as unacceptable (US EPA, 2001), requiring some target intervention from the Chilean government.