Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, ...agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.
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•Litterbags of a mixture of leaves, hand net, and corer was the compared techniques.•We got 540 samples in five forested wetlands temporary and permanent for one year.•Richness and ...diversity were higher with a hand net, followed by litterbags, and corer.•nMDS and ANOSIM separating two macroinvertebrate assemblages in respect to techniques.•We reinforce findings from the joint use of two techniques, hand net, and corer.
Forest wetlands are biodiversity hotspots that perform functions of vital ecological importance, but they are among the world's most threatened ecosystems. Due to their high diversity of habitats and species, the study of their benthic macroinvertebrate communities is challenging, and there is no consensus on which sampling methods allow a better representation of these communities. Here we compared the performance of 3 sampling methods (hand net, corer and litterbags) in 2 temporary and 3 permanent forested wetlands in southern Chile, which were bimonthly sampled throughout a year, with 108 samples per wetland. Our results indicated that the greatest abundance and diversity were collected with the hand net, followed by the litterbags and the corer. The composition of communities collected by the hand net and litterbags were more similar between them than that of communities collected by the corer (where Chironomidae and Oligochaeta were common). We suggest that the combined use of the hand net and corer could provide a good representation of macroinvertebrate communities in forest wetlands, as they would allow recording most of the diversity, including taxa that are both sensitive and tolerant to stressors.
El anfípodo Hyalella patagonica está muy extendido en aguas interiores andinas de la Patagonia argentina y chilena, esta especie habita en zonas litorales de ríos, arroyos, lagos y lagunas, que según ...la literatura tienen patrones de distribución espacial principalmente agregados. El objetivo del presente estudio es aplicar diferentes tipos de modelos de agregación para explicar la distribución espacial de H. patagonica colectada en un arroyo del norte de la Patagonia. Se aplicaron diferentes tipos de coeficientes de dispersión para comprender el patrón espacial de H. patagonica. Los resultados revelaron que la población de H. patagonica tiene una distribución agregada, pero no necesariamente una distribución binomial negativa, que es frecuente en el modelo probabilístico asociado a la distribución espacial agregada. Los resultadosserían similares a los patrones observados para el género Hyalella en aguas interioresde la Patagonia.
The Chilean Patagonian lakes are characterized by their marked oligotrophic or oligomesotrophic status and low zooplankton species abundances, many of these lakes with oligomesotrophic status is ...associated to human intervention due towns in their shores. The aim of the present study was determine the relations between spectral properties (LANDSAT/OLI), chlorophyll and plankton abundances in two north Patagonian lakes, Villarica, that has two towns in its shore, and Caburgua, that has native forest in its shores as basis of environmental pollution monitoring tools. The results revealed that Villarica lake has high reflectances in near infrared, red and green bands, high chlorophyll (a, b and c) concentrations, and high bacterial and plankton abundances, whereas Caburgua lakes has low reflectance in the same bands, and low chlorophyll concentrations, low bacterial and plankton abundances, with exception to high mixotrophic ciliates. The obtained results agree with limnological observations about both lakes, and the comparison with spectral properties agree with similar observations for glacial north Patagonian lakes about spectral properties and zooplankton community.
Extreme temperatures have increased in intensity, duration and frequency in the last century, with potential consequences on key ecological processes such as organic matter breakdown. Many stream ...ecosystems are fueled by the breakdown of terrestrial leaf litter, which is exposed to atmospheric conditions for certain periods of time before entering the stream. Thus, extreme warming or freezing events may affect the litter physicochemical structure, which could translate into altered breakdown within the stream. The above prediction was tested by exposing litter of common riparian tree species in southern Chile to freezing (−20 ºC; dry or wet litter) or heating (40 ºC) and comparing breakdown with control litter exposed to room temperature (20 ºC), separating the effects of different breakdown agents (i.e., leaching, microorganisms and detritivores). The greatest effects were found in wet litter subjected to freezing; this treatment significantly increased leaching in the short term (48 h) and slowed down breakdown in the long term (30 days), mostly due to the inhibition of microbial breakdown. Heating also retarded microbial breakdown, but the effect was smaller. Our results suggest that short-term extreme temperatures—particularly cold ones—have the potential to slow down litter breakdown in streams, which will most likely impact global biogeochemical cycles where streams play a key role.
The marine ecosystem of the Chilean Patagonia is considered structurally and functionally unique, because it is the transition area between the Antarctic climate and the more temperate Pacific ...region. However, due to its remoteness, there is little information about Patagonian marine biodiversity, which is a problem in the face of the increasing anthropogenic activity in the area. The aim of this study was to analyze community patterns and environmental characteristics of scavenging crustaceans in the Chilean Patagonian Sea, as a basis for comparison with future situations where these organisms may be affected by anthropogenic activities. These organisms play a key ecological role in marine ecosystems and constitute a main food for fish and dolphins, which are recognized as one of the main tourist attractions in the study area. We sampled two sites (Puerto Cisnes bay and Magdalena sound) at four different bathymetric strata, recording a total of 14 taxa that included 7 Decapoda, 5 Amphipoda, 1 Isopoda and 1 Leptostraca. Taxon richness was low, compared to other areas, but similar to other records in the Patagonian region. The crustacean community presented an evident differentiation between the first stratum (0-50 m) and the deepest area in Magdalena sound, mostly influenced by Pseudorchomene sp. and a marked environmental stratification. This species and Isaeopsis sp. are two new records for science. The discovery of undescribed species evidences that this region needs further studies exploring its biodiversity, which is most likely being already impacted by anthropogenic pressure.
The decapod fauna in the intertidal zone of the rocky shores of Chile is highly diverse, especially along the northern and central mainland coasts, where the influence of the cold Humboldt Current ...results in high productivity. One of the most abundant species in these ecosystems is the decapod Cyclograpsus cinereus Dana, 1851. The aim of the present study, carried out in the spring and summer seasons between 2018 and 2020, was to determine the spatial distribution patterns of the decapod C. cinereus in different sites along the rocky shores of Antofagasta bay, northern Chile, in order to establish probabilistic models that explain its distribution at each site. Individuals were counted in random quadrants in the intertidal zone. The data thus obtained were processed by application of the variance/mean ratio to determine whether the distribution of individuals was random, aggregated or uniform, associated with Poisson, negative binomial or positive binomial distributions, respectively. The data revealed aggregated (negative binomial) distribution in 15 sampling events, and uniform (positive binomial) distribution in 4 events. The sampling sites were located on rocky shores in four sectors of an urban zone, and two in a protected zone; no significant differences were found between the densities of the sites in the two zones. The results of the interpretative probabilistic models indicated aggregated distribution patterns, agreeing with previously reported interpretative probabilistic models for the distribution of decapods on the rocky shores of central and southern Chile.
The intertidal crustaceans on the Chilean coast are characterized by high diversity and niche specialization. The present study applied a size overlap null model for intertidal decapod communities at ...four different sites on the Chilean coast. The results revealed that there is a size overlap for the four sites, though body size is significantly different for each location. This means that the reported species would share their ecological niches. The results agree with the first classic environmental descriptions for Chilean intertidal decapods at a local scale and support the observations for similar species on the southern Pacific and southern Atlantic coasts.
The genus
is the main component of southern South American temperate forests. The 40
species, evergreen and deciduous, and some natural hybrids are spread among Central and Southern Chile, Argentina, ...New Zealand, Australia, New Guinea and New Caledonia.
,
and
are potentially very important timber producers due to their high wood quality and relative fast growth; however, indiscriminate logging has degraded vast areas the Chilean forest causing a serious state of deterioration of their genetic resource. The South of Chile has a large area covered by secondary forests of
. These forests have a high diversity of species, large amount of biomass and high silvicultural potential. This work shows a case of hybrid identification in
subgenus in different secondary forests of Chile, using high resolution melting. Unknown samples of
subgenus are genetically distinguishable with the ITS region of
,
and
species. It was not possible to distinguish between unknown samples of Andean versus coastal origin. Melting curves with ITS approach of unknown material are genetically similar, positioned between
and
and distant from
. The unknown samples are genetically very close to
. This suggests the presence of hybrid individuality between species (
×
) with the possibility of introgression towards the gene pool of
, producing the deciduous foliage that is both present. The trnL locus has no distinction between the
and
species, since a similar melting curve is present and equal Tm (80.00 °C). The trnL locus cannot be genetically distinguished from one unknown sample of
to another, as highlighted in this study.
Forest ecosystems provide services that are important for human use; one of the most critical ecosystem services is the provision and regulation of water. Basins with high forest improves ...hydrological functionality by promoting reduction in surface runoff, increase infiltration and aquifer recharge, and ensures base flow regulation amongst others. On the other hand, the conversion towards highly anthropized productive systems is usually accompanied by precarious environmental management that alters the hydrological cycle and reduction in water quality in basins.
The goal of this study was to analyze land use changes and their effect on water efficiency index (WEI) in three sub-basins.
The methodology included a multi-temporal analysis of satellite images to identify land uses, also the use of SWAT (Soil and Water Assessment Tool) model for hydrological analysis in each sub-basin, information needed for calculating the WEI.
The results revealed the existence of no significant difference in terms of WEI between the sub-basins with predominant tree cover of native or artificial, being higher (0.89) than the WEI values reported by the sub-basin with agricultural land use (0.65). It is concluded that hydrological functions are more efficient in basins with forest cover, made up of native or exotic species, than agricultural land use with annual crop rotations. The results contribute to decision making on public policies associated to the rural productive activities.
Finally, we conclude the necessity of the promotion of forest plantation management techniques that avoid clear-cutting and multiple rotations in basin headwaters and riparian areas.
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