Javier Pérez - Academia.edu (original) (raw)

Papers by Javier Pérez

Forest Ecology and Management, 2013

In low-order forested streams, watershed-scale land-use modifications, such as the replacement of... more In low-order forested streams, watershed-scale land-use modifications, such as the replacement of native vegetation by conifer monocultures, can affect energy inputs into streams and trophic interactions within these donor-controlled food webs. We examined the effects of Pinus radiata plantations on structural (benthic macroinvertebrate communities) and functional (alder and pine leaf-litter breakdown) attributes of headwater streams. We compared three streams draining pine plantations with three draining natural deciduous forests. We found differences in the structure of benthic macroinvertebrate communities, namely lower densities of shredders in streams flowing through pine plantations. Breakdown rates of alder leaves was a 20% lower in streams draining pine plantations, and breakdown of pine needles, a much lower quality material, was slower than that of alder and did not differ between stream types. Although fungal activity was similar in all streams, lower detritivore densities under pine plantations could explain the lower rate of alder breakdown in these environments. The present study points out that pine monocultures alter the structure of benthic macroinvertebrate communities and reduce detritus processing capacity of streams. However, these effects were weaker than expected due to the presence of deciduous riparian forest in pine streams.

Hydrobiologia, 2013

Agricultural and urban runoffs result in increased nitrogen and phosphorus inputs in rivers and a... more Agricultural and urban runoffs result in increased nitrogen and phosphorus inputs in rivers and are the cause of eutrophication. Headwater streams are less frequently affected by these impairments because of the low-to-moderate human activities there. Eutrophication can affect the structure and function of benthic communities in headwater streams, stimulating the activity of heterotrophic microorganisms and macroinvertebrates on a pivotal process such as leaflitter decomposition. In this study, we monitored the breakdown of alder leaves in six headwater streams that constitute a moderate nutrient enrichment gradient. Breakdown experiments were conducted in autumn-winter and leaf carbon, nitrogen and phosphorus, and associated aquatic hyphomycetes and macroinvertebrates were determined. The increase in nutrient availability in the stream water enhanced leaflitter quality and led to an increase in the hyphomycete assemblage evenness and a reduction of shredder densities. However, contrary to our expectations, dissolved nutrient availability did not explain the breakdown rates. Thus, the absence of a clear effect of nutrient enrichment of stream water on the leaf breakdown rate highlights the difficulties of predicting the response of this ecosystem process to slight levels of eutrophication in headwater streams.

The Science of the total environment, Jan 15, 2015

Although temporary streams represent a high proportion of the total number and length of running ... more Although temporary streams represent a high proportion of the total number and length of running waters, historically the study of intermittent streams has received less attention than that of perennial ones. The goal of the present study was to assess the effects of flow cessation on litter decomposition in calcareous streams under oceanic climate conditions. For this, leaf litter of alder was incubated in four streams (S1, S2, S3 and S4) with different flow regimes (S3 and S4 with zero-flow periods) from northern Spain. To distinguish the relative importance and contribution of decomposers and detritivores, fine- and coarse-mesh litter bags were used. We determined processing rates, leaf-C, -N and -P concentrations, invertebrate colonization in coarse bags and benthic invertebrates. Decomposition rates in fine bags were similar among streams. In coarse bags, only one of the intermittent streams, S4, showed a lower rate than that in the other ones as a consequence of lower inverteb...

Limnetica, 2013

Evaluation of the ACR SmartButton thermometer and a low-cost protective case for continuous strea... more Evaluation of the ACR SmartButton thermometer and a low-cost protective case for continuous stream temperature measurement Water temperature is a common variable of interest in stream ecology studies. In this paper, the performance of the ACR SmartButton thermometer and a low-cost protective case were evaluated for stream temperature measurement. The accuracy of the SmartButtons at 0, 10 and 15 • C was well within the ± 1 • C range specified by the manufacturer. For 50-60 % of the readings performed, the error was greater than the ± 0.2 • C correction factor accepted for meteorological temperature measurements. However, the observed level of accuracy is most likely sufficient for most biological applications if the loggers are calibrated against a reference standard. The metallic case that we used had a negligible effect on temperature measurements and offers a reliable way to protect the SmartButton during use in small streams.

Hydrobiologia, 2015

In temperate streams, water temperature and organic matter inputs from surrounding forest vary al... more In temperate streams, water temperature and organic matter inputs from surrounding forest vary along the altitude. We tested if the different features of streams of similar size determined by an altitudinal gradient might differentially affect the processing rate of different quality leaves (alder, oak and beech). To distinguish the relative contribution of microbial decomposition from overall decomposition, fine- and coarse-mesh bags were used. We determined decomposition rates, leaf-N and -P concentration, microbial respiration (fine bags), invertebrate colonisation (coarse bags) and density and identity of benthic invertebrates in three second-order streams. Alder decomposed faster than the other species in all three streams and regardless of mesh size due to its lower values of C:N, C:P and N:P. Unexpectedly, microbial decomposition rate did not vary among streams for any of the leaf species. The total decomposition rate of alder and oak showed a negative trend along the altitudinal gradient, the magnitude of the change in decomposition rates being similar for both species. The density and structure of the invertebrate community differed along the altitudinal gradient, related to temperature and surrounding vegetation, determining the decomposition rate. Unexpectedly, sensitivity of decomposition rate of different quality leaves to temperature does not differ along the gradient.

Journal of the North American Benthological Society, 2011

The main purpose of our work was to elucidate factors responsible for the geographical difference... more The main purpose of our work was to elucidate factors responsible for the geographical differences in leaf-litter decomposition rates in Spanish oligotrophic headwater streams. Decomposition experiments with alder (Alnus glutinosa) leaf litter were carried out in 22 headwater streams in 4 different climatic regions across the Iberian Peninsula (Cornisa Cantábrica, Cordillera Litoral Catalana, Sierra de Guadarrama, and Sierra Nevada). Streams that were similar in size, flowed mainly over siliceous substrate in catchments with scarce human settlements and activities, and fell within a range of low nutrient concentrations were chosen in each region. Breakdown rates were regionally variable and were low (0.109-0.198% ash-free dry mass [AFDM]/degree day [dd]) in the Cornisa Cantábrica, the most mesic and Atlantic region, and high (0.302-0.639% AFDM/dd) in Sierra de Guadarrama, one of the coldest and most inland areas. Temperature was not the determining factor affecting differences in breakdown rates among regions, and breakdown rates were not related to concentrations of dissolved nutrients. However, microbial reproductive activity (sporulation rates) was significantly correlated with dissolved P concentration. Breakdown rates were explained better by presence and feeding activities of detritivores than by decomposer activity. Incorporation of breakdown rates in assessment schemes of stream ecological status will be difficult because leaf processing does not respond unequivocally to environmental factors when climatic regions are considered. Thus, regional adjustments of baseline standards in reference conditions will be required.

Hydrobiologia, 2013

We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs... more We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs (surface release in autumn-winters) (north Spain) to assess the effect of flow regulation on structural and functional characteristics of stream ecosystems. We based our approach on the use of structural metrics (density, biomass, richness and diversity) in combination with two functional diversity indices based on biological and ecological traits: FD PG index, related to species richness, and FD Q , which incorporates evenness across taxa. Although water physicochemical parameters were unaffected by the reservoirs during the study period (autumnwinter), macroinvertebrate metrics were lower below the dams, with detritivores (shredders and collector-gatherers) being the most affected. The alder leaf breakdown rate estimated by the litter-bag technique was related to the density, biomass, richness, diversity and FD PG index of shredders, compromising the ecosystem functioning. The most plausible origin for the observed differences in macroinvertebrate metrics between upstream and downstream reaches was the change of the flow regime caused by the impoundments at downstream sites, leading to droughts in summer in those naturally permanently flowing streams. The observed functional diversity loss might reduce the chances of the community to override natural or man-induced fluctuations in their environment with possible repercussions on important ecosystem functions and services.

We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs... more We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs (surface release in autumn-winters) (north Spain) to assess the effect of flow regulation on structural and functional characteristics of stream ecosystems. We based our approach on the use of structural metrics (density, biomass, richness and diversity) in combination with two functional diversity indices based on biological and ecological traits: FD PG index, related to species richness, and FD Q , which incorporates evenness across taxa. Although water physicochemical parameters were unaffected by the reservoirs during the study period (autumnwinter), macroinvertebrate metrics were lower below the dams, with detritivores (shredders and collector-gatherers) being the most affected. The alder leaf breakdown rate estimated by the litter-bag technique was related to the density, biomass, richness, diversity and FD PG index of shredders, compromising the ecosystem functioning. The most plausible origin for the observed differences in macroinvertebrate metrics between upstream and downstream reaches was the change of the flow regime caused by the impoundments at downstream sites, leading to droughts in summer in those naturally permanently flowing streams. The observed functional diversity loss might reduce the chances of the community to override natural or man-induced fluctuations in their environment with possible repercussions on important ecosystem functions and services.

Microbial Ecology, 2014

We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and euc... more We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and eucalyptus leaf litter respond to changes in habitat characteristics (transplantation experiment). We examined the breakdown of leaf materials and the associated fungal communities at two contrasting sites, a headwater stream (H) and a midreach (M). Agroforestry increased from headwater to midreach. One month after the start of experiments at both sites, some leaf samples from the midreach site were transplanted to the headwater site (M-H treatment). Although both sites showed similar dissolved inorganic nutrient concentrations, eucalyptus leaves initially incubated at the midreach site (M, M-H) increased their breakdown rate compared to those incubated along the experiment at the headwater site (H). Alder breakdown rate was not enhanced, suggesting that their consumption was not limited by nutrient availability. Sporulation rates clearly differed between leaf types (alder > eucalyptus) and streams (H > M), but no transplantation effect was detected. When comparing conidial assemblages after transplantation, an inoculum effect (persistence of early colonizing species) was clear in both leaf species. Substrate preference and shifts in the relative importance of some fungal species along the process were also observed. Overall, our results support the determining role of the initial conditioning phase on the whole litter breakdown process, highlighting the importance of intrinsic leaf characteristics and those of the incubation habitat.

Plant litter represents a major basal resource in streams, where its decomposition is partly regu... more Plant litter represents a major basal resource in streams, where its decomposition is partly regulated by litter traits. Litter-trait variation may determine the latitudinal gradient in decomposition in streams, which is mainly microbial in the tropics and detritivore-mediated at high latitudes. However, this hypothesis remains untested, as we lack information on large-scale trait variation for riparian litter. Variation cannot easily be inferred from existing leaf-trait databases, since nutrient resorption can cause traits of litter and green leaves to diverge. Here we present the first global-scale assessment of riparian litter quality by determining latitudinal variation (spanning 107°) in litter traits (nutrient

The main goal of this study was to examine the natural variability of alder (Alnus glutinosa (L.)... more The main goal of this study was to examine the natural variability of alder (Alnus glutinosa (L.) GAERTN.) leaf processing and explore its potentiality as a functional indicator to assess the ecological status of Spanish headwater streams. Breakdown of leaf litter was studied during autumn-winter in reference headwater streams of two regions of northern Spain: the Basque Country (on the Atlantic) and Catalonia (on the Mediterranean). Spring experiments were also carried out in the Atlantic region in order to study seasonal changes. Leaf mass loss rates were slightly higher in Catalonian streams. Temperature was not the main factor for explaining differences between the two regions. In the Atlantic one, however, water temperature determined the spatial and seasonal variability of leaf litter processing. Because of the high natural variability in breakdown rates, our results highlight the difficulty in detecting moderate impairments on stream functioning through the analysis of leaf litter decomposition if this process is not accompanied by the study of other factors affecting it. J. PÉREZ et al.

Science of The Total Environment, 2013

and sharing with colleagues.

Forest Ecology and Management, 2013

In low-order forested streams, watershed-scale land-use modifications, such as the replacement of... more In low-order forested streams, watershed-scale land-use modifications, such as the replacement of native vegetation by conifer monocultures, can affect energy inputs into streams and trophic interactions within these donor-controlled food webs. We examined the effects of Pinus radiata plantations on structural (benthic macroinvertebrate communities) and functional (alder and pine leaf-litter breakdown) attributes of headwater streams. We compared three streams draining pine plantations with three draining natural deciduous forests. We found differences in the structure of benthic macroinvertebrate communities, namely lower densities of shredders in streams flowing through pine plantations. Breakdown rates of alder leaves was a 20% lower in streams draining pine plantations, and breakdown of pine needles, a much lower quality material, was slower than that of alder and did not differ between stream types. Although fungal activity was similar in all streams, lower detritivore densities under pine plantations could explain the lower rate of alder breakdown in these environments. The present study points out that pine monocultures alter the structure of benthic macroinvertebrate communities and reduce detritus processing capacity of streams. However, these effects were weaker than expected due to the presence of deciduous riparian forest in pine streams.

Hydrobiologia, 2013

Agricultural and urban runoffs result in increased nitrogen and phosphorus inputs in rivers and a... more Agricultural and urban runoffs result in increased nitrogen and phosphorus inputs in rivers and are the cause of eutrophication. Headwater streams are less frequently affected by these impairments because of the low-to-moderate human activities there. Eutrophication can affect the structure and function of benthic communities in headwater streams, stimulating the activity of heterotrophic microorganisms and macroinvertebrates on a pivotal process such as leaflitter decomposition. In this study, we monitored the breakdown of alder leaves in six headwater streams that constitute a moderate nutrient enrichment gradient. Breakdown experiments were conducted in autumn-winter and leaf carbon, nitrogen and phosphorus, and associated aquatic hyphomycetes and macroinvertebrates were determined. The increase in nutrient availability in the stream water enhanced leaflitter quality and led to an increase in the hyphomycete assemblage evenness and a reduction of shredder densities. However, contrary to our expectations, dissolved nutrient availability did not explain the breakdown rates. Thus, the absence of a clear effect of nutrient enrichment of stream water on the leaf breakdown rate highlights the difficulties of predicting the response of this ecosystem process to slight levels of eutrophication in headwater streams.

The Science of the total environment, Jan 15, 2015

Although temporary streams represent a high proportion of the total number and length of running ... more Although temporary streams represent a high proportion of the total number and length of running waters, historically the study of intermittent streams has received less attention than that of perennial ones. The goal of the present study was to assess the effects of flow cessation on litter decomposition in calcareous streams under oceanic climate conditions. For this, leaf litter of alder was incubated in four streams (S1, S2, S3 and S4) with different flow regimes (S3 and S4 with zero-flow periods) from northern Spain. To distinguish the relative importance and contribution of decomposers and detritivores, fine- and coarse-mesh litter bags were used. We determined processing rates, leaf-C, -N and -P concentrations, invertebrate colonization in coarse bags and benthic invertebrates. Decomposition rates in fine bags were similar among streams. In coarse bags, only one of the intermittent streams, S4, showed a lower rate than that in the other ones as a consequence of lower inverteb...

Limnetica, 2013

Evaluation of the ACR SmartButton thermometer and a low-cost protective case for continuous strea... more Evaluation of the ACR SmartButton thermometer and a low-cost protective case for continuous stream temperature measurement Water temperature is a common variable of interest in stream ecology studies. In this paper, the performance of the ACR SmartButton thermometer and a low-cost protective case were evaluated for stream temperature measurement. The accuracy of the SmartButtons at 0, 10 and 15 • C was well within the ± 1 • C range specified by the manufacturer. For 50-60 % of the readings performed, the error was greater than the ± 0.2 • C correction factor accepted for meteorological temperature measurements. However, the observed level of accuracy is most likely sufficient for most biological applications if the loggers are calibrated against a reference standard. The metallic case that we used had a negligible effect on temperature measurements and offers a reliable way to protect the SmartButton during use in small streams.

Hydrobiologia, 2015

In temperate streams, water temperature and organic matter inputs from surrounding forest vary al... more In temperate streams, water temperature and organic matter inputs from surrounding forest vary along the altitude. We tested if the different features of streams of similar size determined by an altitudinal gradient might differentially affect the processing rate of different quality leaves (alder, oak and beech). To distinguish the relative contribution of microbial decomposition from overall decomposition, fine- and coarse-mesh bags were used. We determined decomposition rates, leaf-N and -P concentration, microbial respiration (fine bags), invertebrate colonisation (coarse bags) and density and identity of benthic invertebrates in three second-order streams. Alder decomposed faster than the other species in all three streams and regardless of mesh size due to its lower values of C:N, C:P and N:P. Unexpectedly, microbial decomposition rate did not vary among streams for any of the leaf species. The total decomposition rate of alder and oak showed a negative trend along the altitudinal gradient, the magnitude of the change in decomposition rates being similar for both species. The density and structure of the invertebrate community differed along the altitudinal gradient, related to temperature and surrounding vegetation, determining the decomposition rate. Unexpectedly, sensitivity of decomposition rate of different quality leaves to temperature does not differ along the gradient.

Journal of the North American Benthological Society, 2011

The main purpose of our work was to elucidate factors responsible for the geographical difference... more The main purpose of our work was to elucidate factors responsible for the geographical differences in leaf-litter decomposition rates in Spanish oligotrophic headwater streams. Decomposition experiments with alder (Alnus glutinosa) leaf litter were carried out in 22 headwater streams in 4 different climatic regions across the Iberian Peninsula (Cornisa Cantábrica, Cordillera Litoral Catalana, Sierra de Guadarrama, and Sierra Nevada). Streams that were similar in size, flowed mainly over siliceous substrate in catchments with scarce human settlements and activities, and fell within a range of low nutrient concentrations were chosen in each region. Breakdown rates were regionally variable and were low (0.109-0.198% ash-free dry mass [AFDM]/degree day [dd]) in the Cornisa Cantábrica, the most mesic and Atlantic region, and high (0.302-0.639% AFDM/dd) in Sierra de Guadarrama, one of the coldest and most inland areas. Temperature was not the determining factor affecting differences in breakdown rates among regions, and breakdown rates were not related to concentrations of dissolved nutrients. However, microbial reproductive activity (sporulation rates) was significantly correlated with dissolved P concentration. Breakdown rates were explained better by presence and feeding activities of detritivores than by decomposer activity. Incorporation of breakdown rates in assessment schemes of stream ecological status will be difficult because leaf processing does not respond unequivocally to environmental factors when climatic regions are considered. Thus, regional adjustments of baseline standards in reference conditions will be required.

Hydrobiologia, 2013

We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs... more We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs (surface release in autumn-winters) (north Spain) to assess the effect of flow regulation on structural and functional characteristics of stream ecosystems. We based our approach on the use of structural metrics (density, biomass, richness and diversity) in combination with two functional diversity indices based on biological and ecological traits: FD PG index, related to species richness, and FD Q , which incorporates evenness across taxa. Although water physicochemical parameters were unaffected by the reservoirs during the study period (autumnwinter), macroinvertebrate metrics were lower below the dams, with detritivores (shredders and collector-gatherers) being the most affected. The alder leaf breakdown rate estimated by the litter-bag technique was related to the density, biomass, richness, diversity and FD PG index of shredders, compromising the ecosystem functioning. The most plausible origin for the observed differences in macroinvertebrate metrics between upstream and downstream reaches was the change of the flow regime caused by the impoundments at downstream sites, leading to droughts in summer in those naturally permanently flowing streams. The observed functional diversity loss might reduce the chances of the community to override natural or man-induced fluctuations in their environment with possible repercussions on important ecosystem functions and services.

We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs... more We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs (surface release in autumn-winters) (north Spain) to assess the effect of flow regulation on structural and functional characteristics of stream ecosystems. We based our approach on the use of structural metrics (density, biomass, richness and diversity) in combination with two functional diversity indices based on biological and ecological traits: FD PG index, related to species richness, and FD Q , which incorporates evenness across taxa. Although water physicochemical parameters were unaffected by the reservoirs during the study period (autumnwinter), macroinvertebrate metrics were lower below the dams, with detritivores (shredders and collector-gatherers) being the most affected. The alder leaf breakdown rate estimated by the litter-bag technique was related to the density, biomass, richness, diversity and FD PG index of shredders, compromising the ecosystem functioning. The most plausible origin for the observed differences in macroinvertebrate metrics between upstream and downstream reaches was the change of the flow regime caused by the impoundments at downstream sites, leading to droughts in summer in those naturally permanently flowing streams. The observed functional diversity loss might reduce the chances of the community to override natural or man-induced fluctuations in their environment with possible repercussions on important ecosystem functions and services.

Microbial Ecology, 2014

We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and euc... more We investigated how fungal decomposer (aquatic hyphomycetes) communities colonizing alder and eucalyptus leaf litter respond to changes in habitat characteristics (transplantation experiment). We examined the breakdown of leaf materials and the associated fungal communities at two contrasting sites, a headwater stream (H) and a midreach (M). Agroforestry increased from headwater to midreach. One month after the start of experiments at both sites, some leaf samples from the midreach site were transplanted to the headwater site (M-H treatment). Although both sites showed similar dissolved inorganic nutrient concentrations, eucalyptus leaves initially incubated at the midreach site (M, M-H) increased their breakdown rate compared to those incubated along the experiment at the headwater site (H). Alder breakdown rate was not enhanced, suggesting that their consumption was not limited by nutrient availability. Sporulation rates clearly differed between leaf types (alder > eucalyptus) and streams (H > M), but no transplantation effect was detected. When comparing conidial assemblages after transplantation, an inoculum effect (persistence of early colonizing species) was clear in both leaf species. Substrate preference and shifts in the relative importance of some fungal species along the process were also observed. Overall, our results support the determining role of the initial conditioning phase on the whole litter breakdown process, highlighting the importance of intrinsic leaf characteristics and those of the incubation habitat.

Plant litter represents a major basal resource in streams, where its decomposition is partly regu... more Plant litter represents a major basal resource in streams, where its decomposition is partly regulated by litter traits. Litter-trait variation may determine the latitudinal gradient in decomposition in streams, which is mainly microbial in the tropics and detritivore-mediated at high latitudes. However, this hypothesis remains untested, as we lack information on large-scale trait variation for riparian litter. Variation cannot easily be inferred from existing leaf-trait databases, since nutrient resorption can cause traits of litter and green leaves to diverge. Here we present the first global-scale assessment of riparian litter quality by determining latitudinal variation (spanning 107°) in litter traits (nutrient

The main goal of this study was to examine the natural variability of alder (Alnus glutinosa (L.)... more The main goal of this study was to examine the natural variability of alder (Alnus glutinosa (L.) GAERTN.) leaf processing and explore its potentiality as a functional indicator to assess the ecological status of Spanish headwater streams. Breakdown of leaf litter was studied during autumn-winter in reference headwater streams of two regions of northern Spain: the Basque Country (on the Atlantic) and Catalonia (on the Mediterranean). Spring experiments were also carried out in the Atlantic region in order to study seasonal changes. Leaf mass loss rates were slightly higher in Catalonian streams. Temperature was not the main factor for explaining differences between the two regions. In the Atlantic one, however, water temperature determined the spatial and seasonal variability of leaf litter processing. Because of the high natural variability in breakdown rates, our results highlight the difficulty in detecting moderate impairments on stream functioning through the analysis of leaf litter decomposition if this process is not accompanied by the study of other factors affecting it. J. PÉREZ et al.

Science of The Total Environment, 2013

and sharing with colleagues.