Ecosystem Parameters Research Articles

Monitoring of parameters of coastal Arctic ecosystems for sustainability control by remote sensing in the short-wave range of radio waves with use of the experimental equipment of coherent reception of a ground-based measuring complex

Monitoring of the earth's surface by remote sensing in the short-wave band can provide a quick identification of some characteristics of coastal Arctic ecosystems. This band range allows to diagnose subsurface aspects of the earth, as the scattering parameter is affected by irregularities in the dielectric permittivity of subsurface structures. This method is based on the organization of the monitoring probe and may detect changes in these environments, for example, to assess hazardous natural phenomena, assessing sustainability, as well as some man-made hazards and etc. The problem of measuring and accounting for the scattering power of the earth's surface in the short-range of radio waves is important for a number of purposes, such as e.g diagnosing properties of the medium, which is of interest for geological, environmental studies. In this paper, we propose a new method for estimating the parameters of incoherent signal/noise ratio. The paper presents the results of comparison of the measurement method from the point of view of their admissible relative analytical errors. The new method is suggested. Accuracy new method on the order exceeds the widely-used standard method. Interpretation of the data is based on a statistical multiplicative model of the signal. Testing the method of obtained a signal/noise ratio in this model was produced by the example of a double reflection of the probe signal from the SW ionosphere in a vertical sounding (when using a satellite, the signal passes twice through the atmosphere and ionosphere). In this paper, a sensitivity of the model parameters was studied. To obtain the necessary experimental data, the pulse method of coherent reception was used. Analysis of analytical error of estimation of this parameter allowed to recommend a new method instead of standard method. A comparative analysis showed that the analytical (relative) accuracy of the determination of this parameter by a new method exceeded the widely-used standard method by the factor of ten.

Effect of dehydrated alfalfa on equine gastric and faecal microbial ecosystems

Disturbances of the gastric and hindgut ecosystems can lead to damage of the mucosa in the stomach and to intestinal colic. Some studies suggested that alfalfa could have preventive and healing capacities against gastric ulcerations. Preliminary data suggest that buffering capacity of alfalfa could also be beneficial for the hindgut ecosystem. The objective of this study was thus to assess the effect of dehydrated alfalfa pellets on the bacterial composition and the microbial activity of the equine gastric and faecal ecosystems. Six adult horses allotted in three pairs were studied in a 3 diets x 3 periods Latin square design experiment. During the 18-days experimental period, horses were fed grass hay (57% of total DMI) plus rolled barley and high-protein pellets (27% and 16% of total DMI) that represented a total intake of 1.8% BW / day. High-protein pellets consisted of alfalfa (obtained from 2 different processes, ALF – 2.35mcal/kg DM, 16.9% DM CP, 27.2% DM NFC, 10.8% DM ash, 2.1% DM Ca) and sunflower meal (SFM – 2.26 mcal/kg DM, 29.1% DM CP, 13.8% DM NFC, 7.2% DM ash, 0.5% DM Ca) pellets. Daily starch intake (289g) was divided into 2 equal meals. During the 5-day wash-out period, horses were fed grass hay and rolled barley (93% and 7% of total DMI respectively). On day 18 of the experimental period, faeces and gastric content were collected 3:00 and 3:30h respectively after morning barley + high-protein pellets meal to assess microbial ecosystem parameters. Horses fed ALF had significantly lower gastric concentrations of amylolytic bacteria than the ones fed SFM (P=0.04). On the contrary, amylolytic bacterial concentrations were higher in the faeces of horses fed ALF (P=0.01) compared to SFM diets, as well as lactate-utilizing and pectinolytic bacterial concentrations (P=0.05 and P=0.04 respectively). However, no significant modification of the pH, VFAs proportions, VFAs and lactic-acid concentrations were measured in gastric content and faeces. Regarding gastric health, minimizing carbohydrate fermentation could be beneficial, although VFAs concentrations were not different in this study between ALF and SFM diets. In the hindgut, higher lactate-utilizing concentrations could be advantageous to limit hindgut acidosis. Further work is required to understand the mechanisms that altered gastric and faecal bacterial ecosystems in horses fed the alfalfa diet and to investigate whether other proportions or processed forms of alfalfa in the diet would be more beneficial.

Towards the co-ordination of terrestrial ecosystem protocols across European research infrastructures.

The study of ecosystem processes over multiple scales of space and time is often best achieved using comparable data from multiple sites. Yet, long‐term ecological observatories have often developed their own data collection protocols. Here, we address this problem by proposing a set of ecological protocols suitable for widespread adoption by the ecological community. Scientists from the European ecological research community prioritized terrestrial ecosystem parameters that could benefit from a more consistent approach to data collection within the resources available at most long‐term ecological observatories. Parameters for which standard methods are in widespread use, or for which methods are evolving rapidly, were not selected. Protocols were developed by domain experts, building on existing methods where possible, and refined through a process of field testing and training. They address above‐ground plant biomass; decomposition; land use and management; leaf area index; soil mesofaunal diversity; soil C and N stocks, and greenhouse gas emissions from soils. These complement existing methods to provide a complete assessment of ecological integrity. These protocols offer integrated approaches to ecological data collection that are low cost and are starting to be used across the European Long Term Ecological Research community.

Ensemble data assimilation for ocean biogeochemical state and parameter estimation at different sites

We develop an efficient data assimilation system that aims at quantifying the uncertainties of various biogeochemical states and parameters. We explore the use of four different ensemble estimation techniques for tuning poorly constrained ecosystem parameters using a one-dimensional configuration of the Ocean Biogeochemical General Circulation Model. The schemes are all EnKF-based operating sequentially in time but have different correction equations. The 1D model is used to simulate the biogeochemical cycle at three different stations in mid and high latitudes. We assimilate monthly climatological profiles of nitrate, silicate, phosphate and oxygen in addition to seasonal surface pCO2 data, between 2006 and 2010. We use the data to optimize eleven ecosystem parameters in addition to all state variables of the model, describing the dynamical processes of the water column. Our assimilation results suggest the following: (1) Among all tested schemes, the one-step-ahead smoothing-based ensemble Kalman filter (OSA-EnKF) is robust and the most accurate, providing consistent and reliable state-parameter ensemble realizations. (2) Given the large uncertainties associated with the ecosystem parameters, estimating only the state variables is generally inconclusive and biased. (3) The OSA-EnKF successfully recovers the observed seasonal variability of the ecosystem dynamics at all stations and helps optimizing the parameters, eventually reducing the prediction errors of the nutrients’ concentrations. (4) The estimates of the parameters may have some temporally correlated features and they can also vary spatially between different regions depending on the magnitude of the bias in the observed variables and other factors such as the intensity of the bloom period. We further show that the presented assimilation system has the potential to be used in global models.

Estimation of Community Land Model parameters for an improved assessment of net carbon fluxes at European sites

AbstractThe Community Land Model (CLM) contains many parameters whose values are uncertain and thus require careful estimation for model application at individual sites. Here we used Bayesian inference with the DiffeRential Evolution Adaptive Metropolis (DREAM(zs)) algorithm to estimate eight CLM v.4.5 ecosystem parameters using 1 year records of half‐hourly net ecosystem CO2 exchange (NEE) observations of four central European sites with different plant functional types (PFTs). The posterior CLM parameter distributions of each site were estimated per individual season and on a yearly basis. These estimates were then evaluated using NEE data from an independent evaluation period and data from “nearby” FLUXNET sites at ~600 km distance to the original sites. Latent variables (multipliers) were used to treat explicitly uncertainty in the initial carbon‐nitrogen pools. The posterior parameter estimates were superior to their default values in their ability to track and explain the measured NEE data of each site. The seasonal parameter values reduced with more than 50% (averaged over all sites) the bias in the simulated NEE values. The most consistent performance of CLM during the evaluation period was found for the posterior parameter values of the forest PFTs, and contrary to the C3‐grass and C3‐crop sites, the latent variables of the initial pools further enhanced the quality‐of‐fit. The carbon sink function of the forest PFTs significantly increased with the posterior parameter estimates. We thus conclude that land surface model predictions of carbon stocks and fluxes require careful consideration of uncertain ecological parameters and initial states.

Assessment of Water quality in terms of physico – chemical parameters of East Godavari mangrove ecosystem (Coringa Wildlife Sanctuary) East Godavari, Andhra Pradesh, India.

Assessment of Water quality in terms of physico – chemical parameters of East Godavari mangrove ecosystem (Coringa Wildlife Sanctuary) East Godavari, Andhra Pradesh, India.

Formulation, General Features and Global Calibration of a Bioenergetically-Constrained Fishery Model.

Human exploitation of marine resources is profoundly altering marine ecosystems, while climate change is expected to further impact commercially-harvested fish and other species. Although the global fishery is a highly complex system with many unpredictable aspects, the bioenergetic limits on fish production and the response of fishing effort to profit are both relatively tractable, and are sure to play important roles. Here we describe a generalized, coupled biological-economic model of the global marine fishery that represents both of these aspects in a unified framework, the BiOeconomic mArine Trophic Size-spectrum (BOATS) model. BOATS predicts fish production according to size spectra as a function of net primary production and temperature, and dynamically determines harvest spectra from the biomass density and interactive, prognostic fishing effort. Within this framework, the equilibrium fish biomass is determined by the economic forcings of catchability, ex-vessel price and cost per unit effort, while the peak harvest depends on the ecosystem parameters. Comparison of a large ensemble of idealized simulations with observational databases, focusing on historical biomass and peak harvests, allows us to narrow the range of several uncertain ecosystem parameters, rule out most parameter combinations, and select an optimal ensemble of model variants. Compared to the prior distributions, model variants with lower values of the mortality rate, trophic efficiency, and allometric constant agree better with observations. For most acceptable parameter combinations, natural mortality rates are more strongly affected by temperature than growth rates, suggesting different sensitivities of these processes to climate change. These results highlight the utility of adopting large-scale, aggregated data constraints to reduce model parameter uncertainties and to better predict the response of fisheries to human behaviour and climate change.

Estimating Savanna Clumping Index Using Hemispherical Photographs Integrated with High Resolution Remote Sensing Images

In contrast to herbaceous canopies and forests, savannas are grassland ecosystems with sparsely distributed individual trees, so the canopy is spatially heterogeneous and open, whereas the woody cover in savannas, e.g., tree cover, adversely affects ecosystem structures and functions. Studies have shown that the dynamics of canopy structure are related to available water, climate, and human activities in the form of porosity, leaf area index (LAI), and clumping index (CI). Therefore, it is important to identify the biophysical parameters of savanna ecosystems, and undertake practical actions for savanna conservation and management. The canopy openness presents a challenge for evaluating canopy LAI and other biophysical parameters, as most remotely sensed methods were developed for homogeneous and closed canopies. Clumping index is a key variable that can represent the clumping effect from spatial distribution patterns of components within a canopy. However, it is a difficult task to measure the clumping index of the moderate resolution savanna pixels directly using optical instruments, such as the Tracing Radiation and Architecture of Canopies, LAI-2000 Canopy Analyzer, or digital hemispherical photography. This paper proposed a new method using hemispherical photographs combined with high resolution remote sensing images to estimate the clumping index of savanna canopies. The effects of single tree LAI, crown density, and herbaceous layer on the clumping index of savanna pixels were also evaluated. The proposed method effectively calculated the clumping index of moderate resolution pixels. The clumping indices of two study regions located in Ejina Banner and Weichang were compared with the clumping index product over China’s landmass.

Comparative fibre-degrading capacity in foals at immediate and late post-weaning periods

Total tract apparent digestibility of dietary fibrous components and parameters of the faecal digestive ecosystem were compared at immediate and late post-weaning periods using five foals. The foals were abruptly weaned (day 0) from their mares at 6 months of age. Immediately (day 0 to day 14) and later (day 131 to day 194) after weaning, foals received the same basal diet consisting of hay and pellets. Pellets were fed at 0.36% BW. Hay was offered ad libitum and corresponded to 120% of the average voluntary hay intake measured individually during the immediate (days 1 to 4) and late (days 180 to 183) post-weaning periods. Total feed intake was measured during the two post-weaning periods (from days 7 to 10 and from days 187 to 190). Total tract apparent digestibility of DM, organic matter (OM), NDF and ADF was assessed using a 4-day partial collection of faeces (from days 8 to 11 and from days 188 to 191). Major bacterial groups in faeces, Fibrobacter succinogenes, DM, pH and volatile fatty acids were quantified at days −1, 1, 3, 7, 14 and 180. During the post-weaning period, minor changes were observed in the composition and activity of the faecal microbiota. The amylolytic count in faeces decreased immediately after weaning (between days 1 and 7) (P<0.05). Later (from days 14 to 180), the molar proportion of propionate decreased (P=0.03). The limited alteration seen in the hindgut ecosystem was probably due to the fact that the foals had undergone a gradual dietary transition from milk to solid feed before weaning. Such conclusions have also been reported in other animal species. Between the immediate and late post-weaning periods, the average daily feed intake and the digestibility coefficients of DM, OM, NDF and ADF increased (P<0.05). These results could suggest an increase in the fibre-degrading capacity of foals after weaning.

Faecal parameters as biomarkers of the equine hindgut microbial ecosystem under dietary change

Faeces could be used for evaluating the balance of the equine hindgut microbial ecosystem, which would offer a practical method for assessing gut health and how this relates to disease. However, previous studies concluded that faeces microbial ecosystem was not representative of the proximal hindgut (caecum and ventral colon). This study aimed to evaluate if variations of the faecal microbial ecosystem were similar to those observed in the proximal hindgut. Six horses, fistulated in the caecum and right ventral (RV) colon, were subjected to a gradual change of diet, from a 100% hay (high fibre) diet (2.2 DM kg/day per 100 kg BW) to a 57% hay+43% barley (high starch) diet (0.8 DM kg/day per 100 kg BW hay and 0.6 DM kg/day per 100 kg BW barley). The two diets were iso-energetic and fed over a 3-week trial period. Samples of digesta from the caecum, RV colon and faeces were collected two times on the 10th and 20th day of the trial, for each diet to assess the microbial ecosystem parameters by both classical culture technics and biochemical methods. The variations observed in the caecal and colonic bacterial composition (increase in total anaerobic, amylolytic and lactate-utilizing and decrease in cellulolytic bacteria concentrations) and microbial activity (changes in volatile fatty acids concentrations and increase in lactate concentrations) demonstrated that the hay+barley diet caused changes in the hindgut microbial ecosystem. Similar variations were observed in the faecal microbial ecosystem. Feeding the hay+barley diet resulted in higher concentrations of faecal lipopolysaccharides. The functional bacterial group concentrations (cellulolytics, amylolytics and lactate utilizers) were significantly correlated between caecum and faeces and between colon and faeces. From analyses of the metabolites produced from microbial activity, only valerate concentration in the caecum and the proportion of propionate were significantly correlated with the same parameters in the faeces. Results of the principal component analysis performed between all the caecal/faecal and colonic/faecal parameters revealed that the total anaerobic and cellulolytic bacteria concentrations, as well as valerate, l-lactate and lipopolysaccharide concentrations were strongly correlated with several microbial parameters in the caecum (P<0.027; r>|0.45|) and in the colon (P<0.013; r>|0.50|). This demonstrated that faecal samples and their bacterial analyses could be used to represent caecum and RV colon hindgut microbial ecosystem in terms of variations during a change from a high-fibre to a high-starch diet, and thus could be markers of particular interest to diagnostic proximal hindgut microbial disturbances.

Soil and leaf litter metaproteomics-a brief guideline from sampling to understanding.

The increasing application of soil metaproteomics is providing unprecedented, in-depth characterization of the composition and functionality of in situ microbial communities. Despite recent advances in high-resolution mass spectrometry, soil metaproteomics still suffers from a lack of effective and reproducible protein extraction protocols and standardized data analyses. This review discusses the opportunities and limitations of selected techniques in soil-, and leaf litter metaproteomics, and presents a step-by-step guideline on their application, covering sampling, sample preparation, extraction and data evaluation strategies. In addition, we present recent applications of soil metaproteomics and discuss how such approaches, linking phylogenetics and functionality, can help gain deeper insights into terrestrial microbial ecology. Finally, we strongly recommend that to maximize the insights environmental metaproteomics may provide, such methods should be employed within a holistic experimental approach considering relevant aboveground and belowground ecosystem parameters.

Environmental factors influencing the distribution and abundance of the introduced signal crayfish in the north of Iberian Peninsula

The identification of habitat requirements of invasive species is essential to evaluate their spread and to assess the vulnerability of recipient ecosystems. We studied the distribution and abundance of the invasive signal crayfish (Pacifastacus leniusculus) in 43 sites in northern Spain and analysed the relationships with several abiotic and biotic parameters of the aquatic ecosystems. Our results indicated that the abundance of signal crayfish was positively associated with vegetation cover and negatively associated with boulders. Also, its abundance was positively correlated with water temperature, organic matter, cations (e.g. sodium), anions (e.g. sulfates) and abundance of some native fish species (Parachondrostoma miegii and Luciobarbus graellsii). We concluded that the habitat of signal crayfish is among salmonid stretches (headwaters) with cold waters and low proportion of organic debris, and among cyprinid stretches (low waters) with warmer waters which it inhabits with another invasive crayfish, the red swamp crayfish (Procambarus clarkii). Our analysis indicated that the presence of signal crayfish is limited in the uppermost stretches by lower water temperatures and a lower proportion of organic debris. The existence of a natural environmental limiting factor in upstream reaches facilitates the conservation of aquatic ecosystems and native fauna.

Construction and analysis of the EWE model of the wetland ecosystem in lake buffering zone of Zhushan Bay, China.

Lake buffering zones play a special role in spatial arrangement of the lake watershed, and the wetland in buffering zones also is of great significance in basin ecological health and lake water environmental quality. Taking Zhushanhu wetland ecosystem in the area of lake buffering zone of Zhushan Bay, Lake Taihu as the research object, the biotic components were divided into 16 functional groups to construct the Ecopath with Ecosim (EWE) model, and the characteristics and state of the ecosystem and the interrelation between the functional groups were analyzed. The results showed that the range of effective trophic level in Zhushanhu wetland ecosystem was 1-3.72, tro-phic flows were mainly concentrated in the first 4 trophic levels, and most of the food chains started from submerged plants and detritus. The total energy conversion efficiency of the wetland ecosystem was 5.1%, being lower than the "1/10 law", indicating that the current energy conversion efficiency was low. The average transmission efficiency of material throughput in the ecosystem was 4.3%. The sum of all production in the ecosystem was 2496.66 t·km-2·a-1, and the total system throughput was 10145.2 t·km-2·a-1. The characteristic parameters of ecosystem showed that the current ecosystem was at the immature stage.

Urban Wetland Characterization in South-Central New York State

Urban wetlands can serve to reduce flooding and improve water quality, yet we know little about their plant communities. Our study aims to characterize the vegetation and soil parameters of these important ecosystems, and to compare these features to those of previously sampled natural wetlands in south-central New York. Vegetation and soil characteristics were sampled in eight urban wetlands and compared to six forested wetlands, five scrub-shrub wetlands, and seven emergent wetlands. Urban sites had significantly lower species richness and a higher percent cover of invasives, including Typha x glauca, Phalaris arundinacea, and Lythrum salicaria. However, non-invasive species were also common in urban flora, including Leersia oryzoides, Ludwigia palustris, and Sagittaria latifolia. Urban wetlands had a high percentage of obligate wetland species, and most closely resembled emergent wetlands in their vegetation composition. Soil pH and soil electrical conductivity were significantly higher in urban sites, but potential net N-mineralization rates were significantly lower. Urban wetland vegetation and soil characteristics are different than those in nearby natural wetlands, and our increased knowledge of these urban ecosystems will lead to more successful restoration and creation projects.

The effects of environmental parameters on zooplankton assemblages in tropical coastal estuary, South-west, Nigeria

The present study was carried out to examine the distribution and assemblage structure of zooplankton in relation to environmental parameters of tropical coastal estuarine ecosystem impounding Bight of Benin, Nigeria. The estuarine water samples were collected between January and December, 2014 from three sampling zones (Brushpark, Open water and Wetland) then were fixed in 4% formalin. A total of twenty-eight (28) species belonging to four (4) groups were recorded in this study. These groups were rotifera, copepoda, cladocerans and ostracodas, and were all widely distributed in the three investigated zones. Higher richness, dominance and abundance indices were recorded in Zone I when compared to both Zones II and III. Cluster analysis showed five distinct species communities. The canonical correspondence analysis (CCA) showed a distinct smattering positive and negative correlation on the distribution of zooplankton indicating that the relative abundance of any species was dependent on specific environmental variables.

Ecological hydrology (ecohydrology) as a part of the aquatic ecology

The understanding of ecohydrology in Ukraine, which was formed due to a large number of detailed hydrological investigations in natural and artificial water bodies, is presented. The approach presented here focuses on one of the hydrology side of this scientific discipline that is to study hydrological processes, which are responsible for the functioning of aquatic ecosystems, vital activity of hydrobionts, bioproductivity of the aquatic environment and its quality. The main goal of ecohydrology is to develop management methods of structural and functional parameters of aquatic ecosystems. In this approach, ecohydrology is a part of aquatic ecology (hydroecology).

Optimization and evaluation of key photosynthesis parameters in forest ecosystems based on FLUXNET data and VPM model.

Gross primary productivity (GPP) plays an important role in global carbon cycle. Vegetation maximum light use efficiency (Δmax) is the key parameter for GPP simulation of terrestrial ecosystem. Based on the vegetation photosynthesis model (VPM) and the eddy covariance flux data at 40 stations from FLUXNET (179 site-years of data), we identified the key model parameters influencing the simulation of GPP with VPM through one-at-a-time (OAT) method. The cross validation method was employed to optimize the key model parameters and evaluate the model perfor-mance for global forest ecosystems. The results showed that the prediction of GPP was mostly affec-ted by Δmax, maximum temperature for photosynthesis (Tmax), and optimum temperature for photosynthesis (Topt). There were distinguishable differences for the key optimized parameters among different forest ecosystems. The optimized Δmax ranged from 0.05 to 0.08 μmol CO2·μmol-1 PAR (evergreen broad-leaved forest>evergreen coniferous forest>mixed forest>deciduous broad-leaved forest). The optimized Tmax ranged from 38 to 48 ℃,while Topt ranged from 18 to 22 ℃. With the optimized key parameters based on ecosystem types, the VPM was able to simulate the seasonal and inter-annual variations of GPP in four forest ecosystems.

Map-based prediction of organic carbon in headwater streams improved by downstream observations from the river outlet

Abstract. In spite of the great abundance and ecological importance of headwater streams, managers are usually limited by a lack of information about water chemistry in these headwaters. In this study we test whether river outlet chemistry can be used as an additional source of information to improve the prediction of the chemistry of upstream headwaters (size &lt; 2 km2), relative to models based on map information alone. We use the concentration of total organic carbon (TOC), an important stream ecosystem parameter, as the target for our study. Between 2000 and 2008, we carried out 17 synoptic surveys in 9 mesoscale catchments (size 32–235 km2). Over 900 water samples were collected in total, primarily from headwater streams but also including each catchment's river outlet during every survey. First we used partial least square regression (PLS) to model the distribution (median, interquartile range (IQR)) of headwater stream TOC for a given catchment, based on a large number of candidate variables including sub-catchment characteristics from GIS, and measured river chemistry at the catchment outlet. The best candidate variables from the PLS models were then used in hierarchical linear mixed models (MM) to model TOC in individual headwater streams. Three predictor variables were consistently selected for the MM calibration sets: (1) proportion of forested wetlands in the sub-catchment (positively correlated with headwater stream TOC), (2) proportion of lake surface cover in the sub-catchment (negatively correlated with headwater stream TOC), and (3) river outlet TOC (positively correlated with headwater stream TOC). Including river outlet TOC improved predictions, with 5–15 % lower prediction errors than when using map information alone. Thus, data on water chemistry measured at river outlets offer information which can complement GIS-based modelling of headwater stream chemistry.

Características Ecosistémicas asociadas a la actividad ganadera en Arauca (Colombia): Desafíos frente al cambio climático

En la llanura inundable de la Orinoquía colombiana (departamento de Arauca) se realizó la caracterización de cuatro tipos ecosistémicos con diferentes grados de intervención por ganadería, durante la intensa temporada seca de enero a marzo 2010: sabana de pastizal, sabana arbolada, bosque de galería y bosque conservado del piedemonte. En cada uno de ellos se evaluaron las condiciones microclimáticas (humedad y temperatura del aire), las características físico químicos del suelo (capacidad de retención de agua, capacidad de intercambio catiónico, pH, contenido de fósforo y de micronutrientes), la diversidad vegetal (riqueza y abundancia) y el potencial regenerativo (diversidad y porcentaje de germinación del banco de semillas del suelo), con el fin de establecer cuáles parámetros ecosistémicos son los más afectados por la ganadería durante la sequía, y evaluar la capacidad de regulación ambiental y el potencial de recuperación natural. Los resultados demostraron que en casi todos los aspectos el tipo ecosistémico de pastizal es ampliamente contrastante con relación a los bosques conservados del piedemonte, siendo estos últimos los lugares con mayor biodiversidad, menor variabilidad en temperatura y humedad relativa, mayor capacidad de retención de agua, mayor variabilidad topográfica que brinda sitios específicos de regeneración y contenidos más balanceados de micronutrientes en el suelo. Los bancos de semillas, que albergan propágulos que soportan la temporada seca para germinar en condiciones más favorables, fueron más diversos y abundantes en la sabana arbolada, mostrando que este ecosistema tiene mayores opciones de recuperación ecológica que la sabana de pastizal. El estudio demuestra la importancia de la cobertura arbórea en la llanura inundable, especialmente en la autorregulación ecosistémica durante temporadas climáticas desfavorables. Se recomienda la implementación de sistemas de producción ganadera que involucren el componente forestal, y la conservación de los remanentes de bosque.Palabras clave: Bosque de galería; bosque del piedemonte Orinoquía; pastizal; regulación climática; sabana arbolada; suelo; Gallery forest; piedmont forest; Orinoquía; pastureland; climate regulation; wooded savannah; soil.

Effect of yeast supplementation on hindgut microbiota and digestibility of horses subjected to an abrupt change of hays

According to epidemiological studies, abrupt change of hay is a major risk factor of equine colic. Disturbances of the microbial ecosystem can lead to colic. However, it is not known if the hay change disturbs the hindgut microbial ecosystem. This study aimed to assess the effect of Saccharomyces cerevisiae (SC) supplementation during an abrupt change of hay on the hindgut microbial ecosystem and digestibility. Six cecum and colon fistulated horses allotted in two groups were subjected to a 2×2 Latin-square design experiment. Horses received a 80/20 ratio forage/concentrate (1.3 DMkg/day/100kgBW meadow hay) diet. During each experimental period, one of the two groups was supplemented with 1g/d of Yea-Sacc preparation in the morning meal. In each experimental period, groups were first fed hay1 (88.1%DM, 62.6%NDF, 34.9%ADF, 5.3%ADL, 33.1%CF, 8.6%CP) for four weeks and then hay2 (87.5%DM, 60.6%NDF, 35.0%ADF, 5.0%ADL, 33.4%CF, 7.8%CP) for the next three weeks without an adaption period. Cecal and colonic samples were collected 4h after the morning meal 6 days before (d-6) and one (d1), eight (d8) and 15 days after (d15) the abrupt change to assess the microbial ecosystem parameters. The digestibility was also measured before (pool1: d-4 to d-1), immediately (pool2: d0 to d3) and after (pool3: d10 to d13) the hay change. There was no effect of either SC supplementation or SC supplementation×sampling day interaction on any parameter (microbial ecosystem/digestibility). In the two experimental groups, the abrupt change of hay caused at d1 a significant increase in Copy Number of Target Gene (CNTG) of Bacteroidetes (P=0.037) and a trend for increasing CNTG of Firmicutes (P=0.089) in the cecum, as well as a significant increase in total volatile fatty acids (P=0.019) and acetate concentrations (P=0.026) in the colon. At d8, a significant decrease of the colonic CNTG of Bacteroidetes was noted (P=0.019), as well as a tendency to increase for CNTG of colonic Firmicutes (P=0.056). The cecal pectinolytic bacteria (P=0.036) and colonic propionate concentration (P=0.009) significantly increased, respectively, at d8 and d15 after the hay change. The DM, OM, NDF and ADF digestibility increased significantly in pool 2 and 3 (P<0.01). Despite the close composition of the two hays, changes were measured after the abrupt hay change suggesting a sensitive response of the hindgut microbial ecosystem. Further investigations are needed to evaluate the extent to which hindgut microbial ecosystem disturbances can lead to colic and to understand how yeast could be supplemented to minimize their effect.