Productive Response of Dairy Cows Fed with Different Levels of Totally Mixed Ration and Pasture

Forty multiparous Holstein cows in early lactation (66 ± 19 days) were assigned to one of four treatments that consisted in different ratios of total mixed rations (TMR) and pasture at 100% TMR (T0), 75:25 (T1) 50:50 (T2) and 25:75 (T3) over 9 weeks in autumn-winter. Measures of rumen parameters and digestion were performed on 4 additional Holstein cows in late lactation (287 days postpartum) fitted with permanent ruminal fistulae and producing 22.6 (±5.4) kg milk in a 4 × 4 Latin Square design. In T1 to T3 cows were taken to the grazing plot once they finished the pre-planned TMR intake and pasture was offered at 2 times the expected forage DM intake. Milk was analyzed for chemical composition, milk fatty acid (FA) profile and antioxidant compounds. The cows were individually weighed and body condition score (BCS) was determined. After the morning milking, blood samples were taken every 2 weeks and plasma was analyzed for glucose, urea, non-esterified fatty acids (NEFA), insulin, growth hormone (GH) and insulin-like growth factor (IGF-I). Herbage mass in pre grazing strips of pasture averaged 2540 ± 343 kg DM/ha. As TMR intake increased, production variables increased linearly excepting milk fat (3.88 g/100g) and milk protein (3.43 g/100g) contents that were not affected. Milk yield (kg/cow/d) resulted maximal in T0 (34.2) and linearly decreased (p 3-N concentration resulted higher in treatments with higher proportion of pasture. Kinetic parameters of DM and NDF digestion from pasture or corn silage were not affected. Milk FA profile and milk antioxidant quality showed unfavorably changes as TMR increased by a decrease in rumenic and linolenic acids and content of antioxidant vitamins, without effect on the atherogenicity index. Results suggested a depressing effect of the pasture on total DM and energy intake probably explained by qualitative deficiencies chemical composition of the forage and/or factors that affect animal behavior that may induce losses in body condition of high yielding dairy cows.

Effects of Supplementation with Increasing Levels of Energy Concentrate on the Productive Response and Ruminal Digestion of Dairy Cows Grazing Lucerne Pasture

The aim of the study was to determine the effect of three levels of energy concentrate intake on dry matter (DM) and energy intake, milk yield and composition, rumen environment and pasture neutral detergent fiber (NDF) digestion. Twelve Holstein multiparous cows in early lactation (69.0 ± 5 days postpartum) producing 32.8 (±4.0) kg milk were assigned to three treatments at (kg/cow day) 3.5 (T3.5), 7.0 (T7.0) and 10.5 (T10.5) kg concentrate in a 3 × 3 Latin Square design. Parameters of ruminal environment and neutral detergent fiber (NDF) digestion were obtained using 3 additional rumen cannulated cows. Concentrate was composed (as fed) by corn grain (68%), soybean meal (22%), wheat bran (8%) and a vitamin-mineral premix including monensin and thoroughly consumed. Yields (kg/cow day-1) of milk, 4% fat corrected milk (4% FCM 4%) and energy corrected milk (ECM) resulted higher (p p -1 without effects on yield of milk fat. Concentrations (g/100 g) of milk fat (3.19), protein (2.97), total solids (11.75), non-fat solids (8.60) and casein (2.40) did not differ. Milk lactose content (g/100 g) was linearly increased (p p p p p < 0.05) in T3.5 due to the increase in acetate and butyrate while the acetate: Propionate ratio remained unchanged. Pasture NDF digestion was affected as concentrate intake increased. To increase milk protein yield and reduce concentrations of N-NH3 in rumen and milk, feeding an energy concentrate at 41% of total DM intake resulted an effective tool.

Increasing Conjugated Linoleic Acid Content in Milk and Cheese after Supplementing a Blend of Crude Soybean Oil Sediment Combined with Fish Oil to Grazing Dairy Cows

The aim of the work was to improve the healthy value of milk and cheese fatty acids (FA) by feeding a mix of crude soybean oil sediment (CSOS) combined with fish oil (FO) to grazing dairy cows. The CSOS is a by-product commonly discarded after oil extraction containing 3.3% moisture, 6% total ash and 70.7% oil, locally available, comparatively economic and easy to mix with other feed ingredients. The experiment lasted 55 days from September 30th to November 23th 2018 and was carried out at the dairy farm “Gacef” provider of milk to the dairy industrial plant “Capilla Del Señor” (CDS) located at the Villa María City, Córdoba Province, Argentine. A herd of 80 multiparous Holstein cows producing 24 kg-1 milk·cow-1·day-1 was used. The cows grazed an alfalfa and an oat pasture that represented about 47% of total dry matter (DM) intake supplemented at 8.5 kg DM·cow-1·day-1 with a total mixed ration (TMR) composed (DM basis) by cracked corn grain (35.18%), whole plant corn silage (31.98%), pelletized soyben meal (17.99%), the CSOS supplement (13.85%) and FO (0.99%). The TMR was supplied by halves after each milking time in groupal feeders yielding 1.4 kg·cow-1·day-1 of the CSOS and 0.1 kg·cow-1·day-1 of FO. Before the start of lipid supplementation, milk samples (5) were obtained from the farm-tank representing the standar or reference milk (Ref-Milk). After 21 days of supplementary lipid supply, additional milk samples (5) were obtained representing the modified milk (Mod-Milk). Milk samples were analyzed for chemical composition and milk FA profile. At each time, sufficient quantities of both (Ref- and Mod-Milk) were collected for manufacturing six types of cheeses. The results were analyzed through the Student-T test for independent observations. Oil supplementation did not modify (P > 0.05) the chemical composition of milk. Concentration of butyric acid (C4:0) in milk was not affected (P < 0.858). Concentration of total saturated FA (SFAs) in Ref-Milk averaged 58.83 g 100 g-1 FA and was decreased to 49.67 g 100 g-1 FA in Mod-Milk (P < 0.0001). Monounsaturated FA (MUFAs) increased (P < 0.001) from 32.03 g 100 g-1 FA in Ref-Milk to 38.13 g 100 g-1 FA in Mod-Milk (+19.07%) whereas polyunsaturated FA (PUFAs) increased (+36.1%) from 4.71 to 6.41 (P < 0.004). The Mod-Milk showed a significant (P < 0.002) reduction (-15.3% or 5.9 g 100 g-1 FA) for the total concentration of the potentially atherogenic fraction of milk FA (C12:0 to C16:0). The atherogenic index (AI) also decreased (P < 0.012) from 1.98 in Ref-Milk to 1.42 in Mod-Milk (-28.4%). Concentration of vaccenic acid (VA, trans-11 C18:1) in Mod-Milk averaged 7.77 g 100 g-1 FA which represented a 162 % increase (P < 0.0001) over that observed in Ref-Milk (2.95 g 100 g-1). Concentration of conjugated linoleic acid (CLA, cis-9, trans-11 C18:2) in Ref-Milk averaged 1.47 g 100 g-1 FA and showed an important increase (P < 0.002) in the Mod-Milk (3.86 g 100 g-1 FA, +163%). The omega 6/3 ratio resulted lower (P < 0.012) in the Ref-Milk (2.28) compared to the Mod-Milk (2.83). Milk and cheese FA composition were highly correlated (R2 = 0.99, P < 0.0001). The Mod-Cheeses showed similar results in AI, total concentration of SFAs, MUFAs and PUFAs compared to the milk of origin. Differences in FA composition between the cheeses made with the Ref- and Mod-Milk were equivalent to those described for milks. It is concluded that supplementation with a blend of CSOS supplement and FO was an effective way to improve the healthy value of dairy products by reducing contents of SFAs, atherogenic FAs and the atherogenicity index with a concomitant increase in VA and CLA. Modifications induced in the Mod-Milk were recovered in the Mod-Cheeses. The results obtained may help to reduce saturated fat intake and fight or prevent incidence of non-communicable, cardiovascular and chronic diseases.

Occupancy of avian foraging guilds in soybean fields and borders in Entre Ríos, Argentina: responses to vegetation structure and prey resources

Background:Reconciling agriculture and biodiversity conservation is a challenge given the growing demand for agricultural products.In recent decades,Argentina has witnessed agricultural expansion and intensification affecting biodiversity and associated ecosystem services.Within agroecosystems,the level of habitat quality is critical for birds,and may depend on vegetation structure,availability of invertebrate prey,and the use of pesticides.Although the relationship between vegetation structure and avian occurrence has been widely studied,to our knowledge,there are no studies that also incorporate prey availability throughout the cycle of soybean crops in Argentina.We estimated and predicted the effects of land cover and temporal variation on the occurrence of avian foraging guilds in Entre Ríos,Argentina,in order to guide management related to potential ecosystem services provided by birds.We also estimated temporal effects of vegetation structure and insecticides on the main arthropod orders consumed by birds to evaluate prey availability.Methods:We conducted bird and arthropod surveys for 2 years along transects located in 20 randomly selected soybean fields(N=60)and their adjacent borders(N=78)throughout the crop growing season,in four seasons.We estimated avian occupancy,accounting for imperfect detection,and arthropod counts fitting generalized linear mixed models.Results:The number of native trees in field borders positively influenced the occurrence of most bird species,mainly insectivores.Granivore foliage gleaners,also were positively affected by grass height.Salliers and aerial foragers were weakly affected by distance to forest and native trees.In general,the availability of invertebrates to birds was highest during the third season.Arthropod counts in borders were greater during the last three crop stages than during the pre-sowing period.Conclusions:We found that with 10 to 15 native tree species in borders,coupled with a complex vegetation structure with shrubs and grasses,we could conserve a wide spectrum of insectivorous birds,and may contribute to the invertebrate pest control service.Vegetated field borders function as a refuge for arthropods,especially agriculturally beneficial taxa such as Hymenopterans.Finally,several groups of birds use the interior of the fields and could help control pests.

Potential for Increasing Soil Nutrient Availability via Soil Organic Matter Improvement Using Pseudo Panel Data

Fixed and random effect models were applied to a pseudo-panel data built of soil analysis reports from tobacco farms to analyze relationships between soil characteristics like soil organic matter (SOM) and soil nitrogen (N), phosphorous (P) and potassium (K) and to explore the potential for improving nutrients availability by increasing SOM content. These econometric models may account for unobserved specific characteristics such as location-specific characteristics, management strategies, farmers’ skills and preferences and environmental heterogeneity. Positive relationships were found between N, P and K availability and SOM. The random effect model reports a highly significant elasticity of N with respect to SOM of 0.75, meaning that an increase of 1% of SOM will increase soil N by 0.75%. Using this elasticity, the required SOM improvement of green manure was calculated at which costs of green manure would exactly equal benefits in terms of reduced N fertilizer use. Costs and benefits are equal if the SOM increases from 1.55% to 3.61%, which is barely achieved according to the literature. Hence, growing green manure crops to increase SOM and thereby N availability is not economically attractive. However, additional benefits may arise from SOM improvement and growing green manure crops.

Effects of Partial Mixed Rations on Production, Composition and Nutritional Value of Milk in Lactating Dairy Cows in Temperate Region of Argentina

The aim of the study was to determine the effect of supplementing an oat winter pasture with a total mixed ration (TMR) on lactation performance of dairy cows. Nine multiparous Holstein cows were used in a 3 × 3 Latin square design with three TMR: pasture ratios at 79:21 (T1), 58:42 (T2) and 33:67 (T3) on a dry matter (DM) basis. The response to the 100% TMR diet (TMR-100) was tested using an extra period of 14 days inmediately after finishing the Latin square schedule using the nine experimental cows. Total DM intake resulted higher in TMR-100 (28.2 (kg/cow·day) and decreased by 2.64 kg/cow·day in T1, 5.02 kg in T2 and 6.68 kg in T3. Yields of milk (31.2 kg/cow·day) and fat corrected milk (26.8 kg/cow·day) was similar between T1, T2 and T3. Milk yield resulted higher in TMR-100 (32.1 kg/cow·day) compared to T2 (30.7 kg/cow·day). Milk fat concentration (g/100 g) was higher in T2 (3.13) and T3 (3.20) compared to T1 (2.96) and TMR-100 (2.85) and milk fat yield did not differ. Milk protein content resulted higher in TMR-100 and T2 averaging 3.37 g/100 g compared to T1 (3.32 g/100 g). The lowest milk protein concentration was observed in T3 (3.29 g/100 g) that resulted only different to T2. Milk protein yield did not differ between T1, T2 and T3 averaging 1.03 kg/cow·day. A lower protein yield was detected in T2 (1.03) and T3 (1.00) when compared to TMR-100 (1.07). Efficiency of milk production (kg milk/kg DM intake) resulted higher in T3 (1.42) compared to T1 (1.25). Treatments that included pasture yielded a higher efficiency of milk production when compared to TMR-100 (1.13). Plasma urea concentration resulted lower in TMR-100 (33.8 mg/dl) with no significant differences for this parameter between the other treatments. Glucose plasma levels did not differ between T1, T2 and T3 but plasma non-esterified fatty acids (NEFA) gradually increased as the proportion of pasture was enhanced according to the lower energy intake. Plasma insulin levels were higher in TMR-100 and T2 whereas concentration of somatomedins (IGF-1) remained unaffected. Grouth hormone (GH) levels and the GH/insulin ratio were highly variable and not affected by treatments. Concentration of vaccenic and conjugated linoleic acids gradually increased with the inclusion of pasture in the diet. Supplementing a winter oat pasture with TMR may be a suitable strategy to maintain milk production with a high conversion efficiency but part of the produced milk could be sustained at the expense of endogenous energy mobilization. The conditions of replacing pasture for TMR in high yielding dairy cows should be defined taking into account the depressing effect of pasture on total DM and energy intake when fresh forage is included in high proportion in the diet.

Improving the Quality of Milk Fatty Acid in Dairy Cows Supplemented with Soybean Oil and DHA-Micro Algae in a Confined Production System

The objective was to reduce saturated fatty acids (SFA) and increase conjugated linoleic acid (CLA, cis-9, trans-11 C18:2), α-linolenic (cis-9, cis-12, cis-15 C18:3) and docosahexaenoic (DHA, C22:6) contents in milk from confined dairy cows in order to promote a healthier option. The work was carried out in a commercial farm (Talar) located in Laguna del Sauce, Maldonado (Uruguay). Twenty four cows were assigned to one of two treatments (12 cows per treatment) over a 6 weeks experimental period. Treatments consisted in a control total mixed ration (C-TMR) without supplementary lipids (L) or the same TMR with the addition of 0.144 kg/cow·day of algae and 0.72 kg/cow·day of soybean oil (L-TMR). Chemical composition of the TMR (44.27% DM) averaged 15.94% for crude protein (CP), 38.20% neutral detergent fiber (NDF), 20.36% acid detergent fiber (ADF), 5.56% fat, 5.30% ash and 28.6% nonstructural carbohydrate (NSCH) with 1.81 Mcal/kg of net energy for lactation (NEL). After 39 days of feeding, individual milk samples were collected during three consecutive days. From the total milk collected, 20 ml were immediately used for chemical composition (Milko Scan) and 80 ml for analysis for milk FA profile. From week 3 onwards, milk production (kg/cow·day) resulted higher (P P P = 0.43) on milk protein content (C-TMR = 3.20;L-TMR = 3.07 g/100g). Milk lactose (C-TMR = 4.86, L-TMR = 4.69 g/100g) and urea nitrogen contents (C-TMR = 21.18, L-TMR = 17.33 g/100g) tended (P cow·day, P 12:0 to C16:0 FA averaging 45.19 in C-TMR and 34.74 g/100g in L-TMR (P P 18:1 trans-9) (0.23) and C18:1 trans-10 (0.44) FA increased (P trans-11 C18:1, VA) increased from 1.08 in C-TMR to 2.56 g/100g of FA in L-TMR (P cis-9, trans-11 C18:2) increased (127%) from 0.62 in C-TMR to 1.41 g/100g FA in L-TMR milk. Content of α-linolenic acid resulted 20% higher (P P cis-9 C18:1) resulted higher (P α-linolenic).

Proximate composition and seed lipid components of “kabuli”-type chickpea (<i>Cicer arietinum</i>L.) from Argentina

Chickpea is an important pulse crop with a wide range of potential nutritional benefits because of its chemical composition. The purpose of the current work was to provide the chemical composition of “kabuli”-type chickpea (Cicer arietinum L.) developed in Argentina for nutritional purpose. Protein, oil and ash contents, fatty acid, tocopherol and mineral element compositions were studied. Among the studied genotypes, protein content ranged from 18.46 to 24.46 g/100g, oil content ranged from 5.68 to 9.01 g/100g and ash from 3.55 to 4.46 g/100g. Linoleic, oleic and palmitic acids were the most abundant fatty acids. The average oleic-to-linoleic ratio was 0.62 and average iodine value was 117.82. Tocopherols, well-established natural antioxidants, were found in chickpea seeds in relatively similar amounts across all genotypes. Mineral element analysis showed that chickpea was rich in macronutrients such as K, P, Mg and Ca. The nutritional composition of chickpea genotypes developed and grown in Argentina provides useful information for breeding programs, food marketing and consumers and establishes chickpea as component of a balanced human diet.

Milk Fatty-Acid Profile after Feeding Increasing Doses of a Mixture of Soybean and Linseed Oils to Pasture Dairy Cows

The goal was to determine the effect of growing intake of a mixture(75:25)of soybean(SoOi)and linseed(LiOi)oils on milk production and composition and milk fatty-acid(MF-A)profile in grazing dairy cows.Twenty-four Holstein cows were assigned to 4 treatments in a completely randomized design with three weeks of adaptation to oil doses and one week of experimental measurements.On a dry matter(DM)basis,cows were fed pasture(63%),energy concentrate(37%)and the SoOi LiOi oil mixture at zero(Tr0%),2%(Tr2%),4%(Tr4%)and 6%(Tr6%)of total DM intake equivalent to 0,0.36,0.72 and 1.08 kg/cow/day of the oil mixture.The oil mixture was manually mixed-up to the concentrate(7.04 kg DM/cow/day)and supplied by halves during each milking time without refusals.Pasture(P=0.49)and total DM intakes(P=0.31)were similar between treatments averaging 11.27 and 18.85 kg DM/cow/day respectively.Milk output(22.71 kg/cow/day)was not affected(P=0.46).Milk fat content reduced linearly(P<0.05)from 3.20(Tr0%)to 2.67 g/100g(Tr6%)without effects(P=0.73)on fat or fat corrected milk(4%FCM)yields.Milk protein concentration(P<0.56)or yields(P<0.11)were not affected.Lactose contents tended(P<0.08)to be higher in oil supplemented cows and milk urea nitrogen was not affected(P=0.14).The basal(Tr0%)concentration(g/100g MF-A)of totaly hypercholesterolemic MF-A(C12:0,C14:0 and C16:0)averaged 38.93 and decreased linearly(P<0.0001)with oil intake to 37.81(Tr2%),31.59(Tr4%)and 29.18(Tr6%).Levels of elaidic(trans-9 C18:1)and trans-10 C18:1 MF-A resulted low-slung in the basal(Tr0%)milk(0.21 and 0.20 g/100g MF-A,respectively)but increased linearly(P<0.0001)after oil intake reaching the maximum values at Tr6%(0.73 and 2.23 g/100g MF-A,respectively).Milk concentration(g/100g MF-A)of vaccenic acid(trans-11 C18:1,VA)averaged 3.63 in Tr0%and increased linearly(P<0.0001)with oil intake reaching 4.97,7.05 and 8.38 in Tr2%,Tr4%and Tr6%,respectively.Basal concentration of rumenic acid(cis-9.trans-11 C18:2,RA)was 2.28 g/100g MF-A and increased linearly(P<0.0001)with increased oil dose resulting in maximal plateau in Tr4%(3.88)and Tr6%(3.89).The basal atherogenic index(AI)of milk was 1.87 and linearly decreased(P<0.01)to 1.64(Tr2%),1.18(Tr4%)and 0.95(Tr6%)after oil intake.The basalΩ6/Ω3 ratio(3.57)was no different(P>0.05)from Tr2%(3.37)but was upper(P<0.05)in Tr4%(4.41)and Tr6%(4.63)remaining under the recommended value of 5:1.Taken together the results suggest that feeding a blend(75:25;SoOi)of SoOi an LiOi oils at 4%of total DM intake to grazing dairy cows maximize the milk RA content with a concomitant decrease in the hypercholesterolemic MF-A of milk maintaining a beneficial for healthΩ6/Ω3 ratio with low levels of the detrimental trans-9 C18:1 and trans-10 C18:1.

Forage offering and seasonal intake comparisons to evaluate European rabbit threat in Nothofagus forests of southern Patagonia

Background:The European rabbit(Oryctolagus cuniculus L.1758)was introduced into different regions of the world,generating significant trade‑offs that critically impacted native vegetation.Here,we evaluate the rabbit’s forage intakes in three vegetation types(forests,shrublands,and grasslands)along the four seasons in a temperate forest landscape in Southern Patagonia and discuss the potential threats over native vegetation.We formulated the following questions:(i)what is the forage offer at each vegetation type?(ii)what is the rabbit’s forage intake and how it varied across the seasons along the year?and(iii)which vegetation types and plant life forms were more used according to the rabbit’s forage intakes?Methods:We censused understory vegetation to characterize the forage offer at each vegetation type and determined seasonal dietary intakes using microhistological analysis of pellets.The plant species identified in the field were grouped according to life form classes(tree regeneration,shrubs,forbs,graminoids,orchids,ferns,bryophytes,and hemiparasites).Data were analysed through uni‑and multi‑variate analyses,determining relationships between forage offer and the rabbit’s forage intakes.Results:Forage intakes revealed changes in plant life form consumption across vegetation types,where intake pressure was considerably different for tree regeneration(p=0.001),graminoids(p=0.001),and hemiparasites(p=0.001).Besides,significant changes in consumption among seasons were detected for shrubs(p=0.001),ferns(p=0.030),and hemiparasites(p=0.002).Although many species play an important role in the rabbit’s forage intake networks(e.g.,Chiliotrichum diffusum,Holcus lanatus),the strongest intake linkages were found in exotic grasses(e.g.,Poa pratensis and Festuca sp.),native hemiparasites(e.g.,Misodendrum sp.),native shrubs(e.g.,Empetrum rubrum),and native trees(e.g.,Nothofagus sp.).The summer and autumn seasons presented higher intake compared to the winter and spring seasons.Furthermore,hemiparasites intake(e.g.,Misodendrum sp.)suggests that rabbits utilize different forage sources depending on the vegetation types.Conclusions:Rabbits regularly inhabit the forest,even though it is not their preferred vegetation type to live.Rabbit management entails isolating regions that are more favourable to intake and emphasizing the year’s season for rabbit control efforts.

Relationship between MODIS-NDVI data and wheat yield: A case study in Northern Buenos Aires province, Argentina

In countries like Argentina,whose economy depends heavily on crop production,the estimation of harvests is an elementary requirement.Besides providing objectivity,the use of remote sensing allows estimating yield in advance.Since the time of maximum leaf area in wheat corresponds with the critical period of the crop,a good relationship is expected between the Normalized Difference Vegetation Index(NDVI)and yield.The present study was carried out in the North of Buenos Aires province,Argentina.Based on the type of soil,the study area can be divided into two homogeneous subzones:a subzone with lower clay content in the southwestand a subzone with higher clay content in the northeast.Nine growing seasons(2003–2011)were studied.In the first five years,an empirical model was calibrated and validated with field-observed wheat yields and MOD13q1 product-NDVI data,whereas in the other four years,the calibrated model was applied by means of yield maps and by comparing with official yields.The MOD13q1 image corresponding to Julian day 289 showed the best fit between NDVI and yield to estimate wheat yield early.Through yield maps,better weather conditions showedhigher yields and higher soil productivity presented a greater proportion of the area occupied by higher yields.At department level,an R2 value of 0.75 was found after relating the estimation of the calibrated empirical model with official yields.The method used allows predicting wheat yield 30 days before harvest.Through yield maps,the NDVI perceived the temporal and spatial variability in the study area.

Glyphosate Dissipation in Different Soils Under No-Till and Conventional Tillage

Glyphosate is the most used herbicide in Argentina, accounting for 62% of the commercialized pesticides on the market. It is used as a weed controller in no-till systems, and it is also applied to various genetically modified crops ( e.g., soybean, corn, and cotton). Although it has a high solubility in water, it tends to adsorb and accumulate in agricultural soils. The main objectives of this work were to compare the dissipation of glyphosate and the accumulation of its metabolite aminomethylphosphonic acid (AMPA) over time in three soils from agricultural areas of Argentina under long-term management with no-till (NT) and conventional tillage (CT) practices. There were no differences in dissipation between NT and CT, indicating that the glyphosate-degrading microflora was not modified by the different tillage managements. Moreover, tillage practices did not alter the general soil properties;therefore, glyphosate bioavailability was not affected by NT or CT practice. Forty percent of the applied glyphosate was degraded within the first three days in all soils, indicating a fast initial dissipation rate. However, the dissipation rate considerably decreased over time, and the degradation kinetics followed a bi-exponential (or two-compartment) kinetic model. No differences were found between tillage practices. Dissipation was not related to the microbial activity measured as soil respiration. The fast decrease in the concentration of glyphosate at the beginning of the dissipation study was not reflected in an increase in the concentration of AMPA. The estimated half-lives for glyphosate ranged between 9 and 38 d. However, glyphosate bioavailability decreases over time, as it is strongly adsorbed to the soil matrix. This increases its residence time, which may lead to its accumulation in agricultural soils.

Improving the knowledge of plant potential biodiversity-ecosystem services links using maps at the regional level in Southern Patagonia

Background:Biodiversity supports multiple ecosystem services,whereas species loss endangers the provision of many services and affects ecosystem resilience and resistance capacity.The increase of remote sensing techniques allows to estimate biodiversity and ecosystem services supply at the landscape level in areas with low available data(e.g.Southern Patagonia).This paper evaluates the potential biodiversity and how it links with ecosystem services,based on vascular plant species across eight ecological areas.We also evaluated the habitat plant requirements and their relation with natural gradients.A total of 977 plots were used to develop habitat suitability maps based on an environmental niche factor analysis of 15 more important indicator species for each ecological area(n=53 species)using 40 explanatory variables.Finally,these maps were combined into a single potential biodiversity map,which was linked with environmental variables and ecosystem services supply.For comparisons,data were extracted and compared through analyses of variance.Results:The plant habitat requirements varied greatly among the different ecological areas,and it was possible to define groups according to its specialization and marginality indexes.The potential biodiversity map allowed us to detect coldspots in the western mountains and hotspots in southern and eastern areas.Higher biodiversity was associated to higher temperatures and normalized difference vegetation index,while lower biodiversity was related to elevation and rainfall.Potential biodiversity was closely associated with supporting and provisioning ecosystem services in shrublands and grasslands in the humid steppe,while the lowest values were related to cultural ecosystem services in Nothofagus forests.Conclusions:The present study showed that plant species present remarkable differences in spatial distributions and ecological requirements,being a useful proxy for potential biodiversity modelling.Potential biodiversity values change across ecological areas allowing to identify hotspots and coldspots,a useful tool for landscape management and conservation strategies.In addition,links with ecosystem services detect potential synergies and trade-offs,where areas with the lowest potential biodiversity are related to cultural ecosystem services(e.g.aesthetic values)and areas with the greatest potential biodiversity showed threats related to productive activities(e.g.livestock).

Seed bank dynamics of an invasive alien species, Helianthus annuus L.

形成持久种子库的能力是预测物种在新区域成功建群的最佳指标之一。野生向日葵(Helianthus annuus L.)原产于北美,干扰促进了其种子库的形成,并对本地种群的建立和延续起着关键作用。然而,种子库在入侵种群的建立和延续中所起的作用尚不清楚。在本研究中,我们评估了种子库和干扰对几种向日葵生物类型(采集于阿根廷荒地生境中的野生向日葵、野生农田野生向日葵与作物向日葵自然杂交种,以及商业品种的后代)的建立和适应性,以及土壤中种子持久性的作用。在种子库试验中,我们评估了上述材料两年在干扰和未干扰条件下的出苗率、成活率到繁殖率、出苗成活率、每株花序数和每块地的花序数;在种子埋藏试验中,我们评估了其种子在四个春季(6个月、18个月、30个月和42个月)土壤中的持久性。研究结果表明,总体而言,幼苗在生长期(冬季)出苗较早,且受到干扰促进,尤其是第一年。尽管如此,在两种情况下,每块样地的花序数是相近的,尤其是荒地生境中。第二年,种子库出苗率较低,但成活率较高。在种子掩埋实验中,观察到遗传差异,荒地和野生生境中种子持久性达到42个月,而商业品种后代的种子持久性不超过6个月。在这两项实验中,农田野生型和商业向日葵品种后代生物型表现出一种中间行为。结果表明,野生向日葵和作物野生向日葵杂交种均能在其生长范围之外形成持久的种子库,且干扰可能有助于其在新区域的建立。

Suitable conditions for natural regeneration in variable retention harvesting of southern Patagonian Nothofagus pumilio forests

Background:Variable retention(aggregated and dispersed retention)harvesting proposed for Nothofagus pumilio was designed for timber purposes and biodiversity conservation.Harvesting by opening canopy generates different microenvironments and creates contrasting conditions for seedling establishment,growth,and eco-physiology performance due to synergies(positives or negatives)with biotic and abiotic factors.This study evaluated the regeneration in different microenvironment conditions within managed stands during 5 years after harvesting.Remnant forest structure after harvesting and different microenvironments were characterized in managed stands,where 105 regeneration plots were measured(3 stands×7 microenvironments×5 replicas).We characterized the seedling bank,as well as growth and ecophysiology performance of the regeneration.Univariate and multivariate analyses were conducted for the comparisons.Results:Microenvironments offered different environmental conditions for natural regeneration(soil moisture and light availability).Seedling under debris and dicot plants showed better eco-physiological performance,establishment,and growth than plants growing under monocots or located in the dispersed retention without the protection of other understory plants.The most unfavorable microenvironment conditions were high canopy cover of remnant trees(inside the aggregates or close to trees in the dispersed retention)and heavily impacted areas(skidder extraction roads).Conclusions:Favorable microenvironments in the harvested areas will improve the natural recruitment,growth,and eco-physiology performance of the natural regeneration after harvesting.It is necessary to develop new silvicultural practices that decrease the unfavorable microenvironments(e.g.,road density or excessive woody accumulation),to assure the success of the proposed silvicultural method.

Knowledge arising from long-term research of variable retention harvesting in Tierra del Fuego: where do we go from here?

Nothofagus pumilio forests in Tierra del Fuego are the southernmost forests in the world,where extreme climate conditions represent a challenge to attain sustainable forest management.Retention forestry was proposed as an alternative to increase the species conservation in managed stands.Here,we synthetized results related to the implementation of a variable retention harvesting based on a combination of aggregate patches and dispersed retention during the last 18 years comparing with other silviculture proposals(e.g.,shelterwood cuts)and control treatments(primary unmanaged forests).We summarized the results for(i)sawmill operations,(ii)timber yield,(iii)overstory stability,(iv)forest structure,(v)microclimate and natural cycles,(vi)natural regeneration dynamics(flowering,seeding,foraging,recruitment,growth,and mortality),and(vii)biodiversity(mammals,understory plants,mistletoes,birds,arthropods,mosses,lichens,and fungi).In general,aggregate patches maintained forest structure and micro-environmental variables,and slightly increased biodiversity and forest reproduction variables compared to unmanaged primary forests.On the contrary,dispersed retention decreased forest structure variables and greatly increased biodiversity(richness and abundance)when it was compared to unmanaged primary forests.Ecological conditions are influenced by variable retention harvesting,but direction and magnitude of the effect depend and differ according to retention types.Besides this,biodiversity taxa greatly differed among groups depending on retention types.In general,the species assemblages in aggregate patches were similar to those found in primary unmanaged forests,while they were significantly modified in the dispersed retention.This occurred due to(i)local extinction of some original species,(ii)the introduction of native species from the surrounding environments,or(iii)the invasion of exotic species.This silvicultural method has been a useful tool to conserve biodiversity and ecosystem functions,approaching to the balance between economy,ecology,and social requirements in the managed areas.