B. R. Vázquez de Aldana

Estimation of mineral content in natural grasslands by near infrared reflectance spectroscopy

Abstract Near infrared reflectance spectroscopy (NIRS) was tested to predict the nitrogen (N) and mineral concentration [for the elements phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn)] in natural grassland samples. The samples wrere taken from different community types according to the topographic gradient at different maturation stages and during a period of four consecutive years. A subset of 95 samples was selected on the basis of the spectral variation. Chemical values from the calibration sample set were regressed on the corresponding spectral data using a stepwise multiple regression analysis. Another subset of 75 samples was used as the validation set. Standard errors of prediction and correlation coefficients, respectively, were: 0.71 and 0.97 (N), 0.22 and 0.73 (P), 1.83 and 0.84 (K), 0.83 and 0.92 (Ca), 0.15 and 0.92 (Mg), 3.94 and 0.66 (Na), 44 and 0.84 (Mn), 19 and 0.75 (Fe), 1.01 and 0.77 (Co), and 3.9 and 0.79 ...

Patterns of aboveground herbage production and nutritional quality structure on semiarid grasslands

Abstract Botanical composition, aboveground biomass, protein, fibre content, and dry matter digestibility (DMD) were used as tools for studying the production and nutritional quality in semiarid grasslands. The study was carried out in herbaceous communities from Central‐West of Spain over a period of five consecutive years (1986–1990). The grassland typologies were mainly related to their positions in topographical gradients (slopes) which characterize the regional landscape. The mean values for the production of aboveground biomass in the communities range between 126 and 304 g/m2 which seem fitted with the possibilities of those areas. The botanical composition is different in the two zones of the slope (upper and lower) and it responds to a defined pattern. Vegetation in the lower zones is dominated by grasses and in the upper zones by forbs. The correlation between production and botanical fractions considered (grasses, legumes and forbs) is significant for the grass group. The results show also that...

Interannual variations of nutrient concentrations in botanical fractions from extensively managed grasslands

Abstract We studied interannual variations in the concentrations of N, P, K, Ca, Mg, Na, Mn, Fe, Cu, and Zn in botanical fractions from semi-natural grassland in central-western Spain. Herbage samples were collected at the ripening stage at the end of May over a 4-year period (1987, 1988, 1989 and 1991) and classified into: grasses, legumes and forbs. There was an increase in N, P and K contents from 1987 until 1991. The interannual differences in Ca, Mn, Cu and Zn concentrations showed no clear trends. However, the sampling year had no significant effect on Mg and Na contents. Grasses generally exhibited significant lower nutrient contents than legumes and forbs. Forbs had N, Ca, Mg and Cu concentrations midway between those of grasses and legumes, and higher P, K, Fe and Zn contents than legumes. The P, Mg, and Na contents in the three botanical fractions were inadequate for feeding livestock. However, the K, Mn, and Fe contents in the three botanical groups and the Ca, Cu, and Zn contents in legumes and forbs were within recommended ranges for cattle. The N contents were only adequate in legumes. These and forbs appear to be most suitable for cattle feeding on account of their mineral contents.

Non‐destructive method for determining ash content in pasture samples: Application of near infrared reflectance spectroscopy

Abstract Ash content is a useful parameter in forage and grass quality studies, but the traditional methods used to quantify this parameter are tedious and sample processing time‐consumig is. Near infrared reflectance spectroscopy (MRS) overcomes some drawbacks of the traditional methods. Measurement of a samples diffuse reflectance is rapid and non‐destructive and chemical reagents are not necessary, which is environmentally friendly. We predicted the ash content of herbage samples from semiarid grassland communities by NIRS. The samples were collected on different sites, over four consecutive years. The calibration equations generated from log 1/reflectance to predict ash content had a standard error of calibration (SEC) of 4.6 g kg‐1 and R2 of 0.88. The standard error of prediction (SEP) was 5.1 g kg‐1 and r was 0.94.

Interaction between plant genotype and the symbiosis with Epichloë fungal endophytes in seeds of red fescue (Festuca rubra)

In diverse natural habitats of Europe, plants of Festuca rubra are commonly infected by the fungal endophyte Epichloe festucae. Under several circumstances, the association between the grass and the fungus has been shown to be mutualistic. Here, we conducted an experiment to study the differences in seed germination and mortality between infected (E+) and endophyte-free plants (E–) at different temperatures (12 and 25°C) and water potentials (0 and –0.5 MPa). Three half-sib lines of F. rubra, each composed of E+ and E– seeds, and derived from infected plants from semiarid grasslands were used. Although the endophyte effect depended on the incubation condition, germination percentage was significantly greater for E– (52%) than for E+ seeds (41%). Seed germination was more inhibited by the low water potential (75 v. 24% for –0.5 and 0.0 MPa, respectively), than by the high temperature (64 v. 35% for 25 and 12°C, respectively). However, mortality was highly dependent on the interaction between plant genotype and endophyte, and between temperature and water condition. It is remarkable that while highly dependent on the host genotype, there was a clear effect of endophyte increasing seed survival, especially in those treatments that were unfavourable for germination. For example, in the more restrictive treatment (25°C and –0.5 MPa), seed survival was on average, 44 and 39% for E+ and E–, respectively. In general, the endophyte affected seed characteristics of F. rubra by reducing the percentage of germination, but simultaneously increasing seed survival.

Use of near infrared reflectance spectroscopy to assess forage quality of a mediterranean shrub

Abstract Shrubs are an important source of food for domestic livestock and wildlife in semiarid areas. This is particularly true during dry periods when forage from natural pastures is scarce and its quality is low. Cytisus multiflorus is a leguminous shrub which is endemic to the Northwestern Iberian peninsula. This species occurs in poor soils and in degraded or marginal areas. The objective of this study was to evaluate the potential of near infrared reflectance spectroscopy (NIRS) to determine quality attributes of Cytisus multiflorus as a forage feed. NIRS calibrations were developed for crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin, cellulose, hemicellulose, ash, and organic dry matter digestibility (OMD). The sample population used included different plant parts and plants of different ages, and was collected in the Spanish province of Salamanca. Calibration models were accurate for the prediction of crude protein (r 2 = 0.99; Standard error of prediction (SEP) = 3.8 g kg−1), OMD (r 2 = 0.98; SEP = 15.7 g kg−1), NDF (r 2 = 0.98; SEP = 13.3 g kg−1), ADF (r 2 = 0.94; SEP = 19.1 g kg−1), cellulose (r 2 = 0.96; SEP = 12.2 g kg−1), and ash (r 2 = 0.91; SEP = 1.1 g kg−1). The results of the lignin and hemicellulose calibrations had lower accuracy (r 2 = 0.76; SEP = 7.0 g kg−1 for lignin and r 2 = 0.88; SEP = 13.6 g kg−1 for hemicellulose). The results showed that NIR spectroscopy can be used for the rapid and accurate prediction of quality attributes in samples of the mediterranean shrub Cytisus multiflorus.

Ergovaline levels in cultivars of Festuca arundinacea

This work was funded by the “Junta de Castilla y Leon “ (CSI3/98). Beatriz R. Vazquez de Aldana was supported by a Research Contract from the Spanish “Ministerio de Ciencia y Tecnologia”.

Effect of topographic and temporal (maturity) gradients on the nutritive quality of semiarid herbaceous communities.

Abstract Five slopes representative of the “dehesa”; grassland communities in the semi‐arid zones of Central‐Western Spain (province of Salamanca) were studied. Above‐ground biomass production was recorded from April to June and the NDF (neutral detergent fibre), ADF (acid detergent fibre), hemicellulose, cellulose, lignin, and digestibility were determined in the dry matter. Principal component analysis was applied to the data. The changes with time along the growth period show a parallel effect on the three positions of the slope, although the effect tended to be greater on the middle and upper zones. There were decreases in the levels of protein, cellular content, and digestibility, and an increase in cell wall components. The variability in nutritive characteristics induced by the phenology and time changes in the communities was reflected in the first factor of analysis, whereas the topographic gradient was related to the second component.

ELEMENTAL CONTENT IN GRASSLAND OF SEMIARID ZONES: EFFECT OF TOPOGRAPHIC POSITION AND BOTANICAL COMPOSITION

Abstract Elemental composition (N, P, K, Ca, Mg, Na, Mn, Fe, Cu, and Zn) was studied in semi‐natural grassland communities of the province of Salamanca (Central‐Western Spain) under the effect of a topographical gradient (two differentiated slope positions: upper zone and lower zone) and for the main botanical groups forming these communities (grasses, legumes, and other families). In the upper positions where the proportion in weight of legumes and other families is greater than in the lower ones, the P, Ca, Fe, and Cu concentrations were higher than in the lower. For elements like N, Mg, and Zn, the zonal difference in the grass was not significant, since this was counteracted by the greater nutrient content of the lower zones and a dilution effect due to the greater production of biomass in that zone. The mean value of the K:(Ca+Mg) ratio in the grass was significantly lower (P<0.05) in the upper zone than in the lower one, and all the samples were lower than the critical value for livestock [2.2]. The...

First report of choke disease caused by Epichloë baconii in the grass Agrostis castellana.

Agrostis castellana is common in semiarid natural grasslands of the province of Salamanca, Spain. In this area, plants showing fungal stromata in their stems were observed in July of 2001. These symptoms are typical of choke disease, caused by Epichloë species in several grasses (3). In this disease, external fungal stromata develop around the leaf sheath of the flag leaf during the reproductive cycle of the plant host. As a result, the inflorescence does not emerge. In natural populations of A. castellana, less than 1% of plants showed disease symptoms, and all the stems of infected plants were sterilized by stromata. Intercellular endophytic mycelium was observed by microscopy in stem pith of diseased plants, but not on samples of 30 apparently healthy plants (1). Ergovaline, a fungal alkaloid, was not detected in lyophilized samples of infected plant tissue (2). In a fungal culture obtained from surface-disinfected leaf sheaths of a diseased plant (1), reniform conidia and conidiophores characteristic of the genus Epichloë were observed (4). To determine the fungal species, the nucleotide sequence of the ITS1-5.8SrRNA-ITS2 region and the three first introns of the beta-tubulin gene were obtained (EMBL Accession Nos. AJ490938 and AJ490939). When compared to those of other Epichloë species, these sequences identified the fungus from A. castellana as E. baconii (3). This fungus has been previously described as a pathogenic fungal endophyte in other Agrostis and Calamagrostis species (3,4). The fact that all stems of infected plants were diseased, infection incidence was low, and no alkaloids were detected in plants suggests that this grass-endophyte interaction is pathogenic and not mixed or mutualistic. References: (1) E. Clark et al. J. Microbiol. Methods 1:149, 1983. (2) N. Hill et al. Crop Sci. 33:331, 1993. (3) A. Leuchtmann et al. Mycol. Res. 102:1169, 1998. (4) J. White Jr. Mycologia 85:444, 1993.