Patterns of aboveground herbage production and nutritional quality structure on semiar1d 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 allocation of biomass among organic compounds is different in the three botanical groups.

In relation to topographical gradient, production and nutritional parameters (protein, fibre content and DMD) for each botanical group show differences between the two zones of the slope. Parameters like organic composition and DMD characterize clearly the botanical fractions. The grasses are always related with high hemicellulose proportions while legumes with cellular contents. Considering the community, grasslands from the lower zones are better characterized by higher protein contents and DMD. The communities from the upper zones are characterized by high contents in cell components. The nutritional quality of communities is clearly related with the percentages of botanical fractions forming the grassland and with organic contents and dry matter digestibility as well.

Notes

Present address: Department Plant Ecology and Evolutionary Biology, University of Utrecht. P.O. Box 800, 84, 3508 TB Utrecht, The Netherlands.

Present address: Section GVK, AB‐DLO (Research Institute for Agrobiology and Soil Fertility) Bornsesteg, 65, Postbus 14, Wageningen, The Netherlands.