Seasonal variation of feed values in arid mountain grasslands under grazing impact in Qilian Shan, NW China

Qilian Mountains are placed in between Qinghai and Gansu provinces of North West China. Being a northern outlier of Kunlun Mountains, they borders with Tibetan Plateau. Qilian Mountains belongs to semi-arid dryland where precipitation and temperature – are two main factors determining vegetation cover - show a distinct vertical gradient Strong differentiation of vegetation on North-facing slopes (mostly spruce forest -Picea crassifolia) and dry South-facing slopes with sparse vegetation.

to evaluate the variation in pasture quality and its dependence from environmental and landscape-related factors as well as from management characteristics (vegetation inventories). to assess grazing-induced and spatially differentiated changes in vegetation patterns regarding to species composition, productivity and grazing value. The objective of the research was: to examine feed values of spring/autumn and summer pastures with subject to harvest time (1) and grazing intensities (2) along the altitudinal gradient and to examine if grassland ecosystem suffer under degradation due to continues grazing and trampling pressure.

Stellera chamaejasme Iris ensata Xanthopappus subacaulis

 For grazing value estimation was developed applied range condition scale (visual estimation scale and complex degradation index)  Productivity: 2-years data on biomass wet and dry weight (235 samples), among them 115 samples were used in analyses for the feeding values (ADF, NDF, ADL) and inorganic content (macro and tracing elements) Du Toit has suggests to estimated chemical parameters (TDM, ADF, K, Mg, Ca, N, P) of each of the forage species in order to model the forage values for each specie presented in the pasture community by multiplying with spread total cover value to get the agronomic value of grazing index.

ADF – Acid Detergent Fiber – the amount of indigestible forage. NDF – Neutral Detergent Fiber – the amount of forage which could be digested CP = Crude Protein = Nitrogen x 6,25 Effective size - amount of biomass consumed by herbivores. Effective size = (wet weight – dry weight)/ wet weight

Effect of harvest time …on effective size of the biomass …on NDF values…on ADF values …on Crude Protein

…on biomass wet weight …on NDF and ADF values …on number of species

Carex spp, Medicago hyspida, Potentilla anserina, P. saundersiana, P. bifurca, Kobresia capillifolia, Leymus secalinus,, Agropyron crystatum Medicago hyspida, Poa spp., Potentilla anserina, Geranium pratense, Agroopyron cristatum, Stipa capillata, Poligonum bistorta Stipa capillata, Stellera shamaejasme, Oxytropis spp, Heteropappus altaicus, Atriplex spp. Stipa capillata, Medicago hyspida, Stellera shamaejasme, Artemisia spp., Oxytropis spp, Allium cyaneum

Distribution of dry and wet biomass wet vs dry weightmean height vs dry weight dry weight vs altitude r²=0,77 p<0,001 r²=0,50 p<0,001 r²=0,39 p<0,001

Median concentrations for the macro elements during growing season were P 1.470, Ca 7.97, K 18.58, Mg 2.51, S 2.21 in g/kg DM, and the trace elements were Mn 0.07, Fe 1.44, Zn in g/kg DM. Median content of feed values was NDF 55.31%, ADF 27.45%, ADL 5.69%, CP 14.50% and median content of DM gm² There was no significant difference in seasonal variation of most mineral concentrations, except K (p=0,048) and Zn (p=0,0002), whereas feed values were differing significantly between harvests (p<0,05). Among grazing classes feed values were also significantly different (p<0,01), as well Zn, P and S content. No linearity was observed in relationship between feeding values and grazing classes, although mean height of the standing biomass showed linear relation with grazing intensities (R²=0.35, p=0,008).