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Seasonal Variation of Feed Values in Arid Mountain Grasslands under Grazing Impact in Qilian Shan, NW China

This study evaluates the variation in pasture quality in the Qilian Mountains and assesses grazing-induced changes in vegetation patterns. It also examines the feed values of pastures and the effects of harvest time and grazing intensities.

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Seasonal Variation of Feed Values in Arid Mountain Grasslands under Grazing Impact in Qilian Shan, NW China

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  1. Alina Baranova, PhDcandidate, working group Prof Dr.UdoSchickhoff, Department of Physical Geography, University of Hamburg, Germany Shun Li Wang, Academy of Water Resource Conservation Forest of Qilian Mountains (AWRCFQM), Zhangye, Gansu Province, China Seasonal variation of feed values in arid mountain grasslands under grazing impact in Qilian Shan, NW China

  2. 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 drylandwhere 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 -Piceacrassifolia) and dry South-facing slopes with sparse vegetation.

  3. Mountain pasture areas (grazing by sheep and goat). Altitude range:2600-3000 m.

  4. Sub-alpine pasture areas (mostly grazed by yak, also sheep and goat). Altitude range:2900-3300 m.

  5. Aims Objective • 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 tramplingpressure.

  6. Succession in mountain grassland: abundance of dominant species, registered in year 2003 and 2012. 2003 2012

  7. Xanthopappussubacaulis Iris ensata Stellerachamaejasme

  8. Methods • 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. Sampling above ground biomass on heavily grazed site.

  9. Feed values • 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 consumedby herbivores. Effective size = (wet weight – dry weight)/ wet weight

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

  11. Effect of grazing …on biomass wet weight …on NDF and ADF values …on numberof species

  12. Grazing classes and species composition 1 Carex spp, Medicagohyspida, Potentillaanserina, P. saundersiana, P. bifurca, Kobresiacapillifolia, Leymussecalinus,, Agropyroncrystatum 3 Stipacapillata, Medicagohyspida, Stellerashamaejasme, Artemisia spp., Oxytropisspp, Alliumcyaneum 2 Medicagohyspida, Poa spp., Potentillaanserina,Geranium pratense, Agroopyroncristatum, Stipacapillata, Poligonumbistorta 4 Stipacapillata, Stellerashamaejasme, Oxytropisspp, Heteropappusaltaicus, Atriplex spp.

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

  14. Conclusions • 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 0.052 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 126.82 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).

  15. Thank you for attention!

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