Transcript Presentation

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.
2003
2012
Xanthopappus subacaulis
Stellera chamaejasme
Iris ensata
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
Effective size variaton during growing season
0.7
0.6
0.5
effectsize,gm²
0.8
…on effective size of
the biomass
1
2
3
harvest
…on ADF values
…on NDF values
ADF values variaton during growing season
28
ADF,%
26
55
22
24
50
45
NDF,%
60
30
32
65
34
NDF values variaton during growing season
1
2
harvest
3
1
2
harvest
3
…on Crude Protein
Effect
of grazing
on NDF
Effect
of grazing
on ADF
Effect
of grazing
on NDF
of grazing
on ADF
Effect
of species Effect
number
on biomass
34
species number
10
15
32
30
28
26
30
24
22
0
5
24
22
50
45
5
50
45
26
ADF,%
28
ADF,%
10
spp.no
60
55
NDF,%
NDF,%
55
60
15
32
65
65
1500
1000
500
0
wet weight,g/m²
Species number variation
20
34
Effect of grazing on biomass
1
2
3
4
grazing classes
…on
biomass
wet weight
1
1 2
2 3
3 4
grazing
classes
grazing
classes
04
500
1 2
1 1000
wet
2 31500
3 4
grazing
classes
grazing
classes
…on NDF and ADF values
4
1
2
3
4
grazing classes
…on number
of species
1
Carex spp, Medicago hyspida, Potentilla
anserina, P. saundersiana, P. bifurca, Kobresia
capillifolia, Leymus secalinus,, Agropyron
crystatum
2
3
Stipa capillata, Medicago hyspida,
Stellera shamaejasme, Artemisia spp.,
Oxytropis spp, Allium cyaneum
Medicago hyspida, Poa spp., Potentilla
anserina, Geranium pratense,
Agroopyron cristatum, Stipa capillata,
Poligonum bistorta
Stipa capillata, Stellera shamaejasme,
Oxytropis spp, Heteropappus altaicus,
Atriplex spp.
4
Distribution of dry and wet
biomass
Effect of grazing on biomass
Effect of grazing on biomass
1000 1000
r²=0,39
p<0,001
1
2
500
3
4
1000
1500
6
0
0
500
wet
wet weight,g/m²
1500
wet weight,g/m²
wet
grazing classes
1000
01500
1
wet vs dry weight
1
500
2
10003
2800
2600
1500
3000
2 Altitude
3
1
3200
4
dry weight vs
grazing classes
mean height vs dry weight altitude
grazing classes
2
grazing cl
Effect of grazing
500
1000
0
08
500
500
wet
1830
5 10 10 12 15 14 20 16 25
mean.h
mean
hight
wet weight,g/m²
400
1000
300
100 500 200
0 0
wet weight,g/m²
dry
r²=0,50
p<0,001
Effect of grazing
0
r²=0,77
p<0,001
peak biomass
1500
Effect of plant hight on biomass
Growing season biomass
1500
1500
Mean hight variation
 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).