The mechanism of productivity formation of alpine meadow ecosystem
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Transcript of The mechanism of productivity formation of alpine meadow ecosystem
The mechanism of productivity formation of alpine meadow ecosystem
Dr Xinquan Zhao
Northwest Plateau Institute of Bi
ology, The Chinese Academy of
Sciences, Xining, 810001
Haibei Research Station
Environmental conditions of the
research area
The Haibei alpine meadow ecosystem research
station is located with N latitude 3729'-3745' a
nd E longitude 10112'-10123'.
The altitude of area is 2900 - 3500 meters. It ha
s a continental monsoon climate, with severe a
nd long winters and short cool summers.
The average air temperature is -1.7 . ℃
Average annual precipitation ranges from 426
to 860 mm, 80% of which falls in the short sum
mer growing season from May to September.
Vegetations and Animals
Alpine meadow, dominated by Kobresia hu
milis and various grasses and forbs (depend
ing on grazing density) are widely distribut
ed in this region along the valley floor.
The shrub, Potentilla fruticosa are joined by
shrubby Salix species are locating on the no
rth hill.
The region marsh vegetation consists prima
rily of Kobresia tibetica and Pedicularis long
iflora.
Vegetations and Animals
The higher shrub lands on
the mountains surrounding the
valley are common summer
grazing lands. The meadow
vegetation is grazed in winter
and is privately owned. Sheep and yaks, the majorherbivorous animals in the
region, live on herbage, which
varies greatly with seasons.
Fig. 2 Seasonal Dynamics of Standing Crop Biomass and Crude Protein Content
0
50
100
150
200
250
300
Month
Stand
ing C
rop Bi
omass
(g/m
)
0
2
4
6
8
10
12
14
16
Standing Crop
Protein
Crud
e Prot
ein Co
ntent
(%)
0
500
1000
1500
2000
2500
3000
3500
May J une J ul y August September
Aboveground Bel owground
Fig. 1 The biomass of Kobrisa humilis meadow during growth season
Biom
ass
(g/m
2)
Fig.4 Changes of sheep live weight of different ages
0
10
20
30
40
50
60
70
80
Months
Live
-weig
ht (k
g)
Table 1 the ratio of herbage consumption to kilogram carcass of different ages of sheep
Age (year) 1 2 3 4 5 6 7
Herbage consumption(HC, kg)
738
2700
4830
6060
7740
9420
1111
0
Carcass weight (CW, kg)
7.6 15.4 21.3 27.2 29.2 30.7 28.5
HC/CW 96.3
175.2 226.4 223.2 265.4 306.4 391.5
Fig. 5 The Consist of Biomass of Alpine MeadowUnder Different Grazing Densities
0
10
20
30
40
50
60
5.3 4.43 3.55 2.68 1.8
Grazing density (sheep/ha.)
Con
sist
of
Bio
ma
ss(%
)
Sedge Grasses Forb Shrub Litter
Fig. 6 The bimass of zokorat different stocking rates
0
500
1000
1500
2000
2500
3000
3500
5.3 4.43 3.55 2.68 1.8
Stocking rate(sheep/ha)
Bio
mas
s (g
wet
wei
ght
ha)
The monthly patterns of biomass changes of the plants are significantly different (P< 0.05) for various plants. The seasonal pattern showed that maximum (80%) above-ground production occurred during July to September when temperature and precipitation are most favorable for plant growth.
The ratio of herbage intake and live weight gain is very low due to the imbalance of herbage supply, both quantity and quality.
During the cold season, which lasts for more than 7 months, livestock live mainly on standing dead grasses and the livestock body weights loss is 50% to 80% of body weight gain during the warm season.
Conclusions
Case study 1Carbon flux in the alpine meadow (Kobresia humilis) ecosystem
Fig.5 Comparison of net CO2 flux (Fc) on ecosystem as a funciton of net radiation (Rn) on clear day(14 August) and cloudy day (29 August)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 100 200 300 400 500 600 700 800
Rn (w m-2)
Fc
(mg
m-2
s-1
)
Cloudy day
Clear day
Fig.6 Relationship between net CO2 flux (Fc) and air temperature (Ta) under the high solar radiation
(Rn>550w m-2) on clear day (14 August)
R2 = 0.4099
0.5
0.6
0.7
0.8
0.9
1.0
15 16 17 18 19 20 21 22 23 24
Ta ( C)
Fc
(mg
m-2
s-1)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
0:00 2:00 4:00 6:00 8:00 10:0012:0014:00 16:0018:0020:0022:00 0:00
Time
Fc
(mg
m-2 s-1
)-200
0
200
400
600
800
1000
1200
Rn
(w m-2
)
8/14 Fc8/14 Rn
Clear daya
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
0:00 2:00 4:00 6:00 8:00 10:0012:0014:0016:0018:0020:0022:00 0:00Time
Fc
(mg
m-2 s-1
)
-200
0
200
400
600
800
1000
1200
Rn
(wm-2
)
8/29 CO28/29 Rn Cloudy dayb
Fig.4 Daily variation of net radiation (Rn) andCO2 flux (Fc) on clear day and cloudy day
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00
Time
VP
D (
KP
a)
-5
0
5
10
15
20
25
30
Ta (
℃ )
8/14 VPD
8/14 Ta
8/14 Ts (5cm)
Clearday
Fig.7 Daily variation of air temperature (Ta) and vapor pressure deficit (VPD) at 220 cm on clear
day (14 August) and cloudy day (29 August)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00
Time
VP
D (
kP
a)
-5
0
5
10
15
20
25
30
Ta (
C)
8/29 VPD
8/29 Ta
8/29 Ts(5cm)
Cloudy
Ecosystem Location NEE
( gCO2m-2day-1)
Canopy height
(cm)
Leaf area index
(m2.m-2)
Reference
Alpine meadow
(Qinghai, China)
37º 29'N 101º 12'E
Al. 3250m
21.23 DOY 233
2.65 DOY 275
30 Ca.3 ?
C4-dominated tall grass prairie (KS USA)
39º 12'N, 396º 35'E
Al. 324m
17.8 DOY 226
-10.3 DOY290
40 1.54 Ham & Knapp (1998)
Larch forest
(Tomakomai, Japan)
42 44'N
141 31'E
115-140m
35.2-44.0
(June)
18-20 - Yamamoto et al. (2001)
Temperate deciduous forest
(Takayama, Japan)
36º 8'N,
137º 25'E
1420m
0.184 (1995) ~ 0.485 (1998)
Yearly average
15-20 3.5
trees
Ca.2.0
Bamboo
Yamamoto et al. (2001)
Net Ecosystem Exchange of CONet Ecosystem Exchange of CO22
Some preliminary conclusions
The alpine meadow exhibited a fairly high daily Fc during the growing season as compared with other similar ecosystem. The decrease of Fc under the high radiation suggests the potential importance of photoinhibition and/or ecosystem respiration in the meadow. Further detailed investigation is needed to evaluate the carbon budget for the unique ecosystem.
Case study 2CLIMATIC AND GRAZING CONTROLS ON VEGETATIVE
ABOVEGROUND BIOMASS
30m
30m
O O O O
O O O O
O O O O
O O O O
40 cm
1.48m
meadow habitat (winter rangeland)
shrub habitat (summer rangeland)
High Graze History Site
Treatments:
* control
* chamber (warm)
* clip (graze)
* chamber x clip
Within site plot setup
Low Graze History Site
Open top chamber
Experimental Design
*graze control
The International Tundra Experiment (ITEX)Arctic and Subarctic Field Sites
Air Temperature – Treatment EffectsGrowing Season, All Sites
NO CLIP CLIP
AIR
TE
MP
ER
AT
UR
E
(o C
)
0
2
4
6
8
10
NO CHAMBER CHAMBER
NO CHAMBER CHAMBER
* ** *
(Klein, Xin-quan, Harte, unpublished data)
Soil Temperature – Treatment EffectsGrowing Season, 3 Sites
SO
IL T
EM
PE
RA
TU
RE
(o C)
0
2
4
6
8
10
NO CHAMBER CHAMBER
*
* *
(Klein, Xin-quan, Harte, unpublished data)MEADOWSHRUB
Soil Moisture – Treatment EffectsGrowing Season, All Sites
NO CLIP CLIP
GR
AV
IME
TR
IC M
OIS
TU
RE
(%
)
0
10
20
30
40
50
NO CHAMBER CHAMBER
Control Plots Only - Site Comparisons
0
50
100
150
200
250
300
350
400
450
500
High Graze Low Graze High Graze Low Graze
shrub
sedge
forb
grass
MEADOW SHRUB
dry
wei
ght (
g/m2
)
(Klein, Xin-quan, Harte, unpublished data)
Chamber Effects on Total AG Vegetative Biomass (2001)
NO CLIP CLIP0
50
100
150
200
250
300
NO CHAMBERCHAMBER
LOW & HIGH GRAZE MEADOWS
LOW GRAZE SHRUBLAND
HIGH GRAZE HISTORY
SHRUBLAND
* * *
Dry
wei
ght b
iom
ass
(g/m
2)
(Klein, Xin-quan, Harte, unpublished data)
Low Grazing History Total Biomass(minus sedge)
050
100150200250300350400450
shrub meadow
dry
wt
(g/m
2)
control
clip
chamber
chamber x clip
Low Grazed Shrub Site soil carbon
0
2
4
6
8
10
12
control clip chamber chamber x clip
g c
arb
on
/ g
so
il x
10
0
SpeciesAltitude
(m)
T(℃) CP(%)( ±SD)
EE (%)( ±SD)
Correlation analyses
T1-2 T3-4 T1-2 and CP T3-4 and CP T1-2 and EE T3-4 and EE
Festucaovina
3 800 7.50 7.01 9.96 ± 1.35 3.60 ± 1.40
r = -0.927 4P< 0.01
r = -0.961 4P< 0.01
r = -0.940 6P< 0.05
r = -0.915 8P< 0.05
3 600 7.84 7.33 8.97 ± 0.66 3.68 ± 0.20
3 400 8.56 7.69 8.90 ± 1.46 3.41 ± 0.35
3 200 9.19 8.25 7.90 ± 0.73 3.22 ± 0.10
Poaannua
3 800 7.50 7.01 10.49 ± 1.32 4.17 ± 0.45
r = -0.700 5P> 0.05
r = -0.728 2P> 0.05
r = -0.996 3P< 0.01
r = -0.993 3P< 0.01
3 600 7.84 7.33 8.35 ± 1.40 4.11 ± 1.42
3 400 8.56 7.69 8.48 ± 0.73 3.95 ± 0.55
3 200 9.19 8.25 8.27 ± 0.06 3.77 ± 0.25
Koeleriacristata
3 800 7.50 7.01 8.87 ± 0.48 4.09 ± 0.05
r = -0.160 6P> 0.05
r = -0.138 6P> 0.05
r = -0.947 9P< 0.01
r = -0.911 9P< 0.01
3 600 7.84 7.33 7.13 ± 0.58 3.91 ± 1.01
3 400 8.56 7.69 6.87 ± 0.67 3.45 ± 0.71
3 200 9.19 8.25 8.3 ± 1.18 3.43 ± 0.09
3 600 7.84 7.33 11.38 ± 2.92 4.19 ± 0.41
3 400 8.56 7.69 9.72 ± 2.28 4.14 ± 0.25
3 200 9.19 8.25 9.90 ± 1.61 3.98 ± 0.21
Temperature and CP, EE contents of herbage grown at different altitudes
SpeciesAltitude
(m)
T(℃)ADF (%)( ±SD)
ADL (%)( ±SD)
Correlation analyses
T1-2 T3-4
T1-2 and
ADF
T3-4 and
ADF
T1-2 and
ADL
T3-4 and
ADL
Festucaovina
3 800 7.50 7.01 35.77 ± 1.27 8.62 ± 0.96
r = 0.864 9P< 0.05
r = 0.857 5
P< 0.05
r = 0.961 0
P< 0.01
r = 0.935 5P< 0.01
3 600 7.84 7.33 39.69 ± 1.41 10.17 ± 1.25
3 400 8.56 7.69 41.67 ± 1.63 12.80 ± 1.48
3 200 9.19 8.25 41.74 ± 1.45 13.25 ± 1.90
Poaannua
3 800 7.50 7.01 32.53 ± 1.58 7.60 ± 1.28
r = 0.963 9P< 0.01
r = 0.958 1
P< 0.01
r = 0.991 9
P< 0.01
r = 0.969 4P< 0.01
3 600 7.84 7.33 35.12 ± 1.23 8.20 ± 1.28
3 400 8.56 7.69 37.28 ± 1.22 10.88 ± 1.59
3 200 9.19 8.25 38.49 ± 1.24 12.18 ± 0.87
Koeleriacristata
3 800 7.50 7.01 43.65 ± 1.87 14.72 ± 0.96
r = 0.954 9P< 0.01
r = 0.914 9
P< 0.05
r = 0.906 5
P< 0.05
r = 0.873 5P< 0.05
3 600 7.84 7.33 44.39 ± 1.65 16.57 ± 1.39
3 400 8.56 7.69 47.98 ± 1.33 19.26 ± 1.30
3 200 9.19 8.25 48.30 ± 2.36 18.96 ± 1.39
3 600 7.84 7.33 30.94 ± 1.49 6.32 ± 1.53
3 400 8.56 7.69 37.08 ± 1.89 7.41 ± 1.06
3 200 9.19 8.25 36.43 ± 1.81 8.21 ± 1.42
Temperature and ADF, ADL contents of herbage grown at different altitudes
Conclusions Our results suggest that the response of AG biomass to warming is mediated by habitat type and site grazing intensity history. The warming-induced reduction in plant species richness is consistent across habitats and site grazing histories.
There were significant downtrends in crude protein, fat and nitrogen free extract contents of herbage along with the increase of temperature. It had a positive correlation between temperature and content of constructed carbohydrates
Case study 3
The influence of enhanced UV-B radiation on alpine meadow
0
2
4
6
8
S. superba G. straminea
Ph
oto
syn
thet
ic O
2 E
vo
luti
on r
ate
( m
ol
O 2 m
-2 s
-1)
ambient UV-B
enhanced UV-B
Fig. 1 Effects of enhanced UV-B radiation on photosynthetic O2
evolution rate of S. superba and G. straminea in K. humilismeadow. There was significant difference between ambient UV-B andenhanced UV-B treatment appeared only in S. superba . n=5, P <0.05.
0
2
4
6
8
S.superba G.straminea
Net photo
synth
esi
s ra
te
( m
ol C
O 2 m
-2 s
-1)
ambient UV-B
enhanced UV-B
Fig. 2 Effects of enhanced UV-B radiation on net photosynthesis rate ofS. superba and G. straminea in K. humilis meadow. The value aremeans ± SD. There was significant difference between ambient UV-B andenhanced UV-B treatment appeared only in G. straminea n=10, P<0.05.
Conclusions
Some species were exposed to a UV-B density 15.80 kJ/m2 every day, simulating a nearly 14% ozone reduction during plant growing season. The results showed both net photosynthetic rate and photosynthetic O2 evolution rate were not decreased after long period of treatment with enhanced UV-B radiation
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