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FAO PLANT PRODUCTION AND PROTECTION PAPER - 162

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6.4  BHUTAN - GRASSLAND SURVEY AND INTEGRATED PASTURE DEVELOPMENT IN THE HIGH MOUNTAIN REGION (TCP/BHU/4505)

6.4.1  Introduction

The purpose of the Grassland Survey and Integrated Pasture Development Project was to provide objective information on the status and development possibilities of the grazing lands of Bhutan (FAO, 1987). This was necessary because the pasture in the upper temperate and sub-alpine zones was considered to be increasingly in "very poor condition, composed of inferior grasses and herbs, and lacking productive legumes." The high altitude pastures were used by yaks in the summer and the mid-altitude zones had a double role, being grazed by yaks in winter and cattle in summer.

Specific activities of the project included:

It was realised at the outset that a region-wide survey would only produce superficial information about the nature and complexity of the grasslands. Attention was therefore directed to detailed surveying of contrasting, but representative, areas of the upper temperate and sub-alpine grasslands.

Detailed surveys of three representative areas were completed. The sites were at Soi Yaksa (north Paro), Chele La (west Paro) and Pele La (between Wangdi Phodrang and Tongsa). The data highlighted the differing character of each area because of variations in climate, pastoral resources and livestock regimes. It followed that development opportunities would also differ between areas. In all areas, emphasis was placed on development possibilities that were low cost, consistent with the prevailing climate and soil conditions, and compatible with the abilities and aspirations of the herders. Lack of local information on species suitability and pasture improvement were addressed by a series of field trials at Thongbu, Shu Chu, Chele La and Pele La, and at the Serbithang Temperate Fodder Research Centre.

While three areas were surveyed during the project (Soi Yaksa, Chele La, and Pele La), for the purposes of this case study the results relating only to Soi Yaksa will be described.

6.4.2  Methodology

Criteria

The survey methods were chosen for their relevance to the vegetation types, consistent with the objectives of the survey, and for their suitability for completion in the time available. They were also tailored to the local staff resources, so that the programme could easily continue after the project. Statistical analyses of grassland survey data were kept to a minimum, with most results being presented in summary tabular form, or as graphic representations. Data presentation was also designed so that inter-year and inter-survey area comparisons could easily be made.

Development possibilities were assessed in relation to environmental, technical, cultural and economic conditions, and not necessarily based on the maximum improvements theoretically possible. The options would be considered a first step in a continuing development programme. The extensive grazing areas, typical of much of the project zone, had inherently low soil fertility and were at the climatic limits of pasture growth. The cost of increasing livestock production through manipulating ("improving") such an extreme environment is invariably prohibitive, so it was considered prudent to work within their natural limits.

It was accepted that improved grazing management could result in improved productivity and condition, but it would be very difficult to implement such changes in the project zone. The main constraints were herder understanding, existing stock ownership and grazing rights, and the extent to which traditional livestock management was an integral part of the culture. Options requiring changes to traditional livestock management were given lower priority. Pasture selection trials were designed to identify crops according to the following criteria: production advantages over existing vegetation; adaptation to "native" soil fertility; ability to compete against natural vegetation; tolerance of mismanagement and relatively high grazing pressures; and ability to be introduced using simple, cheap methods.

Grassland survey

The primary unit of the surveys was a "land unit," an area of relatively homogenous topography and vegetation, such as a valley slope with a particular aspect, or a basin. For each land unit a range of both subjective and objective information was compiled. Firstly the unit was marked on a 1:50 000 topographical map, then estimates of the following were recorded:

  1. Percent cover of grassland, scrub land, forest and rocky bluffs/scree.
  2. Degree of grazing and livestock type.
  3. Degree of current erosion or potential erosion.
  4. Development potential.
  5. General list of plant species.
  6. Area, slope, aspect and altitude as interpreted from maps.

Within each land unit, a number of strategically placed, representative transect sites were established. It was not considered practicable to select the sites randomly because time was not available to record the high number of sites required to ensure adequate sampling and representation of the land unit. The "representative site" method yielded data of adequate detail, required fewer sites and was generally faster. The number and location of transect sites were chosen according to total area and degree of heterogeneity of the land unit. At each transect site, subjective estimates were made of ground cover (vegetation, rock/scree and bare soil), estimates of standing and annual DM production, degree of utilization, and average grass and forb height. Slope, aspect and altitude were also measured at each transect site.

Of the many standard techniques available for detailed measurement of the vegetation, the most common are point analysis and quadrat analysis. Both offer simple techniques for making detailed records of plant species occurrence. Point analysis is more time consuming and can be difficult in high vegetation, particularly at windy sites. Neither technique is suitable for recording the plant species height distribution. This was an important consideration since forest and scrub land were to be measured in addition to short grasslands, so the forage had a significant height distribution.

A technique known as height-frequency analysis based on that described in the 1960s (Scott, 1965) was adopted as the standard technique of transect measurement. This method was relatively rapid, suited to all vegetation types of the survey area, offered an indicator of relative biomass of species or groups of species, and recorded species height distribution.

The procedure at each transect site was as follows: a 50-m tape was first laid out across the contours (i.e. up slope) to form the transect, then, at 1-m intervals, ground cover was measured using a single point technique. Plant species occurrence was recorded within 5-cm "cubes" defined by a height-frequency frame in a vertical column to a height of 2 m. Species occurring above 2 m were also noted under the classification "canopy species." During subsequent data analysis, land units of similar plant species occurrence were grouped or classified using Community Coefficients and Cluster Analysis.

Constraints to the interpretation of the vegetation data included the fact that measurements were for a particular time of year only, and that the species abundance and height-frequency profiles differed according to season. Plant identification in the field was often difficult, particularly in heavily grazed areas and after freezing, about mid-October. Information on plant growth seasons and livestock grazing patterns, obtained during interviews, was used to reduce the shortcomings of single time records.

All plant height-frequency and ground cover data were analysed using a computer programme (SPPANAL). Soil samples were collected at each transect site for laboratory analysis. Extensive collections of botanical specimens (over 250 samples) were made to provide a reference base for plant identification and data analysis.

Livestock management survey

The livestock survey relied almost entirely on interviews. The main questions asked of the herders related to:

Grazing management was recorded on standard sheets, enabling a composite of year-round patterns to be compiled. This information included livestock numbers, grazing location and duration. Verification of information was done by cross questioning and by field checks at the time of survey.

Integration of forage and livestock resources

Analysis of the interrelationships between the pastoral resource and livestock requirements was facilitated using a computer modelling technique (FEDREC - a forerunner of RAPS), which allowed an estimation of the livestock carrying capacities of complex grasslands, estimation of the effects of development, identification of critical feeding periods, and indication of any current over- or understocking. The model reconciled estimates of seasonal patterns of ME supply from pasture and conserved fodder with the seasonal patterns of energy requirements of livestock. In the absence of objective data, estimations of herd composition and monthly changes in liveweight per livestock class were based on field observation and the results of herder interviews.

6.4.3  Characteristics of the pastoral resources of Soi Yaksa

The Soi Yaksa grazing complex (Table 19) was centred about a point 30 km north of Paro and covered an area of about 7 000 ha. Altitude was between 3 400 and 5 000 m; the climate varied from temperate to sub-alpine. The topography was a system of branching, steep-sided valleys, often with narrow or non-existent valley floors. The Soi Yaksa complex was almost exclusively used by yaks and included nearly all of their seasonal grazing lands. Plant communities within the complex were very heterogeneous, reflecting the large variations in altitude, topography and climate. Generally the vegetation could be divided into three types: mixed forest, scrub land and open grassland. Delineation of these communities was often distinct, but there were sometimes large inter-zones.

Forests in the Soi Yaksa complex extended from the lower limits of the survey area up to about 4 200 m, depending on aspect. At lower altitudes and in the western sector, forests on southern aspect (sunny) slopes were dominated by Pinus wallichiana, Picea spp. and Abies spp., with an understorey that included Berberis spp., Piptanthus nepalensis, Salix spp., Pieris spp. and Quercus semicarpifolia. In contrast, the southern-aspect forest of the central sector (e.g. land unit 10) was dominated by Juniperus spp., with an understorey of Berberis spp., Clematis spp., Lonicera spp., Rhododendron spp. and Salix sikkimensis, plus a wide variety of forbs. Also within the central sector, the forests of the northern (shady and moist) aspect slope (land unit 11) were dominated by Abies spp., Betula spp., Salix spp. and a wide variety of Rhododendron spp. Comparison of the latter two forests, which were across the valley from each other, demonstrated the pronounced differences due to aspect: the Pinus spp., Picea spp. and Abies spp. of the shady aspect were replaced by Juniperus spp. on the sunny side.

The shrub land within the grazing complex was predominantly Rhododendron spp. Taller shrub lands were dominated by Rhododendron campanulatum and others, and generally found on the colder, wetter slopes of northern aspect and above 4 200 m (e.g. in land units 6, 18, 25 and 30). These sites were little used by livestock. Short Rhododendron scrub land, dominated by Rhododendron anthopogon and R. setosum, was more common on the slopes of intermediate and eastern aspect (e.g. land units 14, 16 and 21); however, it occurred above the tree line on southern aspects (land unit 24). The highest land units (26, 27 and 28), beginning above 4 400 m, of other than southern aspect, contain short scrub of Rhododendron setosum and R. nivale.

The plant communities typifying the open grassland could be divided roughly into "short" and "lax" types. The "short" grasslands, of mainly southern and western aspects, were above 4 100 m and heavily grazed in summer. This pasture was dominated by Cyperaceae (sedges) and Juncaceae (rushes), commonly with grasses of the genera Agrostis and Festuca, and forbs including Anaphalis spp., Bistorta spp., Cyananthus spp., Fragaria spp., Gentiana spp., Geranium spp., Potentilla spp., Primula spp., Ranunculus spp., Selinum spp. and Bryophyta (mosses). Examples of this pasture were within land units 8, 17, 19, 20 and 23.

The "lax" grassland type was much less heavily grazed in the summer and therefore accumulated biomass during that period. The vegetation was also of a more heterogeneous composition. While generally containing the same species as the "short grassland," other common grasses included Bromus spp., Danthonia spp., Poa spp. and Stipa spp. Common forbs included Anemone spp., Angelica spp., Dipsacus inermis, Iris spp., Morina nepalensis and Thermopsis barbata. Land units 2, 5 and 10 were examples of the "lax" grassland type and ranged between 3 400 and 4 100 m.

From a pastoral resource viewpoint, the Soi Yaksa complex could be divided into three overlapping categories, according to the season of use and botanical characteristics: winter, autumn/spring and summer.

Table 19. General description of land units within the Soi Yaksa grazing complex

Land Unit

Area (ha)(1)

Slope-s(2)

Aspect-s(3)

Altitude (m.a.s.l)(4)

Dominant cover (%)(5)

         

Grass & forbs

Shrub

Forest

Rocks & bluffs

2

142

38

140 - 190

3400 - 4200

93

2

-

5

3

48

20 - 35

265 - 330

3920 - 4280

-

-

-

-

4

107

22 - 32

170 - 320

3920 - 4400

-

-

-

-

5

118

36 - 48

115 - 190

4000 - 4400

82

8

-

10

6

111

25 - 38

000 - 030

4120 - 4380

1

98

-

1

7

98

8 - 14

350 - 004

4100 - 4200

35

65

-

-

8

360

6 - 25

157 - 250

4000 - 4400

95

3

-

2

9

117

15 - 35

073 - 195

4080 - 4450

49

49

-

2

10

252

30 - 48

170 - 200

3800 - 4100

70

5

20

5

11

388

22 - 32

330 - 060

3760 - 4300

3

35

60

2

12

107

18 - 32

340 - 070

4180 - 4640

90

3

-

7

13

419

16 - 42

140 - 220

4000 - 4640

80

3

-

17

14

260

20 - 35

320 - 010

4000 - 4500

60

35

-

5

15

166

35 - 48

175 - 235

4000 - 4500

50

10

-

40

16

285

25 - 30

050 - 110

4200 - 4600

30

60

-

10

17

318

10 - 32

260 - 355

4140 - 4550

50

-

-

50

18

41

15 - 20

350 - 010

4300 - 4600

-

>85

-

-

19

396

15 - 30

120 - 280

4180 - 4800

70

5

5

20

20

385

20 - 30

230 - 330

4200 - 4650

45

5

-

50

21

480

20 - 45

340 - 050

4200 - 4600

30

60

-

10

22

>300

20 - 30

310 - 090

3650 - 4200

[3]

[35]

[60]

[2]

23

267

20 - 35

240 - 320

4320 - 4580

66

4

30

 

24

121

20 - 30

030 - 090

4130 - 4600

25

70

-

5

25

116

20 - 32

330 - 075

4180 - 4500

-

-

-

-

26

435

25 - 38

080 - 260

4410 - 5000

20

20

-

60

27

402

8 - 30

090 - 210

4600 - 5000

40

-

-

60

28

321

15 - 35

300 - 320

4600 - 5000

20

20

-

60

29

139

20 - 40

150 - 240

4080 - 4600

60

-

-

40

30

369

15 - 30

060 - 270

4100 - 4500

10

50

10

30

Notes:  (1) Areas accounting for average slope. (2) Average slope derived from 1:50 000 topographical maps. (3) Aspect range, compass degrees, clockwise (map derived). (4) Metres above sea level (map derived). (5) Visually estimated dominant cover. [ ] indicates an estimate.

The winter grazing areas covered more than 800 ha in the lower altitudes (3 400 to 4 100 m) on southern (sunny) aspect slopes. Vegetation was dominated by a wide range of forbs and underwent a very marked cycle of growth and accumulation of biomass during the summer, and defoliation to ground level during the winter. Annual DM production was estimated to be between 1 500 and 3 500 kg/ha. Although the growing season extended from April/May to October, significant herbage production only began after the onset of the rains. Forage quality was estimated to be moderate at best, and often low. The presence of grass, forbs, and trees and shrubs during October were 38%, 56% and 6%, respectively, with 75% of the vegetation below 20 cm. Most grasses and forbs were recorded below 15 cm, with the forbs showing almost twice the presence below 5 cm as grasses. Shrubs were more evenly distributed throughout the profile to 125 cm.

The flux in biomass and physiognomic structure is illustrated by the comparison of height-frequency profiles representing autumn and spring in Figures 48 and 49. Between October and late May, the aggregate occurrence of grasses decreased from 9% to 2%; forbs from 13% to 2%; and, as expected, trees and shrubs remained the same, at 1-2%. Note that these values refer to the percentage occurrence of a species or group of species within all available compartments of the height-frequency profile and not to occurrence of a species relative to the occurrence of all species (percent composition): the terms "occurrence" and "botanical composition" are used to differentiate the two. During the same period, vegetation ground cover dropped from 65 to 22% and bare ground increased from 8 to 31%. These changes reflected the severity of the excessive stocking load during the winter and early spring, and emphasized the reasons for the high risk of erosion at the onset of the monsoon (June).

The spring-autumn transition grazing areas were typically on southern, eastern and western aspect slopes at medium to low altitudes (3 400 to 4 400 m) and covered more than 800 ha. The botanical composition of this zone was similar to that of the winter grassland. During spring the initial growth and any standing herbage from the previous year was grazed as the yaks moved to the summer grazing. Herbage accumulated during the summer, and was grazed again as they descended to the winter sites.

During October, grasses and forbs made up approximately equal proportions of the botanical composition, at 45 and 46% respectively, while trees and shrubs amounted to 9%. Ground cover was 85% vegetation, 7% litter, 4% bare ground and 4% percent rock. Annual DM production was estimated to be up to 2 500 or 3 500 kg/ha, and the growing season between May and October. As for the winter grassland, spring production depended on the timing of the onset of the monsoon. Herbage quality was low to moderate. During autumn (October) about 75% of the grasses and forbs occurred below 15 cm, and 75% of the trees and shrubs occurred below 30 cm (Figure 50).

Summer grazing was mainly on the southern aspect slopes at the higher altitudes (4 200 to 4 800 m), and on the eastern and western aspect slopes at slightly lower altitudes (4 100 to 4 600 m), with some grazing at high altitudes of the northern aspect slopes. Of the summer grazing lands, the "short grassland" accounted for 2 700 ha and the "short scrub land," 1 400 ha (together about 60% of the grazing).

The respective botanical compositions of these two summer grasslands during October were grasses 44 and 43%; forbs 49 and 38%; and trees and shrubs 7 and 19%. Annual "forage" DM production ranged from less than 500 kg/ha to about 1 750 kg/ha for both grasslands. The pasture of both types, and especially of the "short grassland," was never more than a few centimetres high because it was grazed heavily throughout the whole of the pasture growing season.

Between 25 and 30% of the pasture was composed of Cyperaceae and Juncaceae. Both were grazed by yaks and it is reasonable to assume that they comprised a major component of the diet, despite their low productivity. Cyperaceae and Juncaceae provided stable ground cover under high grazing pressure, and without these two groups of plants the nature of the summer grassland would have been quite different, and probably in a more critical condition. The pasture (i.e. that herbage available and likely to be grazed) of both types, and especially of the "short grassland," was characteristically never more than a few centimetres high (Figure 51) because it was grazed heavily throughout the whole of the pasture growing season. Within the "short scrub land," more than 75% of the shrubs occurred at less than 15 cm, with maximum heights about 35 to 45 cm.

Livestock numbers in the Soi Yaksa grazing complex: were yaks, 897 (88%); cattle, 15 (1%); horses, 71 (7%); mules, 32 (3%); and goats, 9 (1%). Average herd size was 23 head.

The seasonal pattern of yak management was simple, involving regular movement between the winter, spring-autumn and summer grazing lands. Observations and analyses of the pasture supply and requirement indicated that the stocking load of the Soi Yaksa grazing complex was near its potential maximum. Monthly trends in livestock numbers and stocking loads within the Soi Yaksa grazing complex are presented in Table 20, and the altitudinal and aspect distribution of the seasonal grazing lands is illustrated in Figure 52.

Modelling of the pastoral system showed that winter, spring/autumn and summer grazing areas contributed 44%, 3% and 52% of total grazing, respectively. Within the summer grazing areas, the pattern of use varied considerably, with some land units grazed continuously throughout the summer and others rested at mid-summer. Appendix 2 gives estimates of current and potential pasture and fodder production, seasonal patterns of forage surplus and deficit, and livestock carrying capacities for Shu Chu (winter), Thongbu (summer) and Jimdin (summer) valleys.

Table 20.  Monthly trends in livestock numbers and stocking loads within the Soi Yaksa grazing complex

 

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

Land unit (area):  GunhiCh.-Chhui (300 ha) (2)

Number (YE)(1)

150

150

150

7

7

0

0

16

16

0

66

150

21 666.16

Load (YE/ha)

-

-

-

-

-

-

-

-

-

-

-

-

-

Land unit (area):  Lower Thongbu ( ha)(2)

Number (YE)

100

100

100

0

0

0

0

0

0

0

100

100

15 215

Load (YE/ha)

-

-

-

-

-

-

-

-

-

-

-

-

-

Land unit (area):   "LU10 contd." (250 ha)(2)

Number (YE)

307

292

292

220

90

0

0

0

0

105

307

307

58 425.6

Load (YE/ha)

-

-

-

-

-

-

-

-

-

-

-

-

-

Land unit (area):  LU10 (252 ha)

Number (YE)

307

292

292

220

110

0

0

0

0

105

307

307

59 034.2

Load (YE/ha)

1.218

1.159

1.159

0.873

0.437

0

0

0

0

0.417

1.218

1.218

234.2627

Land unit (area):  LU14+15 (426 ha)

Number (YE)

0

0

0

40

40

0

0

0

0

0

0

0

2434.4

Load (YE/ha)

-

-

-

0.094

0.094

-

-

-

-

-

-

-

5.714554

Land unit (area):   "LU2+5 contd." (130 ha)(2)

Number (YE)

0

0

0

47

25

0

0

0

0

5

27

0

3 164.72

Load (YE/ha)

-

-

-

-

-

-

-

-

-

-

-

-

-

Land unit (area):  LU2 (142 ha)

Number (YE)

0

0

0

51

27

0

0

0

0

6

30

0

3 469.02

Load (YE/ha)

-

-

-

0.359

0.190

-

-

-

-

0.042

0.211

-

24.42972

Land unit (area):  LU5 (118 ha)

Number (YE)

0

0

0

43

22

0

0

0

0

5

25

0

2 890.85

Load (YE/ha)

-

-

-

0.364

0.186

-

-

-

-

0.042

0.212

-

24.49873

Land unit (area):  LU12 (107 ha)

Number (YE)

0

0

0

0

60

60

60

60

60

60

0

0

1 0954.8

Load (YE/ha)

-

-

-

-

0.561

0.561

0.561

0.561

0.561

0.561

-

-

102.3813

Land unit (area):  LU13 (419 ha)

Number (YE)

0

0

0

0

0

0

180

180

180

0

0

0

16 432.2

Load (YE/ha)

-

-

-

-

-

-

0.430

0.430

0.430

-

-

-

39.21766

Land unit (area):  LU16 (285 ha)

Number (YE)

0

0

0

0

60

78

78

78

60

60

0

0

12 598.02

Load (YE/ha)

-

-

-

-

0.211

0.274

0.274

0.274

0.211

0.211

-

-

44.20358

Land unit (area):  LU17 (318 ha)

Number (YE)

0

0

0

0

0

20

72

20

0

0

0

0

3 408.16

Load (YE/ha)

-

-

-

-

-

0.063

0.226

0.063

-

-

-

-

10.71748

Land unit (area):  LU18 (41 ha)

Number (YE)

0

0

0

0

0

2

2

2

0

0

0

0

182.58

Load (YE/ha)

-

-

-

-

-

0.049

0.049

0.049

-

-

-

-

4.453171

Land unit (area):  LU19 (396 ha)

Number (YE)

0

0

0

0

220

250

190

190

250

250

0

0

41 080.5

Load (YE/ha)

-

-

-

-

0.556

0.631

0.480

0.480

0.631

0.631

-

-

103.7386

Land unit (area):  LU20 (385 ha)

Number (YE)

0

0

0

0

0

0

13

13

13

0

0

0

1 186.77

Load (YE/ha)

-

-

-

-

-

-

0.034

0.034

0.034

-

-

-

3.082519

Land unit (area):  LU21 (480 ha)

Number (YE)

0

0

0

0

0

0

69

17

17

0

0

0

3 134.29

Load (YE/ha)

-

-

-

-

-

-

0.144

0.035

0.035

-

-

-

6.529771

Land unit (area):  LU23 (267 ha)

Number (YE)

0

0

0

0

0

24

71

103

32

32

0

0

7 972.66

Load (YE/ha)

-

-

-

-

-

0.090

0.266

0.386

0.120

0.120

-

-

29.86015

Land unit (area):  LU24 (121 ha)

Number (YE)

0

0

0

0

0

11

32

47

14

14

0

0

3 590.74

Load (YE/ha)

-

-

-

-

-

0.091

0.264

0.388

0.116

0.116

-

-

29.67554

Land unit (area):  LU25 (116 ha)

Number (YE)

0

0

0

0

0

10

31

44

14

14

0

0

3 438.59

Load (YE/ha)

-

-

-

-

-

0.086

0.267

0.379

0.121

0.121

-

-

29.64302

Land unit (area):  LU26 (435 ha)

Number (YE)

0

0

0

0

32

32

55

55

55

0

0

0

6 968.47

Load (YE/ha)

-

-

-

-

0.074

0.074

0.126

0.126

0.126

-

-

-

16.01947

Land unit (area):  LU27 (402 ha)

Number (YE)

0

0

0

0

0

0

78

78

78

0

0

0

7 120.62

Load (YE/ha)

-

-

-

-

-

-

0.194

0.194

0.194

-

-

-

17.71299

Land unit (area):  LU28 (321 ha)

Number (YE)

0

0

0

0

0

0

62

62

62

0

0

0

5 659.98

Load (YE/ha)

-

-

-

-

-

-

0.193

0.193

0.193

-

-

-

17.63234

Land unit (area):  LU29 (139 ha)

Number (YE)

0

0

0

0

0

0

120

120

0

0

0

0

7 303.2

Load (YE/ha)

-

-

-

-

-

-

0.863

0.863

-

-

-

-

52.54101

Land unit (area):  LU30 (369 ha)

Number (YE)

0

0

0

0

0

60

0

0

60

60

0

0

5 477.4

Load (YE/ha)

-

-

-

-

-

0.163

-

-

0.163

0.163

-

-

14.84390

Land unit (area):  LU4 (107 ha)

Number (YE)

0

0

0

0

20

0

0

60

60

60

0

0

6 086

Load (YE/ha)

0

0

0

0

0.187

0

0

0.561

0.561

0.561

0

0

56.87850

Land unit (area):  Wonney (150 ha)(2)

Number (YE)

0

0

0

0

0

50

50

50

0

0

0

0

4 564.5

Load (YE/ha)

-

-

-

-

-

-

-

-

-

-

-

-

-

Land unit (area):  LU7 (98 ha)

Number (YE)

0

0

6

28

42

60

3

0

50

50

0

0

7 272.77

Load (YE/ha)

-

-

0.061

0.286

0.429

0.612

0.031

-

0.510

0.510

-

-

74.21194

Land unit (area):  LU8 (360 ha)

Number (YE)

0

0

24

102

154

220

13

0

184

184

0

0

26 808.83

Load (YE/ha)

-

-

0.067

0.283

0.428

0.611

0.036

-

0.511

0.511

-

-

74.46897

Total (YE)

864

834

864

758

909

877

1 179

1 195

1 205

1 010

862

864

(sum)         347 541.03

                         

(av.)    44.20

Notes: (1)  YE = yak equivalent days. (2) Areas are merely indications, being estimated post-survey, and not used in calculations.

Figure 48.   Aggregate plant species height/frequency profiles for winter grazing area, autumn (October, 1986)

Figure 49. Aggregate plant species height/frequency profiles for winter grazing area, spring (May, 1987)

Figure 50.  Aggregate plant species height/frequency profiles for spring/autumn grazing area

Figure 51.   Aggregate plant species height/frequency profiles for summer grazing area, predominantly grassland

Figure 52.  Altitudinal and aspect distribution of seasonal grazing lands, Soi Yaksa

6.4.4  Resource constraints and development opportunities

During interviews, herders of the Soi Yaksa grazing complex emphasized that the level of feeding during winter was the most critical factor limiting livestock production and health. Evidence of this included:

i. The average use of the winter grazing areas was five to ten times that of the other seasonal grazing areas, while pasture production at the winter sites was one to four times that of the other areas.
ii. At prevailing stocking rates, pasture growth exceeded pasture demand for, at the most, four months of the year.
iii. For winter survival, the yaks depended on very low quality "standing" fodder (carried over from summer), and the conversion of body fat.
iv. The contribution made by fodder conservation was insignificant.
v. Significant liveweight losses occurred during winter.
vi. Computer modelling indicated under-feeding in winter was in the order of 33%.
vii. Computer modelling also indicated that, at current stocking rates, pasture/fodder deficits were likely to occur during January to April within winter grazing areas, and during March to May within the summer grazing areas.
viii. The dramatic reduction in standing biomass and increases in bare ground recorded in land unit 10 between October and May further indicated high grazing pressure during the winter.

Accordingly, grassland development programmes should be primarily directed toward:

ix. overcoming the winter and spring forage deficit;
x. increasing fodder production and conservation in winter grazing areas;
xi. extending pasture growing season and pasture availability; and
xii. increasing summer pasture production and quality to meet feed requirements of lactation, and to increase fat deposition (liveweight) for assimilation during winter.

Pasture development

One winter grazing area and two summer grazing areas were identified as having a high priority or potential for development. Estimates of current and potential pasture production characteristics of land units of the Soi Yaksa grazing complex are presented in Table 21.

Within the winter grazing area, priority should be given to increased summer production of high quality hay or silage. This would improve levels of livestock feeding during the winter, decrease winter deaths and tend to delay movement to the spring and summer grazing lands, thus relieving pressure on those lands during a critical time of year. Herders spoke of the availability of labour being a major factor limiting the amount of hay produced. This could be partially overcome by using a perennial legume for hay or silage production, rather than the traditional annual crops. The area for hay or silage production could be increased significantly because not all fields would not have to be cultivated and sown each year.

Table 21.  Current and potential pasture production characteristics(1) of land units of the Soi Yaksa grazing complex (subjective)

Land Unit

DM Production(2)

Pasture Quality(3)

Growing Season

 

Current

Potential

   

2

2 500 - 3 500

 

low-moderate

May-Oct

5

2 500 - 3 500

 

low-moderate

May-Oct

7

  900 - 1 800

 

moderate

 

8

  750 - 1 500

2 000 - 3 500

moderate

May-Oct

10

1 500 - 3 500

3 500 - 5 500

low-moderate

Apr/May-Oct

13

1 500 - 2 000

 

low

May-Oct

14

1 000 - 1 500

 

low

Jun-Sep

15

  500 - 1 000

 

low

 

16

  500 - 1 000

 

low

Jun-Sep

17

350 - 750

 

low

May/Jun-Sep

19

1 000

2 000 - 3 500

moderate

May-Oct

20

400 - 750

 

low

May/Jun-Sep

Notes:  (1) Relating to grassland or inter-shrub pasture sections of land unit only. (2) kg DM/ha. (3) Subjective assessment of present pasture quality

Land suitable for development as perennial leguminous hay or silage pasture was limited and unlikely to be sufficient to eliminate the problems associated with winter fodder shortages. In an initial development phase, approximately 10 ha might be used for establishment of perennial hay or silage pasture. With an expected production of 5 500 kg DM/ha (see Appendix 2), the effective forage supply would be increased by 3% and not be sufficient to cover the general winter forage deficit. Therefore any additional fodder should be for strategic use to maximize economic benefits. For example, it could be fed to weak animals (particularly the young), and cows in the later stages of pregnancy.

Both the summer areas assigned development priority were major grazing sites, with gentle to moderate slope and a southern aspect. Within these areas, development would focus on the increased production of higher quality pasture to be grazed in situ. A trial was established in the Thongbu Valley to screen suitable pasture species.

Land suitable for the initial development phase of the summer area covered 40 ha. If the area produced about 2 750 kg DM/ha, then the effective pasture supply would increase by between 5 and 10%. Overall, this initial level of development would result in marginal to moderate improvement in overall livestock feeding. The development should therefore be directed at producing special purpose pasture for feeding lactating cows and the growing of pasture that extended the duration of pasture availability.

Within the context of the whole Soi Yaksa grazing complex, extensive revision of grazing management with, for example, deferred grazing or subdivision and more intensive grazing management would be beyond that practicable during the initial development phases, beyond the understanding of the herders, and too much of a violation of traditional practices to be considered as a viable development option in the short term. Minor management changes were however necessary to facilitate the successful establishment and use of the improved pastures and fodder areas. In areas developed for perennial fodder crops, complete livestock exclusion and careful management to facilitate establishment would be necessary. The economics of fencing would depend on the scale of development. The larger and more aggregated the area developed, the less the cost of fencing on a unit area basis. The realization of the development possibilities would depend on the successful completion of the trial programme initiated under the project.

Livestock carrying capacities

Carrying capacity can be defined as the number of livestock that can be grazed on a particular area so that its long-term productivity is assured and the vegetative cover maintained in good condition.

Table 22.  Estimates of stocking loads for a selection of typical grasslands based on patterns of use of the seasonal grazing, derived from herder interviews and field surveys.

Grassland type

Season of use

Stocking load
(YE days/ha)(1)

Total survey area

35

Open short

summer

74

Open short

summer

103

Open short

summer

30

Open short

summer

3

Open short

summer

6

Open forest/forb

winter

234

Mixed short

spring/autumn

24

Mixed short

spring/autumn

6

Notes: (1) Yak Equivalents × number of days per hectare (365 YE days/ha = 1 YE/ha)

In order objectively to ascertain the carrying capacity of a particular area, the following factors must be known: productivity of the herbage, forage quality, optimum degree and pattern of utilization, seasonal pattern of production of the forage, energy and nutrient requirements of the livestock, and environmental variability. Since local resources were not adequate for a detailed assessment of carrying capacity, the status of current stocking loads were interpreted using analyses based on field estimations, indirect indicators of current stocking loads and the observed condition of the grasslands. Survey results showed that stocking loads varied considerably between and within the grassland types of Soi Yaksa. This reflected both differences in forage productivity and the stocking loads imposed by the herders. Over all of the Soi Yaksa complex, stocking loads averaged 35 YE days/ha and varied between 3 and 234 YE days/ha (Table 22).

Evidence of overgrazing

The most striking visual evidence of overgrazing was generally confined to the upper altitude limits of the grassland, some yak wintering areas within pine forests, and the common grazing around villages. The botanical composition and physiognomic status of an area can indicate its grazing history. The actual changes due to grazing that may have taken place in Bhutan's higher altitude grasslands are hard to quantify because there are few historical records. Additionally some indicators may have been misinterpreted.

Two adjacent, southern aspect, summer grazing lands allowed a reasonable comparison of heavily grazed and lightly grazed grasslands. Within the heavily grazed area, grazing was fairly intense for the whole of the growing season and vegetation close cropped. This area was dominated by Cyperaceae and Juncaceae and received a stocking load of 104 YE days/ha. In the lightly grazed area, the vegetation was dominated by Danthonia sp. and Stipa sp. The stocking load was about 53 YE days/ha, with grazing confined to late summer. In the area of lower stocking loads and shorter grazing duration there were more grass species and greater standing biomass. Evidence did not indicate greater production within the more lightly grazed area, nor that the more lightly grazed area was in better condition. Ground cover appeared to be less on the lightly grazed site.

Grazing can be an important factor in maintaining a grassland. The forage resource status of the bamboo grassland of the Pele La grazing complex is maintained by constant grazing (see Dickie and O'Rourke, 1984). With lighter stocking loads, the bamboo would grow to full height, its foliage become less accessible, and ground cover vegetation would be shaded.

Trends in livestock numbers can be used to indicate the changing status of a grassland from a utilization viewpoint. The few data available and herders' comments indicated that over recent years cattle and yak numbers had increased. Another indicator of excessive livestock numbers is low productivity per animal. If the level of feeding is significantly less than optimal, then factors such as reproductive rate, growth rate and milk production, decrease. Some evidence suggested that this was occurring.

The FEDREC model confirmed the high incidence of forage deficits (see Appendix 2).

Towards better livestock loads

A range of indicators suggested the existence of overgrazing and degradation of some, but not all, of the grazing lands. Adjustment of stocking loads in line with carrying capacity is a desirable objective. However, because of the complexity of the grasslands and the unreliability of some livestock data, specific recommendations for carrying capacities were not appropriate. Having stocking loads commensurate with the forage resources might be achieved by a reduction in livestock numbers, improvement in the forage resource, and manipulation of herd composition. The common remedy suggested for overgrazing is to simply "reduce numbers." This would be difficult in practice, because it depends on an accurate survey of current livestock numbers and an ability to enforce livestock limits and the necessary management practices. The cooperation of the herders would be necessary, and they would have to be thoroughly convinced of the economic advantages of controlled numbers. Demonstrations of the benefits would be essential.

A reduction in livestock numbers may not always lead to improvement in the production and quality of vegetation. If livestock on a particular area are underfed, then a reduction in numbers will enable increased forage intake by the remaining animals, and so the sum utilization of the vegetation will tend to remain about the same. Another side effect of improved livestock nutrition would be increased reproduction rates and increased survival, which would tend to counter the effects of de-stocking. The improvement of forage production within an overgrazed area is the converse of a reduction of livestock numbers in that area, and subject to the same limitations regarding strict livestock numbers and management practices.

Traditional yak herd compositions closely resemble that of a natural herd, which is continually being modified by the effects of starvation, disease and predation. The herds were not tailored to maximize production of the primary product. If the herd composition were modified, then the following changes would occur: the efficiency of milk production per unit of forage consumed would increase; total milk production would increase; and the number of livestock available for sale would increase. This form of change can only be achieved with improved levels of feeding and the sale of excess livestock. The manipulation of herd composition would increase herd productivity and make any reductions in livestock numbers more acceptable to the herders, as overall production would not be decreased.

No single approach would achieve full and stable reduction of livestock numbers within the upper temperate and sub-alpine grasslands. For this reason, ways of achieving optimal stocking loads should be implemented as an integrated package. The underlying sociological force causing increasing livestock numbers (division of families and the desire of each sibling to own livestock) would have to be resolved. Integrating all these components would require considerable organization and forbearance.


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