The environmental challenge

The valleys and lower mountain ranges ofsouth-central Tibet have a semidesert

appearance. Overexploitation of vegeta-tion from ancient times until recently hascaused severe erosion processes and con-verted previous forest and scrub commu-nities into open steppe (Figure 1). Themain consequences for the local humanpopulation have been a marked shortageof firewood and construction wood. Thelast residues of juniper shrubs are beinguprooted in remote areas. Poplar and wil-low plantations in valleys cover some ofthe rural demand for construction wood,but they offer firewood of only minorquality and require either irrigation or ahigh groundwater table.

The scientific challenge

The common consensus in the scientificcommunity is that southern Tibet has nopotential for tree growth. It hardly seemspossible to believe otherwise, in view ofthe dry and barren Central Asian environ-ment. The only exceptions are sites withsurplus water, such as river floodplains,where poplar woodlands and thickets ofwillow and buckthorn are assumed togrow naturally.

Several comprehensive ecologicalinventories were undertaken in southernTibet between 1995 and 1999 in a cooper-ative effort involving the Tibet PlateauInstitute of Biology in Lhasa and the Fac-ulty of Geography at the University ofMarburg, Germany. These investigations

Sacred Forests in TibetUsing Geographical Information Systems for Forest Rehabilitation

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The treeless desertlike environments ofsouthern Tibet are assumed to be naturallyunsuitable for forests. Yet, climatic condi-tions do allow for the growth of indigenoustrees in Lhasa and many parts of southernTibet, even where there is no high groundwa-ter table or irrigation. This was discoveredand proven in a Sino–German research proj-ect launched in 1997. The project made aninventory of forest relics, correlated residualtree stands with climatic data, and success-fully cultivated nonirrigated indigenousjunipers and cypresses. The eroded semi-desert landscape of southern Tibet appearsto have a huge potential for reforestation.The area with a potential for tree growth wasinvestigated using the Geographical Informa-tion System known as GRASS (Geographical

Resource Analysis Support System). Refor-estation measures could meet the heavydemand for timber and firewood, help com-bat erosion on overgrazed slopes, andrestore the degraded pastures. Grazing mustbe excluded on reforestation plots. Simulta-neously, rangelands may regenerate afterovergrazing. The optimum duration of theungrazed period varies with altitude, humidi-ty, soil conditions, and the degree of degra-dation. Successional trends observed onexclosure plots suggest that the drier the cli-mate and the lower the initial degree ofherbaceous vegetation cover, the longer theungrazed period will be beneficial for pastureregeneration. Challenges in research andpractice resulting from these preliminaryresults are highlighted.

FIGURE 1 Hypothetical desertification process on lower sunny slopes of the KyiChu–Yarlung Zhangbo area around Lhasa. The rehabilitation of forests is possible,provided that there is rootable substrate. (Based on sketches by S. Miehe, 2002)

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revealed numerous isolated tree stands ofindigenous juniper species within thedesertlike shrublands. Most of the siteshave a southern orientation, with a shal-low rocky substrate. The trees are of mod-erate to excellent vitality and producelarge quantities of fruit. Young trees occurwhere trampling or grazing during winteris not too great. Two juniper tree speciesare widespread in southern Tibet: Junipe-rus convallium Rehder & Wilson in the low-er reaches of the Kyi Chu and YarlungZhangbo between 3600–3700 m and4100–4570 m, and Juniperus tibeticaKomarov from 4100 up to a maximum of4850 m, the latter reaching far into west-ern Tibet. Most of the trees are under reli-gious protection as junipers are sacred inthe Tibetan tradition. The largest standsof juniper trees are even pilgrimage sites,such as Reting Forest, 80 km north ofLhasa (Figure 2).

Sacred forests are still found some 600km west of the current westernmost forestborder as it is shown in the Atlas of Tibet.Rainfall data in the area suggest that thedrought limit of juniper trees correlateswith annual precipitation of 200–250 mm.The pattern of isolated forests surroundedby vegetation types commonly believed tooccur naturally in other climates resem-bles the isolated tree stands of Polylepiswithin Andean páramo grassland, Erica inafroalpine heathlands, and Ulmus trees inthe steppe of Mongolia.

On the basis of field evidence, wehypothesize that the present high mountaindeserts of southern Tibet are the result ofdeforestation due to centuries of woodcut-ting, use of incense, and grazing. They canbe reforested with indigenous tree specieswithout irrigation if grazing is excluded.Figure 3 shows the potential zonation ofjuniper forests in the Lhasa area, as recon-structed from residual tree stands.

Use of Geographical ResourceAnalysis Support System to identifyareas suitable for reforestation

Intense ecological research on environ-mental conditions affecting indigenousjuniper trees in southern Tibet resultedin a comprehensive data set of point

information on distribution. Geographi-cal Information System (GIS) analysis ofecological features makes it possible todetect patterns and relationships that arenot clearly evident without visualizing

FIGURE 2 J. tibetica in the Reting sacred forest at 4400 m.The forest is overmature, and regeneration is inhibited bywinter grazing. (Photo by G. Miehe)

FIGURE 3 Potential altitudinalforest belts in the Lhasa area insouthern Tibet, extrapolated onthe basis of forest relics. (Basedon sketch by S. Miele, 2002)

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the data. Information on the occurrenceof indigenous juniper trees linked withdata on rainfall variability, partly extrap-olated, was observed and analyzed usingthe Geographical Resource Analysis Sup-port System (GRASS) and a digital ter-rain model (DTM) of 2 selected areas insouthern Tibet. Potential forest siteswere identified on this basis. Extendedareas in the lower Lhasa valley could sup-port tree growth without irrigation (Fig-ure 4). The maps offer a foundation foradditional reforestation measures in thisarea.

Evidence of forest potential

To provide experimental evidence for for-est potential in Tibet, saplings of indige-nous junipers and cypresses were raised inan experimental tree nursery in the TibetPlateau Institute of Biology for 1–2 years.In 1999 and 2000, plantation trials wereundertaken on fenced experimental plotsbetween 3750 and 4170 m above Lhasa(Figure 5). Despite the short cultivationperiod (at least 3 years are recommend-

ed), the survival rate of saplings averaged18% in the 1999 plantation and almost100% in the 2000 campaign. The saplingswere only watered in the tree nursery andat the time of plantation. They arepresently growing without any supplemen-tary irrigation.

Combining reforestation withrangeland regenerationEvidence of tree growth in Lhasa revealsthat vast areas are secondary shrublandsthat do replace forest. Thus, the erodedsemidesert landscape of southern Tibethas a huge potential for reforestation.Grazing by livestock must be excludedfrom afforestation plots until the trees arestrong enough to resist trampling andbrowsing. At the same time, rangelandsmay regenerate from overgrazing. Theoptimum period for the exclusion of live-stock varies with altitude, humidity, soilconditions, and the degree of pasturedegradation. However, there is a lack oflong-term studies and experiments in thisarea.

FIGURE 4 DTM of the lower Lhasa valley with potential reforestation areas extrapolated from mapped residual trees. 30.4% (1,620 km2) of the total area is suitable for reforestation with J. convallium (red) and J. tibetica (green).Intermediate areas are shown in brown. The potential forest area is partly restricted by unsuitable substrates such as solid rock, not included in the DTM. (Model by M. Will)

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The second purpose of the experi-mental exclosure plots was to observeand document changes in vegetation thattake place after grazing has been exclud-ed at different altitudes. On the lowest of7 exclosure plots fenced in 1997, situatedat 3750 m, the extrapolated annual rain-fall was 485 mm. The highest plot islocated at 4650 m and receives some 715mm annual rainfall (rainfall has beenmeasured on all plots since 1997)—morethan in the temperate oak–pine forests ofsoutheastern Tibet. On the lowest plot,heavy regeneration of both herb andshrub layers was recorded. Within 4years, the cover of both strata almostdoubled. The cover percentage of the talldominant grass (Pennisetum flaccidum)rose from 10% to 32%. Where it domi-nates today, it has replaced the less pro-ductive small bunch grasses (Eragrostisand Tripogon spp.), which are probablymore resistant to trampling and overgraz-ing. The latter pioneers have occupiedpatches of ground that were previouslybarren. The number of species increasedslightly, from 21 to 24. Some grazingweeds have been replaced by plants witha greater demand for nutrients, whichare probably provided by accumulatedplant litter.

It is remarkable that Artemisia santolin-ifolia reinvaded the plots very quickly. Thiswormwood species is becoming wide-spread above 3900 m on slopes with asouthern orientation above Lhasa. Theexperiment showed that the growth of thisshrub at higher altitudes is not only afunction of the greater amount of rainfallmeasured there; intensive grazing and col-lecting of fuelwood and incense over cen-turies reduced A. santolinifolia on the low-er slopes. A similar connection can beobserved with the potential for Buddlejaspp. trees on the lower valley flanks, whichform thickets that suppress most of thegrasses during later regeneration stages inthe absence of woodcutting.

These preliminary results from anexperimentation period of just 5 yearsprovide only rough ideas about crucialquestions of combined silvicultural–envi-ronmental–pastoral restoration projects:

• How long are fences necessary to pro-tect young trees?

• What is the future development of veg-etation in this environment? Will grass-es or shrubs dominate after a certainperiod of time?

• When will the aims of foresters (safegrowth of young trees) and of environ-

FIGURE 5 South-facing slopenear Lhasa with grazingexclosure plots (dots) between3800 and 4650 m. Whitesquare indicates the locationof residual J. convallium. (Photo by G. Miehe)

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mental conservationists (dense anddiverse plant cover that stabilizes thesoils and improves the water catch-ment) start to diverge from those ofpastoralists (dense, palatable, and pro-ductive herb layer with a certain resist-ance to trampling)?

The preliminary observations ofregeneration processes made on the dif-ferent exclosure plots imply that the drierthe climate and the lower the initial coverdegree of the herbaceous vegetation, thelonger it will take to observe significantpasture regeneration.

Conclusions and recommendations

Integrating GIS in environmental researchimproves decision making in planning forsustainable development and makes it pos-sible to identify areas where reforestationis promising.

Generally, the environmental reha-bilitation of both woody and pasturecomponents seems very appropriate in

the zone of dry juniper forests of the KyiChu and Yarlung Zhangbo catchments(Figure 6). Many questions remain to beanswered, however. General recommen-dations cannot be given as long as so lit-tle is known about the vegetation ecolo-gy of this area. Thus, environmentalrehabilitation projects will necessarilyhave to include further experiments.The cultivation of junipers and otheruseful woody species adapted to the localclimate can be done by village communi-ties in simple low-input tree nurseries.Fencing is much more problematic.Fences must be livestock-safe but cheapand eventually removable. Mud brickwalls are a safe but labor-intensivechoice. If mud is taken from slopingsites, erosion problems can be aggravat-ed. Thorn fences and turf walls shouldbe avoided by all means to preserve frag-ile natural resources. The monitoring ofrangeland regeneration should be donein collaboration with local herders, whohave the most experience in judging thequality of a pasture.

FIGURE 6 Treeless highmountain desert with extendedsandy areas along the lower Kyi Chu (Lhasa River) and theYarlung Zhangbo. This area has a great potential forreforestation. (Photo by G.Miehe)

FURTHER READING

[APMN] Asia-Pacific Mountain Network.Juniper Forum Web Site. www.mtnforum.org/apmn/juniper_forum.htm.Farjon A, Miehe G, Miehe S. 2002. Thetaxonomy, distribution and ecology ofJuniperus in High Asia. In: Forest andWalnut Research Institute and Kyrgyz-Swiss Forestry Support Program, editors.Problems of Juniper Forests: Looking forSolutions, Methods, Techniques. Proceed-ings of the International Symposium,Bishkek, 7–11 Aug 2001. Bishkek, Kyr-gyzstan: Forest and Walnut ResearchInstitute, pp 70–79.Miehe G, Zhang Y, editors. 2000. Envi-ronmental Changes in High Asia. Proceed-ings of the International Symposium,Marburg, 29 May 1997; Marburger Geo-graphische Schriften 135. Marburg, Ger-many: Geographisches Institut der Uni-versität Marburg.

AUTHORS

Georg Miehe, Sabine Miehe, Katja Koch,and Martin WillFaculty of Geography, University of Mar-burg, Deutschhausstrasse 10, D-35032Marburg, Germany.

Georg Miehe and Sabine Miehe arehigh mountain ecologists interested in thevegetation dynamics of high mountainsunder the impact of humans and climaticchanges.miehe@staff.uni-marburg.de

Katja Koch is a student researcherworking on environmental issues in Tibet,with a special focus on vegetation andgrazing ecology.Katja.Koch@students.uni-marburg.de

Martin Will is a student researcherspecializing in GIS.martin.will.tr@gmx.de

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