Documentation:Open Case Studies/FRST522/2022/The restoration and protection of desert riparian poplar (Populus euphratica) forest along the Tarim river, Xinjiang, China

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Summary of Case Study

The restoration and protection of Populus euphratica are critical as it provides ecological and socioeconomic benefits to all stakeholders using the resources. This case study focuses on the Tarim River and its floodplain. It aims at an interdisciplinary approach to discuss the importance of desert riparian poplar, as well as previous damage and recent restoration efforts on regenerating it along the river basin. Therefore, we describe the natural environment and outline the historical development and cultural and economic background. We also examine the water management and gap creation methods in Populus euphratica restoration and suggest some improvements. In the end, this paper recommends some future strategies for the sustainable development of the Tarim river's floodplain and how to protect the endangered Populus euphratica.

Keywords

China, Xinjiang, Tarim basin, ecosystem services, water management, Populus euphratica, restoration

Introduction

Populus euphratica

In recent decades, restoration of degraded and damaged ecosystems has become a challenge for landscape management, nature conservation, and sustainable land use development worldwide[1]. A particular emphasis is placed on river and floodplain restoration because they offer numerous ecosystem services, such as water purification, preventing desertification, storing carbon, and providing habitat for plants and animals. Restoration of riparian and floodplain ecosystems in desert environments becomes particularly important because riparian ecosystems are one of the world's most important and diverse ecosystems. The desert riparian forests are mainly composed of desert poplar (Pulphus euphratica) located along the rivers that flow through the desert. In arid regions, riparian forests provide essential ecosystem services such as ecological stability and the prevention of natural disasters such as sandstorms, heat waves, and desertification[2]. Riparian vegetation is ecologically distinct from adjacent terrestrial vegetation, which remains significantly effective against frequent water level fluctuations[3]. Moreover, Local climatic factors like rainfall, temperature, and humidity are influenced by riparian forests; vegetation provides shade, cools, and slows water flow, controls flooding, and provides microhabitats for aquatic organisms such as fish and amphibians[3]. In general, conserving biodiversity, preserving regional economic development and ecological security, controlling desertification, and ensuring the viability of oasis agriculture and animal husbandry depends on maintaining this priceless natural resource - desert riparian forests.

This restoration process also becomes difficult as water resources become increasingly limited, and the seedlings and saplings in large riparian forest areas have withered[4]. Also, climate change and increased anthropogenic activity have brought severe external disturbances to ecosystems, including droughts, short-term climate anomalies, resource depletion, species invasions, and fires, which increase the restoration difficulty[5]. However, restoring degraded ecosystems in arid areas could be successful when implementing suitable management plans.

Description

Location and Natural Environment

Tarim river basin

Three of the world's largest Populus euphratica forests are located in China, of which 90% of Populus euphratica forests are distributed in the Tarim river basin[5]. The Tarim river basin in continental-arid Southern Xinjiang, China, has a typical desert riparian forest ecosystem. Xinjiang is located in Central Asia between the Qinghai-Tibetan Plateau, Mongolia, and Kazakhstan. The Tarim basin is filled with Quaternary sediments deposited by rivers and moved by wind.[6] The vast inland basin, mostly covered by the Taklamakan desert, descends from 1,300 meters above sea level in the west to 750 meters in the east and is surrounded by the Kunlun, Tianshan and Pamir mountains[6]. The climate is extremely dry because these mountains cut off all flow of moist air to the Tarim basin. The average temperature in January is -9°C, and the average in July is 25°C, indicating a strongly continental climate. The average annual rainfall is less than 25 mm[7]. Consequently, the floodplain ecosystem depends heavily on the water supply from river floods or underground water stored during floods.

The forest along the Tarim river, which is also known as the Tugai forest, forms a natural green belt on the Northern edge of the Taklamakan Desert. Populus euphratica is the dominant tree species in the floodplain ecosystem. As a "green corridor," the Populus euphratica forests have become increasingly important in preventing the merging of the two adjacent deserts, Taklamakan and Kuruktagh[8]. In addition to their socioeconomic and tourism value, these forests also perform important ecological functions, such as preserving biological diversity, regulating climatic and hydrological conditions in oases, the maintenance of soil fertility and regional ecosystems. However, due to the development of large-scale irrigation projects[9], many tributaries of the watershed have been disconnected from the main river[10], causing the reduction of upstream water volume and leading to catastrophic damage to the Populus euphratica trees that formed the base of the ecosystem[11]. The water table had decreased from 3-5m to 8-12m deep by the 1990s, and 47 percent of the remaining Populus euphratica trees had died[11]. Over 50 years, the forested area had shrunk from 5.4 x 104 ha to 0.5 x 104 ha, thriving on the edge of extinction[12].

Cultural History

Military reclamation Museum of Xinjiang production and Construction Corps

In 840 AD, Uyghur people moved into the Tarim basin, mixing with the indigenous Tocharian people and adopting their religion and culture of oasis agriculture[13]. Tocharian, Uyghur, and Chinese people are settled in the oasis at the foot of the mountain. The Tarim river floodplain has never been densely populated because the river is very dynamic. Only the fisherman and nomads like the Lopliks and Abdal lived in the floodplain and could fully adapt to the dynamic environment of the Tarim river floodplain[13]. After the establishment of the People's Republic of China in 1949, the ethnic composition along the Tarim river changed dramatically. The army created state farms, also called military farms or Xinjiang Production and Construction Corps. Built on the upper and lower reaches of the Tarim river, these farms were strongholds during the Peoples Liberation Army (PLA) occupation of Xinjiang.

On the one hand, they serve as a starting point for the reclamation of the Tarim river floodplain; on the other hand, they provide food supplies to the PLA in Xinjiang[14]. Millions of Chinese military personnel and rusticated youth were sent to this region which hugely increased the Chinese population along the Tarim river bank. In 1940, around 75 percent of Xinjiang's total population was Uyghur, and today that figure has dropped to about 45 percent. With the state's population and colonizing policies implemented from the 1950s, the Han Chinese population has increased dramatically from about 7 percent of the total population in the 1950s to about 40 percent today[1].

Socio-Economic Environment

Xinjiang's population changes are accompanied by massive changes in the economy of the oasis, manifesting as a gradual shift from traditional agriculture and agroforestry to intensive irrigated agriculture dominated by cotton[15]. Traditional land use systems are based on various cultivated plants, especially those that sustainably use water resources. However, with the cotton monoculture, water scarcity becomes significantly severe, negatively impacting the Populus euphratica population. Excessive use of surface water for irrigation, particularly in the upstream and midstream cotton fields, has lowered water levels downstream from 3-5 meters in the 1950s to 11-13 meters in the 1990s[16]. As a result, large areas of poplar forests are severely degraded or completely extinct. In addition, part of the middle and upper reaches of the Tarim River dried up in the spring and early summer of 2007 and 2008 due to reduced snowmelt runoff.

Degradation of the Populus euphratica also hugely impacts the pasture system, as it is typically transhumance with goats and sheep as livestock, which use the leaves of Populus euphratica as fodder. Furthermore, riparian forests shelter people and livestock from heat and dust storms. Due to their transpiration, dense riparian forests have a much cooler local climate than scrub vegetation or open deserts, providing a place for recreation. Thus, Populus euphratica floodplain forests have a high potential for restoration even after significant degradation.

Institutional/Administrative arrangements

The management authorities regarding water allocation and ecosystem restoration are the Xinjiang Forestry Administration, the Tarim River Basin Water Resource Commission, and the Xinjiang Production and Construction Corps (military farms).

Xinjiang Forestry Administration

structure of the water resource administration of the Tarim Basin

All Tarim basin nature reserves fall under the purview of the Xinjiang Forestry Administration, which manages and safeguards the region's forests. The Nature Conservation Bureaus under the Forestry Administrations of Bayingouleng and Aksu Prefecture, respectively, are responsible for the day-to-day management of the Tarim Huyanglin and Tarim Shangyou Xayar Nature Reserves. However, the Nature Conservation Bureaus do not have the power to enact conservation measures; in fact, the enforcement of conservation measures is the responsibility of the county-level forestry bureaus[6].

Tarim River Basin Water Resource Commission

The Water Resources Committee of the Tarim river basin was established in 1997 to coordinate the distribution of water resources throughout the Tarim river basin and to avoid conflicts between different levels of administration within the same area. The management bureau under the Tarim River Basin Water Resources Committee is responsible for water allocation and implementing the Tarim River Regulations[17]. However, the policies that the administration bureau developed are carried out by the local water administrations. Water quotas were introduced as one of the management methods. Water usage quotas were established for the upstream and downstream river stretches. Additionally, quotas were established along each river stretch for the amount of water to be retained for natural ecosystems (environmental flow), as well as for agriculture and industry to withdraw[17].

Xinjiang Production and Construction Corps (Military Farms)

The Xinjiang Production and Construction Corps, which operates eight large farms along the Tarim river, is still under the direct rule of the army rather than the Xinjiang government. Thus, the Xinjiang Production and Construction Corps does not participate in the decision-making processes and cannot be controlled by the administration bureau or the Xinjiang government, despite consuming a significant portion of the Tarim River's water[1][17].

Affected Stakeholders

Indigenous farmers and herders will be the most prominent affected stakeholders. Most of the Uyghur indigenous farmers are smallholders who live in traditional villages along the Tarim river. Most herders are also Uyghur people from the villages along the Tarim river. They are extremely vulnerable when facing natural disasters and have no decision-making power. For example, due to water scarcity and soil salinization, farmers and herders were already forced to give up agricultural land during land reclamation. Furthermore, Indigenous farmers and animal herders had no channel to participate in decision-making[18]. Thus, it can be concluded that Indigenous farmers and herders are affected stakeholders with high importance, low relative power, and low influence.

Interested Stakeholders

Cotton Field of the Eighth Division of Xinjiang Production and Construction Corps

The Xinjiang Production and Construction Corps is one of the interested stakeholders. The main objective of Xinjiang Production and Construction Corps is to generate considerable revenue, and one major business they are involving is cotton farming. Since the Xinjiang Production and Construction Corps have access to the entire infrastructure for cotton processing and marketing, growing cotton is the easiest way to increase the revenue. They also have the power in decision-making. It can ignore the regulations implemented by the administration bureau under the Tarim River Basin Water Resources Committee and still maximize its profit by using excessive amounts of water. In addition, it remains a huge political influence that could impact the decision-making process since it is not under the administration of Xinjiang but is administered directly by Beijing[17]. Therefore, The Xinjiang Production and Construction Corps has high relative power and strong influence.

Oil exploitation company is also one of the interested stakeholders. The main objectives for them will be increasing oil yield and profit. Thus restoration and protection will not be the priority. Unfortunately, the oil extraction detaches parts of the riparian forests and arid vegetation. It has high relative power and strong influence since most of the oil company belongs to the state, and they have a huge influence and decision-making power regarding natural resource extraction.

Scientists will be another group of interested stakeholders. Their main objective will be to conduct ecosystem studies along the Tarim river and provide suggestions. For example, the Tarim River Regulations benefited greatly from the scientific input provided by the Xinjiang Institute of Ecology and Geography, which also monitors groundwater levels and the regrowth of vegetation along the Tarim river's lower reaches[19]. In addition, applied research projects on the reforestation of Populus euphratica were conducted by the Xinjiang Forestry Academy, the Poplar Research Institute, and Tarim University. Thus, it is clear that these institutions have a strong influence on Tarim basin development and desert riparian poplar restoration but low relative power.

Discussion

Some water management plans could be considered to successfully conserve and restore riparian poplar forests. One of the management methods will be to maintain a sufficiently high groundwater table by implementing environmental flows[2]. Typically, environmental flows are created to restore parts of the uncontrolled (natural) flow regime[9] and have been used as an ecological restoration measure, particularly by rehydrating alluvial aquifers to support existing degraded vegetation and promote the emergence and establishment of target species[2]. When it comes to desert riparian poplar restoration, a sufficiently high groundwater table must be maintained so that the plants can connect to the groundwater and reach their water supply. One of the successful examples is the Ecological Water Development Project conducted by the Chinese government in 2000[20]. 1038 mcm of water was released in the first three years from the upstream reservoirs, and the water table reacted positively[21]. Even though the recovery of Populus euphratica is slow and under expectation[22], survival and recruitment of new cohorts have both been achieved[23].

Another method to recover riparian poplar forests is the natural disturbance in terms of gap formation. Due to the environmental heterogeneity it produces, gap disturbance is the primary factor influencing forest dynamics[4]. Thus, forest gaps provide crucial habitat for the regrowth of plant species that the under canopy might otherwise suppress. Additionally, they are essential for forest regeneration and succession, particularly for establishing and growing plant species with various ecological recruitment[24]. Dead trees can create canopy gaps in the forest. In general, gap-based regeneration provides a flexible system that can simulate natural regeneration in different environments. Gaps change the light intensity, contributing to the diversity and abundance of seedlings and saplings[25]. Therefore, It can be considered that gap formation is the best method for ensuring the sustainable management and restoration of desert riparian forests[26].

Critical Issues and their Assessments

One of the critical issues is the problem of uneven water distribution and allocation between different administrative areas. For water distribution, the downstream water intakes are below their respective quotas, and some of the original water flow that flow through a certain county has now been cut to transfer to the Tarim River, which causes a significant problem to local water usage. Regarding water allocation, about 66,700 hectares of agricultural land in Aksu County was not included in the water allocation plan. The first division of Xinjiang Production and Construction Corps had a water quota separate from Aksu County. In addition, although the Aksu region has an obligation to protect the existing ecosystem, the Aksu river project does not have an environmental flow quota, and the development of the Aral city may absorb the water volume of the Aksu region. Before 2009, Aral city was part of division one of the Xinjiang Production and Construction Corps. This issue is not adequately managed, as Xinjiang Water Resource Bureau and the management bureau under the Tarim River Basin Water Resources Committee control the decision-making power. They refused any changes to the current water management plan. The Xinjiang Water Resource Bureau remains positive about water distribution and allocation, saying the water transfer is designed following the government's water distribution plan, aims to improve water transfer efficiency, and is based on scientific research results[18].

Another critical issue is the natural ecosystems, especially Populus euphratica degradation due to dykes construction. Several reports from the middle and lower reaches of the Tarim river show that the natural ecosystem inside the dam is improving, while the natural ecosystem outside the dam has further deteriorated since the dam was built[18]. The primary objective of constructing a dyke on the Tarim River's main channel is to control overflow during flooding, which strategically boosts income and lowers expenses. However, the middle reaches of the Tarim River's Tugai forests are threatened by the dykes, since they reduce river system dynamics and negatively impact the forest's ability to regenerate and survive[26]. Once more, the Xinjiang Water Resource Bureau was the only organization to assert that the Tarim river catchment's natural ecosystems were recovering as a whole and did not make any corrections regarding the situation.

Due to its inability to regulate water withdrawal by water users along the Aksu River during spring and early summer, including the Xinjiang Production and Construction Corps and water users within Aksu Prefecture, the Tarim river basin Water Resource Commission's administration bureau is currently unable to ensure water flows all year long along the entire Tarim River. As long as Xinjiang is considered a cotton-producing region, local decision-makers will support cotton production. The Aksu river and the area upstream of the Tarim will most likely experience increased irrigation, which will cause water shortages along the middle and lower reaches and threaten the regeneration of desert riparian poplar.

Moreover, there is a lack of Indigenous community representatives in negotiating. As mentioned, Uyghur farmers and herders have no place on the negotiating table and could be ignored throughout the decision-making process. More research and attention are needed to ensure Indigenous people's rights are secured, and needs are heard. However, with the Chinese government's implementation of genocide and mass detention camps in Xinjiang against Indigenous Muslims, securing locals' fundamental rights becomes harder.

Recommendations

It is necessary to stop further land reclamation. Newly reclaimed land along the upper reaches and the Aksu river will reduce river runoff along the middle and lower reaches, while newly reclaimed land along the middle reaches will inexorably rely on groundwater exploitation. Groundwater extraction will lower the water table, which will cause massive vegetation degradation, negating all restoration efforts. Groundwater abstraction from existing agriculture should be controlled and monitored to avoid lowering groundwater levels and further degradation of ecosystems.

Also, the water allocation quotas must be established on a seasonal or monthly basis to achieve year-round runoff, and the administration bureau under the Tarim River Basin Water Resource Commission's position must be strengthened. Besides, a mechanism must be established to ensure that the Xinjiang Production and Construction Corps adheres to the water quotas established in Xinjiang. Furthermore, there is a need for additional research to offer recommendations for enhancing the water dike and optimizing the operation of the ecological brakes, as well as to establish demonstration zones at local levels to gather experience with allocating and utilizing flood water before expanding it to the entire basin.

Moreover, efforts should be made to strengthen the legal environment. Laws and regulations must be strictly enforced to carry out the water distribution in the Tarim basin.The legal protection of participation rights is necessary to ensure fairness in the distribution of public goods. Also, The establishment of a water market should be considered. A water market must ensure that poor people continue to have access to water. Water is essential for all human activities, so water distribution should not favor the most privileged water users.


This conservation resource was created by Course:FRST522.


References

  1. ↑ 1.0 1.1 1.2 Zerbe, S., & Thevs, N. Restoring central Asian floodplain ecosystems as natural capital and cultural heritage in a continental desert environment. Landscape ecology in Asian cultures (pp. 277-297). Springer Japan. https://doi.org/10.1007/978-4-431-87799-8_19
  2. ↑ 2.0 2.1 2.2 Halik, Ü., Aishan, T., Betz, F., Kurban, A., & Rouzi, A. (2019). Effectiveness and challenges of ecological engineering for desert riparian forest restoration along China’s largest inland river. Ecological Engineering, 127, 11-22. https://doi.org/10.1016/j.ecoleng.2018.11.004
  3. ↑ 3.0 3.1 Mohan, M., Saritha, V. N. K., Rameshan, M., Chacko, A., & Gopikrishna, V. G. (2021). Restoring degraded riparian forest ecosystems of the Western Ghats for ecological sustainability. Restoration Ecology, 29(4), n/a. https://doi.org/10.1111/rec.13254
  4. ↑ 4.0 4.1 Keram, A., Halik, Ü., Aishan, T., Keyimu, M., Jiapaer, K., & Li, G. (2021). Tree mortality and regeneration of euphrates poplar riparian forests along the Tarim river, Northwest China. Forest Ecosystems, 8(1), 1-13. https://doi.org/10.1186/s40663-021-00323-x
  5. ↑ 5.0 5.1 Fu, A., Li, W., Chen, Y., Wang, Y., Hao, H., Li, Y., Sun, F., Zhou, H., Zhu, C., & Hao, X. (2021). The effects of ecological rehabilitation projects on the resilience of an extremely drought-prone desert riparian forest ecosystem in the Tarim river basin, Xinjiang, China. Scientific Reports, 11(1), 18485-18485. https://doi.org/10.1038/s41598-021-96742-5
  6. ↑ 6.0 6.1 6.2 Thevs, N. (2007). Ecology, spatial distribution, and utilization of the Tugai vegetation at the middle reaches of the Tarim, River Xinjiang, China. Cuvillier Verlag. https://cuvillier.de/uploads/preview/public_file/3449/9783867274319.pdf.
  7. ↑ Yaning, C., Takeuchi, K., Changchun, X., Yapeng, C., & Zongxue, X. (2006). Regional climate change and its effects on river runoff in the tarim basin, china. Hydrological Processes, 20(10), 2207-2216. https://doi.org/10.1002/hyp.6200
  8. ↑ Betz, F., Halik, U., Kuba, M., Tayierjiang, A., & Cyffka, B. (2015). Controls on aeolian sediment dynamics by natural riparian vegetation in the eastern tarim basin, NW china. Aeolian Research, 18, 23-34. https://doi.org/10.1016/j.aeolia.2015.04.005
  9. ↑ 9.0 9.1 Glenn, E. P., Nagler, P. L., Shafroth, P. B., & Jarchow, C. J. (2017). Effectiveness of environmental flows for riparian restoration in arid regions: A tale of four rivers. Ecological Engineering, 106, 695-703. https://doi.org/10.1016/j.ecoleng.2017.01.009
  10. ↑ Chen, Y., Li, W., Liu, J., & Yang, Y. (2013). Effects of water conveyance embankments on riparian forest communities at the middle reaches of the tarim river, northwest china. Ecohydrology, 6(6), 937-948. https://doi.org/10.1002/eco.1418
  11. ↑ 11.0 11.1 Chen, Y., Cui, W., Li, W., Chen, Y., & Zhang, H. (2003). Utilization of water resources and ecological protection in the tarim river. Acta Geographica Sinica, 58(2), 215-222.
  12. ↑ Ling, H., Zhang, P., Xu, H., & Zhao, X. (2015). How to regenerate and protect desert riparian populus euphratica forest in arid areas. Scientific Reports, 5(1), 15418-15418. https://doi.org/10.1038/srep15418
  13. ↑ 13.0 13.1 Soucek, S., CRKN MiL Collection, & Cambridge Core EBA eBooks Complete Collection. (2000). A history of inner Asia. Cambridge University Press. https://doi.org/10.1017/CBO9780511991523
  14. ↑ Bellér-Hann, I., & Hann, C. M. (2020). The great dispossession: Uyghurs between civilizations. Lit.
  15. ↑ LI, Y., CHEN, Y., ZHANG, Y., & XIA, Y. (2009). Rehabilitating china's largest inland river. Conservation Biology, 23(3), 531-536. https://doi.org/10.1111/j.1523-1739.2009.01238.x
  16. ↑ Chen, Y. -., Zilliacus, H., Li, W. -., Zhang, H. -., & Chen, Y. -. (2006). Ground-water level affects plant species diversity along the lower reaches of the tarim river, western china. Journal of Arid Environments, 66(2), 231-246. https://doi.org/10.1016/j.jaridenv.2005.11.009
  17. ↑ 17.0 17.1 17.2 17.3 Thevs, N. (2011). Water scarcity and allocation in the tarim basin: Decision structures and adaptations on the local level. Journal of Current Chinese Affairs, 40(3), 113-137. https://doi.org/10.1177/186810261104000305
  18. ↑ 18.0 18.1 18.2 Peng, H., Thevs, N., & Ott, K. (2014). Water distribution in the perspectives of stakeholders and water users in the tarim river catchment, xinjiang, china. Journal of Water Resource and Protection, 6(6), 543-543. https://doi.org/10.4236/jwarp.2014.66053
  19. ↑ Zhang, Y. M., Chen, Y. N., & Pan, B. R. (2005). Distribution and floristics of desert plant communities in the lower reaches of tarim river, southern xinjiang, people's republic of china. Journal of Arid Environments, 63(4), 772-784. https://doi.org/10.1016/j.jaridenv.2005.03.023
  20. ↑ Bao, A., Huang, Y., Ma, Y., Guo, H., & Wang, Y. (2017). Assessing the effect of EWDP on vegetation restoration by remote sensing in the lower reaches of tarim river. Ecological Indicators, 74, 261-275. https://doi.org/10.1016/j.ecolind.2016.11.007
  21. ↑ Liu, Y., & Chen, Y. (2007). Saving the "green corridor": Recharging groundwater to restore riparian forest along the lower tarim river, china. Ecological Restoration, 25(2), 112-117. https://doi.org/10.3368/er.25.2.112
  22. ↑ Hou, P., Beeton, R. J. S., Carter, R. W., Dong, X. G., & Li, X. (2007). Response to environmental flows in the lower tarim river, xinjiang, china: Ground water. Journal of Environmental Management, 83(4), 371-382. https://doi.org/10.1016/j.jenvman.2005.12.026
  23. ↑ Aishan, T., Halik, Ü., Kurban, A., Cyffka, B., Kuba, M., Betz, F., & Keyimu, M. (2015). Eco-morphological response of floodplain forests (populus euphratica oliv.) to water diversion in the lower tarim river, northwest china. Environmental Earth Sciences, 73(2), 533-545. https://doi.org/10.1007/s12665-013-3033-4
  24. ↑ Zhu, J., Lu, D., & Zhang, W. (2014). Effects of gaps on regeneration of woody plants：a meta-analysis. Journal of Forestry Research, 25(3), 501-510. https://doi.org/10.1007/s11676-014-0489-3
  25. ↑ Van Der Meer, Peter J., & Dignan, P. (2007). Regeneration after 8 years in artificial canopy gaps in mountain ash ( eucalyptus regnans F. muell.) forest in south-eastern australia. Forest Ecology and Management, 244(1), 102-111. https://doi.org/10.1016/j.foreco.2007.03.055
  26. ↑ 26.0 26.1 Keram, A., Halik, Ü., Keyimu, M., Aishan, T., Mamat, Z., & Rouzi, A. (2019). Gap dynamics of natural populus euphratica floodplain forests affected by hydrological alteration along the tarim river: Implications for restoration of the riparian forests. Forest Ecology and Management, 438, 103-113. https://doi.org/10.1016/j.foreco.2019.02.009
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