Based on periodⅠquantitative analysis, broomcorn millet and barley emerged as the two most significant cereals among the plant remains discovered at Taitai'er Caves. Broomcorn millet exhibited the highest ubiquity, while foxtail millet and wheat were relatively scarce. Although barleywas exclusively found in K7, its quantity (1,001 grains) vastly exceeded that of foxtail millet and wheat. All plant remains were recovered from K7 and K12, identified as monastic cells (vihāra) where monks resided and performed daily activities. Therefore, these remains directly reflect monastic dietary practices. This evidence indicates a dietary preference among Taitai'er monks for broomcorn millet and barley, supplemented minimally by foxtail millet and wheat. In the periodⅡ, A large number of broomcorn millet husks were still found, indicating that broomcorn millet remained a very important crop even after the caves were abandoned.

The predominance of broomcorn millet and barley in Theravada Buddhist monastic contexts signifies an active adaptation to local environmental constraints. There is a typical temperate continental arid climate, with an average temperature of 7.6°C, frost-free period of 133 to 163 days, annual sunshine duration of 2,789.7 hours and annual precipitation of 171.13 mm. Within this environmental framework, cold and drought tolerance became critical determinants for crop planting selection. According to the climatic conditions of Luntai in the Tang dynasty, the crop growth period in this area was from the end of April to the middle of October. Barley and broomcorn millet, with superior stress tolerance, lower thermal requirements and minimal water demands, thrived under these conditions(Table 3). Their flowering and fruiting stages coincided with the rainy season, eliminating the need for intensive irrigation. Additionally, their shorter growth cycles provided an advantage over wheat, which cultivated from March to June, yielded poorly due to temperature limitations.

In archaeobotanical studies of the southern piedmont of the Tianshan Mountains (Table 4), sites such as Yanghai, Aisikexiaer South^,, and Yuergou exhibit a crop planting structure dominated by broomcorn millet and barley. Liushugou, Mohuzhahangoukou and Wubao^, primarily cultivated barley, while Duogang and Subeixi focused on broomcorn millet. This indicates that drought-tolerant crops (broomcorn millet and barley) formed the core agricultural system in this region since the Bronze Age, adapting to the arid continental climate. A few sites near water sources—such as Xintala, adjacent to Bosten Lake—were able to cultivate wheat.

The Sui to Tang dynasties were in the third warm period in China, the climate was relatively humid and the water and heat conditions were improved. Consequently, foxtail millet and wheat became the preferred cereals in the southern Tianshan region. The Tuyugou site in the Turpan Basin relied primarily on broomcorn millet during the Northern Wei Dynasty. By the Wei-Jin to Tang periods, the Astana site shows evidence of foxtail millet and wheat co-dominance, facilitated by improved hydrothermal conditions. At the Karakhoja Cemetery (Tang Dynasty), the crop planting structure shifted decisively toward foxtail millet and wheat. In contrast, the Kuola site, located at the northeastern piedmont of the Tianshan Mountains, was constrained by higher altitude and poorer hydrothermal conditions. The only plant remains unearthed were broomcorn millet and barley. This divergence underscores how topography-driven hydrothermal variations critically shaped cereal selection across the Tianshan region(Table 4).

Both Taitai'er Caves (the Sui to Tang dynasties) and Tuyoq Grottoes(Northern Wei Dynasty) showed a distinct preference for broomcorn millet. However, the monks of Tuyoq Grottoes demonstrated a significant inclination toward wheat, likely influenced by natural geographical factors. Despite similar latitudes, Tuyoq Grottoes are situated in the Turpan Basin at an elevation of 80 meters above sea level—approximately 1,200 meters lower than Taitai'er Caves—resulting in vastly superior thermal conditions. Additionally, Karez (坎儿井, underground canals) in Turpan Basin provided stable agricultural water supply, creating more favorable hydrothermal conditions for wheat cultivation.

Archaeobotanical data from the Tang dynasty at the Kaiyuan Temple in Zhengding, Hebei Province, reveal a crop planting structure dominated by foxtail millet and broomcorn millet, with overwhelmingly predominant (173 grains of foxtail millet, 39 grains of broomcorn millet, 5 grains of wheat and 2 grains of barley). This contrasts sharply with the crop structure of Taitai'er Caves. under the background of relatively similar environmental conditions in the overall era, such divergence primarily may be related to the local microclimate differences and agricultural planting traditions caused by the natural geographical differences between the two places.

Zhengding Kaiyuan temple is located in the eastern plains in China. Research has shown that the average temperature of the winter from 601 to 820 was approximately 0.52°C higher than that of the present (1961–2000), and during the same period there is a rainy phase of nearly 200 years. It can be seen that hydrothermal condition is one of the most important prerequisites for the cultivation of foxtail millet and broomcorn millet in Kaiyuan temple. In contrast, Taitaier Caves is located in the intermontane basin. The terrain factors make its thermal conditions relatively poor and the climate of Xinjiang during the Sui and Tang dynasties is also quite different from that of Kaiyuan temple. From Southern and Northern dynasties to Sui dynasty (420–600 A.D.), the lower temperature in Xinjiang led to the decrease of glacial snowmelt water and the less precipitation limited the water supply. in the late Tang dynasty, the climate turned cold and dry. in addition, from the Southern and Northern dynasties to the end of the Tang dynasty (420–907 A.D.), there were significant cold or warm climate fluctuation. During the Sui and Tang dynasties, the climate in Xinjiang changed greatly, so it was more suitable for the survival of plants with strong stress tolerance, mainly millet and barley.

The agricultural tradition of the region can not be ignored. in the central plains, foxtail millet and broomcorn millet have been cultivated since the Neolithic age. By the pre-qin period, although a multi-crops planting system of "Five Grains" (foxtail millet, broomcorn millet, rice, wheat and soybean) was formed, foxtail millet and broomcorn millet remained overwhelmingly dominant^,. During the Qin and Han dynasties, this millet-centric structure persisted. During the Wei, Jin, southern and northern dynasties, traditional millet agriculture had matured significantly.Although rice and wheat gained prominence in the Sui and Tang period, millet-centric agriculture continued to dominate^,. Thus, the deep-rooted millet farming tradition in the Central Plains, where Kaiyuan Temple is located, exerted a strong inertial influence on the local crop plantingl selection.

Northwestern China, including Xinjiang, served as a critical hub for the eastward transmission of wheat and barley from West Asia. As early as the late Neolithic age(cal. 5000 BP), wheat and barley cultivation had begun in this region. At the Xintala site, wheat predated barley, reflecting the complexity of crop composition. The Gumugou cemetery relied on glacial snowmelt water to support early wheat cultivation. Starch grain analysis from Shirenzigou site in Balikun county confirmed that the nomadic groups adopted barley as the staple food in spring, which was adapted to the cool and humid climate at the eastern Tianshan foothills and had a short growing period. From the Iron Age to Han and Jin dynasties, agricultural diversification had advanced, with sophisticated processing techniques for wheat and barley. During the Tang Dynasty, the ancient Dahe City in Balikun county developed a crop planting structure dominated by barley and wheat, supplemented by pea and foxtail millet, while military farmers implemented farming strategies tailored to the cold climatic condition. Consequently, the long history of barley and wheat cultivation in Xinjiang reflects environmental adaptation. At Taitai'er Caves, barley thrived due to its stress tolerance (drought and cold resistance). Therefore, the large number of unearthed barley is the result of inheriting the local agricultural tradition and adapting to the environment.

Beyond environmental factors, the preference for barley and broomcorn millet in Taitai'er Caves may also be influenced by Theravada Buddhism. Theravada Buddhism emphasizes alms-begging (Pindapāta) and non-selectivity in food consumption(托钵乞食、不择饮食). The Theravada Buddhism advocates begging, this doctrine asked monks to accept any donated food without preference. Therefore, the eating habit of monks in Taitai'er Caves are closely related to the grain production and supply in Kuča. According to the wooden slips SI P/136_B from the Russian collection༈俄藏木牍SI P/136_B༉, the largest quantity of barley purchased was 553 dou༈斗༉^,, indicating that the Kuča monastery had a great demand for barley. Barley straw is also an ideal building material, which is conducive to the construction of caves and other buildings. Inddition to edible functions, Documents Excavated at Turpan (III)(吐鲁番文书) mentioned that barley was ritually offered in worship of Heaven.

Taitai'r Caves are located in Kuča and served as a center of Theravada Buddhist in the Western Regions during the Tang dynasty. From emperors to commoners, donating and abolishing secular affairs, observing fasting, receiving scriptures and listening to Dharma, and forgetting tiredness.The agricultural practices revealed by plant remains unearthed in the Taitai'r Caves reflect a proactive adaptation strategy of Buddhist monasteries to support large numbers of non-productive populations amid arid environments. Moreover, the monastic diet dominated by broomcorn millet and barley epitomized a precise alignment with the oasis agro-economy.

Five kinds of fruit were found there: apricot (Armeniaca vulgaris), peach (Amygdalus persica), grape (Vitis vinifera), walnut(Juglans regia) and gourd(Lagenaria siceraria). Quantitatively, apricot dominated with 523 grains, followed by peach (4 grains), walnut (9 grains), grape (3 grains), and bottle gourd (1 grain). Apricots not only constituted the absolute majority of fruit remains but also exhibited the highest ubiquity (50%). Peach and walnut followed with a recovery rate of 33.33%. The Great Tang Records on the Western Regions (大唐西域记) in the record:" The kingdom of Kuča (屈支国) spans over 1,000 li (里) east-west and 600 li (里) north-south.……It is suitable for broomcorn millet and wheat, yields rice, and produces grapes, pomegranates, abundant pears, crabapples, peaches, and apricots". This indicates that during the Sui-Tang times, inhabitants of Kuča (modern Kuqa) recognized the nutritional value of fruit.

The total number of apricots unearthed in the caves occupies an absolute advantage, which should be closely related to its growth habit, fruit tree management, planting tradition and nutritional value. Apricot originated in Xinjiang and exhibits exceptional environmental adaptability, with extreme cold and drought resistance. Apricot trees require minimal management, 2–3 years of fruit, 4–5 years of high yield. Archaeological evidence confirms that apricots have a long history of cultivation in Xinjiang. Apricot remains have been unearthed at the Niya site, Astana Cemeteries and Tuyoq Grottoes in Xinjiang. Up to now, Kuqa White Apricot is a high-quality variety of apricot cultivation in China. According to chronological analysis, we found that during the Sui and Tang dynasties, apricots were always used by Buddhist monks. Apricot flesh is rich in β-carotene. It is widely cultivated here with high yield, in the midsummer fruit off-season, it was the preferred choice of monks to eat.

Charcoal analysis from K7 revealed that the monastic communities selectively used small branches of Populus sp, Willows and Fraxinus for fuel and no fruit tree detected. This suggests monastic communities avoided burning fruit trees, likely because orchard cultivation was integral to their economic system. Monks strategically preserved fruit trees for sustained food production rather than fuel consumption .

Theravada Buddhism strictly prohibits monks from engaging in farming activities. While monks were permitted to receive land owneship rights, they could not personally participate in cultivation. Instead, field labor was delegated to hiring laborers affiliated with the monastery. Monks obtained portions of grain cereals or collected land taxes. As stated in the Abhidharma-samuccaya-vyākhyā (阿毗达磨集异门足论): "Digging the earth with one's own hands" and "destroying living plants" were considered "offenses requiring censure". Similarly, the Mahāparinirvāṇa Sūtra (大般涅槃经) prohibited "eight impure practices", including:"Hoarding gold or silver, owning slaves/livestock, maintaining granaries, engaging in trade, farming and preparing food with one's own hands".

Beyond doctrinal constraints, the fact that Kuča monks did not engage in agriculture may also be related to their social status. According to The Great Tang Records on the Western Regions (大唐西域记), on the 15th day of each month and the lunar month-end, the king and ministers discussed state affairs, consulting eminent monks before announcing decisions. This highlights the high political standing of monastic elites in Kuča, potentially explaining their exemption from manual labor. Despite Theravada prohibitions on farming, abundant broomcorn millet husks discovered in K7 and K12 at Taitai'er Caves indicate monks likely engaged in dehusking within the monastery. Beyond food consumping, millet husks may have been repurposed—for example, stuffed into sacks placed at bed legs to prevent floor damage.

Strontium isotope analysis of plant remains from Taitai'er Caves confirms local cultivation of both cereals and fruits. The ratios of ⁸⁷Sr/⁸⁶Sr in river samples from Kuča are between 0.7102 and 0.7118, while the ratios of ⁸⁷Sr/⁸⁶Sr in walnuts and peach are 0.710773 and 0.711246, respectively, the ⁸⁷Sr/⁸⁶Sr ratios were 0.710698 and 0.710512 for apricot and 0.710929 and 0.711003 for broomcorn millet. This demonstrates uninterrupted cultivation of broomcorn millet in Kuča during the Sui and Tang dynasties, with all crops and fruits sourced locally.

The Mūlasarvāstivāda Vinaya (根本萨婆多部律摄) stipulates: "If monasteries possess fields, gardens or livestock, they should entrust hired laborers for cultivation. The monastery may collect land taxes or a share of cereals to support the sangha. Should hired laborers till the land themselves, all grains, vegetables and fruits produced become impure". This indicates that monks at Taitai'er Caves likely organized agricultural activities through hired laborers on monastic-owned farmlands, achieving self-sufficiency. By the Sui and Tang dynasties, agriculture in Kuča had matured significantly, with monastic production reaching advanced levels. Agricultural tools and iconographic evidence confirm that the agricultural productivity of monasteries is highly developed. Stone sickles dating to 1000–600 BC were discovered at the Kizil Cemetery in Baicheng County.

The Ox Ploughing Scene in the Five Realms Reincarnation Scene(五趣轮回图—牛耕图) of Cave 175 at Kizil Caves depicts a scene of two yoked oxen pulling a plough, with a farmer holding the plough handle and wielding a whip to drive the cattle. The Tilling Scene(五趣轮回图—耕作图) in the same Scene demonstrates the use of Kantuman (坎土曼,broad-bladed hoes) for cultivation in Kuča. Meanwhile, adjacent cave structures—including niche caves, irregular-shaped caves, cross-shaped caves, and storage caves—likely served as monastic granaries or warehouses. The discovery of farming tools, agricultural murals and storage caves indicates that Buddhist monasteries probably owned cultivated lands. By organizing efficient agricultural production, they achieved self-sufficiency and even utilized grain reserves to mitigate risks.

Developed agriculture formed the core of monastic economies, simultaneously providing the foundation for monasteries to fulfill their social functions. As Jacques Gernet observed in Buddhist Monasteries in Chinese Society from the Fifth to the Tenth Centuries: from the Southern and Northern Dynasties to the Sui and Tang Dynasties, monasteries accumulated land through imperial grants, lay donations (donating farmlands to monasteries), and land reclamation (e.g, Guoqing Temple in Tiantai Mountain reclaiming forested land). Dependent laborers (净人) attached to monasteries tilled these lands, with harvests sustaining monastic daily life and ritual activities. In addition, monasteries was involved in tea cultivation, fruit orcharding, animal husbandry and selective logging. Land constituted a vital component of monastic property, while agrarian production provided stable funding and raw materials for the development of handicrafts and commerce. in the process of production, monasteries engaged with surrounding communities through land leasing and labor hiring. Guided by the principles of universal salvation and merit accumulation, they participated in infrastructure projects like bridge and road construction, as well as social relief efforts. Thus, Buddhist monasteries emerged as integral pillars in ancient societies.

Analysis of plant remains from the Taitai'er Caves and related literature reveals that Theravada Buddhist monasteries in Kuča achieved a balance between religious precepts and material production. While Theravada doctrine strictly prohibits monks from engaging in farming—as stated in Volume 4 of the Abhidharma-samuccaya-vyākhyā(阿毗达磨集异门足论) that digging earth with one's own hands and destroying plants constitute offenses requiring public censure. However, strontium isotope analysis demonstrates that crops and fruits unearthed at the cave were locally cultivated in Kuča. Thus, monastic communities at Taitair likely hired labor for agricultural activities surrounding the monastery.

Situated at a crossroads of civilizations along the Silk Road, the monastic economy of Taitai'er Caves developed a unique adaptive model under dual constraints of ecological limitations and Theravada Buddhist precepts. Confined by the high-altitude, arid basin environment with poor hydrothermal conditions, monastic communities primarily relied on cereals with strong stress resistance: broomcorn millet and barley, supplemented by foxtail millet and wheat. Fruits such as apricot (Armeniaca vulgaris), peach (Amygdalus persica), grape (Vitis vinifera), walnut(Juglans regia) and gourd (Lagenaria siceraria) provided essential dietary diversification .

Bound by monastic doctrines prohibiting direct farming, most Buddhist monks in Kuča served primarily as managers of monastic agricultural production, relying on hired labors for fieldwork. Theravada Buddhist monks were largely confined to processing activities such as grain dehusking. Monasteries accumulated farmlands through land grants, devotee donations and reclamation initiatives, while also managing orchards—thus diversifying their economic structure. Strontium isotope analysis confirms that plant remains unearthed in Taitai'er Caves were locally cultivated. The persistent utilization of broomcorn millet during the Sui and Tang dynasties further attests to the integration of alms-begging tradition with localized supply mechanisms.

This study reconstructs the agriculture patterns and monastic dietary practices of Kuča Buddhist monasteries based on archaeobotanical evidence unearthed from Taitai'er Caves, offering new perspectives for understanding socio-economic role of Buddhist monasteries along the Silk Road. It should be noted, however, that the strontium isotope analysis in this research relies on a limited sample size. The conclusions drawn thus remain preliminary inferences. Future studies with expanded sample sizes would significantly enhance the validation of our findings.