Johann Sievers, a German pharmacist and botanist, participated in a Russian expedition to the southern mountains of Siberia in 1790-1795. One of its objectives was to find medicinal rhubarb (Rheum palmatum), and sites where it could be grown, but he collected a wide variety of plants during the five-year journey. Among these were wild apples in south-east Kazakhstan and the first recorded example of Picea schrenkiana (Fisch. & C.A. Mey) Lindl. & Gordon.

Sievers travelled in the Yablonoi Mountains in 1791, and in 1792 crossed the Irtysh and Bukhtarma rivers in the Altai Mountains. In 1793 he explored the Tarbagatai Mountains and reached the Alakol Lake, traversing into Chinese territory in 1794. Sievers is credited with being the first botanist to visit the Tarbagatai Mountains, according to E. Bretschneider.

Sievers sent letters to the botanist P.S. Pallas in St. Petersburg, who published them in his Neueste Nordische Beyträge in 1796. Pallas also published an enumeration of Sievers' collections in Nova Acta Academiae Scientiarum Imperialis Petropolitanae (1797).

Sievers was born in Peine, Germany, and died suddenly at the age of 33. Artemisia sieversiana Ehrh. Ex Willd. and Malus sieversii (Ledeb.) M.Roem. (initially named Pyrus sieversii) are named in his honour.

Sources:
E. Bretschneider, 1898, History of European Botanical Discoveries In China, 1: 313
P.S Pallas and J. Sievers, 1796, "Sievers Briefe", Neue Nordische Beyträge, 7(3): 143-370.