SAUSSUREA

Sasssurea laniceps and S. medusa (Cardueae, Asteraceae) (Lipschitz 1979) are two of the species known in Asia as “Snow Lotus” (or mig stog gang lha in Tibetan). These species are harvested for medicine in regions of China and Tibet (Yang et al. 2003). Tibetans use Snow Lotus medicinally to treat high blood pressure, other blood disorders, and ailments associated with pregnancy and menstruation (Ge 1989). Tibetan doctors claim that the medicinal properties of Saussurea spp. are greatest during flowering, before seed set. Thus, most plant collection occurs from late July through early September, when Snow Lotus is flowering but not yet reproducing.

Saussurea laniceps is the larger of the two species and is limited to the northwest of Yunnan Province in China. It has green leaves and flowers that are packed by pubescent bracts (Tsukaya 2001). S. medusa is smaller in size and has a wider range, encompassing northwest Yunnan and areas of southeastern Tibet. It has purple leaves and exposed flowers (Tsukaya 2002). S. laniceps is collected preferentially because of its larger size and higher market value, and so experiences much heavier harvest pressures. Both of these Saussurea spp. are high alpine plants growing at approximately 4000 meters. S. laniceps usually grows on cliffs and rocky surfaces above 4000 meters on west facing slopes (Wayne Law, MO, personal observation) but has been reported to grow from 3200-5280 meters (Chen 1999). S. medusa is usually found from 3500 to 4300 meters on east facing, rocky scree slopes (Law, personal observation) but has been reported to grow from 3000 to 5600 meters (Chen 1999). Pollen of both species has been found on individuals of Bombus rufofaciatus (P.H. Williams, Nat. History Mus., London. pers. comm.), a common bumblebee found in the mountains east of Tibet.

Saussurea laniceps and S. medusa are both monocarpic plants, meaning that they only have a single flowering period during the lifetime of the plant. With such a distinctive life history, plants with this reproductive strategy are particularly susceptible to harvest, yet they are rarely the focus of harvest impact studies. The goal of the study now being conducted by WLBC-associate Wayne Law is to understand the consequences of harvesting Saussurea. The problem will be approached from three dfferent angles. First, by utilizing techniques of matrix modeling, the impacts of harvesting on growth rates of populations from both species will be assessed. Secondly, herbarium specimens collected in the past will be used to see whether harvesting is impacting S. laniceps and S. medusa in an evolutionary sense. As has been seen in fisheries, removal of the larger fish causes the remaining fish to reproduce earlier and at a smaller size, thereby decreasing yield (Conover and Munch 2002). Human harvesters tend to collect larger, more noticeable, plants, and it is suspected that a trend similar to that seen in fish might occur in Saussurea. Finally, the impact of human harvesting on pollination rates within plant populations will be examined. Removal of flowering plants will decrease the number of flowering individuals in a population. It has been found that plant populations can be less attractive to pollinators if population size decreases (Agren 1996) and/or densities drop (Groom 1998; Mustajarvi et al. 2001). As a result reduced pollinator attraction produces negative effects on plant population growth rates due to decreased seed set (Forsyth 2003). This study should shed light on the evolutionary and ecological effects of harvesting, and also help researchers to devise conservation strategies before these plants populations, and a part of Tibetan culture, become extinct.

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This work is supported by NSF Grants # 0408123 and # 0413496.