DOI: 10.5061/dryad.gxd2547gf
title: Demography of the giant monocarpic herb Rheum nobile in the Himalayas and the effect of disturbances by grazing

description: Abstract Background Perennity of giant rosette species in combination with
 a single “big bang“ reproduction followed by death of the genetic
 individual is relatively rare among plants. Such long-lived monocarpic
 plants are usually slow growing and can be found in deserts, bogs or in
 alpine regions of the tropics or subtropics. Due to their longevity
 monocarpic perennials risk to lose everything before reproduction, which
 make them particularly susceptible to disturbances. Because of the
 inherent difficulties to assess if long-lived populations are growing or
 declining, usually neither their demography nor the consequences of
 increasing grazing pressure are known. Methods We used integral projection
 modelling (IPM) to measure growth rate and passage time to flowering of
 Rheum nobile, a monocarpic perennial, and one of the most striking alpine
 plants from the high Himalayas. We estimated the impact of grazing cattle
 (yaks) by including in the models those rosettes, which were not found any
 more due to disturbances or grazing by yaks, either as missing or dead.
 Data was collected from plants at 4500 m a.s.l. in Shangri-la County,
 Yunnan Province, southwest China. In four consecutive years (2011-14) and
 in two populations, 372 and 369 individuals were measured, respectively,
 and size-dependent growth, survival and fecundity parameters were
 estimated. In addition, germination percentage, seedling survival, and
 establishment probability were assessed. Key results The probability of
 survival, of flowering and fecundity were strongly size-dependent. Time to
 reach flowering size was 33.5 years (95% CI from 21.9 to 43.3, stochastic
 estimate from pooled transitions and populations). The stochastic
 population growth rate (λs) of Rheum nobile was 1.013 (95% CI from 1.010
 to 1.017). When disturbance by grazing cattle (yaks) was accounted for in
 the model, λs dropped to values below one (0.940, 95% CI from 0.938 to
 0.943). Conclusion We conclude that natural populations of this unique
 species are viable, but that conservation efforts should be taken to
 minimise disturbances by grazing and to protect this slow-growing flagship
 plant from the high Himalayas.
description: The demographic data of Rheum nobile was collected at two sites
 in the eastern Himalaya: Huluhai (28°31′N, 99°57′E, 4450 m a.s.l.) and
 Yongjiongyi (28°24′N, 99°55′E, 4490 m a.s.l.), in Shangri-la County,
 Yunnan Province, SW China. In four consecutive years (2011-14), 372 and
 369 individuals (rosettes), respectively, were marked and measured. Table
 1 includes the data of four consecutive years (2011-14) that was used to
 estimate the size-dependent growth, survival and fecundity parameters for
 the Integral projection Model (IPM). For each rosette the table includes
 the following: number of leaves, largest and shortest diameter of rosette
 (cm), length and width of largest leaf (cm); when an individual was
 flowering, the table includes: the number of flowers, fruit set, the
 number of fruits, the abortion rate, mature seeds, the predation rate, the
 number of viable seeds. Flowering plants died after seed ripening. In the
 column "status" it is inicated if a plant flowered in a
 particular year, was found dead due to natural mortality (die), or was
 missing or dead due to disturbance by grazing yaks (missing). 
 Table 2 includes the data that was used to calculate the
 germination rate: the number of seedlings around all the 8 and 9 plants
 reproducing in 2013 in Huluhai and Yongjiongyi respectively, were counted
 in 2014 and divided by the number of seeds produced by their mother
 plants. Table 3 includes the data that was used to
 calculate seedling survival: 5 (Huluhai) and 6 plots (Yongjiongyi) of size
 80 x 80 cm were established early in 2011 close to all plants which had
 reproduced in the preceding year. Emerging seedlings until the end of
 season 2011 in these plots were counted and the surviving seedlings and
 their size (diameter) was measured in the following year. Seedling
 survival was calculated by dividing the number of seedlings surviving in
 2012 by the number of seedlings counted in 2011. 
description: Table 1-3 are excel-sheets.