Patterns and Environmental Determinants of Medicinal Plant : Vascular Plant Ratios in Xinjiang, Northwest China

<div><p>With both a full collection of native vascular plant distributions and a full checklist of source plants of the Chinese Materia Medica (CMM), the Uygur Medicine (UM), and the Kazak Medicine (KM) for the Xinjiang region, we defined medicinal plant: vascular plant ratios (simplified as medicinal plant ratios hereafter) as the value of medicinal plant richness divided by vascular plant richness. We aimed to find whether the ratios are constant or change in different environments, which environmental variables determine medicinal plant ratios, and whether the ratios are more influenced by human or by natural environments. Finally, suggestions for medicinal plant conservation were addressed. We found that (1) medicinal plant ratios were not constant, and they were high in the Tarim Basin which was largely covered by desert, while they were relatively low in mountainous areas, especially in the Tianshan Mountains where the general species richness was high; (2) medicinal plant ratios were not significantly influenced by human activities, indicated by human population density distributions, but they were highly correlated with plant species richness and climate, i.e. ratios decreased with plant species richness and MAP, and were related quadratically with MAT; (3) CMM ratio and UM ratio were more influenced by plant richness than by climate, while KM ratio was more influenced by climate. We concluded that the percentages of plants used as medicines were not influenced by distances from human settlements, but were determined by species richness or climate. We suggest that (1), in general, the medicinal plant ratio could be a complementary indicator for medicinal plant conservation planning and (2), for the region of Xinjiang, not only high diversity areas, but also some extreme environments should be considered as compensation for a better protection of medicinal plants.</p></div

The effects of climate (energy and water availability) and plant species richness on medicinal plant ratios as results from the Partial Redundancy Analysis (PRDA).

<p>The effects of climate (energy and water availability) and plant species richness on medicinal plant ratios as results from the Partial Redundancy Analysis (PRDA).</p

Distribution patterns of medicinal plant ratios in Xinjiang, China.

<p>For (a) CMM ratio, (b) UM ratio, and (c) KM ratio; Geographical divisions of Xinjiang are shown [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158405#pone.0158405.ref028" target="_blank">28</a>].</p

The RDA of the three ratios and the environmental variables (CMM ratio + UM ratio + KM ratio ~ Plant species richness + Population + MAT + MTCM +MAP + WD).

<p>The RDA of the three ratios and the environmental variables (CMM ratio + UM ratio + KM ratio ~ Plant species richness + Population + MAT + MTCM +MAP + WD).</p

The relationship of medicinal plant ratio and plant species richness.

<p>For (a) CMM ratio, (b) UM ratio, and (c) KM ratio.</p

The relationship of medicinal plant ratio with climatic variables.

<p>With MAP for CMM ratio (a), UM ratio (b), and KM ratio (c); with MAT for CMM ratio (d), UM ratio (e), and KM ratio (f).</p

The effects of plant species richness, population, and climate on the medicinal plant ratios of CMM, UM, and KM as results from the General Linear Models (GLMs).

<p>The effects of plant species richness, population, and climate on the medicinal plant ratios of CMM, UM, and KM as results from the General Linear Models (GLMs).</p