Abstract
The formation of many nebkha dunes relies on the layering of clonal plants. The microenvironmental conditions of such phytogenic nebkha are heterogeneous depending on the aspect and slope. Exploring the effects of aspect on clonal reproduction and biomass allocation can be useful in understanding the ecological adaptation of species. We hypothesized that on the windward side layering propagation would be promoted, that biomass allocation to leaves and stems of ramets would increase, and that the effects of aspect would be greater in the layering with larger biomass. To test these hypotheses, we surveyed the depth of germination points of axillary buds, the rate of ramet sprouting, the density of adventitious root formation points, and the biomass of modules sprouting from layering located on the NE, SE, SW and NW, aspects of Nitraria tangutorum nebkhas. The windward side was located on the NW and SW aspects. The results indicated that conditions of the NW aspect were more conducive to clonal reproduction and had the highest rate of ramet sprouting and the highest density of adventitious formation points. For the modules sprouting from layering on the SW aspect, biomass allocation to leaves and stems was greatest with biomass allocation to adventitious roots being lowest. This result supported our hypothesis. Contrary to our hypothesis, the effects of aspect were greater in layering of smaller biomass. These results support the hypothesis that aspect does affect layering propagation capacity and biomass allocation in this species. Additionally, clonal reproduction and biomass allocation of modules sprouting from layering with smaller biomass was more affected by aspect. These results suggest that the clonal growth of N. tangutorum responses to the microenvironmental heterogeneity that results from aspect of the nebkha.
Highlights
Nebkhas are composed of wind-borne sediment within or around the canopies of plants and are an adaptive feature of the growth of plants in arid and semiarid regions [1,2,3]
Depth of germination point of axillary buds There was a significant difference in the depth of axillary bud germination points found in layering from different aspects (ANOVA: F = 4.878, P = 0.004), which were significantly higher on the SE and SW than on the NE and NW (Fig. 1A)
The germination points of axillary buds on the layering of N. tangutorum were deeper on the SE and SW aspect sections of the nebkhas than on the NE and NW aspect sections
Summary
Nebkhas are composed of wind-borne sediment within or around the canopies of plants and are an adaptive feature of the growth of plants in arid and semiarid regions [1,2,3]. These phytogenic mounds are the habitat of many clonal plants that perform advantageous clonal reproduction [4,5] through layering modules. The whole clonal plant can increase its survival and regenerate through layering. The microenvironmental conditions on different aspects of a clonal plant nebkha may have marked effects on the growth and development of the plants
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