Allocation of limiting resources, such as nutrients, is an important adaptation strategy for plants. Plants may allocate different nutrients within a specific organ or the same nutrient among different organs. In this study, we investigated the allocation strategies of nitrogen (N) and phosphorus (P) in leaves, stems and roots of 126 shrub species from 172 shrubland communities in Northern China using scaling analyses. Results showed that N and P have different scaling relationships among plant organs. The scaling relationships of N concentration across different plant organs tended to be allometric between leaves and non-leaf organs, and isometric between non-leaf organs. Whilst the scaling relationships of P concentration tended to be allometric between roots and non-root organs, and isometric between non-root organs. In arid environments, plant tend to have higher nutrient concentration in leaves at given root or stem nutrient concentration. Evolutionary history affected the scaling relationships of N concentration slightly, but not affected those of P concentration. Despite fairly consistent nutrients allocation strategies existed in independently evolving lineages, evolutionary history and environments still led to variations on these strategies.

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A survey was made of the arbuscular mycorrhizal (AM) status of 73 spring ephemeral plant species that grow in the desert ecosystem of Junggar Basin, northwest China. The proportion of AM colonization ranged from 7 to 73% with a mean value of 30%. A total of 65 plant species studied were AM with coils/arbuscules or vesicles and the remaining eight species were possibly AM with no coils/arbuscules or vesicles but with fungal mycelia in the root cortex. AM fungal spores were isolated from rhizosphere samples of all 73 plant species and identified. The mean spore density was 22 per 20 ml of air-dried soil, ranging from 0 to 120. Colonization and spore density of perennials were slightly higher than of annuals and varied among different plant families. A total of 603 AM fungal spore (or sporocarp) specimens were isolated belonging to six genera, Acaulospora, Archaeopora, Entrophospora, Glomus, Paraglomus, and Scutellospora; Glomus was the dominant genus. We conclude that spring ephemerals may be highly dependent on AM associations for survival in the very infertile and arid soils of this desert ecosystem.

Colonization by and diversity of arbuscular mycorrhizal (AM) fungi associated with five common ephemerals, Eremopyrum orientale (L.) Jaub. et Spach., Gagea sacculifera Regel., Plantago minuta Pall., Tragopogon kasahstanicus S. Nikit., and Trigonella arcuata C. A. Mey. were investigated in four typical desert plant communities in Junggar Basin, northwest China. All five ephemerals examined were found to be colonized and formed typical arbuscules or vesicles. The proportion of root length colonized ranged from 2 to 85% with an average of 19%. Spore density in soil near the roots of different ephemerals varied from 1 to 120 spores per 20 ml soil, with an average value of 33 spores. Species richness averaged 8.8 AM fungal species in soil near the roots and ranged from 2 to 21. Fifty-four AM fungal taxa belonging to the genera Acaulospora, Archaeospora, Entrophospora, Glomus and Paraglomus were isolated and identified from soil around the roots. Glomus was the dominant AM fungal genus with a frequency of 100% and relative abundance of 82.6%. The AM fungal species with the highest frequency of occurrence was Glomus aggregatum with a frequency of 75%. G. microaggregatum was present in the highest relative abundance (16%). G. sacculifera, P. minuta and T. arcuata formed Arum-type mycorrhizas. Arbuscular mycorrhizal fungi are ubiquitous and Arum-type mycorrhizas are especially prevalent in these important desert communities used for grazing and traditional medicine.