Dynamic Changes in Plant Resource Use Efficiencies and Their Primary Influence Mechanisms in a Typical Desert Shrub Community

Understanding plant resource use efficiencies (RUEs) and their tradeoffs in a desert shrub community, particularly as it concerns the usage of water, light, and nitrogen, remains an ecological imperative. Plant RUEs have been widely used as indicators to understand plant acclimation processes to unfavorable environmental conditions. This study aimed to examine seasonal dynamics in RUEs in two widely distributed plant species in a typical desert shrub community (i.e., Artemisia ordosica and Leymus secalinus) based on in-situ measurements of leaf photosynthesis, specific leaf area (SLA), leaf nitrogen concentration (i.e., Nmass + Narea), and several site-related abiotic factors. Both species exhibited significant seasonal variation in RUEs, with a coefficient of variation (CV) > 30% and seasonal divergence among the various RUEs. Seasonal divergence was largely controlled by variation in stomatal conductance (Gs), which was in turn influenced by variation in soil water content (SWC) and water vapor pressure deficit (VPD). RUEs between species converged, being positively correlated, yielding: (i) r2 = 0.40 and p < 0.01 for WUE; (ii) r2 = 0.18 and p < 0.01 for LUE；and (iii) r2 = 0.25 and p < 0.01 for NUE. RUEs for A. ordosica were mostly larger than those for L. secalinus, but less reactive to drought. This suggests A. ordosica was more conservative in its usage of available resources and was, therefore, better able to adapt to arid conditions. Resource use strategies between species differed in response to drought. Desert shrubs are projected to eventually replace grasses, as drought severity and duration increase with sustained regional climate change.

Taxonomy of Ctenomys (Rodentia: Ctenomyidae) in northwestern Patagonia, Argentina: the occurrence of the “mendocinus” lineage

Subterranean rodents Ctenomys are iconic representatives of the mammalian fauna from southern South America. Based on molecular data, eight lineages have been identified within the genus, although species-level identifications and relationships are still debated. Until now, the “magellanicus” clade has been the only lineage mentioned from arid, extra-Andean portions of Patagonia. Here, we report the presence of a Ctenomys population from northern Patagonia that is unambiguously associated with the Central Argentinean “mendocinus” lineage. Most of the 160,000 km2 comprising the northern portion of Patagonia – an area consisting primarily of Monte Desert shrub-land – are inhabited by Ctenomys populations of unknown taxonomy.