Dryland ecosystems are increasing in geographic extent and contribute greatly to interannual variability in global carbon dynamics. Disentangling interactions among dominant primary producers, including plants and autotrophic microbes, can help partition their contributions to dryland C dynamics. We measured the δ¹³C signatures of biological soil crust cyanobacteria and dominant plant species (C₃ and C₄) across a regional scale in the southwestern USA to determine if biocrust cyanobacteria were coupled to plant productivity (using plant-derived C mixotrophically), or independent of plant activity (and therefore purely autotrophic). Cyanobacterial assemblages located next to all C₃ plants and one C₄ species had consistently more negative δ¹³C (by 2‰) than the cyanobacteria collected from plant interspaces or adjacent to two C₄Bouteloua grass species. The differences among cyanobacterial assemblages in δ¹³C could not be explained by cyanobacterial community composition, photosynthetic capacity, or any measured leaf or root characteristics (all slopes not different from zero). Thus, microsite differences in abiotic conditions near plants, rather than biotic interactions, remain a likely mechanism underlying the observed δ¹³C patterns to be tested experimentally.

旱地生态系统的地理范围正在扩大，并极大地促进了全球碳动态的年际变化。包括植物和自养微生物在内的主要初级生产者之间的相互纠缠的相互作用可以帮助将其贡献分配给干旱地区碳动态。我们测量了δ ¹³生物结皮蓝藻和优势种的Ç签名（C ₃和C ₄跨区域规模）在美国西南部，以确定是否biocrust蓝藻被耦合到工厂生产力（使用源自植物的Çmixotrophically），或与植物活动无关（因此是纯自养的）。蓝藻菌群位于所有C ₃植物和一棵C _4附近物种一贯更负δ ¹³ C（由2‰）比从植物间隙或相邻的收集两个不同的C蓝藻₄格兰马草属草物种。在δ蓝藻组合之间的差异¹³ C可不受蓝藻群落组成，光合能力，或任何测量叶或根的特性（所有斜坡从零未不同）进行说明。因此，在靠近植物的非生物的条件下，而不是生物相互作用微型差异，仍基本观察到的δ一个可能的机制¹³ Ç图案进行实验测试。