United States Department of Agriculture-Agricultural Research Service, Jornada Experimental Range, Box 30003, MSC 3JER, NMSU, Las Cruces, New Mexico 88003-0003 USA.
Am J Bot. 2002 Oct;89(10):1616-23. doi: 10.3732/ajb.89.10.1616.
The objective of this study was to quantify differences in recruitment potential (seed production, seed presence in the soil) for two congeneric perennial grasses (Bouteloua gracilis, Bouteloua eriopoda [Poaceae]) that dominate adjacent arid and semiarid grassland biomes. It was hypothesized that these species have different recruitment strategies at the biome transition zone that are related to differences in their growth form and longevity. Recruitment potential for each Bouteloua species was compared in patches dominated by one or both species or codominated by the invasive shrub, Larrea tridentata (Zygophyllaceae). Regional variation in recruitment was examined for B. gracilis for cases in which comparable data were available in the literature for a site located within the semiarid grassland biome. The short-lived stoloniferous species B. eriopoda produced more seeds per plant than the long-lived bunchgrass B. gracilis, yet seed viability (<60%) and presence in the soil were lower. Mean viability of B. gracilis was higher (>90%) than that of B. eriopoda, and a greater percentage of seeds produced on a square meter basis was found in the soil (10-25%). Similar patterns were found for both species in all grass-dominated patches. Bouteloua eriopoda plants growing in patches codominated by L. tridentata produced fewer seeds per plant with lower viability, and fewer seeds were found in the soil compared to grass-dominated patches. Regional comparisons found greater seed production per square meter and more seeds in the soil for B. gracilis at the transitional site compared with a cooler, wetter site located within the semiarid grassland biome. These differences in recruitment potential along with published differences in rates of seedling establishment and vegetative spread may explain, at least in part, localized patterns in species dominance.
本研究的目的是量化两种同源多年生禾本科植物（Bouteloua gracilis、Bouteloua eriopoda）在主导相邻干旱和半干旱草原生物群落中的潜在繁殖差异（种子产生、种子在土壤中的存在）。假设这些物种在生物群落过渡带具有不同的繁殖策略，这与它们的生长形态和寿命差异有关。在由一种或两种物种或入侵灌木 Larrea tridentata（Zygophyllaceae）主导的斑块中比较了每个 Bouteloua 物种的繁殖潜力。对于 B. gracilis，在文献中有可比数据的情况下，检查了其在半干旱草原生物群落中一个地点的区域繁殖变化。短命的匍匐茎物种 B. eriopoda 每株植物产生的种子比长寿命的丛生草 B. gracilis 多，但种子活力（<60%）和在土壤中的存在率较低。B. gracilis 的平均活力较高（>90%），而且每平方米产生的种子比例更高（10-25%）。在所有以草为主的斑块中，两种物种都存在类似的模式。在与 L. tridentata 共同主导的斑块中生长的 B. eriopoda 植物每株植物产生的种子较少，活力较低，在土壤中发现的种子也较少。与位于半干旱草原生物群落中的较凉爽、湿润地点相比，在过渡地点发现 B. gracilis 每平方米的种子产量更大，土壤中的种子更多。这种潜在繁殖能力的差异以及已发表的幼苗建立和营养繁殖率的差异，至少可以部分解释物种优势的局部模式。
