Data from: Positive effects of non-native grasses on the growth of a native annual in a southern California ecosystem

Fire disturbance is considered a major factor in the promotion of non-native plant species. Non-native grasses are adapted to fire and can alter environmental conditions and reduce resource availability in native coastal sage scrub and chaparral communities of southern California. In these communities persistence of non-native grasses following fire can inhibit establishment and growth of woody species. This may allow certain native herbaceous species to colonize and persist beneath gaps in the canopy. A field manipulative experiment with control, litter, and bare ground treatments was used to examine the impact of non-native grasses on growth and establishment of a native herbaceous species, Cryptantha muricata. C. muricata seedling survival, growth, and reproduction were greatest in the control treatment where non-native grasses were present. C. muricata plants growing in the presence of non-native grasses produced more than twice the number of flowers and more than twice the reproductive biomass of plants growing in the treatments where non-native grasses were removed. Total biomass and number of fruits were also greater in the plants growing in the presence of non-native grasses. Total biomass and reproductive biomass was also greater in late germinants than early germinants growing in the presence of non-native grasses. This study suggests a potential positive effect of non-native grasses on the performance of a particular native annual in a southern California ecosystem.火灾干扰被视为促进外来植物物种扩散的主要因素。外来草本植物对火灾具有适应性，可改变南加州本土海岸鼠尾草灌丛与查帕拉尔群落的环境条件，并降低其资源可利用性。在该类群落中，火灾后外来草本植物的存续会抑制木本物种的定植与生长，这使得部分本土草本植物得以在林冠间隙中定植并存活。本研究通过设置对照组、枯落物处理组与裸地处理组的野外控制性实验，探究了外来草本植物对本土草本物种刺鹤虱（Cryptantha muricata）的生长与定植的影响。在存在外来草本植物的对照组中，刺鹤虱的幼苗存活率、生长态势与繁殖表现均为最优。相较于移除了外来草本植物的处理组，生长在外来草本植物存在环境下的刺鹤虱个体，其开花数量与繁殖生物量均达到后者的两倍以上；其总生物量与果实数量也更高。此外，在外来草本植物存在的环境中，晚萌发个体的总生物量与繁殖生物量同样高于早萌发个体。本研究表明，在南加州的生态系统中，外来草本植物可能对特定本土一年生植物的生存表现产生潜在的正向影响。