Xu Weizhou, Deng Xiping, Xu Bingcheng, Palta Jairo A, Chen Yinglong
College of Life Sciences, Yulin University, Yulin, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, China.
Front Plant Sci. 2021 Oct 22;12:723839. doi: 10.3389/fpls.2021.723839. eCollection 2021.
The grasslands on the semi-arid Loess Plateau of China are expected to be particularly responsive to the size and frequency changes of extreme precipitation events because their ecological processes are largely driven by distinct soil moisture pulses. However, the plant growth and competitiveness of co-dominant species in response to the changes in the amount and timing of soil water are still unclear. Thus, two co-dominant species, and , were grown in seven mixture ratios under three watering regimes [80 ± 5% pot soil capacity (FC) (high watering), 60 ± 5% FC (moderate watering), and 40 ± 5% FC (low watering)] in a pot experiment. The soil water contents were rapidly improved from low to moderate water and from moderate to high water, respectively, at the heading, flowering, and maturity stages of , and were maintained until the end of the growing season of each species. The biomass production of both species increased significantly with the increased soil water contents, particularly at the heading and flowering periods, with a more pronounced increase in in the mixtures. The root/shoot ratio of both species was decreased when the soil water availability increased at the heading or flowering periods. The total biomass production, water use efficiency (WUE), and relative yield total (RYT) increased gradually with the increase of in the mixtures. The relative competition intensity was below zero in , and above zero in . The competitive balance index calculated for was increased with the increase of the soil water contents. responded more positively to the periodical increase in soil water availability than , indicating that the abundance of could increase in relatively wet seasons or plenty-rainfall periods. In addition, the mixture ratio of 10:2 ( to ) was the most compatible combination for the improved biomass production, WUE, and RYTs across all soil water treatments.
中国半干旱黄土高原的草原预计对极端降水事件的规模和频率变化尤为敏感，因为其生态过程在很大程度上受明显的土壤水分脉冲驱动。然而，共优势物种的植物生长和竞争力对土壤水分数量和时间变化的响应仍不清楚。因此，在盆栽试验中，将两种共优势物种[物种名称缺失]以七种混合比例种植在三种浇水处理下[80±5% 盆栽土壤持水量（田间持水量）（高浇水）、60±5% 田间持水量（中浇水）和40±5% 田间持水量（低浇水）]。在[物种名称缺失]的抽穗期、开花期和成熟期，土壤含水量分别从低水迅速提高到中水，从中水迅速提高到高水，并维持到每个物种生长季节结束。两种物种的生物量生产均随土壤含水量增加而显著增加，尤其是在抽穗期和开花期，混合种植中[物种名称缺失]的增加更为明显。在抽穗期或开花期，当土壤水分有效性增加时，两种物种的根冠比均降低。混合种植中，总生物量生产、水分利用效率（WUE）和相对总产量（RYT）随[物种名称缺失]比例增加而逐渐增加。[物种名称缺失]的相对竞争强度低于零，[物种名称缺失]的相对竞争强度高于零。为[物种名称缺失]计算的竞争平衡指数随土壤含水量增加而增加。[物种名称缺失]对土壤水分有效性的周期性增加反应比[物种名称缺失]更积极，这表明在相对湿润季节或多雨时期，[物种名称缺失]的丰度可能增加。此外，在所有土壤水分处理中，10:2（[物种名称缺失]与[物种名称缺失]）的混合比例是提高生物量生产、WUE和RYT的最适宜组合。
