本地和外来草本物种对水分条件时间异质性的可塑响应

Plastic responses of native and exotic herbaceous species to temporal heterogeneity in water conditions

关键词:  水分时间异质性, 干旱, 水淹, 外来种, 本地种, 表型可塑性

Key words:  water temporal heterogeneity, drought, inundation, exotic species, native species, phenotypic plasticity

摘要:

极端气候导致的干旱和水淹事件频发,影响了外来植物和本地植物的生长。为了解外来种和本地种植物对干旱和水淹事件发生顺序的响应,探讨草本植物适应水分时间异质性的策略,该文以美国蒙大拿州西部4种本地植物和4种外来植物为研究对象,将所有植物分别进行持续湿润(对照,CK)、水淹-干旱(I-D)和干旱-水淹(D-I)处理,并观测一系列形态和生物量特征的变化。结果表明:(1)与CK相比,D-I和I-D处理均显著降低了外来种的总生物量(P<0.05)。(2)D-I显著降低了本地种早期总生物量、后期地下生物量和根冠比,但显著提高了其后期的相对生长(P<0.05)。(3)D-I处理显著降低了所有植物的地下-地上生物量关系的异速指数,外来种异速指数显著高于本地种(P<0.05)。综上认为,极端事件(水淹和干旱)的发生顺序能改变外来植物和本地植物的生物量分配,早期干旱比后期干旱更容易减少植物生物量的积累,但能促进本地种后期的生长; 本地种在环境胁迫下不被降低的总生物量表现说明维持表型稳定的能力较强; D-I处理下本地种和外来种地上和地下生物量关系的分配方式不同。

Abstract:

In recent years, many studies have shown that extreme climate events occur more frequently. The extreme climate led to frequent drought and inundation events, which affected the growth of both exotic and native plants. In order to discuss the strategies of exotic and native plants in adapting to temporal heterogeneity in water conditions by investigating their responses to the sequence of drought and inundation events, four native and four exotic perennial herbaceous species in western Montana, USA were used as study objects. All plants were treated with moderate water(CK), initial inundation before drought(I-D)and initial drought before inundation(D-I)conditions, and variations in a series of morphological and biomass traits were measured. The results were as follows:(1)Compared with CK, both D-I and I-D treatments significantly reduced the total biomass of exotic species(P<0.05).(2)D-I treatment significantly reduced the total biomass at the early stage, and late belowground biomass and root/shoot of native species, but significantly improved their later relative growth(P<0.05).(3)D-I treatment significantly reduced the scaling exponent of the allometric relationship between belowground biomass and aboveground biomass for all plants, with a higher allometric exponent for exotic species than native species(P<0.05). In conclusion, the sequence of extreme events(inundation and drought)can alter the allocation of biomass between exotic and native plants. Early drought is more likely to reduce the accumulation of plant biomass than late drought, but it can promote the growth of native species in late period. The total biomass of native species is not reduced under environmental stress, indicating that native species have a strong ability to maintain phenotypic stability. Distribution patterns of aboveground and belowground biomass relationships are different between native and exotic species under D-I treatment.