Abstract
Increases in nitrogen (N) deposition and variation in precipitation have been occurring in temperate deserts; however, little information is available regarding plant phenological responses to environmental cues and their relationships with plant growth pattern in desert ecosystems. In this study, plant phenology and growth of six annuals in response to N and water addition were monitored throughout two consecutive growing seasons in 2011 and 2012 in a temperate desert in northwestern China. The effects of N and water addition on reproductive phenology differed among plant species. N and water addition consistently advanced the flowering onset time and fruiting time of four spring ephemerals; however, their effects on two spring‐summer annuals were inconsistent, with advances being noted in one species and delays in another. N and water addition alone increased plant height, relative growth rate, leaf number, flower number, and individual biomass, while their combinative effects on plant growth and reproductive phenology were dependent on species. Multiple regression analysis showed that flowering onset time was negatively correlated with relative growth rate of two species, and negatively correlated with maximum plant height of the other four species. Our study demonstrates that phenological responses to increasing precipitation and N deposition varied in annuals with different life histories, whereby the effects of climate change on plant growth rate were related to reproductive phenology. Desert annuals that were able to accelerate growth rate under increasing soil resource availability tended to advance their flowering onset time to escape drought later in the growing season. This study promotes our understanding of the responses of temperate desert annuals to increasing precipitation and N deposition in this desert.
Highlights
Phenology is the onset time and duration of biological events, and it determines species fitness and coexistence in plant communities (Forrest & Miller-Rushing, 2010)
The specific aims of our study were to (1) assess whether N and water addition would alter plant growth patterns and phenophases, including flowering onset time, fruiting time, seed maturation time, and reproductive duration; (2) test whether plant phenological responses to N and water addition would be consistent among species or between two life-history strategies (3) explore the role of plant growth traits in reproductive phenological responses, and determine how this is modified by water and N availability
Our study shows that the combination of N and water addition only advanced flowering onset time and fruiting time of C. arenarius
Summary
Phenology is the onset time and duration of biological events, and it determines species fitness and coexistence in plant communities (Forrest & Miller-Rushing, 2010). There are three typical plant growth patterns in response to resource availability in desert ecosystems: Drought-escape ephemerals only use soil resources at the first nutrient and water pulse in early spring; such a one bet strategy carries a risk of utter reproductive failure if resources are only available for a very short period (Figure 1curve A). Drought avoiding spring-summer annuals can survive drought periods through slow growth or aboveground dormancy and maintain reproduction in later resource pulses in autumn (Curve C). Species with these distinct life-history strategies may respond differently to water or N availability and modify the species coexistence in desert ecosystems (Rasmussen, Van Allen, & Rudolf, 2014; Zhang, Hu, & Zhang, 2016). The specific aims of our study were to (1) assess whether N and water addition would alter plant growth patterns and phenophases, including flowering onset time, fruiting time, seed maturation time, and reproductive duration; (2) test whether plant phenological responses to N and water addition would be consistent among species or between two life-history strategies (3) explore the role of plant growth traits in reproductive phenological responses, and determine how this is modified by water and N availability
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