1 Introduction
The timing and duration of plant flowering affect plant survival,
reproduction and community assembly dynamics (Collins
et al., 2021; Forrest et al.,
2010). Our planet is currently experiencing abrupt environmental
changes, including rising air temperatures and increased atmospheric
nitrogen (N) deposition (IPCC, 2023). Numerous studies have demonstrated
that warming leads to earlier flowering across the Northern Hemisphere
(Piao et al., 2019; Shen et al., 2018; Wolkovich et al., 2012). To
understand how these changes in plant phenology will affect the
structure of ecosystems, it is crucial to understand the relative
responses of different plant types to climate change (Collins et al.,
2021; Piao et al., 2019; Post et al., 2008).
The effects of N deposition on flowering phenology are complex and can
differ among species, plant functional groups and ecosystems (Zhou et
al., 2023; Xia et al., 2015). For instance, in a semiarid, alpine meadow
ecosystem on the central Tibetan Plateau, N addition resulted in delayed
flowering of grasses, but slightly advanced flowering of forbs (Dorji et
al., 2013). The responses of plant flowering phenology to both warming
and N deposition are likely regulated by soil resource availability and
plant resource acquisition, which are closely tied to plant traits,
particularly in arid and semi-arid regions (Nord et al., 2009; Xia &
Wan, 2013). The efficiency of nutrient and water absorption by plants
can also impact their phenology (Dorji et al., 2013; Post et al., 2008).
Plant phenology affects plant growth and its temporal dynamics (Cleland
et al., 2007). It, however, is less clear to what extent plant phenology
influences community assembly and competition dynamics (Stone et al.,
1998; Menzel, 2002; Piao et al., 2019). Differences in flowering times
can affect plant density, thereby reducing pollinator competition or
interspecific pollen transfer in symbiotic species (Wolf et al., 2017).
Variation in phenological responsiveness can thus have a significant
influence on population competition dynamics (Alexander & Levine, 2019;
Wolkovich et al., 2012). Early-flowering plants may possess certain
advantages over other competitors within the population, thus enabling
them to adjust their strategies and adapt to a warming world (Fu et al.,
2015). Conversely, plants that fail to keep pace with climate change may
face disadvantages, but may also benefit if highly responsive species
more frequently encounter climate risks, such as increased late frost
damage (Cleland et al., 2012). However, we lack empirical evidence
linking dryland plant phenology with community composition under field
conditions.
Here, we present findings from a long-term (17-year) field manipulation
experiment conducted in a temperate desert steppe in northern China. Our
study region was located in the interior of the Asian continent, where
particularly high rates of climate change
have been observed (Zhang et al.,
2011). We examined the responses of plant phenology to climate warming
and N deposition, and tested the potential implications of these
phenological changes on species composition. Our experiment aimed to
address two research questions. Firstly, we investigated the
differential effects of climate warming and nitrogen deposition on plant
flowering phenology in a desert steppe. Secondly, we explored how the
differences in plant phenological responses to changes in temperature
and nitrogen availability contribute to shifts in plant community
composition, specifically the relative abundance of C3and C4 plants in a community. By addressing these
questions, our study provides unique insights into the dynamics of plant
phenology and community composition in response to global change in the
temperate desert steppe ecosystem.