Soil nutrient supply modulates temperature‐induction cues in mast‐seeding grasses

Abstract

Abstract. Synchronous and intermittent reproduction in long-lived plants, known as mast seeding, is induced by climatic cues, but the mechanism explaining variation in masting among neighboring but edaphically segregated species is unknown. Soil nutrients can enhance flowering, and thus, populations on nutrient-rich soils may require less-favorable growing temperatures to flower. We tested this hypothesis by predicting the probability of flowering in response to air temperature for five species of alpine Chionochloa grasses in South Island, New Zealand, over 37 years and relating our predictions to soil N supply (NH 4 þ þ NO 3 À ). Summer air temperatures better predicted flowering than spring air temperatures, which were correlated with soil N mineralization. Species on N-rich soils required lower mean temperatures to induce flowering and/or responded more consistently across a gradient of air temperatures, contributing to the higher probability of their tillers and tussocks flowering at low summer temperatures. Our results suggest that flowering primarily occurs in response to warm summer temperatures, but species on N-rich soils require less favorable growing conditions because they invest relatively less N in seeds. Thus, predicting masting requires a consideration of the interactions among climate, the internal resources of plants, and mineral nutrient uptake.

Contrasting bacterial communities in two indigenous Chionochloa (Poaceae) grassland soils in New Zealand

“…teretifolia soils, which have a higher C:N ratio compared to C . pallens soils [33]. Actinobacterial abundance in soil was previously positively correlated with total microbial biomass and C:N ratio in grassland soils [35,64].…”

“…Diversification within this group resulted in more than 10 species in the region segregated according to altitude, soil conditions and snow lie [30,31]. The edaphic segregation of species influences temperature cues, flowering intensity, costs of seed production and vegetative growth [32,33]. Different species of Chionochloa exhibit adaptation to different extremes in natural soil fertility, resulting in distributions that are delimited by soil nutrients [30,32].…”

“…Different species of Chionochloa exhibit adaptation to different extremes in natural soil fertility, resulting in distributions that are delimited by soil nutrients [30,32]. Soil N-limitation is a key component differentiating nutrient-rich from nutrient-poor sites in this system [33]. It follows that nitrogen-fixing bacteria must play a significant role in providing biologically available N in the N-limited soils, therefore their diversity and abundance is expected to impact on Chionochloa resource allocation and flowering.…”

“…pallens occupies N-rich and well-drained fertile soils. These soils also differ in the proportion of organic carbon (C), Olsen phosphorus (P) and soil pH [33]. High-throughput 16S rRNA gene sequencing enables high resolution taxonomic characterization of soil bacterial communities [35–37].…”

Assessing the efficacy of population-level models of mast seeding

“…Sala et al 2012;Ichie and Nakagawa 2013). Moreover, Tanentzap et al (2012) showed the positive correlation between soil nitrogen and the mean probability of flowering for five species of Chionochloa in New Zealand. This model contained regions of parameter space that demonstrated constant, intermittent and chaotic seedfall regimes and was shown to demonstrate synchronicity under coupling through pollen limitation.…”