Abstract
Peatland ecosystem processes are strongly influenced by hydrology linked to climate change. However, how transpiration, as major water loss pathway in closed peatland, responds to climate change and then regulates ecosystem water balance that remains poorly understood. Here, we reported an 18,000-year fossil phytolith record from an herbaceous community-dominated mountain peatland in central China to reconstruct climate changes and vegetation evolution and reveal the interactions between regional climate changes and peatland ecosystem. The abundance of bulliform phytoliths—a silicified type of cells that regulate the movements of plant leaves to reduce light exposure and transpiration rate—shows close correlations with the Holocene climate variations with higher bulliform abundance in response to warm-dry climate (11,500–9600 cal yr BP; 7500–3000 cal yr BP) and lower values associated with cold-wet climate (13,000–11,500 cal yr BP; 3000 cal yr BP-present). Spectral analysis reveals that bulliform abundance and reconstructed climate vary with a major ~1000-year periodicity during the Holocene, suggesting a possible causal relationship to solar activity. A high bulliform abundance and warm-dry climate correspond with enhanced solar activity, and vice versa. We interpret that the resultant leaf water deficit resulted from greater light interception, high temperature and drought promoted the production of bulliform cells to fold leaf for water conservation, which is an effective protective mechanism of peatland grasses from the environmental stress. These results expand our understanding of how grass-dominated peatland plant water regulation recorded by bulliform phytoliths responds to solar radiation and local hydroclimate during geological period.
Fig.1. Time series of bulliform abundance and climate changes records from the middle Yangtze Valley. The age calibration errors and sensitivity of climate proxies could probably cause the tiny differences and shifts from independent core records.
a. Temperature changes based on the phytolith record from Core ZK5 (3-point moving average); b. BNA15-derived palaeo-temperature record in the Dajiuhu Peatland, central China (Huang et al., 2013a); c. Pollen-based temperature change from Dajiuhu Peatland (Zhu et al., 2008); d. Δδ2H between Sanbao Cave carbonate and ZK5 leaf waxes (Huang et al., 2018); e. DWT changes based on the phytolith record from Core ZK5; f. Dajiuhu hopanoid flux (Xie et al., 2013); g. Average aromatic ring (AAR) values of the Dajiuhu peat aromatic oleanenes (Huang et al., 2013b); h. Strong rainfall recorded by IRMsoft-flux from the stalagmite in Heshang Cave (Zhu et al., 2017); i. Hydrological record based on leading PC1 of Mg/Ca, Sr/Ca, and Ba/Ca in Haozhu Cave (Zhang et al., 2018); j. Bulliform phytolith abundance from Core ZK5. The red bars show evident warm-dry conditions in Dajiuhu Peatland.
Fig. 2. The cycles of the bulliform phytolith abundance, climate and solar activity.
a-d. Power spectral analysis of TSI (Steinhilber et al., 2012), phytolith-based temperature reconstruction, phytolith-based DWT reconstruction (Liu et al., 2019) and bulliform phytolith abundance. The orange, green and purple dashed lines are the 99%, 95% and 90% confidence levels (CL), respectively. e. TSI (purple solid line, temperature (red solid line), DWT (blue dashed line) and bulliform phytolith abundance (black solid line) after ~1000-year band-pass filtering. Higher TSI is representative of enhanced solar activities. The yellow bars show ten periods of high temperature. The ~1000-year cycle of climate is almost in-phase with ~1000-year solar activity cycle. The differences from independent climatic records could probably be caused by the different age models, which could probably result in the small phase shift or tiny discrepancy.
Title: Holocence peatland water regulation response to ∼1000-year solar cycle indicated by phytoliths in central China
Authors: Hongye Liu, Yansheng Gu, Zicheng Yu, Chunju Huang, Jiwen Ge, Xianyu Huang, Shucheng Xie, Min Zheng, Zhiqi Zhang, Shenggao Cheng
DOI：10.1016/j.jhydrol.2020.125169
Source: Journal of Hydrology, 2020, VOL589, 125169
Link to the paper：https://doi.org/10.1016/j.jhydrol.2020.125169
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