Characterizing Growing Season Length of Subtropical Coniferous Forests with a Phenological Model

Yuan Gong,Yinlong Zhang,Christina L Staudhammer,Gregory Starr,Susanne Wiesner

doi:10.3390/f12010095

Yuan Gong, Yinlong Zhang + Show 3 more

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https://doi.org/10.3390/f12010095

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Abstract

Understanding plant phenological change is of great concern in the context of global climate change. Phenological models can aid in understanding and predicting growing season changes and can be parameterized with gross primary production (GPP) estimated using the eddy covariance (EC) technique. This study used nine years of EC-derived GPP data from three mature subtropical longleaf pine forests in the southeastern United States with differing soil water holding capacity in combination with site-specific micrometeorological data to parameterize a photosynthesis-based phenological model. We evaluated how weather conditions and prescribed fire led to variation in the ecosystem phenological processes. The results suggest that soil water availability had an effect on phenology, and greater soil water availability was associated with a longer growing season (LOS). We also observed that prescribed fire, a common forest management activity in the region, had a limited impact on phenological processes. Dormant season fire had no significant effect on phenological processes by site, but we observed differences in the start of the growing season (SOS) between fire and non-fire years. Fire delayed SOS by 10 d ± 5 d (SE), and this effect was greater with higher soil water availability, extending SOS by 18 d on average. Fire was also associated with increased sensitivity of spring phenology to radiation and air temperature. We found that interannual climate change and periodic weather anomalies (flood, short-term drought, and long-term drought), controlled annual ecosystem phenological processes more than prescribed fire. When water availability increased following short-term summer drought, the growing season was extended. With future climate change, subtropical areas of the Southeastern US are expected to experience more frequent short-term droughts, which could shorten the region’s growing season and lead to a reduction in the longleaf pine ecosystem’s carbon sequestration capacity.

Highlights

Introduction nal affiliationsForested ecosystems play an important role in the global carbon cycle [1,2], and are among the largest terrestrial carbon sinks [3,4]
The estimated parameters of the phenology model indicated that gross primary production (GPP) differed by year and site, and that sites differed in their response to weather events (Table 2; Appendix B, Figure A2)
The eddy covariance (EC) sites are in close proximity to one another and share a similar climatic environment [42], there were still slight differences among sites in terms of phenological characteristics derived from daily GPP

Summary

Introduction

Introduction nal affiliationsForested ecosystems play an important role in the global carbon cycle [1,2], and are among the largest terrestrial carbon sinks [3,4]. It has been hypothesized that forests may have the ability to increase their carbon sequestration capacity as a means to mitigate rising atmospheric CO2 concentrations [5,6]. This increase will likely be through phenological changes, as future model projections indicate that by the end of this century, the growing season length will increase by 29–43 days [7]. Knowledge regarding phenological characteristics of different forests, the length of the growing season, can contribute to a better understanding of the terrestrial carbon cycle with global change [13]

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