S-Space College of Natural Sciences (자연과학대학) Dept. of Earth and Environmental Sciences (지구환경과학부) Theses (Master's Degree_지구환경과학부)
Role of climate variables on changes in spring phenology over boreal forests in the Northern Hemisphere
북반구 한대림에서 기후 변수가 봄철 식물계절 현상의 변화에 끼치는 영향
- 자연과학대학 지구환경과학부
- Issue Date
- 서울대학교 대학원
- spring vegetation phenology; boreal forest; climate changes; CLM4.5; GIMMS LAI; winter precipitation; interannual variability
- 학위논문 (석사)-- 서울대학교 대학원 자연과학대학 지구환경과학부, 2017. 8. 허창회.
- Observations show significant influence of climate changes on vegetation green-up, an important event in terrestrial carbon and water cycle. While recent spring warming is considered as a main cause in the advance of vegetation green-up, but changes in precipitation, humidity, and solar radiation prior to the green-up may modulate leaf-onset date as well. Quantifying the influences of each climate variable on the change in spring phenology is one of great challenges due to limitation of observational analyses. Here, the author examines the effect of temperature, precipitation, specific humidity, and insolation on trend and interannual variability of the start date of growing season (SOS) over boreal forests (>40°N) during 1982─2005 based on a set of experiments using Community Land Model version 4.5 (CLM4.5). The CLM4.5 experimental set consists of one control experiment including all changes in climate variables and four sensitivity experiments, which can isolate the impact of each climate variables. Results indicate that the change in the surface temperature is the main driver for the SOS trend (−0.47 day/decade) for the analysis period. Other climate variables played a supportive role on the SOS changes, but their contributions are relatively small. In terms of interannual variability, spring temperature, humidity, and insolation are significantly related with SOS changes (correlation coefficient, r =−0.62, −0.45, and −0.45, respectively). The SOS variation is not significantly correlated with changes in spring precipitation (r =0.08). It is found that SOS is delayed by 1.04 days over 69.5% of the analysis domain due to 8.1°C decrease in the growing degree-days during spring (April and May) when winter precipitation (December to March) anomaly is higher than its one standard deviation. Our results suggest that temperature is a main cause of SOS change on interannual and decadal time scale, but impacts of other climate variables on interannual variability of SOS are considerable. This study highlights the impacts of precipitation, humidity, and insolation on SOS in boreal forests and suggests that these variables as well as temperature should be considered for accurate prediction of changes in spring vegetation phenology.