CONTROL ID: 1487850

TITLE: Global latitudinal-asymmetric vegetation growth trends and their driving mechanisms over the past three decades

AUTHORS (FIRST NAME, LAST NAME): Jiafu Mao1, Xiaoying Shi1, Peter E Thornton1, Forrest M Hoffman2

INSTITUTIONS (ALL): 1. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.
2. Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.

ABSTRACT BODY: Using a latest global Leaf Area Index (LAI) dataset and the Community Land Model version 4 (CLM4), we investigate latitudinal percent changes and controlling factors of vegetation growth for the period 1982 to 2009. Over the past 28 years, both the observation and model show a substantial latitudinal-asymmetric LAI tendency with low increase in the Southern Hemisphere and high increase at high latitudes in the Northern Hemisphere. The observed LAI increases northward monotonically at 0.08%/°N (P<0.05), which is in similar magnitude to CLM4 prognostic latitudinal LAI change (0.09%/°N (P<0.05)). The south-to-north warming asymmetry induced by a corresponding asymmetry in the landmass area was hypothesized to be the principal driver of this latitudinal asymmetry of LAI trend. To quantify contributions from other external forcings such as climate, CO2, N deposition and land use/land cover change, a series of single-factor experiments were conducted. The climate-only simulation confirms that climate change particular the asymmetry of land temperature variation tend to explain the latitudinal pattern of LAI variation but with lower estimate of global LAI change compared to the observation for the 28-yr period. Among all the selected global forcings, CO2 fertilization was simulated to be the dominant causative factor for the enhanced vegetation growth during the last three decades.

KEYWORDS: [0414] BIOGEOSCIENCES / Biogeochemical cycles, processes, and modeling.
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CONTACT (E-MAIL ONLY): maoj at ornl dot gov