Impacts of meteorology-driven seed dispersal on plant migration : implications for future vegetation structure under changing climates

As the impacts among land cover change, future climates and ecosystems are expected to be substantial (e.g., Feddema et al., 2005), there are growing needs for improving the capability of simulating the dynamics of vegetation structure across the global landscape as accurately as possible. In order to serve these needs, Dynamic Global Vegetation Models (DGVMs) are used to describe the current status of vegetation structure and biogeography as well as estimate their future dynamics, either with prescribed climates or coupled to climate models. Yet, current DGVMs generally assume ubiquitous availability of seeds and do not generally consider seed dispersal mechanisms and plant migration processes, which may influence the impacts of vegetation structural changes on the climate system (i.e., change in albedo, runoff, and terrestrial carbon sequestration capacity). For the first time, this study incorporates time-varying winddriven seed dispersion (i.e., the SEED configuration) as a dynamic constraint to the migration of natural vegetation in the Community Land Model (CLM)-DGVM. Compared to estimates of satellite-derived tree cover, simulations by this model configuration shows significantly improved representation of boreal forests in Western Siberia and temperate forests in Eastern Europe. The prevailing wind pattern, along with the existing vegetation structure in nearby grid cells, alters the competition dynamics of the trees in these regions by filtering unrealistic plant functional types through adjustment of establishment rates. The SEED configuration was applied to project future vegetation structures under two climate mitigation scenarios (No-policy vs. 450ppm CO 2 stabilization) for the 21st century. The simulation results indicate that regional changes of vegetation structure under changing climates are expected to be significant. In the high latitudes, regions such as Alaska and Siberia are expected to experience substantial shifts of forestry structure, characterized by expansion of needle-leaf boreal forest and shrinkage of C3 grass Arctic. In the mid-latitudes, temperate trees are likely to expand in South America, South Africa, and East Asia at the expense of C3 grass during the latter part of the 21' century. In the Tropics, the most notable degree of change is in the composition of tropical trees and C4 grasses in the Amazon and in Africa.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2011

Author dc:creator

• Lee, Eunjee

Advisor dc:contributor.advisor

• Ronald Prinn.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/69469

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/69469