Forest Influences on Climate and Water Resources at the Landscape to Regional Scale - Landscape Ecology for Sustainable Environment and Culture - page 316

15.5.2 Improving Earth System Modeling Capacity: Bridging
Landscape Processes and Regional Climate
and Hydrology
Climate is the ultimate driving force for landscape-scale hydrologic processes
which are naturally linked to local climate. Traditional watershed or landscape
hydrological studies largely assume climate as a stationary external force, and
hydrologic processes have no influences on local climate. For example, we know
that reforestation will increase ET at the watershed scale, but we rarely tract how
far and where the water vapor will travel across the physical watershed boundaries.
Scaling empirical observations at the landscape scale to regional scale is still a
difficult task and remains to be an active research area in landscape ecology and
regional and global hydrology.
Simulating the true interactions and feedbacks between land surface processes
such as forest vegetation functions and climate systems requires the tight coupling of
regional climate models and landscape vegetation dynamics, and global circulation
climate models or regional climate models (Phipps et al. 2011 ). Existing integrated
dynamic vegetation models (DGVMs) have the capacity to simulate natural forest
vegetation dynamics and the influences of external disturbances such as climate
variability (e.g., drought and flood) and physical and chemical climate effects (e.g.,
greenhouse gases), species invasion, wildfire, insect outbreak on ecological pro-
cesses (i.e., water and carbon cycles). DGVMs simulate daily or monthly carbon,
water and nitrogen cycles driven by the changes in atmospheric chemistry including
ozone, nitrogen deposition, CO 2 concentration, climate, land-use and land-cover
types and disturbances. DGVMs usually include four core components of bio-
physics, plant physiology, soil biogeochemistry, and dynamic vegetation and land-
use. Examples of DGVMs include HYBRIDS (Friend et al. 1997 ), MC1 (Bachelet
et al. 2001 ), the Lund-Potsdam-Jena (LPJ) (Sitch et al. 2003 ), CLM (Levis et al.
2004 ), IBIS (Foley et al. 2005 ), and the DELM (Tian et al. 2009 ).
Efforts have been made to couple DGVMs into Global Circulation Models
(GCMs) and Regional Climate Model (RCMs). For example, CLM is fully cou-
pled with the National Center for Atmosphere Research's Community Earth
System Model (CESM) and WRF (Jin et al. 2010 ), respectively. The coupled
models are able to simulate the impacts on and feedbacks to climate from dynamic
changes in forests. They will be especially useful for understanding the roles of
afforestation in mitigating the impacts of climate change discussed above. For
further assessing the mitigation roles and making management plans, compre-
hensive modeling systems such as the integrated Regional Earth System Model
(iRESM) ( http://www.pnl.gov/atmospheric/iresm/ ) are needed. iRESM is a mod-
eling framework developed in the Pacific Northwest National Laboratory (PNNL)
to address regional human-environmental system interactions in response to cli-
mate change and the uncertainties therein. The framework consists of a suite of
integrated models representing regional climate change, regional climate policy,
and the regional economy.