Pine Expansion of Arid Land: Fire Effects on Safe Site Abundance, Subcontract

Affiliation(s)PIProject periodFunded by
DEES Cablk, Mary E 12/01/2008 - 11/30/2010 International Arid Lands Consortium

Project Description

Conifer forest expansion in arid lands is a phenomenon which may lead to substantial changes in the invaded ecosystem particularly in terms of wildfire risk. Although pine expansion occurs globally, research focus has been primarily at regional scales, with variability and uncertainty surrounding the underlying causes. The goal of this study is to develop a more mechanistic understanding of how fire and fire exclusion relate to pine expansion processes, through comparative studies of different regions where pine expansion is occurring, specifically western North America (the Great Basin Desert, Nevada, USA) and the Eastern Mediterranean region of Asia (Israel). Comparative studies of pine expansion may provide better understanding of the mechanisms underlying pine invasion processes in the context of historical and contemporary land use practices, climate change, and fire regime. Causes of pine expansion in both the western United States and Israel are similarly multifaceted and potentially involve climate change, historical land use, grazing management practices, and altered fire regimes.

We propose to study the role of fire and post-fire succession in controlling the early establishment phase of pine colonization in dry lands. We will focus on the influences of fire history and consequent landscape pattern and vegetation structure on the spatiotemporal distribution of safe sites for pine establishment in dry lands. Specifically we will:

  1. define general characteristics of safe sites for early establishment of pine,
  2. investigate the role of fire and post-fire succession in determining the availability in time and space of safe sites for early pine establishment and,
  3. study at large scales relationships among fire, post-fire succession, landscape patterns and safe site availability.

The research will be conducted on two different model pine species: Pinus monophylla in Nevada, USA and Pinus halepensis in Israel. Study areas in both countries represent a climatic transitional zone with a precipitation gradient of 250-500 mm/year. Manipulative field experiments involving regeneration trials along systematic gradients will quantify the effects of time-since-fire and drought stress on early establishment of the local pine. Safe site availability will be measured as the proportion of seeds to germinate and establish. Safe sites will be characterized through field measurements of soil and substrate characteristics, vegetation structure, light availability, and proximity to neighboring plants and other features that influence the establishment micro-environment. Statistical relationships derived from experimental and observational studies will be used to geographically model the distribution and abundance of safe sites at approximately 0.1-ha spatial resolution. The distribution of safe site predictors will be modeled as a function of available GIS layers for vegetation structure, soils, geology, climate, topography, and fire history. The resulting GIS model will allow prediction of safe site distribution over large spatial extents, and will be applied and validated in recently burned and unburned study areas.