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Accueil du site → Projets de développement → Projets de recherche pour le Développement → 2009 → LONG-TERM RESPONSES OF NORTHERN ARIZONA GRASSES TO CLIMATE AND LAND-USE CHANGE

United States Department of Agriculture (USDA) 2009


Grasses Climate Change

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)


Identification : ARZZ-MOORE-MS105

Pays : Etats Unis

Durée : Jul 1, 2009 à Jun 30, 2013

Mots clés : herbacious vegetation ; wildland ecosystem


Ponderosa pine-bunchgrass ecosystems of the Southwest have undergone dramatic changes in structure and composition since Anglo-American and Hispanic settlement of the region in the late 1800s. Overgrazing, high-grade logging, fire exclusion, and climate change have been identified as factors contributing to dramatic increases in tree density across the Southwest (Fig. 1 ; Covington & Moore 1994a, Moore et al. 2004). The impact of these factors on the herbaceous (non-woody) plants in forest openings or underneath the forest canopy has received surprisingly little attention (Moore et al. 2006, Bakker & Moore 2007). Although the understory herbaceous vegetation often goes unnoticed, it represents over 90% of the plant biodiversity in the ponderosa pine vegetation type of the Southwest (McDougal 1973), which in-turn also supports most animal diversity. In addition, the understory herbaceous vegetation may have important ecosystem-level effects by, for example, cycling nitrogen more efficiently than pine trees (Kaye & Hart 1998). It is critical that we understand and document the dynamics in vegetation structure and function over time if we are to understand population trends and the potential fates of indigenous understory species. Long-term, permanent plots provide an opportunity to detect and quantify these changes. Originally designed by Clements (1905), and widely used in the western U.S. rangelands in the 1900s, chart quadrats are fine-grained permanent plots and maps showing the location of 2 individual plants. In the past, chart quadrats were most commonly used to analyze plant demography (Albertson & Tomanek 1965, Lauenroth & Adler 2008). Currently, there is a renewed interest in relocating and remapping permanent chart quadrats because of their tremendous importance for ecological theory (Adler et al. 2006), vegetation response to climate change (Adler et al. 2006, Yao et al. 2006), soil processes (Gill 2007), and questions regarding biodiversity (Adler & Lauenroth 2003, White et al. 2006, Alder & Levine 2007). Life history characteristics are totally lacking for all but a few herbaceous species in the Southwest and these studies focused on the desert grasslands of New Mexico (Nelson 1934, Paulsen & Ares 1962, Wright & Van Dyne 1976, 1981 ; Gibbens & Beck 1987, 1988, Qinfeng et al. 2002), desert grasslands of southern Arizona (Canfield 1957), and the Sonoran Desert (Shreve 1917, 1929 ; Shreve & Hinckley 1937, Goldberg & Turner 1986). Life history studies of herbaceous plants in Arizona pine forests are practically nonexistent.

We propose to build upon the large amount of vegetation and soils data already collected on these long-term permanent plots by using a combination of "seed" funding from the School’s MRP and a proposal to be submitted to the NSF LTREB program (long-term research in environmental biology) in July 2009 (see VII. Matching Funds ; Exhibit II - Proposals Funded). Specifically, we propose to : 1) examine the temporal variation in basal cover of nine important perennial graminoids (8 grasses and 1 upland sedge) in northern Arizona, during the time periods from 1912-1950 and 2002-2007 ; and 2) determine the relationship among graminoid basal cover and factors such as climate, grazing, and tree densities over the same time periods. Determining the relative importance of factors such as climate and past land-use to long term trends in grass cover can provide insights into processes that drove these vegetation patterns in the past and can be used to improve our ability to forecast future vegetation change (Adler et al. 2006, Yao et al. 2006). In addition, we can explore theoretical ideas of species coexistence and climatic variability (Adler et al. 2006, Adler et al. 2007).

Présentation : USDA

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