Predictors of Ips confusus Outbreaks During a Record Drought in Southwestern USA: Implications for Monitoring and Management

Abstract

In many ecosystems the effects of disturbance can be cryptic and disturbance may vary in subtle spatiotemporal ways. For instance, we know that bark beetle outbreaks are more frequent in temperate forests during droughts; however, we have little idea about why they occur in some locations and not others. Understanding biotic and abiotic factors promoting bark beetle outbreaks can be critical to predicting and responding to pest outbreaks. Here we address the environmental factors which are associated with Ips confusus outbreaks during the 2002 widespread drought within the distribution range of pinyon pine woodlands in Arizona. We used univariate statistics to test if whether tree characteristics, other herbivores, stand properties, soil type, wind, and topography were associated with I. confusus outbreak, and logistic regression to create a predictive model for the outbreaks. We found that I. confusus attacks occur in low elevation stands on steeper slopes, where favorable winds for I. confusus dispersion occur. I. confusus select larger trees, in high density stands with understory shrubs that exhibit phenotypic traits characteristic of resistance to stem-boring moths. The model was highly accurate, and explained 95% of the variability in occurrence (98% of the absences and 95% of the presences). Accurate prediction of the impacts of disturbance allow us to anticipate, minimize or mitigate for and eventually counteract its effects, especially those affecting diversity and ecosystem function. Identification of outbreak risk areas can guide regional and national management towards the reduction of infestation risk and enhancing conservation of pinyon-juniper woodlands.

Establishment and growth of piñon pine regeneration vary by nurse type along a soil substrate age gradient in northern Arizona

“…html). The region experienced a prolonged drought from 1996 to 2003 that resulted in substantial piñon pine mortality in 1996 and 2002 (Mueller et al, 2005;Gitlin et al, 2006;Koepke et al, 2010;Santos and Whitham, 2010;Looney et al, 2012). Annual precipitation from 2000 to 2008, the time period in which stem elongation was measured for piñon pines, ranged from 214.6 mm to 586.2 mm.…”

“…Recent climate changeinduced, intense drought has been associated with large die-offs of piñon pine in Arizona (Breshears et al, 2005;Mueller et al, 2005;Gitlin et al, 2006;Koepke et al, 2010;Santos and Whitham, 2010;Looney et al, 2012) as well as throughout much of the southwestern U.S. (Shaw et al, 2005;Floyd et al, 2009;Redmond and Barger, 2013). Climatic predictions for the region suggest continued increases in temperature and frequency of drought (Seager et al, 2007;IPCC, 2013).…”

Managing drought-induced mortality in Pinus radiata plantations under climate change conditions: A local approach using digital camera data

“…Traditionally, forest mortality events have been recorded either through plot-based inventories or mapped at the stand-level from ground surveys using GPS or aerial sketch mapping techniques (e.g. Negrón et al, 2008;Hicke and Logan, 2009;Santos and Whitham, 2010). Mapping plantation canopy damage process is now becoming automated through the application of high spatial resolution (pixel size 61.0 m) multi-spectral imagery and ranging (LiDAR) data (Coggins et al, 2008;Bater et al, 2010;Dennison et al, 2010;Meddens et al, 2011).…”

Potential aboveground biomass in drought‐prone forest used for rangeland pastoralism

“…Deep-soil characteristics that are difficult to investigate may play a role (Fensham and Fairfax 2007), and biological interactions (other than competition) are poorly understood in Australia and require further investigation. In North America bark-feeding beetles are implicated (Santos and Whitham 2010), although death can certainly occur due to drought alone (Floyd et al 2009). There is no published information implicating a biological agent in the drought-induced tree mortality of mulga, but based on anecdotal reports, grasshoppers may be a candidate, having been reported to have stripped trees which, in a drought-stressed condition, are unable to recover (R. Kerr, personal communication).…”