Bioturbation by gophers and marmots and its effects on conifer germination

Abstract

Although climate has been shown to have a considerable influence on alpine forest dynamics, many fine‐scale processes contribute to observable forest patterns. Disturbances created by burrowing mammals may provide conifer seedlings with refuge in previously inhospitable environments and may result in conifer invasion that is not directly associated with climate change. In Olympic National Park, Washington, USA, Olympic marmot (Marmota olympus) populations have declined. Abandoned marmot burrows, which may provide ideal sites for conifer establishment, now dot the alpine landscape. Similarly, in Glacier National Park, Montana, USA, pocket gophers (Thomomys talpoides) have disturbed large areas of alpine meadows at treeline. Field and laboratory analysis of gopher eskers and spoil mounds of abandoned marmot burrows illustrated that such sites are less compacted than soils in adjacent, undisturbed locations. Additionally, disturbed soils contained higher amounts of phosphorus and lower amounts of potassium and organic matter. Soils disturbed by gophers were cooler at the surface and warmer at depth than undisturbed soils, whereas marmot‐disturbed soils were warmer at the surface and cooler at depth. Experimental seed germination of subalpine fir (Abies lasiocarpa) was higher on mammal‐disturbed soils, and this was statistically significant for marmot‐disturbed soils. These findings suggest that fossorial mammal disturbances have the potential to affect conifer germination and establishment. Furthermore, this research initiates the dialogue for future research on the distinct morphological and behavioral influences of different fossorial mammals as zoogeomorphic agents and ecosystem engineers. Copyright © 2016 John Wiley & Sons, Ltd.

Henry Gannett

“…Most of Gannett’s timberline observations occurred at the coarse, mountain or range scale. Although he recognized the importance of geology and geomorphology, it is unlikely he observed many of the fine-scale geomorphic processes that affect the timberline (for examples, see Malanson et al, 2002; Resler, 2006; Resler et al, 2005; Whitesides and Butler, 2016). Butler et al (2007) suggested that some timberlines may be attributed to climatic factors, but large- and small-scale geomorphic processes and geological history are often the primary control of timberline in the American West, although additional research is desperately needed (Whitesides and Butler, 2010).…”

Pocket gopher (Thomomys talpoides) soil disturbance peaks at mid-elevation and is associated with air temperature, forb cover, and plant diversity

“…This large soil disturbance creates multiple microenvironments (Huntly and Inouye 1988). For example, pocket gopher disturbance can raise median subsurface temperatures while decreasing median surface temperatures when compared to undisturbed soils (Whitesides and Butler 2016). Furthermore, burrowing and plant foraging by pocket gophers can influence succession and plant species composition (Reichman and Seabloom 2002;Sherrod, Seastedt, and Walker 2005).…”

Ecosystem engineering by hummock‐building earthworms in seasonal wetlands of eastern South Africa: Insights into the mechanics of biomorphodynamic feedbacks in wetland ecosystems

“…Although these animals conduct their activities at the geomorphological micro-scale, the cumulative effect of colonies or populations can create distinctive landscapes (Zaitlin and Hayashi, 2012;Coombes and Viles, 2015). The micro-landforms produced by burrowing and soil foraging activities have a patchy distribution that creates gradients of local environmental change (Zaitlin and Hayashi, 2012), can affect the flow paths of moisture and other resources (Eldridge et al, 2010), and can create refugia for plant germination (Whitesides and Butler, 2016). Through burial of vegetation by burrow spoil or casting material (Zaitlin and Hayashi, 2012), provision of foraging pits that provide conditions favouring enhanced litter decomposition (Travers and Eldridge, 2016), or selective transport and concentration of organic materials, burrowing and soil foraging animals can profoundly influence the structure and biogeochemistry of soil environments (Coggan et al, 2018), and thereby increase landscape-scale heterogeneity and biodiversity (Zaitlin and Hayashi, 2012).…”