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Standing dead trees, or snags, are important features in natural forests, providing habitat and food for a wide range of fungi, insects, birds, and small mammals. 

The abundance of snags is greatly reduced in forests managed for timber production. Variable retention, an alternative harvest method that retains live trees and snags within harvest areas, has the potential to preserve biodiversity. Researchers examined the relationships between variable retention practices and snag abundance using two decades of data from Douglas-fir dominated forests in the Pacific Northwest. The analysis revealed that harvest strategies that preserve large, undisturbed patches of live trees reduce the loss of the large, tall, and hard snags that contribute disproportionately to biodiversity. These results suggest that variable retention, and particularly preserving large patches of trees in harvest areas, has the potential to preserve the diversity of snag dependent animals.  

Halpern, C.B., Rossman, A.K., and Hagar, J.C., 2022, Level and pattern of overstory retention shape the abundance and long-term dynamics of natural and created snags: Forest Ecology and Management, v. 526, 120575.