Ice storms generate spatially heterogeneous damage patterns at the watershed scale in forested landscapes

Abstract

Abstract. The effects of large-scale disturbances play a pivotal role in shaping ecosystem structure and function. Interactions between disturbances and a multitude of biophysical factors at different scales generate spatially heterogeneous patterns of damage on vegetated landscapes. However, research on largescale disturbances is often conducted at one spatial extent because of the challenges associated with quantifying patterns of damage in vegetation across multiple spatial extents. Consequently, the literature has identified many different and often conflicting biophysical controls of vegetation damage, which is likely a consequence of the historical and spatial contingency of particular geographic locations. We investigated the influence of biophysical factors and spatial extent of ice storm damage patterns across the entire Ouachita National Forest and in 65 individual watersheds. This allowed for an assessment of how spatial extent and contingency might influence statistical results and therefore any conclusions drawn from these analyses. Two pre-and post-storm Landsat 7 ETMþ scenes (October 6, 1999 and September 25, 2001) were acquired to map ice storm damage based on the normalized difference vegetation index (NDVI) change. Field sites verified the relationship between NDVI and actual forest damage from the storms. We derived topographic variables from a digital elevation model (DEM) and biological variables from GAPgenerated data. The relationship between ice storm damage patterns and biophysical factors across the entire national forest landscape was weak. However, the relationship between damage severity, topography, and forest type increased significantly at the watershed scale, though the specific variable displaying the strongest influence varied by individual watershed. This research demonstrates that complex topography and biological factors interact with the meteorological characteristics of ice storms to generate spatially heterogeneous damage patterns in forests at the watershed scale. It is likely that the damage patterns corresponding to a particular watershed will be repeated during future disturbances.

Quantifying the compound hazard of freezing rain and wind gusts across CONUS

“…The 6-level Sperry-Piltz Ice Accumulation Index © (SPIA) was developed by Sidney Sperry and Steven Piltz (https://spia-index.com/index.php) to quantify damage associated with FZG [22] based on radial equivalent ice accumulation (R eq ) and wind speed (figure 1(b)). Icing events from FZ tend to be concentrated in time and are spatially heterogeneous [23]. A FZ climatology for the contiguous USA (CONUS) derived from the Integrated Surface Database (ISD) (1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994) found frequencies of <0.1 events per year over the Southwest to >8 in the Midwest and Northeast [24] (regional definitions per figure 1(d)).…”

Evaluation of Forest Damaged Area and Severity Caused by Ice-snow Frozen Disasters over Southern China with Remote Sensing

“…Although field surveys can provide comprehensive and detailed information of the ice-storm disaster to forest vegetation (Broxton et al, 2015;Busseau et al, 2017), it usually costs lots of manpower, material and financial resources and much time (Olthof et al, 2004). In contrast, remote sensing can provide explicit vegetation changes information before and after ice and snow storm disasters in large-scale region (Millward and Kraft, 2004;Isaacs et al, 2014). Due to the lack of multiple period's images near the ice-snow disaster, some high resolution data, such as Landsat, were restricted for detecting the forest damages accurately and timely.…”