. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. â Other Hardwoods 1,815 H Maple 1,766 El Hickory 1,559 0 Ash 783 â¡ Cottonwood 710 â Sycamore 605 & Elm 483 â¡ Walnut 368 â¡ Softwoods 338 â¡ Oak 8,833 Figure 15. Volume (in million board feet) of various types of trees in Illinois commercial forestland, 1985. Total volume of sawtimber was billion board feet. majority of insect and pathogen mortality can be traced to two sources: (1) introd
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. â Other Hardwoods 1,815 H Maple 1,766 El Hickory 1,559 0 Ash 783 â¡ Cottonwood 710 â Sycamore 605 & Elm 483 â¡ Walnut 368 â¡ Softwoods 338 â¡ Oak 8,833 Figure 15. Volume (in million board feet) of various types of trees in Illinois commercial forestland, 1985. Total volume of sawtimber was billion board feet. majority of insect and pathogen mortality can be traced to two sources: (1) introduced pests spreading through the region (such as Dutch elm disease) or (2) decreased resistance to disease and herbivores as a result of environmental stress (such as the red spruce decline in the northeastern United States or the general forest decline in northern Europe). Examining mortality patterns by species shows that elm leads all species in mortality rates (Table 1). The majority of this mortality is the result of continued spread of Dutch elm disease in Illinois. Thus, it seems likely that the observed increase in mortality rate from 1962 to 1985 may not be symptomatic of general forest decline (Figure 20) but may indicate a peak in mortality associated with a single disease spreading through the region. There appear to be no major differences in mortality rates of trees by ownership category (Table 2). Tree Health An investigation of tree health in Illinois forests was conducted during the summer of 1992 (Iverson and Schwartz, unpublished data). For this study, the investigators followed the USDA Forest Service Forest Health Monitoring (FHM) protocol (Conkling and Byers 1992). The FHM protocol is designed to establish long-term monitoring stations from which periodic samples are collected in order to assess changes in the health and status of forests throughout the United States. The federal project is in a test phase, with current information available for
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