Age Structure of Trees in. Du Page County Forest Preserves. Scott N. Kobal. Presentation to Commission February 21, 2017

Transcription

1 Age Structure of Trees in Scott N. Kobal Du Page County Forest Preserves Presentation to Commission February 21, 2017

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3 Pre-settlement Vegetation of DuPage County

4 Initial Plot Methodology 35 one-acre plots were established within typical wooded communities in 14 preserves between 1979 and 1986 Live trees >3.5 inches in diameter (DBH) were sampled in 12 different oak dominated plots to establish age structure between 2006 and 2016

5 Methodology

6 Methodology

7 70 Number of Trees Cored by Year Class - White Oaks Quercus alba

8 70 Number of Trees Cored by Year Class - Wild Black Cherries Prunus serotina

9 70 Number of Trees Cored by Year Class - Oaks White Oak Bur Oak Red Oak Black Oak

10 70 White Oak start dates vs. mesic tree species start dates Sugar Maple White Ash Ironwood Wild Black Cherry White Oak Basswood American Elm Slippery Elm

11 30 Number of Trees Cored by Year Class - Walnuts and Hickories Bitternut Hickory Shagbark Hickory Black Walnut

12 30 Number of Trees Cored by Year Class - Belleau Woods - Plot # Bitternut Hickory Shagbark Hickory White Ash Black Walnut Wild Black Cherry White Oak Bur Oak Basswood American Elm Slippery Elm

13 Pre-1900 Tree Establishment 70% 60% 50% 40% 30% 20% 10% 0%

14 Post 1900 Tree Establishment 30% 25% 20% 15% 10% 5% 0%

15 Important Findings Most white oaks have start dates from the 1840 s through the 1860 s this correlates with historical records that indicate that most of the white oaks in the area date back to the time of settlement after the large trees were cut for building materials and plank roads.

16 Important Findings Bur oaks were the oldest trees recorded during the study with the oldest dating back to This species had a more even age distribution than white oak but the majority established between the 1850 s and 1890 s. This is the only tree species that had individuals that could be considered pre-settlement (< 1810) that were found in any of the plots.

17 Important Findings Although a few older mesic tree species individuals established prior to 1900 the majority of these trees established in the plots post Most of the plots saw very little recruitment of any tree species in the late 19 th Century and early 20 th Century presumably corresponding to grazing activity at the time.

18 Conclusions Oak recruitment is currently very low in Du Page County woodlands and most stands are relative even-aged Hickories and walnuts had much higher rates of recruitment in the 20 th Century than oaks Recruitment over the last 100 years has consisted primarily (70%) of shade tolerant species: basswood, sugar maple, wild black cherry, ironwood and American and slippery elms

19 Management Implications Health of our woodlands will depend on innovative and multi-faceted management techniques which will reduce competition and allow new oaks to be recruited

20 The Forest Preserve District should do the following to preserve these valuable ecosystems Identify important oak ecosystems in the Forest Preserve Districts holdings and develop specific management plans for each site Increase the frequency of prescribed fire in our important oak ecosystems Continue and expand the removal of invasive species in our oak ecosystems Continue and expand the thinning of overabundant native woody species in our oak ecosystems Augment oaks where appropriate and expand the size of existing stands where suitable soils exist Continue the deer management program in key oak ecosystem areas Continue to monitor oak ecosystems so as to be able to provide the best management practices at the most efficient cost

21 Acknowledgments Marlin Bowles Dr. Jon Mendelson Former FPDDC Employees Wayne Lampa John Oldenburg FPDDC Volunteers Carol Kobal Frank Keller Current FPDDC Employees Rachel Reklau Erik Neidy Jessi DeMartini Tom Velat Dan Grigas Andres Ortega FPDDC Interns Maggie Silvinski Barbara Sherwood FPPDC Physical Plant - Carpenters