Stand Composition, Structure, and Dynamics in a Mature Oakhickory Forest of Northeastern Kansas

Undergraduate #77
Discipline: Biological Sciences
Subcategory: Ecology

Hanna Dörnhofer - Reed College
Co-Author(s): Bryan Foster and Jeremy Forsythe, University of Kansas, Lawrence, KS

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Forest ecosystems worldwide face tremendous pressure from human activities. Empirical studies documenting long-term vegetation dynamics in response to human disturbance are rare. Understanding how forests respond to environmental changes is important to conserve biodiversity and protect ecosystem services humans rely upon. We investigated forest community dynamics over 34 years in Baldwin Woods Area (BWA), an oakhickory forest in the University of Kansas Field Station that underwent selective logging in the early 1900s. Forest trees were surveyed four times from 1981-2015 in four 50 x 75 m permanent plots. In each plot, tree diameter (DBH) was measured at breast height (1.4 m) for all trees ≥7.5 cm DBH. Tree species were identified and status (alive, unhealthy, dead) was determined. We questioned whether forest composition has changed by calculating total stem number and tree basal area. We compared DBH frequency distributions over time to determine whether changes suggest ecological succession in response to logging. Total stem number showed no trend across sites since 1981, but total basal area increased steadily, suggesting BWA is recovering biomass lost due to logging. Tree size distributions for all species combined varied over time, suggesting fluctuations in recruitment patterns and stochastic dynamics. However, size distributions depicting only the dominant canopy oaks (Quercus spp.) revealed low recruitment into the smallest size class, indicating this genus may not be replacing itself. A forest in succession has a greater capacity for carbon sequestration than a mature and stable forest. The unstable, succession-like dynamics observed here suggest that BWA is affecting the local carbon cycle as a carbon sink. This demonstrates the importance of considering how forest dynamics affect regional biogeochemical processes in future models of climate change.

Funder Acknowledgement(s): I thank Sheena Parsons, Vaughn Salisbury, and Galen Pittman for completing earlier years of fieldwork. Funding was provided by NSF Grant DBI-1262795 to the KU EEB department for Hanna Dörnhofer.

Faculty Advisor: Bryan Foster,