Geophysical features influence the climate change sensitivity of northern Wisconsin pine and oak forests

Abstract

Landscape-scale vulnerability assessment from multiple sources, including paleoecological site histories, can inform climate change adaptation. We used an array of lake sediment pollen and charcoal records to determine how soils and landscape factors influenced the variability of forest composition change over the past 2000 years. The forests in this study are located in northwestern Wisconsin on a sandy glacial outwash plain. Soils and local climate vary across the study area. We used the Natural Resource Conservation Service's Soil Survey Geographic soil database and published fire histories to characterize differences in soils and fire history around each lake site. Individual site histories differed in two metrics of past vegetation dynamics: the extent to which white pine (Pinus strobus) increased during the Little Ice Age (LIA) climate period and the volatility in the rate of change between samples at 50-120 yr intervals. Greater increases of white pine during the LIA occurred on sites with less sandy soils (R² = 0.45, P < 0.0163) and on sites with relatively warmer and drier local climate (R² = 0.55, P < 0.0056). Volatility in the rate of change between samples was positively associated with LIA fire frequency (R² = 0.41, P < 0.0256). Over multi-decadal to centennial timescales, forest compositional change and rate-of-change volatility were associated with higher fire frequency. Over longer (multi-centennial) time frames, forest composition change, especially increased white pine, shifted most in sites with more soil moisture. Our results show that responsiveness of forest composition to climate change was influenced by soils, local climate, and fire. The anticipated climatic changes in the next century will not produce the same community dynamics on the same soil types as in the past, but understanding past dynamics and relationships can help us assess how novel factors and combinations of factors in the future may influence various site types. Our results support climate change adaptation efforts to monitor and conserve the landscape's full range of geophysical features.

Taking the Long View: Integrating Recorded, Archeological, Paleoecological, and Evolutionary Data into Ecological Restoration

“…Data from multiple time points can be used to show the range of conditions over long time periods and provide a historical context for more recent conditions. For example, pollen analysis of sediments from 13 lakes on a 450-km 2 sand plain in northwestern Wisconsin was used to place the vegetation patterns recorded by the PLS during the 1850s and 1860s (Radeloff et al 1999) into a historical context (Hotchkiss et al 2007;Tweiten et al 2015). Maps showing current and reconstructed vegetation communities at 100-yr intervals over the past 1200 yr ( fig.…”

Quantifying trends and uncertainty in prehistoric forest composition in the upper Midwestern United States

“…Although we do not formally assess here the role of potential environmental drivers on these vegetation changes, many of the above changes are consistent with regional trends toward cooler and moister conditions over the last 2,000 yr (Marlon et al 2017). There is also strong evidence that extensive droughts (Booth et al 2012b) and changing fire regimes (Umbanhowar 2004, Tweiten et al 2015 have affected UMW vegetation. A next key step is to combine these vegetation reconstructions with climate reconstructions for the last several millennia (Ahmed et al 2013) to understand better the combination of external forcings, internal feedbacks, and interaction of slow and fast processes (Svenning and Sandel 2013) that produced the observed mixture of forest change and stability.…”

“…Key ecological changes include the ongoing westward range expansion of several tree taxa in the Great Lakes region (Davis et al 1986, Woods and Davis 1989, Booth et al 2012a, Jackson et al 2014, Wang et al 2016, population expansion for some species such as hemlock (Davis et al 1998) and white pine (Tweiten et al 2015), the establishment of mesic hardwood forests in the Big Woods of south-central Minnesota (Umbanhowar et al 2006, Hupy 2012, and southward shifts in the ecotone between northern mixed forests and temperate broadleaved forests (Hupy 2012). Key ecological changes include the ongoing westward range expansion of several tree taxa in the Great Lakes region (Davis et al 1986, Woods and Davis 1989, Booth et al 2012a, Jackson et al 2014, Wang et al 2016, population expansion for some species such as hemlock (Davis et al 1998) and white pine (Tweiten et al 2015), the establishment of mesic hardwood forests in the Big Woods of south-central Minnesota (Umbanhowar et al 2006, Hupy 2012, and southward shifts in the ecotone between northern mixed forests and temperate broadleaved forests (Hupy 2012).…”

“…The upper Midwestern United States (UMW), ranging from Minnesota to Upper Michigan, has been the focus of decades of paleoecological study and has one of the densest networks of fossil pollen data worldwide. Key ecological changes include the ongoing westward range expansion of several tree taxa in the Great Lakes region (Davis et al 1986, Woods and Davis 1989, Booth et al 2012a, Jackson et al 2014, Wang et al 2016, population expansion for some species such as hemlock (Davis et al 1998) and white pine (Tweiten et al 2015), the establishment of mesic hardwood forests in the Big Woods of south-central Minnesota (Umbanhowar et al 2006, Hupy 2012, and southward shifts in the ecotone between northern mixed forests and temperate broadleaved forests (Hupy 2012). There is also evidence for ecologically significant climatic changes in the UMW during the past 3,000 yr , Booth and Jackson 2003, Tweiten et al 2009) and shifts in fire regimes (Umbanhowar 2004).…”

Fuels, vegetation, and prescribed fire dynamics influence ash production and characteristics in a diverse landscape under active pine barrens restoration

“…Soils are classified as slightly to strongly acidic (pH = 5.1 to 6.5) spodosols with a depth of 15 to 25 cm to the spodic horizon under NRCS Soil Taxonomy (Soil Survey Staff 1999). Soils consist of well-drained sands and sandy loams of glacial outwash origin, with a low water holding capacity and low cation exchange capacity (Tweiten et al 2015). This landscape consists of a mosaic of hardwood forest, pine woodland, shrubland, and grasslands (Curtis 1959).…”