More than Drought: Precipitation Variance, Excessive Wetness, Pathogens and the Future of the Western Edge of the Eastern Deciduous Forest

Abstract

For many regions of the Earth, anthropogenic climate change is expected to result in increasingly divergent climate extremes. However, little is known about how increasing climate variance may affect ecosystem productivity. Forest ecosystems may be particularly susceptible to this problem considering the complex organizational structure of specialized species niche adaptations. Forest decline is often attributable to multiple stressors including prolonged heat, wildfire and insect outbreaks. These disturbances, often categorized as megadisturbances, can push temperate forests beyond sustainability thresholds. Absent from much of the contemporary forest health literature, however, is the discussion of excessive precipitation that may affect other disturbances synergistically or that might represent a principal stressor. Here, specific points of evidence are provided including historic climatology, variance predictions from global change modeling, Midwestern paleo climate data, local climate influences on net ecosystem exchange and productivity, and pathogen influences on oak mortality. Data sources reveal potential trends, deserving further investigation, indicating that the western edge of the Eastern Deciduous forest may be impacted by ongoing increased precipitation, precipitation variance and excessive wetness. Data presented, in conjunction with recent regional forest health concerns, suggest that climate variance including drought and excessive wetness should be equally considered for forest ecosystem resilience against increasingly dynamic climate. This communication serves as an alert to the need for studies on potential impacts of increasing climate variance and excessive wetness in forest ecosystem health and productivity in the Midwest US and similar forest ecosystems globally.

Reconciling inconsistencies in precipitation–productivity relationships: implications for climate change

“…(2) the level of PPT that causes ANPP to decrease as a result of hydric limitations (direct or indirect effects of anoxia and pathogens: Schuur, 2003;Knapp et al, 2008;Hubbart et al, 2016); (3) the inflection point at which decreases in PPT lead to reductions in ANPP that deviate substantially from those expected from nominal variation in PPT; and, finally, (4) the reduction in PPT that leads to significant mortality, potential ecosystem collapse and possible ecosystem state change.…”

“…This intensification may be manifest in many ways, including increased interannual PPT variability, more frequent extreme PPT years (wet and dry) and alterations in annual PPT amount, with some regions expected to become wetter and others drier (Lau et al, 2013;Polade et al, 2014). Recent climatological trends have supported these predictions (Huntington, 2006;Fischer & Knutti, 2014;Hubbart et al, 2016). Thus, forecasting how future ecosystem structure and function will respond to changing PPT regimes requires a robust understanding of the relationship between PPT and ANPP.…”

Climatic Trends of West Virginia: A Representative Appalachian Microcosm

“…The combination of an increasingly wet and temperate climate should help to secure WV's water resource quantity, but water quality problems exist in WV including (but not limited to) LULC change [45], acid mine drainage [46], and pathogenic water contamination [47]. Additionally, WV's increasingly temperate climate combined with decreasing temperature variance [9] may prolong episodes of excessive soil wetness and humid conditions that increases the vulnerability of terrestrial ecosystems to pathogens and fungal-like oomycetes such as Phytophtora and Pythium [48]. Similarly, increasing precipitation variance [9] indicates wet years are becoming more extreme, which may exacerbate vulnerabilities associated with pests and pathogens [49][50][51][52][53].…”

A method for mapping Australian woody vegetation cover by linking continental-scale field data and long-term Landsat time series

“…Humans convert forests to agricultural and other land uses (DeFries et al 2012). And our warmer and more variable climate creates conditions suitable for fire, pests, disease, and extremes of temperature and precipitation to severely damage forests (Trumbore, Brando, and Hartmann 2015;Hubbart, Guyette, and Muzika 2016). The processes driving shrub encroachment into grasslands and woodlands are complex and vary globally.…”