Warm winter and dry spring spell trouble for Oregon’s tree population

SALEM, Ore. (KTVZ) -- Oregon trees are facing another challenging year as climate change continues to impact the state. This spring's conditions are similar to those in 2015, a period marked by peak high temperatures and drought. These current conditions follow a winter that tied 1934 for the warmest since accurate records began in 1896.

The National Oceanic and Atmospheric Administration reported the record-tying warm winter, signaling continued stress for the region's tree population.

For at least two decades, trees in Oregon have experienced chronic stress from hot droughts. The compounding effect of frequent or prolonged warm and dry conditions has taken a significant toll on many trees. These conditions include higher than average temperatures, inconsistent precipitation patterns where more rain falls than snow and earlier snow melt.

Christine Buhl, a Forest Entomologist with the Oregon Department of Forestry, explained that a warm or dry spring is particularly detrimental for trees. "A warm or dry spring is particularly harmful for trees as this is their most active growing period. This stress reduces growth, weakens defenses against opportunistic insects and diseases and can outright kill tissues or whole trees," Buhl said.

Buhl also noted that warmer winters create more favorable conditions for tree pests. "Warm winters reduce pest deaths from cold, increasing their growth or number of pests. It also extends the range of less cold-tolerant pests and lengthens their feeding periods," she stated.

To help landowners manage their trees amid these conditions, Buhl offered several recommendations. She advises planting species and seedlots only within their current and climate-projected range. When planting seedlings, it is best to avoid dry seasons and keep roots moist and out of direct sun to ensure proper establishment.

Landowners should also work to reduce competition for moisture by controlling weeds and decreasing stand density to match the carrying capacity for the specific tree species, site quality and climate. If currently adapted species or seedlots are struggling, Buhl suggests shifting toward a nearby, more drought-tolerant seedlot, or in extreme cases, a more drought-tolerant species.

Other practices include using native understory vegetation and mulch to help retain soil moisture. Landowners should avoid root compaction caused by heavy equipment when the soil is wet. Additionally, fertilizing should be avoided if a site is already drought-stressed, as fertilizer increases biomass and thus water requirements.