Measurement report: Introduction to the HyICE-2018 campaign for measurements of ice nucleating particles in the Hyytiälä boreal forest

The formation of ice particles in Earth’s atmosphere strongly influences the dynamics and optical properties of clouds and their impacts on the climate system. Ice formation in clouds is often triggered heterogeneously by ice nucleating particles (INPs) that represent a very low number of particles in the atmosphere. To date, many sources of INPs, such as mineral and soil dust, have been investigated and identified in the lower latitudes. Although less is known about the sources of ice nucleation at higher latitudes, efforts have been made to identify the sources of INPs in the Arctic and boreal environments. In this study, we investigate the INP emission potential from high latitude boreal forests. We introduce the HyICE-2018 measurement campaign conducted in the boreal forest of Hyytiälä, Finland between February and June 2018. The campaign utilized the infrastructure of the SMEAR II research station with additional instrumentation for measuring INPs to quantify the concentrations and sources of INPs in the boreal environment. In this contribution, we describe the measurement infrastructure and operating procedures during HyICE-2018 and we report results from specific time periods where INP instruments were run in parallel for inter-comparison purposes. Our results show that the suite of instruments deployed during HyICE-2018 reports consistent results and therefore lays the foundation for forthcoming results to be considered holistically. In addition, we compare the INP concentration we measured to INP parameterizations, and we show a very good agreement with the Tobo et al. (2013) parameterization developed from measurements conducted in a ponderosa pine forest ecosystem in Colorado, USA.

Southwestern ponderosa pine forest patterns following wildland fires managed for resource benefit differ from reference landscapes

Context. Managers aiming to utilize wildland fire to restore southwestern ponderosa pine landscapes require better understanding of forest cover patterns produced at multiple scales. Restoration effectiveness of wildland fires managed for resource benefit can be evaluated against natural ranges of variation.Objectives. We describe landscape patterns within reference landscapes, including restored and functioning ponderosa pine forests of northern Arizona, and compare them to wildland fires managed for resource benefit. We make comparisons along a gradient of extents and assess the effects of scale on landscape differences.Methods. Using Sentinel-2 imagery, we classified ponderosa pine forest cover and calculated landscape metrics across a gradient of landscape extent within reference and managed landscapes. We used non-parametric tests to assess differences. We used random forest models to assess and explore which landscape metrics were most importance in differentiating landscape patterns.Results. Managed wildfire landscapes were significantly different from reference landscapes for most metrics and extents (15 ha to 840 ha). Landscape type (managed vs. reference) became increasingly differentiable with scale, with area and aggregation metrics being the most informative. Classification models increased in accuracy despite fewer observations with increasing scale.Conclusions. Wildland fires managed for resource benefit in ponderosa pine forests of northern Arizona are not producing landscape patterns consistent with reference landscapes likely due to predominance of low-severity burning and minimal resulting changes in overstory structure. Differences become more pronounced with increasing landscape size and suggest small-scale heterogeneity and mid - and large-scale homogeneity within each landscape type.

Responses of Ground-Dwelling Spider (Arachnida: Araneae) Communities to Wildfire in Three Habitats in Northern New Mexico, USA, with Notes on Mites and Harvestmen (Arachnida: Acari, Opiliones)

Catastrophic wildfire is increasingly common in forests of the western United States because climate change is increasing ambient temperatures and periods of drought. In 2011, the Las Conchas wildfire burned in the Santa Fe National Forest of New Mexico, including portions of ponderosa pine and mixed-conifer forests, and grasslands in the Valles Caldera National Preserve, a large, high-elevation volcanic caldera. Following the fire, Caldera staff began monitoring abiotic, plant, and animal responses. In this study, ground-dwelling arachnids were collected in pitfall traps in burned and unburned habitats from 2011–2015. Permutational multivariate analysis of variance (PERMANOVA) mostly at the genus level with some higher taxon levels showed significant fire, year, and interaction effects. Abundance was at or near unburned levels by 2014, but species composition changed in burned areas. Pardosa and Haplodrassus were dominant genera across habitats. Linyphiids were strong indicators of unburned sites. Harvestmen were among the dominant species in the forest habitats, and erythraeid mites were abundant in the burned ponderosa pine forest and the grassland. Years were not significantly autocorrelated, unsurprising given the interannual variation in precipitation in this generally arid region. Although fire is a common feature of these habitats, future fires may be outside of historical patterns, preventing spider communities from re-establishing fully.