Whitebark pine (Pinus albicaulis) has the largest and most northerly distribution of any white pine (Subgenus Strobus) in North America, encompassing 18° latitude and 21° longitude in western mountains. Within this broad range, however, whitebark pine occurs within a narrow elevational zone, including upper subalpine and treeline forests, and functions generally as an important keystone and foundation species. In the Rocky Mountains, whitebark pine facilitates the development of krummholz conifer communities in the alpine-treeline ecotone (ATE), and thus potentially provides capacity for critical ecosystem services such as snow retention and soil stabilization. The invasive, exotic pathogen Cronartium ribicola, which causes white pine blister rust, now occurs nearly rangewide in whitebark pine communities, to their northern limits. Here, we synthesize data from 10 studies to document geographic variation in structure, conifer species, and understory plants in whitebark pine treeline communities, and examine the potential role of these communities in snow retention and regulating downstream flows. Whitebark pine mortality is predicted to alter treeline community composition, structure, and function. Whitebark pine losses in the ATE may also alter response to climate warming. Efforts to restore whitebark pine have thus far been limited to subalpine communities, particularly through planting seedlings with potential blister rust resistance. We discuss whether restoration strategies might be appropriate for treeline communities.

This study aims to understand the effects of wildfires in sagebrush ecosystem on soil properties by examining connections between Soil Water Repellency (SWR), reflectance, and chemistry. Ash and burned soil samples were collected after performing laboratory burns of three common sagebrush plants: sagebrush, rabbitbrush, and bitterbrush. The collected samples were analyzed for their physical properties, including SWR measured by Water Drop Penetration Time (WDPT) and Apparent Contact Angle (ACA), and solar spectral reflectance in the wavelength range of 350 to 2500 nm. Chemical functional groups of the samples were analyzed using Fourier-Transform Infrared (FTIR) spectroscopy. WDPT and ACA values were in the range of 1 to 600 s and ~10° to 88°, respectively, for all three tested fuels. The FTIR analysis showed a decrease (~2 to 4 times) in the ratio of COO⁻/C=C signals for the burned soil samples compared to the unburned soil samples. Overall, increase in temperature and ACA levels for the samples of burned and burned soil from a 2 cm depth led to increased formation of non-polar compounds with C=C functional groups, and decarboxylation.

It is widely known that the increasing presence of invasive annual grasses (IAG), such as Bromus tectorum (cheatgrass), is reshaping landscapes through positive fire-IAG feedback loops across the ~520,000 km2 sagebrush ecosystems of the western US. However, the short-term effects of invasive annuals and fire cycles on net ecosystem CO2 exchange (NEE) and their controlling mechanisms remain poorly quantified, partly due to limited observations able to resolve heterogeneity in plant community composition, fire effects, and soil-vegetation interactions. The objectives of this study were (1) to quantify how fire, plant community species composition, IAG presence, plant canopy greenness (NDVI), and environmental drivers influence late season NEE; and (2) to compare 4x3 meter plot-level NEE values measured with an automated mobile transparent ecosystem gas exchange chamber with simultaneously collected NEE measured across the entire study site using eddy covariance. We measured diel NEE using the automated chamber system on 20 4x3 m experimental plots, which were categorized into pairs according to their plant compositions, namely the varying amounts of B. tectorum, perennial native herbaceous species, and native perennial grasses. In late autumn 2025, one plot within each pair was experimentally burned, allowing for comparison of burned and unburned plots with similar pre-fire vegetation. Repeated pre- and post-burn CO2 flux measurements were collected and analyzed in relation to key NEE drivers, including photosynthetically active radiation (PAR), air temperature, and vegetation composition. Nighttime NEE ranged from 0.62 to 1.48 µmol CO2 m⁻² s⁻¹, consistent with net CO2 release via ecosystem respiration, while daytime NEE ranged from 0.32 to −4.36 µmol CO2 m⁻² s⁻¹, indicating net CO2 uptake. Negative daytime NEE was observed on all measurement dates for most plots, including post-fire burned plots, coincident with late-season germination of B. tectorum. Daytime NEE measured in burned plots actually became more negative relative to values measured in these plots before they were burned, whereas nighttime values remained unchanged. These patterns highlight the importance of IAGs in mediating short-term carbon exchange in recently disturbed sagebrush ecosystems. This work aims to provide new insight into the short-term carbon dynamics of fire-prone sagebrush systems and improve mechanistic understanding of disturbance-driven changes in ecosystem CO2 exchange.