Trends of forest and ecosystem services changes in the Mescalero Apache Tribal Lands.

Forests are critically important for the provision of ecosystem services. The Sacramento Mountains of New Mexico, USA, are a hotspot for conservation management and the Mescalero Apache Tribe's homeland. The multiple ecosystem services and functions and its high vulnerability to changes in climate conditions make their forests of ecological, cultural, and social importance. We used data from the Mescalero Apache Tribal Lands (MATL) Continuous Forest Inventory over 30 yr to analyze changes in the structure and composition of ecosystems as well as trends in ecosystem services. Many provisioning, regulating, cultural, and supporting services were shared among the MATL ecosystems and were tied to foundational species dominance, which could serve as a reliable indicator of ecosystem functioning. Our analysis indicates that the MATL are in an ongoing transition from conifer forests to woodlands with declines in two foundation species, quaking aspen and ponderosa pine, linked to past forest management and changing climate. In addition, we detected a decrease in species richness and tree size variability, amplifying the risk of forest loss in a rapid climatic change. Continuous permanent plots located on a dense grid (1 × 1 km) such as the ones monitored by the Bureau of Indian Affairs are the most detailed data available to estimate forests multiresource transitions over time. Native lands across the USA could serve as the leading edge of detecting decadal-scale forest changes and tracking climate impacts.

Fire regime on a cultural landscape: Navajo Nation.

Fire has played an important role in the evolutionary environment of global ecosystems, and Indigenous peoples have long managed natural resources in these fire-prone environments. We worked with the Navajo Nation Forestry Department to evaluate the historical role of fire on a 50 km2 landscape bisected by a natural mountain pass. We used fifty 5-ha circular plots to collect proxy fire history data on fire-scarred trees, stumps, logs, and snags in a coniferous forest centered on a key mountain pass. The fire history data were categorized into three groups: All (all 50 plots), Corridor (25 plots closest to Buffalo Pass drainage), and Outer (remaining 25 plots, farther from pass). We assessed spatial and temporal patterns of fire recurrence and fire-climate relationships. The landscape experienced frequent fires from 1644, the earliest fire date with sufficient sample depth, to 1920, after which fire occurrence was interrupted. The mean fire interval (MFI) for fire dates scarring 10% or more of the samples was 6.25 years; there were 13 large-scale fires identified with the 25% filter with an MFI of 22.6 years. Fire regimes varied over the landscape, with an early reduction in fire occurrence after 1829, likely associated with pastoralism, in the outer uplands away from the pass. In contrast, the pass corridor had continuing fire occurrence until the early 20th century.Synthesis. Fires were synchronized with large-scale top-down climatic oscillations (drought and La Niña), but the spatially explicit landscape sampling design allowed us to detect bottom-up factors of topography, livestock grazing, and human movement patterns that interacted in complex ways to influence the fire regime at fine scales. Since the early 20th century, however, fires have been completely excluded. Fuel accumulation in the absence of fire and warming climate present challenges for future management.