Vegetation Production and Phenology at Black Canyon of the Gunnison National Park, 2000–2019

Black Canyon of the Gunnison River illustrates the extreme depth and narrowness that define one of North America’s most dramatic river canyons.

NPS/A. Washuta

What We Wanted to Know

Between 2000 and 2019, scientists at the Northern Colorado Plateau Network used satellite imagery and climate data to understand the impacts of climate variation on vegetation at Black Canyon of the Gunnison National Park. During that time, plants experienced stress during dry years, but overall, there was a slight upward trend in plant growth throughout the study.

The park’s plant communities show resilience to dry times but face increasing risk from shifting temperatures and drought. This study aimed to uncover when and where vegetation might change and why, using long-term climate and vegetation observations to guide future management.

At-a-Glance

• Vegetation production in-creased in 98% of BLCA from 2000 to 2019.
• Quaking Aspen, Mixed Montane Shrublands, and Mesic Sagebrush had the fastest gains.
• Drought tolerance and climate sensitivity varied across vegetation groups.
• The growing season lengthened by nearly 3 days due to earlier green-up and later senescence.

What We Did

Researchers used NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer) satellite imagery to evaluate vegetation production and its sensitivity to climate over 20 years. They assessed more than 260 vegetation map units across 13 vegetation alliance groups, including Mixed Montane Shrubland, Pinyon-Juniper and Mesic Sagebrush, that are dominant types in the park.

By pairing remote-sensing and weather data, they tracked phenological changes like green-up, peak growth, and senescence (go dormant). The study identified “pivot points” (the value of a climate variable where vegetation teeters between below- and above-average condition) and “responses” (amount vegetation production changes in response to changes in a climate variable). These indicators reveal climate sensitivity and help forecast potential shifts in plant communities.

What’s phenology?

Phenology is the study of seasonal biological events—like when plants sprout leaves, flower, or go dormant—and how these events are influenced by climate and weather.

What We Learned

Although the study began during a dry period, growing season vegetation production at Black Canyon of the Gunnison National Park increased, likely driven by modest gains in precipitation and more efficient water use. However, not all areas responded equally to these conditions (Figure 1).

Figure 1. Pivot points and responses for 13 polygon types relative to water-year precipitation. Steeper lines indicate greater sensitivity; lines shifted left indicate greater drought tolerance.

NPS/D. Thoma

What are legacy effects?

Legacy effects occur when past climate conditions—like several dry years—continue to influence plant growth today. This means vegetation health often reflects multi-year trends, not just the current season.

Figure 2. Pivot points and responses for 13 polygon types relative to water-year actual evapotranspiration. Steeper lines indicate greater sensitivity; lines shifted left indicate greater drought tolerance.

NPS/D. Thoma

Changes in phenology were also observed. By 2019, green-up occurred nearly two days earlier, and senescence came more than two days later, compared to 2000. These subtle shifts extended the growing season by nearly three days and indicate altered vegetation timing that could affect broader ecological processes.

What We Recommend

Park managers can use the results of this study—and the tools developed from it—to interpret vegetation response in real time, anticipate future conditions, and inform both near-term decisions and long-term conservation goals:

Use pivot points to interpret current conditions

Real-time climate data—such as soil moisture, precipitation, or evapotranspiration—can be compared to vegetation-specific pivot points. This “now-cast” approach allows managers to estimate whether current-year vegetation production is likely to be above or below average (without the complexity of analyzing satellite imagery), helping guide timely decisions during drought or high-heat events.

Adjust interpretation based on accuracy

Pivot points are subject to a margin of error. When current climate conditions fall within the standard error of a pivot point, vegetation performance is best interpreted as “near average.” This guidance helps managers be more confident that vegetation change is likely if current conditions fall well above or below a climate pivot point.

Incorporate findings into vulnerability assessments

The study provides a foundation for identifying vegetation types with low drought tolerance or high climate sensitivity. These findings can inform future planning and help prioritize areas most susceptible and most likely to change.

Prioritize high-value or sensitive areas

High value vegetation that is important as wildlife habitat, forage or even visitor enjoyment, such as shade trees near campgrounds, picnic areas, and overlooks, may warrant higher management concern if it is very climate sensitive. Vegetation types with declining or variable productivity—such as Douglas fir and Disturbed—may need focused monitoring for early detection of undesirable change.

Information in this article was summarized from Landscape Phenology, Vegetation Condition, and Relations with Climate at Black Canyon of the Gunnison National Park, 2000-2019 by D. Thoma. Content was edited and formatted for the web by E. Rendleman.

Tags: black canyon of the gunnison national park, ncpn, inventory and monitoring division, northern colorado plateau network, phenology, satellite observation, vegetation monitoring, remote sensing, phenology monitoring, long-term monitoring, monitoring, northern colorado plateau, inventory and monitoring program, blca