Montane meadows

Montane meadows are geographically limited to the high elevation mountain ranges. For example, in the Colorado Plateau the meadows typically start between 7,500 and 8,500 feet (2,286 and 2,591 meters) in elevation, with some variation depending upon location. These meadows are nestled within mountains around the globe, including the Alps and Pyrenees in Europe, the Himalayas in Asia, the Andes in South America, and the western mountain ranges in the United States. Despite the disparate geographic locations, they do have some climatological similarities.

Temperatures in montane meadows are generally cool, and precipitation is generally high. In Arizona montane meadows, the temperatures can range from minus 46 degrees F (8 degrees C) for a low in January to 80 degrees F (27 degrees C) for a high in July. Montane meadows, on average, are wetter than many other grassland biomes. These meadows receive multiple sources of water, including the melt of the winter snow from the surrounding mountains as well as rain from the annual summer monsoons. The monsoons start in July and last through October, helping to maintain a higher than average annual precipitation. This precipitation can range anywhere from 20 to 35 inches (508 to 889 millimeters), which allows for a rich floral community with substantial ground cover in the wetter areas.

The floral and faunal composition of montane meadows is unique and these meadows are often surrounded by encroaching pine forests. Vegetation in montane meadows will vary depending on geographic location. However, the patterns are similar and consist of grasses, forbs, and shrubs. Grasslands can include brome grasses and fescues. Forbs can include fleabane, scarlet gilia, and yarrow. The shrubs include rabbitbrush and sagebrush. Conifer forests that surround these meadows vary in species composition based on geographic location. Forests in Arizona include ponderosa pines, aspen, and mixed conifer forests.

The conifer forests that surround the meadows are constantly moving in. The main force that limits their takeover is the presence of an active fire regime. Fire drives the nontolerant tree seedlings and forest herbs back to the established tree line. Research in 2009 by the Joint Fire Science Program suggests that the meadows are shrinking in size due to conifer encroachment. In fact, meadow species tend to get replaced by forest herbs within just a few decades of tree invasion. Fire is very important to meadow maintenance, and research suggests that it takes a careful mixture of prescribed burns and tree removal to help maintain meadows. Interestingly, burning itself does not seem to impact meadow species, but burning does drive back forest herbs. Alternatively, it is the tree removal that seems to directly benefit and maintain the meadow species.

Montane meadows are fragile from a conservation perspective, which comes in part from an inadequate seed bank. Normally, a stable seed bank will lead to species maintenance, or in the case of disturbance, recovery. Almost 75 percent of the species that define montane meadows are absent from the soil seed bank. This means that once an area has been disturbed, the damage is permanent unless an active recovery effort takes place. Typical natural disturbances include water erosion, drought, and ungulate grazing.

Anthropogenic disturbances include climate change that will invariably impact moisture levels. Despite these higher than average precipitation levels, montane meadows can vary in moisture levels between wetter and drier conditions. Because of this variation, these meadows will be impacted differentially by climate change. Research by Diane Debinski of Iowa State University, using data collected from 1997 to 2007, suggests that long-term drought will negatively impact montane meadows by decreasing the number of flowering plants and their associated pollinators. When examining the reaction of wet to dry meadows to extensive drought, researchers have discovered that meadows with middle-of-the road moisture levels were the most susceptible to drought. Debinski concluded that dry meadows tended to just get drier and wet meadows tended to still have moisture that kept some consistency of the vegetation. However, meadows that depended upon some moisture (medium amounts) had a vegetation shift to more drought-tolerant species or a disappearance of cover overall, which will eventually impact pollinators of the region.

Vegetation in the montane meadows ultimately drives the faunal composition. Grasslands in the United States attract grazers such as mule deer and elk. Floral plants and their fruit attract pollinators such as white-lined sphinx hawkmoths (Hyles lineata) and Rufous hummingbirds (Selasphorus rufus) and frugivores such as Heliothis spp. caterpillars. Grazing by ungulates is a natural process in the montane meadows and in fact has an important consequence in shaping plant life histories.

Scarlet gilia (Ipomopsis spp.) has a unique life-history strategy whereby plants in certain populations actually benefit from being browsed. Scarlet gilia initially germinates to form a rosette. The plants can stay in this form anywhere from two to 10 years. If the plants are not browsed, they will send up a single aboveground shoot that will flower and set seed. However, if plants are browsed at this stage, some populations will send up multiple stalks that produce on average twice as many flowers, set seed, and reproduce. This will increase the overall seed production and plant fitness and is known as overcompensation or tolerance.

Not all plants are able to overcompensate, and browsing and grazing can be detrimental to this ecosystem if left unchecked. Constant grazing by cattle can change the vegetation composition, cause water tables to decline, and increase tree density. Grazing is among one of many disturbances currently impacting the range and quality of montane meadows. Combined with tree encroachment, changing fire regimes, and climate change, the future of montane meadows remains questionable.