There are many tools which land managers at Bosque del Apache utilize to accomplish the important work of habitat restoration on the refuge. Here, we see how a few of them – prescribed fire, heavy equipment and water infrastructure, used to flood and drain units – can serve as critical “tools of the land management trade”.
Natural Renewal on the Rio Grande – Making Way for Wet Meadows
Contains excerpts from articles previously published in Bosque Watch Summer 2021 by Amanda Walker, BdA Visitor Services Chief and Deb Williams, former Refuge Manager and Spring 2022 by Jessica Jia, former Visitor Services Chief.
It doesn’t take long for new life to sprout after a prescribed burn!
Water provides a lifeline in the desert. And millennia ago, water also provided something much bigger – change. Catastrophic river floods were once a regular part of the natural history of the Rio Grande Valley. Today at Bosque del Apache National Wildlife Refuge, staff must work hard to imitate the Rio Grande’s natural history in order to provide for wildlife the refuge protects.
To understand what natural processes once were here at Bosque del Apache, let’s go back in time and picture the historic Rio Grande. The narrow and seasonal river that we see running through the refuge today is only a remnant of a once incredible force. For thousands of years the Rio Grande was mighty and had a mind of its own. It might flow slow and wide one year, then the next year become a raging body of water that flooded and moved miles of land. Sudden major flood events would wreak havoc on bosque (riparian forests) and surrounding desert shrublands, but also renew them by turning over essential nutrients and exposing bare ground where new plants could grow. Decades ago, snow melt would amplify the Rio Grande each spring, carving trees and shrubs from soils and regularly changing its course as it meandered through the valley. After the river receded, grasses would take advantage of the plentiful nutrient-rich soils. Ducks, wading birds, and nesting grassland birds could be found eating seeds or taking shelter in the new growth. Changing river paths allowed for lush non-woody plant communities to grow. As time passed, trees took root providing lookouts for predators and perches for other migratory birds.
Wildfires would also regularly occur within the Rio Grande bosque: a nutrient-enhancing process which set back the successional stage and allowed grasses and wildflowers to take hold in areas once shaded by larger canopy trees. The skeletons of the larger trees remained after the fire, providing drying wood perfect for cavity-nesting woodpeckers and kestrels, perches for hawks and owls, and display locations for bluebirds, kingbirds, and flycatchers. Woody shrubs were reinvigorated as new growth replaced the dead stems, offering young vegetation for insects or browsing mammals. Today, the river is very different. Today’s Rio Grande is controlled by canals and dams, ensuring that it won’t destroy cities and can provide ample food from irrigated farm fields and household water for growing human populations.
Why is the history of the river important? Native species of plants still need that constant change to thrive. The plants need new nutrients, and the forests need bare soil for fresh young plants to grow – just as they once did before humans changed the river. The taming of the river makes the surrounding land vulnerable to non-native plant species taking over. Additionally, fallen limbs and dead trees start to build up where they never did before and thus create a hazard if lightning were to spark on the refuge. Undesired non-native species such as salt cedar, Russian olive, kochia, and Siberian elm start to grow thick. These non-native plants provide poor homes and nutrition for the native species that we protect – migratory ducks, endangered small mammals, and threatened forest bird species.
Prescribed fire is one tool refuge staff can utilize today to help recreate the important natural processes which the river once accomplished. We can renew the land by carefully using fire to redistribute nutrients, clear woody species overgrowth, and remove non-native plants. A little at a time, we attempt to recreate the jobs that the once-wild Rio Grande did to support many different habitats. The work isn’t easy: realities of modern times often conflict. At the refuge, these realities include the needs of endangered and threatened species, the unpredictability of water supplies which support certain habitats at different times of the year, and fire hazards.
Prescribed fires on the refuge are closely attended by wildland fire crews.
But by mimicking natural processes, we can begin the long task of restoration, such as in spring 2021, when fire was applied in the area south of the Dabbler/Diver Deck on the South Loop. Habitat in this area is now transforming from decadent willow scrub into wet meadow. Seasonally, you may encounter meadowlarks, roadrunners, or mule deer foraging or raising their young. Blackened trees may host flickers, doves, or bluebirds. In time, the shrubs and grasses will once again cover the ground, and resilient cottonwoods will overshadow the wildflowers and provide shelter, food, or perches for a variety of wildlife, while cavity nesters will occupy the once-standing cottonwoods. What will this habitat eventually look like? At Bosque del Apache, a mixture of salt grass, cottonwoods, willows, sacaton, and yerba mansa identifies wet meadows. These habitats would have been prevalent in the Middle Rio Grande Valley historically as ebbs and flows of the wild river created open areas for grasses to find a home.
Mere months after a prescribed burn occurs, saltgrass and willows take hold of the blackened soil.
Another prescribed burn in spring 2022 along the edge of the North Tour Loop cleared piles of non-native trees, like salt cedar and Russian olive, which had been previously removed and stacked there utilizing heavy equipment. This burn not only cleared the brush, but also returned nutrients to the soil, resetting the plant life. Now, a year later, blackened soils have sprouted with thickly budding yerba mansa flowers, thin golden wisps of sacaton, and fragrant mesquite shrubs. Tender green shoots of salt grass have emerged to replace the dry salt cedar. The land is transformed!
The pattern of destruction and regeneration is a healthy and normal cycle for the landscape. Although humans must now imitating the work of the once-wild Rio Grande, the response of the plants and wildlife shows that these tools are working: new places for wildlife to eat, nest, and rest. Perhaps soon, endangered desert species will expand their known range within the refuge, and in turn, show us that the landscape is returning to a historic abundance of life.
Managing for Invasive Cocklebur
Contains excerpts from an article previously published in Bosque Watch Summer 2019 by Jeff Sanchez, former Supervisory Biologist.
BdA Water Manager, Gerad Montoya, standing in a highly-productive unit of millet and various other desirable seed-bearing plants.
As climatic conditions fluctuate year to year, refuge staff must be extremely adaptive and do their best to follow Mother Nature’s lead. They have a few tools in the bag that help promote desirable plant growth to serve as food for ducks, geese, and cranes during the upcoming fall, winter, and spring months. Maintaining the wetlands at Bosque del Apache is a true labor of love, one that requires year-round work, endless planning, and extensive collaboration and teamwork. The wetland plan is complex, and it drives management practices in every season.
One of the most important summer wetland prescriptions, which is necessary to promote desirable plant species, is cocklebur treatments. Once all the wetland units are drawn down strategically, usually by mid-to-late May, staff begin assessing the wetland plant response that soon follows, hoping to observe wetland units full of young millet, sprangletop, smartweed, and a diversity of seed-bearing plants. Unfortunately, though, many times the first plant to germinate is the invasive cocklebur. Despite best efforts, some units are overtaken by cocklebur and require an additional prescription beginning in mid-June. Cocklebur has poor feed value to most wildlife and has the ability to grow quickly and out-compete the plants that later meet waterfowl needs. Staff strategically stagger drawdowns for the 70+ wetland units on the refuge so that not all plants start growing at the same time (specifically cocklebur). Timing plant growth allows refuge staff to spread cocklebur treatments over three months, from June to August. Unfortunately, we do not have the staffing or equipment required to treat cocklebur infestations during a short timeframe.
A cocklebur treatment entails mowing and flooding. Cocklebur plants are mowed as close to the ground as possible when they are less than six inches high. This treatment should occur before desirable plant species growing beneath the cocklebur get tall enough to be negatively impacted by mowing.
Mowing cocklebur after it has grown beyond the six-inch mark. Note the monotypic growth pattern as cocklebur takes over if left to grow.
After mowing, the unit is flooded as quickly as possible, inundating the cut cocklebur stems. Water is then held on top of them for three days before flushing the unit. This not only kills the cocklebur, but also irrigates the desirable grasses, rushes/sedges, and broadleaf plants growing under the cocklebur stands. If water is held too long, you run the risk of damaging desirable annual grasses and broadleaf plants. During this same timeframe, refuge staff are also irrigating (dependent on monsoonal rains) the remaining units that do not require cocklebur treatments; this maintains growth of valuable food resources for cranes and other waterfowl.
Cocklebur treatment is critical if we hope to maintain a high seed yield of desirable plants within our wetland units, and these efforts are highly dependent on water availability. It is refuge staff teamwork, along with support from the public, Friends, and other divisions of the Fish and Wildlife Service, that allows Bosque del Apache to continue providing waterfowl feed for the thousands of birds that call the refuge home during the winter months.