Tree Invasion

Tree Invasion by Randy Rodgers wildlife biologist, Hays photos by Mike Blair It’s time to change the way we look at trees on the prairies. While trees provide habitat for some wildlife, they pose a serious threat to grassland-dependent species. Randy Rodgers photo think that I shall never were Daniel Boone and Davy As early as 1873, Nebraska see, anything so lovely Crockett, woodsmen of the Senator Phineas Hitchcock “Ias a tree.” At least, highest caliber, at least on TV. introduced the Timber Culture that’s the version of the first Now, I better understand the Act. As federal law, this legisla- two lines of Joyce Kilmer’s values of trees for shade, for tion offered 160 acres of prairie poem, “Trees,” that I had in my respite from the wind, and as land to anyone who would head for years. I recently habitat for many species. plant 40 of those acres to trees. learned that the poem actually Perhaps those of us who live Years later, University of begins “I think that I shall never in prairie states value trees Nebraska botany professor see/A poem lovely as a tree.” more than those who live in Charles Bessey advanced the Either way, these words reflect more timbered regions. Those idea that the vast grasslands of deeply-held values for genera- roots go way back. Who hasn’t the Nebraska Sandhills should tions of Americans. heard accounts of European set- rightfully be pine forest. The No doubt, I stand among the tlers cursing the incessant wind, level of enthusiasm with which countless people who place the blazing summer sun, and his idea was embraced then, great value on trees. As a boy, I sheer exposure of the Great and even now, is evidenced by climbed them, drew them, and Plains? It’s not hard to under- the Bessey Ranger District of the explored kid-sized wilderness stand why they and their Nebraska National Forest near wherever I could roam through descendants were determined Halsey. There, about 30 square even an acre of them. My heroes to change this land. miles of man-planted forest, in 1 the middle of one of North America’s greatest remaining grasslands, attest to our love for trees — and perhaps to our underdeveloped appreciation of grassland. The weather of the Great Plains can be harsh and the beauty of our grasslands subtle. But I can’t help but believe that Kilmer would also have waxed poetic had he seen a bluestem prairie’s rosy glow in the refracted light of an October sunset. Unfortunately, too few of us appreciate the beauty or Randy Rodgers photos comprehend the true value of Eastern redcedars pose a serious threat to this midgrass prairie in Russell County. our Great Plains grasslands. Trees can be controlled with fire, cutting, or spraying — sooner better than later. This poor understanding of grasslands, coupled with our bring the more moderate condi- immune. Eastern redcedar, culture’s love of trees, has laid tions and the wildlife of the east hedge (Osage orange), and the foundation for a change that out onto the plains, at least on blackjack oak have invaded sub- threatens our signature land- small scales. Alone, these tree stantial parts of our largest and scape — the prairies — like plantings have altered, but per- best known prairie region, the nothing since John Deere’s haps not seriously threatened, Flint Hills. Russian olive, cedar, invention of the moldboard our remaining prairie ecosys- black locust, and honeylocust plow. tems. But our collective failure have rapidly spread across our For more than a century, we to understand the needs of our central Kansas sand prairies. have planted and nurtured trees prairies has often resulted in Redcedar is devouring the across the Great Plains. The ben- grassland management or, more prairies of the Red Hills. In the efits were clear: windbreaks for correctly, lack of management Smoky Hills, cedar and hedge farmsteads, crop fields, live- that has permitted some species are the main culprits. Even in stock, and wildlife allowed us to of trees to escape their original western Kansas, where dry con- planting sites. Fire, ditions might seemingly prevent the prairie’s natural tree invasion, a hodgepodge of ally, was often sup- trees are making inroads into pressed and midgrass and shortgrass grazing was some- prairies, as well as many times misapplied, Conservation Reserve grass- leading to a weak- lands. ened prairie com- So, what’s so bad about a mix munity vulnerable of grassland and trees? After all, to what has become there are many natural savannas an onslaught of where trees and grasslands com- invasive trees. Such bine to make diverse and beau- species are now tiful landscapes. It’s not so swallowing our much that there’s anything Osage orange, commonly called hedge, can’t be killed grasslands at an intrinsically wrong with this with fire. Reclaiming this pasture will require cutting and alarming rate. combination. But it’s the immediate treatment of the stumps with a herbicide. It seems no prairies, places that Kansans Kansas prairie is often take for granted, that actu- 2 ally are among Earth’s most threatened landscapes. Even where mechanical removal of trees has While there may be rela- occurred (note piles), tively fewer species present failure to follow up with in any one place, the controlled burning has per- prairie’s unique assemblage mitted small cedars to of wildlife is a rare treasure rapidly reinvade this pas- on the global scale. Many of ture. Piling cut trees is not a good idea as this removes us who live on the prairie grassland from production suffer from the illusion that for many years and creates meadowlarks are somehow habitat for mammalian ordinary, when nothing predators. could be further from the truth. Taken as a group, Randy Rodgers photos populations of grassland birds wise suitable prairie habitat in next. While other factors like have shown sharper and more many parts of our state. Greater prairie conversion and fragmen- widespread declines over recent prairie chickens have rapidly tation may be involved, it’s a decades than any other ecolog- lost ground in southeastern good bet that tree invasion has ical or behavioral guild of birds Kansas, as shown by long-term played a significant role in the in North America. surveys. The last time prairie greater prairie chicken’s demise. Grassland birds are probably chickens were observed on the Despite the fact that grasslands the best indicator of the decline 20-square -mile survey area in of adequate size are still present, of our prairies because many of Montgomery County was in lesser prairie chickens no longer these species are sensitive to 1987. They disappeared from occupy significant portions of change. Foremost among them the Wilson County area by 2000, their former range in Barber, are our two species of prairie the Elk County area by 2002, Harper, Kingman, Pratt, Reno, chickens. These birds are crea- and are all but gone on the Rice and Stafford counties. The tures of open spaces with clear Chautauqua County area. most evident explanation is tree horizons, but invasive trees Survey areas in Woodson, Allen, invasion. And trees now threaten have forced them from other- and Anderson counties may be occupied prairie chicken range farther west and north. It may be confusing to hear that prairie chickens in the Flint Hills are disappearing in some areas because of too little fire. More attention has gone to the opposite situation; annual spring burning of vast sections of the central Flint Hills and the associated early-intensive grazing system have left greater prairie chickens and other ground dwelling birds with little or no residual nesting cover. Neither of these fire extremes are what’s needed. Most prairie wildlife are adapted to a shifting mosaic of The manager of one Barber County pasture (left of fence) has done a good job of con- burned and unburned areas like trolling cedar invasion, but his neighbor has not. This creates a situation of continuous reinvasion of the well managed pasture with seed from the neighbor’s trees. that provided in the “patch burning – patch grazing” 3 system that mimics the dynamic is not an issue just for prairie landscape once created by fire chickens. Accumulating scien- and bison. That innovative tific evidence suggests that rela- system, developed at Oklahoma tively few trees can have major State University, is worthy of its negative impacts on those own story. Suffice it to say that species of birds that are highly burning once every three years dependent on open prairie — or even three years out of five the so-called grassland obligate would go far to improve the species. A recent study in future of greater prairie Arizona indicated that commu- chickens in the Flint Hills by nities of grassland songbirds maintaining prairie health, begin to decline in habitats with leaving nesting cover, and sup- as few as four junipers per acre. pressing tree invasion. Research in Oklahoma and Recent research has begun to other states have shown that offer an explanation of prairie grassland birds directly decline As trees encroach, the variety and chickens’ intolerance of number of predators increases. as trees encroach. Part of this invading trees. By radio decline may be tied to behav- marking lesser prairie chickens, ioral avoidance of vertical struc- students of Kansas State chickens than we might have ture, as has been seen with University professor Robert originally believed. This behav- prairie chickens. Research in Robel have revealed some ioral avoidance means it won’t southwestern Missouri found important clues. While tree take a sweeping front of wood- that even diminutive Henslow’s invasion was not an issue on the land but only widely-scattered sparrows avoided woody cover, sandsage prairie study area, trees to eliminate prairie albeit to a lesser degree.

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