麻豆视频

From crusts and dust to nuts and chains to climate and cattle, grad student aims to fill gaps in knowledge of vast and important woodlands

Ecosystems dominated by species of pi帽on and juniper, a spatially extensive vegetation type in the United States, are among the most predominant vegetation types administered by U.S. land management agencies.

That means, among other things, that millions of acres of pi帽on-juniper woodlands have been subjected to numerous land-management techniques since 1950, including various methods of tree removal.

The long-term consequences of those actions are still poorly understood, but听, a doctoral student in the University of Colorado听Boulder Department of Ecology and Evolutionary Biology (EBIO) has been working hard to change that.

In just the past two years Redmond has been the lead author on several papers examining the precipitous decline of pi帽on-nut production and the effects of vegetation management on Bureau of Land Management lands, including the effects of burning, chaining and 鈥渕astication鈥� to remove woody plants in an effort to increase grasses for grazing livestock, restore wildlife habitat, and reduce the risk of wildland fires.

鈥淲e use our national lands pretty heavily. We enjoy them and the services they provide鈥濃�攅verything from recreation to livestock grazing to water management鈥斺�渁nd it鈥檚 important to know how to effectively manage them for both the increased resilience of ecosystems in the future and to maintain them today,鈥� says Redmond from Cape Town, South Africa, where she currently is studying invasive woody species.

Redmond and her frequent co-author, EBIO Assistant Professor听, have carved out something of a niche as pi帽on specialists, from the effects of climate change on pi帽on-nut production to management techniques and tree regeneration following mortality from pine beetles and drought.

滨苍听, co-authored by Barger and Frank Forcella of the U.S. Agricultural Research Service, the researchers found that pi帽on-pine seed production has declined by 40 percent at nine study sites across New Mexico and northwestern Oklahoma since 1970. The study was the first to look at the effects of climate change on pi帽on cone production.

The biggest declines in cone production we measured were in areas with greater increases in temperatures over the past several decades during the March to October growing season

The nuts, a small but culturally and economically important product in the Southwest, particularly among American Indians and other harvesters, take two years to mature. Production is higher when late-summer temperatures are cool, Redmond says.

鈥淭he biggest declines in cone production we measured were in areas with greater increases in temperatures over the past several decades during the March to October growing season,鈥� she says.

For decades, federal land managers sought to alter pi帽on-juniper and other ecosystems to restore understory plant cover and maximize grazing potential, without understanding long-term consequences. They also frequently planted non-native species such as crested wheatgrass, which still thrives in many places today. More recently, management plans have sought to reduce catastrophic fire while restoring these native ecosystems.

Redmond also was lead author on a paper in the July 2014 issue of听听that examined how three 鈥渨oody fuel reduction鈥� techniques affect herbaceous understory in pi帽on-juniper woodlands two years after they are applied.

鈥淲e found that two treatments, broadcast burning and mastication, resulted in a large increase in herbaceous cover. But the broadcast burn resulted in really large increases in invasive species, where the mastication didn鈥檛,鈥� Redmond says. 鈥淭hat suggests mastication may be the more effective treatment.鈥�

Another paper, published in the June 2013 issue of听Forest Ecology and Management, found that 鈥渃haining鈥� to reduce pi帽on-juniper cover resulted in increased long-term grass growth. But chaining and/or post-treatment grazing patterns also reduced 鈥渂iocrust cover,鈥� which stabilize soils and can provide an important source of nitrogen to these semi-arid ecosystems.

Other researchers are investigating the implications of diminished biological soil crusts, including possible links to dust storms, which, in turn, may have unforeseen consequences. For example, red dust from a hundred miles away accumulates on high-mountain snowfields and glaciers, causing faster snowmelt. Dust storms also can cause traffic accidents, breathing problems and asthma in metropolitan areas.

Crusts and dust, nuts and chains, climate and cattle鈥擱edmond ultimately sees herself as connecting these and other myriad dots.

As Barger observes: 鈥淧inon-juniper ecosystems are important vegetation type across the western U.S. providing critical wildlife habitat and resources for human (e.g. firewood, pine nuts). Over the past decade we have observed substantial mortality across some regions.

鈥淭he important question is, what comes next after a significant mortality event and what will vegetation response to these mortaility events look like in a world that is warmer and drier than when many of these very old trees were born? Miranda鈥檚 work is critically important in answering these questions.鈥�

鈥淭he goal of my dissertation is to understand the effects of climate change and land management on pi帽on-juniper ecosystems. I want to highlight that we really do need more research to understand the implications, the longer-term and shorter-term effects,鈥� she says.

Clay Evans is director of public relations for听.