Riparian Zones in Winter What are the differences

Riparian Zones in Winter “What are the differences in the tree species between riparian zones and upland zones in winter? ” Tim Moret Winter Ecology – Spring 2005 Mountain Research Station – University of Colorado,

Introduction § Riparian zone encompasses the strip of land between the stream channel and hillslope § Sometimes referred to as the valley floor, near-stream zone § Differentiated from upland zones by unique hydrology, topography, vegetation, and soils § Because of their location, they have significant potential to regulate the movement of water § elements in surface § subsurface runoff that flows from upslope areas to the stream § Tree species § improve fish and wildlife habitat § act as nutrient sinks § As interest in water quality increases, riparian zone management is improving and evolving § people are looking for tree species that grow well in areas that are periodically flooded.

What is important about tree species in riparian habitats? § Trees are very effective nutrient filters § can modify some environmental impacts of agricultural practices. § act as nutrient sinks § Tree species improve fish and wildlife habitat § food and shelter § Ecology improved by species of trees that are fairly flood resistant § can be a problem especially with rapid snowmelt in the mountains.

What kinds of trees are found in Colorado mountain riparian zones? § Trembling or Quaking Aspen § River (Water) Birch § Arroyo Willows (29 different species) § Thin-leaf Alders § Narrow-leaf Cottonwood § Box-Elder § Rocky Mountain Maple § Shrubs § Ashes § Blue Spruce

How does that differ from upland zones in the mountains? § § § § § Lodgepole Pines Englemann Spruces Douglas Firs Limber Pine Sub-Alpine Fir Ponderosa Pine White Fir White Pine Colorado Blue Spruce Aspen and Gamble Oak

Why the discrepancy? § The big factors are water and sunlight. § Conifers need less water to survive § slower growers than the local deciduous trees § This leads to the conifers being able to spread farther out § leaving the riparian space to those who need it § Conifers also need less sunlight whereas the deciduous trees need a lot more § § § Deciduous then flock to where the dense conifer canopy is parted they can receive more direct rays Deciduous do most of their growing in the summer months able to shed their leaves § Evergreen grow all year round so they must retain their needles § Conifers are adapted to harsher environments where their deciduous neighbors are unable to follow, giving them reason to spread out into the upland montane and sub-alpine environments § So many things work in conjunction to provide this divided situation.

My Investigation § Question: Whether the riparian zone still supports a greater diversity of life than the upland in winter months? What does this mean for regional ecology? § Diversity of life measured in the number of species clearly identifiable to my eye in each zone § Take samples in different locations

Small Stream Bed near Meeting Hall § § § Distinguishable riparian zone: 10 paces by 40 paces Stream Width: 2 paces Identifiable species: 3 § § § Willow Aspen River Birch § Nearby upland zone: 10 paces out on either side § Identifiable species: 4 § § Lodgepole Englemann Sub-Alpine Limber § Clearly definable boundary between zones? NO

Medium Stream Bed Crossing Road § Distinguishable riparian zone: 40 paces by 40 paces § Stream Width: 10 paces § Identifiable species: 8 § § § Willow Aspen River Birch Alder Shrubs (3+) § Nearby upland zone: 10 paces out on either side § Identifiable species: 4 § § Lodgepole Englemann Sub-Alpine Limber § Clearly definable boundary between zones? YES

Large Stream Bed up near the Campground § Distinguishable riparian zone: 60 paces by 40 paces § Stream Width: 15 paces § Identifiable species: 8 § § § Willow Aspen River Birch Alder Shrubs (3+) § Nearby upland zone: 10 paces out on either side § Identifiable species: 5 § § § Lodgepole Englemann Sub-Alpine Limber Blue Spruce § Clearly definable boundary between zones? YES

Graphed Results

Crossover of Species Between Zones

Conclusions I have drawn from my investigation § Curious about if the advent of winter also brought on an equalizing effect to the diversity discrepancy between riparian zones and upland zones…

Conclusions § Somewhat of a change § Some smaller plants died off because of the season § Deciduous plants do not die in winter though, obviously, so not as much as I might have predicted § However, upland forests did exceed riparian zones in smaller streams § Leading to conclusion that size of the stream probably has an effect on diversity it is able to sustain § Montane forests’ diversity stayed fairly similar throughout the testing § But I believe that there is an equalizing effect going on § Results not perfect § I used the broad category of shrubs to represent at least 3+ species § My testing area was small for testing species diversity § My species identification is at beginner level, especially with deciduous trees without leaves § Death and dormant is hard to distinguish

Extrapolate to Ecological Effects § What does this mean for the region and why would someone care? § Refer back to functions of riparian zones § Reduction in species diversity during the winter probably also means reduction in number of plants § Could also mean losing plants that have very important functions § Nutrient filtering could be impaired if it is needed in winter because stream water is usually still flowing § Habitat loss or food loss for local wildlife, spawning either a press of resources or a necessary migration § Floods may be more damaging in the winter thaw and spring melt because the plants have not returned after the winter yet. § However all of these issues probably deserve specified studies of their own rather than inferences

In Summary… § Species diversity is reduced during the winter which may or may not have ecological consequences § Smaller streams will have less clearly definable boundaries between their zones, making winter’s effect more pronounced § Larger streams will support more diversity in general and possibly lose less in the winter

Sources § § § § Dickson, James G. “Managing Streamside Zones for Wildlife. ” NWTF Wildlife Bulletin No. 17 Colorado Native Plant Society. “Suggested Native Plants for Horticultural Use on the Front Range of Colorado. ” Revised April 2001. Barkley, Yvonne Carree and Ron Mahoney. “Riparian Zone Tree Plantings. ” UI Extension Forestry Information Series. Tree Planting and Care No. 3. University of Idaho. Mc. Glynn, B. L. In press. The role of riparian zones in steep mountain catchments. in Global Change and Mountain Regions. “Advances in Global Change Research book series”, Martin Beniston (ed), Kluwer. “Trees Along Streams. ” Forest and Wildlife Benefits on Private Lands. Missouri Department of Conservation. Copyright 1994. “Biotic Communities of the Colorado Plateau. ” Land Use History of North America: Colorado Plateau. http: //www. cpluhna. nau. edu/Biota/mixedconifer. htm. USDA Forest Service. 1993. “Changing conditions in southwestern forests and implications on land stewardship. U. S. Forest Service, Southwest Region, Albuquerque, N. M. , 8 pp. Weber, William A. Rocky Mountain Flora. University of Colorado Press. Copyright 1967