West-side Prairies & Woodlands

Transcription

1 Washington State Natural Regions Beyond the Treeline:, Alpine & Drylands Beyond the Forested Ecosystems: WA Dept. of Natural Resources 1998 West-side & Woodlands 1. South Puget Sound prairies & oak woodlands 2. Island / Peninsula coastal prairies & woodlands 3. Rocky balds West-side in Grey San Juan Island Olympic Peninsula South Puget WA GAP Analysis project 1996 West-side Oak Woodland & Prairie Ecosystems in Grey Olympic Peninsula South Puget San Juan Island Grasslands dominated by Grasses Herbs Bracken fern Mosses & lichens With scattered shrubs WA GAP Analysis project 1996 Camas (Camassia quamash) 1

2 Some of these are mounded prairies Mounded prairie Mima Mounds Research Natural Area Scattered shrubs Lichen mats in the prairie Serviceberry Cascara As unique ecosystems they provide habitat for unique plants As unique ecosystems they provide habitat for unique critters Camas (Camassia quamash) Mazama Pocket Gopher Golden paintbrush (Castilleja levisecta) Many unique species of butterflies (this is an Anise Swallowtail) Photos from Dunn & Ewing (1997) 2

3 Fire is an important & natural part of ecosystems Garry Oak Woodlands Often associated with prairies Riparian corridors in prairies Extensive in Islands & BC Photo from Dunn & Ewing 1997 Quercus garryana Important Habitat Garry Oak Woodlands : Human Impacts Current prairie cover is about % of its historical extent in South Puget Sound Causes of Prairie Loss Hall (1995) Urban development % Forest invasion % Tacoma Agriculture % Olympia Streaked horned lark Mazama pocket gopher Mardon skipper & other butterflies Western gray squirrel Crawford & Hall 1997 South Sound : Protected Areas South Sound : Protected Areas 3

4 Fort Lewis & McChord Air Base: Protected Areas > 75,000 acres of training grounds : Human Impacts Invasive Species are another threat Tacoma 86,000 acre reservation Olympia Fort Lewis Scot s Broom (Cytisus scoparius) Fort Lewis : Human Impacts Control of Scot s Broom These prairies & woodlands exist within the same climate as the surrounding sea of evergreen forest. WHY? Pulling Burning A central question: What prevents the forest from existing here? What Restricts Forest Cover? PLANT INVESTMENTS Sugar What Restricts Forest Cover? Wood becomes a luxury in droughty conditions Sugar Woody Plant Herbaceous Plant Woody Plant Herbaceous Plant leaves wood roots leaves roots leaves wood roots leaves roots NOW IMAGINE DROUGHT CONDITIONS Which can better support its leaves with drought? This suggests herbaceous plants will do better in drier locations Are these prairies & woodlands in drier locations? 4

5 To understand if our west-side prairies are in dry sites we must understand the history of the ground beneath! 18,000 YBP 15,000 YBP Glacier recedes 12-15,000 YBP Coarse, droughty substrate 10-12,000 YBP Grasses & forbs establish 10,000 YBP Soil holds more water & nutrients Trees & shrubs begin to establish 9-10,000 YBP Organic matter added; Soil building 7-10,000 YBP Climate shift: HYPSITHERMAL Too warm & dry for trees; prairies remain 5-7,000 YBP Climate cools & becomes more wet Trees & shrubs begin to establish again Humans arrive 5-7,000 YBP Climate cools & becomes more wet Trees & shrubs begin to establish again Humans arrive 200-7,000 YBP We would expect: Soil OM builds rapidly Forest establishes 200-7,000 YBP FIRE Native Americans use fire to keep trees & shrubs out maintaining prairie 5

6 West-side & Woodlands Post European settlement Fire suppression allows forest succession to proceed 1. South Puget Sound prairies & oak woodlands 2. Island / Peninsula coastal prairies & woodlands How do we maintain these unique ecosystems in the face of natural succession to forests? in San Juan Islands, NE Olympic Peninsula & Coastal Bluffs Just a little different Coarse, dry post-glacial soils Rainshadow low precipitation Rainshadow of the San Juans & NE Olympic Peninsula Inches of annual precipitation in San Juan Islands, NE Olympic Peninsula & Coastal Bluffs Just a little different West-side & Woodlands Coarse, dry post-glacial soils Rainshadow low precipitation Wind exposed Unusual soil chemistry 1. South Puget Sound prairies & oak woodlands 2. Island / Peninsula coastal prairies & woodlands 3. Rocky balds 6

7 Rocky Balds: another west-side ecosystem not dominated by trees West-side & Woodlands Windswept resistant bedrock outcrops Rocky balds South Puget Sound prairies & oak woodlands Island / Peninsula coastal prairies & woodlands More common on San Juan Islands Unique, rare species Lord Hill, Snohomish County What is the common reason all of these ecosystems exist? How is that different from the factors that tend to control ecosystem existence for our more extensive ecosystems? 7