Coquille Subbasin Working Atlas - p6

Vegetation and Land Cover

Vegetative cover and land use can be mapped in numerous ways. Systems for classifying vegetation types vary considerably depending on the needs of potential users and resources available in the mapping process. Due to the high degree of variability among different classification systems it is often difficult to combine vegetation maps from different sources. Maps of broad land use and vegetative types are developed from interpretation of aerial photography or satellite imagery and are useful for general purposes. Detailed maps with multiple vegetation classes require extensive field work, particularly where forest tree sizes or age classes are classified. The accuracy of these types of data can only be determined by independent assessments that compare map types to actual field observations. Three general vegetation and land cover maps are presented in this atlas. The accuracy of these thematic data are not quantified. While more detailed vegetation data does exist for the Coquille, none is available across the entire subbasin.

[click on map for larger version]

 

Land use and land cover

The land cover data show on the Land Use and Land Cover map is the 1979 USGS land use/land cover GIS data layer. Land use and land cover (LULC) data were derived from thematic overlays registered to 1:250,000-scale base maps. The LULC data provides broad information on urban or built up land, agricultural land, rangeland, forest land, water, wetlands, barren land, tundra, and perennial snow or ice. While the land use patterns shown in this USGS data layer are generally considered to be accurate, more detailed vegetation information is provided in the GAP analysis data.

As indicated by Figure 11, the vast majority of the Coquille basin is forested, with agriculture, rangeland, and urban areas making up the remainder of the basin. The lower Coquille subdivision is the most diverse area of the subbasin in terms of land use activities, although over 76% of this area is still in forest cover. Most of the agricultural activity occurs along the main fork of the Coquille from the area surrounding the city of Coquille to the city of Bandon. Over 15% of the lower Coquille subdivision is classified as agricultural land. Other small agricultural areas are located along various tributaries within the other subdivisions. Most of the rangeland within the subbasin occurs along the South Fork of the Coquille between Myrtle Point and Powers, although rangeland makes up little more than 4% of the land base in that subdivision. Residential and other urban areas are clustered around the main towns of the subbasin; Bandon, Coquille, Myrtle Point, and Powers. Nearly five percent of the Lower Coquille subdivision is classified in urban land uses. Table 5 lists total area by subdivision and broad cover type. Table 7 lists total area by land use type for the entire Coquille subbasin.

Table 5: Acres by Major Land Use and Land Cover Class by Subdivision
Subdivision	Agricultural	Rangeland	Forest	Urban or Built-up	Other
Coquille	16,686	1,332	83,573	5,336	1,934
East Fork	2,133	—	82,985	128	34
Middle Fork	5,058	301	186,416	1,225	451
North Fork	5,196	269	92,644	1,184	40
South Fork	6,247	7,416	159,209	1,195	161
Total Acres	35,320	9,318	604,827	9,067	2,620

source: analysis of 1979 USGS LULC data

 

 

Table 7: Acres by Land Use and Land Cover Class
Land Use		Acres	% of Total
Forestland		—	91.5%
Evergreen Forest Land		604,827	-
Agricultural Land		—	5.3%
	Cropland and Pasture	34,742	-
Other Agricultural Land	578	-
Rangeland		—	1.4%
	Herbaceous Rangeland	1,136	-
	Shrub and Brush Rangeland	55	-
	Mixed Rangeland	8,127	-
Urban and Built-up Land		—	1.4%
	Residential	6,156	-
	Industrial	789	-
	Commercial and Service	953	-
	Mixed Urban or Built-up	521	-
	Other Urban or Built-up	567	-
	Transportation	81	-
Water		—	0.2%
	Lakes	12	-
	Reservoirs	17	-
	Streams and Canals	1,036	-
Wetland		—	0.1%
	Non-forested Wetland	339	-
Barren Land		—	0.1%
	Strip Mines	575	-
	Transitional Areas	31	-
	Sandy Areas other than Beaches	267	-
Undefined		—	0.0%
	Area Undefined by Coding	4	-
	Total	660,813	-

source: analysis of 1979 USGS LULC data

 

Mining

The Land Use and Land Cover map also indicates the locations of mining sites by type. Mine location data is based on the Mineral Information Layer for Oregon Counties (MILOC) database from the Department of Geology and Mineral Industries (DOGAMI) (Gray, 1994). Although mine locations are indicated, the level of activity is not. Many of the mining sites shown may not be active.

 

Vegetation

The Vegetative Cover Types and Precipitation Zones map shows large-scale vegetation patterns within the Coquille Basin. The vegetation data used in this map is based on data developed by the Oregon GAP Analysis Program, a cooperative effort between the Oregon Fish and Wildlife Service the Oregon Natural Heritage Program and the Idaho Cooperative Fish and Wildlife Research Unit (Kagan and Caicco, 1992). Actual vegetation was mapped as vegetation complexes or groups of vegetation types through visual interpretation of 1988 satellite imagery. Landsat Multi-Spectral Scanner (MSS) false-color infrared positive prints were visually photo-interpreted at a scale of 1:250,000 to identify boundaries of different vegetation cover types. The nominal minimum mapping unit is 320 acres, and the average polygon size for the statewide coverage is 8,141 acres. The median polygon size is somewhat smaller, on the order of a few thousand acres. No independent assessment is available to verify the accuracy of this data.

Table 8: Acres by Vegetation Cover Type based on GAP Analysis Data by Subdivision
Cover Type	Coquille	East Fork	Middle Fork	North Fork	South Fork	Total
Bigleaf Maple-Red Alder-Douglas Fir Forests	10,336	35,442	66,933	52,848	3,374	168,934
Brushfields — Recent Clearcuts and Fires	3,463	—	14,802	7,039	4,356	29,659
Douglas Fir Forests	8,612	49,830	94,358	35,958	61,045	249,804
Oregon White Oak-California Oak Woodland	—	—	448	—	19,801	20,249
Oregon White Oak-Douglas Fir Woodlands	—	—	6,363	—	—	6,363
Rural Pasture with Remnant Bottomlands	20,852	—	330	3,349	4,474	29,005
Sitka Spruce-Western Hemlock Forest	63,824	—	—	—	27,549	91,374
Shoreline Communities	550	—	—	—	—	550
Urban and Industrial Areas	—	—	—	154	204	358
Tufted Hairgrass Meadows	—	—	4,827	—	—	4,827
White Fir-Douglas Fir-Incense Cedar Forests	—	—	5,040	—	53,414	58,454
Total	107,914	85,273	193,101	99,349	174,217	659,853

Source: 1988 GAP vegetation data

The Coquille subbasin is dominated by a variety of forest complexes. The Douglas fir type is the most common, covering approximately 38 percent of the entire subbasin. Sitka Spruce and Western Hemlock Forests are prevalent along the lower and western portions of the subbasin and make up nearly 60 percent of the lower Coquille subdivision. Over 65 percent of the South Fork subdivision in the southern portion of the subbasin is comprised of Douglas fir and a complex of White Fir, Douglas Fir and Incense Cedar. The Bigleaf Maple — Red Alder — Douglas Fir complex covers approximately 25 percent of the Coquille subbasin, but this vegetation type is most prevalent in the East Fork and North Fork subdivisions where it covers 42 percent and 53 percent of the total area, respectively.

The GAP data were used in conjunction with the ownership data to determine the general pattern of vegetation by owner type. Over 78 percent of the White Fir, Douglas Fir and Incense Cedar complex in the entire Coquille subbasin is found in the Siskiyou National Forest. Most of the Sitka Spruce and Western Hemlock Forest type is on private non-industrial (49 percent) and industrial (44 percent) ownerships. Forty four percent of the Douglas fir type is in private industrial ownerships and another 32 percent is on federal lands managed by the BLM. The brushfields and recent clearcuts and fires in the Coquille are found primarily on private industrial (56 percent) and private non-industrial (24 percent) lands. Thirty-seven percent of the Bigleaf Maple — Red Alder — Douglas Fir complex occurs on land managed by the BLM, 35 percent on private industrial and another 27 percent on non-industrial ownerships.

Table 9: Acres by Vegetation Cover Type based on GAP Analysis Data
Vegetation Cover Type	Acres	%
Bigleaf Maple-Red Alder-Douglas Fir Forests	168,934	25.6%
Oregon White Oak-California Oak Woodland	20,249	3.1%
Oregon White Oak-Douglas Fir Woodlands	6,363	1.0%
Sitka Spruce-Western Hemlock Forest	91,374	13.8%
Douglas Fir Forests	249,804	37.9%
White Fir-Douglas Fir-Incense Cedar Forests	58,454	8.9%
Brushfields — Recent Clearcuts and Fires	29,659	4.5%
Shoreline Communities	550	0.1%
Tufted Hairgrass Meadows	4,827	0.7%
Rural Pasture with Remnant Bottomlands	29,005	4.4%
Urban and Industrial Areas	358	0.1%
Undefined	276	0.0%
Total	659,853	100%

Source: 1988 GAP vegetation data

 

Forest cover seral stage

The Forest Seral Stage map shows three forest cover seral stage classes — late seral, mid seral, and early seral — along with non-forested, other forest, and water. The data was developed from 1988 Landsat Thematic Mapper (TM) satellite imagery for the Oregon Department of Forestry. The six classes are defined as follows:

Late seral stage: greater than 70% tree crown closure with greater than 10% of total crown closure in trees 21 inches diameter at breast height (dbh) or more, and not more than 75% of total crown closure in hardwoods.

Mid seral stage: greater than 70% tree crown closure with less than 10% of total crown closure in trees 21 inches diameter dbh or more, and not more than 75% of total crown closure in hardwoods.

Early seral stage: greater than 10% and less than 70% tree crown closure and not more than 75% of total crown closure in hardwoods.

Other: less than 10% crown closure of conifers and/or greater than 75% of total crown closure in hardwoods.

Water: open water.

Non-forested: not forestland as determined by 1:250,000 scale USGS landuse coverage.

Table 10 shows acres by seral stage class within each subdivision. Thirty-two percent of the Coquille subbasin is classified as mid seral stage. Another 22 percent is classified as other forest due most likely to a predominance of hardwoods. The lower Coquille subdivision has the lowest percentage of late and mid seral class. One third of the lower Coquille is classed in the other forest category, and another third is non-forest. The Middle Fork subdivision has the highest percentage (60%) of late and mid seral stage forest.

[click on map for larger version]

 

Table 10: Acres of Seral Stage by Subdivision
Seral Stage	Coquille	East Fork	Middle Fork	North Fork	South Fork	Total
Late Seral	2,454	19,522	41,107	13,068	27,414	103,565
Mid Seral	22,428	31,820	65,413	39,261	51,862	210,785
Early Seral	8,396	6,895	16,737	7,849	36,723	76,600
Other Forest	36,768	17,936	39,216	23,533	29,565	147,018
Water	392	0	10	5	5	412
Non-forest	36,977	8,826	30,016	15,255	27,525	118,599
Total Acres	107,415	84,998	192,499	98,971	173,095	656,978

Source: 1988 25 meters seral stage data, ODF

Merging the ownership data with seral stage data highlights variation in the pattern of ownership relative to general forest condition. Figure 12 indicates the distribution of seral class by ownership type. The BLM, which manages 23 percent of the land within the Coquille subbasin, controls 46 percent of the late seral stage class. Private industrial ownerships, which account for 36 percent of the entire subbasin, control forty-six percent of the mid seral stage class lands.

Figure 12: Acres by Seral Stage and Owner Class

Source: analysis of 1988 25 meter seral stage data and 1991 Western Oregon Industrial Forest Ownership data (OSU)

Table 11: Cover Type as Percentage of total Ownership Type*
Cover Type	BLM	PI	PNI	USFS
Bigleaf Maple-Red Alder-Douglas Fir Forests	41.31%	24.50%	23.83%	—
Brushfields — Recent Clearcuts and Fires	3.23%	6.95%	3.71%	—
Douglas Fir Forests	51.92%	45.72%	21.55%	27.53%
Oregon White Oak-California Oak Woodland	0.08%	1.17%	8.92%	—
Oregon White Oak-Douglas Fir Woodlands	1.41%	0.35%	1.73%	—
Rural Pasture with Remnant Bottomlands	—	0.62%	14.07%	—
Shoreline Communities	—	0.02%	0.04%	—
Sitka Spruce-Western Hemlock Forest	0.67%	16.96%	22.98%	—
Tufted Hairgrass Meadows	0.14%	0.01%	2.36%	—
Undefined	—	0.00%	0.10%	—
Urban and Industrial Areas	—	—	0.18%	—
White Fir-Douglas Fir-Incense Cedar Forests	1.23%	3.69%	0.53%	72.47%

Source: analysis of 1988 GAP vegetation data and 1991 OSU Western Oregon Industrial Forest Ownership Coverage.
* BLM = Bureau of Land Management; PI = Private Industrial; PNI = Private Non-industrial; USFS =US Forest Service.

The distribution of land by seral stage class varies considerably within ownership groups. National forest land managed by the USFS is nearly evenly divided among late, mid and early seral classes. One third of BLM land is classified as late and another third as mid seral stage. Twenty-eight percent, however, is in either the other seral or non-forest class. Forty-one percent of private industrial land is in the mid seral stage and 25 percent is in the other seral class. The remaining third of private industrial land is evenly distributed among the late seral, early seral and non-forest classes. Approximately two thirds of all private non-industrial lands are in other seral or non-forest classes. Twenty percent of non-industrial lands are in the mid seral stage class.

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