For many in my general age group the term “Ball and Chain” immediately conjures images of the late, great Janis Joplin belting out the Big Mama Thornton tune of that title in 1967, commemorated in D. A. Pennebaker’s documentary film, Monterey Pop. Who knew that in the following decade, the term would take on a whole different meaning, applied by California’s Division of Forestry (CDF) to such tasks as “Pre-burn treatment of oaks with the ball and chain” (Brown 1973)?
While that particular report is not available online today, we learn from the Brushland Range Improvement 1973 Report (CDF 1974) that there was “considerable excitement among ranchers about the ‘Ball and Chain’ ”, shown in that report’s Figure 6 doing its destruction on Monterey County slopes (left). As is clear from the first title, the ball and chain action was only preparatory to prescription burns and this report offers, in its Table 1, a “summary of controlled burn statistics, 1973”, in various California districts and counties, primarily northern and central California, although 30 acres were aerial sprayed with herbicide in Bautista Canyon, Riverside County, with plans to treat remaining brush and sprouts by mechanical means or burning.
Before we get too far into this discussion, I want to alert the reader to two new pages in the Alternate Paradigms section that complement this post and vice-versa – all are interrelated. California “Grasslands” vs. Altered State(s) offers the bigger picture of the artificiality of what most folks think of as our state’s “grasslands”. “Water Yield” vs Baseflow Augmentation, expands on the snapshot offered in the Rainfall to Groundwater Executive Summary, including going back in time for yet another wee history lesson. Now, jumping back to the 1970s . . .
CDF (1974) Table 2 offers a “summary of activity in controlled burning and reseeding for range improvement, 1946-1973 inclusive”. The grand totals during that period were: “2,533,904 acres burned, less 780,363 acres re-burned, for 1,940,172 net acres burned, with a total 191,406 excess acres burned by escapes. In other words, more than 2 million acres burned for range improvement over a 27-year period. All officially permitted by CDF, discounting the escapes.
For a Division of Forestry, our state agency sure eliminated a lot of woody plants during those years. One might think those post-WWII years continued the momentum of wartime defensive assault, just applying it to native woody plants instead of foreign enemies. The irony of the “Forestry” moniker is not lost on this botanist/ arborist. But this was all for the noble cause of “rangeland improvement”, remember. At least most was. The cover photo (right), which appears at the end of the online pdf, depicts operations for game management.
Not much detail is offered on mechanical treatment prior to burning in the earlier “Activity in Range Improvement: CDF Annual Report” (CDF 1962), other than to state it was done in most cases. A still earlier one-page report, “Data on D-7 Tractor Operations” (CDF 1949) notes the general process, as well as the data that 3 hours per acre were required for felling knobcone pines with the D-7, along with time needed for other tasks in Mendocino National Forest. Perhaps that was also the equipment used through 1961.
The 1962 report does include a list of species seeded, in contrast with the 1974 report, which notes seeding but not which species were seeded. Other details in that report are that in the North Coast District “there were 25 burns conducted exclusively for game habitat improvement. Fourteen burns were conducted for medusa-head (Elymus caput-medusae) control . . .” (CDF 1962). Costs for helicopter application of herbicide on brushland are given for the Central Sierra District. For the San Joaquin District one Madera County rancher provided costs for pre-burn treatments including:
“Cut surface” treatment on Digger [now referred to as Gray] pines
Killing live oak trees (falling and treating stumps with 2,4-D amine)
Mashing brush and preparing fire lines . . .
Rancher organizations participated in controlled burning activities in Fresno, Madera, Mariposa and Tulare counties (CDF 1962)
Cooperation of rancher organizations in controlled burns is noted for San Luis Obispo and Santa Barbara Counties on the Central Coast District, while “chemical control of brush sprouts and seedlings by helicopter highlighted 1961 activities at the Ranchita Range Study near San Luis Obispo. . . .” (CDF 1962). In the Southern California District, “nearly 900 acres of brush were cleared for range improvement by mechanical means in San Diego County” (CDF 1962).
Stepping back in time to near the beginning of these documented “range improvement” initiatives, Aaron Gordon and Arthur Sampson wrote in 1939,
In half a century of grazing by domestic livestock conspicuous changes have taken place in the plant population of this vast grass-woodland area. In many instances the carrying capacity has declined sharply, and a portion of the top soil has been removed. Evidence points to the fact that a substantial proportion of the original perennial graminaceous species has been replaced by annual exotic grasses and other herbs of southern Europe . . . So conspicuous has been this transformation that future grazing management plans must be focused largely upon this relatively early-maturing vegetation.
(Gordon and Sampson 1939)
And so it was, and remains today. Rangeland managers continue to (attempt to, at least) make the best of difficult situations, milking what they can of the nonnative annual grasses that now effectively dominate the greatest proportion of California rangelands – typically viewing this as the “natural” condition of rangelands, forgetting that their forebears are the ones that rendered them thus. Naturally, cattle must be shipped to out of state feedlots for finishing as year-round grazing is not an option for most ranchers, given the predominance of exotic annual grasses that are done at the end of each rainy season.
Cover image from Composition of common California foothill plants as a factor in range management (Gordon and Sampson 1939), presumably San Joaquin Experimental Station
Gordon and Sampson conducted research on field and nursery sample plots at the San Joaquin Experimental Station, providing insight into species mosaics characteristic of the place at that time. Observing that the chemical composition of rangeland plant species changes over the increasingly shorter season of productivity, they posed some questions for range management, including the following:
Should the management of a range be so directed as to restore and maintain as nearly as possible the original plant cover, linked, as it is, with its characteristic soil type, or may there be a less planned utilization of the forage, resulting in the vegetation being naturally transformed into a single plant association, such as a purely herbaceous stand, or into a brush cover?
(Gordon and Sampson 1939)
Among other insights on chemical constituents of different plant groupings they noted that
The crude protein in the foliage of the deciduous shrubs and trees declines in an orderly way from the earliest appearance of the leaves to their maturity. The protein levels in this group are the highest of the various groups studied. In the deciduous half-shrubs and nondeciduous shrubs, the protein levels change relatively little, and are the lowest of the six groups. . . . A diversified plant cover is preferable for stabilization of nutritive forage values to that of a single plant type. (Gordon and Sampson 1939, emphases added)
However, such insights may have come too late, as ten years later we learn:
In 1932, at the urgent request of the livestock interests of the state, the Dean of College of Agriculture appointed within the University [of California] a Committee on Range Management, charged with the responsibility of studying ways and means of improving brush ranges. Investigations were started and some information was obtained on the behavior of an area after the brush was burned. More important, investigations were started on the controversial problems of run-off and erosion, which are providing invaluable information. In 1945 this Committee was reorganized, as the Committee on Range Land Utilization, with this change: it became primarily a policy-forming committee, charged mainly with the responsibility of recommending and sponsoring a sound research program. This Committee is still active and is composed of representatives from the various divisions of the College of Agriculture, and the School of Forestry. . . . (Madson 1949, emphasis added)
More from other authors in that same 1949 document:
The California State Division of Forestry is authorized to regulate the use of fire on lands under its jurisdiction and to cooperate with those who wish to use fire as a legitimate tool in the management of their property. . . .
. . . Controlled burning is being practiced by many different industries and individuals in the state. Hunting clubs “spot” burn on their land in the winter and early spring months to improve hunting. The recreation industry uses fire for hazard reduction and debris removal. The timber industry burns to remove slash and mill waste. The livestock industry burns to increase grazing capacity. The farmer uses fire to aid debris removal and hazard reduction. Each year approximately 20,000 permits are issued by the State Division of Forestry for use of fire in a legal manner.
From the beginning of civilization man has used fire as a cultural tool in his attempt to develop land. In many cases he continues to use fire through habit and tradition, after technological advances have furnished him with more adequate tools to accomplish the desired results.
Fire has been used extensively in California by the livestock industry in order to extend the boundaries of available grazing land. This practice was generally accepted when grazing, mining, and harvesting of virgin timber were the primary uses of the land involved. Recently, however, with an increasing demand for water, second-growth timber, and recreation sites, there has developed a recognition that the indiscriminate use of fire can be very detrimental to other interests. As forage, water, and timber are our most valuable renewable resources, conflicts in management practices evident among these industries must be weighed carefully. . . . The State Division of Forestry is authorized by legislation to issue the landowner a permit to burn brush-covered lands for the purpose of range improvement. . . . (Fenner and Nelson 1949)
Now we better understand how the Division of Forestry got involved in the destruction of trees and woody shrubs in California. And for the record, all the CDF reports were about permitted burns. But do note that this program of burning for “rangeland improvement” was not considered anything new to the state – it had been going on since at least the beginning of statehood, and, as noted in blog post 4, Think Outside the Basin, along with the page California “Grasslands” vs. Altered State(s), such burning only continued similar practices by Native Americans in prehistorical times.
As for the ball and chain method, some citations (Gilbert and Schmidt 1970, Brown 1973, Adams 1976) have not been preserved for posterity online. But Roby and Green (1976), U.S. Forest Service, have us covered, also demonstrating both state and federal agencies’ participation. ’Turns out, there was a WWII legacy.
Mechanical brush treatment with anchor chains between two tractors, or with a bulldozer or brush rake, is not usually feasible on steep side slopes. The “ball and chain” technique of crushing brush was developed to fill this gap.
The equipment usually used for a ball-and-chain operation is a light-to-heavy anchor chain and a steel marine net float (buoy), 5 feet in diameter. The buoys, like the chains, are available through Navy surplus outlets. . . .
The empty buoys weigh about 600 pounds each. Armor plated and filled with water, they weigh about 5,000 pounds each. When filled with fine gravel, and then with water, they weigh about 6,700 pounds. Some balls have been filled with gravel or sand alone, and a few have been filled with concrete. A buoy filled with gravel, sand, or both, is more difficult to fill and to empty for transporting, but leakage is avoided. When filled with concrete, the buoys weigh approximately 9,000 to 10,000 pounds depending on the density, but of course they cannot be emptied for transportation. . . .
(Roby and Green 1976)
Chain lengths range from 60 to 180 feet, with recommended chain weights for each length class. Roby and Green’s (1976) Agriculture Handbook No. 487 describes other chaining methods, tractor specifications and several chain modification methods using steel crossbars, along with safety cautions, cost details and photos of equipment being customized and in action on brushy slopes.
John Rusk from Berkeley, CA, United States of America, H20140529-2666—Rhamnus ilicifolia—RPBG (14376384343), CC BY 2.0
Click images to enlarge
As mentioned in some of the above, mechanical methods weren’t the only means used for clearing rangelands of those pesky woody plants. As Graham, USFS Range Conservationist (1958) reports, [note that pages 1 and 2, 3 and 4, are reversed in the downloadable pdf] the herbicides 2,4-D; 2,4,5-T; and a 50/50 mixture of both, recommended by Dr. Oliver Leonard, UC Botany Department, were tested at San Joaquin Experimental Range on the evergreen interior live oak (Quercus wislizenii) and redberry (Rhamnus illicifolia), also on deciduous blue oak (Quercus douglasii) – so much for the recommendations of Gordon and Sampson (1939), noted above. Three consecutive annual treatments were recommended for effective removal of these woody species.
These same herbicides were tested on stump sprouts of madrone (Arbutus menziesii) and tanoak (Notholithocarpus densiflorus) by Kay and colleagues (1961) in Garberville. In this experiment, daubing a mixture of the herbicide on cut stumps was found more effective and economical than spraying.
Honestly, it struck me that this experiment was reported in the journal Weeds, given that I find madrone among the more beautiful of hardwood species due to its smooth reddish bark that often resembles human skin. And it also produces quite tasty, as well as pretty, white flowers. Furthermore, it has long been considered difficult to establish plantings of this species when/ where desired. While tanoak may not be as attractive to most folks, it was long valued for processing (tanning) animal leathers and just may be on the decline due to it’s susceptibility to Sudden Oak Death disease. Certainly many trees of this species died along the Big Sur coast as the disease took hold early this millennium, eliciting at least local concern. So the thought of them considered “weeds” seems at odds with some current perspectives. But the authors explain that these two species,
. . . are often considered undesirable along the Pacific Coast. These weed trees are removed to increase forage production; to remove competitors of more valuable timber trees, especially Douglas fir (Pseudotsuga menzesii . . .); or to obtain firewood or charcoal. Tanoak is occasionally cut for tanbark harvest. Control of stump sprouting following cutting would be desirable.
(Kay and colleagues 1961)
The cover photo for the “Brushland Range Improvement Annual Report 1974-1977” (CDF 1978), also on the final page of the online pdf, is shown at right.
Some may recall that the final two years of the period encompassed by that report marked a severe statewide drought. So the great headwind accomplished earlier by the agency, now “Department” of Forestry, on “rangeland improvement” through burning began to die due to a combination of natural causes and new regulations on air quality management.
“Twenty years after close of study good forage production continues on Spring Dell Study in San Benito County. Good brush control by crushing, burning, and herbicide treatment produced lasting benefits. Good grazing management was an important factor in preventing another invasion by brush.” (CDF 1978)
The severe drought conditions, restrictions on burning permits because of high hazard, a lack of grass cover to carry fire, and the need to save what grass was available for cattle feed resulted in a large reduction in control burning activity the last two years. . . .
To a much greater extent, the use of fire is becoming just one phase of the land clearing process rather than the total remedy in converting brush-covered land to productive rangeland. Mechanical and chemical pre-burn treatments on brush-covered lands were applied as important steps in rangeland improvement.
However, in the Regional Activity section of that report, the last line of the North Coast Region reads, “ Fire will probably continue to be employed as a land clearance tool.”
View of oak woodland zone from General’s Highway, facing northeast, Three Rivers, Tulare County, CA (1993) Photographer: Brian C. Grogan, Historic American Buildings Survey (HABS) Team
Click images to enlarge
In the San Joaquin Region mechanical pre-burn treatment continued to be the pattern.
Crushing the brush with bulldozers, piling, and falling oaks with chainsaws were the methods used. Follow-up treatment on brush sprouts with chemicals continued. A number of wood cutting operators continued to use stump treatment with chemicals to reduce sprouting following cutting.
Brushland range improvement activity in the Central Coast Region took a significant drop . . . a reflection of the drought during this period. . . . A total of 50,831 acres was burned . . . about equally divided between north and south halves of the region. . . . Air pollution “no burn” days limited some otherwise good burning days.
The Wartham Canyon Range Study, located in Western Fresno County, was established in 1969 for demonstrating conversion of chaparral cover to grass for livestock production. Among its objectives is to demonstrate the possibility of burning during periods of the year when fire hazard and the danger of air pollution are low.
The entire area has been spring burned in two parts (April 1971 and April 1972). Both parts were sprayed for control of brush seedlings and sprouts during May, 1972 and 1973.
The entire area was seeded with Blando brome and wimmera ryegrass at ten pounds of mixture per acre. Two strips of Luna wheatgrass and trigo wheatgrass were overseeded at a rate of 15 pounds per acre of each.
The project area has remained “open” without further treatment. Data is being collected annually.
Regarding the Bautista Canyon study, this report notes that it was a cooperative study with UC Riverside and the Pacific Southwest Forest and Range Experiment Station. Not explicitly mentioned earlier we now learn that:
One of the primary objectives of the study was to trace residues from the several herbicides being used in the study, Plans are now being formulated to clear the study are of the dead brush and sprouts by various mechanical means and/or fire.
Symposium on Ecology, Management and Utilization of California Oaks (1979) Claremont, CA
But the paradigm was shifting. As the momentum of public agency efforts to facilitate removal of woody vegetation from California rangelands began to wain, along came a new appreciation of oak woodlands. This was especially expressed in the first of many symposia on oak woodlands, convened in June 1979 on the Scripps College campus in Claremont and sponsored by the Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, and the Society of American Foresters. Since that document is currently available online for anyone to download, just a few highlights are noted here. Chairman and Technical Coordinator Timothy R. Plumb observed in the Preface to the published proceedings (Plumb 1980),
Historical records show that the beauty and value of the arborescent oaks were readily apparent to the early settlers, but during the last 200 years, probably more effort has been spent to remove and kill oaks than to grow and manage them. Efforts by concerned individuals and public resource organizations to manage oaks have generally been ineffective.
Because of the “poor” stem form and the relatively slow growth of most oak trees, professional foresters have generally concentrated their efforts on managing other trees, mainly conifers. Recently, however, broad-scale interest in oaks has developed. The public has become aware of the limitations of our natural resources. The potential of the oak woodlands in meeting energy shortages and wildlife needs, as well as the great immediate value of these woodlands to recreation, are now being recognized. This recognition, and the intense concern now felt about the urbanization of California’s woodlands, have contributed to the success of the symposium.
The Rainfall to Groundwater Executive Summary mentions the use of oaks for charcoal, citing (Mensing 2006). Randall Rossi’s (1980) overview of cultural impacts on oak woodlands at the 1979 symposium offers a fairly detailed description of the history of using various oak species for charcoal making around the state, along with use or removal of oaks for many other reasons dating well back before the “mid-century modern” approaches detailed above. As for “rangeland improvement” Rossi notes,
It was not until 1973 that the practice of clearing oaks from rangeland was seriously questioned. Holland (1973) working in oak savanna sites near Madera, in the Temblor Range, in Kern County, and at Hastings Reservation in Carmel Valley, showed that forage production and nutritional quality are greater under the blue oaks than between them. Further, the forage has greater nutritional value and remains greener into the dry season; the trees also modify the micro-climate and improve range land soils. Further details of this blue oak canopy effect and its implications for oak clearing appear in Holland (1980) and Holland and Morton (1980). Where oaks form a nearly closed canopy (120-200 trees per acre) tree removal has reportedly not affected forage value in some areas (Murphy and Crampton 1964) and enhanced it in others (Johnson et al . 1959).
The Holland (1980) and Holland and Morton (1980) papers referred to above are included in these proceedings and the interested reader is encouraged to review them in their entirety. Offering the lingering opposing viewpoint was a pair of the “old guard” (Kay and Leonard 1980) still somehow providing results showing improved forage production after removal of oaks, albeit in northern California rangelands, and they did acknowledge an increase in soil bulk density during their study.
Menke and Fry (1980) summarize the ongoing use of oaks for fuelwood and offer a detailed study showing the importance of not only acorns to deer and sheep, but also the significance of protein from lichens associated with the oak trees at UC’s Hopland Field Station in Mendocino County (among locations where trees were removed for experiments). Finally, with respect to this overview, Duncan and Clawson (1980) offer ratings of nine different oak species as browse for cattle, horses, sheep, goats and deer, along with a chemical analysis of the acorns of five different species and they note the lack of regeneration of blue oaks at San Joaquin Experimental Range despite exclusion of grazing.
In conclusion, we can be somewhat content that this milestone 1979 symposium on oak woodlands represented the turn of the tide with respect to the wholesale removal of oak woodlands for “range improvement”. To this date, conversion of oak woodlands to vineyards and urbanization remains a concern. Type conversion of native chaparral and scrub vegetation to nonnative annual grasses through prescription burning and anthropogenic wildfire remains an ongoing issue, as touched upon in California “Grasslands” vs. Altered State(s).
Problems of poor regeneration of blue and valley oaks on woodlands and especially savannas with understories dominated by nonnative annual grasses remains an issue to date, perhaps to be addressed in some future blog post.
But the biggest point to understand here is that the foregoing offers a summary glimpse of only what is documented as having transpired over a mere few decades of the 20th century to convert California’s oak woodlands, chaparral and scrub to the vast acreages of nonnative annual grasslands we see today. Consider what happened over the decades and centuries before, that has only been alluded to, not formally documented.
Cultivation of crops in a natural oak forest in the Salinas Valley (1914), central California. Old Quercus lobata (valley oak) trees in Monterey County.
For example, as noted in blog post 4, Think Outside the Basin, dryland farming took a toll on many upland sites, including oak woodlands. Please see the adjacent photos from Popular Science Monthly Volume 85. It seems likely the trees in the photo at left, at least, are no longer with us.
Those who wish to transform the vast rangeland acreages into carbon farms through widespread application of organic farming methods are missing the point that there are far better ways to increase the carbon sequestration potential of these vast rangelands – by restoring native woody species, along with their soil ecosystems, for whom these are their rightful homelands. If a rancher’s only objective is better grass, organic farming may be fine for them. But if they wish to be supported in their efforts by payment for watershed/ catchment services (see What’s in it for ranchers?) they need to do better.
For example, a few excerpts from the relatively recent California Agriculture report, “Research connects soil hydrology and stream water chemistry in California oak woodlands” (O’Geen and colleagues 2010) are included on the new Alternate Paradigms page, “Water Yield” vs Baseflow Augmentation, regarding watershed/ catchment functions. But the following is particularly germane here:
. . . Given the organic matter enrichment in soils and oak vegetation, there is considerable potential for carbon sequestration (about 89 tons per acre) associated with the conversion of grasslands to oak woodlands. To ensure long-term carbon sequestration, oak trees must be protected. Organic carbon and many of the enhanced soil properties are lost within 20 to 30 years following an oak’s removal (Dahlgren et al. 2003).
(O’Geen and colleagues 2010)
We can restore the watershed detention functions of these lands, as noted in numerous other places on this site, to support payment for watershed/ catchment services. Rather than a single-issue approach (e.g., solely carbon sequestration), Rainfall to Groundwater proposes a holistic a.k.a. whole systems ecological restoration scenario that will support both those, along with other ecosystem functions, and is doubtless more sustainable over the long term than the proposed widespread application of organic farming methods, much as I approve of and practice those methods myself on smaller scales.
While the organic farming approach may help hold more water in the soil, it won’t contribute to groundwater recharge, as proposed on this site, in the absence of the deep woody root systems and their soil ecological associates that have been removed from these lands through long-term and ongoing human disturbance.
There is plenty of literature support for this approach but its true viability for groundwater recharge will only be proven by Groundwater Sustainability Agencies’ (GSA’s) site-specific monitoring, as called for by the Sustainable Groundwater Management Act (SGMA), but reaching beyond the narrow confines that apply that legislation (reductionistically) solely to groundwater basins.
Thankfully, the required water budgets are the way to incorporate such watershed relationships into Groundwater Sustainability Plans. When GSAs demonstrate through strategic monitoring that watershed/ catchment restoration actions have increased natural recharge, such increases should become available to them in the form of acceptable corresponding withdrawals. The Rainfall to Groundwater Learn, Apply program offers singular guidance to help GSAs accomplish such objectives, especially since they can’t look to California’s Department of Water Resources (DWR) for this approach.
The California Healthy Soils Program may actually support such holistic approaches given that the US Natural Resource Conservation Service’s Silvopasture Conservation Practice Standard Code 381 is among the practices acceptable to the program, according to the downloadable Guihua (Grace) Chen, Ph.D. presentation on the program. Learn more at Carbon Farming & Watershed Restoration.
I only learned through the April 18, 2018 New York Times Magazine article, “Can Dirt Save the Earth?” (Velasquez-Manoff 2018) that the impetus for the Healthy Soils Program was apparently its vociferous championship to the state legislature by one determined advocate.
Can Rainfall to Groundwater foster some equally vociferous champions, given that it aspires to support at least as many stakeholders in their objectives? That is, ranchers and GSAs specifically, among the rest of us who will benefit from the proposed ecohydrological as well as carbon sequestration, among other ecosystem services.
Alas, DWR seems less open to holistic approaches. DWR has apparently barricaded its fortress to any input coming from me, so I wonder whether Rainfall to Groundwater can generate some vociferous champions to insist that DWR broaden their horizons from 20th century engineered-diversion-of-surface-waters-to-engineered-recharge-structures toward holistic approaches to enhancing natural groundwater recharge where watershed/ catchment functions have been degraded through historic and prehistoric human impacts, including those described above, as well as on California “Grasslands” vs. Altered State(s)?
Hey, this may be slightly off-topic but related and I want to give a timely shout out for a recent 46 minute film I recommend to see what some Central Coast folks are doing about groundwater recharge in the context of our changing climate. The video itself is The Dirt on Climate Change and you can view it, along with more info, from the page Climate Change Hits Home.
I linked one of Producer Lois Robin’s earlier films, Stuck in the Mud: the Pajaro River in Peril on the Plants in an Ecohydrology Context page and should have noted it in the Rainfall to Groundwater Executive Summary. Download that approximately 30-minute video to see the aftermath of the misguided decimation of riparian vegetation there following the 1995 floods, and learn more about the state of that Central Coast river that hosts steelhead, supports family farms and much more.
But The Dirt on Climate Change offers more encouraging news. It’s a feel-good, inspirational film.
Adams, T. E. 1976. Brush Management-The Ball and Chain. California Division of Agricultural Sciences Leaflet 2920, Berkeley, CA
Brown, R. D. 1973. Pre-burn treatment of oaks with the ball and chain. Range Improvement Studies, California Division of Forestry, Sacramento, CA
California Division of Forestry (CDF). 1949. Data on D-7 Tractor Operations. California Division of Forestry, Sacramento, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157125&p=VLYWCC
California Division of Forestry (CDF). 1962. Activity in Range Improvement: CDF Annual Report. California Department of Forestry, Sacramento, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157871&p=ZHGFRP
California Division of Forestry (CDF). 1974. Brushland Range Improvement 1973 Report. California Division of Forestry, Sacramento, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157887&p=UHGJJX
California Department of Forestry (CDF). 1978. Brushland Range Improvement Annual Report 1974-1977. California Department of Forestry, Sacramento, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157895&p=IGPSAY
Dahlgren, R. A., W. R. Horwath, K. W. Tate, and T. J. Camping. 2003. Blue oak enhance soil quality in California oak woodlands. California Agriculture 57:47. http://danr.ucop.edu/calag
Duncan, D. A. and W. J. Clawson. 1980. Livestock utilization of California’s oak woodlands. Pages 306- 313 in Proceedings of the Symposium on the Ecology, Management and Utilization of California Oaks, June 26-28, 1979, Claremont, CA. USDA Forest Service Pacific Southwest Forest and Range Experiment Station General Technical Report PSW-44, Berkeley, CA. http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.224.1308
Fenner, R. and D. Nelson. 1949. The role of the State Division of Forestry in the range improvement program. Pages 4-7 in M. D. Miller, editor. What We Know About Brushland Management in California UC Agricultural Extension Service, Berkeley, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157126&p=VHZYUD
Gilbert, R. and J. Schmidt. 1970. Ball and chain brush crushing. Range Improvement Studies, California Division of Forestry, Sacramento, CA.
Gordon, A. and A. W. Sampson. 1939. Composition of common California foothill plants as a factor in range management. UC College of Agriculture Agricultural Experiment Station Bulletin 627, Berkeley, CA. https://ucanr.edu/repository/fileaccess.cfm?article=156809&p=SOSYEV
Graham, C. A. 1958. Killing brush sprouts on open woodland range in California. USDA Forest Service Forest Research Notes No. 136. Berkeley, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157159&p=SPCOWB
Holland, V. L. 1980. Effect of blue oak on rangeland forage production in central California. Pages 314-318 in Proceedings of the Symposium on the Ecology, Management and Utilization of California Oaks, June 26-28, 1979, Claremont, CA. USDA Forest Service Pacific Southwest Forest and Range Experiment Station General Technical Report PSW-44, Berkeley, CA. http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.224.1308
Holland, V. L. and J. Morton. 1980. Effect of blue oak on nutritional quality of rangeland forage in Central California1. Pages 319-322 in Proceedings of the Symposium on the Ecology, Management and Utilization of California Oaks, June 26-28, 1979, Claremont, CA. USDA Forest Service Pacific Southwest Forest and Range Experiment Station General Technical Report PSW-44, Berkeley, CA. http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.224.1308
Kay, B. L., O. A. Leonard, and J. E. Street. 1961. Control of madrone and tanoak stump sprouting. Weeds 9:369-373. https://ucanr.edu/repository/fileaccess.cfm?article=157189&p=GJDZUD
Kay, B. L. and O. A. Leonard. 1980. Effect of blue oak removal on herbaceous forage production in the north Sierra foothills1. Pages 323-328 [pdf 328-333] in Proceedings of the Symposium on the Ecology, Management and Utilization of California Oaks, June 26-28, 1979, Claremont, CA. USDA Forest Service Pacific Southwest Forest and Range Experiment Station General Technical Report PSW-44, Berkeley, CA. http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.224.1308
Madson, E. A. 1949. Coordinating brush range research. Pages 1-3 in M. D. Miller, editor. What We Know About Brushland Management in California UC Agricultural Extension Service, Berkeley, CA. https://ucanr.edu/repository/fileaccess.cfm?article=157126&p=VHZYUD
Menke, J. W. and M. E. Fry. 1980. Trends in oak utilization-fuelwood, mast production, animal use. Pages 297-305 in Proceedings of the Symposium on the Ecology, Management and Utilization of California Oaks, June 26-28, 1979, Claremont, CA. USDA Forest Service Pacific Southwest Forest and Range Experiment Station General Technical Report PSW-44, Berkeley, CA. http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.224.1308
Mensing, S. 2006. The History of Oak Woodlands in California, Part II: The Native American and Historic Period. The California Geographer 46:1-31. https://www.researchgate.net/publication/232041282_The_History_of_Oak_Woodlands_in_California_Part_II_The_Native_American_and_Historic_Period
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