Appendix 2: Disturbance and Ecological Possibilities
We would like to discuss the possibility that much of the Los Gatos Creek Watershed is in a state of regeneration from major past disturbances. In the late 1800's to early 1900's most of the area owned by SJWC was clear-cut, and some areas remained in agricultural production for several decades. In 1961, much of the upper watershed, including 2600 acres of what is currently SJWC land was burned in the Austrian Gulch Fire. In 1985, almost the entire watershed, including 5145 acres of SJWC land, burned in the Lexington fire (see Map 3).
This discussion has been included to present several hypotheses about the ecological potential of SJWC land. Unfortunately, we have not had the privilege to examine the vegetation on these lands from the ground (except looking in from local roads). However, in many other areas of the Santa Cruz Mountains, including areas adjacent to SJWC land, we have noticed several trends developing after the Lexington Fire. Specifically, certain hardwood dominated areas seem to be taking many years to recover conifer dominance and areas of Arctostaphylos sp. (manzanita) chaparral have been invaded by Douglas-fir saplings. There are many statements within the NTMP application that concur with these ideas (detailed below). This discussion was not meant to be a complete examination of the ecological potential of these lands. Any such effort would require a more extensive literature review and access to the land for ground surveys. However, our base estimates of 'Timberland' do not even consider hardwood-dominated areas outside of the NTMP. To that end, the arguments below are incidental to the finding the SJWC owns 2754 acres of timberland.
We found evidence of Group A timber species on 28% of the "SECONDARY SERIES" zones owned by SJWC (for definition of "SECONDARY SERIES" see Appendix 1). We did not find evidence on Group A timber species on 1239 acres. These areas have been classified as a mix of hardwoods, such as Tanoak, Pacific Madrone, White Alder, and California Bay Laurel (Bay Laurel is the dominant species for 76% of these zones). Of these hardwood areas, 96% were burned in the Lexington Fire and 53% were burned in the Austrian Gulch Fire. While California Bay Laurel is not a Group B species in the Coast District (it is in the Northern District), most of these areas are classified as a mix of hardwoods, including the Group B species Tanoak, Pacific Madrone, and White Alder. Thus if they had grown Coast Redwood trees in the recorded past, they would count as legal timberland.
The ecological literature is replete with evidence that California Bay Laurel sprouts very quickly after a fire or clear-cut, slowing the re-establishment of conifer species (Howard 1992, Burns and Honkala 1990, McBride et al 1980, Stein 1974). We would hypothesize that the multiplicative effects of a clear-cut in the early 1900's, followed by a 1961 fire, followed by a 1985 fire may have created dense stands dominated by California Bay and other hardwoods in areas where Coast Redwood or Douglas-fir may have dominated in the 19th century. In addition, California Bay is well-known to allelopathically (chemically) inhibit growth of its competitors by secretion or leaching of terpene compounds (Griffin et al 1972, Tinnin et al 1985, Gurevitch et al 2002, unpublished data UCSC). This may also drastically slow the rate of conifer regeneration.
However, Coast Redwood often sprouts from basal lignotubers after an injuring fire or clear-cut. This idea of disturbance-based hardwood dominance is applicable mainly to areas on the margins of dense forest or in areas where the Coast Redwoods and Douglas-fir may not have recovered as quickly from the clear-cut in the early 20th century. For example, the stand dynamics of Coast Redwood are summarized in the review by Sawyer et al 2000 as: "Fire may have favorable or detrimental consequences on the success of redwood, as well as that of associated tree species. Very frequent fires may favor tree species other than redwood....With increased fire and disturbance, redwood trees will have greater mortality, seedling success will decline, and competitors with greater drought resistance and higher light requirements will be more successful."
We did find ample evidence of young, mostly Douglas-fir, coming up on the margins of more dense Redwood or Douglas-fir forest that had been mapped by MROSD as mostly California Bay dominated vegetation types in their survey in 1999 (Supplement 5). A cursory look at USGS aerial photographs over time also provide some evidence of more extensive conifer distribution before the 1985 fire (see images below of the upper watershed above Lake Williams), although a difference in image resolution will make any quantification of this pattern difficult.
The idea of Calfornia Bay slowing the re-establishment of conifer species such as Coast Redwood and Douglas-fir after fires or clear-cuts is well documented. For example, Burns and Honkala 1990 state: "Because of its thin bark, the tree is easily top-killed by fire, but it sprouts rapidly. Dense clumps are often formed on cutover land, which may prevent the establishment of desired conifers."
Howard 1992 explains further: "California bay severely reduces growth of conifer timber seedlings through allelopathic inhibition. The leaves contain water-soluble terpenes which retard root elongation.... Unless controlled, the California bay understory in coniferous forests often becomes dominant or codominant within a few years following clear-cutting of mature timber trees......Top-killed California bay recovers rapidly from fire. Taber and Dasmann reported crown sprouts appearing 4 to 6 weeks after late winter and spring fires in the North Coast Ranges of California…..Reproductive ability is regained quickly; flowers have been noted on first-year sprouts . Seedlings establish from post-fire year 1 until the next fire cycle. In the redwood (Sequoia sempervirens) forest of Muir Woods National Monument, for example, 567 seedlings per acre (1,400 seedlings/ha) were observed at post-fire year 134. The dense understory was codominated by redwood and California bay trees that began as sprouts and seedlings following the 1845 fire."
Howard 1992 goes on to explain that regaining conifer forest from Bay Laurel after a clear-cut may require extensive management: "Prescribed burning alone is not effective in removing California bay from clear-cut timber areas. Prescribed fire will top-kill California bay, but follow-up mechanical or chemical control of sprouts will be necessary until conifer seedlings are established."
All of the above citations are meant to emphasize the ecological potential for conifer expansion into 1239 acres of land owned by SJWC that appear from the air to be dominated by hardwoods (California Bay is the primary species on 76% of this land). This land has gone through a historical clear-cut and two recent fires. Ecologically, it is very likely that these areas were once a mixed hardwood and conifer forest. If this is true, the process of transitioning back to a conifer forest will be very slow, thus we might not be able to see evidence of Group A timber species in our aerial photographs.
Ecological Potential of the Chaparral Areas
San Jose Water Company owns at least 1900 acres (of those lands mapped by MROSD) that contain chaparral species such as Scrub Oak, Chamise, Ceanothus, Mountain Mahogany, and Big Berry Manzanita. The Lexington Fire burned 85% of this land, and 46% had been through the Austrian Gulch fire as well. A plethora of ecological studies, conducted in coastal California over the last several decades, have supported the idea that the forest-chaparral boundary is a dynamic entity largely controlled by the fire regime (Franklin 2006, Franklin 2005, Wells 2004, Franklin 2001, Minnich 2000, Minnich 1997). Around the San Francisco Bay Area, several studies have documented the invasion of chaparral by Douglas-fir in recent history (Horton 1999, Dunn 1994, Horton 1992, Sparling 1994). If any of these chaparral areas owned by SJWC currently contain young Douglas-fir individuals, which is definitely possible, these areas should count towards final estimates of timberland.
Work completed by Horton, Bruns and Parker (1999) suggests that ectomycorrhizal fungi associated with Arctostaphylos sp. (manzanita) actually facilitates the establishment of Douglas-fir seedlings: "Aerial photographs taken over the last 50 years document forest succession in chaparral sites in Marin County, California. Field surveys suggest that Pseudotsuga menziesii (Douglas-fir) differentially establishes only in chaparral dominated by Arctostaphylos spp. (manzanita) and not in chaparral dominated by Adenostoma fasciculatum (chamise)....In this part of California, both the mixed evergreen forest and chaparral communities are stable aspects of the vegetation landscape because of the Mediterranean climate, topography, soil type, and fire history. Depending on current climatic trends and fire history, however, vegetation boundaries are dynamic and mixtures of species from both communities occur in some locations....Results from the vegetation survey and seedling survival experiments both support that Pseudotsuga seedlings survive in Arctostaphylos patches but not in Adenostoma patches."
For reference, MROSD had mapped 740 acres of SJWC land (approximately 40% of all land mapped as chaparral) as containing manzanita species, although some for these are a mixed chamise-
manzanita series.
Concurrence with the NTMP Application
Many sections from the NTMP application concur with the idea that clear-cuts and the Lexington Fire caused high mortality of Coast Redwood and Douglas-fir, and that certain areas currently dominated by hardwoods or chaparral are in the process of slowly regenerating conifers. (Note: The authors of the NTMP frequently use the term ‘brush’, which we believe to be consistent with chaparral species).
First, this section states that some areas of the NTMP zone had remained cleared for some time (thus these areas would take longer to regenerate conifers):
Due to varying patterns of settlement and land use since that time, some areas remained cleared for periods of time for use as homesites or agricultural land, and other areas appear to have been used for some small scale fuelwood gathering activities. The property’s predominant use shifted to watershed management near the beginning of the 20th century, and since that time the stands have regenerated themselves from sprouts and seed. –pg 50
Next, several sections mention the high mortality of the Lexington Fire:
Fire has drastically modified the stand conditions throughout much of San Jose Water Company timberlands. High levels of mortality, focusing mainly on the component of Douglas-fir and suppressed redwood, has resulted from the conflagration of 1985 known as the Lexington Fire. –pg 51
This elevated presence of snags is… an indictation of the forested setting demonstrating a short term response to an abiotic stress factor, namely the Lexington Fire of 1985. – pg 78
With the introduction of a stress factor of wildfire in 1985, these suppressed trees could not maintain a level of health and eventually [would] succumb to damage that was incurred during this conflagration. –pg 79
In addition, the following sections clearly state that the mortality of the Lexington Fire caused hardwood and chaparral dominated 'clearings' that are in the process of regenerating conifers:
Across the project area there are areas that are generally less than 3 acres where the Douglas-fir trees experienced intense crowning during the Lexington Fire in 1985. These areas can be identified by the openings in the canopy, and the current existence of aggregated, larger snags. Most of these areas support a significant level of conifer regeneration. In time, these aggregated snags will collapse, the conifer regeneration will out compete the brush, and these “openings” will become stands of early-successional sapling redwood and Douglas-fir. –pg 81
Several major disturbances, however, have influenced the development of the stand. Major earthquakes in 1906 and 1989 would have likely altered the stand structure of the current stand to some degree. Several major fires are also known to have influenced some or all of the plan area…. The disturbances are known to have been large enough to create openings in the forest canopy which have allowed some regeneration to occur. Finally, some overmature trees, particularly Douglas-firs, have died and created other natural openings, which have been filled in by commercial and non-commercial tree species. –pg 97.4
Finally, the following sections detail how management will be conducted to return hardwood and chaparral dominated areas to occupancy by Group A species:
Further, site occupancy over time of Group A species will not be reduced relative to Group B species. Such a shift in site occupancy will be prevented by selecting trees for harvest in areas where other Group A species are already established and can be expected to occupy the site following harvest. Additionally, while hardwoods are not proposed for management, some hardwoods will be felled during harvest operations in order to favor already present conifer trees…. Finally,…planting of conifer species will be done as needed, particularly in areas dominated by brush or Group B species, increasing the relative stocking over time of Group A species. –pg 97.3
Management objective of the NTMP #7: Maintain species composition with an emphasis on increasing conifer stocking levels where non-conifer trees are overstocked. Supplement natural regeneration through planting, as deemed necessary. –pg 97.9
The "capability" of SJWC land to grow Group A species
If the FPR language really means that any area ecologically "capable" of growing Group A species counts towards "Timberland" acreage, then SJWC is certainly far above the allowable limit of "Timberland".
While some of the hardwood and chaparral zones may be on drier slopes or different soil types than could support Group A species, most of the Santa Cruz Mountains is capable of supporting Douglas-fir if it were planted and managed (according to the USFS climatic requirements for Douglas-fir, such as 34 - 134 inches of annual precipitation, 195-260 frost-free days, etc). According to latest California total annual preciptation estimates of the Natural Resources Conservation Service, all of the land owned by SJWC has recieved an average of 37 to 53 inches of annual precipitation since 1960.
In addition, the FPR states that Christmas tree farms count as legal Timberland. Indeed, many Christmas tree farms in Santa Cruz Mountains are on higher and drier slopes than many Group A species are found on naturally. Most of the land owned by SJWC would be absolutely within the climatic requirements of the common Christmas tree species Scotch Pine (Richardson 1998). As another side-note, the Group A species Monterey Pine could probably thrive over much of the Santa Cruz mountains if competitors were removed initially. While locally rare on the California Coast, Monterey Pine is invasive in many areas where it is allowed to establish (Richardson 1998), and much of SJWC land is certainly 'capable' of growing Monterey Pine given its climatic requirements.