In MM05 (EE), we reviewed literature on bristlecones because these trees were supposed to be unique radio receivers for world temperature. Obviously the specialist literature stood against this proposition. We cited a number of interesting articles by Mooney in American Midland Naturalist in the 1960s – none of which are considered by Juckes in his “evaluation” of millennial reconstructions, including the following:
Even in higher stands, their [bristlecone] principal botanical competition in many locations is with big sagebrush [Wright and Mooney, 1965; Mooney et al., 1964] with bristlecones outcompeting big sagebrush on moister dolomite substrate. This effect is vividly illustrated by Figure 2 of Wright and Mooney , where the sharp geological contact between the dolomite and sandstone is clearly shown by the change from bristlecone pines to sagebrush at the same elevation The same effect is also perhaps shown in the charming 19th century painting (Figure 7), where a sharp change in vegetation at the same elevation is easily observed.
Here is the very interesting Figure 2 from Wright and Mooney . I’m probably more used to looking for geological contacts than most of you, but there is a really remarkable vegetation demarcation of the contact between granite and dolomite illustrated in the picture below. What makes this particular picture so remarkable is that the contact is marked by a vegetation contrast – bristlecones on the dolomite; sagebrush on the granite or sandstone. Since the geological contact runs uphill-downhill, the contrast is clearly differentiated from an altitudinal gradient usually associated with temperature.
At the NOAA website on drought, the following 19th century water color is shown (illustrated in MM05 (EE)). Although there is no specific statement that this water color illustrates a similar geological contact, there is a very similar-looking vegetation contact running uphill-downhill, which I suspect is due to the same phenomenon.
Here are some comments from Wright and Mooney 1965:
The main objective of this study was to determine the environmental gradient or complex of gradients that controls the distribution of bristlecone pine on the White Mts. However it soon became apparent that any consideration of bristlecone pine distribution must include a study of sagebrush since their patterns are complementary…
Sagebrush accounts for only 13% of the shrub cover on dolomite but on sandstone it constitutes 75% and on granite 78% of the total shrub cover. Sagebrush is comparatively least abundant on dolomite. This face alone acconts for a substantial difference in total shrub cover among the three substrates, since cover by other shrubs is low on all three….
A comparison between treatments for any given soil indicates that all soils are severely deficient in phosphorus, but the deficiency is most severe on dolomite…
It appears then, in answer to the question posed earlier, that bristlecone pine is responding in gross terms primarily to a moisture gradient in the White Mts. This would explain how its distribution runs counter to most of the subalpine herb and shrub components which seem to be controlled essentially by temperature gradients. This viewpoint is an obvious simplification of the complex environmental relationships operative in controlling plant distribution in the subalpine zone of the White Mts. However most of the mechanisms which have been described tht favor the development of bristlecone over sagebrush, its most severe competitor, can be explained directly or indirectly on a basis of moisture balance.
It seems pretty obvious to me that any species that is competing with sagebrush is moisture-limited and that there will be, at a minimum, an interaction effect between temperature and precipitation. Juckes’ current line of justification is to issue the curious challenge for us to show that bristlecones are a worse temperature proxy than the other so-called “proxies”. No, Martin, the challenge is for proponents of bristlecones/foxtails to show that they are valid temperature proxies. There were plenty of warnings in the literature prior to MBH98. There are more warnings now.
Wright RD and HA Mooney, 1965. Substrate-oriented Distribution of Bristlecone Pine in the White Mountains, American Midland Naturalist 73