Climate and Vegetation Change, Hillslope Soil Erosion, and the Complex Nature of Late Quaternary Environmental Transitions, Eastern Mojave Desert, USA
Round 1
Reviewer 1 Report
This paper covers the fascinating and complex subject of linkages among climate, plant communities, and soils at location in the Mojave Desert that is unusual in representing a stark contrast in soils and plants on facing hillsides; this location represents an important example where the linkages can be examined for their roles after they interacted and caused drastic changes. By dating the soils, the timing of changes for each element of the system were elucidated. This study will hopefully guide more like it until we have a deeper understanding of these complex systems.
The paper is well written, fully illustrated, and easily understood (which is important because it must be read by experts in diverse specialties to have the impact it deserves). I only have minor comments, keyed to lines:
l 297. Maps of both bedrock and surficial geology have been published much more recently than those the authors mention. Two are: Miller, D.M., and Wooden, J.L., 1994, Field guide to Proterozoic geology of the New York, Ivanpah, and Providence Mountains, California: U.S. Geological Survey Open File Report 94-674, 40 p. Miller, D.M., 2012, Surficial geologic map of the Ivanpah 30' x 60' Quadrangle, San Bernardino County, California, and Clark County, Nevada: U.S. Geological Survey Scientific Investigations Map 3206, scale 1:100,000, 14 p
The latter map shows the extent of eolian sand sheets east of Ivanpah Lake and should be referred to as a source for that information. A companion map covers the north part of Ivanpah Lake, its authors are Schmidt and McMackin.
l 425. litter OUTSIDE of canopy, not "beneath"? Your pie diagrams do no show litter beneath canopy.
l 426. Can the authors cite support for the statement that canopy and litter cover "provide the most effective protection from erosion"?
l 464. change 'negligible' to 'far less' than.... Negligible is a relative term, and to a lichen the water retained by soils on the xeric side might be adequate.
l 555. You may want to note that eolian deposits are lacking in the high McCulloughs, so it is a partial analog for the Nipton Hills site.
l 748. Increasing (not increasingly)?
Author Response
We thank Reviewer #1 for the helpful comments and also for providing the most current references regarding geological mapping. Following are replies to specific comments:
Introduction - in contrast with the high marks given by the other two reviewers, Reviewer #1 scored the introduction with the ranking "must be improved." However, without specific suggestions as to what aspects require improvement, or what might be added, we choose to retain the original content of the introduction because we believe it succinctly states the problem of the mix of factors that potentially contribute to vegetation changes. Furthermore, the final portion of the original introduction accurately describes the purpose of the paper, and how it builds on a foundation of detailed geochronological and geomorphological research published previously.
L 297: The most current reference (Miller, 2012) has been substituted for the older one used in the original manuscript. The Miller, 2012 reference has also been added when discussing the aeolian sand sheet on the east side of Ivanpah Playa (p. 12, Section 3.2.2).
L 425: The text was clarified by referring to "plant litter on the soil surface",
L 426. Can the authors cite support for the statement that canopy and litter cover "provide the most effective protection from erosion"?
Response: The direct cover of a mineral soil surface by plant canopies and organic litter is universally recognized as one of the most important factors that protect against splashdrop impacts and erosion of soil materials, and consequently does not require a list of citations to back up the conclusion. Specific citations would only be necessary if more detailed claims were made regarding measured amounts of erosion related to variable amounts of cover.
L 464. change 'negligible' to 'far less' than.... Negligible is a relative term, and to a lichen the water retained by soils on the xeric side might be adequate.
Response: The recommended change was made.
L 555. You may want to note that eolian deposits are lacking in the high McCulloughs, so it is a partial analog for the Nipton Hills site.
Response - The claim that aeolian deposits are lacking in the upper elevations of the McCullough range is not correct. Although surficial deposits of loess are lacking, nevertheless, slopes clad with coarse rocky colluvium in the upper elevations serve as the same kind of aeolian dust trap as in the lower elevations of the nearby Nipton Hills study area. Fieldwork by the senior author in the higher elevations of the McCullough range indicated the same kinds of soils developed in coarse colluvium as are present in the Nipton Hills. Fine dust rich in silt and clays lofted high into the atmosphere contributes significantly to soil formation in higher mountain areas, as also has been demonstrated in other tall mountain regions, for example the Wasatch Range in Utah. Consequently, the soils in the higher elevations of the McCullough range, as well as the vegetation occupying those areas do represent an appropriate analog for possible vegetation conditions during the late Pleistocene at lower elevations in the Nipton Hills. Given this perspective, no change was made in the original text.
L 748. Increasing (not increasingly)? Response: The reviewer is correct, and the text was changed to "increasing."
Reviewer 2 Report
The article presented is of current interest, its contribution is important in the field of study.
It should be complemented with a review of current works, I recommend updating the bibliography.
In the conclusions, the results obtained with other previous works should be compared,
Author Response
Reviewer comment: "It should be complemented with a review of current works, I recommend updating the bibliography."
Response: We have updated the reference to the geological mapping of the area by including the reference to Miller (2012) (reference #23) in revision. In terms of other references, we believe the paper fully cites the most recent references that are directly related to the investigation and conclusions. For example, the inclusion of the most recent records from radiocarbon-dated woodrat midden studies (reference #53) brings essential information to the forefront that was absent in an earlier publication (reference #7). Other references (e.g., # 49, 72) have been published within the last two years and represent the most recent works that pertain to the topic of the paper. The paper is not a review paper, but rather, a presentation of original research that integrates multiple topics. Without specific suggestions from the reviewer regarding additional references that might be included, we have not added further references beyond what was originally included.
Reviewer comment: "In the conclusions, the results obtained with other previous works should be compared"
Response: We have compared our results at length with results of other studies in the main discussion section of the paper (sections 4.1-4.5), and consequently, we do not see the need to repeat such comparisons in the section 5 (conclusions). Rather, we chose to keep this section in its original form, particularly the comments regarding the relevance of knowledge of these complex landscape responses to understanding how future climate changes may act to alter existing ecological conditions.
Reviewer 3 Report
This is a very interesting paper and I enjoied reading it. It is well written, well organised ,scientifically sound and informative. Besides, I appreciated its critical spiritin the discussion and the conclusion, e.g. concerning envelope models to predict future changes in dryland environments.
I recommend to publish this paper as is.
Author Response
Reviewer #3 recommended no further changes, and we appreciate that he recognizes the importance of the brief comments in the conclusions.
