Drought and Anthropogenic Effects on Acacia Populations: A Case Study from the Hyper-Arid Southern Israel

Round 1

Reviewer 1 Report

Thank you for submitting your manuscript. The study focuses on the important question of the influence of anthropogenic (land use) and climate (drought) on longitudinal survival of Acacia shrubs over several decades (45 years, between 1972–2017).

There are, however, multiple fundamental flaws that limit its relevance for Soil Systems readers. These concerns include:

• outdated nomenclature for Acacia raddiana and Acacia tortilis:
  • Vachellia tortilis (Forssk.) Galasso & Banfi Species recognized by EOL Dynamic Hierarchy 1.1 and EOL Dynamic Hierarchy 1.1
    Note: Acacia tortilis (Forssk.) Hayne  is Synonym for Vachellia tortilis (Forssk.) Galasso & Banfi according to EOL Dynamic Hierarchy 1.1 and EOL Dynamic Hierarchy 1.1
  • Vachellia tortilis ssp. raddiana (Savi) Kyal. & Boatwr. Species recognized by EOL Dynamic Hierarchy 1.1 and EOL Dynamic Hierarchy 1.1
    Note: Acacia tortilis ssp. raddiana (Savi) Brenan is Synonym of Vachellia tortilis ssp. raddiana (Savi) Kyal. & Boatwr. according to EOL Dynamic Hierarchy 1.1 and EOL Dynamic Hierarchy 1.1 Reference taxon from WWW in Species 2000 & ITIS Catalogue of Life Acacia raddiana Synonym according to NCBI Acacia raddiana Savi Authority according to NCBI
• World Wide Wattle might also be useful to clarify names, and how these fit within the general term of ‘Acacia’
• limited design – e.g. confounding design of single site per landuse
• misleading references to it being 45 year study, between 1972–2017: there were only 3 survey periods (one is published data) with no systematic survey protocol or timing
• entirely descriptive, as data is limited to exploratory data analyses (% change)

For these reasons, I would recommend developing your manuscript further and submitting to a regional journal focused on descriptive case studies.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Please see the attached for edits and comments directly on the manuscript.

Overall I enjoyed reading the manuscript but there are a few points that need revision and tightening up.

The presence of Tables in the discussion is problematic and the authors might want to consider moving these to the results section. Figure 5 is most likely Table 3. This fragments the discussion and makes it hard to see the final conclusions being presented by the authors.

Lines 260 to 270 are in italics. There are a lot of assumptions made in this part as well that might need more support.

I've marked several sections "awk" and have made a few suggestions but the authors should look at these sections/sentences and revise them for clarity.

The idea of using an annual rate of change based on 20-year gaps is problematic in assuming that these changes occur evenly over time. This might require further justification by the authors.

There are a few edits to be made on the figures and tables with respect to labels, information and fonts.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The paper “Drought and anthropogenic effects on Acacia populations: A case study from the hyper-arid southern Israel” submitted for review describes a long study of the effects of moisture conditions on the demography of Acacia populations in two ephemeral stream channels. Due to the significant ecological and spiritual roles and the importance of assessments of drought impacts on biological systems this paper have high scientific significance. Although the authors present a very detailed analysis and comparison with data from the literature several issues could be improved. I list the comments below.

1. It seems advisable to compare the area occupied by Acacia (in addition to the analysis conducted on the number of live and dead trees) during the different study periods. Tree numbers and mortality may be due to intra-population processes (competition, aging, and physiological mortality). Analysis of the area occupied is not as heavily weighted by these processes and may better reflect the true impact of drought and dam construction. It appears, from the methodology presented, that the authors have the data to support such an analysis.
2. Materials and Methods section. An exact year of dam construction should be given. On page three, in one sentence the authors state that in 1972 aerial photos were taken, 5 years before the dam was built (1972+5=1977); and in another that in 1994 a population survey was made 22 years after the dam was built (1994-22=1972).
3. From what size were Acacia individuals inventoried? Were all found individuals (even 1 cm in height) inventoried?
4. In the Results section, I propose to discuss rainfall variability and drought delineation first and then discuss demographics of Acacia populations in both valleys. The drought is the background for the demographic changes in Acacia numbers.
5. There is no statistical test that would indicate whether the differences between the wadis and study periods are statistically significant. The statistical analysis that could probably be used is a chi-square test based on contingency tables.
6. It is not clear what test the authors used to compare the mean precipitation in figure 4. Moreover, it appears from the analysis of the graph that the period of drought lasted from 1995 to 2012 and not from 1995 to 2009.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The high mortality rates and poor recruitment of Acacia tortilis and raddiana has for long been a worry from an ecological and conservation viewpoint, and an intriguing scientific question since long-term data in general are rare. Against that background this study could provide valuable insights since it builds on a dataset spanning the periods from 1972 till 2017, and enabled to follow individual trees at 3 points in time. Nevertheless, the study is not successfully exploiting this potential in its current form. In general, a better structure of the text itself will improve the quality of the paper. But there are also other issues that the authors should consider.

The paper is called a case study but in its first paragraphs it has a wide scope and describes general information of Acacia in its wide distribution range of North Africa and the Arabian Peninsula. The Israeli populations are, however, at the northern extension and leading range of the species distribution and there are reasons to believe they grow under different conditions. For instance, rainfall pattern is much more regular (low, but still nearly annual) than in other hyper arid areas where successive years pass by without rainfall at all.  As a case study it is therefore an outlier case and the authors should be very careful extending any results to acacias in general. As a local study of the special conditions in this area it might, however, provide interesting information. To do so the authors need to elaborate the different chapters.

The Introduction chapter needs information about the climate of the area in general. The mean rainfall is apparently low but unlike the Saharan and Arabian deserts it is fairly regular compared to a large portion of the Acacia tortilis / raddiana distribution range. Annual rainfall data from Eilat are presented in fig 4 (line 174, Results chapter!) with no explanation why the rather arbitrary “drought period” is placed as it is. One should need to know on which criteria this period is considered as a drought.

There is a fair amount of acacia studies in this region. Some of them by excellent scholars. Based on this the introduction should present aspects of Acacia distribution, ecology and adaptions leading to what can be expected regarding population dynamics through the different periods in the two small wadies studied. It is problematic that the study in general and its results are not seen in any theoretical framework.

Since the base of the work is the Bendavid-Novak and Schick study, this study and its results should have been presented shortly. The authors should keep in mind that even though a dam is an anthropogenic disturbance- it is a very special type. 

I cannot find any permission to use the data Bendavid-Novak and Schick study (other than the airphotos used) and wonder whether it could be of ethical concern.

The three sentences about the objective (s) are not particularly good. It is too general and makes it rather difficult to properly test the hypothesis.

The methods chapter must be better described. It is referring to field and laboratory work. What kind of laboratory work was done, and how was that used in the study? Field measurements such as height and crowns size have been done, but it is hard to see the results of such measurements. There is not a description of the work done to compile the two datasets (GIS?) and there is no rigorous analysis. Would it not be possible to make a model assessing how different factors affect the survival and recruitment across the two sites? Different topographical and hydrological parameters could easily be extracted from elevation models, for instance different distance measures could shed light on how distance to past/new streams, the dam (i.e. water availability) affects mortality and recruitment.  Another approach could be to look at spatial point patterns or clustering (see Isaacson’s study) in order to reveal any patterns in distribution of different life history trajectories (alive-alive-dead etc). Whether this is possible with the current datasets should be considered by the authors.

The result chapter must also be better presented/clearer structured and should not include Introduction and discussion elements. It should present results of all the data derived from the different datasets. In its current state, it is difficult for the reader to extract the essence from the long listing of rates and percentages in the text. Please consider a better way to write up the text and use of tables to present all the numbers. Reading the current text it is difficult to get an easy overview of the differences between young and older trees, between A. tortilis and A. raddiana and between trees growing in old and newer streams. These are elements that later pop up in the discussion.

Discussion

New information should not be presented in this chapter. However, in this manuscript even methods and results are first presented here (section 4.5; why is table 3 included?). The discussion should be based on the result presented earlier.

One can wonder whether the number of data points are too small, as for some groups they are well below 10. Is it possible to generalize based on e.g. 3 recruits in w. Yael. Perhaps, if the underlying argument is spelled out? It is difficult to assess for the reader based on the current text.

The discussion contains surprises (cf 4.3 new recruits, and 4.4 roots) and the authors simply assume reasons without any further documentations. Further discussion is needed to make such sections understandable and acceptable.

The mortality is generally high in this area and not only in the dryer period. That the mortality is higher for older established individuals while the recruits survive also need a better treatment than the authors give in this manuscript (4.2).

As a reader one tends to speculate whether the apparent dependence on surface water makes the Acacia populations vulnerable to rather small temporal and spatial variance in soil moisture. The paper does not provide any clue.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

This manuscript could be revised for a regional journal, or once future years of data are available to rigorously track population trends.

Reviewer 3 Report

Line 221-223 the distance is in meters. Give this information for precision. 

Reviewer 4 Report

The previous comments has been adressed and the changes made has improved the manuscript.