Plant Responses to Changing Water Supply and Availability in High Elevation Ecosystems: A Quantitative Systematic Review and Meta-Analysis
Round 1
Reviewer 1 Report
This is a high quality paper that tackles a very important topic in a highly competent and professional manner. The final literature selection with suitable studies and the plant species "sample" set are impressive; the Results are informative and the Discussion is well articulated. Both Abstract and Conclusion are well synthesised.
Major comments:
a) While the authors are constrained to available literature in such a meta-analysis, it is a pity that there is no suitable literature on Africa, and it would appear that the suitable literature that came out is predominantly (if not all) in mountains with moisture surpluses (?). Although there is no literature that met the meta-analysis criteria in this regards, this would be worth mentioning in the Discussion - and an encouragement for such studies to done in these contexts.
b) A map showing the study locations would be a useful addition to Fig 1, to see the geographic spread (and geographic biases in the literature). In addition, overlaying this spread on a Köppen climate classification underlay would assist in determining the climatic spread of the studies: I suspect it would suggest a water-surplus Northern, Temperate bias, with limited studies from sub-arid/sub-humid and Southern high elevation systems? A skim through the localities in the suppl material suggests this (and of course Fig 1 shows N hem continents dominate the studies).
c) A look through suppl material at the species in the studies again shows a N, mesic bias - this can't be helped, but it worth noting that the POACEAE for instance are all C3, and are all relatively soft grasses: it would be interesting to conjecture what would happen if one included robust tussock C3 POACEAE (e.g. from southern African alpine/sub-alpine), that are adapted to extended seasonal drought, and a rainfall variability from ENSO. The meta-analysis should indicate that the POACEAE in the studies are not necessarily representative of POACEAE in all high-elevation mountains - and the results (lowered resilience of POACEAE under moisture availability decrease) are not necessarily representative: and in fact there is a large group of high elevation POACEAE that might not be as affected as the results show.
(a)-(c) in summary: the authors might want to elaborate in the Discussion / Conclusion on what data is NOT available to be able to give a holistic global predictor or pattern for vegetation change / plant response in high elevation regions - e.g. the authors mention Mediterranean-type mountains once, in passing, as being "under-represented" - but this is a critically important plant region in terms of biodiversity, thus is a massive gap in the literature that the authors can encourage future studies on (take the Cape Floral Region for example, with an excessively rich montane flora - but not represented due to lack of studies); also, sub-tropical grassy systems with C4-C3 grass community interfaces and high forb diversity (many with well-developed underground storage organs) could also be highlighted as a literature gap (for example, informal observations in southern Africa mountains suggest geophytes are likely to be among the most resilient species under climate change). The authors are therefore in a strong position to encourage a future trajectory of such research that fills in the biases and balances the mesic/sub-humid, N/S, functional trait biases in existing studies. The results in this paper should not be portrayed as a global narrative, and should be contextualised by region, moisture regime, and other constraints to being a global story.
Minor Comments:
l.37 - full-stop needed after (Larcher et al. 2010).
l.58 - CO2 needs 2 to be sub-scripted.
l.227 - Oceanea - spelling (Oceania in Fig 1)
l.272 - delete full-stop before (Figure 5)
Suppl material - Meta-analysis: sp. 319 - no sp. name?
Author Response
see attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is a very well-implemented and well-written meta-analysis study to determine the overall impacts of experimental soil moisture manipulation on high-elevation plant performance responses. I have only a few minor comments:
- Can you explain a bit more about how the funnel analysis is used to test publication bias? I was unfamiliar with this and and a bit more info would have been useful in the methods.
- It was somewhat unclear to me about the methods that people used to both increase and decrease moisture supply in their treatments. Knowing more about how researchers did this (and perhaps even reporting on these methods as a possible result graph) would provide some further insights into the meta-analysis results. In particular, how did studies decrease the supply of water? In a lab type set up, I guess it could mean that studies just didn't water some plants relative to others? How about in the field? If it was a covering of some sort, how might this have caused confounding of the treatment results?
- Likewise, it would also be interesting to know something about the 'baselines' that people were comparing their treatments to, in terms of moisture conditions. What exactly were the 'controls' across the different types of study set ups?
Author Response
please see attachment
Author Response File: 
Author Response.docx
