This is a solid study that should be deserving of publication. It presents a valuable dataset and lends new insights not only into the hydrologic status of these particular poplar plantations located in a water-limited, mid-latitude environment but also into fundamental relationships among attributes of the surface water and energy balances. However, in my view, and similar to statements by the anonymous reviewers, the interpretations need to be corrected in a few places, both in terms of relationships among reported variables (e.g. Rs vs. LAI and LE/LEeq vs. Rs), as well as in terms of the sustainability and perceived threats of the plantation activity.

Assessment of Sustainability Is Still Not Aligned With This Study's Findings: The sustainability of the plantation operation is inadequately quantified and this term should be either dropped or more carefully employed. The addition of Section 4.3 does not ameliorate the situation. What might be unsustainable is the use of groundwater, either directly by the trees or also via irrigation, to support the plantation, particularly if the rate of groundwater extraction exceeds the rate of recharge. That has not been assessed here, and while that outcome is plausible or even likely, the methods employed in this study are insufficient to fully substantiate the claim. The main finding is that the poplar plantations evapotranspire all of the water that is supplied via precipitation and irrigation. That is an important finding but does not directly address the question of sustainability. The paper does not clearly document how the establishment and operation of these poplar plantations is a threat to adjacent ecosystems or may compromises the long-term sustainability of livelihoods in the region. I agree that discussion of these points is acceptable and even warranted but I urge the authors to do so within the bounds of what is supported scientifically in this study. For example, I would argue that the following statements could be part of the discussion: In wet years, the plantation itself is in hydrologic balance with the water that arrives as precipitation, with evapotranspiration consuming nearly all of the precipitation. The same is true in dry years, but irrigation increases ET even further by depleting groundwater. Even if the plantations are in hydrologic balance with water delivered as precipitation, their existence and operation could be a threat to adjacent ecosystems and livelihoods if those rely on runoff or groundwater recharge from the areas where the plantation has been sited. In the absence of the plantations it is likely that groundwater recharge would increase, especially given the sandy textured soil that tends to allow rapid infiltration and percolation as well as limit moisture delivery to the atmosphere directly from the soil surface itself. While poplar plantation growth in this water-limited location might be sustained by the modest precipitation in the region, it could still be unsustainable for the broader context of the region's ecosystems and livelihoods. To truly assess this one would need to study (a) the surface water balance at the same site pre-plantation or at an adjacent, similar site but without a plantation, and/or (b) groundwater levels both spatially and temporally. New text appears notes that Zhang et al. 2014 documented water table decline over the last 30 years, so some of this may well already be substantiated. If that's the case, the argumentation needs to be rebuilt to note that connection more clearly.

Cannot State in the Abstract That the Groundwater Table is in Decline: This is not studied or reported here. You could potentially report that, or certainly discuss it, but it is not a major finding from the present study.

Cannot Conclude that Fast-growing, Water-intensive Species Like the Poplar Plantation Are Poorly Adapted for Water-Limited Regions: From the data presented, the plantation growth appears healthy and well-adapted even to this dry setting. While irrigation was applied in the drier years, it is not clear how much growth or damage (mortality?) would have occurred in the dry years if irrigation had not been applied. Statements about the plantation being poorly adapted for water limited regions must be removed, for example the last statement of the conclusions.

Drought Impacts Are Only Weakly Assessed: Because of the irrigation it is not really possible to quantify drought response. The irrigation clearly had the potential to mediate the impacts of lower precipitation in 2006 and 2009, thus the true effects of drought cannot be quantified.

Correlation Between Resistance and LAI at a Seasonal Scale Does Not Indicate Influence of Other Factors (P15): On the contrary, doesn't this evidence primary control by LAI, which varies seasonally, at least when water is less limiting? Larger scatter in the relationship for the dry year(s) does indicate additional control by other factors. The argumentation needs to be corrected and clarified here.

Decline in LE/LEeq with Increasing Rs is Required by the Way Rs is Derived from Inversion of the Penman-Monteith Equation (P16): This should not be presented as a finding given that the relationship is essentially implied by the formulation.

Considerable grammar, syntax, spelling, and diction errors remain, particularly (but not only) in the text that has been revised or added as part of the revision. The manuscript must be edited to correct these errors before it can be accepted for publication.

P2
L10: "latent heat" to "latent heat flux"
L11: "sensible heat" to "sensible heat flux"
L20: "thread" to "threat"
P3
L10: "pf" to "of"
L28: "most of previous and current are only concentrated on" to "most previous and current studies concentrated only on"
L30: "is central important for" to "is of central importance for"
L27 to 31: recommend edit from "Whereas ..." to "Most prior work has concentrated primarily on the water balance of forest ecosystems, with less emphasis on the relationship of forest ecosystems to their environmental setting. Much can be learned from exploring the partitioning of available energy and ecosystem response to meteorological forcings such as droughts. Not only are they of central importance for understanding water and carbon balances (), but they also help elucidatie the degree to which forest water use is in balance with supply from precipitation, and hence the degree to which plantations located in water limited regions are sustainable in the long-term."
P4
L5: "in water limited" to "in this water limited"
L22: "shrubs as the understory layer were low at density due to manual removal" to "understory shrubs were kept at low density by manual removal"
P5
L1-2: "... from [the] southeast (during [the] growing season and [the] northwest [(outside of the growing season)]."
I cannot spend the time to provide additional writing edits but further corrections are required before this can be accepted.

The Zhang et al. 2014 paper appears to still be in review. Unfortunately, it cannot be cited until the paper has been accepted and has a full citation with digital object identifier and/or page numbers. This paper's findings feature prominently in the revised discussion (section 4.3). Please replace the citation there (p16,L21) and elsewhere in the paper to something like, "...groundwater, as we show in a forthcoming, parallel study."