Competition and Niche Differentiation of Water and Nutrients between Broussonetia papyrifera and Platycladus orientalis under Prolonged Drought Stress

Round 1

Reviewer 1 Report

The paper focuses on a very relevant issue since frequent water scarcity affects plant growth worldwide. The paper  deals with competition for water and nutrients between plants of different physiology (Broussonetia papyrifera and Platycladus orientalis) under drought stress. This type of knowledge is worth to be extended to better understand relations between plants under water scarcity and develop nature based solutions to better manage water and nutrients.  

1) What about the niche differentiation of nitrogen and phosphorus between B. papyrifera and P. orientalis under drought stress?

2) Does interspecific competition affect the status of water, nitrogen and phosphorus nutrition of B. papyrifera and P. orientalis under drought stress and who is the winner?

As reported by the authors, the research results show that tested plants have diverse competition and niche differentiation modes to different nutrients under drought stress, and the effect of the competition should be seriously considered in mixed forests in semiarid areas.

The authors carefully emphasize that drought not only affects the water properties of plants, but also affects their absorption of nutrients. The paper presents a diagram of the experiment carried out in a legible and clear manner. What is important to eliminate individual size differences as much as possible, the experiment was started when the seedlings grew to 30 cm tall (approximately 2.5 months old for B. papyrifera and 10 months old for P. orientalis). This means that Authors took some methodological risks into account when planning the study.

Furthermore, the present study indicated that B. papyrifera benefited from water and nutrients competition under moderate drought and the competition mode of B. papyrifera and P. orientalis  is controlled by the dominant limiting factor—soil water content.

Introduction and Material and methods sections are comprehensive and are described in an concise and clear manner.

There are, however some weaknesses in discussion, therefore I recommend minor revision of the paper.

Minor issues to be corrected:

Chapter 4.1. Water sources competition and plants water status

Please supplement the chapter with current literature referring to current research on similar issue

Chapter 4.2. Plants N status and N sources change

L.300  – Please add a sentence or 2 on assimilation of nitrate so that the reader better understands what Authors mean. What new research says about the assimilation of nitrate in environmental research.

Chapter 4.4. Interspecific competition analysis

There is no reference to existing literature regarding interspecific competition. Please expand this chapter referring your results to current literature on competition between trees.

In summary, the paper is worth publishing in the Journal. Please expand referring your research to the wider research currently conducted in the world.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

The authors contribute a nice data set via well-designed incubation experiment for two plant species. The manuscript is generally well written and presented by several nice figures and tables. The authors found that interspecific competition would exaggerate drought stress and affects other physiological processes as indicated by a suit of proxies. I would suggest the authors to better summarize the results to make a stronger conclusion for the manuscript. Besides, the language (I only picked and cured several grammar errors in the text) could also be improved significantly to increase the readability of the paper. Collectively, the authors should make a thorough revision on the manuscript before publishable.

Major points:

1. The conclusion section should be strengthened.

2. The language should be improved.

Specific points:

L18: “alleviate” to “alleviated”

L19-20: “but PDE: PME ratio changes of 19 these two plants indicated that they lose” to “but the changes of PDE: PME ratio for these two plants indicate that they have lost…”

L23: “Our results indicate that …”

L70: Remove “both”.

L344-347: It is too stretching. You can’t say anything about gymnosperms or angiosperms under the circumstances of only two species inspected.

Author Response

Please see the attachment.

Author Response File: Author Response.doc