Responses of Soil Microbial Community Composition and Enzyme Activities to Land-Use Change in the Eastern Tibetan Plateau, China
Round 1
Reviewer 1 Report
A well written paper with satisfactory selection of methodologies and valuable data on an important topic. Generally, the results are well presented, however, there are few suggestions/recommendations that authors can incorporate in the manuscript.
- Line 75 - Please specify the associated microbial group
- Line 115 - Please classify the soil according to Soil Taxonomy or WRB classification system
- Please give some details on the parent material of the studied soil
- Line 148 - The authors should provide the chemical analysis for the determination of total soil P - see for example Journal of Plant Nutrition and Soil Science, 164 (435-439), 2001
- Please use standard font size through the text
Author Response
Point 1: Line 75 - Please specify the associated microbial group.
Response 1: Thanks for the comment. "anaerobic bacteria and 16:1ω5c" has been changed to "anaerobic bacteria and AM fungi (16:1ω5c)" in our revised manuscript. (Line 77, Page 2)
Point 2: Line 115 - Please classify the soil according to Soil Taxonomy or WRB classification system. Please give some details on the parent material of the studied soil.
Response 2: Thanks for the comment and suggestion. "The soil is classified as belonging to the mountain brown soil" has been changed to "The soils at the study area are formed from weathered granite and classified as Cambisols and Regosols according to IUSS Working Group WRB [25]" in our revised manuscript. (Line 116-118, Page 3)
Point 3: Line 148 - The authors should provide the chemical analysis for the determination of total soil P - see for example Journal of Plant Nutrition and Soil Science, 164 (435-439), 2001.
Response 3: Thanks for the suggestion. We added the chemical analysis for the determination of total soil P referred the example Gasparatos, D.; Haidouti, C. A comparison of wet oxidation methods for determination of total phosphorus in soils. J. Plant Nutr. Soil Sci. 2001, 164, 435-439 in revised manuscript, and the detailed revision can be found in Line 155-159, Page 4.
Point 4: Please use standard font size through the text.
Response 4: Thanks for the comment. We rechecked and used standard font size through the text.
Reviewer 2 Report
The manuscript addressed the important issue of the effect of land-use changes on microbial communities composition and function. The experimental design is appropriate and analysis are satisfactorily carried out. The paper is well written and the result may be of interest for journal audience.
Author Response
Many thanks for your high quality comments, we are very grateful for your recognition and appreciation of our manuscript.
Reviewer 3 Report
The topic addressed is relevant for assessing forest management in abandoned lands. I have some concerns on the experimental design. A battery of soil microbial analysis is applied to a low number of soil samples. Given the hypothesis stated by the authors that soil physicochemical properties could explain the differences in soil microbial communities, there is no control of the mineral soil properties in the different stands. Therefore, uncontrolled differences in the soils, unrelated to land use change, could confound the interpretation of obtained results. This is particularly relevant for soil texture which has a strong influence in soil carbon dynamics and the associated microbial activity. I recommend analyzing texture in the soil samples to assess to what extent the soils for the different plots are similar. From the available soil data, it is not evident that the soil type factor is random among land uses: TP is highly determined by soil mineral properties. TP is lower for GL than for the forest land uses studied. Could this difference relate to GL developing in poorer soils? In this case, differences in soil microbial properties would be due to differences in soil properties rather than to land uses change. Specific comments directly included in the manuscript.
Comments for author File: 
Comments.pdf
Author Response
Point 1: Land use change may encompass very different changes on the type of land use that may occur under very different soil and climate conditions. Are you expecting to find a general pattern of change in the soil microbial community for all kind of land use change?
Response 1: Thanks for the comments. We fully agree with the comments. Changes in land use can substantially alter soil and microclimate conditions and, consequently, microbial community composition and microbial activity. In this paragraph, we just expect to review the results of different studies in the past relative to the land use change similar to our study. To avoid confusion, we deleted the sentence “However, there appears to be no consistent effects of land-use change” in revised manuscript. (Line 68-69, Page 2)
Point 2: A recent study conducted in an oak forest persisted for more than 100 years reported that both microbial biomass and enzymatic activity levels were distinctly lower in ancient forests when compared to historically cultivated sites. Confuse sentence: please rewrite.
Response 2: Thanks for the comment. The sentence was rewritten as “A recent study conducted in an oak forest showed that both microbial biomass and enzymatic activity levels were distinctly lower in ancient forests when compared to historically cultivated sites” in revised manuscript. (Line 78-80, Page 2)
Point 3: Recently, forest restoration has been emphasized against any further disturbances in this region. Clarify the meaning of this sentence. Is forest restoration preventing disturbances?
Response 3: Thanks for the comment. The sentence was rewritten as “Recently, forest restoration has been emphasized to prevent further deforestation in this region” in revised manuscript. (Line 90-91, Page 2)
Point 4: Specifically, we expected that differences in microbial community composition can be explained by differences in soil physicochemical properties. Induced by land use change, isn't it?
Response 4: Thanks for the comment. Yes, the purposes of this work were to explore whether land use change induced differences in soil physicochemical properties and consequently influenced microbial community composition.
Point 5: With an average evaporation ranging between 1000 and 1900 mm y–1. Is this potential evapotranspiration?
Response 5: Thanks for the comment. Yes, the sentence was change to “with an average potential evapotranspiration ranging between 1000 and 1900 mm y–1”. (Line 115-116, Page 3)
Point 6: Nevertheless, some of the deforested sites failed to form secondary forest and turned into rye grass land (GL). Could be this failure related to soil limitations? e.g., shallower soil?
Response 6: Thanks for the comment. In the subalpine regions, there were some reasons for grassland formation, such as unreasonable land management or human activities that caused forest regeneration failure (fuelwood logging, overgrazing, etc.), of course, the shallower soil may also be one of the reasons.
Point 7: The coverage of undergrowth vegetation was about 60% in OF and SF, and 25% in PF. What about vegetation composition in GL?
Response 7: Thanks for the comment. We added “GL was mainly characterized as Lolium perenne L. and Thalictrum alpinum L., and the coverage was about 95%” in revised manuscript. (Line 131-132, Page 3)
Point 8: Did you check if soils were similar among land use types and stands? Particularly, soil texture usually has a strong influence in soil organic carbon dynamics and, consequently, on microbial activity.
Response 8: Many thanks for the comment. In this study, the subalpine regions in southwestern China were largely covered by old-growth forest dominated by firs in the last century. The selected secondary forest, plantation forest and grass land were all formed after harvesting old-growth forest based on similar altitude and soil. It meant that soils were similar among land use types and stands. Yes, soil texture usually has a strong influence in soil organic carbon dynamics and, consequently, on microbial activity. We will pay close attention to the effects of soil texture on microbial activity in our future studies.
Point 9: Soil nitrate is highly variable in time. Were all samples collected in the same period?
Response 9: Many thanks for the comment. We revised the sentence as “The soil samples collected from each plot in the same period were thoroughly mixed to obtain one homogeneous and representative sample.” (Line 143-145, Page 3)
Point 10: TP is generally highly determined by the mineral soil characteristics. Could GL mineral soils be poorer than the studied forest soils?
Response 10: Thanks for the comment. In the studied area, the rainfall is abundant and there is no canopy interception in GL, therefore, we speculate that it could cause TP loss of top layer soil in GL sites more serious than in forest sites.
Point 11: The effect of plant species diversity was not especially tested in this experiment.
Response 11: Thanks for the comment. We deleted “and diverse plant species”, and the sentence was change to “OF and SF with fertile soils favored highly total microbial biomass, anaerobic bacterial, SEM fungal communities, and β-glucosidase activities, whilst less fertile GL soil favored highly polyphenoloxidase activities”. (Line 392-395, Page 11)
Round 2
Reviewer 3 Report
After the improvements and clarifications in the revised version, the manuscript should only consider very minor corrections as suggested in the attached document.
Comments for author File: Comments.pdf
Author Response
Point 1: A recent study showed that both microbial biomass and enzymatic activity levels were distinctly lower in ancient oak forests when compared to historically cultivated sites.
Response 1: Thanks for the comment. The sentence was change to “A recent study showed that both microbial biomass and enzymatic activity levels were distinctly lower in ancient oak forests when compared to historically cultivated sites.” (Line 77-79, Page 2)
Point 2: Recently, forest restoration has been enhanced to improve forest cover in this region.
Response 2: Thanks for the comment. The sentence was change to “Recently, forest restoration has been enhanced to improve forest cover in this region.” (Line 89-90, Page 2)
Point 3: Specifically, we expected that differences in microbial community composition can be explained by differences in soil physicochemical properties induced by land use change.
Response 3: Thanks for the comment. The sentence was change to “Specifically, we expected that differences in microbial community composition can be explained by differences in soil physicochemical properties induced by land use change.” (Line 104-106, Page 3)
Point 4: One gram of soil samples was digested with 15 mL of 72% perchloric acid (HClO4) at 203 ℃.
Response 4: Thanks for the comment. We added a ‘space’ between “was” and “digested”. (Line 154, Page 4)
