Fire Effects on Lichen Biodiversity in Longleaf Pine Habitat

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article presents relevant research on the effects of fire on both epiphytic and soil lichens. The proposed management approach for longleaf pine forests is noteworthy, as it offers practical implications for the conservation of soil lichens in particular.

However, certain aspects of the manuscript need to be improved.

 

There is a general concern that should be clarified. Throughout the manuscript, the terms longleaf pine forests and longleaf pine habitat are used, but plantations of pine are not mentioned. A distinction should be made, as they are not synonymous and differ in stand structure and in the diversity of both epiphytic and soil lichens. The study area is described as a site where approximately 60 years ago there were no trees. Is this a secondary forest? Is it a plantation?

Abstract: It is excessively long and should be more concise, following the journal’s guidelines.

Keywords: It is recommended to remove those already included in the title and to add other relevant terms, such as oaks or hardwood trees, prescribed fire, management…

 

Introduction

It is recommended that the introduction be revised or expanded to include more recent references, for example in the following citations:

Many lichens are known to be dispersal-limited (Hale 1952; Stevenson and Enns 1992) and may be slow to recolonize a site.

A positive correlation often exists between greater lichen cover and light availability in the forest canopy (Gustafsson and Eriksson 1995).

In the taiga, Klein (1982) concluded that fire can destroy lichens and other forage when observed over a short-term period of 50 years or less, potentially reducing the taiga’s ability to support caribou.

The stated objective is: Our study sought to assess lichen epiphyte diversity and abundance on longleaf pine and oak trees, the diversity and abundance of understory ground lichens in this habitat, and to quantify the effect of prescribed fire on the lichen diversity. The introduction focuses on longleaf pine, but no studies on lichen diversity in oaks are presented to justify their inclusion in the study. Addressing this point would strengthen the introduction, making it more comprehensive and providing clearer justification for the inclusion of both tree types.

In Figure 1, the note 'created by and data sources' is not clearly visible. Improve the quality so that it can be read well.

 

Material and methods

“Based on a 1965 aerial photograph, the study area appeared to lack trees at that time. Hence, we estimate the oldest trees to be 58 years or less, suggesting the area was logged in the past”. Please clarify whether this refers only to pines or also to the other tree species reported.
It seems to be a plantation rather than a natural forest with trees of different ages. Clarifying this information would help to better describe the forest structure under study.

It is recommended to include the sampling site location in the map shown in Figure 1.

Post-burn year2. “Two years after the burn, we surveyed the hardwood trees in the 10-acre study area for live standing versus fallen trees”. Please justify why only hardwood trees were considered; pines should also be included to allow for better comparisons and to understand potential differences.

“We only surveyed the larger trees with a diameter at breast height (DBH) of ≥ 4 in (10.16 cm)”. This sampling criterion based on tree diameter should be applied to all epiphytic lichen surveys, both before and after the burn. It should be stated at the beginning of the Post-Burn section.

 

Results

Table 1. The 'common name' column could be eliminated, as it does not provide relevant information. Instead, a column could be added with the growth form of the lichens (crustose, foliose, fruticose) to complement the analysis, given that the lichen coverage is being evaluated by type.

It would also be useful to provide an additional table with the average values per tree species and tree zone pre-burn and post-burn, as well as for the soil lichens by zone pre-burn and post-burn.

Figures 3, 4, and 5 do not need titles at the top, since that information should be included in the figure captions.

Figure 3: Statistical significance of the data shown should be indicated.

Figure 4: Only oak data are presented. It would be useful to either include pine data in this figure or provide a separate figure with pine data.

“Ground lichen species that were lost from burning included Cladonia evansii, C. parasitica, C. peziziformis, C. rappii, C. ravenelii, C. subcariosa, C. subradiata, C. subtenuis, and Trapeliopsis granulosa.” — Scientific names should be italicized.

Figure 5: The graph is confusing. Could it be represented in a different format? Alternatively, it could be split into several graphs by tree base, trunk, and canopy, or separated by burned vs. unburned areas.

Figure 7: Does the photograph represent a fallen tree, as suggested by the figure caption, or canopy branches, as stated in the text? This should be clarified.

 

Discussion

“By Feb. 2, 2023, 24 hours after burn ignition, many of the small to medium-sized oak trees had burned at the base and fallen over; some were still smoking”.  In the surveys, no differentiation by trunk diameter classes is provided, yet here the text refers to small to medium trees. Please specify what is considered small to medium, taking into account the maximum trunk size at maturity, not only the sizes present in the study area.

The manuscript states that “The physical bark properties influence lichen species composition and abundance (Broad 1989),” but chemical properties are also highly relevant when comparing pines and hardwoods. It is necessary to include a more recent reference.

Char height on the conifers (mean: 62 inches, SE 5.35) was greater than twice that of the hardwoods (mean: 29.4 inches, SE 1.56). This belongs in Results, not Discussion.

“Ground lichens (Cladonia spp.) were blackened and fragile to the touch or completely gone at our study site post-fire. Some still showed their three-dimensional structure, but they were not green at the base. Mechanical damage post-fire could be an issue at sites where ground lichens were previously abundant, and it is possible that avoidance could facilitate ground lichen recovery”. This group of species is highly relevant, and it would be important to discuss which factors may influence their persistence. No comparison is made with previous studies, although relevant literature exists that could corroborate and complement these results.

“Deciduous oaks generally allow more sunlight and moisture through the canopy. Turkey oaks, a deciduous species, provided the best lichen substrate at our study site.  Canopy lichen diversity was also highest on the turkey oaks, the tallest Quercus at our site (to 10 m). Sand live oak, an evergreen, did not offer suitable lichen substrate, while the bluejack oak were young and generally unoccupied by lichens. The larger water oaks generally do not support many macrolichens, but crustose lichens are often present on their    trunks. Crustose lichen diversity was similar in our burned and unburned plots; however,smooth-barked oak trees abundant with crustose lichen declined post-fire·”.      The variation in oak lichen diversity and cover is not discussed in relation to possible causes, nor compared with other studies. This should be addressed.

Lichen growth form diversity (crustose, foliose, fruticose) is analyzed, but the reasons behind the variation in their relative percentages are not explained. It would be important to discuss the implications of each growth form in relation to their substrate affinity and the successional stage of epiphytic lichens in the study area.

Conservation recommendations for management

“Some studies have documented detrimental effects of forest densification on lichens, which can occur without fires”, however, this could be related to ecological succession, a natural process toward ecological climax. Fire also affects lichen diversity and cover. The present study shows that soil lichens are reduced and damaged after prescribed burning.

This aspect should be further reflected upon, discussed and clarified.

References

There are references in the bibliography that are not cited in the text. Please review and remove those not referenced.

Author Response

The comments for all three reviewers are in one file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Forests Manuscript ID: forests-3825546 Research paper review

Fire Effects on Lichen Biodiversity in Longleaf Pine Habitat

 

Since prescribed fire is a management tool for maintaining overall biodiversity in certain forest ecosystems, it is worthwhile to examine the effect of fire on different groups of organisms, particularly lichens, which are highly sensitive to disturbances due to their low growth rate and dispersal limitation. The present study aimed to investigate the impact of prescribed fire on lichen abundance and diversity in Longleaf pine habitat. Therefore, the message of the present research is essential, as it also provides conservation recommendations based on its findings.

Besides appreciating the importance of this work, many questions arose in my mind while reading the manuscript, which needs a moderate revision in its present form. Hopefully, by incorporating the answers into the manuscript, the Introduction, Sampling, and Discussion will be more followable for readers. My general comments:

1. The authors mention biodiversity in the Title and Discussion; however, lichen community composition is not evaluated after the burning. It would be exciting to read more about the lichen community composition before and after the fire, as well as the post-burn species richness.
2. The manuscript contains interesting data on biodiversity; however, several pieces of information are less relevant from the study's focus point of view (e.g., post-burn vascular vegetation or the role of Quercus species in overall biodiversity).
3. I suggest following the same logical order throughout the Results and the Discussion (1. re-burn lichen inventory, 2. post-burn ground lichens, 3. post-burn tree canopy lichens).

 

My specific comments:

2nd row (Title): I suggest emphasising the adverse effect of fire on lichens

17-18: The diversity after fire was not shown in the Results and Discussion; I recommend completing the sentence with the information on when the post-burn sampling was conducted.

65: „for these ecosystems”

71: „Epiphytic lichens vary….” new paragraph

78-80: This sentence fits better into the previous paragraph (rows 60-70).

81: There is no doubt, but why is it important?

97: For example?

98-99: This statement could be supported by data estimating lichen biomass in these ecosystems documented in the literature.

Materials and methods:

I suggest restructuring the „Study area” description: I would start the text with the site description, including location, topography, and management, followed by a description of the vegetation.

158: The lichen species abundance was rated for the entire plot in the canopy. How was canopy sampling conducted at a height of 50-60 feet? By climbing or with drones?

195: What was the sampling design in the case of fallen branches post-burn? How many branches or sampling points were investigated?

Data analysis: What is the reason that the authors used an independent paired t-test and ANOVA? Did the authors consider analysing data using linear models? Perhaps it would be easier to handle the explanatory variables and site effects. Investigating changes in community composition would also be very informative and interesting. I suggest running, for example, non-metric multidimensional scaling (NMDS) to visualise relationships between communities and PERMANOVA to see whether the differences are significant. Another way could be the comparison of diversity indices. They are only recommendations. If the suggested analyses are beyond the study's goal, they can be skipped.

Table 1: indicating the conservation status of the species, would also be very informative

250-251: M, SD, n, t, and p – the text should be set in italics

Figure 3: „standard error (SD) of the mean (M)” instead of „standard error of the mean (SD)”

321: „4 and 24” – measure unit is missing

329-331: Diversity was only evaluated prior to the burn. Please consider evaluating data using diversity indices or comparing species richness before and after burning to gain a better understanding of the changes in lichen diversity.

Author Response

Reply to all three reviewers are in one word file.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This is a well-prepared paper presenting detailed data on the effects of fire on lichen diversity. The findings of this study can provide valuable insights for the conservation and management of lichen species. Below are some suggestions for revision:

1. line 64,  you mentioned that "Nitrogen-fixing cyanolichens are especially important for ecosystems", please provide a specific example and a supporting reference, similar to those included in the preceding or following sections of the introduction.

2. Latine names of Cladoniashould be in italic form, such as in line 111, 112, 134. Please check through the paper.

3. line 159, Authors should clarify how the canopy lichen abundance was rated?

4. In the results part, please refer to the latest database such as Indexfugorum or Fungal Names, and use the  currently accepted species names, because some of them has changed their genus name, which might influence your conclusion. For example, the current name of Parmelinopsis spumosa is Hypotrachyna spumosa (Asahina) Krog & Swinscow, and Parmelinopsis minarum is Hypotrachyna minarum (Vain.) Krog & Swinscow. 

5. line 258-260, 386-387, species names should be in italic form.

6. in Figure 4, the same question arises, how do you get the data of mean lichen cover for the canopy? 

7. in line 340, Fallen twigs might not always from the canopy, how to confirm they are canopy twigs?

Author Response

All three reviewers' replies are in one Word file.

Author Response File: Author Response.pdf