Lichens are unique symbiotic associations formed between a fungal partner (mycobiont) and photosynthetic partners, usually green algae or cyanobacteria. They constitute an important component of terrestrial biodiversity and play significant ecological roles in nutrient cycling, soil formation, water retention and habitat provision for numerous microorganisms. Due to their high sensitivity to atmospheric pollutants and environmental disturbances, lichens are widely recognized as reliable bioindicators of air quality and ecosystem health.

Urbanization is one of the major drivers of biodiversity loss worldwide. Rapid expansion of cities, road widening projects, infrastructure development and removal of mature trees have resulted in severe habitat fragmentation and degradation of epiphytic communities. Lichens are particularly vulnerable to such disturbances because they depend on stable microclimatic conditions and suitable bark substrates for survival and growth. Consequently, urban environments often exhibit reduced lichen diversity and abundance compared with natural ecosystems.

In India, urban lichen conservation has received relatively limited attention despite increasing developmental pressures on urban green spaces. In Coimbatore, Tamil Nadu, expansion of transportation networks and urban infrastructure has led to the removal of several lichen-bearing trees, particularly along major roads and urban corridors. Such habitat loss threatens local lichen populations and may reduce the ecological functions they provide within urban ecosystems.

Conservation strategies aimed at protecting urban lichens are therefore urgently required. Among the available approaches, lichen transplantation has emerged as a promising technique for conserving threatened populations by relocating healthy thalli from disturbed habitats to suitable receptor sites. Previous studies have demonstrated that successful transplantation can contribute to the preservation of lichen diversity and facilitate ecological restoration in modified landscapes.

The present study was undertaken to evaluate the feasibility of lichen transplantation as a conservation and rehabilitation strategy in Coimbatore, Tamil Nadu. Specifically, the study assessed survival, growth performance, attachment success and reproductive development of transplanted macrolichens relocated between two ecologically similar urban green corridors. The findings provide valuable insights into the potential application of lichen transplantation in urban biodiversity conservation and restoration programmes. Urbanization and anthropogenic disturbances have accelerated biodiversity loss, emphasizing the need for conservation and ecological restoration strategies in managed landscapes (Kongvaree et al., 2026).

Study
 
The study was conducted in two locations in Coimbatore, Tamil Nadu, namely Siruvani Road (10.9458°N-10.9412°N) as the donor site and Marudhamalai Road (11.0342°N-11.0429°N) as the recipient site. Both sites are situated within the semi-deciduous ecosystems of the Western Ghats foothills. The region experiences an annual rainfall ranging from 650 to 700 mm and a mean temperature between 28°C and 34°C. The dominant tree species present at both locations include Azadirachta indica, Albizia lebbeck and Pongamia pinnata, providing suitable substrates for epiphytic lichen growth. The field survey, lichen transplantation and monitoring were conducted between January 2023 and June 2023 in Coimbatore District, Tamil Nadu, India
 
Sampling design
 
A systematic sampling design was adopted for the study. A total of 45 donor trees were surveyed, from which 120 healthy lichen thalli were collected. Subsequently, 30 receptor trees were selected for transplantation, with a maximum of five thalli affixed per tree. Stainless steel wire staples were used to secure the thalli onto the bark surfaces. The transplanted lichens were monitored over a period of six months with observations recorded at monthly intervals.
 
Data collection
 
Data collection focused on thallus-level parameters to assess survival and growth. Measurements included thallus length and width (in millimeters), necrotic rank based on a scale of 1 to 3, attachment strength using a similar 1 to 3 scale, apothecia count and evidence of herbivore damage. These parameters were recorded systematically during each monitoring interval.
 
Field survey
 
During the field survey, 45 donor trees were examined, out of which 38 trees exhibited natural lichen occurrence. Four macrolichen species were identified, namely Parmotrema tinctorum, Heterodermialeucomelos, Dirinariapicta and Pyxinecocoes. Detailed observations were recorded for each occurrence, including GPS coordinates, tree diameter at breast height (DBH), height and orientation of lichen thalli on the tree, as well as necrotic rank and attachment strength.
 
Transplantation protocol
 
A total of 120 healthy lichen thalli were carefully excised intact from donor trees and stored under moist conditions using sterile wipes to prevent desiccation. These thalli were then transplanted onto 30 selected receptor trees, with a maximum of five thalli per tree. Fixation was carried out using No. 18 stainless steel staples and each thallus was assigned a unique identification number for monitoring purposes. The transplantation methodology was adapted from standardized epiphytic relocation protocols described by Scheidegger et al., (1995) and further refined based on long-term macrolichen monitoring studies by Gustafsson et al., (2013). Morphometric and vitality assessments were conducted following the criteria outlined by Nash (2008).
 
Monitoring
 
The monitoring of transplanted lichens was carried out over a duration of six months, with observations recorded on a monthly basis. Parameters assessed included survival status, thallus length and width (mm), necrotic rank (1-3 scale), apothecia count, attachment strength (1-3 scale) and percentage overgrowth. These measurements provided insights into the establishment success, growth dynamics and overall health of the transplanted lichens.

Survival rate
 
The relatively high survival percentages across all species suggest that the transplantation technique and selected host trees provided suitable microclimatic conditions for lichen establishment (Table 1; Fig 1).




 
Morphometric growth
 
Mean thallus length increased from 42.6±8.2 mm to 45.9±9.4 mm after six months, representing an average growth increment of 3.3 mm (Fig 2). Approximately 46% of surviving thalli developed apothecia, indicating successful acclimatization and reproductive activity. 46% of surviving thalli showed apothecia development.


 
Attachment strength
 
The attachment strength of the transplanted lichens improved significantly over the monitoring period. After six months, 63% of the transplanted thalli were firmly attached to the host trees, indicating successful establishment (Table 2).


 
Necrosis and herbivory
 
● 12% showed minor necrotic increase.
● 5% showed herbivore damage (mites/slugs).
● No mortality linked to substrate rejection.

The overall survival rate of 82.5% observed in this study is consistent with previous transplantation experiments conducted in temperate and boreal ecosystems. For example, Gustafsson et al., (2013) reported long-term survival of macrolichens up to 14 years following translocation onto retained aspen trees. Similarly, Scheidegger et al., (1995) demonstrated that epiphytic lichens can successfully establish when transplanted onto ecologically comparable substrates.

The absence of significant interspecific survival differences (p>0.05) suggests that macrolichens with foliose growth forms exhibit comparable resilience under short-distance relocation conditions. This aligns with findings by Ellis (2012), who reported that growth form and substrate compatibility are stronger determinants of transplantation success than species identity alone.

The significant increase in mean thallus length indicates active growth rather than passive survival. Lichen growth rates are strongly influenced by microclimatic stability, bark roughness and light exposure (Giordani et al., 2016). In this study, selection of rough-barked receptor trees likely enhanced water retention and attachment stability, reducing desiccation stress (Paoli et al., 2017).

Attachment strength showed strong correlation with survival supporting previous evidence that mechanical stabilization during early establishment phase is critical for transplantation success (Scheidegger and Werth, 2009). Improper attachment often results in detachment during wind or rainfall events, especially in urban corridors with higher airflow turbulence (Aptroot and van Herk, 2007).

Apothecia development in 46% of surviving thalli indicates reproductive activation post-transplantation. This suggests functional physiological recovery and ecological integration rather than mere structural persistence. Reproductive recovery after transplantation has been documented as a positive indicator of habitat suitability (Gustafsson et al., 2013; Nash, 2008).

Overall, the results demonstrate that short-distance (<10 km) transplantation within similar biogeoclimatic zones can effectively support epiphytic lichen rehabilitation in urban environments.
 
Recommendations

● Long-term monitoring (≥2 years).
● Integration into urban greenbelt planning.
● Use in compensatory afforestation projects.
● Policy inclusion in municipal biodiversity management plans.

Recent advances in AI-based plant health monitoring further highlight the growing importance of digital tools for long-term ecological monitoring and conservation programs (Reddy and Kumari, 2026).

Lichen transplantation is an effective short-term conservation strategy in urbanizing landscapes. The 82.5% survival rate demonstrates feasibility of assisted relocation within similar bio geoclimatic zones.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the author and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

The author declares that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.