Is the Tea Bag Index (TBI) Useful for Comparing Decomposition Rates among Soils?

• Published in: Ecologies (Basel) Vol. 3; no. 4; pp. 521 - 529
• Main Author: Mori, Taiki
• Format: Journal Article
• Language: English
• Published: St. Paul MDPI AG 15.11.2022
• Subjects: asymptote model; Decomposition; decomposition constant k; Environmental conditions; Polyethylene; stabilization factor S; Tea; Tea Bag Index; United Kingdom > UK
• ISSN: 2673-4133; 2673-4133
• DOI: 10.3390/ecologies3040038

The Bag Index (TBI) is a novel approach using standardized materials (i.e., commercial tea bags) to evaluate organic matter decomposition by determining two indexes: the early stage decomposition constant k (k_TBI) and litter stabilization factor S (S_TBI). k_TBI is defined as the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea, whereas S is the ratio of the stabilized to total hydrolysable fractions of green tea. However, it was recently revealed that both k_TBI and S_TBI deviate from the actual S and k values accurately determined by fitting an asymptote model to the time series mass of green and rooibos teas remaining (k_fitting and S_fitting, respectively). Nevertheless, k_TBI and S_TBI, which can be determined in a cost- and labor-effective manner, might indicate the relative values of k_fitting and S_fitting across different soils and be useful for comparative analyses. Therefore, this study investigated the positive correlations of k_TBI and S_TBI with k_fitting and S_fitting, respectively, in which case these indexes are useful for comparative analyses. However, the result showed that k_TBI was negatively correlated with k_fitting. This study underscores the importance of obtaining time-series data for accurately determining the decomposition constant of an asymptote model describing the decomposition curve of rooibos tea. S_TBI was positively correlated with S_fitting, implying that S_TBI can be used as an indicator of S.