Global distribution of forest leaf litter decomposition experiment used in this study. (Illustration adapted from respective paper).
The University of Hong Kong (HKU) has studied the role of invertebrates in forest litter decomposition. The study, led by researchers PhD candidate Xiaoyi ZENG and Professor Louise A ASHTON from the School of Biological Sciences at HKU, illustrates the significant contribution of soil invertebrates, specifically termites, to forest litter decomposition in tropical and subtropical regions. The study was recently published in Ecology Letters, and the results are imperative for preserving healthy ecosystems and conserving invertebrates in the wake of widespread environmental change.
Research Background
Litter decomposition is a crucial process in carbon cycling and nutrient turnover. Microbes, such as bacteria and fungi, are widely considered the most important decomposers in nature. However, soil invertebrates contribute a large proportion of decomposing and nutrient turnover and are therefore important for functioning and healthy ecosystems. Most previous studies on decomposition and nutrient turnover are conducted in temperate regions like Europe and North America, resulting in a biased perspectives and substantial knowledge gaps regarding the roles of invertebrates in global ecosystem processes.
A major invertebrate decomposer in the tropics are termites, which is often viewed only as pests to humans. However, termites are important ecological engineers in the tropics, helping to break down organic matter and redistribute nutrients. Termite dominance in the tropics, as opposed to temperate regions, should result in differences across regions regarding invertebrate decomposition, but this has not been well established.
Findings
In this study, the HKU research team included 476 case studies from 93 sites across the globe. A meta-analysis approach was used to assess the regional differences in forest litter decomposition mediated by invertebrates. The results showed that invertebrates contributed 31% to global forest litter decomposition, and the contribution of soil invertebrates in tropical and subtropical forests was 1.4 times higher than that in temperate and boreal forests. Termites, together with warm and humid climate contributed to the greater decomposition in tropical and subtropical forests.
This study highlights the global importance of invertebrates in driving the decomposition of forest litter, particularly in tropical and subtropical regions. However, the contribution of invertebrates to forest litter decomposition may be underestimated due to the current regional sampling bias. Additionally, this study highlights the importance of termites in nutrient cycling. Many still consider termites as crop pests and widely use insecticides to reduce termite abundance. Conservation of invertebrates in tropical and subtropical regions is crucial for maintaining ecosystem services, given the widespread environmental change in these areas.
Therefore, this study stresses the need to integrate invertebrate functions into earth system models as they contribute approximately 31% of global forest litter decomposition. An extensive and standardised data collection is of great value to develop global database of soil biodiversity and improve the predictive power of earth system models. Furthermore, forest management approaches that focus on insecticide use to control termite populations may have unintended consequences on ecosystem functioning (e.g. nutrient cycling). Instead, forest managers should consider conservation strategies that protect invertebrate populations and promote sustainable forest management practices.
‘This study shows that invertebrates are essential for decomposition, keeping ecosystems working by breaking down dead organic material. Invertebrates like termites are particularly important in the tropics and sub-tropics where most biodiversity occurs. Invertebrate biodiversity is threatened by human activities such as climate change, habitat loss and pollution. It is essential we mitigate biodiversity loss in order to maintain healthy, functioning ecosystems into the future,’ said Professor Louise Ashton, Assistant Professor of HKU School of Biological Sciences.
Click here to access the journal paper ‘Global contribution of invertebrates to forest litter decomposition’.
Authorship
This study conducted by the Biodiversity and Environmental Change Lab at The University of Hong Kong (HKU) (www.louiseashton.net). The Biodiversity and Environmental Change Lab is led by Professor Lousie A Ashton. The lab is dedicated to research exploring insect biodiversity and ecosystem function and understanding ecological responses to environmental change. This study was conducted by Xiaoyi Zeng (PhD student) as the first author and Professor Louise Ashton as the corresponding author. The co-authors include Huilin Gao from the Faculty of Business and Economics (HKU), Runxi Wang and Bartosz Majcher from the School of Biological Sciences (HKU), Dr Cheng Wenda at Sun Yat-sen University, and research teams from the University of Liverpool, the Natural History Museum, London, and the University of Bristol in the UK. This research was supported by the General Research Fund from the Hong Kong Research Grants Council.
香港大學（港大）研究人員最近就無脊椎動物在森林凋落物降解中的作用進行探究，發現土壤中的無脊椎動物，尤其是白蟻，在熱帶和亞熱帶森林凋落物降解中發揮着重要作用。
生物多樣性受威脅
港大生物科學學院 Louise A ASHTON 教授指出，人類活動如氣候變化、棲息地流失和污染，威脅着無脊椎動物的生物多樣性，「為了保持生態系統的良好運作與健康，減緩生物多樣性的損失刻不容緩」。
該研究由港大生物科學學院博士研究生曾小儀及助理教授 Louise A ASHTON 共同率領。Ashton 教授的團隊分析了來自全球 93 個地點的476 項案例，在此基礎上使用統合分析（Meta-analysis）的方法，來評估森林生態系統之中透過無脊椎動物進行凋落物降解的地區性差異。
研究發現，無脊椎動物對全球森林凋落物分解的貢獻佔 31%，其中熱帶和亞熱帶森林中的土壤無脊椎動物對降解的貢獻是溫帶和寒帶森林的 1.4 倍。在熱帶和亞熱帶地區，較高的白蟻多樣性和溫暖潮濕的氣候提高了無脊椎動物對森林凋落物降解的貢獻度。
能促進森林凋落物降解
此研究指出無脊椎動物在促進全球森林凋落物降解方面的重要性，尤以熱帶和亞熱帶地區為甚，亦突顯了白蟻於養分循環中所擔當的重要角色。
然而，許多人仍然將白蟻視為作物害蟲，並廣泛使用殺蟲劑來減少白蟻數量。鑒於這些地區廣泛的環境變化，保護熱帶和亞熱帶地區的無脊椎動物對於維持生態系統運作實至為重要。
研究提出將無脊椎動物功能整合到地球系統模型（Earth System Model，簡稱 ESM）中的必要性。且由於單一使用殺蟲劑來控制白蟻群或會影響生態系統功能，因此森林管理者有必要考慮保護無脊椎動物族群和促進永續森林管理實踐的保育策略。