Differential effects of vegetation and climate on termite diversity and damage

Species diversity shapes ecosystem services. Despite the advantages that
this relationship has for pest management, few studies have investigated
the links between infrastructure damage (i.e. the percentage amount of
infrastructures infested by termites), species richness and the
environment. Moreover, it is not clear that which proportion of species
richness (total/functional-dominant/common/rare) contributes most to
infrastructure damage. We correlated termite species richness with termite
infestation throughout 83 cities in Zhejiang Province, eastern China.
Species were classified according to whether or not they fed on wood, and
based upon their distributional range, whether they were common or rare.
We analyzed the relative importance and the direct/indirect effects of
climate, vegetation, anthropogenic activities, and the species richness of
four functional categories of termites on the damage levels of eight
infrastructure types in populated (i.e. urban and rural building, green
space and sea wall) and remote areas (i.e. ancient building, large-old
tree, agroforest and reservoir dam). Common species favoured populated
areas, whereas rare species favoured remote areas. Common species, with
preferences for deciduous vegetation, caused more damage to the
infrastructures of populated areas. Rare species, with preferences for
evergreen vegetation, caused more damage in remote areas. Reforestation
project which emphasised evergreen trees increased the number of rare
species but reduced the number of common species. Elevation and drought
risk were positively correlated with rare species richness but neutrally
with common species richness. Structural equation models showed that
vegetation predominantly influenced infrastructure damage in populated
areas via altering common species richness, whereas climate predominantly
and directly influenced infrastructure damage in remote areas. Notably,
elevation and drought risk were positively correlated with infrastructure
damage especially in remote areas. Synthesis and applications. Termites
cause global economic losses of 15~40 billion dollars per year. Our study
reveals that managing city forests and green space, for example increasing
the proportion of evergreen trees, is a sustainable means of suppressing
common termites and thereby reducing infrastructure damage in populated
areas. Conservation strategies, supported by regular inspections, will
become increasingly important as climate change not only threatens the
survival of less harmful rare species, but also increases
infrastructure damage in remote areas.

物种多样性（species diversity）塑造生态系统服务（ecosystem services）。尽管该关系对害虫防治（pest management）具有积极意义，但鲜有研究探讨基础设施损毁（infrastructure damage，即被白蚁（termite）侵染的基础设施占比）、物种丰富度（species richness）与环境之间的关联。此外，尚不清楚哪一类物种丰富度（总/功能优势种/常见种/稀有种）对基础设施损毁的贡献度最高。

本研究针对中国东部浙江省83座城市，对白蚁物种丰富度与白蚁侵染情况进行了相关性分析。研究对象根据其是否以木材为食进行分类，并依据分布范围划分为常见种与稀有种。

本研究分析了气候、植被、人为活动（anthropogenic activities）以及四类白蚁功能类群的物种丰富度，对人口密集区（即城乡建筑、绿地与海堤）和偏远区域（即古建筑、古树（large-old tree）、农林复合系统（agroforest）与水库大坝（reservoir dam））共8类基础设施的损毁程度的相对重要性，以及直接与间接效应。

常见种偏好人口密集区，而稀有种则偏好偏远区域。偏好落叶植被（deciduous vegetation）的常见种会对人口密集区的基础设施造成更严重的损毁；偏好常绿植被（evergreen vegetation）的稀有种则会在偏远区域造成更严重的损毁。

以常绿乔木为核心的造林工程（reforestation project）会提升稀有种的数量，却降低常见种的数量。海拔（elevation）与干旱风险（drought risk）与稀有种丰富度呈正相关，但与常见种丰富度无显著关联。

结构方程模型（structural equation models）分析结果显示，植被主要通过改变常见种丰富度，对人口密集区的基础设施损毁产生影响；而气候则主要且直接地作用于偏远区域的基础设施损毁。值得注意的是，海拔与干旱风险与基础设施损毁呈正相关，这一效应在偏远区域尤为显著。

研究综合与实践应用。白蚁每年在全球范围内造成的经济损失达150~400亿美元。本研究表明，通过调控城市森林与绿地结构（例如提升常绿乔木的占比），可实现抑制常见白蚁种群的可持续目标，进而降低人口密集区的基础设施损毁风险。在气候变化的背景下，低危害性稀种种群生存受到威胁，同时偏远区域的基础设施损毁风险加剧，因此依托定期监测的保护策略将愈发重要。