In many tropical ecosystems, termites are important ecosystem engineers. Mound-building termite species often contribute to topographical landscape heterogeneity, and the associated accumulation of soil moisture and nutrients affects the spatial distribution of plant communities. Plants that grow next to the termite mound are known to benefit from the provided nutrients and water storage. The other way around, protection against erosion and cooling effects on the microclimate of the mounds imposed by associated trees have been described. However, little is known regarding the influence of tree parameters and the long-term effects on colony development. In an interval of 12 yr, we studied all Macrotermes michaelseni mounds occurring within one square kilometer of Namibian thornbush savanna in terms of morphology, life history, and associated plants, with a focus on the role of associated trees which grow directly adjacent to the termite mounds. Here, we present the results of a combined analysis of the character states recorded at the termite mound and the associated trees. More than 50% of all 345 recorded termite mounds were associated with a tree. Mounds with associated trees showed increased activity, growth, and height. Mound growth within the study period was correlated positively with the canopy coverage by the associated tree, while total mound heights were correlated non-linear with medium canopy coverage of about 40%. Mounds with a tree covering the sun's average zenith (north) were taller, grew most within 12 yr, and were more likely to be active than those with no northern canopy coverage. Mounds associated with the evergreen Boscia albitrunca attained highest average height (195.06 ± 11.76 cm). We conclude that vital parameters like growth, size, and activity of the termite colonies are facilitated by shading associated trees. These benefits were shown to take significant effect within the span of 12 yr. This indicates a proper long-term mutualism, not a loose alliance and not an obligative eu-symbiosis. Therefore, we propose to use the term “partner tree” for trees associated with M. michaelseni mounds.

中文翻译：

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有益的关系：相关树木促进纳米比亚的白蚁群落（Macrotermes michaelseni）

在许多热带生态系统中，白蚁是重要的生态系统工程师。土丘建筑白蚁物种通常有助于地形景观异质性，土壤水分和养分的相关积累影响植物群落的空间分布。众所周知，在白蚁丘附近生长的植物可以从所提供的养分和储水中受益。另一方面，已经描述了相关树木对土丘微气候的侵蚀和冷却效应的保护。然而，关于树木参数的影响和对菌落发育的长期影响知之甚少。在 12 年的时间间隔内，我们研究了所有Macrotermes michaelseni在形态、生活史和相关植物方面，纳米比亚荆棘稀树草原 1 平方公里内出现的土丘，重点关注直接生长在白蚁丘附近的相关树木的作用。在这里，我们展示了对白蚁丘和相关树木记录的特征状态的综合分析结果。在所有 345 个记录的白蚁丘中，超过 50% 与一棵树有关。带有相关树木的土丘显示出活动、生长和高度的增加。研究期间的土丘生长与相关树木的冠层覆盖率呈正相关，而总土丘高度与约 40% 的中等冠层覆盖率呈非线性相关。一棵树覆盖太阳平均天顶（北）的土丘更高，在 12 年内生长最多，并且比那些没有北方冠层覆盖的人更有可能活跃。与常青树有关的土墩Boscia albitrunca达到了最高的平均高度 (195.06 ± 11.76 厘米)。我们得出的结论是，对相关树木进行遮荫有助于促进白蚁群落的生长、大小和活动等重要参数。这些好处在 12 年的时间里显示出显着的效果。这表明适当的长期共生，而不是松散的联盟，也不是强制性的欧盟共生。因此，我们建议对与M. michaelseni丘相关的树木使用术语“伙伴树” 。