Data from: Ants, fire and bark traits affect how African savanna trees recover following damage

Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating how the inner bark of marula (Sclerocarya birrea), a widespread tree species favoured by elephants, recovers after bark damage. We used a long-term fire experiment in the Kruger National Park to measure bark recovery with and without fire. At 24 months post-damage, mean wound closure was 98, 92, and 72% respectively in annual and biennial burns and fire exclusion treatments. Fire exclusion resulted in higher rates of ant colonisation of bark wounds, and such ant colonisation resulted in significantly lower bark recovery. We also investigated how ten common savanna tree species respond to bark damage and tested for relationships between bark damage, bark recovery and bark traits while accounting for phylogeny. We found phylogenetic signal in bark dry matter content, bark N and bark P, but not in bark thickness. Bark recovery and damage was highest in species which had thick moist inner bark and low wood densities (Anacardiaceae), intermediate in species which had moderate inner bark thickness and wood densities (Fabaceae) and lowest in species which had thin inner bark and high wood densities (Combretaceae). Elephants prefer species with thick, moist inner bark, traits that also appear to result in faster recovery rates.

大象取食造成的树皮损伤在非洲稀树草原树木中极为普遍，后续火灾、昆虫与其他病原体的协同作用往往会导致树木死亡。然而令人意外的是，学界对稀树草原树木如何应对树皮损伤的认知仍极为匮乏。本研究针对这一研究空白展开探究，聚焦深受大象青睐的广布树种马鲁拉树（Sclerocarya birrea），解析其内树皮在遭受损伤后的修复机制。我们依托克鲁格国家公园（Kruger National Park）的长期火灾控制实验，对比测量了存在火灾干扰与无火灾干扰情况下的树皮修复情况。损伤后24个月时，年度火烧、两年火烧以及火烧排除处理组的平均伤口闭合率分别为98%、92%与72%。火烧排除处理组的树皮伤口蚂蚁定植（ant colonisation）率更高，而此类蚂蚁定植会显著降低树皮修复效率。此外，本研究还探究了10种常见稀树草原树木对树皮损伤的响应模式，并在控制系统发育关系的前提下，检验了树皮损伤程度、树皮修复速率与树皮性状之间的关联。研究发现，树皮干物质含量、树皮氮（N）与树皮磷（P）含量存在系统发育信号（phylogenetic signal），而树皮厚度则未表现出该信号。内树皮厚实湿润且木材密度较低的物种（漆树科Anacardiaceae）的树皮损伤程度与修复速率均处于最高水平；内树皮厚度与木材密度适中的物种（豆科Fabaceae）次之；内树皮较薄且木材密度较高的物种（使君子科Combretaceae）则最低。大象更偏好内树皮厚实湿润的树种，而这类性状恰好也能提升树木的树皮修复速率。