Incubation mound-building by the Australian megapode (Malleefowl, Leipoa ocellata) creates novel, resource-rich patches in a semi-arid woodland

Desert ecosystems are characterised by a patchy distribution of resources. Nutrient sinks associated with landscape modulators (trees) differ markedly from the resource-poor interpatch matrix. Fauna can also act as landscape modulators, modifying patch dynamics by redistributing resources via 'ecosystem engineering’. In semi-arid woodlands, malleefowl (Leipoa ocellata: Megapodiidae) reconfigure surface characteristics by scavenging leaf litter to construct large incubation mounds. The extent to which this movement of resources creates a novel patch and alters extant patches is largely unknown. Ecosystem engineering effects by megapodes have been little studied, but are potentially great, particularly in drylands, where mammalian engineers are known to enhance ecosystem function and drive restoration. We measured vegetation, ground cover, and soil chemistry at malleefowl mounds and four extant microsites (trees and open areas close to, and far from, mounds) and predicted that: 1) malleefowl mounds would represent enriched, yet novel, microsites; 2) the characteristics of tree and open patches close to the mounds would differ from those away from the mounds, because of the diminishing intensity of disturbance; and 3) effects at tree and open patches close to the mound would be shorter-term, compared to the more substantial high-resource patch formation occurring at the mound, but we expected all effects would diminish with time since malleefowl activity. We found that: 1) malleefowl mounds were novel microsites with soil chemistry more similar to tree-modulated patches, and groundcover and vegetation variables more similar to the open, interpatch matrix; 2) effects extended to tree and open patches near the mound, but most effects were short lived; and 3) some novel mound attributes (e.g., soil pH, phosphorus, nitrogen, carbon) were greater at mounds, irrespective of their age, while less plant cover and richness on young mounds dissipated with age. Synthesis: Mound-building megapodes can modulate the distribution of locally derived resources and create a novel microsite. Engineering effects can enhance spatial heterogeneity and ecosystem function over broad spatial and temporal scales, and may assist with ecological restoration, particularly in depauperate, arid systems.荒漠生态系统以资源的斑块状分布为典型特征。与景观调节因子（树木）相关的养分汇，与资源匮乏的斑块间基质存在显著差异。动物亦可作为景观调节因子，通过“生态系统工程（ecosystem engineering）”手段重新分配资源，进而改变斑块动态。在半干旱林地中，眼斑冢雉（Leipoa ocellata: Megapodiidae）会通过收集枯落叶构筑大型孵化冢，以此改造地表特征。目前学界对该类资源转移所形成的新型斑块，以及其对现存斑块的改造程度仍知之甚少。冢雉类的生态系统工程效应鲜有研究，但其潜在影响巨大，尤其是在干旱地区——已知该区域的哺乳动物工程因子可提升生态系统功能并推动生态修复。本研究针对眼斑冢雉的孵化冢，以及四类现存微生境（即孵化冢附近与远处的树木区、开阔区）开展了植被、地表覆盖及土壤化学性质的测定，并提出如下三项假设：1. 眼斑冢雉孵化冢将构成养分富集且全新的微生境；2. 由于干扰强度随距离增加而减弱，孵化冢附近的树木区与开阔斑块的特征，将与远离孵化冢的同类斑块存在差异；3. 相较于孵化冢处形成的高资源丰度大型斑块，孵化冢附近的树木区与开阔斑块所受的工程效应持续时间更短；但我们推测，所有工程效应均会随眼斑冢雉活动停止后的时间推移而逐渐减弱。本研究结果显示：1. 眼斑冢雉孵化冢属于全新微生境：其土壤化学特征与树木调控的斑块更为接近，而地表覆盖与植被变量则更贴近开阔的斑块间基质；2. 工程效应可延伸至孵化冢附近的树木区与开阔斑块，但多数效应的持续时间较短；3. 部分孵化冢的特有属性（如土壤pH值、磷、氮、碳含量）无论冢龄长短均保持较高水平，而年轻冢上较低的植物覆盖度与物种丰富度则随时间推移逐渐消失。研究总结：筑冢冢雉类可调控本地源资源的分布，并构建全新的微生境；其工程效应可在广泛的时空尺度上提升空间异质性与生态系统功能，或可助力生态修复，尤其在贫瘠的干旱生态系统中效果显著。