Collaborative Research: Effects of top scavenger declines—from microbes to ecosystems

除非首先被捕食者吃掉，否则所有动物死后都会进入腐肉池。食腐动物和微生物在将尸体来源的营养物质返回土壤中发挥着关键作用，在土壤中它们被循环利用，用于植物的吸收和生长。腐肉输入对养分循环、食物网动态和生态系统碳平衡的影响仍然是一个谜。随着包括食腐动物在内的许多物种的全球减少，量化腐肉来源营养物质的数量和质量如何影响植物群落结构和生态系统动态是至关重要的。袋獾是研究食腐对生态系统过程影响的理想和有魅力的物种。它们是世界上为数不多的吃骨头的食肉动物之一。通过加速关键植物生长限制营养物质的循环，袋獾提供了一个关键的生态系统功能，否则这些营养物质将被锁在骨骼材料中多年。近年来，一种高度传染性的癌症——魔鬼面部肿瘤病（DFTD）的出现，极大地减少了塔斯马尼亚东部的魔鬼种群规模，并蔓延到整个岛屿，威胁着这个标志性物种的灭绝。研究人员将利用这一悲惨的情况来测试是否可以在生态系统规模上检测到魔鬼的清除影响，以及魔鬼数量的减少如何导致其他清除物种的角色转变。该项目将为美国研究生和博士后学者提供国际培训机会。通过教育和推广活动，研究人员将强调食腐动物、生物多样性和生态系统恢复能力之间存在的联系。很少有研究直接调查非植物输入对食物网内能量转移的影响。因此，在了解腐肉和食腐动物行会如何在生态系统尺度上控制生物地球化学循环方面存在相当大的知识差距。在塔斯马尼亚，一种致命的、可传播的癌症DFTD从东向西传播，威胁着魔鬼的灭绝，并在整个岛屿上造成了人口密度梯度（从0%到100%的承载能力）。由此产生的“自然实验”提供了一个难得的机会来研究顶端食腐动物的衰退如何改变食物网中的能量转移以及腐肉、土壤和植物中的养分流动。将在跨越DFTD梯度的五个研究地点建立高频监测和采样站，并捕获四种实验处理：(1)全清道夫通道（桩置猎物尸体）；(2)魔鬼隔离（将猎物的尸体围起来，允许除魔鬼外的所有食腐动物进入）；(3)重建魔鬼厕所，从局部粪便中捕获营养脉冲；(4)和土壤控制监测背景C和养分有效性。将使用相机阵列估计尸体上的魔鬼和中型捕食者密度；利用适当的捕虫器评估无脊椎动物的密度。稳定同位素示踪将用于跟踪尸体来源的养分如何影响微生物群落多样性和土壤碳形成。植物生产力（NPP）、叶片质量、幼苗招募和细根生物量将在每个站点和整个大陆DFTD梯度上进行估算。利用魔鬼数量减少的程度和时间的时空变化，将采用一系列规模实验：(1)确定清除者密度的变化如何影响当地土壤生物地球化学；(2)研究腐肉和腐食网络如何引起微生物群落代谢效率和新植物凋落物分解速率的变化；(3)检测魔鬼的食腐程度；(4)综合野外和室内实验结果，预测未来50年生物多样性丧失对生态系统功能的影响。该项目将支持一个由早期职业女性科学家领导的团队，涉及国际合作，并提供研究生和博士后水平的培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Unless first consumed by a predator, all animals enter the carrion pool when they die. Scavengers and microorganisms play a critical role in returning carcass-derived nutrients to the soil where they get recycled and used for plant uptake and growth. The impact of carrion inputs on nutrient cycling, food web dynamics, and ecosystem carbon balance remains a mystery. With global declines of many species including scavengers, it is essential to quantify how the quantity and quality of carrion-derived nutrients shapes plant community structure and ecosystem dynamics. Tasmanian devils are an ideal and charismatic species with which to study the effects of scavenging on ecosystem processes. They are one of a few carnivores worldwide that consume bones. By accelerating the cycling of key plant growth-limiting nutrients that would otherwise remain locked in bone material for years, Tasmanian devils provide a critical ecosystem function. In recent years, the emergence of a highly transmissible cancer — devil facial tumor disease, or DFTD — has dramatically reduced devil population sizes in eastern Tasmania and has spread throughout the island, threatening this iconic species with extinction. Researchers will use this tragic situation to test whether devil-scavenging impacts can be detected on an ecosystem scale and how devil population declines result in a shift in the role of other scavenger species. This project will provide training opportunities for US graduate students and post-doctoral scholars in an international setting. Through education and outreach activities, researchers will highlight the linkages that exist between scavengers, biodiversity, and ecosystem resiliency. Few studies have directly investigated the effects of non-plant inputs on energy transfer within food web networks. As a result, there is a considerable knowledge gap in understanding how carrion and scavenger guilds govern biogeochemical cycling at an ecosystem scale. In Tasmania, the east to west spread of DFTD, a lethal, transmissible cancer, threatens devils with extinction and has created a population density gradient across the island (from 0% to 100% of carrying capacity). The resulting 'natural experiment' offers a rare opportunity to study how apex scavenger declines alter energy transfer within food webs and nutrient flows through carrion, soils, and plants. High-frequency monitoring and sampling stations will be established at five study sites that span the DFTD gradient and capture four experimental treatments: (1) full scavenger access (staked prey carcass); (2) devil exclusion (fenced prey carcass allowing access to all scavengers but devils); (3) reconstructed devil latrines to capture nutrient pulses from localized scat; (4) and soil-only controls to monitor background C and nutrient availability. Devil and mesopredator densities at carcasses will be estimated using camera arrays; invertebrate densities will be assessed using appropriate insect traps. Stable isotope tracing will be used to track how carcass-derived nutrients influence microbial community diversity and soil carbon formation. Plant productivity (NPP), leaf quality, seedling recruitment, and fine root biomass will be estimated at each site and across the continental DFTD gradient. Using temporal and spatial variation in the extent and timing of devil population declines, a series of scaled experiments will be used to: (1) determine how variation in scavenger densities affects local soil biogeochemistry; (2) investigate how carrion and scavenging networks induce shifts in the metabolic efficiency of microbial communities and decomposition rates of new plant litter inputs; (3) test the scale at which scavenging by devils is detectable; and (4) integrate findings from field and laboratory experiments to predict how biodiversity loss will affect ecosystem function over the next 50 years. The project will support a team led by an early-career female scientist, involve international collaboration and provide training at the graduate student and postdoctoral levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.