Long‐term herbivore removal experiments reveal how geese and reindeer shape vegetation and ecosystem CO2 ‐fluxes in high‐ Arctic tundra
Long‐term herbivore removal experiments reveal how geese and reindeer shape vegetation and ecosystem CO2 ‐fluxes in high‐ Arctic tundra
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长期食草动物清除实验揭示了鹅和驯鹿如何塑造高北极苔原的植被和生态系统二氧化碳通量
DOI：
10.1111/1365-2745.14200
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发表时间：
2023
影响因子：
5.5
通讯作者：
Jónsdóttir, Ingibjörg S.
中科院分区：
文献类型：
--
作者：
Petit Bon, Matteo;Hansen, Brage B.;Loonen, Maarten J. J. E.;Petraglia, Alessandro;Bråthen, Kari Anne;Böhner, Hanna;Layton‐Matthews, Kate;Beard, Karen H.;Le Moullec, Mathilde;Jónsdóttir, Ingibjörg S.
鉴于目前的气候变化速度，以及草食动物种群密度的相关变化，了解不同草食动物在生态系统功能中的作用对于预测生态系统响应至关重要。在这里，我们研究了迁徙的鹅和居民，非迁徙的驯鹿--两种主要但功能上截然不同的食草动物--如何在迅速变暖的北极苔原控制植被和生态系统过程。我们在高北极斯瓦尔巴群岛发现的两个最长的、完全重复的食草动物去除实验中收集了植物生长高峰期的植被和生态系统碳（C）通量数据。实验分别在夏季藤壶鹅Branta leucopsis利用的潮湿栖息地和野生驯鹿Rangifer tarandus platyrhynchus全年利用的潮湿-干燥栖息地进行。（只有4 g m− 2活的地上维管植物生物量）到未放牧，以禾本科植物为主（排除4年后为60 g m− 2）和以马尾植物为主（排除15年后为150 g m− 2）的苔原。这导致植被碳和氮（N）库，死亡生物量和苔藓层深度大幅增加。植物氮浓度和CN比率的变化表明，在短期（4年）没有鹅的情况下，植物群落营养动态总体较慢。长期（15年）的鹅迁移增加了生态系统的光合作用而非呼吸作用，使生态系统的碳净固存量（NEE）增加了四倍。排除驯鹿21年也使地上维管植物的活生物量（从50 g m − 2增加到80 g m−2;没有促进植被状态的变化）以及植被的碳和氮库、死生物量、苔藓层深度和呼吸作用显著增加。然而，驯鹿的迁移并没有改变植物和土壤的化学成分或NEE的合成。虽然这两种食草动物都是生态系统结构和功能的关键驱动力，但鹅在其主要栖息地（湿苔原）中的控制作用比驯鹿在其主要栖息地（湿干苔原）中的控制作用要明显得多。重要的是，这些食草动物的影响是规模依赖的，因为鹅在空间上更集中，从而影响了一个较小的部分苔原景观相比，驯鹿。我们的研究结果强调了食草动物如何塑造苔原植被和生态系统过程的实质性异质性，并对正在进行的环境变化产生影响。
Given the current rates of climate change, with associated shifts in herbivore population densities, understanding the role of different herbivores in ecosystem functioning is critical for predicting ecosystem responses. Here, we examined how migratory geese and resident, non‐migratory reindeer—two dominating yet functionally contrasting herbivores—control vegetation and ecosystem processes in rapidly warming Arctic tundra.We collected vegetation and ecosystem carbon (C) flux data at peak plant growing season in the two longest running, fully replicated herbivore removal experiments found in high‐Arctic Svalbard. Experiments had been set up independently in wet habitat utilised by barnacle geeseBranta leucopsisin summer and in moist‐to‐dry habitat utilised by wild reindeerRangifer tarandus platyrhynchusyear‐round.Excluding geese induced vegetation state transitions from heavily grazed, moss‐dominated (only 4 g m−2of live above‐ground vascular plant biomass) to ungrazed, graminoid‐dominated (60 g m−2after 4‐year exclusion) and horsetail‐dominated (150 g m−2after 15‐year exclusion) tundra. This caused large increases in vegetation C and nitrogen (N) pools, dead biomass and moss‐layer depth. Alterations in plant N concentration and CN ratio suggest overall slower plant community nutrient dynamics in the short‐term (4‐year) absence of geese. Long‐term (15‐year) goose removal quadrupled net ecosystem C sequestration (NEE) by increasing ecosystem photosynthesis more than ecosystem respiration (ER).Excluding reindeer for 21 years also produced detectable increases in live above‐ground vascular plant biomass (from 50 to 80 g m−2; without promoting vegetation state shifts), as well as in vegetation C and N pools, dead biomass, moss‐layer depth and ER. Yet, reindeer removal did not alter the chemistry of plants and soil or NEE.Synthesis. Although both herbivores were key drivers of ecosystem structure and function, the control exerted by geese in their main habitat (wet tundra) was much more pronounced than that exerted by reindeer in their main habitat (moist‐to‐dry tundra). Importantly, these herbivore effects are scale dependent, because geese are more spatially concentrated and thereby affect a smaller portion of the tundra landscape compared to reindeer. Our results highlight the substantial heterogeneity in how herbivores shape tundra vegetation and ecosystem processes, with implications for ongoing environmental change.