Grazing impacts on experimentally restored aquatic macrophytes as critical habitat for the threatened Australian lungfish.

IF 8 2区 环境科学与生态学 Q1 ENVIRONMENTAL SCIENCES
Colin L Burke, Luke Carpenter-Bundhoo, David T Roberts, César Herrera, Hannah M Franklin, Mark J Kennard
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引用次数: 0

Abstract

Aquatic macrophytes, especially Vallisneria nana, provide essential spawning habitat and food resources for the threatened Australian lungfish (Neoceratodus forsteri). The availability of V. nana for lungfish has been dramatically reduced in some areas due to flood disturbances and macrophyte recovery is inhibited by reduced hydrochory due to river fragmentation by dams. Active transplanting of macrophytes may be a feasible restoration strategy to increase abundance of macrophytes, however, in the presence of macro-herbivorous aquatic animals, replanted beds may not persist due to intensive grazing. In this study, we analyzed the effects of environmental conditions on growth and expansion of transplanted V. nana in six 60 m2 herbivore exclosures in the mid-Brisbane River in subtropical south-east Queensland. Following establishment, we also quantified the impact of aquatic herbivores on different patch sizes (15 m2 or 45 m2) of restored V. nana to test the hypothesis that larger patch sizes may confer greater resistance to grazing using a paired control/treatment design. After initial planting, V. nana grew and spread rapidly throughout the exclosure plots, with mean % cover increasing from 5% to 71% on average and mean leaf length increasing from 20 cm to 54 cm on average over 161 days. Transplanted V. nana cover was significantly positively associated with water depth and finer substrate sizes and leaf length was significantly positively associated with water depth and water velocity but was unrelated to substrate size. Exposure to grazing significantly reduced cover of V. nana, however there was no significant effects of macrophyte patch size, grazing intensity, or environmental factors on changes in V. nana cover. Complete removal of exclosure fencing resulted in near complete loss of macrophytes within 7-22 days at all plots, indicating the macrophyte beds (15 m2-60 m2) were of insufficient size to resist grazing pressure. Our findings suggest that transplanting is a viable restoration method with exclusion of grazing, which is critical for creating resistant beds to disturbances and driving future macrophyte recovery. Further research is required to evaluate the feasibility and efficacy of alternative macrophyte restoration strategies in rivers to foster hydrochory and natural regeneration processes following flood disturbance.

放牧对作为濒危澳大利亚肺鱼重要栖息地的试验性恢复水生大型植物的影响。
水生大型藻类,尤其是裸鲤,为濒危的澳大利亚肺鱼(Neoceratodus forsteri)提供了重要的产卵栖息地和食物资源。在一些地区,由于洪水的干扰,肺鱼的 V. nana 数量急剧下降,而大坝造成的河流支离破碎又降低了水文通道,从而抑制了大型水生植物的恢复。积极移植大型水草可能是增加大型水草丰度的可行恢复策略,然而,在大型食草水生动物的存在下,重新种植的水草床可能会因密集的放牧而无法持续。在这项研究中,我们分析了环境条件对昆士兰亚热带东南部布里斯班河中游 6 个 60 平方米食草动物围栏中移植的 V. nana 的生长和扩展的影响。种植后,我们还量化了水生食草动物对不同面积(15 m2 或 45 m2)的裸冠菊恢复植被的影响,通过配对对照/处理设计,验证了较大面积的裸冠菊可能具有更强的抗放牧能力这一假设。在最初种植后,裸冠菊迅速生长并蔓延到整个围栏地块,平均覆盖率从5%增加到71%,平均叶长在161天内从20厘米增加到54厘米。移植的裸冠菊盖度与水深和较细的基质尺寸呈显著正相关,叶长与水深和水速呈显著正相关,但与基质尺寸无关。放牧会明显降低裸冠菊的覆盖率,但大型植物斑块大小、放牧强度或环境因素对裸冠菊覆盖率的变化没有明显影响。完全拆除围栏会导致所有地块的大型植物在 7-22 天内几乎完全消失,这表明大型植物床(15 m2-60 m2)的大小不足以抵御放牧压力。我们的研究结果表明,移植是一种可行的禁牧恢复方法,这对于建立抗干扰性床和推动未来大型植物恢复至关重要。还需要进一步研究,以评估在河流中采用其他大型藻类恢复策略的可行性和有效性,从而在洪水干扰后促进水生和自然再生过程。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Environmental Management
Journal of Environmental Management 环境科学-环境科学
CiteScore
13.70
自引率
5.70%
发文量
2477
审稿时长
84 days
期刊介绍: The Journal of Environmental Management is a journal for the publication of peer reviewed, original research for all aspects of management and the managed use of the environment, both natural and man-made.Critical review articles are also welcome; submission of these is strongly encouraged.
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