Nutrient enrichment, biodiversity loss, and consequent declines in ecosystem productivity
Nutrient enrichment, biodiversity loss, and consequent declines in ecosystem productivity
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DOI：
10.1073/pnas.1310880110
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发表时间：
2013-07-16
影响因子：
11.1
通讯作者：
Binder, Seth
中科院分区：
文献类型：
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作者：
Isbell, Forest;Reich, Peter B.;Binder, Seth
环境变化的人为驱动因素往往具有多重影响，包括生物多样性、物种组成和生态系统功能的变化。生物多样性和物种组成的这种变化本身是否可能是人为驱动因素对生态系统功能的总体长期影响的主要促成因素，目前仍不清楚。此外，尽管许多实验表明，物种的随机损失会影响生态系统的功能，但人类造成的生物多样性损失很少是随机的。在这里，我们使用的结果，从长期的草地田间试验，以测试长期营养富集对生态系统生产力的直接影响，以及由此产生的物种损失介导的生产力富集的间接影响。我们发现，随着时间的推移，生态系统生产力下降最多的地块，失去了最多的物种。慢性氮添加也导致了最初占主导地位的本地多年生C-4草的非随机损失。在附近的生物多样性实验中，这种优势植物物种的损失与每个物种损失的生产力损失相比，是随机物种损失的两倍。因此，虽然长期的氮富集最初提高了生产力，但它也导致了植物物种的损失，包括最初的优势物种，然后导致氮肥的回报大幅减少。相比之下，CO2浓度升高并没有减少草地植物多样性，而且随着时间的推移，它始终促进生产力。我们的研究结果支持这一假设，即环境变化的人为驱动因素对生态系统功能的长期影响在很大程度上取决于这些驱动因素如何逐渐减少生物多样性和重建社区。
Anthropogenic drivers of environmental change often have multiple effects, including changes in biodiversity, species composition, and ecosystem functioning. It remains unknown whether such shifts in biodiversity and species composition may, themselves, be major contributors to the total, long-term impacts of anthropogenic drivers on ecosystem functioning. Moreover, although numerous experiments have shown that random losses of species impact the functioning of ecosystems, human-caused losses of biodiversity are rarely random. Here we use results from long-term grassland field experiments to test for direct effects of chronic nutrient enrichment on ecosystem productivity, and for indirect effects of enrichment on productivity mediated by resultant species losses. We found that ecosystem productivity decreased through time most in plots that lost the most species. Chronic nitrogen addition also led to the nonrandom loss of initially dominant native perennial C-4 grasses. This loss of dominant plant species was associated with twice as great a loss of productivity per lost species than occurred with random species loss in a nearby biodiversity experiment. Thus, although chronic nitrogen enrichment initially increased productivity, it also led to loss of plant species, including initially dominant species, which then caused substantial diminishing returns from nitrogen fertilization. In contrast, elevated CO2 did not decrease grassland plant diversity, and it consistently promoted productivity over time. Our results support the hypothesis that the long-term impacts of anthropogenic drivers of environmental change on ecosystem functioning can strongly depend on how such drivers gradually decrease biodiversity and restructure communities.