WSL Swiss Federal Research Institute, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland.
Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012, Bern, Switzerland.
J Environ Manage. 2021 Feb 1;279:111629. doi: 10.1016/j.jenvman.2020.111629. Epub 2020 Nov 10.
Land-use intensification is a major threat to biodiversity in agricultural grasslands and fertilization is one of the main drivers. The effects of fertilization on biodiversity and plant functional composition (community-weighted mean traits and mean ecological indicator values) are well studied in lowland regions, but have received less attention in mountain grasslands. Moreover, in inner-alpine dry valleys, fertilizer is often applied in combination with irrigation, and irrigation effects are less well known. We experimentally tested the effects of fertilization and irrigation on vascular plant species richness and the functional composition of mountain grasslands in the Swiss Alps. After five years, fertilization increased yield but the relationship was quadratic with maximum yield reached at intermediate fertilizer levels (58 kg N hayear). The species richness of all vascular plants and forbs decreased, on average, by 6 and 5 species respectively, per 50 kg N of extra fertilizer (ha year) applied. Fertilization also favored fast-growing plants (increased mean specific leaf area) and plants typically found in productive environments (increased mean indicator values for soil productivity and moisture). In contrast, we found no effects of irrigation on plant community composition, which suggests that irrigation does not affect vascular plant diversity to the same extent as fertilization in these mesic mountain hay meadows, at least in the mid-term. Our finding that maximum yield can be achieved at intermediate fertilizer levels is very important from an applied, agronomical and conservation point of view. It suggests that without loss of yield, farming costs and at the same time environmental pollution and negative effects on biodiversity can be reduced by applying less fertilizer. We therefore recommend maintaining non-intensive land use and keeping fertilizer inputs as low as possible to maintain the high plant diversity of mountain grasslands.
土地利用集约化是农业草原生物多样性的主要威胁，施肥是主要驱动因素之一。施肥对低地地区生物多样性和植物功能组成（群落加权平均特征和平均生态指标值）的影响已经得到了很好的研究，但在山地草原中却受到了较少的关注。此外，在内陆高山干旱河谷中，肥料通常与灌溉结合使用，而灌溉的影响则不太为人所知。我们在瑞士阿尔卑斯山的实验中测试了施肥和灌溉对山地草原维管束植物物种丰富度和功能组成的影响。经过五年的时间，施肥增加了产量，但呈二次曲线关系，在中等施肥水平（58kgN/ha/year）下达到最大值。所有维管束植物和杂类草的物种丰富度平均每公顷额外施 50kgN 肥料（ha/year）分别减少了 6 种和 5 种。施肥还有利于生长速度较快的植物（增加平均比叶面积）和通常在生产力环境中发现的植物（增加土壤生产力和水分的平均指标值）。相比之下，我们没有发现灌溉对植物群落组成的影响，这表明在这些湿润的山地干草草地中，至少在中期，灌溉对维管束植物多样性的影响不如施肥大。从应用、农艺和保护的角度来看，我们发现最大产量可以在中等施肥水平下实现，这一点非常重要。这表明，在不降低产量的情况下，可以通过减少施肥来降低农业成本，同时减少环境污染和对生物多样性的负面影响。因此，我们建议保持非集约化土地利用，并尽可能减少肥料投入，以维持山地草原的高植物多样性。
