The Forest School, School of the Environment, Yale University, New Haven, Connecticut, 06511, USA.
Melbourne School of Design, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Ecol Appl. 2021 Jul;31(5):e02336. doi: 10.1002/eap.2336. Epub 2021 May 12.
As urbanization increases worldwide, investments in nature-based solutions that aim to mitigate urban stressors and counter the impacts of global climate change are also on the rise. Tree planting on degraded urban lands-or afforestation-is one form of nature-based solution that has been increasingly implemented in cities around the world. The benefits of afforestation are, however, contingent on the capacity of soils to support the growth of planted trees, which poses a challenge in some urban settings where unfavorable soil conditions limit tree performance. Soil-focused site treatments could help urban areas overcome impediments to afforestation, yet few studies have examined the long-term (>5 yr) effects of site treatments on soils and other management objectives. We analyzed the impacts of compost amendments, interplanting with shrubs, and tree species composition (six species vs. two species) on soil conditions and associated tree growth in 54 experimental afforestation plots in New York City, USA. We compared baseline soil conditions to conditions after 6 yr and examined changes in the treatment effects from 1 to 6 yr. Site treatments and tree planting increased soil microbial biomass, water holding capacity, and total carbon and nitrogen, and reduced soil pH and bulk density relative to baseline conditions. These changes were most pronounced in compost-amended plots, and the effects of the shrub and species composition treatments were minimal. In fact, compost was key to sustaining long-term changes in soil carbon stocks, which increased by 17% in compost-amended plots but declined in unamended plots. Plots amended with compost also had 59% more nitrogen than unamended plots, which was associated with a 20% increase in the basal area of planted trees. Improvements in soil conditions after 6 yr departed from the initial trends observed after 1 yr, highlighting the importance of longer-term studies to quantify restoration success. Altogether, our results show that site treatments and tree planting can have long-lasting impacts on soil conditions and that these changes can support multiple urban land management objectives.
随着全球城市化的不断推进，旨在减轻城市压力源和应对全球气候变化影响的基于自然的解决方案的投资也在不断增加。在退化的城市土地上植树造林（或造林）是一种越来越多地在世界各地城市实施的基于自然的解决方案。然而，造林的好处取决于土壤支持种植树木生长的能力，而在一些城市环境中，不利的土壤条件限制了树木的生长。以土壤为重点的场地处理可以帮助城市地区克服造林的障碍，但很少有研究考察场地处理对土壤和其他管理目标的长期（> 5 年）影响。我们分析了堆肥改良、与灌木间作和树种组成（6 个树种与 2 个树种）对美国纽约市 54 个实验造林地块土壤条件和相关树木生长的影响。我们将基线土壤条件与 6 年后的条件进行了比较，并检查了从 1 年到 6 年处理效果的变化。与基线条件相比，场地处理和植树造林增加了土壤微生物生物量、持水能力和总碳氮含量，降低了土壤 pH 值和容重。这些变化在堆肥改良的地块中最为明显，而灌木和树种组成处理的效果则微不足道。事实上，堆肥是维持土壤碳储量长期变化的关键，堆肥改良的地块中土壤碳储量增加了 17%，而未改良的地块则减少了。堆肥改良的地块的氮含量也比未改良的地块多 59%，这与种植树木的基面积增加 20%有关。6 年后土壤条件的改善偏离了 1 年后观察到的初始趋势，这突出了进行长期研究以量化恢复成功的重要性。总之，我们的结果表明，场地处理和植树造林对土壤条件具有持久的影响，这些变化可以支持多种城市土地管理目标。
