How Well Do Three Tree Species Adapt to the Urban Environment in Guangdong-Hongkong-Macao Greater Bay Area of China Regarding Their Growth Patterns and Ecosystem Services?

Abstract

It is predicted that global change combined with urbanization will impact increasingly on the society and terrestrial ecosystem in the Guangdong-Hongkong-Macao Greater Bay Area of China (GBA). In this context, the cities in GBA began to plant a variety of urban trees since 2000 which are considered to play an important role in fixing carbon, improving air quality, reducing noise and providing other ecosystem services. However, data on the growth patterns and ecosystem services of the planted trees remains scarce, which hampers a comprehensive understanding of how well the planted trees adapt to the local urban environment. Therefore, we selected three widely planted tree species in Foshan, one of the core cities in GBA and investigated their tree growth and ecosystem services via a harvest campaign and soil analysis. With the same, fast tree growth as natural forests and the greatest above-and below-ground biomass among the three tree species, Ml (Mytilaria laosensis Lec.) showed a distinguished adaption to the local urban environment in terms of growth patterns, carbon fixation, stabilization against typhoon risk and water uptake capacity against potential drought risk in the future. Although Cf (Chinese fir) showed reduced diameter at breast height (DBH) and volume development, it significantly increased the total and available potassium in soils to improve the soil quality. The DBH growth of Sp (Slash pine) decreased between six and 12 years old while it recovered at the age of 12 years, probably suggesting its adaptation might take a longer time. Our results indicated that different trees had different growth patterns and ecosystem services after they were planted in cities. In a harsh urban environment under climate change, precise and comprehensive data on urban trees is necessary, helping to provide different perspectives for urban managers to select appropriate tree species and make policies.

Ecological and Landscape Perspectives on Urban Forest Planning and Construction: A Case Study in Guangdong-HongKong-Macao Greater Bay Area of China

“…Foshan, an inland city in GBA, was famous for its rapidly developing economy, which relied mainly on the manufacturing industry (Lu et al, 2005). As CUA with restricted areas might face both economic and environmental stress, Foshan was transferring part of the industry to SUA and especially UFA (Zhang et al, 2020). Taking into account this phenomenon and becoming a national forest city in 2018 (Zhang et al, 2020), it could be confirmed that Foshan had an increasing demand for forest construction as urban forests were highly expected to provide various ecosystem services such as reducing noise, purifying air quality, and improving environmental quality.…”

“…However, UFA showed the highest diversity and tree species density, implying a recent focus on this area. Furthermore, as CUA and SUA were already occupied with various enterprises, it was necessary to transfer part of the industry to UFA and together with which, the forest construction obtained enhanced investment (Zhang et al, 2020). Hence, to introduce different tree species in CUA and SUA could increase their diversity to optimize the ecosystem services and achieve balanced development between the three areas.…”

“…In the context of rapid urban expansion and global change, GBA is under the increasing pressure of severe environmental challenges and it is essential to take action to ameliorate the adverse effects. Therefore, cities in GBA started to plant a wide variety of trees in the urban area since 2000, aiming to raise the forest cover rates and to improve the urban environmental quality (Zhang et al, 2020). Although most of them have become "national forest cities" with advantages in forest cover rate, whether the constructed urban forests stayed healthy and could develop sustainably were scarcely investigated (Zhang et al, 2018).…”

Evaluation of the growth, adaption, and ecosystem services of two potentially-introduced urban tree species in Guangzhou under drought stress

“…The selection of urban tree species for urban greening should cautiously take tree's adaption to the local environment into account 45,48 . Meanwhile, considering the surge of global change, how well trees responded to extreme climatic events should be profoundly evaluated for their conservation and management in the future 22 . In cities such as Guangzhou with rapid increasing urbanization together with a trend of rising temperature and reduced precipitation, the introduced or selected urban tree species were better to cope with drought positively to avoid high mortality together with economic loss.…”

“…Particularly under drought stress, trees could dynamically adjust their investment in root growth from different perspectives, such as increasing the growth at vertical or horizontal levels, and accelerating root turnover rates 20,21 . For urban trees, the below-ground development patterns could reflect tree's adaption adequately as this could be the most efficient and practical way of coping with harsh surroundings and restricted water supply 22 . Therefore, to evaluate the adaption of two potentially-introduced tree species in Guangzhou, we launched a drought-simulation experiment and measured their above-and below-ground growth, including the development of tree height, diameter in breast height, crown areas, and fine root biomass at different directions.…”