Short-Term Growth Dynamics of Spontaneous and Planted Vegetation on Subtropical Extensive Green Roof as Renaturalized Biotope
Abstract
:1. Introduction
2. Materials and Methods
2.1. The Study Site
2.2. A Manicured Extensive Green Roof
2.3. Transforming a Manicured Green Roof into a Biodiverse Habitat
2.4. Vegetation Surveys and Statistical Analysis
3. Results
3.1. Revolution of Planted and Spontaneous Vegetations in Terms of Coverage, Plant Height and Diversity
3.2. Revolution of Planted and Spontaneous Vegetations Grouped under Different Plant Forms
3.3. Species Abundance Distribution
3.4. Seasonal Growth Pattern of Spontaneous Species
4. Discussion
4.1. Single Dominant Species Flourished, While Minorities Diminished, Others Remained Stable
4.2. Annual Herbaceous Vegetation Fluctuated
4.3. Floral Diversity Peaked and Leveled, While Dominant Species Expanded
4.4. Spontaneous Vegetation Being More Resilient than Planted Vegetation
4.5. Medium and Less Abundant Spontaneous and Planted Species Require Attention
4.6. Factors Determining Plant-Growth Patterns on Renaturalized Green Roof
4.7. Management Recommendations for Balancing the Ecological, Aesthetic, and Functional Value of Extensive Green Roof
4.8. Guiding Principles for Choosing and Maintaining Plant Species in Renaturalization Projects
- Landscape designers and managers should communicate the expected appearance of the concerned green roof and the amount and pattern of manpower required thoroughly. Both should understand all traits of the plant species chosen.
- A summary or pictorial guide for all introduced plant species should be available to all landscape managers and frontline gardeners for easy identification, and their means of propagation (e.g., estimated germination rate) and effective removal should be taught.
- If native fern species are planned to be adopted in the renaturalization project, those fern species should be selected with great care to avoid aggressive species undermining biodiversity. Additionally, their mature height should not be underestimated by referencing their sizes in pots in nurseries. Their mature height and size should be compatible with other species to avoid competition for sunshine and resources.
- Annual forb species could be invisible over the winter months and thrive in the summer months. If some of them (e.g., Bidens alba) are too aggressive against other species, they could be problematic to deal with after the seeds are ripe.
- To control the spread and coverage of certain target species in subtropical regions, mowing may not be the best management practice, unlike what was suggested for temperate regions [1]. Total uprooting of the plants is sometimes a practical solution under the constraints of manpower. Understanding the growth cycle and physical structure of plants will help in formulating optimal management strategies.
4.9. Limitations of the Study
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Species | Family | Number of Pots Planted | % | Planting Date | Planting Location | Life-Form Group | Habitat | Survival Rate by the End of Renaturalized Planting (Sep 2014) |
---|---|---|---|---|---|---|---|---|
Adiantum capillus-veneris | Adiantaceae | 8 | 0.77% | May 2013 | South-facing roof | Low-growing fern | Heavy shade, moist rocky cliff | 0% |
Adiantum flabellulatum | Adiantaceae | 2 | 0.19% | May 2013 | South-facing roof | Low-growing fern | Acidic sunny slope | 0% |
Adiatum malesianum | Adiantaceae | 23 | 2.21% | May 2013 | South-facing roof | Low-growing fern | Heavy shade, moist rocky cliff | 0% |
Asplenium prolongatum | Aspleniaceae | 20 | 1.92% | May 2013 | South-facing roof | Low-growing fern | Heavy shade, moist rocky cliff | 0% |
Ctenitis eatonii | Dryopteridaceae | 27 | 2.59% | May 2013 | South-facing roof | Medium height fern | Wet places in forests | 0% |
Cyclosorus parasiticus | Thelypteridaceae | 256 | 24.54% | May 2013; mid-Sep 2013; late Sep 2014 | Both roofs | Tall fern | Forest undergrowth, beside stream | 37.50% |
Desmodium heterocarpon | Fabaceae | 12 | 1.15% | late Sep 2014 | North-facing roof | Creeping forb | Sparse shrubland | 100% |
Elephantopus scaber | Asteraceae | 40 | 3.84% | late Sep 2014 | North-facing roof | Low-growing forb | Sunny open field, roadside | 0% |
Liriope spicata | Liliaceae | 16 | 1.53% | late Sep 2014 | South-facing roof | Medium height forb | Slope, forest undergrowth | 0% |
Macrothelypteris torresiana | Thelypteridaceae | 115 | 11.03% | May 2013; mid-Sep 2013; early and late Sep 2014 | Both roofs | Tall fern | Forest valley | 100% |
Pteris biaurita | Pteridaceae | 22 | 2.11% | May 2013; mid-Sep 2013 | Both roofs | Medium height fern | Forest undergrowth, sunny location | 80% |
Pteris ensiformis | Pteridaceae | 446 | 42.76% | May 2013; mid-Sep 2013; late Sep 2014 | Both roofs | Low-growing fern | Forest undergrowth, sunny location | 100% |
Pteris semipinnata | Pteridaceae | 7 | 0.67% | May 2013; mid-Sep 2013 | Both roofs | Low-growing fern | Forest undergrowth, sunny location | 100% |
Selaginella moellendorffii | Selaginellaceae | 30 | 2.88% | May 2013 | South-facing roof | Low-growing fern | Heavy shade, moist rocky cliff | 0% |
Sphenomeris chinensis | Lindsaeaceae | 19 | 1.82% | May 2013; mid-Sep 2013 | Both roofs | Low-growing fern | Forest margins | 0% |
Oct 2014 | Apr 2015 | Jul 2015 | Nov 2015 | |
---|---|---|---|---|
Shannon–Weiner Diversity Index (H’) | 3.805 | 3.632 | 3.486 | 3.416 |
Pielou’s Evenness Index (J’) | 0.901 | 0.864 | 0.829 | 0.812 |
Smith and Wilson’s Index of Evenness (Evar) | 0.542 | 0.528 | 0.739 | 0.712 |
Number of plant species alive | 68 | 67 | 67 | 67 |
Number of planted species alive | 14 | 14 | 15 | 16 |
Number of spontaneous species alive | 54 | 53 | 52 | 51 |
Number of die-off spontaneous species compared with previous plant survey | -- | 12 | 11 * | 12 |
Number of newly colonized (spontaneous) species compared with previous plant survey | -- | 11 | 5 | 9 |
Number of revived spontaneous species compared with previous plant survey | -- | -- | 6 | 3 |
Cluster Number Shown in Figure 9 | Traits of Cluster | No. of Species | Range of Average Coverage % (Std Dev at Species Level) | Typical Pattern of Coverage % over the Year (14 October, 15 April, 15 July, 15 November) |
---|---|---|---|---|
1 | Dominant, slight decline in summer | 6 | 1.83–1.25% (0.195) | 1.4/2.3/0.9/1.6 |
2 | Thrive in spring, decline over winter | 5 | 1.2–1% (0.083) | 2.2/1/0.8/0.3 |
3 | Sustain over the year, slight decline in winter | 14 | 1.225–0.725% (0.130) | 0.9/0.9/1.1/0.8 |
4 | Decline in spring, regrow in summer | 8 | 0.8–0.5% (0.122) | 1/0.1/1.1/0.4 |
5 | Late colonizer | 14 | 0.775–0.2% (0.183) | 0.2/0.1/0.1/0.9 |
6 | Early colonizers, decline and die off | 8 | 0.58–0.25% (0.125) | 0.9/0.4/0.1/0.1 |
7 | Minority, seasonal | 22 | 0.5–0.025% (0.141) | 0.1/0.3/0.3/0.2 |
Type of Plants with Following Traits | Management Recommendations | Reason(s) | Examples of Plant Species |
---|---|---|---|
Tree and shrub species | Remove all | Damage engineering structure of the extensive green roof | Celtis sinensis, Ficus subpisocarpa, Acacia confusa |
Large-sized forb | Remove all | Shade out shorter plants | Alocasia macrorrhizos |
Tall and/or fast-growing, easily germinated forb, ferns, graminoids | Remove all or most of them (aggressive forbs to be moved before/during flowering) | Shade out shorter plants Adversely affects the aesthetic value | Bidens alba, Laggera alata, Aster subulatus, Cyperus involucratus |
Aggressive and fast spreading forb, ferns, graminoids with tubers | Remove all or most of them | Upset balance of species diversity | Nephrolepis auriculata, Polygonum chinense, Imperata cylindrica var. major |
Mild forb, ferns, graminoids with tubers | Monitor and remove some or all, if necessary | May upset the balance of species diversity if conditions favor their growth | Pteris vittate, Desmodium heterocarpon |
Thick rhizome species/fast-growing geophytes | Remove all | Damage engineering structure of green roof and can slowly spread to form large clumps | Curcuma spp. |
Annual species with suitable mature height (except aggressive ones) | Allow them to self-seed over winter Remove dead stems in spring to early summer (only if dead stems are unaesthetic) | Preserve seed source and mimic the natural environment | Spilanthes paniculata, Drymaria cordata, Eclipta prostrata |
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Law, C.M.Y.; Pan, M.; Sham, Y.T.; Ho, K.C.K. Short-Term Growth Dynamics of Spontaneous and Planted Vegetation on Subtropical Extensive Green Roof as Renaturalized Biotope. Sustainability 2024, 16, 8314. https://doi.org/10.3390/su16198314
Law CMY, Pan M, Sham YT, Ho KCK. Short-Term Growth Dynamics of Spontaneous and Planted Vegetation on Subtropical Extensive Green Roof as Renaturalized Biotope. Sustainability. 2024; 16(19):8314. https://doi.org/10.3390/su16198314
Chicago/Turabian StyleLaw, Caroline Man Yee, Min Pan, Yik Tung Sham, and Kenrick Chun Kiu Ho. 2024. "Short-Term Growth Dynamics of Spontaneous and Planted Vegetation on Subtropical Extensive Green Roof as Renaturalized Biotope" Sustainability 16, no. 19: 8314. https://doi.org/10.3390/su16198314
APA StyleLaw, C. M. Y., Pan, M., Sham, Y. T., & Ho, K. C. K. (2024). Short-Term Growth Dynamics of Spontaneous and Planted Vegetation on Subtropical Extensive Green Roof as Renaturalized Biotope. Sustainability, 16(19), 8314. https://doi.org/10.3390/su16198314