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Ecological connectivity in the three-dimensional urban green volume using waveform airborne lidar

View Article: PubMed Central - PubMed

ABSTRACT

The movements of organisms and the resultant flows of ecosystem services are strongly shaped by landscape connectivity. Studies of urban ecosystems have relied on two-dimensional (2D) measures of greenspace structure to calculate connectivity. It is now possible to explore three-dimensional (3D) connectivity in urban vegetation using waveform lidar technology that measures the full 3D structure of the canopy. Making use of this technology, here we evaluate urban greenspace 3D connectivity, taking into account the full vertical stratification of the vegetation. Using three towns in southern England, UK, all with varying greenspace structures, we describe and compare the structural and functional connectivity using both traditional 2D greenspace models and waveform lidar-generated vegetation strata (namely, grass, shrubs and trees). Measures of connectivity derived from 3D greenspace are lower than those derived from 2D models, as the latter assumes that all vertical vegetation strata are connected, which is rarely true. Fragmented landscapes that have more complex 3D vegetation showed greater functional connectivity and we found highest 2D to 3D functional connectivity biases for short dispersal capacities of organisms (6 m to 16 m). These findings are particularly pertinent in urban systems where the distribution of greenspace is critical for delivery of ecosystem services.

No MeSH data available.


Related in: MedlinePlus

Structural connectivity parameters for different connectivity metrics for the three towns derived from analysis of different 3D structural layers (coloured bars) and 2D green cover (grey).(a) Proportion of green surface cover - where higher values of the landscape proportion parameter represent greater overall amounts of green cover; (b) fragmentation of green patches <30 m2 – where higher values of the small patch index parameter correspond to a more fragmented landscape; (c) core area cover – where higher values of the largest patch index parameter correspond to a higher percentage of the landscape comprised of the largest greenspace patch; (d) CI or the probability that two random chosen locations in a green surface are not connected – where the higher CI parameter corresponds to a lower overall spatial connectivity.
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f2: Structural connectivity parameters for different connectivity metrics for the three towns derived from analysis of different 3D structural layers (coloured bars) and 2D green cover (grey).(a) Proportion of green surface cover - where higher values of the landscape proportion parameter represent greater overall amounts of green cover; (b) fragmentation of green patches <30 m2 – where higher values of the small patch index parameter correspond to a more fragmented landscape; (c) core area cover – where higher values of the largest patch index parameter correspond to a higher percentage of the landscape comprised of the largest greenspace patch; (d) CI or the probability that two random chosen locations in a green surface are not connected – where the higher CI parameter corresponds to a lower overall spatial connectivity.

Mentions: When comparing the 3D derived strata and 2D analysis, the structural connectivity measures varied as shown in Fig. 2. Key patterns and distinctions as found for all three towns were: (i) 2D metrics indicated a greener landscape than 3D derived strata (Fig. 2a shows a higher percentage of green landscape in 2D than in any of the 3D derived strata); (ii) 2D metrics indicated a less fragmented landscape than 3D derived strata (Fig. 2b shows a higher density of patches smaller than 30 m2); (iii) A wider core connected zone was indicated from 2D data as compared to 3D derived strata, as a proportion of the overall area (Fig. 2c shows the largest patch index in the 2D analysis); (iv) A more connected 2D surface as compared to the 3D derived strata (Fig. 2d shows lower CI values from 2D analysis implying higher structural connectivity) - according to 2D metrics, Bedford had the highest structural connectivity (Fig. 2d).


Ecological connectivity in the three-dimensional urban green volume using waveform airborne lidar
Structural connectivity parameters for different connectivity metrics for the three towns derived from analysis of different 3D structural layers (coloured bars) and 2D green cover (grey).(a) Proportion of green surface cover - where higher values of the landscape proportion parameter represent greater overall amounts of green cover; (b) fragmentation of green patches <30 m2 – where higher values of the small patch index parameter correspond to a more fragmented landscape; (c) core area cover – where higher values of the largest patch index parameter correspond to a higher percentage of the landscape comprised of the largest greenspace patch; (d) CI or the probability that two random chosen locations in a green surface are not connected – where the higher CI parameter corresponds to a lower overall spatial connectivity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382541&req=5

f2: Structural connectivity parameters for different connectivity metrics for the three towns derived from analysis of different 3D structural layers (coloured bars) and 2D green cover (grey).(a) Proportion of green surface cover - where higher values of the landscape proportion parameter represent greater overall amounts of green cover; (b) fragmentation of green patches <30 m2 – where higher values of the small patch index parameter correspond to a more fragmented landscape; (c) core area cover – where higher values of the largest patch index parameter correspond to a higher percentage of the landscape comprised of the largest greenspace patch; (d) CI or the probability that two random chosen locations in a green surface are not connected – where the higher CI parameter corresponds to a lower overall spatial connectivity.
Mentions: When comparing the 3D derived strata and 2D analysis, the structural connectivity measures varied as shown in Fig. 2. Key patterns and distinctions as found for all three towns were: (i) 2D metrics indicated a greener landscape than 3D derived strata (Fig. 2a shows a higher percentage of green landscape in 2D than in any of the 3D derived strata); (ii) 2D metrics indicated a less fragmented landscape than 3D derived strata (Fig. 2b shows a higher density of patches smaller than 30 m2); (iii) A wider core connected zone was indicated from 2D data as compared to 3D derived strata, as a proportion of the overall area (Fig. 2c shows the largest patch index in the 2D analysis); (iv) A more connected 2D surface as compared to the 3D derived strata (Fig. 2d shows lower CI values from 2D analysis implying higher structural connectivity) - according to 2D metrics, Bedford had the highest structural connectivity (Fig. 2d).

View Article: PubMed Central - PubMed

ABSTRACT

The movements of organisms and the resultant flows of ecosystem services are strongly shaped by landscape connectivity. Studies of urban ecosystems have relied on two-dimensional (2D) measures of greenspace structure to calculate connectivity. It is now possible to explore three-dimensional (3D) connectivity in urban vegetation using waveform lidar technology that measures the full 3D structure of the canopy. Making use of this technology, here we evaluate urban greenspace 3D connectivity, taking into account the full vertical stratification of the vegetation. Using three towns in southern England, UK, all with varying greenspace structures, we describe and compare the structural and functional connectivity using both traditional 2D greenspace models and waveform lidar-generated vegetation strata (namely, grass, shrubs and trees). Measures of connectivity derived from 3D greenspace are lower than those derived from 2D models, as the latter assumes that all vertical vegetation strata are connected, which is rarely true. Fragmented landscapes that have more complex 3D vegetation showed greater functional connectivity and we found highest 2D to 3D functional connectivity biases for short dispersal capacities of organisms (6&thinsp;m to 16&thinsp;m). These findings are particularly pertinent in urban systems where the distribution of greenspace is critical for delivery of ecosystem services.

No MeSH data available.


Related in: MedlinePlus