Changes in canopy structures caused by harvesting and regeneration practices can significantly alter the wind environment. Therefore, it is essential to understand the wind patterns influenced by seed tree arrangements for predicting seed dispersal by winds and ensuring the success of natural regeneration. This study aimed to identify how wind speed responds to seed tree arrangement designs with differing horizontal distances, vertical positions, and free-stream wind speeds. A wind tunnel test was conducted using pine saplings for a scale model of various seed tree arrangements, and the change in wake speed was tracked. The wake’s relative wind speed averaged 71%, ranging from 3.5% to 108.5%, depending on the seed tree arrangement, distance from saplings, and vertical position. It peaked within the patch of three seed trees compared to other arrangements and at the top canopy layer. The empirical function effectively described the wind speed reduction and recovery with distance from saplings. For instance, the minimum wind speed was reached at 0.6–2.2 times the canopy height, and a wind speed reduction of over 20% of the free-stream wind speed was maintained at a 1.6–7.6 canopy height. A negative relationship between the seed tree leaf area and the relative wind speed was observed only at the top canopy layer. This study presents empirical evidence on the patterns of wake winds induced by different types of heterogeneous canopy structures.

The quantification of urban tree biomass allocation has primarily relied on estimations using allometric equations (AEs) developed for nondestructive harvest methods. However, the lack of harvest-based AEs that account for belowground biomass, nutrient concentration, and annual growth rates poses challenges in accurately quantifying the greenhouse gas inventory for urban land uses. In this study, we aimed to develop AEs using a log-transformed linear model for eight urban landscaping tree species, taking into account belowground biomass. We purchased 117 urban landscaping trees from tree farms in South Korea and investigated their biomass fractions, carbon and nutrient concentrations, and annual growth rate using a destructive method. We also developed AEs for different tree compartments using diameter at breast height as an independent variable. The AEs obtained exhibited high suitability, as evidenced by their high R² values (0.853–0.982 and 0.806–0.923 for aboveground and belowground biomass, respectively). The mean belowground biomass fraction across the different species was approximately 30%, suggesting that urban trees could allocate more belowground biomass than forest trees. Conversely, carbon and nitrogen concentrations varied significantly across species and compartments, and the mean annual carbon sequestration rate was 3.96 kg C year⁻¹ tree⁻¹. Therefore, the application of the AEs for urban trees may enhance the accuracy of the national greenhouse gas inventory for the settlement sector.

Urban trees grow in diverse environments where site conditions and human management may influence their growth patterns. However, few allometric equations (AEs) have been developed for urban trees, and the effects of environmental variations across urban land use categories on tree biomass remain largely unexplored. Therefore, this study developed urban land-use-specific AEs for major urban tree species in South Korea. We selected eight major urban tree species groups (at genus level), harvested 201 trees, and non-destructively measured the stem volumes of 1995 trees using a laser dendrometer. Species-specific and generalized AEs to estimate stem volume were developed under three urban land use categories: street trees, urban parks, and others. The results indicated that differences in stem volume across urban land use categories varied by species, with street trees generally showing smaller stem volumes. Furthermore, due to the high variation in stem volume within species, sampling designs that encompass diverse size distributions are necessary when developing AEs for urban trees. Our findings indicate that various factors in urban environments influence tree volume and considering these differences is essential for improving biomass estimation accuracy.

The national level carbon sequestration estimation for urban trees generally relies on diameter at breast height (DBH) increments. However, limited research on urban tree growth has led to uncertain estimates. In this study, we determined the DBH increment of six major urban tree species in South Korea using three analytical methods (mean, linear regression, and generalized additive model) and two data classifications (total and segmented). Additionally, wedeterminded the aboveground woody biomass (AGWB) increment, which was calculated using the estimated DBH increment, and the accuracy of the estimates using different methods. We found wide variations in DBH increment (0.616 to 1.002 cm yr⁻¹) among the assessed tree species. Metasequoia glyptostroboides exhibited the highest mean growth, while Pinus densiflora showed the lowest. The peak DBH increment occurred at a median of 25.4 cm for Quercus spp. and 40.0 cm for Prunus yedoensis. The total mean method led to overestimations of AGWB increment, especially for the largest trees (i.e., those in the top 5% of DBH). Our study suggests that relying on a simple total mean method can lead to significant uncertainties in estimating AGWB increment. Therefore, more accurate methods for estimating DBH increment, especially in urban environments, are needed.