Spatial patterns and drivers of plant diversity in the tropical city of Sanya,China

Drivers of patterns in plant diversity remain poorly understood in tropical cities. Therefore, we investigated diversity within the tropical city of Sanya in Hainan Province of southern China by sampling one to three plots within 154 urban functional units (UFUs) based on six primary and 18 secondary UFUs. To measure diversity, we determined the number of vascular plants (species richness; SR) within each functional unit based on vegetation plots. We computed Faith's phylogenetic diversity (PD_Faith) using a large megatree of plant life. To assess the potential drivers of SR and PD_Faith, we performed multiple regressions using socioeconomic, biophysical, and vegetation management variables. The results showed significant differences in SR and PD_Faith among the six primary UFUs. PD_Faith of cultivated species was significantly higher than PD_Faith of spontaneous species in all UFUs except in the wasteland area. Management measures were better predictors of SR and PD_Faith than socioeconomic variables. The best predictor of SR and PD_Faith of spontaneous species was the management of the urban green space. Our results provide clear guidelines for improved management strategies in Sanya, especially by showing how spontaneous and/or cultivated plant diversity can be encouraged depending on environmental, ecological, and cultural needs. Our work also adds to the presently scarce literature on drivers of urban plant diversity in tropical cities worldwide.     

Plant functional rarity across different land use types in the megacity of Tokyo

The rarity of species has multiple facets. Functional rarity is an integrated index that can quantify species’ sparseness and functional traits’ rarity. However, a comprehensive evaluation of various dimensions of functional rarity at different scales in urban ecosystems is under-researched. Here, we addressed two hypotheses: (1) functional rarity will not be consistent with conventional rarity at local and regional scales, and (2) land use types influence the distribution of all forms of functionally rare plants in urban ecosystems. We first selected ten functional traits to quantify the functional rarity components of 170 plant species. Second, we assessed the distribution of functional rarity and all forms of functionally rare plants across seven land use types in the megacity of Tokyo. We found that functional rarity is not consistent with conventional rarity at the local and regional scales. Several native species and two non-native species were functionally distinct and not scarce at the local scale. In addition, natural remnants and anthropogenic habitats could protect functionally rare species in urban ecosystems. We thus argue for incorporating functional rarity in the current biodiversity conservation framework and considering natural remnants and anthropogenic habitats in urban functionally rare species conservation.     

Effects of historical and present fragmentation on plant species diversity in semi-natural grasslands in Swedish rural landscapes

Habitat loss and fragmentation of natural and semi-natural habitats are considered as major threats to plant species richness. Recently several studies have pinpointed the need to analyse past landscape patterns to understand effects of fragmentation, as the response to landscape change may be slow in many organisms, plants in particular. We compared species richness in continuously grazed and abandoned grasslands in different commonplace rural landscapes in Sweden, and analysed effects of isolation and area in three time-steps (100 and 50 years ago and today). Old cadastral maps and aerial photographs were used to analyse past and present landscape patterns in 25 sites. Two plant diversity measures were investigated; total species richness and species density. During the last 100 years grassland area and connectivity have been reduced by about 90%. Present-day habitat area was positively related to total species richness in both habitats. There was also a relationship to habitat area 50 years ago for continuously grazed grasslands. Only present management was related to species density: continuously grazed grasslands had the highest species density. There were no relationships between grassland connectivity, present or past, and any diversity measure. We conclude that landscape history is not directly important for present-day plant diversity patterns in ordinary landscapes, although past grassland management is a prerequisite for the grassland habitats that can be found there today. It is important that studies are conducted, not only in very diverse landscapes, but also in managed landscapes in order to assess the effects of fragmentation on species.     

The spatiotemporal dynamics of rapid urban growth in the Nanjing metropolitan region of China

To better understand the spatio-temporal dynamics of the urban landscape of the Nanjing metropolitan region, China, we conducted a series of spatial analyses using remotely sensed data of 1979, 1988, 1998, 2000 and 2003. The results showed that the urban area as well as the growth rate increased significantly. Three urban growth types were distinguished: infilling, edge-expansion and spontaneous growth. The pattern of urban growth can be described as a ‘diffusion–coalescence’ phase transition. Although edge-expansion was the most common growth type, the spontaneous growth took a greater proportion in area and patch number than the infilling growth at the early stage, but its dominance decreased as urbanization proceeded from the diffusion phase to the coalescence phase. Hot-zones of urban growth and the distribution pattern of newly urbanized areas in different periods were studied with a buffering analysis. More than 80% of the growth area occurred within a zone of 1.4 km wide outwards from the pre-growth urban fringes. The spatial distribution of newly urbanized areas in each period showed a uniform negative exponential decline relative to the distance from the edge of the urban patches. There existed an outward wave-like shifting of urban growth hot-zones, but the distance-growth area curves varied at different stages of urban growth. While a double-peaked pattern usually occurred in the diffusion phase, a single-peaked pattern was common in the coalescence phase.     

The influence of management history and habitat on plant species richness in a rural hemiboreal landscape,Sweden

We explored patterns of plant species richness at different spatialscales in 14 habitats in a Swedish rural landscape. Effects of physicalconditions, and relationships between species richness and management historyreaching back to the 17^th century were examined, using old cadastralmaps andaerial photographs. The most species-rich habitats were dry open semi-naturalgrasslands, midfield islets and road verges. Alpha diversity (species richnesswithin sites) was highest in habitats on dry substrates (excluding bedrock withsparse pines) and beta diversity (species richness among sites) was highest inmoist to wet habitats. Alpha and beta components of species richness tended tobe inversely related among habitats with similar species richness. Managementhistory influenced diversity patterns. Areas managed as grasslands in the17^th and 18^th century harboured more species than areasoutside the villages. We also found significant relationships between speciesrichness and soil type. Silt proved to be the most species-rich topsoil(10–20 cm) in addition to thin soils top of on green- orlimestone bedrock. The variation in species richness due to local relief orform of thesite also showed significant relationships, where flat surfaces had the highestnumber of species. In contrast, no significant relationship was found betweenspecies richness and aspect. Our study suggests that present-day diversitypatterns are much influenced by management history, and that small habitat,e.g., road verges and midfield islets, are important for maintaining speciesrichness.This revised version was published online in May 2005 with corrections to the Cover Date.     

Contemporary interpretation of the meaning and heritage of early 20th century private gardens: From an historical reflection to a future outlook in planning

This article examines the strategic role played by private gardens in meeting societal challenges in urbanized environments in the late 19th-early 20th century. These gardens represented a means to provide food, a healthier living environment and, by implication, improved living conditions for the growing urban population. This strategic role was embedded in spatial and urban planning policies, as exemplified here in two case studies: the residential area Rostorp, Malmö (Sweden) and the region of Flanders (Belgium). With the case studies’ results as starting point their historical narratives were written. These narratives were then confronted and the cases were qualitatively compared to demonstrate how, over time, the idea and materiality of the private garden have created value and meaning. These values include the strengthening of family values, establishing and maintaining social coherence, sense of place and identity, and creating social space which enabled an exchange of knowledge. We argue that these values have been gradually lost over the past half-century, particularly the understanding of private gardens as strategic spaces in which social challenges can be met. Due to lack of documentation, current knowledge of their meaning and heritage is poor. Their physical space is declining through urban densification. We add to the densification debate by arguing the potential for reinvigoration of the private garden and its values, to meet and plan for sustainable urban futures. Based on historical reflections and a presentation of the significance and meaning of private gardens in Belgium and Sweden, the main contributions of this article are general insights on the heritage and meaning of private gardens and a future outlook on the strategic role of private gardens in planning.     

The response of plant growth and leaf gas exchange to the speed of lamp movement in a greenhouse

High-pressure sodium (HPS) light supplementation during the low-light months has become quite common for high-light requiring crops at latitudes above 45°. Most common systems have fixed installations, while movable systems have been tried with various results in greenhouses. The concept is that fewer lamps are used on a track system, and that light intensity varies over time. In two trials, we determined whether the speed of the HPS lamp movement had any effect on leaf CO₂ exchange rate, growth and developments of various plants species. Plants (chrysanthemum, petunia, rose and tomato) were grown in a greenhouse supplemented with HPS lamps which moved at various speeds (0, 2, 8 and 20 mm s⁻¹) between 06:00 and 24:00 h daily for about 6–7 weeks. One trial started at the end of November and one started at the end of January. The light sum from the lamps were 0.212 ± 0.004 mol m⁻² h⁻¹ at bench level, and the supplemental lighting represented 55 and 35% of the total light received by the plants for the two trial dates, respectively. The growth (dry matter) was reduced for tomato only when grown under moving lights compared to those grown under the stationary system, while plant height was not affected. Light saturated CO₂ exchange rate on the youngest fully developed leaves increased with lamp speed for petunia and tomato, but not for chrysanthemums, while apparent quantum yield was not affected by lamp speed for any species. In situ measurements of net CO₂ exchange rate (NCER) with supplemental lighting only, showed that NCER decreased exponentially when lamp speed increased from 0 to 20 mm s⁻¹.