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To date, the evaluation of the performance of Mediterranean native plants under urban green roof conditions has been limited to monoculture studies. However, plants grow naturally in plant communities and therefore it is of interest to evaluate their growth under realistic conditions, including interactions among plant species. The present study aims to evaluate the growth, flowering, and self-reproduction capacity of three artificially created plant communities consisting of native Mediterranean plants, as exemplified in Greece under shallow green roof substrate depths (8 and 15 cm) and two irrigation regimes (high, 20% ETo and low, 10% ETo). The plant communities (PC) were designed to resemble xerophytic vegetation found either in Chania, Crete (PC-1), as a combined pattern with plants from Attica, Crete, and the Cyclades (Kythnos) (PC-2), or to resemble the coastal vegetation of Attica and Cyclades (Kythnos) (PC-3). Each of the three artificial plant communities (PC-1, PC-2 and PC-3) consisted of nine species and subspecies. The deeper substrate significantly improved the growth, flowering and survival of most plant taxa. The irrigation regime was not significant for all species except one, indicating that minimal amounts of irrigation are required. Four species did not manage to bloom while 15 species were able to self-reproduce.

The present study evaluated the role of having plants at home during the confinement period as a result of the COVID-19 pandemic that deprived people of freely visiting open green spaces. Preferences concerning the quantity of the desired vegetation as well as the ways in which the COVID-19 crisis affected the change of perceptions with regard to having plants at home were also evaluated. A questionnaire, which was filled by 4205 participants, provided an undistracted evaluation of the impact of indoor and outdoor plants on their emotional welfare considering behavioural, social, and demographic variables. The emotional state of the respondents was neutral and a significant proportion expressed positive emotions. Having indoor plants was correlated with more positive emotions, and confined inhabitants allocated more time for plant maintenance. By contrast, negative emotions prevailed in respondents who related to a positive COVID-19 case, which was more frequent in females and young participants living in small houses that received low levels of natural light and had few or no plants. A few indoor plants placed in strategic positions were also preferred compared with a high number of plants. By contrast, an increased amount of vegetation accompanied by living walls was preferred for outdoor settings. Living walls were considered as advantageous for increasing indoor vegetation, but they were also associated with technical and economical hurdles.

The mediating role of water relations on vase life response to prior desiccation (dry handling) was addressed in cut chrysanthemum. In the first part of the study, the contribution of different organs to whole-cut flower transpiration was determined in 12 cultivars. During desiccation, leaf transpiration decreased owing to stomatal closure. Instead, no active regulation was apparent in either stem or flower. Cultivar differences in leaf transpiration were related to the weight loss required to induce stomatal closure (R2 = 0.919). A small portion of cut flower transpiration was through the flower (12.3 ± 0.3 %), with the major contributor being either leaves or stem, depending on the water status and the cultivar. Leaf transpiration was positively correlated with whole-cut flower transpiration (R2 = 0.879). In the second part of the study, the postharvest longevity upon arrival and following desiccation (5 or 10 % weight loss) was determined on six cultivars with contrasting whole-cut flower transpiration rates. In these cultivars, the rehydration ability following a dehydration event, petal carbohydrate and soluble protein contents, as well as leaf carbohydrate, soluble protein and mineral contents were also assessed. Impaired water transport, as a result of prior desiccation, was not associated with the vase life response to dry handling. A strong correlation between whole-cut flower transpiration in the desiccation experiment and the vase life response to prior desiccation was found. Low vase life decrease in response to prior desiccation was associated with decreased whole-cut flower transpiration during the postharvest period. In conclusion, cultivar differences in vase life response to prior desiccation were attributed to variation in leaf stomatal characteristics.

It is widely accepted that green roofs provide multiple benefits to the urban environment and the well-being of the cities' residents. Despite their acknowledged contribution to the contemporary cityscape and environment, their broad implication in arid and semi-arid regions is extremely limited compared to northern countries. Thus, it is of great interest and importance to identify the hurdles that delay the broad implication of green roofs in challenging climatic zones. These hurdles can be categorized either as governmental or technical or psychological even though they all intermingle and interact. More specifically, in the arid and semi-arid climatic zones, such as those of the Mediterranean basin, the governmental incentives are absent forcing the private sector and the homeowners to take the initiative. In those cases, investing in green roofing can only be justified if green roofs are usable and aesthetically pleasing since the preference of the public has been documented towards the intensive green roof types. However, taking into account that the majority of existing buildings are old and can bare minimal additional loading, it is obvious that green roof substrate depth must be minimal. All the above parameters are contradicting and have led us to the introduction of a new green roof category, namely the adaptive type. Adaptive green roofs have minimal substrate depth ranging from 5 to 15 cm but utilize a broad palette of plant species such as groundcovers, turfgrasses, medicinal and aromatic plants coppices and small shrubs. All the above are feasible due to minimal and prudent irrigation inputs. The current presentation provides a thorough review of the plant species evaluated in adaptive green roof systems concerning their response to different substrate types and depths, their tolerance to either deficit irrigation or drought and their irrigation requirements.

Turfgrass use on extensive green roofs could offer a sustainable solution for increasing urban greening within the existing built space in contemporary cities. The aim of the study was to determine Paspalum vaginatum 'Platinum TER' drought tolerance when grown under extensive green roof conditions and two irrigation regimes. Treatments included: (i) six extensive green roof substrates formulated from mixing locally available materials; (ii) two substrate depths (7.5 or 15 cm) and (iii) two irrigation regimes (60% ETc or 100% ETc). Turfgrass drought tolerance was measured, using digital image analysis, as the number of days until a treatment reached 50% green turf cover (GTC). In both study years (2011 and 2012), for each one of the six substrate types, higher GTC values were reached when deeper profiles (15 cm) were combined with the higher irrigation regime (100% ETc), while the worst drought tolerance turfgrass response was obtained when the swallow substrate (7.5 cm) was combined with the deficit irrigation regime of 60% ETc. It was found that increasing substrate depth resulted in delay of drought stress symptoms expression, while irrigation regime affected the velocity of GTC reduction over time with lower irrigation regime resulting in faster GTC decline compared to higher irrigation regime. It was also concluded that the imposed drought stress to the turfgrass by the reduced irrigation could be compensated by increasing substrate depth. Thus, in buildings with adequate load bearing capacity, it is preferable to select a substrate depth of 15 cm since it will result in 40% reduction on irrigation inputs compared to substrate depth of 7.5 cm.

In an effort to increase the accessibility and functionality of shallow green roof systems, the ability of warm-season grasses to provide acceptable growth needs to be further investigated. In the current study, which was conducted during 2011 and 2012, three warm-season grasses (hybrid bermudagrass, Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy ‘MiniVerde’; seashore paspalum, Paspalum vaginatum Swartz ‘Platinum TE’ and zoysiagrass, Zoysia japonica Steud. ‘Zenith’) were established in outdoor lysimeters. The lysimeters were equipped with all necessary green roof layers placed below a coarse-textured substrate that comprised pumice, thermally treated attapulgite clay, peat, compost and zeolite. Half of the lysimeters had a substrate depth of 15 cm, while the other half had a substrate depth of 7.5 cm. Irrigation was applied at crop evapotranspiration (ET c ). Measurements included determination of substrate moisture content, green turf cover (GTC) and leaf stomatal resistance. Significant differences were observed in the values of GTC among the three turfgrass species and the two substrate depths. Zoysiagrass exhibited the best adaptation at the lower depths of shallow green roof systems. At 15 cm substrate depth, zoysiagrass managed to sustain green coverage for the two study periods. In addition, it was the only turfgrass species that managed to perform well at the substrate depth of 7.5 cm. Seashore paspalum exhibited limited green cover at both substrate depths, while hybrid bermudagrass could provide acceptable green coverage only at 15 cm substrate depth.

The current study aims to systematically analyze the relationship between runoff reduction from different types of shallow green roof systems, and the initial substrate moisture conditions, and total rainfall depth. The experimental study comprised of 30 specialized lysimeters equipped with green roof layering. The lysimeters had two different substrate depths (8 cm or 16 cm) and three different plant covers [either succulent plants ( Sedum sediforme (Lacq.) Pau), or xerophytic plants ( Origanum onites L.), or turfgrasses ( Festuca arundinacea Shreb.)]. In addition unplanted lysimeters and lysimeters without a green roof system were utilized as controls. The results of the experimental study were used in order to formulate a mathematical expression, which effectively described the relationship between all the above mentioned parameters (runoff reduction, initial substrate moisture conditions and rainfall depth). The derived relationship was then utilized to provide effective estimations of the rational method runoff coefficients, which constitutes one of the main prescribed methodologies for water resources planning, and management, as a function of initial moisture content and total rainfall depth. Furthermore, the Soil Conservation Service Curve Number model was calibrated using the collected rainfall–runoff data in order to estimate the corresponding curve number (CN) values. Finally, the applicability of a simple linear relationship between total rainfall depth and total runoff depth was investigated. The observed runoff reduction ranged between 2% and 100% for the total runoff depth and between 17% and 100% when the peak runoff rate was considered. Higher reductions were observed in deeper substrates (16 cm) combined with O. onites vegetation cover as well as in cases with lower initial substrate moisture contents and smaller rainfall depths. A strong multiple correlation between rainfall depth, runoff reduction and initial substrate moisture was observed. The developed equation describing this correlation was successfully fitted to the experimental data. In addition, the SCS-CN model was successfully calibrated using the experimental rainfall–runoff data of this study. The obtained CN values were generally high and varied from 88 to 95.5. The lowest CN value was obtained for O. onites vegetation cover combined with deeper substrate depth (16 cm), indicating an increased runoff mitigation potential for such vegetation cover types.

Green roofs constitute a promising technology for reintroducing lost flora in degraded urban environments. The present study aimed to evaluate the growth and ground coverage capacity of seeded Sedums grown on shallow extensive green roofs under semi-arid Mediterranean climatic conditions. Treatments included: a) two types of seed mixtures (M1 containing seeds from 16 different Sedum species and M2 containing seeds from 28 different Sedum species; b) two substrate depths (6 cm and 12 cm) and c) two different irrigation regimes (high and low) during the dry summer seasons of the three-year study period: i) 15% and 0% of the cumulative reference evapotranspiration (ETo) in year 2012, ii) 60% and 30% of ETo in year 2013 and iii) 30% and 0% of ETo in year 2014. Growth performance was evaluated based on the total number of the Sedum plants and their ground coverage rate over the three-year study period. Out of the 16 and 28 Sedum species contained in mixtures M1 and M2, respectively, only four species (S. acre, S. album, S. reflexum, S. sexangulare) were able to survive for the duration of the study period. The seeded Sedum plants did not provide adequate growth or ground coverage. Their plant number decreased abruptly soon after the imposition of the first water stress in 2012 and remained at low numbers throughout the study period. The ground coverage rate was extremely slow. At the end of the three-year study period, Sedum plants of the M1 seed mixture growing in both deep and shallow substrate depths and under high irrigation regimes provided ground coverage of 51.9% and 48.7%, respectively, while the same treatments of the M2 seed mixture provided ground coverage of 25.5% and 19.2%, respectively. All the remaining treatments provided minimal final coverage ranging from 3.1% to 0.5%. Although the seed mixture type exhibited minimal impact on total plant number and ground coverage, S. album and S. sexangulare were not able to grow in the M2 mixture. Overall, the seeded Sedum species exhibited reduced capacity to sustain growth under the Mediterranean climatic conditions, especially during the summer periods and under the imposition of water stress.

Efficient use of irrigation water and nutrient uptake is of utmost importance for efficient and sustainable turfgrass management. In the present study, the ability of selected symbiotic micro-organisms to improve the visual quality and growth of turfgrass was investigated. Specifically, three soil inoculants, Trichoderma harzianum T-22, Glomus intraradices (arbuscular mycorrhizal fungus) and Bacillus amyloliquefaciens FZB42 as plant growth promoting rhizobacterium, were applied in order to colonize Festuca arundinacea 'Grande II'. The study was conducted under greenhouse conditions using disinfected 1.7 L pots filled with a sterilized substrate mixture comprising 85% sand, 2% peat and 13% organic soil. Green turf cover (GTC) and dark green color index (DGCI) were determined using digital image analysis. In addition, the weight of the clippings and the root dry weight were determined. Turfgrass cover and color, as determined by digital image analysis, was affected by inoculation treatments. T. harzianum T-22 and B. amyloliquefaciens FZB42 had a positive influence on turfgrass growth, by increasing clipping yield compared with the control. The aforementioned micro-organisms had a positive effect on root development, while the microscopic examination of root samples showed that the turfgrass root system was colonized by T. harzianum T-22 and G. intraradices. In addition, an efficient colonization of the rhizosphere by B. amyloliquefaciens FZB42 and T. harzianum T-22 occurred. Inoculation with strains FZB42 and T-22 improved GTC and DGCI while G. intraradices did not have any positive impact. These positive first results will be used as a basis for a field experiment where the effects of the above three symbiotic micro-organisms on turfgrass drought resistance will be evaluated.

The aim of this study was to determine the effects of different irrigation regimens on five native aromatic and medicinal species including Ballota acetabulosa (Greek horehound), Helichrysum orientale (helichrysum), Melissa officinalis (lemon balm), Rosmarinus officinalis (rosemary), and Salvia fruticosa (Greek sage) when grown on adaptive green roof systems. The applied levels of irrigation were 100% (well-watered control), 75%, 50%, 25%, and 0% (no irrigation) of the daily pan evaporation (Epan). Measurements included the in situ determination of substrate moisture, stomatal resistance, and soil plant analysis development (SPAD) values. It was found that Greek horehound, helichrysum, and rosemary can sustainably grow at an irrigation of 25% Epan, whereas Greek sage and lemon balm require an irrigation of at least 50% Epan for sustainable growth in shallow adaptive green roof systems.

Fires played an integral role in shaping the rural Mediterranean landscape. However, the decoupling of social-ecological systems of landscapes led to rural degradation and rendered traditional settlements vulnerable to fire. A questionnaire survey conducted at the traditional village of Leontari, in the Peloponnese, Greece, investigates respondents' perceptions towards particular interventions that would affect the landscape character and development of the village after the 2007 forest fires. Results suggest that the values of a location can play a major role in determining the perceptions of respondents. Overall respondents were "place attached" with an increased awareness of the local landscape character that guided their preferences for rural development, however, some sociodemographic group differences were found. Women compared to men were more sensitive to the impact of the forest fire and people over 65 years of age were more positive in restoring the original vegetation compared to younger in age people.

Several locally available materials were tested to create an optimized growth substrate for arid and semiarid Mediterranean extensive green roofs. The study involved a four-step screening procedure. At the first step, 10 different materials were tested including pumice (Pum), crushed tiles grade 1–2 mm (T1–2), 2–4 mm (T2–4), 5–8 mm (T5–8), 5–16 mm (T5–16), and 4–22 mm (T4–22); crushed bricks of either 2–4 mm (B2–4) or 2–8 mm (B2–8); a thermally treated clay (TC); and zeolite (Zeo). All materials were tested for their particle size distribution, pH, and electrical conductivity (EC). The results were compared for compliance with existing guidelines for extensive green roof construction. From the first step, the most promising materials were shown to include Pum, Zeo, T5–8, T5–16, and TC, which were then used at the second stage to develop mixtures between them. Tests at the second stage included particle size distribution and moisture potential curves. Pumice mixed with TC provided the best compliance with existing guidelines in relation to particle size distribution, and it significantly increased moisture content compared with the mixes of Pum with T5–8 and T5–16. As a result, from the second screening step, the best performing substrate was Pum mixed with TC and Zeo. The third stage involved the selection of the most appropriate organic amendment of the growing substrate. Three composts having different composition and sphagnum peat were analyzed for their chemical and physical characteristics. The composts were a) garden waste compost (GWC), b) olive (Olea europaea L.) mill waste compost (OMWC), and c) grape (Vitis vinifera L.) marc compost (GMC). It was found that the peat-amended substrate retained increased moisture content compared with the compost-amended substrates. The fourth and final stage involved the evaluation of the environmental impact of the final mix with the four different organic amendments based on their first flush nitrate nitrogen (NO3−-N) leaching potential. It was found that GWC and OMWC exhibited increased NO3−-N leaching that initially reached 160 and 92 mg·L−1 of NO3−-N for OMWC and GWC, respectively. By contrast, peat and GMC exhibited minimal NO3−-N leaching that was slightly above the maximum contaminant level of 10 mg·L−1 of NO3−-N (17.3 and 14.6 mg·L−1 of NO3−N for peat and GMC, respectively). The latter was very brief and lasted only for the first 100 and 50 mL of effluent volume for peat and GMC, respectively.

The study evaluated the response of Paspalum vaginatum ‘Platinum TE’ turfgrass under adaptive green roof conditions over the course of two years. P. vaginatum was established in six different green roof substrates: (i) S15:Pum60:P20:Z5, (ii) S15:Pum60:C20:Z5, (iii) S15:Pum40:Per20:P20:Z5, (iv) S15:Pum40:Per20:C20:Z5, (v) S30:Pum40:P20:Z10 and (vi) S30:Pum40:C20:Z10 (where S: sandy loam soil; Pum: pumice; Per: perlite; Z: clinoptilolite zeolite; P: peat and C: compost in volumetric proportions that are indicated by their subscript). Two depths of 7.5 cm and 15 cm were used for each substrate type. During two summer periods, water-stress was applied through deficit irrigation of 60% ETc. The control irrigation consisted of 100% ETc. Measurements included the determination of green turf cover (GTC) utilizing digital image analysis. The data was fitted to a sigmoid variable slope model to determine the GTC50 (number of days to achieve 50% green turf cover) and the slope variable (which defines how rapidly GTC changed over time). Finally, parameter estimates were used to calculate 95% confidence intervals for the number of days required for GTC to reach 1%, 25%, 50%, 75% or 95% during the water deficit and spring green-up periods. It was found that during the drought stress periods turfgrass retained its GTC over longer time intervals when grown in the deeper substrates of 15 cm and when combined with the high irrigation regime of 100% ETc. By contrast, the worst drought tolerance turfgrass response was obtained when the swallow substrate (7.5 cm) was combined with the deficit irrigation regime of 60% ETc. The remaining treatments had in-between GTC values, while substrate type was indifferent during the water stress period and, thus, GTC values exhibited the following sequence for the substrate depth and irrigation regime treatments under investigation: 15 cm − 100% ETc > 15 cm − 60% ETc = 7.5 cm − 100% ETc > 7.5 cm − 60% ETc. The GTC50 values were 20.0–26.8 d for the 15 cm − 100% ETc treatment, 14.9–19.9 d for the 15 cm − 60% ETc treatment, 15.5–19.1 d for the 7.5 cm − 100% ETc treatment and 11.7–15.0 d for the 7.5 cm − 60% ETc treatment. During autumn recovery, which occurred just after the termination of water stress periods, the most influential parameter was shown to be substrate type. In that case, the substrates amended with compost provided faster GTC recovery that ranged from 21.6% to 40.9% compared to the peat-amended substrates that reached GTC values from 14.3% to 24.2%. Similarly, a faster spring green-up was determined for substrates amended with compost having a GTC50 of 32.1–64.2 d (with a GTC95 of 50.1–113.7 d) compared to the 43.1–81.3 d of the peat-amended substrates (with a GTC95 of 90.1–117.6 d). It was concluded that P. vaginatum should be established in 15 cm substrate depth if the latter can be tolerated by the building framework. On the other hand, if the load bearing capacity of the building framework is inadequate, then P. vaginatum could be established in 7.5 cm substrate depth, but irrigation should be applied at 100% ETc. However, in those cases when a 15 cm substrate depth can be utilized, then irrigation demands could be reduced at 60% ETc resulting in significant water savings. Substrate type is influential only when water is not a limiting factor, and thus compost-amended substrates are preferred.

Green roofs have a versatile maintenance and irrigation system installation depending on their type (intensive, semi-intensive, or extensive) and plant species selection. The present chapter provides a description of the most commonly utilized irrigation systems and analyzes the common maintenance procedures of green roofs. Irrigation is categorized into surface and subsurface systems that include sprinklers, drippers, subsurface dripping systems, and creation of a perched water table. Innovative ideas such as wick irrigation and irrigation of pitched green roofs are also discussed. Irrigation demands are categorized based on substrate type and depth and plant species selection. Green roof maintenance requirements are presented including drainage and irrigation system, plant protection, integrity of the green roof layers, and safety precautions for the workers.

Sedums are considered among the best plant species for use on extensive green roof types. The present study evaluated the growth capacity of native Sedum sediforme (Jacq.) Pau in extensive green roof systems that varied in substrate type and depth as well as in the applied irrigation regime. The two substrate types included either soil-less (Pum50:Per20:C20:Z10) or soil-amended substrate (S15:Pum40:Per20:C20:Z5) that comprised sandy loam soil [S], pumice [Pum], perlite [Per], compost [C], and zeolite [Z] at volumetric proportions indicated by their subscripts. Each substrate type was used at two depths (7.5 or 15 cm). During the summer drought periods two different irrigation regimes (high and low) were utilised: (a) in 2010, the high irrigation regime replenished 30% of the cumulated daily pan evaporation (Epan) between consecutive irrigation applications, while the low irrigation regime replenished half of it (15% Epan) and (b) in 2011, the high irrigation regime remained the same as in 2010, while the low irrigation regime was not irrigated at all. Measurements included physical and chemical characterisation of the utilised substrates as well as plant growth and physiological measurements that included plant height, dry weight, chlorophyll and carotenoid determination. It was found that during the first study year plant growth was promoted by the soil-less substrate, which was also depicted in the prolific flowering in the following study year, while chlorophyll and carotenoid content increased in the deeper substrates. By contrast, in the second study year plant growth and physiology was mainly enhanced in deeper substrates, while substrate type was indifferent. Despite the observed differences S. sediforme was able to survive under minimal or no irrigation even at the shallow depth of 7.5 cm and proved to be a native plant species that could successfully be utilised in extensive green roof systems in the Mediterranean and other semi-arid climatic regions.

The marine halophytes Arthrocnemum macrostachyum and Halimione portulacoides are found growing naturally in saltmarshes within Greece creating an aesthetically pleasing groundcover that also reflects the changing of seasons. The potential use of these species in an extensive green roof system in coastal areas would lead to additional benefits such as preserving and enhancing the local landscape character and supporting biodiversity. The growth of Arthrocnemum macrostachyum and Halimione portulacoides in an extensive green roof system under two watering regimes (30% ET 0 and 15% ET 0 ) was investigated. The substrates used consisted of soil (S), pumice (Pum) and grape marc compost (C) or peat (P), at various volumetric proportions indicated by the subscripts: S 15 :Pum 70 :C 15 , S 15 :Pum 70 :P 15 and S 15 :Pum 70 :P 7.5 :C 7.5 . Biometric measurements to determine plant growth included plant height and diameter, growth index, dry weights and ground cover. The growth of both plant species was similar under both watering regimes until elevated summer temperatures lead to plant loss in the reduced watering regime (15% ET 0 ). Both shoot and root dry weights of both plant species at the end of the experiment were greater under the 30% ET 0 watering regime. Results indicated that both watering regimes (30% ET 0 and 15% ET 0 ) studied could be applied initially in the early summer months followed by watering with 30% ET 0 at increased summer temperatures.

Little is known about the accuracy of soil moisture dielectric sensors in coarse-textured root zones and green roof substrates. In the present study, the accuracy of two dielectric sensors of different technologies (frequency domain and time domain dielectric sensor) in measuring moisture content was investigated in six coarse-textured green roof substrates. Calibration equations were developed for both sensors, and the effect of electrical conductivity (EC) on substrate moisture content calculation was determined. It was found that for frequency domain sensor the relationship between dielectric permittivity square root () and actual substrate moisture content (θm) was strongly linear for all tested substrates. However, for each substrate a distinct specific calibration equation of was required. The correlation between substrate permittivity and EC was linear for frequency domain sensor for all moisture levels (0% to 35%). In the case of time domain sensor, each green roof substrate was also described from a different calibration curve between actual substrate moisture content and period of time that was recorded by the device. It was found that their relationship was quadratic for all substrates. In addition, time domain sensor output responded in a quadratic manner to increasing levels of EC. This response was found to interact with actual substrate moisture content as well. It was concluded that the most reliable results for moisture content determination of the coarse-textured green roof substrates were obtained by substrate-specific calibration curves for both dielectric sensors.

The development of the green roof market in Greece and other Mediterranean countries in general has not been standardized, unlike in Germany and other northern European countries. The construction of successful sustainable green roofs relies mainly on the development and combination of integrated systems that include green roof stabilization and the appropriate selection of a substrate and drainage system to support sustainable plant growth. The current study provides a thorough review of the decision-making process associated with the selection of substrate, drainage, and slope-reinforcing materials for the Athens Concert Hall green roof park (2 ha). For the scope of this study, guidelines from different scientific fields were modified and combined to accommodate the specifics of this project and the Hellenic climatic conditions. The challenges addressed included a roof shell with 70 different inclinations, underground retaining walls and steps, and steep slopes that reached 70 % gradients. Selection of the appropriate materials and methodologies was supported by analyses that included granulometry, bulk density, hydraulic conductivity, moisture potential curves, organic matter content, and weight at saturation and field capacity. The drainage layer consisted of a bilayered system of pea gravel and sand combined with geotextiles. Substrate characteristics were defined by the analyses undertaken and adapted to the Hellenic climatic conditions. Geogrids and honeycomb geocells were utilized separately or in conjunction on inclined surfaces. Substrate moisture measurements performed at 150 locations on the green roof revealed increased moisture fluctuations (10–35 % v/v), which were mainly caused by the presence of the underground retaining walls.

Turfgrass use in adaptive extensive green roof systems could provide a sustainable solution for increasing urban greening in semi-arid regions. The aim of the study was as follows: (i) to investigate the effects of four different substrate formulations from locally available materials (S 15 :Pum 60 :P 20 :Z 5 , S 15 :Pum 60 :C 20 :Z 5 , S 30 :Pum 40 :P 20 :Z 10 , and S 30 :Pum 40 :C 20 :Z 10 , where S, sandy loam soil; Pum, pumice; P, peat; C, compost; and Z, zeolite in volumetric proportions as indicated by their subscripts), and two substrate depths (7.5 cm and 15 cm) on the lateral growth of Manilagrass ( Zoysia matrella L. [Merr.] ‘Zeon’); (ii) to evaluate the capacity of locally produced compost to be substituted for peat as an organic substrate amendment in an effort to reduce its horticultural use; (iii) to determine the effect of increasing soil participation in substrate formulations on growth and drought resistance of Manilagrass; (iv) to evaluate the effects of the four substrate types and two substrate depths on Manilagrass drought resistance. The measurements included: (a) determination of substrate characteristics, such as particle size distribution, saturated and dry bulk density, total porosity, water potential curves, in situ substrate moisture, pH and electrical conductivity and (b) determination of turfgrass quality and physiological status that included green turf cover (GTC), normalized difference vegetation index (NDVI), and leaf stomatal resistance (LSR). It was found that during establishment, when adequate irrigation of turfgrass was applied, the deeper profiles (15 cm) combined with compost-amended substrates (S 15 :Pum 60 :C 20 :Z 5 and S 30 :Pum 40 :C 20 :Z 10 ) provided higher GTC values while the shallow profiles (7.5 cm) with peat-amended substrates (S 15 :Pum 60 :P 20 :Z 5 and S 30 :Pum 40 :P 20 :Z 10 ) provided the lowest GTC. The opposite phenomenon was observed during water-deficit periods, since the peat-amended substrate S 15 :Pum 60 :P 20 :Z 5 combined with the deeper profile (15 cm) resulted in the least drought stress imposition to Manilagrass while providing the highest GTC and NDVI and the lowest LSR values. By contrast, the compost-amended substrates S 15 :Pum 60 :C 20 :Z 5 and S 30 :Pum 40 :C 20 :Z 10 increased the drought stress imposition to Manilagrass when combined with shallow profiles (7.5 cm). Substrate depth was the most influential factor, since Manilagrass drought stress was alleviated as substrate depth increased from 7.5 cm to 15 cm.

The present study aims to introduce an adaptive approach to intensive green roofs by evaluating suitable, lightweight substrates and by determining the effect of their depth on the growth and physiological status of Pittosporum tobira L. and Olea europaea L. The two-year study was conducted in outdoor containers (1.2 m × 1.2 m) while treatments included the use of two depths (30 cm and 40 cm) and three different substrates: (a) pumice (Pum) mixed with peat (P) and zeolite (Z) in a volumetric proportion of 65:30:5 (Pum65:P30:Z5), (b) pumice mixed with compost (C) and zeolite in a volumetric proportion of 65:30:5 (Pum65:C30:Z5) and (c) sandy loam soil (S) mixed with perlite (Per) and zeolite in a volumetric proportion of 30:65:5 (S30:Per65:Z5). Each experimental plot was planted with four plants of P. tobira and one plant of O. europaea var. Koroneiki. Measurements included determination of the physical and chemical characteristics of the substrates while plant growth and physiological status were determined through plant growth index, trunk perimeter for olive trees, SPAD measurements and chlorophylla+b content. Both the plant species exhibited better growth and higher chlorophyll content in the compost-amended substrate (Pum65:C30:Z5) due to its higher nutrient content. The 40 cm depth substrate provided minimal improvement in the growth of both the plants at the end of the first year while in the second year the deeper substrate positively influenced the growth of olive trees.

In spite of the well-known green roof benefits, their widespread adoption in the management practices of urban drainage systems requires the use of adequate analytical and modelling tools. In the current study, green roof runoff modeling was accomplished by developing, testing, and jointly using a simple conceptual model and a physically based numerical simulation model utilizing HYDRUS-1D software. The use of such an approach combines the advantages of the conceptual model, namely simplicity, low computational requirements, and ability to be easily integrated in decision support tools with the capacity of the physically based simulation model to be easily transferred in conditions and locations other than those used for calibrating and validating it. The proposed approach was evaluated with an experimental dataset that included various green roof covers (either succulent plants - Sedum sediforme, or xerophytic plants - Origanum onites, or bare substrate without any vegetation) and two substrate depths (either 8 cm or 16 cm). Both the physically based and the conceptual models matched very closely the observed hydrographs. In general, the conceptual model performed better than the physically based simulation model but the overall performance of both models was sufficient in most cases as it is revealed by the Nash-Sutcliffe Efficiency index which was generally greater than 0.70. Finally, it was showcased how a physically based and a simple conceptual model can be jointly used to allow the use of the simple conceptual model for a wider set of conditions than the available experimental data and in order to support green roof design.

Turfgrasses are a promising means of cultivation for covering roof tops of buildings. Their low and frequently prostrate growth, their ability to provide total surface coverage, the increased tolerance of specific species to several stress factors such as drought, heat, solar irradiance, and air pollution make them good candidates for green roof plant material. In intensive green roof systems the selection of the substrate is of major importance since it was found to affect Festuca arundinacea growth while at the same time contributes to the roof weight. The effort to minimize the load applied onto the building necessitates the use of substrate amendments that are lightweight and usually coarse textured. However special care should be given to the environmental fate of the agrochemicals applied on these coarse textured substrates since nitrates were found to leach in excess from a sandy loam soil amended with perlite (30:70% v/v mix). In addition metalaxyl-m leached from the substrates in a manner that was reversely proportional to the amount of organic matter in the substrate. In extensive green roofs trials that included four different substrates with variable depth (7.5 and 15 cm) and two irrigation regimes (high and low) establishment rate of Zoysia matrella ‘Zeon’ was generally improved by substituting peat with compost in the substrates but performed poorly under water stress conditions. The stress was alleviated by increasing substrate depth from 7.5 to 15 cm. Further research is necessary to establish rigid standards for the use of turfgrasses on green roofs.

The role of rootzone CO2 and O2 levels on seed germination and plant growth is not fully defined. The aim of the present study was to investigate the effects of supraoptimal CO2 in combination with different O2 concentrations on seed germination and the growth of pre-rooted stolon segments of Cynodon dactylon. Seeds of “Princess 77” were germinated in specialized airtight tubes for 21 days. Gas mixtures containing 40–20, 40–10, 40–2.5% CO2–O2, or air were injected every 12 h. The establishment of bermudagrass stolons took place in micro-lysimeters for 28 days, while the rootzone was injected with either ambient air (control) in natural conditions or with the above-mentioned gas mixtures. For the determination of the effects of soil gases on stolon growth, the cumulative clippings dry weight, the root dry weight, the root total area and total length were recorded. The leaf chlorophyll, the relative water content, and the soluble sugars of both leaves and roots were also measured. The presence of 4...

Turfgrass use in semi-extensive green roofs might provide an additional solution for establishing green roofs in urban city centres. The aim of the present study was: (a) to investigate the effects...

Green roofs have received increased interest as a result of their environmental, social, and economic benefits. The present study aims to evaluate suitable, lightweight substrates for the installation of semi-intensive-type green roofs and their effects on Lavandula angustifolia growth and physiological status under Mediterranean climatic conditions. The study was conducted in field containers (1.2 × 1.2 m), and treatments included the use of two depths (20 cm or 30 cm) and three different substrates: 1) pumice (Pum) mixed with peat (P) and zeolite (Z) in a volumetric proportion of 65:30:5 (Pum65:P30:Z5); 2) pumice mixed with compost (C) and zeolite in a volumetric proportion of 65:30:5 (Pum65:C30:Z5); and 3) sandy loam soil (S) mixed with perlite (Per) and zeolite in a volumetric proportion of 30:65:5 (S30:Per65:Z5). Each experimental plot was planted with four plants of L. angustifolia. The physical and chemical characteristics of the substrates and the in situ substrate moisture levels were determined. Plant growth was determined by the growth index and root dry weight, whereas the plant physiological status during the stressful summer period was determined by chlorophylla+b content and stomatal resistance. It was found that the bulk density of all of the substrates was less than 0.8 g·cm−3, whereas the water retention of substrate S30:Per65:Z5 was greater than the other two substrates at all tensions. Substrate depth was the most influential factor; therefore, the deeper substrates (30 cm) provided higher growth indices and root dry weight, increased total chlorophyll content, and reduced leaf stomatal resistance compared with the shallower substrate depth of 20 cm. Differences between substrate types were smaller compared with those of substrate depth. In spring, the growth index in substrate Pum65:C30:Z5 was larger but not in the summer when the growth index of substrates S30:Per65:Z5 and Pum65:P30:Z5 exceeded that of the substrate amended with compost until the end of the study. In late summer, the plant total chlorophyll content decreased in all substrates, whereas substrate Pum65:C30:Z5 exhibited increased stomatal resistance compared with the other two substrates at the same period. It was concluded that L. angustifolia could be grown successfully in semi-intensive Mediterranean green roofs at a substrate depth of 20 cm, but its growth and tolerance to the harsh summer conditions would improve at a substrate depth of 30 cm.

Green roofs cooling and thermal insulating features have been demonstrated in many research projects. However, all efforts mostly have assessed green roof thermal properties under steady state conditions or by computational modeling. The present study evaluated green roof thermal performance in terms of the thermal transmittance coefficient, in real scale and under dynamic conditions. For the study's purposes, five semi-intensive green roof systems were constructed on the roof of an outdoor test cell. It was found that the green roof with 8 cm thick rock wool substrate with 2 cm sod on top had a very low U-value. For the same level of substrate moisture content, the other two green roof systems made of 8 cm deep coarse aggregate substrates with 2 cm sod on top provided higher U-values. In contrast, deeper amounts of same substrates (20 cm) reduced the U-value. The relation between the estimated thermal transmittance and the substrate moisture content was investigated and found to be linear. The green roof systems were also simulated for a single-storey residential building in order to quantify their possible energy savings. The results from the simulation showed that shallow substrates conserve building energy mainly during the summer period of the year. Rock wool and deeper substrates showed significant cooling and thermal insulating features.

A field study evaluated composted olive mill waste (OMC) as a soil amendment in Cynodon dactylon (bermudagrass; C4) turf establishment and maintenance. The study comprised two substudies, each of which had discrete goals: 1) an evaluation of OMC effects on overall bermudagrass growth over the course of 2.5 years when established by seed and subsequently from sprouting of existing rhizomes (2002 to 2004); and 2) a re-evaluation of OMC effects on bermudagrass establishment by seed (2003). Twenty-four plots (1.44 × 1.44 m) were filled with sandy-loam soil and supplemented with one of three OMC proportions (low= 12.5%, medium = 25%, and high = 50% by volume, indicated as substrates S:OMCL, S:OMCM, and S:OMCH, respectively), and non-amended soil served as a control (S). The study evaluated: 1) the substrate's chemical and physical characteristics, including bulk density, water retention curves, pH, and electrical conductivity (EC) measurements; 2) the establishment rate of C. dactylon, either by seed or by sprouting of existing rhizomes after dormancy as determined by measurements that included vertical detachment force (VDF), root growth, and substrate moisture; and 3) the growth rate of C. dactylon as determined through measurements of visual quality, clipping dry weight, root growth, and VDF. The results show that OMC decreased substrate pH in proportion to the OMC supplementation rate and increased EC only at the end of the study and only in the plots with the highest supplementation rate (S:OMCH). Water retention was improved by OMC incorporation except from S:OMCL, which increased water retention only at low tensions. Compared with soil alone, bulk density decreased by 13.5%, 19.7%, and 32.8% as the OMC rate increased, respectively, from 12.5% to 50%. The OMC rate of 50% v/v resulted in a minor reduction in plant visual quality during the cold periods but in a slight improvement during the warm periods. The clipping dry weights were increased by OMC amendments in 2003, which was considered a disadvantage because of the insignificant visual quality differences between substrates during the 2 study years. In 2004, the clipping yields were unaffected by OMC rate. Root dry weight response to OMC varied. For the highest OMC rate, root dry weight was lower during the cold and wet periods, greater during the first stages of bermudagrass establishment by seed, and similar compared with soil without OMC during turf establishment from the sprouting of existing rhizomes after dormancy. The highest OMC rate reduced resistance to vertical detachment force at four sampling dates (of six) during the 2002–2003 study, because the reduced root dry weight and/or increased moisture of the substrate facilitated bermudagrass detachment. In contrast, OMC-supplemented substrates resulted in increased VDF at the first sampling date of establishment both by seed (2003) and by rhizome sprouting after dormancy (2004). It was concluded that, when speedy establishment is imperative (such as in sod farms) or when irrigation is limited, an OMC rate of 50% by volume should be selected. In contrast, for sustainable bermudagrass growth, a rate of 12.5% by volume is preferred, because it increases the visual quality of the grass and root growth.

This 2-year research study focuses on the reclamation of bentonite inclined surfaces using hydroseeding in a quarry of the island of Milos. Three types of hydroseeding seed mixes were utilized: a) a mixture from 7 native species of Milos’s island, b) a mixture from 6 commercial species, c) a barley-oat mixture and d) a non-hydroseeded control. The study included two inclined surfaces. The first had a northern while the second had an eastern orientation. Each inclined surface had 12 experimental plots (12-15 m height and 1,5 m width and each experimental plot was subdivided into 3 subplots along the height direction (high, medium, low). Measurements included the total number of plants, the total number of plants per species, the number of invading plants; soil moisture and plant dry weight. It was found that during the 2 years of the study, the number of plants as well as the soil moisture was higher in the northern inclined surface compared with the eastern one. The commercial species mixture provided the highest plant number (66%, 59% and 74% more than native species, barley-oat and the control, respectively). However towards the end of the second year a significant decrease in the number of plants of the commercial species mixture was observed that equalized its plant numbers with the barley-oat mixture. The number of the native mixture was minimal and equal to the non seeded control. In contrast plant number in the barley-oat mixture was reduced by 3% from the first to the second year. The commercial plants mixture provided the most biomass as indicated by the dry weight. The species that provided the highest plant numbers were mainly Lolium rigidum and Avena sterilis. The plant-intruders that were detected without participating in the hydroseeding mixture were Brassica nigra, Salsola kali, Inula viscosa and Mesembryanthemum nodiflorum.

Preferential flow is implicated as one of the causes of groundwater contamination with agrochemicals. Although preferential flow is a natural process, on turfgrass surfaces, it may be enhanced by mechanical aeration that creates surface perforations similar to macropores. Aeration effect on pesticid

Two field studies (winter and summer) were performed to evaluate the effect of three different fertilizer programs and a urea formaldehyde resin foam (UFRF) soil amendment on sod establishment and anchorage. Fertilizer treatments involved were 1) a quick release (QR) granular fertilizer (12-12-17); 2) a slow release (SR) fertilizer (27-5-7); and 3) a foliar (FL) fertilizer (20-20-20). The application rate was 50, 30, 0.35 g·m-2 for QR, SR, and FL, respectively. The substrate consisted of sandy loam soil, and in half of the plots UFRF flakes were incorporated in the upper 100 mm at a rate of 20% v/v. The effects of the fertilizer and soil amendment on sod establishment were evaluated through measurements of the dry weight of clippings and roots and the visual quality of the turf. Sod anchorage was measured by determination of the vertical force required to detach a piece of sod. For each treatment the initial and final pH, EC, available P, exchangeable K, Ca, Mg, and Fe were also determined. It was found that FL reduced clipping yield but retained turf visual quality similar to the other fertilizer treatments except in winter, when it resulted in the worst quality ratings. However, FL fertilizer promoted root growth and provided high vertical detachment force values and therefore enhanced sod establishment. Slow release fertilizer resulted in moderate top growth and visual quality of the turf during winter, but delayed sod establishment. Quick release fertilizer increased top growth and improved turfgrass visual quality during the winter, but root growth and vertical detachment force were reduced, indicating poorer sod establishment. UFRF did not enhance sod establishment since there was a negative effect on root growth when temperatures were below 10 °C, without however affecting vertical detachment force. Differences in soil P, K, Ca, Mg and Fe between treatments were inconsistent between the two studies, except for final K concentration, which was higher for QR fertilization than SR and FL. Foliar fertilization can enhance sod establishment compared to QR and SR, by accelerating sod anchorage and root growth. QR can be used in late autumn to improve winter green up of the sod. UFRF does not improve or accelerate sod establishment and possesses a minimal capacity to improve soil properties of sandy loam soils.

Fresh, senesced, and decaying pine needles from Pinus halepensis were evalu- ated for their allelopathic potential on Festuca arundinacea, Cynodon dactylon and the biosensor plants Avena sativa and Lemna minor through in vivo and in vitro studies. The in vivo study was performed in growth chambers, using 6, 12, and 18 g of pine needle tissue mixed with screened perlite as a substrate. The effects of the different pine needle types were evaluated by determining the total root length, total root surface, root dry weight, total shoot length, total shoot surface, and shoot dry weight. The in vitro study was performed in Petri dishes where seeds from each species were subjected to an increasing concentration of pine needle extract. The extracts were obtained from pine needle ground tissue that was diluted with water and either shacked at room temperature or placed in water bath at 40 °C for 24 h. The evaluation of the allelopathic potential was performed with the determination of radicle length. The allelopathic potential of the pine needle tissues was confirmed with bioassays using oat (A. sativa) and duckweed (L. minor). The results strongly suggested the allelopathic potential of the pine needle tissue, being more pronounced in the fresh, moderate in the senesced, and low in the decaying pine needles. The allelopathic substances were species-specific, and the inhibition resistance of the species tested followed the order F. arundinacea > C. dactylon > A. sativa. The inhibition of the L. minor suggested that the water soluble phytotoxic compounds were inhibitors of Photosystem II. Plants produce many compounds that have no apparent metabolic, physiological, or struc- tural role for the producer. These secondary metabolites might exhibit allelopathic effects and influence other organisms in the vicinity of the producer (Rice, 1984). In many cases, allelochemicals function as biochemical defence mechanisms or possess insecticidal, repellent, antifeedant, and antimicrobial ac- tivities (Grainge and Ahmed, 1988; Peterson et al., 1989). In turfgrasses, allelopathy has been inves- tigated as an interactive mechanism to explain competition between species (Lickfeldt et al., 2001). Brede (1991) was unable to determine allelopathic inhibitory action when leachate collected from a Poa annua putting green was applied onto bentgrass (Agrostis stolonifera ssp. palustris Huds.). In contrast, Buta et al. (1987) found different degrees of lettuce seed- ling growth inhibition when seed leachate from various turfgrasses was applied. Tall fescue (Festuca arundinacea Schreb.) has been found to exhibit allelopathic effects on birdsfoot tre