Caracterização e seleção de acessos de Paspalum quanto à resiliência ao cultivo em telhados verdes extensivos

Abstract

The use of vegetation cover on green roofs contributes to the formation of micro-ecosystems in the urban environment, increasing the green area. However, the selection of plants suitable for use on green roofs represents the most critical factor for their performance. Research with grasses of the Paspalum genus for green roofs and other purposes of use, has contributed to the enhancement of the genetic potential of native plants. This study aimed to characterize and select accessions of Paspalum spp. for use on extensive green roofs, based on characteristics of ecological and aesthetic features, in addition to using phenotyping techniques in the characterization of native grasses for use on green roofs. Simulating a green roof condition, the experiment was carried out from May 2018 to June 2019, at the Federal Rural University of Pernambuco - UFRPE, Recife. The 16 genetic materials provided by EMBRAPA Pecuária Sudeste and used in this work were: P. notatum (PNO1, PNO2, PNO3, PNO5, PNO6 and PNO7); Paspalum sp. (CE2, CE5 and CE9); P. compressifolium (PCO1, PCO2 and PCO3); P. rhodopedum (PRH1 and PRH2); P. ionanthum (PIO1); P. rojasii (PRO1). Considering the rusticity and resilience conditions evaluated, the plants were grown in 7 cm deep trays and filled with low fertility soil. The evaluated characteristics were: growth height (Alt-cm); setting rate (TAP -%) at 30 days after planting - DAP; persistence rate (TPER -%) at 180 DAP; covering capacity (CC -%) and fresh and dry shoot biomass (BFPA and BSPA - g / plant), roots and rhizomes (BFR, BSR and BFRZ, BSRZ - g / plant). The accessions of prostrate growth PNO1, PNO5 and CE5, and that of upright growth (tuft) PIO1 showed better suitability of use for extensive green roofs, with good establishment, good coverage capacity, reduced vertical growth, low maintenance and good tolerance. the depth of 7cm. This shows the resistance and rusticity of the same to the adverse conditions of the environment in the absence of nutritional support, as well as the good speed of recovery of these accessions in the period that the nutritional support was offered emphasizing the resilience of this genus. Regarding the techniques, the Soil-Adjusted Vegetation Index - SAVI, thermometry - TM and thermography - TG. The relationship between SAVI and the coverage area showed a coefficient of determination (R2 = 0.84), with green matter (R2 = 0.73), with dry matter (R2 = 0.56). Thermography and thermometry provided measurement of leaf temperature and canopy showing no significant difference between the accessions for leaf temperature (TMF and TGF) and for canopy thermometry (TMD), whereas for canopy thermography - TGD there was a significant difference, with accesses of upright growth showed lower canopy temperatures than those of low growth. The relationship between the techniques showed high values of determination coefficient (R2 = 0.85) between TMF and TGF and (R2 = 0.91) between TMD and TGD. Given the above, the SAVI index can be used to estimate the coverage capacity (CC), identify how much of this coverage is green matter (MV%) and how much is dry matter (MS%). Leaf and canopy temperatures can be used as an indication of water deficit in Paspalum accesses, using both the infrared thermometer (more accessible) and the thermographic camera. Canopy thermography - TGD can also be used to evaluate the thermal performance of green roofs. Thermographic images indicated that Paspalum accessions of erect growth (tuff) may possibly provide better thermal comfort.