Transpiration and growth of young African mahogany plants subject to different water regimes

Timber production has been prominent in the Brazil scenario to minimize deforestation. Thus, technical information is necessary to define the productive process of the African mahogany in the Midwest region of Brazil, especially with regard to its hydric parameters. Recent studies, reported in the literature, have shown that irrigation improves the performance of young African mahogany plants in the field. Sap flow measurement can be used to estimate transpiration of perennial plants and to determine their water demand. This study evaluated the influence of two water regimes on the transpiration and growth of an African mahogany forest after irrigation has ceased. Moreover, this study also characterizes the seasonal patterns of transpiration and growth of African mahogany under these conditions. African mahogany plants with 2.5 years of age were cultivated in Bonfinopolis-GO and evaluated for 2 years. Treatments were IT-irrigated until 2 years of age-and NIT-non-irrigated. Plant height (PH), breast height diameter (DBH), trunk volume (TRV), leaf area (LA), leaf dry matter (LDM), and transpiration (T) were monitored by heat dissipation probe (HDP) between Oct/2014 and Oct/2015. Higher growth in LA, DBH, and LDM were observed in IT. However, increase in PH and TRV was similar in both treatments. The mean annual T was similar between treatments (15.0 L m^-2 month^-1). The highest T was recorded in October/2014 (IT = 33.0 L m^-2 month^-1) and July/2015 (NIT = 20.5 L m^-2 month^-1). The greater LA and water deficit blades DEF > 30 mm promoted lower transpiration in the irrigated plants. Irrigation maintained plant growth in PH, DBH, and LA in the third year, even after irrigation has ceased. However, non-irrigated plants were similar in TRV (0.065 m³) and transpiration rates (≈ 15 L m^-2 month^-1). Winter transpiration (11.3 L m^-2 month^-1) was lower than in summer (18.8 L m^-2 month^-1) for irrigated plants and similar for non-irrigated plants (≈ 14 L m^-2 month^-1). Based on that, in order to maintain the homogeneity of the plants, the irrigation in the first 2 years of cultivation is recommended, and also, the sap flow measures presented satisfactory results regarding the determinations of the water needs of African mahogany.