Arboriculture & Urban Forestry 34(3): May 2008 Table 2. Effect of soil management techniques on and plant height (cm), trunk diameter (cm), and shoot length of Tilia × europaea.z Parameter Height increment (cm) Total height increment (cm) Diameter increment (mm) Total diameter increment (mm) Shoot length (cm) Data are reported as means and subjected to analysis of variance. Different letters within the same row indicate statistical differences at P 0.05 (*) or P 0.01 (**) using Duncan test. NS nonsignificant. z affected by compost mulching in the first year compared with pine bark and control trees. This parameter was also higher considering the total increment after 3 years from planting. Shoot length was generally higher in trees mulched with compost. In linden trees, the effects of mulching were more evident in the second year after planting when trees mulched with compost generally showed higher values of the parameters measured than control trees (Table 2). Total diameter increment was higher in trees mulched with compost, whereas plant height was not sta- tistically affected. In 2005, coarse compost was more effective to increase mean annual net photosynthesis of Tilia × europaea than pine bark and control. On Aesculus × carnea, no statistical differences were found among the different management techniques (Table 3). However, because mulched trees were larger with longer shoots, whole-plant leaf gas exchange was probably greater. Mulching with both compost and pine bark increased transpi- ration of horsechestnut in 2005 compared with chemical weed- ing, whereas no effect was found in 2006. No differences were found on Tilia × europaea in both years for this parameter (Table 4). Net photosynthesis also showed a declining trend over time in both species in 2005, whereas this trend was not observed in 2006. An explanation for this behavior is the higher rainfall techniques.z Parameter A(mol/m−2/s−1) E (mmol/m−2/s−1) WUE (A/E) Gs (mmol/m−2/s−1) Ci (ppm) Chlorophyll fluorescence (Fv/Fm) Data are reported as means and subjected to analysis of variance. Different letters within the same row indicate statistical differences at P 0.05 (*) or P 0.01 (**) using Duncan test. NS nonsignificant. z ©2008 International Society of Arboriculture during August in 2006 than in 2005. Differences were only noted in linden at the beginning and at the end of the growing season, when control trees showed lower Pn values compared with those mulched with compost (Figure 1). No differences were found in horsechestnut (Figure 2). Comparing the findings of the 2 sepa- rated years, the Pn for horsechestnut trees was higher in 2006, probably as a result of the different environmental conditions. In this regard, it needs to be stressed that individual leaf photosyn- thesis has demonstrated high variability compared with whole plant gas exchange, and it is sometimes complicated by a poor relationship of dry matter production to yield (Klingemann et al. 2005), but it is the only way to measure leaf gas exchange in adult trees. Water use efficiency, in this research considered as the ratio of carbon gain during CO2 assimilation (A, mol/m−2/s–1) to water loss during transpiration (E, mmol/m−2/s–1), is of major impor- tance to the survival, productivity, and fitness of individual plants and it was higher in control trees only in 2005 in Tilia and in 2006 in Aesculus. Actually, the two species showed different patterns in the 2 years. Tilia × europaea had higher Pn and E values in 2005 compared with Aesculus × carnea, which in 2006 showed higher values of photosynthesis but not a corresponding increase in transpiration, which was actually lower. As a conse- quence, this species showed higher values of WUE. Table 3. Net photosynthesis (A), transpiration (E), water use efficiency (WUE), stomatal conductance (Gs), substomatal CO2 concentration (Ci), and chlorophyll fluorescence values in Aesculus × carnea young trees under different cultivation Year 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 Pine bark 6.75 8.43 2.66 a 1.76 2.65 ab 5.60 149.01 a 98.84 178.06 181.95 0.75 0.75 Compost 6.91 8.85 2.81 a 1.96 2.56 b 5.04 148.11 a 107.05 171.75 190.00 0.74 0.74 Control 6.95 8.53 2.46 b 1.78 2.93 a 5.11 124.85 101.02 160.58 192.26 0.73 0.74 P NS NS ** NS * NS ** NS NS NS NS NS Year 2004–2005 2005–2006 2004–2006 2004–2005 2005–2006 2006–2007 2004–2007 2005 2006 2007 Pine bark 12.5 67.61 ab 80.11 9.5 ab 16.3 b 17.04 42.84 b 20.02 b 75.45 b 82.94 a Compost 20 77.83 a 97.83 8.73 b 19.17 a 18.17 46.07 a 25.97 a 83.57 a 79.8 a Control 11.11 51.08 b 62.19 10.41 a 14.09 b 16.39 40.89 b 18.14 b 58.83 c 63.67 b P NS ** NS * ** NS * ** ** ** 159
May 2008
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