Effect of Acacia plantations on net photosynthesis, tree species composition, soil enzyme activities, and microclimate on Mt. Makiling

Abstract

To determine the effectiveness of rehabilitation on improving ecosystem functions, we examined net photosynthetic rate (P N ), tree species composition, soil enzyme activities, and the microclimate (air and soil temperature, relative humidity) of an area on Mt. Makiling that has been rehabilitated and protected from fire for over 12 years. After it was last burned extensively in 1991, restoration was initiated by planting Acacia mangium and Acacia auriculiformis. We selected three areas to study in 2003. Two areas were rehabilitated with A. mangium and A. auriculiformis, and one was still dominated by Imperata cylindrica and Saccharum spontaneum. P N of A. mangium and A. auriculiformis showed significantly lower values than those of I. cylindrica and S. spontaneum. The Acacia plantations had more naturally regenerated tree species than the grassland. Additionally, more tree species appeared in the A. mangium plantation than in the A. auriculiformis plantation. Ficus spetica was present in all of the study sites. Dehydrogenase and phosphatase activities were significantly higher in soil under the Acacia plantations than under grassland. Grassland showed higher air temperature, relative humidity, and soil temperature as well as a larger variation per hour in these parameters compared to the Acacia plantations. The highest air temperature, relative humidity, and soil temperature were measured in April during the dry season. From the regression analysis, soil temperature was significantly correlated with air temperature. Hence plantations, as a rehabilitation activity for grassland, promote natural regeneration and stabilize the microclimate. This stabilization of the microclimate affects establishment and growth of naturally occurring tree species.

Ecophysiological traits associated with the competitive ability of invasive Australian acacias

“…, 2003). N 2 ‐fixing associations occur in most Australian acacias (Lawrie, 1981; Lee et al. , 2006), which usually nodulate with common, but slow‐growing Bradyrhizobium species (Lafay & Burdon, 2001; Rodríguez‐Echeverría et al.…”

“…Australian acacias are well known for their N 2 -fixation abilities (Levine et al, 2003). N 2 -fixing associations occur in most Australian acacias (Lawrie, 1981;Lee et al, 2006), which usually nodulate with common, but slow-growing Bradyrhizobium species (Lafay & Burdon, 2001;Rodríguez-Echeverría et al, 2011). Associations with other nodulating species have also been reported, including Rhizobium, Ensifer, Mesorhizobium, Burkholderia, Phyllobacterium and Devosia species (Marsudi et al, 1999;Lafay & Burdon, 2001;Hoque et al, 2011).…”

Nitrogen and phosphorus retranslocation and N:P ratios of litterfall in three tropical plantations: luxurious N and efficient P use by Acacia mangium

“…Therefore, large production of A. mangium is likely supported by high photosynthetic rate from leaves containing high N and efficient P use under enough light, water and limited P conditions. The efficient P retranslocation by A. mangium appears to be a discrepancy with an enhanced P acquisition ability by the significant phosphatase activities (Kojima 2004;Lee et al 2006), because efficient P retranslocation did not occur under sufficient P conditions (Martínez-Sánchez 2005; Richardson et al 2008). These two P use strategies might be caused by differences in P demand by the host plant and its symbiotic microbes.…”

“…Leguminous Acacia mangium growing in solution cultures or pots were found to efficiently utilise P under P-deficient conditions (Vadez et al 1995;Ribet and Drevon 1996;Nguyen et al 2006). Recent studies showed that tropical legumes had enhanced P acquisition abilities compared to other species (Khanna 1998;Kojima 2004;Lee et al 2006;Houlton et al 2008). A literature survey indicated that extracellular phosphatase activities were significantly higher in soils under N 2 -fixing plants compared to those under non-N 2 -fixing plants (Houlton et al 2008).…”

Ecological Impact on Nitrogen and Phosphorus Cycling of a Widespread Fast-growing Leguminous Tropical Forest Plantation Tree Species, Acacia mangium

“…Some tropical N 2 -fixing trees exhibit specific P acquisition abilities by producing larger extracellular phosphatase [15]. This phosphatase production was larger in soils under A. mangium than those under secondary forests [16]. Houlton et al [17] suggested that N 2 -fixing plants could thrive under P-deficit conditions, such as those encountered in the wet tropics, in part by enhanced phosphatase production using the abundant N resources.…”