Drought Mortality of Tree Seedlings in an Eroded Tropical Pasture

Abstract

Experimental restoration may both accelerate and elucidate natural processes of succession on degraded agricultural land by offering insight into factors that influence rates of succession and the composition of resulting communities. A novel study in restoration of degraded tropical agricultural land in coexistence with cattle ranching activities was established in southern Veracruz, Mexico. The experimental planting of 16 mixed-species stands of 18 pioneer and late-successional tree species was established from September to November 2006 on an eroded hillside pasture with an elevational gradient from 182 to 260 m and heterogeneous soil depths. An unusually severe dry season in 2007 killed 72 per cent of the seedlings: least squares regression suggested that survival of six pioneer and 12 late-successional species was mainly explained by initial basal diameter at planting followed by soil depth for pioneers and by elevational position on the hillside for latesuccessional species. Individuals with larger initial size at planting (>4 mm basal diameter), regardless of germination size in a growing house, survived better probably because larger seedlings developed deeper roots that found fissures in substrate underlying thin soils. Interestingly, seedlings small at planting (<4 mm basal diameter) survived as well as large seedlings in deeper (>19 cm) soils, but virtually, all small seedlings died on thin soils (<18·5 cm). Mortality in restoration plantings can be reduced by planting large seedlings of a mix of pioneer and late-successional species, recognizing that soil depth is a key criterion for survival of the smallest seedlings in a cohort.

Seedling growth and survival of five tree species in secondary forests and adjacent pastures in the montane rain forests of southern Costa Rica

“…Davidson, Gagnon, Mauffette and Hernández (1998) reported for I. densiflora survival levels higher than 90 % in degraded pastures, higher than the levels observed here. The reason for this difference could be that the initial average height reported by Davidson, Gagnon, Mauffette and Hernández (1998) was more than twice the initial average height in our study; this clearly favored growth and survival (Gerhardt, 1994;Martínez-Garza, Tobon, Campo, & Howe, 2013). The initial diameter and seedling size has shown to influence survival and growth of tree seedlings planted in pastures (Mexal, Rangel, Negreros-Castillo, & Lezama, 2002).…”

Influence of Rhizobia Inoculation on Biomass Gain and Tissue Nitrogen Content of Leucaena leucocephala Seedlings under Drought

“…In a restoration effort of degraded agricultural land in Mexico, the establishment rate and drought survival were greater for legume seedlings that grew for two months under controlled conditions before planting [60]. Applying our results to field conditions, Leucaena seedlings grown with R. tropici until lignification occurs are likely to gain more biomass and increase N tissue content compared with those grown with M. loti.…”

Performance of 15 tropical tree species recruited or transplanted on restoration settings

“…In our study, transplants might have suffered some water limitation. This is supported by higher diameter growth rates of transplant compared to recruits; basal diameter has been related to root biomass for juvenile trees growing in experimental plantings (Martínez-Garza et al 2013a). Evaluation at species level revealed a contrasting response of Heliocarpus: recruits of this species showed higher height growth rates than transplants suggesting that this species have not overcome transplant shock.…”