Dynamics of non-structural carbohydrate reserves in pruned Erythrina poeppigiana and Gliricidia sepium trees

Abstract

In alley cropping systems, fast growing leguminous trees are pruned to reduce competition with crops for light and to provide organic inputs for crop nutrition. Tree regrowth depends on non-structural carbohydrate reserves in the remaining tree parts. In this study, the dynamics of starch and soluble carbohydrates in roots and stems of completely pruned (all shoots removed), partially pruned (one branch retained on the pruned stump) and unpruned Erythrina poeppigiana (Walp.) O.F. Cook and Gliricidia sepium (Jacq.) Kunth ex Walp. trees were studied under humid tropical conditions in Turrialba, Costa Rica. Measurements on starch and soluble carbohydrates in roots and stems were made at 0, 2, 6 and 12 weeks after pruning during both a ''rainy'' and a ''dry'' season. In general, the dynamics of non-structural carbohydrates in roots and stems of pruned E. poeppigiana and G. sepium trees were similar. Starch concentration was highest in unpruned trees and higher in roots than in stems of pruned trees. The effect of pruning intensity was first observed in stems, and starch reserves were more depleted in stems than in roots, an effect more evident during the ''dry'' season. The critical tree regrowth stage for starch mobilisation was that of vigorous sprout development at six or four weeks after pruning particularly in completely pruned trees. At this time, fine root biomass and length and nodule biomass in pruned trees decreased. Survival of fine roots and nodules was greater in partially pruned than in completely pruned trees. Starch accumulation in roots recommenced at 12 weeks after pruning in G. sepium, and later than 12 weeks after pruning in E. poeppigiana roots. This study showed that E. poeppigiana responded better to pruning regimes than G. sepium. Recovery of trees after pruning is better when trees are partially pruned than when completely pruned.

Occurrence and abundance models of threatened plant species: Applications to mitigate the impact of hydroelectric power dams

“…However, its roots have a unique strategy to acquire soil nitrogen. The roots do not exploit available nitrogen in the soil, and instead use nitrogen in the leaf litter (Chesney and Vasquez, 2007;Payan et al, 2009 on E. poeppigiana in agroforestry systems), an environmental variable that was analysed in our study. Conversely, M. frondosus, another Fabaceae species, was not reported to produce nitrogen-fixing nodules (Allen and Allen, 1981;Faria et al, 1984).…”

Shoot Pruning and Impact on Functional Equilibrium Between Shoots and Roots in Simultaneous Agroforestry Systems

“…The operating premise of shoot pruning management is that managing perennial tree species by frequent pruning is possible because affected plants tend to restore the functional balance between above-and below-ground plant organs through reducing root respiration, slowing or ceasing root growth or reallocating carbon from storage organs in roots and stems to shoot meristems to support tree regrowth (Chesney & Vasquez, 2007;Eissenstat & Yanai, 1997). The consequence of acropetal movement of carbon from roots and stems to shoot meristems to provide energy for new shoot growth and restoration of photosynthetic capacity is the death of roots and nodules and contribution of carbon and nitrogen to soil pools (Chesney & Vasquez, 2007;Nygren & Campos, 1995;Nygren & Ramirez, 1993).…”

“…The consequence of acropetal movement of carbon from roots and stems to shoot meristems to provide energy for new shoot growth and restoration of photosynthetic capacity is the death of roots and nodules and contribution of carbon and nitrogen to soil pools (Chesney & Vasquez, 2007;Nygren & Campos, 1995;Nygren & Ramirez, 1993). This response mechanism by pruned trees is essential to recovery and sustainability of the treecrop system.…”

“…On the other hand, lopping or partial pollarding (e.g. leaving one branch on the pruned stump) may lead to the growth of the retained branch at faster rate than other branches from shoots on the pruned stump (Chesney, 2008;Chesney & Vasquez, 2007). This may be due to branch autonomy for carbon uptake independent of the needs of other developing shoots on the pruned stump and this may be species and season dependent (Sprugel, 2002;Sprugel et al, 1991).…”

“…Trees pruned during the dry season resprout more vigorously compared to the response during the rainy season. Chesney & Vasquez (2007) reported that pruned E. poeppigiana and G. sepium trees mobilised similar amounts of starch in roots and stems in the rainy season but more starch in stems in the dry season because sink demand was greater in the dry season when greater and faster resprouting occurred compared to the wet season. In that experiment, resprouting occurred two weeks earlier during the dry season compared to the wet season.…”