Effect of lopping on water potential, transpiration, regrowth, 14C-photosynthate distribution and biomass production in Alnus glutinosa

Abstract

The effects of light, moderate and heavy branch pruning or lopping treatments (resulting in removal of 28-31, 56-60 and 80-82% of the foliage, respectively, unlopped control = 0%) were studied in 3-year-old black alder (Alnus glutinosa L. Gaertn.) plants. Within 24 h of lopping, transpiration rates decreased and water potentials increased. The effects of lopping continued for 48 days. The improved water status of the lopped plants enhanced water-use efficiency during the first 30 days. Regrowth was related to a combination of enhanced net assimilation rates during the first 30 days after lopping, use of current photoassimilates and stored carbohydrates in the roots (particularly in medium and heavily lopped plants) for the production of new leaf area, and delayed leaf senescence. The lightly and moderately lopped plants developed 62 and 57% more leaf area, respectively, than the unlopped plants, but total leaf area development was slower in the heavily lopped plants. Lightly lopped plants produced total biomass equivalent to that of unlopped plants, but the moderately and heavily lopped plants produced less biomass than the unlopped plants. During the first 30 days after lopping, there was a net loss of nodule dry matter and recovery to control values did not occur during the period of study. Immediately (24 h) after lopping, more (14)C-photosynthate was translocated to the roots of lopped plants than to the roots of unlopped plants. When a branch near the base of the main stem was fed (14)CO(2), (14)C-photosynthate translocation to the shoot increased with increasing intensity of lopping, at 50 days after lopping.

Effect of pruning on Prosopis juliflora: considerations for tropical dryland agroforestry

“…In our study, pruning increased the photosynthetic rate and hence, biomass growth, linearly with increasing pruning intensity. Responses of plants to defoliation either by pruning or lopping vary greatly (see Belsky, 1986;Singh & Thompson, 1995;Kadiata et al, 1997;Patch et al, 1998;Verdaguer et al, 2000). Increase in total biomass has been observed in most cases, e.g.…”

“…Shoot pruning has become a management practice in agroforestry for reducing both above-and belowground competition with associated crops (Fownes & Anderson, 1991;Sinclair et al, 1998), supplying organic materials to the soil (Mafongoya et al, 1998) and providing mulch during the cropping season (Kadiata et al, 1998). However, as the functional balance of the tree is altered through pruning, it reacts both morphologically and physiologically in response to the changes and consequently, the growth and development of shoots and foliage may be altered (Singh & Thompson, 1995).…”

Changes in Whole-Tree Water Use Following Live-Crown Pruning in Young Plantation-Grown Eucalyptus pilularis and Eucalyptus cloeziana

“…The duration of whole-plant water use reductions following reductions in photosynthetic leaf area depends on the rate of leaf area production in the crown [17]. In fast-growing species with rapid turn-over of leaf area [18], including eucalypts, reductions in water use following defoliation may be relatively short-lived under favourable environmental and climatic conditions. However, such reductions may be useful during short-term periods of low rainfall to reduce the mortality rates and the susceptibility of trees and stands to water stress.…”

Initial effects of quinclorac on the survival and growth of high biomass tree species

“…One-year old Populus maximowiczii x nigra trees that were decapitated and allowed to reshoot had over 50 percent greater photosynthetic rate and a 37 percent increase in leaf dry weight compared to unpruned trees (Tschaplinski & Blake 1995). Pruning of young black alder (Alnus glutinosa) led to lower transpiration rates for 48 days post pruning and net assimilation rate increase for the first 30 days as pruning intensity increased (Singh & Thompson 1995). Similarly, removal of upper leaves and leaf laminae in silver birch (Betula pendula) saplings led to increased photosynthetic rates (Ovaska et al 1992).…”

“…Still, these increases in remaining leaves or new, post-herbicide leaves correspond to depletion of metabolites including sucrose and galactose in the stems (Tschaplinski & Blake 1994) and a reduction of carbohydrates and starches in both the lower stem and roots (Tschaplinski & Blake 1995). Potentially, minor defoliation and stem dieback events may not lead to losses in overall biomass due to the rapid regrowth and improved water status due to less transpiration in the reduced leaf area (Seastedt et al 1983;Singh & Thompson 1995). However under field conditions where water stress increases during drier summer months following exposure to quinclorac, trees are at a great risk of reserve depletion that leads to decreases in biomass and increases in mortality.…”