Apical control of branch movements in white pine: biological aspects

Two-year-old branches on control trees (Pinus strobus L.) were compared through a season with branches on trees stem-girdled just above, or below, the branch whorl. All branches first sagged down for 20 days and then moved up for 40 days. Then, control branches reversed and moved back down while branches in both girdle treatments continued to move up. Movement reversal correlated with cessation of both elongation and diameter growth in control branches. Diameter growth continued in branches of girdled trees. Control branches continued to stiffen even after diameter growth stopped. Differences in movements due to girdling are from compression wood formed after cessation of branch elongation. Apical control stops cambial activity and compression wood formation in branches after branch elongation ceases, allowing photosynthate produced in the branch to move to the stem. Control branches bend down from increasing self-weight after cambial activity ceases.     

THE ROLE OF RESERVES IN LEAVES,BRANCHES, STEMS,AND ROOTS ON SHOOT GROWTH OF RED PINE

By defoliation, girdling, and various combinations of these before the growing season began, the role of foods in old needles, branches, main stems, and roots on shoot growth of 8-yr-old red pine (Pinus resinosa) trees was studied in northern Wisconsin. Defoliation and girdling, alone or in combination, reduced shoot growth but defoliation reduced shoot dry weight more than it reduced shoot elongation. Reductions in shoot growth due to treatment were in the following decreasing order: branch girdling + needle removal > girdling at stem base + needle removal > needle removal > branch girdling > base girdling. The old needles were the major source of food for shoot growth and accounted for four-fifths or more of all shoot growth. The combined reserves in the branches, main stem, and roots accounted for less than 15% of shoot growth. The contribution of reserves from tissues other than old leaves was in the following order: branches > main stem > roots. Defoliation weakened apical dominance relations. In defoliated trees, many secondary axes elongated more than the terminal leader, and secondary axes in lower whorls often grew more than those in upper ones. The data suggest an important role of nutritional factors in correlative growth inhibition.     

Effects of defoliation and girdling on fruit production in Ilex aquifolium

1. The effects of defoliation and girdling on fruit production in European holly Ilex aquifolium were studied in a northern Spanish population. Three defoliation treatments (control, 50% and 100% leaf removal) were applied at branch level in 10 trees. Six branches were used per treatment in each tree and half of these branches were girdled (a ring of bark and cambium was removed from the branch base).
2. Leaf removal from ungirdled branches had little effect on fruit set, fruit production and reproductive allocation at branch level. However, these variables decreased as the extent of defoliation increased on girdled branches.
3. Fruit production in undefoliated branches did not differ between girdled and ungirdled branches, showing that girdled branches were autonomous for fruit production when undamaged. Mean fruit mass of girdled-100% defoliated branches averaged 8% of fruit mass produced by control branches.
4. Fruit production of ungirdled-100% defoliated branches did not differ from control branches, showing the importance of resource importation from other branches. Hence the branches may be regarded as only partially autonomous for fruit production.
5. Fruit production of girdled-50% defoliated branches was 42% of fruit production of control branches, while ungirdled-50% defoliated branches amounted to 70% of controls. These results also demonstrated resource importation but did not support the existence of photosynthetic compensatory mechanisms.
6. The ability of resource importation developed by fruiting branches might be a mechanism to reduce the effect of reproductive costs in this species.     

The role of herbivory by wood-boring insects in mangrove ecosystems in Belize

The roles wood-boring insects play in modifying mangrove ecosystems were examined on small, offshore mangrove islands in Belize. Several species of xylem- and phloem-feeding woodborers consume the wood of living mangrove trees. By girdling, pruning, and hollowing, woodborers killed over 50% of the Rhizophora mangle canopy in experimental plots arrayed across a tidal-elevation gradient. In contrast, leaf-feeding herbivores removed less than 6% of the canopy. In the plots, stem girdlers killed over three branches per tree. The patterns of herbivory by three functional feeding groups were heterogeneous and did not vary consistently with tidal elevation. Because R. mangle lacks viable axillary buds or the ability to produce epicormic shoots to replace pruned branches, the canopy architecture was significantly modified by this damage. The branches that were pruned by stem girdlers created numerous small holes or gaps in the mangrove canopy. Shoot growth and flowering increased in R. mangle trees with 50% of their branches experimentally girdled. Because branches and twigs attacked by woodborers lost their leaves prematurely as greenfall, the quantity and quality of leaf litter were altered when a leaf-bearing branch was girdled or hollowed. These changes suggest that wood-boring insects also significantly affect internal and external nutrient cycling processes in mangrove ecosystems.     

Changes in Photosynthesis and Fruit Characteristics in Olive in Response to Assimilate Availability

The source level in the olive cultivar Leccino was varied by girdling at different stages of fruit growth. Afterwards, the effects on gas exchange, fruit growth, and ripening and blooming were studied. Girdling during fruit growth did not significantly influence net photosynthetic rate (P _N) except in the last phase of fruit growth when the P _N was reduced. In the girdled branch, P _N began to decrease at the onset of starch accumulation because fruit growth ceased. In mid-November stomatal conductance (g _s) and transpiration rate (E) were also reduced by girdling, whereas sub-stomatal CO₂ concentration (C _i) increased in leaves from the girdled branches. The total chlorophyll content (Chl) tended to decrease in parallel with the reduced P _N. Girdling did not substantially influence the leaf and shoot water contents. The large availability of assimilates seems to cause an earlier fruit ripening. In general, girdling increased fruit dry mass. Healing before the time when the majority of pulp growth occurs reduced the effect of girdling. June girdling increased the pit dry mass. Girdling at the beginning of August and September, compared to the control, increased the pulp dry mass, but the pit dry mass did not differ with respect to the control. The percentage of oil in the fruit, on a dry mass basis, increased with August and September girdlings, but the percentage of oil in the pulp did not change. Girdling reduced shoot growth, but the internode length was unchanged. Girdling slightly stimulated differentiation of flower buds.     

Stem girdling influences concentrations of endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton

Many studies have shown that root–shoot imbalance influences vegetative growth and development of cotton (Gossypium hirsutum L.), but few have examined changes in leaf senescence and endogenous hormones due to stem girdling. The objective of this study was to determine the correlation between some endogenous phytohormones, particularly cytokinins and abscisic acid (ABA), and leaf senescence following stem girdling. Field-grown cotton plants were girdled on the main stem 5 days after squaring (DAS), while the non-girdled plants served as control. Plant biomass, seed cotton yield, main-stem leaf photosynthetic (Pn) rate, chlorophyll (Chl) and malondialdehyde (MDA) concentrations, as well as levels of cytokinins and ABA in main-stem leaves and xylem sap were determined after girdling or at harvest. Main-stem girdling decreased the dry root weight and root/shoot ratio from 5 to 70 days after girdling (DAG) and reduced seed cotton yield at harvest. Main-stem leaf Pn and Chl concentration in girdled plants were significantly lower than in control plants. Much higher levels of MDA were observed in main-stem leaves from 5 to 70 DAG, suggesting that stem girdling accelerated leaf senescence. Girdled plants contained less trans-zeatin and its riboside (t-Z + t-ZR), dihydrozeatin and its riboside (DHZ + DHZR), and isopentenyladenine and its riboside (iP + iPA), but more ABA than control plants in both main-stem leaves and xylem sap. These results suggested that main-stem girdling accelerated leaf senescence due to reduced levels of cytokinin and/or increased ABA. Cytokinin and ABA are involved in leaf senescence following main-stem girdling.     

Fruit Set, Abscission and Dry Matter Accumulation on Girdled Branches of Macadamia

The patterns of fruit growth, abscission and dry matter accumulationwere determined for ungirdled macadamia branches and comparedwith the patterns on girdled branches. The relationships betweenfruit set, fruit drop, and the number of available leaves werealso assessed. Approximately 50 leaves were required to supportdevelopment of each fruit on girdled branches, so that finalfruit numbers on girdled branches were higher or lower thanon ungirdled controls, depending on leaf number. High leaf numbersdid not cause any increase in fruit size on girdled branches,but low leaf numbers resulted in fruit volumes up to 23% lowerthan the controls. The number of fruits set on ungirdled brancheswas independent of the number of leaves on the branch. Defoliationof ungirdled branches had no effect on the number of fruitsset, with fruit set on these branches apparently being supportedalmost entirely from carbohydrates obtained elsewhere in thetree. Three phases of fruit drop were observed, with maximaat 2, 6-7, and 10 weeks post-anthesis, separated by phases ofrelatively low fruit drop at 4 and 8 weeks post-anthesis. Themaximum dry weight increase of the crop occurred between 10and 20 weeks post-anthesis, when there was very little fruitdrop. Therefore, although limited availability of assimilatesmay influence fruit retention in macadamia, there is no simplerelationship between structural carbon demand and fruit drop.Copyright1994, 1999 Academic Press Macadamia integrifolia Maiden and Betche, Macadamia tetraphylla L. A. S. Johnson, Proteaceae, macadamia, fruit set, fruit drop, girdling     

Effects of jasmonic acid, branching and girdling on carbon and nitrogen transport in poplar

? Here, we examined the impact of jasmonate (JA) treatment, branching and phloem girdling on 13C and 1?N import, invertase activity and polyphenol accumulation in juvenile tissues of unbranched and branched hybrid poplar saplings (Populus nigra?×?P. deltoides). ? The import of 13C to juvenile tissues was positively correlated with invertase activity at the treatment site and enhanced by JA. Both invertase activity and 13C import were greater in shorter, younger branches and smaller, younger leaves. By contrast, JA treatments, branching and girdling had little or no impact on 1?N import. ? In poplar saplings with multiple lateral branches, we observed almost no 13C movement from subtending source leaves into lateral branches above them, with or without JA treatment. The presence of potentially competing branches, treated with JA or not, girdled or not, had no impact on carbohydrate (CHO) import or polyphenol accumulation in target branches. ? We conclude that poplar branches comprise modules that are relatively independent from each other and from the stem below in terms of CHO movement, carbon-based defence production and response to elicitors. By contrast, branches are closely linked modules in terms of nitrogen movement. This should produce trees that are highly heterogeneous in quality for herbivores.     

Effects of habitat fragmentation on the three-way interaction among ants,aphids and larvae of the giant purple emperor, <Emphasis Type="Italic">Sasakia charonda</Emphasis> (Hewitson), a near-threatened butterfly

Survival rates of both early and middle instar larvae of the nymphalid butterfly, Sasakia charonda, were estimated to be lowest on test trees planted in a meadow (site A), intermediate in a small, narrow secondary deciduous broadleaf forest (small patch, site B) and highest in a large secondary deciduous broadleaf forest (large forest, site C). The larval mortality rates due to predation by tree-climbing predators from the ground (tree climbing predator) such as ants and the larvae of carabids were estimated to be greater at sites A and B than those at site C. The number of predatory ants climbing test trees was significantly greater at sites A and B than at site C, and the ants harvested honeydew from aphids living on tree leaves at those two sites. Aphid densities were significantly higher on trees at sites A and B than at site C, and aphid densities and numbers of predatory ants were significantly and positively correlated at sites A and B. In an experiment controlling aphid density per branch on test trees, the numbers of ants and the mortality rates of S. charonda larvae were greater on branches with high aphid densities than on those with low aphid densities at both sites A and B. These results suggest that the aphid density per host tree was higher in the meadow and the small patch than in the large forest; at both sites these higher aphid densities attracted higher numbers of predatory ants to test trees, and as a result, mortality rates of S. charonda larvae were increased.     

Tree-girdling to separate root and heterotrophic respiration in two Eucalyptus stands in Brazil

The release of carbon as CO₂ from belowground processes accounts for about 70% of total ecosystem respiration. Insights about factors controlling soil CO₂ efflux are constrained by the challenge of apportioning sources of CO₂ between autotrophic tree roots (and mycorrhizal fungi) and heterotrophic microorganisms. In some temperate conifer forests, the reduction in soil CO₂ efflux after girdling (phloem removal) has been used to separate these sources. Girdling stops the flow of carbohydrates to the belowground portion of the ecosystem, which should slow respiration by roots and mycorrhizae while heterotrophic respiration should remain constant or be enhanced by the decomposition of newly dead roots. Therefore, the reduction in CO₂ efflux after girdling should be a conservative estimate of the belowground flux of C from trees. We tested this approach in two tropical Eucalyptus plantations. Tree canopies remained intact for more than 3 months after girdling, showing no reduction in light interception. The reduction in soil CO₂ efflux averaged 16–24% for the 3-month period after girdling. The reduction in CO₂ efflux was similar for plots with one half of the trees girdled and those with all of the trees girdled. Girdling did not reduce live fine root biomass for at least 5 months after treatment, indicating that large reserves of carbohydrates in the root systems of Eucalyptus trees maintained the roots and root respiration. Our results suggest that the girdling approach is unlikely to provide useful insights into the contribution of tree roots and heterotrophs to soil CO₂ efflux in this type of forest ecosystem.     

Tissue Differentiation of the Regeneration Rind in Jerusalem artichoke Stem

In trees, after removal of the bark, the vascular tissues of the newly-formed bark usually developed as a continuous layer. However, the stem of the herbaceous Jerusalem artichoke, after girdled, gives rise to regeneration of many irregularly arranged vascular bundles. Early July is the best time for girdling as the vascular bundles are well-developed, One week after girdling, some small groups of vascular tissues appeared in callus. Later on the vascular bundles eventually grew close together sooner or later, yet there were some wide pith rays which separated the various sized vascular bundles and exhibited irregularly contours. From these experiments, it is further evidenced that tile stem of herbaceous plants can also be girdled and regenerates a new rind. Furthermore, the girdled portion of this plant regenerates the vascular tissues which in a rather different way from all the plants that previously studied.     

The autotrophic contribution to soil respiration in a northern temperate deciduous forest and its response to stand disturbance

The goal of this study was to evaluate the contribution of oak trees (Quercus spp.) and their associated mycorrhizal fungi to total community soil respiration in a deciduous forest (Black Rock Forest) and to explore the partitioning of autotrophic and heterotrophic respiration. Trees on twelve 75 × 75-m plots were girdled according to four treatments: girdling all the oaks on the plot (OG), girdling half of the oak trees on a plot (O50), girdling all non-oaks on a plot (NO), and a control (C). In addition, one circular plot (diameter 50 m) was created where all trees were girdled (ALL). Soil respiration was measured before and after tree girdling. A conservative estimate of the total autotrophic contribution is approximately 50%, as indicated by results on the ALL and OG plots. Rapid declines in carbon dioxide (CO₂) flux from both the ALL and OG plots, 37 and 33%, respectively, were observed within 2 weeks following the treatment, demonstrating a fast turnover of recently fixed carbon. Responses from the NO and O50 treatments were statistically similar to the control. A non-proportional decline in respiration rates along the gradient of change in live aboveground biomass complicated partitioning of the overall rate of soil respiration and indicates that belowground carbon flux is not linearly related to aboveground disturbance. Our findings suggest that in this system there is a threshold disturbance level between 35 and 74% of live aboveground biomass loss, beyond which belowground dynamics change dramatically.     

Colonization of disturbed Scots pine trees by bark‐ and wood‐boring beetles

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Interguild interactions between a non-native phloem feeder and a native outbreaking defoliator

1. Competitive and synergistic interactions directly or indirectly drive community dynamics of herbivorous insects. Novel interactions between non-native and native insects are unpredictable and not fully understood. 2. We used manipulative experiments on mature red spruce trees to test interactions between a non-native phloem feeding insect, the brown spruce longhorn beetle (BSLB), and an outbreaking native defoliator, the spruce budworm. We subjected treatment trees to defoliation by three densities of spruce budworm larvae. Treatment trees were: stressed by (i) girdling (to mimic beetle feeding) or (ii) girdling + BSLB before spruce budworm larvae were introduced on branches in sleeve cages. Budworm larvae then fed on foliage and developed to pupation. We assessed all branches for budworm performance, defoliation, shoot production and shoot growth. 3. Shoot length did not differ in response to stress from girdling or BSLB infestation. Neither stress from girdling, nor interactions with BSLB feeding affected spruce budworm performance or defoliation. Intraspecific impacts on performance and defoliation in relation to budworm density were stronger than the effects of tree stress. 4. Prior infestation of red spruce by BSLB in our experimental set-up did not influence spruce budworm performance. BSLB is a successful invader that has blended into its novel ecological niche because of ecological and phylogenetic similarities with a native congener, Tetropium cinnamopterum. 5. Outbreaks by BSLB will not likely impede or facilitate spruce budworm outbreaks if they co-occur. It would be useful to evaluate the reverse scenario of BSLB success after defoliation stress by spruce budworm.     

Birds girdling activity on exotic tree species as a form of adaptive behavior?

Four tree species in the Kostelec n. ?. l. arboretum (Czech Republic) have been repeatedly damaged by Dendrocopos medius. The unique aspect of this otherwise common behavior called girdling consists in regularly visiting the same trees every spring, although there are more than 1.200 tree species within the arboretum. We monitored transpiration, leaf phenology and the chemical composition of the xylem sap of girdled and nongirdled trees. Spectral analysis revealed slightly higher amounts of sugars, especially saccharose, in Cladrastis Raf. as the most regularly girdled tree among other conditions, comparing girdled to non-girdled trees. Higher transpiration rates were not confirmed in connection with girdling—quite the opposite—Cladrastis Raf. as the most highly favored tree for girdling showed the lowest transpiration rates (in average 6 kg water per day within spring months) compared to other non-girdled trees. We presume that the birds do not choose a particular tree on the basis of any visible or chemical traits but they examine many trees within their territory. Afterwards they probably remember the position of trees whose xylem sap starts to flow early in the spring compared to other trees, as their transpiration stream is enriched with sweet organic substances that represent an advantage for the forthcoming nesting period.     

环剥对红松(Pinus koraiensis)韧皮部和木质部碳水化合物的影响

树干环剥可以阻碍韧皮部光合产物的运输并进一步影响光合产物的分配。长时期内,环剥能够导致环痕上部可溶性糖和淀粉的积累,但对于短期内如何影响碳水化合物在木质部和韧皮部内的运输模式所知甚少。以38年生红松(Pinus koraiensis Sieb.etZucc.)为研究材料,分别对环剥上部、下部每隔1~2d采样,区分木质部和韧皮部(树皮)进行可溶性糖和淀粉含量及树干糖呼吸消耗速率测定,确定环剥后的日变化和周变化,并对木质部可溶性糖、淀粉含量与韧皮部中相应指标进行相关关系的回归分析。结果发现:(1)环剥后4周内,在环剥痕上、下部间木质部可溶性糖和淀粉含量,韧皮部中淀粉含量均不存在显著差异(p>0.05),而韧皮部内可溶性糖含量,环剥后第2周出现显著差异,从第4周出现环剥上部显著高于下部的碳水化合物积累现象(p<0.05);(2)环剥阻隔了韧皮部可溶性糖的纵向运输,但是并不影响木质部的纵向运输,而且环剥并没有影响木质部和韧皮部之间的糖和淀粉的相关关系;(3)环剥第1周内环剥上部和下部呼吸消耗速率差异不显著,第2周环剥上部显著高于环剥下部,从第3周开始环剥下部呼吸消耗速率显著下降。推断认为,在环剥处理的4周内,环剥上部冠层新形成的碳水化合物很大一部分均被呼吸消耗掉,导致环剥上部较环剥下部可溶性糖稍有增加;红松胸高直径以下部分所储藏的碳水化合物足以保障2周内红松树干呼吸。     

Girdling increases survival and growth of emerald ash borer larvae on Manchurian ash

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Girdling of young Robinia pseudoacacia trees on the Tama River terrace,central Japan

Robinia pseudoacacia L. has been widely planted worldwide for a variety of purposes, but it is an aggressive invader in many regions. To control invasion by the species, we examined the effectiveness of girdling young trees to ground level to kill trees and preclude sprout development through comparison among girdling, clearcut and control treatments on the Tama river terrace, Tokyo. More than 99% of R. pseudoacacia trees were killed by girdling. The number of sprouts that developed from roots and stumps after girdling was distinctly reduced compared with that observed after clearcutting. We also conducted girdling of young trees of Ailanthus altissima (Mill.) Swingle, which shows similar developmental and ecological characteristics to R. pseudoacacia, and the two species are often sympatric. More than 98% of A. altissima trees were killed, but a higher number of sprouts developed from A. altissima stumps compared with that from R. pseudoacacia stumps. These results indicate that girdling young trees to ground level is an effective method of controlling R. pseudoacacia by killing the stem and precluding sprout development. The girdling method is simple to apply and imposes a low burden on the surrounding environment.

     

Influence of Invasive Tree Kill Rates on Native and Invasive Plant Establishment in a Hawaiian Forest

Fire tree (Morella faya) has invaded extensive areas of wet and mesic forest on the Island of Hawai’i, forming nearly monospecific stands. Our objective was to identify a method of controlling M. faya, which would allow native plants to establish while minimizing establishment by invasive plants. Treatments (logging all trees, trees left standing but girdled, and incremental girdling over 20 months) were selected to kill M. faya stands at different rates, thereby creating different conditions for species establishment. Leaf litter was either removed or left in place; seeds and seedlings of three native pioneer species, three native forest species, and three alien invasive species were then added to determine their ability to establish. Native pioneer species established best in the log and girdle treatments, whereas seedling emergence of native forest species was higher in the girdle and incremental girdle treatments. Seedlings of invasive species emerged faster than the natives, but each of them responded differently to the stand treatments. Leaf litter reduced seedling emergence for all species, with small‐seeded species (<1 mg/seed) affected most under low light conditions. No single method eliminated all invaders, but girdling of M. faya provided suitable conditions for most native species. If combined with selective removal of the most disruptive alien species and native seed additions, girdling could be an effective general strategy for restoring native forests that have been overwhelmed by woody invaders.     

Pathogenicity of Bursaphelenchus xylophilus on Pines in Minnesota and Wisconsin

The pinewood nematode, Bursaphelenchus xylophilus, was inoculated into established native jack and red pines (Pinus banksiana and P. resinosa) and exotic Austrian pine (P. nigra) in Minnesota and Wisconsin forests during summer 1981. The nematode isolates did not kill established nonstressed pine trees growing in the forest. However, the same nematode isolates killed pine seedlings under greenhouse conditions. Girdling the main stem of some trees to induce stress resulted in the death of the majority of inoculated and noninoculated branches of Austrian and jack pines, but no branch death was observed on red pine. Greater numbers of nematodes were extracted from branches of inoculated, girdled trees than from nongirdled trees. The mean number of nematodes extracted from branches of inoculated, nongirdled trees was 0.3 - 14 nematodes per gram of wood.