Experimental evidence of an increased leaf production in Prosopis after removal of epiphytes (Tillandsia)

The production of new leaves of host trees can be affected by the presence of epiphytic species. This experimental study was planned to evaluate the effects on the mean number of new leaves produced by Prosopis alba considering the factors site-disturbance, different epiphytes loads, and the respective zones in the tree crown. The number of new leaves produced was counted manipulating branches with originally low and high loads of epiphytes at different crown zones, in 10 trees per site. The effect of manual removal of epiphytes on the leaf production of the hosts was analyzed by comparing branch responses in short and medium periods of time (i.e., 6 months and 3 years, respectively). There were no significant differences when comparing the number of new leaves produced in the sampled trees at sites with different human disturbance intensities. By contrast, significant differences were observed between both epiphytic loads treatments and when comparing tree crown zones. Experimental results showed a higher subsequent host leaf production (>100%) in branches where epiphytes were experimentally removed, in comparison with branches with high load of epiphytes The number of new leaves produced in branches with naturally low loads of the epiphytes was higher than 1000% compared to branches with high Tillandsia loads. Finally, a higher significant production of new leaves was observed in the bottom crown zone as compared with the middle and upper crown zones. Furthermore, this trend was confirmed considering a longer time-period (3 years) after experimental removal of epiphytes. A significant increase (>100%) was observed when comparing the production of new leaves between different periods after total epiphyte removal. In consequence, Tillandsia species could be considered as “structural parasites” of Prosopis alba.     

Differential leaf traits of a neotropical tree Cariniana legalis (Mart.) Kuntze (Lecythidaceae): comparing saplings and emergent trees

Cariniana legalis is an emergent tree that reaches the upper canopy in Brazilian Semideciduous Forest. Spatial contrasts in microclimatic conditions between the upper canopy and understorey in a forest may affect morpho-physiological leaf traits. In order to test the hypothesis that the upper canopy is more stressful to leaves than a gap environment we compared emergent trees of C. legalis, 28–29 m in height to gap saplings, 6–9 m in height, for the following parameters: leaf area, leaf mass area (LMA the dry weight:leaf area ratio), leaf thickness, leaf anatomical parameters, stomata conductance, and chlorophyll a fluorescence. Leaves from emergent trees had smaller leaf areas but greater LMA compared to saplings. Leaf thickness, palisade layer thickness, and stomatal density were higher for emergent trees than for saplings. The opposite pattern was observed for spongy layer thickness and spongy/palisade ratio. Stomatal conductance was also higher for emergent tree leaves than for sapling leaves, but the magnitude of depression on stomatal conductance near midday was more pronounced in emergent trees. The potential quantum yield of photosystem II, as determined by the F _v/F _m ratio was lower for leaves from saplings. The lower values of stomatal conductance, indicating restriction in CO₂ diffusion into the mesophyll can be related to higher photoinhibition observed in the saplings. Leaves from emergent trees and saplings exhibited similar values for apparent electron transport rates and non-photochemical quenching. Our results suggest that changes in leaf traits could be associated to dry conditions at the upper canopy as well as to the ontogenetic transition between sapling/emergent tree life stages.     

Abundance of white lace lerp psyllids on understorey and canopy river red gums and relationships with foliar sugars and tannins

1. Trees present herbivorous insects with the greatest diversity of resources of any plant growth form. Both ontogeny and shading can alter suitability for arboreal insect herbivores. 2. We conducted a longitudinal study of tagged ‘mature’ (>12 months old) Eucalyptus camaldulensis leaves to compare the suitability of understorey and canopy trees for the leaf senescence-inducing psyllid, Cardiaspina albitextura. We quantified sugars and tannins as possible predictors of nymphal abundance. 3. Canopy leaves hosted double the number of nymphs as understorey leaves. Variation among individual trees (understorey and canopy) was the most important source of heterogeneity explaining psyllid abundance, although relative leaf age significantly influenced oviposition on canopy leaves. The diversity of foliar sugars was higher among canopy leaves than among understorey leaves. There was significant between-tree diversity in total hydrolysable tannins (HTs) and total condensed tannins (CTs) among understorey trees but not among canopy trees. Heterogeneity among understorey and canopy trees was explained by greater diversity of ellagitannins (HTs) than of CTs. 4. Shading is detrimental to the survival of nymphs on both host types, but sugars are unlikely to explain variation in suitability. Vescalagin (an ellagitannin) was negatively correlated with the abundance of nymphs on both host types.     

A tropical epiphytic orchid uses a low‐light interception strategy in a spatially heterogeneous light environment

Light is considered a non‐limiting factor for vascular epiphytes. Nevertheless, an epiphyte's access to light may be limited by phorophyte shading and the spatio‐temporal environmental patchiness characteristic of epiphytic habitats. We assessed the extent to which potential light interception in Rodriguezia granadensis, an epiphytic orchid, is determined by individual factors (plant size traits and leaf traits), or environmental heterogeneity (light patchiness) within the crown of the phorophyte, or both. We studied 104 adult plants growing on Psidium guajava trees in two habitats with contrasting canopy cover: a dry tropical forest edge, and isolated trees in a pasture. We recorded the number of leaves and the leaf area, the leaf position angles, and the potential exposure of the leaf surface to direct irradiance (silhouette area of the leaf blade), and the potential irradiance incident on each plant. We found the epiphytes experience a highly heterogeneous light environment in the crowns of P. guajava. Nonetheless, R. granadensis plants displayed a common light interception strategy typical of low‐light environments, resembling terrestrial, forest understory plants. Potential exposure of the total leaf surface to direct irradiance correlated positively with plant size and within‐plant variation in leaf orientation. In many‐leaved individuals, within‐plant variation in leaf angles produced complementary leaf positions that enhanced potential light interception. This light interception strategy suggests that, in contrast to current wisdom, enhancing light capture is important for vascular epiphytes in canopies with high spatio‐temporal heterogeneity in light environments.     

Does leaf ontogeny lead to changes in defensive strategies against insect herbivores?

Plants use different defense strategies throughout their ontogenetic development. In this study, three questions were proposed: (1) Is there a greater abundance of ants on young leaves, which possess active extrafloral nectaries, than on mature leaves? (2) Do ants exert an indirect defense that is effective against the attack of herbivorous insects? (3) Do mature leaves have a greater concentration of physical and chemical defense than young leaves? These questions were addressed through an ant-exclusion experiment in which two branches of Copaifera langsdorffii (n = 25) were marked and monitored throughout the entire foliar expansion and development period. A reduction in the abundance of ants throughout foliar development was observed. The ants exerted an effective defense against herbivores on C. langsdorffii: the branches where ants were excluded had a greater number of herbivores. The mature leaves possessed a greater index of leaf sclerophylly than young leaves, but the leaves did not differ in the concentration of tannins. The foliar ontogeny of C. langsdorffii promoted an inversion in the defense strategy against herbivores, and despite showing an opportunistic relationship, the interaction between ants and extrafloral nectaries appears to play an important role in structuring the interactions between herbivorous insects and their host plants.     

Ontogenic change in leaf shape and crown form of a tropical tree,Scaphium macropodum (Sterculiaceae) in Borneo

Crown architecture was analyzed forScaphium macropodum (Sterculiaceae), a common shade-tolerant emergent tree of a tropical rain forest in West Kalimantan, Indonesia. Saplings and poles shorter than 12 m in height had no branches, and gathered their leaves at the ends of the stem. The leaves changed from entire to palmately-parted with increasing tree size. The parted leaves increased the light penetration through the clustered foliage. The size of leaves including the blade and petiole ranged from 22 cm to 147 cm. Because the weight of petiole per blade increased with leaf size, the leaf could not be enlarged infinitely. Taller trees with lateral branches bore small (about 40 cm in length) entire leaves. The light intensity in the forest increased from the ground to about 12 m tall and was nearly constant from 12 m to 18 m. Crown architecture ofS. macropodum adapted to this light environment. The monoaxial trees lower than 12 m could thus increase the amount of light with vertical elongation, and the branched trees higher than 12 m could increase it by means of lateral extension of crown area.     

Developmental and physiological correlates of leaf size in Hyeronima alchorneoides (Euphorbiaceae)

The tropical emergent tree Hyeronima alchorneoides has large decreases in leaf size with tree age: 1200 cm(2) at 1 yr, 900 cm(2) at 3 yr, 200 cm(2) at 11 yr, and 80 cm(2) in old (>30 yr) individuals. We tracked leaf growth and physiological attributes on trees of three different ages (1, 3, and 11 yr) to determine the developmental basis and functional consequences of this variation. Leaves on young trees grew faster and sustained maximum rates of leaf expansion longer than leaves on older trees. Leaf mass per area (LMA) did not differ among age classes. Maximum photosynthetic rates reflected differences in leaf nitrogen concentration, in which leaves from the lower crown of younger trees outperformed those at a comparable crown position in older trees. One-year-old trees had the lowest stomatal conductance and the greatest instantaneous water use efficiency. Ontogenetic plasticity in mature leaf size, structure, and physiology may be a balance between the advantages conferred by rapid height growth when trees are young and the benefits derived from producing branches that increase light harvesting ability as trees reach the canopy.     

Whole-tree sap flow is substantially diminished by leaf herbivory

Ecohydrological models consider the relationship between tree size and structure (especially leaf area index) and water use but generally treat herbivory as a source of unwanted noise in the data. Little is known of how insect damage to leaves influences whole-plant water use in trees. Water use is driven by environmental demand and the total leaf area through which transpiration can occur, but the effects of insects are expected to be complex. Different kinds of insects could have different effects; for example, chewing insects reduce leaf area, whereas sucking and tissue mining insects reduce leaf function without reducing area. Further, plants respond to herbivory in a range of ways, such as by altering leaf production or abscising leaves. We examined the effect of insects on Eucalyptus blakelyi in a woodland near Canberra, Australia, using sap flow velocity as a measure of whole-plant water use. We applied insecticide to 16 trees matched to an untreated control group. After 6 months, we examined the effects on sap flow velocity and crown condition. There was a general increase in sap flow velocity as trees produced leaves over the growing season, but the increase in sap flow for trees without insecticide protection was half that of the protected trees (increase: 4.4 vs. 9.0 cm/h, respectively). This dramatic effect on sap flow was consistent with effects on crown condition. Unprotected trees had 20% less leaf mass per unit stem in the crown. In addition, unprotected trees had a 20% greater loss of leaf functional area from necrosis. It should be noted that these effects were detected in a year in which there was not an outbreak of the psyllids (Homoptera) that commonly cause severe leaf damage to this tree species. It is predicted that the effect in a psyllid outbreak year would be even more substantial. This result underscores the significant impact that insect herbivores can have on an ecological process of significance to the ecosystem, namely, the movement of water from the soil to the atmosphere.     

不同生境栓皮栎天然更新幼苗植冠构型分析

栓皮栎存在于秦岭南坡的多种林分中,生活在不同生境中的个体往往形成不同的树冠形态和构型特征。为了说明不同生境条件下栓皮栎幼苗的植冠构型变化,采用典型抽样法,对秦岭南坡3种生境中(林冠下、林隙、林缘)的栓皮栎天然更新幼苗的侧枝、叶片特征及其空间分布进行了调查分析,结果表明:3种不同生境中栓皮栎幼苗植冠形态发生了明显的可塑性变化,(1)林冠下的幼苗明显为开阔型树冠,林隙和林缘处的幼苗树冠相对紧密;(2)幼苗的1级侧枝密度与分枝角度在3种生境下均差异显著(P0.05);从Ⅰ到Ⅳ层,林冠下幼苗的分枝角度在冠层内变化幅度不到5°,而林缘处幼苗的分枝角度变化高达40°;发生5个以上1级侧枝的概率以林冠下最大,为0.6;(3)从林缘、林隙到林冠下,幼苗的叶长、叶宽、单叶面积、叶面积指数逐渐降低,数量叶密度和比叶面积则逐渐增大,与其它两种生境相比,林冠下幼苗的叶片逐渐向树冠上层集中,且以更高序的侧枝为主要着生枝条;(4)林隙中栓皮栎幼苗的树高、地径明显优于林缘和林冠下,缩短了苗木进入主林层的时间,林隙对栓皮栎种群更新有利。在今后栓皮栎林的经营中,可以通过适当间伐来增加林隙数量,为森林更新和结构的优化的提供有利条件。     

The relationship between bark peeling rate and the distribution and mortality of two epiphyte species

Tree bark characteristics influence epiphyte establishment and survival and consequently the way in which epiphytes are distributed on trees. Tree species with peeling bark have been reported as poor epiphyte hosts. We analyzed the distribution and seedling mortality of two Tillandsia species (Bromeliaceae) in relation to rate of bark peeling of Bursera fagaroides (Burseraceae). The highest peeling rate (0.12% per day) took place on the trunk and the lowest rate on twigs (0.04% per day; branches ≤2 cm in diameter). The highest proportion of Tillandsia plants appeared on twigs. The distributions of juvenile and adult plants on twigs were higher than those expected based on the distribution of first-year seedlings, suggesting that on twigs, survival could be greater than on trunks and branches, canopy areas where peeling is faster. On the trunk and branches, in contrast, the proportion of juveniles and adults were similar to or less than that expected for first-year seedlings. The main cause of mortality was peeling and the area of minor overall mortality was the trunk, suggesting that this area should be favored as the main distribution area for the Tillandsia species but is not. Our results show that the peeling rate of B. fagaroides depends on branch size and suggest that the Tillandsia distribution depends not only on peeling rate but also on seed dispersion. We suggest that to colonize B. fagaroides epiphytes would either have adaptations to counteract the peeling rate or should occur in the areas of lowest peeling rate located in the exterior crown of trees.     

Leaf dynamics and insect herbivory in a Eucalyptus camaldulensis forest under moisture stress

Abstract The influence of soil moisture content on leaf dynamics and insect herbivory was examined between September 1991 and March 1992 in a river red gum (Eucalyptus camaldulensis) forest in southern central New South Wales. Long-term observations of leaves were made in trees standing either within intermittently flooded waterways or at an average of 37. 5m from the edge of the waterways. The mean soil moisture content was significantly (P≤0.05) greater in the waterways than in the non-flooded areas. Trees in the higher soil moisture regime produced significantly larger basal area increments and increased canopy leaf area. This increase in canopy leaf area was achieved, in part, through a significant increase in leaf longevity and mean leaf size. Although a greater number of leaves was initiated and abscissed per shoot from the non-flooded trees, more leaves were collected from litter traps beneath the denser canopies of the flooded trees. Consumption of foliage by insects on the trees subjected to flooding compared to the non-flooded trees was not significantly different. However, the relative impact of insect herbivory was significantly greater on the non-flooded trees. Leaf chewing was the most common form of damage by insects, particularly Chryso-melidae and Curculionidae. No species was present in outbreak during this study. Leaf survival decreased as the per cent area eaten per leaf increased. In addition, irrespective of the level of herbivory, leaf abscission tended to be higher in E. camaldulensis under moisture deficit. The influence of soil moisture content on the balance between river red gum growth and insect herbivory is discussed.     

Nonglandular leaf trichomes as short-term inducible defense of the grey alder,Alnus incana (L.), against the chrysomelid beetle,Agelastica alni L.

Summary The grey alder compensates leaf area losses due to insect grazing by continuously producing new leaves throughout the vegetative period. Different degrees of defoliation were attained experimentally by a controlled release of the oligophagous beetle Agelastica alni on arbitrarily selected trees from a homogenous population of young alders. The reduction in leaf area per tree significantly influenced the density of leaf trichomes, assessed 10–30 days later, on newly sprouting leaves only. Cross-correlations between leaf area reduction and trichome density were strongest for leaves which completed unfolding 14–21 days after damage. Dualchoice assays suggested a negative influence of trichomes on oviposition rate of A. alni. Removal of trichomes by shaving demonstrated the highly significant effect of trichomes on feeding behavior of adults and larvae in dual-choice assays. The role of the induced increase in trichome density as a possible short-term defense reaction against herbivorous insects is discussed.     

Canopy Herbivory and Insect Herbivore Diversity in a Dry Forest–Savanna Transition in Brazil

This study aimed to compare canopy herbivore diversity and resultant insect damage to vegetation in two distinct and adjacent ecosystems, specifically a dry forest ecosystem and a cerrado (savanna) ecosystem that occur together in an abrupt transition zone in southeastern Brazil. In the dry forest, the canopy was reached using a single rope climbing technique, whereas the shorter canopy of the cerrado was assessed using a 7 m ladder. Insect specimens were collected by beating the foliage, and 20 representative leaves were collected to calculate the specific leaf mass (SLM) and leaf area loss through herbivory. Also, we collected ten soil samples from each habitat to determine soil nutrient content. We sampled 118 herbivorous insects from ten families, mostly in dry forest trees (96 individuals belonging to 31 species). A higher abundance of chewing and sap-sucking insects were observed in dry forest trees than in cerrado trees. The same pattern was observed for the richness of chewers, with a higher degree of diversity of chewers found in dry forest trees than in cerrado trees. Herbivorous insects were not affected by SLM regardless of guild and habitat. However, we observed a negative correlation between the herbivory rate and the specific leaf mass (SLM). The cerrado trees showed a higher SLM and lower herbivory rates than trees occurring in the dry forest. These results suggest that herbivory rates in the transition dry forest–cerrado may be driven by soil nutrient content, which is thought to influence leaf sclerophylly.
Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp .     

胡杨枝芽生长特征及其展叶物候特征

以5个不同发育阶段的胡杨(Populus euphratica Oliv.)个体为研究对象,观测记录了枝芽展叶物候、枝芽生长特征和叶形变化的空间分布规律。结果表明:不同发育阶段的胡杨个体以及同一个体树冠的不同层次,其枝芽生长及其展叶物候期表现出不同的时空特征。随着树龄的增加和树冠层次的增高(由基向顶),当年新生枝条长度、枝条叶片数和叶形指数逐渐减小,但叶面积和叶片干重逐渐增大。5个不同发育阶段胡杨个体均表现出展叶物候始于树冠顶层,依次向下结束于树冠基部;展叶物候期共性表现在枝芽萌动期均在4月上旬,起始展叶期集中在4月中旬,展叶终期则在5月上旬到下旬;树龄较大的个体其枝芽萌动期、起始展叶期、展叶终期较树龄较小的个体早;其枝芽萌动期到展叶终期的时间进程较树龄较小的个体短;不同发育阶段的个体枝芽萌动期出现的时间较为离散,起始展叶期和展叶终期出现的时间较为集中。相关分析表明,出叶周期与枝条长度、枝条叶片数量和叶形指数呈极显著正相关,与叶面积和叶片干重呈显著负相关。     

Spatial variation in sapwood area to leaf area ratio and specific leaf area within a crown of silver birch

Spatial variation in sapwood area to leaf area ratio (Huber value, HV) and specific leaf area (SLA) was examined in branches of closed-canopy trees of silver birch (Betula pendula Roth). HV increased basipetally within a crown and decreased with increasing branch order, but exhibited no significant radial trend along a primary branch. HV was primarily determined by branch position in a crown and branch diameter at the sampling point, being independent of the size of the tree and branch. Greater HV in the lower-crown branches is considered a means to mitigate differences in hydraulic transport capacity between the branches located in different canopy layers. Beside branch position and sampling location on a branch, SLA depended significantly on several other variables characterising tree and branch size. SLA increased basipetally within a crown and along a primary branch, but exhibited no significant trend with branch orders. Because height caused leaf area (A_L) to diminish more rapidly than leaf dry weight, A_L primarily determined the vertical variation in SLA.     

The occurrence of non-ring producing branches in Abies lasiocarpa

Lack of annual growth ring production at the base of branches in the lower portion of the crown is a commonly observed phenomenon. In this study, branches with missing rings were found on 47 of 49 Abies lasiocarpa trees sampled. The number of missing rings on the lowest live branch in the crown averaged 12, and ranged as high as 28. The lower one-third of the live crown tended to consist of branches without rings; these branches contained an average of 30% of the total crown leaf area. The ratio of foliage weight to total branch weight, in combination with position of the branch in the canopy, was an effective discriminator of non-ring producing branches. This suggests that both structural and environmental factors influence the cessation of ring production. The potential ecological implications of branches that fail to produce rings are discussed.     

亚热带森林附生植物叶片气孔特征及其可塑性对光照变化的响应

附生植物是热带亚热带森林生态系统中物种多样性极高且极其脆弱敏感的生物类群之一。光照被认为是促进附生植物由陆生类群演化而来并决定其生长和分布的关键因素。然而,由于接近林冠和规范性采样的限制,附生植物与光照的关系仍亟待阐述。为揭示附生植物对光强变化的响应和适应策略,该研究以亚热带常绿阔叶林6种附生植物(林冠层木本:鼠李叶花楸、毛棉杜鹃;林冠层草本:狭瓣贝母兰、毛唇独蒜兰;树干区草本:点花黄精、距药姜)为对象,对其在4个光处理梯度下生长的叶片气孔特征及其可塑性进行了对比分析。结果表明:(1) 2种附生小乔木的气孔面积(SA)、气孔密度(SD)、潜在气孔导度指数(PCI)和表皮细胞密度(ECD)均对光强改变显著响应。2种附生兰科植物的SA最大,而SD最小;附生乔木叶片SD和ECD的光响应趋势与陆生植物更相似,而附生草本则出现种间差异。(2) 6种附生植物的气孔、表皮细胞特性及其表型可塑性,在草本-木本、常绿-落叶植物、林冠-树干区之间,均无明显差别。(3)附生植物气孔特性和表皮细胞平均可塑性指数均低于陆生植物。综上结果表明,亚热带常绿阔叶林中附生植物对于光环境变化的适应性相对较弱。不同的附生植物可以通过不同程度地增加叶片SD和ECD来适应高光强生境,并通过对SD和SA的双重调节以增大潜在光合能力从而应对低光胁迫。     

Seasonality of insect herbivory on the leaves of Neoboutonia macrocalyx in the Kibale National Park, Uganda

The seasonality of herbivory on the leaves of Neoboutonia macrocalyx Pax. in Kibale Forest National Park, Uganda, was studied. A total of 2929 fallen leaves was collected during 15 months under randomly-selected trees in three different habitats; natural forest and two selectively cut forest sites. The percentage of leaf area eaten and leaf size were estimated. Leaf herbivory was highly seasonal and correlated with rainfall in the previous 2 months, but less than 100 mm monthly rainfall had no effect. There was no correlation between leaf size and rainfall. Although Kibale Forest has two wet seasons, insect feeding on leaves had only one peak during the major rainy season from September to December. Three to four months after peak herbivory, leaves had very low rates of insect damage. Habitat had only a small effect on the amount of insect feeding. The sampling time accounted for 71% of variation in leaf herbivory. New leaves were formed continuously year-round. The constant leaf production by Neoboutonia trees may be an adaptation to escape generalist herbivorous insects which might be synchronized with the major wet season when the leaf flush of the most other deciduous species occurs. Thus, the availability of fresh leaves is not acting as a regulating factor in seasonality of Neoboutonia herbivory.     

The effects of tree characteristics on rainfall interception in urban areas

Trees in urban areas have significant effects on the urban ecosystem. They can be used to improve the water cycle in urban areas by increasing evaporation and reducing runoff through rainfall interception. Street trees placed in planters on impervious areas reduce runoff by intercepting rainfall and by temporarily storing raindrops on leaves. Therefore, understanding tree canopy geometry and the effect of rainfall interception is important in urban hydrology. In this study, we assessed the effect of tree canopy morphology on rainfall interception using four major street tree species, Sophora japonica L., Ginkgo biloba L., Zelkova serrata (Thunb.) Makino, and Aesculus turbinata Blume, in Seoul, South Korea. We measured throughfall for each tree and also derived three-dimensional data of tree canopy morphology with a terrestrial laser scanner. Tree height, canopy crown width, leaf area index (LAI), leaf area density, mean leaf area, and mean leaf angle were used to determine canopy morphology. The interception rate was mostly affected by the LAI; a higher LAI tended to result in a higher interception rate. Leaf area affected the rainfall interception rate when trees had similar LAIs. These findings on individual tree canopy rainfall interception can help us to understand the importance of rainfall interception in hydrology and for ecological restoration when planning urban green spaces.

     

Variation in shoot mortality within crowns of severely defoliated <Emphasis Type="Italic">Betula maximowicziana</Emphasis> trees in Hokkaido,northern Japan

To clarify mortality patterns of current-year shoots within the crown of Betula maximowicziana Regel after severe insect herbivory in central Hokkaido, northern Japan, we investigated the degree of defoliation, pattern of shoot development, shoot mortality, and leaf tissue-water relations. One hundred current-year long shoots growing in a B. maximowicziana plantation were observed for defoliation and mortality in June 2002. An outbreak of herbivorous insects (Caligula japonica and Lymantria dispar praeterea) occurred in the stand in mid-to-late June, and the monitored shoots were defoliated to various degrees. Within 1 month of defoliation, some of the severely defoliated shoots had produced new leaves on short shoots that had emerged from axillary buds. Stepwise logistic regression revealed that the probability that current-year long shoots would put out axillary short shoots with leaves is closely related to the degree of defoliation. To evaluate the water relations of the leaves, we determined pressure–volume curves for the leaves that survived the herbivorous insect outbreak and the new leaves that emerged after defoliation. The water potential at turgor loss (Ψ_l,tlp) and the osmotic potential at full turgidity (Ψ_π,sat) were higher for the new leaves than for the surviving leaves, indicating a lower ability to maintain leaf cell turgor against leaf dehydration in the new leaves. Of the 100 shoots, 13 died after the emergence of new leaves. Stepwise logistic regression revealed that the probability that the long shoots would die generally increased with the emergence of new leaves, with increasing shoot height. This result suggests that the combined effect of the vulnerability of newly emerged leaves and low water availability, associated with higher shoot positions within the crown, caused shoot mortality. Based on our results, some possible mechanisms for mortality in severely defoliated B. maximowicziana are discussed.