散孔材与环孔材树种枝干、叶水力学特性的比较研究

为揭示散孔材与环孔材树种树木水分生理特性的差异,选取了常见的3种散孔材落叶树种(毛白杨、法国梧桐和樱花)和3种环孔材落叶树种(刺槐、合欢和白蜡),研究了其枝干与叶水力学性质的差异及其协调性。结果表明:3种环孔材树种枝干横截面积基础上的最大比导水率(Ks-max)大于3种散孔材树种,但其木质部对空穴化的脆弱性(P50branch)高于散孔材树种,6种树木枝干的水分传输能力和抵抗空穴化能力之间存在一种相互制约的权衡关系。3种散孔材与3种环孔材树种的叶最大水力导度(Kl-max)和水力脆弱性(P50leaf)并无显著差异;对于3种散孔材树种,叶的水力脆弱性要高于枝干,但对3种环孔材树种而言,枝干的水力脆弱性要高于叶。6种树木枝干和叶的水力学性质(Kmax、P50)之间并无相关关系。这些结果表明:散孔材与环孔材树种的枝干水力学特性有明显差异,但叶水力学特性无差异;枝干与叶水力学性质之间是相互独立的。     

Weak relationships between leaf phenology and isohydric and anisohydric behavior in lowland wet tropical forest trees

Wet tropical forest trees display a wide range of leaf phenology dynamics. However, the interrelation between deciduousness, water status, and leaf and stem characteristics have been poorly investigated compared with dry forests. We studied wet forest trees to answer the following questions: (1) do water regulation modes (iso/anisohydric behavior) of evergreen species differ from those found in deciduous species? (2) Does leaf water potential (Ψ_L) influences leaffall and emergence dynamics? (3) Are leaf and stem characteristics consistent across evergreen and deciduous trees? We evaluated vegetative phenology, Ψ_L, and leaf and stem characteristics of six evergreen and three deciduous species monthly for 2 yr. Species exhibited different leaffall and emergence dynamics, as well as different water regulation modes, independent of their deciduousness. Thus, the relationship between leaf phenology and water regulation behaviors appears to be a species‐specific property rather than a functional group attribute. Ψ_L had no direct influence on the dynamics of leaffall and/or emergence, indicating that this process is not modulated by water availability alone. Individual groups of evergreen and deciduous species could not be identified using principal component analysis (PCA), but a decoupling was observed in the leaf and stem economics spectra. The lack of an interrelation between deciduousness and iso/anisohydry, as well as the independence of leaf and stem trade‐offs, emphasizes that more systematic measurements of vegetative phenology and ecophysiological characteristics are necessary to advance our knowledge of leaf habit and water regulation behaviors based on the functional traits of wet forest plants.     

Correlations of climate and plant ecology to leaf size and shape: potential proxies for the fossil record

The sizes and shapes (physiognomy) of fossil leaves are widely applied as proxies for paleoclimatic and paleoecological variables. However, significant improvements to leaf-margin analysis, used for nearly a century to reconstruct mean annual temperature (MAT), have been elusive; also, relationships between physiognomy and many leaf ecological variables have not been quantified. Using the recently developed technique of digital leaf physiognomy, correlations of leaf physiognomy to MAT, leaf mass per area, and nitrogen content are quantified for a set of test sites from North and Central America. Many physiognomic variables correlate significantly with MAT, indicating a coordinated, convergent evolutionary response of fewer teeth, smaller tooth area, and lower degree of blade dissection in warmer environments. In addition, tooth area correlates negatively with leaf mass per area and positively with nitrogen content. Multiple linear regressions based on a subset of variables produce more accurate MAT estimates than leaf-margin analysis (standard errors of ±2 vs. ±3°C); improvements are greatest at sites with shallow water tables that are analogous to many fossil sites. The multivariate regressions remain robust even when based on one leaf per species, and the model most applicable to fossils shows no more signal degradation from leaf fragmentation than leaf-margin analysis.     

Deciduousness in tropical trees and its potential as indicator of climate change: A review

In tropical forests, deciduousness is an outcome of integrated effect of drought, tree characteristics and soil moisture conditions and thus it is a reliable indicator of seasonal drought experienced by different tree species. Variations in the deciduousness are associated with several ecophysiological characteristics, such as varying allocation pattern of metabolic products, resource capture and conservation, water relations and stem water storages, annual carbon sequestration, timing of reproductive event initiation, extent of separation of vegetative and reproductive events and leaf strategies, and it helps in maintenance of water balance and protection of tree organs during the seasonal drought. Tropical forests support mosaics of tree functional types showing marked differences in the duration of deciduousness (from leaf exchanging to >8 months deciduous), as a result of varying degree of water stress experienced by physiognomy, distribution and wood anatomy of tropical trees. Wide variations in deciduousness in the same species growing at different sites suggest the high sensitivity of tropical trees to small changes in growing habitat. In the present review we have explored the ecological significance of deciduousness in tropical trees with emphasis on: (a) inter- and intraspecies plasticity in deciduousness, (b) various capacity adaptations related with the duration of deciduousness, (c) relationship between tree stem water status and deciduousness, and (d) probable effect of impending climate change on tropical trees. An attempt has also been made to establish deciduousness as climate change indicator in the dry tropics. There is need to develop capabilities to detect and predict the impact of climate change on deciduousness through long-term phenological network in tropics. Remote sensing techniques can generate valuable ecological information such as leaf level drought response and phenological patterns. Deciduousness has the potential to emerge as an important focus for ecological research to address critical questions in global modeling, monitoring, and climate change.     

Plant functional types broadly describe water use strategies in the Caatinga,a seasonally dry tropical forest in northeast Brazil

1. In seasonally dry tropical forests, plant functional type can be classified as deciduous low wood density, deciduous high wood density, or evergreen high wood density species. While deciduousness is often associated with drought‐avoidance and low wood density is often associated with tissue water storage, the degree to which these functional types may correspond to diverging and unique water use strategies has not been extensively tested.
2. We examined (a) tolerance to water stress, measured by predawn and mid‐day leaf water potential; (b) water use efficiency, measured via foliar δ¹³C; and (c) access to soil water, measured via stem water δ¹⁸O.
3. We found that deciduous low wood density species maintain high leaf water potential and low water use efficiency. Deciduous high wood density species have lower leaf water potential and variable water use efficiency. Both groups rely on shallow soil water. Evergreen high wood density species have low leaf water potential, higher water use efficiency, and access alternative water sources. These findings indicate that deciduous low wood density species are drought avoiders, with a specialized strategy for storing root and stem water. Deciduous high wood density species are moderately drought tolerant, and evergreen high wood density species are the most drought tolerant group.
4. Synthesis. Our results broadly support the plant functional type framework as a way to understand water use strategies, but also highlight species‐level differences.

     

Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications

? Paleobotanists have long used models based on leaf size and shape to reconstruct paleoclimate. However, most models incorporate a single variable or use traits that are not physiologically or functionally linked to climate, limiting their predictive power. Further, they often underestimate paleotemperature relative to other proxies. ? Here we quantify leaf-climate correlations from 92 globally distributed, climatically diverse sites, and explore potential confounding factors. Multiple linear regression models for mean annual temperature (MAT) and mean annual precipitation (MAP) are developed and applied to nine well-studied fossil floras. ? We find that leaves in cold climates typically have larger, more numerous teeth, and are more highly dissected. Leaf habit (deciduous vs evergreen), local water availability, and phylogenetic history all affect these relationships. Leaves in wet climates are larger and have fewer, smaller teeth. Our multivariate MAT and MAP models offer moderate improvements in precision over univariate approaches (± 4.0 vs 4.8°C for MAT) and strong improvements in accuracy. For example, our provisional MAT estimates for most North American fossil floras are considerably warmer and in better agreement with independent paleoclimate evidence. ? Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions. This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf-climate relationships.     

Leaf growth pattern in evergreen and deciduous species of the Central Himalaya,India

Leaf growth patterns were investigated in 11 evergreen (with leaf life-spans of just more than 1 year) and 15 deciduous species, occurring along an elevational gradient of 600–2200 m elevation in the Central Himalaya. Records were made of the leaf initiation period, leaf population dynamics, leaf expansion, leaf mass changes, leaf longevity and related parameters. Species of both groups produced leaves at similar rates during March to April, the driest period of the year. Species of both groups had approximately fully developed foliage during the warm, wet period (mid-June to mid-September) of the monsoon. However, significant differences were found at group level in other characters: shoot length (19.5 cm per shoot for deciduous and 11.7 cm for evergreen species); leaf population per 10 cm shoot length (4.7 vs 15.0); leaf area (107.9 vs 41.4 cm²/ leaf); specific leaf mass (106.9 vs 191.3 g/m²); and leaf mass loss after the monsoon period, being rapid and higher (31.6%) in deciduous species and slow and limited in the evergreens (26.2%). However, species of the two groups showed considerable overlaps in the values of above characters. The evergreen species of the Central Himalaya resembled the deciduous species of the region more than the multi-year leaves of clearly evergreen species. The evergreens bear leaves throughout the year, but like deciduous species bear the cost of annual replacement of old leaves by new leaves. They seem to outcompete deciduous species by producing annually a greater mass of leaves of low-carbon cost (per unit leaf mass), which is capable of conducting photosynthesis all year round. A situation of less marked contrast between favourable and nonfavourable periods, with respect to temperature, seems to favour the leaf characters of the evergreens.     

Plant growth-form alters the relationship between foliar morphology and species shade-tolerance ranking in temperate woody taxa

Variation in leaf size (area per leaf) and leaf dry weight per area (LWA) in relation to species shade- and drought-tolerance, characterised by Ellenberg's light (ELD) and water demand (EWD) values, respectively, were examined in 60 temperate woody taxa at constant relative irradiance. LWA was independent of plant size, but leaf size increased with total plant height at constant ELD. Canopy position also affected leaf morphology: leaves from the upper crown third had higher LWA and were larger than leaves from the lower third. Leaf size and LWA were negatively correlated, and leaf size decreased and LWA increased with decreasing species shade-tolerance. Mean LWA was similar for trees and shrubs, but trees had larger leaves than shrubs. Furthermore, all relationships were altered by plant growth-form: none of the qualitative tendencies was significant for trees. This implies the considerably lower plasticity of foliar parameters in trees than those in shrubs. Accordingly, shade-tolerance of trees, having relatively constant leaf structure, may be most affected by the variability in biomass partitioning and crown geometry which influence foliage distribution and spacing and finally determine canopy light absorptance. Alteration of leaf form and investment pattern for construction of unit foliar surface area which change the efficiency of light interception per unit biomass investment in leaves, is a competitive strategy inherent to shrubs. EWD as well as wood anatomy did not control LWA and leaf size, though there was a trend of ring-porous tree species to be more shade-tolerant than diffuse-porous trees. Since ring-porous species are more vulnerable to cavitation than diffuse-porous species, they may be constrained to environments where irradiances and consequently evaporative demand is lower.     

Network analysis of tree crowns distinguishes functional groups of Cerrado species

Deciduous, semideciduous and evergreen leaf phenological groups of Cerrado trees were studied using a representative network composed of nodes and links to uncover the structural traits of the crown. A node denotes the origin of a branch, and a link represents the branch emerging from a lateral bud. The network representation usually resulted in a graph with three links per node and twice as many links as nodes for each leaf phenological group. It was possible to identify four kinds of nodes according to the position and the number of links: initial, regular, emission and final nodes. The numbers of links and nodes and the distance between two kinds of nodes decreased from evergreen to deciduous species. A crown with a few nodes and links and a short distance between the kinds of nodes could facilitate the unfolding of foliage on leafless branches at the end of the dry season in deciduous trees. In contrast, foliage persistence in evergreens could facilitate the mass flow to new leaves produced during the entire year in a crown with a high number of links and nodes and with a large distance between nodes. There is a clear interdependence between the degree of leaf deciduousness and the crown structural traits in Cerrado tree species. Therefore, there are functional groups of trees in Cerrado vegetation that are characterized by a set of structural traits in the crown, which is associated with leaf deciduousness.     

Responses of leafing phenology and photosynthesis to soil warming in forest-floor plants

Phenological and physiological responses of plants to climate change are key issues to understand the global change impact on ecosystems. To evaluate the species-specific responses, a soil-warming experiment was conducted for seven understory species having various leaf habits in a deciduous forest, northern Japan; one evergreen shrub, one semi-evergreen fern, one summer-deciduous shrub, and four summer-green herbs. Soil temperature in the warming plots was electrically maintained 5 °C higher than control plots. Responses of leafing phenology highly varied among species: new leaf emergence of the evergreen shrub was delayed; senescence of overwintering leaves of the semi-evergreen fern was accelerated resulting in the shift to deciduousness; leaf shedding of the summer-deciduous shrub was accelerated. Among four summer-green species, only an earliest leaf-out species advanced growth initiation, but the period of growth season was not changed. Physiological responses to soil warming were also highly species-specific: the warming treatment increased the photosynthetic activity of the summer-deciduous shrub and one summer-green species, decreased that of the semi-evergreen fern, while other species did not show any changes in photosynthetic traits. Totally, the soil warming impacts on understory plants was apparent in spring. It was suggested that modification of snow conditions is important issue especially for plants with overwintering leaves. Responses of understory vegetation to climate change may highly vary depending on the composition of leaf habits in the cool-temperate forests.     

Hydraulic failure and tree dieback are associated with high wood density in a temperate forest under extreme drought

Catastrophic hydraulic failure will likely be an important mechanism contributing to large‐scale tree dieback caused by increased frequency and intensity of droughts under global climate change. To compare the susceptibility of 22 temperate deciduous tree and shrub species to hydraulic failure during a record drought in the southeastern USA, we quantified leaf desiccation, native embolism, wood density, stomatal conductance and predawn and midday leaf water potential at four sites with varying drought intensities. At the two driest sites, there was widespread leaf wilting and desiccation, and most species exhibited predawn leaf water potentials of ≤3 MPa and >60% loss of xylem conductivity in branches. Although species with high wood density were more resistant to cavitation, they had higher levels of native embolism and greater canopy dieback than species with low wood density. This unexpected result can be explained by the failure of species with dense wood to avert a decline in water potential to dangerous levels during the drought. Leaf water potential was negatively correlated with wood density, and the relationship was strongest under conditions of severe water deficit. Species with low wood density avoided catastrophic embolism by relying on an avoidance strategy that involves partial drought deciduousness, higher sensitivity of stomata to leaf water potential and perhaps greater rooting depth. These species therefore maintained water potential at levels that ensured a greater margin of safety against embolism. These differences among species may mediate rapid shifts in species composition of temperate forests if droughts intensify due to climate change.     

The Deciduous Behavior of a Tropical Plant, Plumeria acuminata

The deciduous behavior of the tropical perennial Plumeria acuminata Ait., cultivar Sherman White, was investigated. The temperature during the period of experiment varied only 3°C, the mean maxima and minima, respectively, being; 28.5° and 23.5°C for summer months and 25.5° and 20.6°C for winter months. The length of the day-light period ranged from 14¼ hours on the longest day in June to 11¾ hours on the shortest day in December. Under naturally prevailing conditions of temperature and day-lengths, cessation of leaf formation and shedding of foliage occurred during the longer-night, autumn-winter months. The shedding was manifested in two stages: from mid-October to mid-January there was a slow but steady decrease in the number of leaves per plant, and in late January there occurred an abrupt abscission of all remaining leaves. Light interruptions during the middle of each night prevented a net loss in foliage as well as the en masse shedding in late January. Stem elongation was retarded during the autumn-winter months, but its rate was fully restored when the long nights were interrupted with artificial light. Flowering was unaffected by day-length. On the basis of these observations it is concluded that the deciduous behavior of Plumeria and perhaps other tropicals, alike temperate climate species, is governed by photoperiod. Cessation of leaf formation and en masse shedding of foliage are induced by long nights. However, in contrast to temperate zone plants, in which deciduousness is an adaptation against the winter cold and freeze, deciduousness provides tropical plants a survival advantage, perhaps, against seasonally recurring droughts.     

Functional groups of woody species in semi‐arid regions at low latitudes

In seasonally dry environments, woody species have different survival strategies. However, little is known about how environmental variables affect the phenology and water dynamics of these species. We aim to understand which variables initiate the vegetative phenophases of species in a tropical semiarid climate at 3°S latitude, where variation in photoperiod is minimal and rainfall is seasonal. We hypothesize that groups of species with similar vegetative phenologies, under similar conditions, are functionally similar in terms of water storage and use. We analyse the relationship between functional characteristics related to the acquisition and utilization of water, such as wood density, water storage capacity, water potential and vegetative phenology. The attributes were ordered by multidimensional scaling, and a multiple response permutation procedure was used to test consistency of the groups. Canonical correspondence analysis and Mantel tests were used to evaluate the phenophase response to environmental variables. We found four functional groups: (i) deciduous low wood density, which lose 75% of their leaves one month before the end of the rains; (ii) evergreen high wood density; (iii) early deciduous high wood density, which lose 75% of their leaves one month after the end of the rains; and (iv) late deciduous high wood density, which lose 75% of their leaves two months after the end of the rains. As expected, the vegetative phenodynamics of the deciduous high wood density group were mainly influenced by water availability. The evergreens did not show a correlation with rainfall. Only leaf shedding of the late deciduous, and the vegetative phenophases of the evergreens, responded to an increase in temperature and photoperiod. Bud‐break responded to increased photoperiod and soil humidity in the deciduous low wood density group. The foliar periodicity groups can be explained by the presence of species that differ mainly in their mechanisms of water acquisition and use.     

Relationship between the timing of vessel formation and leaf phenology in ten ring-porous and diffuse-porous deciduous tree species

The goal of this study is to clarify how different aspects of plant function are coordinated developmentally for species of ring-porous versus diffuse-porous deciduous trees, comparing the timing of leaf phenology and vessel formation in twigs and stems from an ecophysiological viewpoint. Cylindrical stem cores and twigs were collected at intervals from early spring through summer from five ring-porous and five diffuse-porous species in a cool temperate forest, and leaf and vessel formation were observed simultaneously. We found that the first-formed vessels of the year were lignified in twigs around the time of leaf appearance and at or before full leaf expansion of each tree in both groups of species with flush-leaves. Vessels in stems were lignified 2 weeks before to 4 weeks after leaf appearance and before or around full leaf expansion of the tree in ring-porous species. This was significantly earlier than in diffuse-porous species, in which stem vessel lignification was 2–8 weeks after leaf appearance and at or after full leaf expansion of the tree. The timing of vessel formation in twigs compared to stems was significantly earlier in ring-porous species than in diffuse-porous species. Lignification of vessels in stems occurred within 2 weeks of lignification in the twigs of ring-porous species and 2–8 weeks after lignification in twigs of diffuse-porous species. These results indicate the order and time-lag of leaf and vessel formation. Ring-porous species showed intensive leaf/vessel production, whereas diffuse-porous species showed less intensive leaf/vessel production.     

Assessing the response of plant functional types to climatic change in tropical forests

Abstract. We propose and test a classification of plant functional types for tropical trees based on demography, growth form, phenology, and moisture requirements, using data from a 50-ha forest dynamics plot in Panama. Correlations among demographic variables for individual species - mortality, growth, and the tendency to colonize light gaps - were strong, and a single principal component (PC) accounted for a large fraction of the demographic variability. Most species - shade-tolerants - were clustered at the low end of the PC axis (low growth, low mortality), while the rest were continuously distributed over a wide range. Three demographic guilds could be defined from scores on this axis: we call these pioneer, building phase, and shade-tolerant trees, following earlier terminology. Leaf lifetime correlated negatively with the demographic axis, and there was a weak relationship between demography and moisture-preference: no species with high demographic scores also had high moisture requirements. There was no significant relationship between deciduousness and the demographic axis, but deciduousness was negatively correlated with leaf lifetime and moisture index. Altogether, 11 different combinations of demographic variables, deciduousness, moisture needs, and growth form (canopy vs. understory species) were identified. We evaluated how these functional types changed in abundance between 1982 and 1995. Because of a recent run of dry years and long dry seasons, we predicted that deciduous species, canopy species, pioneers, and drought-tolerant species would be increasing at the expense of their counterparts. Only one aspect of this prediction was borne out: moisture- demanding species declined sharply in abundance relative to drought-tolerant species. Neither deciduousness nor growth form was associated with population change, and pioneer species declined in abundance more often than shade-tolerants. The overall structure of the forest - the density of deciduous, pioneer, and understory species - did not change much, but the decline of the moisture-demanding guild indicates that a change in composition is preceding a structural change.     

长白山阔叶红松林5种主要树种水分利用效率与叶片养分特征

以长白山阔叶红松林中5种优势树种(红松、水曲柳、色木槭、蒙古栎、紫椴)为研究对象,利用稳定碳同位素技术分析了植物的水分利用效率(WUE),测定了叶片碳(C)、氮(N)、磷(P)3种营养元素的含量用以分析植物对养分的利用特征,并综合分析了植物WUE与叶片养分含量之间的关系.结果 表明:冠层不同位置微气象因子的差异导致WU...     

Paleotemperature proxies from leaf fossils reinterpreted in light of evolutionary history

Present-day correlations between leaf physiognomic traits (shape and size) and climate are widely used to estimate paleoclimate using fossil floras. For example, leaf-margin analysis estimates paleotemperature using the modern relation of mean annual temperature (MAT) and the site-proportion of untoothed-leaf species (NT). This uniformitarian approach should provide accurate paleoclimate reconstructions under the core assumption that leaf-trait variation principally results from adaptive environmental convergence, and because variation is thus largely independent of phylogeny it should be constant through geologic time. Although much research acknowledges and investigates possible pitfalls in paleoclimate estimation based on leaf physiognomy, the core assumption has never been explicitly tested in a phylogenetic comparative framework. Combining an extant dataset of 21 leaf traits and temperature with a phylogenetic hypothesis for 569 species-site pairs at 17 sites, we found varying amounts of non-random phylogenetic signal in all traits. Phylogenetic vs. standard regressions generally support prevailing ideas that leaf-traits are adaptively responding to temperature, but wider confidence intervals, and shifts in slope and intercept, indicate an overall reduced ability to predict climate precisely due to the non-random phylogenetic signal. Notably, the modern-day relation of proportion of untoothed taxa with mean annual temperature (NT-MAT), central in paleotemperature inference, was greatly modified and reduced, indicating that the modern correlation primarily results from biogeographic history. Importantly, some tooth traits, such as number of teeth, had similar or steeper slopes after taking phylogeny into account, suggesting that leaf teeth display a pattern of exaptive evolution in higher latitudes. This study shows that the assumption of convergence required for precise, quantitative temperature estimates using present-day leaf traits is not supported by empirical evidence, and thus we have very low confidence in previously published, numerical paleotemperature estimates. However, interpreting qualitative changes in paleotemperature remains warranted, given certain conditions such as stratigraphically closely-spaced samples with floristic continuity.     

Periodicity of leaf growth and leaf dry mass changes in the evergreen and deciduous species of Southern Assam,India

The study described patterns of leaf dry mass change, leaf mass per area (LMA), relative growth rate and leaf life span (LL) for 14 evergreen and 7 deciduous species of a tropical forest of Southern Assam, India. Leaf expansion in both the groups was, in general, completed before June (i.e. well before the onset of monsoon rains). Although leaf dry mass during leaf initiation phase was significantly higher (P < 0.01) in evergreen species than in deciduous species, at the time of full leaf expansion, average leaf dry mass relative to the peak leaf dry mass, realised by the evergreen species was lower (66 %) than for deciduous species (76 %). Leaf dry mass increase in both groups continued after leaf full expansion. Evergreen species had a longer leaf dry mass steady phase than deciduous species (2–6 vs 2–3 months). Average LMA of mature leaves for evergreen species (77.43 g m^?2) was significantly greater than that of deciduous species (48.43 g m^?2). LL ranged from 165 days in Gmelina arborea (deciduous) to 509 days in Dipterocarpus turbinatus (evergreen). LMA was correlated positively with LL, indicating that evergreen species with higher leaf construction cost retain leaves for longer period to pay back. The average leaf dry mass loss before leaf shedding was greater (P < 0.01) for deciduous species (30.29 %) than for evergreen species (18.31 %). Although the cost of leaf construction in deciduous species was lower than for evergreen species, they replace leaves at a faster rate. Deciduous species perhaps compensate the cost involved in faster leaf replacement through higher reabsorption of dry mass during senescence, which they remobilise to initiate growth in the following spring when soil resources remain limiting.     

Do the phenology and functional stem attributes of woody species allow for the identification of functional groups in the semiarid region of Brazil?

The phenology of tree species in environments that are subject to strong climatic seasonality is mainly determined by water availability, which may vary as a function of wood density. The relationship among phenology, water potential, wood density and the capacity of water storage in the stem were determined for woody species of caatinga vegetation (dry forest) in the semiarid region of NE Brazil. Leaf flush and fall, flowering and fruiting events were recorded over a 31-month period, and the water potential was measured over a two-year period. These data were related to precipitation, water availability in the soil and photoperiod. Seven deciduous species exhibited low wood density (DLWD,?<0.5?g?cm^?3), high capacity of water storage in the stem (until 250?% of the dry weight) and high water potential during the year, as opposed to 15 deciduous species that showed high wood density (DHWD,?≥0.5?g?cm^?3). Leaf flush, flowering and the fruiting of DHWD species were related to precipitation, whereas these phenological events occurred at the end of the dry season and/or the beginning of the rainy season for DLWD species and were related to the photoperiod. The two evergreen species showed variations of water potential that were intermediate between those of DHWD and DLWD deciduous species, leaf flush during the dry season and flowering at the end of dry season. These results suggest the existence of three functional groups: evergreen species, DHWD deciduous species and DLWD deciduous species.