Effect of environmental conditions on decomposition in eight woody species of a dry tropical forest

Litter decay is a significant part of carbon budget. Due to strong environmental control, the changes in the environment may drastically influence the litter decay rates. Litter decomposition of eight dry tropical woody species, viz. Shorea robusta, Buchanania lanzan, Diospyros melanoxylon, Lagerstroemia parviflora, Lannea coromandelica, Terminalia tomentosa, Holarrhena antidysenterica and Lantana camara was studied to document the effect of intra-annual changes in the environment. Litter decomposition was monitored at monthly intervals at five sites using litter bag technique over an annual cycle in a dry tropical deciduous forest of Vindhyan highland, India. Weight loss differed among species and through months, and ranged from 15.38% in L. camara at Kotwa site in January to 30.72% in T. tomentosa at Hathinala site in August. Peak weight loss occurred in August and averaged 46.2% across species and sites. Nitrogen and phosphorus mineralization rates also varied significantly from species to species. T. tomentosa having higher nitrogen content and lower C/N ratio than other species exhibited faster weight loss. Nitrogen and phosphorus contents of litter showed significant positive correlation with weight loss. C/N ratio was negatively related to decay constant, and the weight loss was positively related to the soil surface temperature as well as soil moisture content.     

Differences in leaf phenology between juvenile and adult individuals of two tree species in a seasonally dry tropical woodland

In temperate forests, juvenile trees anticipate leaf phenology compared to adults, thus avoiding shading and herbivory. This is also expected to occur in seasonal tropical forests due to intense herbivory and shading during the rainy season; however, the anticipation of leaf phenology by juveniles in seasonal tropical forests has yet to be demonstrated. Stem‐succulent species are expected to be prone to juvenile phenological anticipation because these species are able to use water stored in their stems for leaf flushing in the dry season. We investigated this hypothesis by comparing leaf phenology (bud break, leaf expansion) of juveniles and adults of two species with contrasting wood densities in the transition between dry and rainy seasons in a tropical dry woodland. We also investigated the level of light limitation that juveniles experience in the rainy season. Both species exhibited bud break during the dry season, but only expanded their leaves with the occurrence of the first rains. In general, the stem‐succulent species had a more precocious bud break; however, anticipation by juveniles occurred only in the species with more dense wood. Canopy openness was lower than in temperate deciduous forests, but the fact that the full expansion of leaves occurred only with rainfall indicates that bud break in anticipation of canopy closure contributes only to keeping leaf photosynthetic balance from going negative, and not to higher carbon gain. The importance of anticipated budding for escaping herbivory remains an alternative explanation in need of investigation.     

Contrasting leaf chemical traits in tropical lianas and trees: implications for future forest composition

Lianas are an important growthform in tropical forests, and liana abundance and biomass may be increasing in some regions. Explanations for liana proliferation hinge upon physiological responses to changing resource conditions that would favour them over trees. Testing a chemical basis for such responses, we assessed 22 foliar traits in 778 lianas and 6496 trees at 48 tropical forest sites. Growthform differences in chemical allocation occurred on a leaf mass and area basis. Light capture-growth and maintenance-metabolism chemicals averaged 14.5 and 16.7% higher mass-based concentration in lianas than in trees globally, whereas structure and defence chemicals averaged 9.0% lower in lianas. Relative differences in chemical allocation by lianas and trees were mediated by climate with peak differences at about 2500 mm year(-1) and 25 °C. Differences in chemical traits suggest that liana expansion could be greatest in forests undergoing increased canopy-level irradiance via disturbance and climate change.     

Relative effects of different leaf attributes on sapling growth in tropical dry forest

Aims Soil moisture content (SMC) influences establishment, survival and development of plant species and is considered as the most important limiting factor in tropical dry forest (TDF). In this study we attempt to establish the relationship between leaf attributes and of tree saplings in TDF and address the following questions: (i) how are the functional attributes of dominant tree saplings of TDF affected by seasonal changes in SMC at different habitats?, (ii) what is the relationship of functional attributes with each other?, (iii) how are the functional attributes and their plasticity affected by habitat conditions? and (iv) can the functional attributes in single or in combination predict the growth rate of tree saplings of TDF? The study was conducted on four sites (Hathinala, Gaighat, Harnakachar and Ranitali, listed in order of decreasing SMC) within the tropical dry deciduous forest in northern India.Methods We analysed eight leaf attributes, specific leaf area (SLA); leaf dry matter content (LDMC); leaf nitrogen concentration (leaf N); leaf phosphorus concentration (leaf P); chlorophyll concentration (Chl); mass-based photosynthetic rate (A mass); mass-based stomatal conductance (Gs mass); intrinsic water use efficiency (WUEi) and three growth attributes, relative diameter increment (RDI); relative height increment (RHI); relative growth rate (RGR) of the 10 dominant tree saplings (viz., Acacia catechu, Anogeissus latifolia, Boswellia serrata, Buchanania lanzan, Diospyros melanoxylon, Hardwickia binata, Lagerstroemia parviflora, Lannea coromandelica, Shorea robusta and Terminalia tomentosa) of a TDF and observed the effects of site, season and species for a period of 2 years. Saplings were selected in gradients of deciduousness. Step-wise multiple regression was performed to predict RDI, RHI and RGR from mean values of SMC and leaf attributes.Important findings All the 11 attributes were interrelated and differed significantly among the 10 saplings. Species response varied across sites and seasons. Across the SMC gradient, the attributes showed variable plasticity that differed across species. Among the 10 saplings, the highly deciduous Boswellia serrata showed the maximum plasticity in seven functional attributes. According to the step-wise multiple regressions, 65% variability in RDI and 67% variability in RGR were due to Gs mass, and for RHI, 61% variability was due to A mass. SMC and the other attributes, viz ., SLA, Chl, WUEi and LDMC in combination could contribute only for ~2–6% of the variability in RDI, RHI and RGR, which indicates that other traits/factors, not accounted in this study are also important in modulating the growth of tree saplings in TDFs. In conclusion, growth of the tree saplings in the tropical dry environment is determined by soil moisture, whereas the response of saplings of different tree species is modulated by alterations in key functional attributes such as SLA, Chl, WUEi and LDMC.     

翅果油树及其群落中7种优势木本种类的叶性特征比较

Taking Elaeagnus mollis Diels and seven dominant woody species in its community from Yicheng County of Shanxi Province as research objects, leaf traits including specific leaf area (SLA), nitrogen content in leaf per unit area ( Narea ) , leaf dry matter content ( LDMC ) and photosynthetic nitrogen use efficiency ( PNUE ) were compared, and correlations of SLA value with LDMC and PNUE values were analyzed. The results show that there are different degree variations in four indexes of leaf traits of E. mollis, Vitex negundo var. heterophylla ( Franch.) Rehd., Broussonetia papyrifera ( Linn.) L' Hér. ex Vent., Lespedeza bicolor Turcz., Caragana microphylla Lam., Rosa xanthina Lindl., Amygdalus davidiana ( Carrière) de Vos ex Henry and Periploca sepium Bunge, in which, SLA value with the largest coefficient of variation ( 404%) , and LDMC value with the lowest coefficient of variation ( 103%) . Compared with other tested species, SLA and PNUE values of E. mollis are the lowest ( 103 cm-2 · g-1 and 108 μmol · mol-1 · s-1 , respectively) , while its Narea value is the highest ( 0243 g · m-2 ) , and its LDMC value is also relatively high ( 0380 g·g-1 ) . SLA value of eight tested species show an extremely significant positive correlation ( P<001) with PNUE value, and a significant negative correlation ( P<005 ) with LDMC value, correlation coefficient are 0923 and -0718, respectively, indicating that SLA value is an important parameter of leaf photosynthetic capacity and resource utilization ability. It is suggested that compared with other dominant woody species, E. mollis is more sensitive to environmental change, and has a poor environmental adaptability.     

Leaf physiology does not predict leaf habit; examples from tropical dry forest

Leaf structure and physiology are thought to be closely linked to leaf longevity and leaf habit. Here we compare the seasonal variation in leaf hydraulic conductance (k_leaf) and water potential of two evergreen tree species with contrasting leaf life spans, and two species with similar leaf longevity but contrasting leaf habit, one being deciduous and the other evergreen. One of the evergreen species, Simarouba glauca, produced relatively short-lived leaves that maintained high hydraulic conductance year round by periodic flushing. The other evergreen species, Quercus oleoides, produced longer-lived leaves with lower k_leaf and as a result minimum leaf water potential was much lower than in S. glauca (–2.8 MPa vs –1.6 MPa). Associated with exposure to lower water potentials, Q. oleoides leaves were harder, had a higher modulus of elasticity, and were less vulnerable to cavitation than S. glauca leaves. Both species operate at water potentials capable of inducing 20 (S. glauca) to 50% (Q. oleoides) loss of k_leaf during the dry season although no evidence of cumulative losses in k_leaf were observed in either species suggesting regular repair of embolisms. Leaf longevity in the deciduous species Rhedera trinervis is similar to that of S. glauca, although maximum k_leaf was lower. Furthermore, a decline in leaf water potential at the onset of the dry season led to cumulative losses in k_leaf in R. trinervis that culminated in leaf shedding.     

Phenology of tree species of tropical moist forest of Uttara Kannada district,Karnataka, India

Phenological observations on tree species in tropical moist forest of Uttara Kannada district (13ℴ55′ to 15ℴ31′ N lat; 74ℴ9′ to 75ℴ10′ E long) during the years 1983–1985 revealed that there exists a strong seasonality for leaf flush, leaf drop and reproduction. Young leaves were produced in the pre-monsoon dry period with a peak in February, followed by the expansion of leaves which was completed in March. Abscission of leaves occurred in the post-monsoon winter period with a peak in December. There were two peaks for flowering (December and March), while fruit ripening had a single peak in May–June, preceding the monsoon rainfall. The duration of maturation of leaves was the shortest, while that of full ripening of fruits was the longest. Mature flowers of evergreen species lasted longer than those of deciduous species; in contrast the phenophase of ripe fruits of deciduous species was longer than that of evergreen species.     

Leaf and shoot water content and leaf dry matter content of Mediterranean woody species with different post-fire regenerative strategies

BACKGROUND AND AIMS: Post-fire regeneration is a key process in Mediterranean shrubland dynamics, strongly determining the functional properties of the community. In this study, a test is carried out to determine whether there is co-variation between species regenerative types and functional attributes related to water use. METHODS: An analysis was made of the seasonal variations in leaf relative water content (RWC), leaf dry matter content (LDMC), leaf moisture (LM) and live fine fuel moisture (LFFM) in 30 woody species of a coastal shrubland, with different post-fire regenerative strategies (seeding, resprouting or both). KEY RESULTS: RWC results suggest that the studied resprouters have more efficient mechanisms to reduce water losses and maintain water supply between seasons. In contrast, seeders are more drought tolerant. LDMC is higher in resprouters over the course of the year, suggesting a more efficient conservation of nutrients. The weight of the phylogenetic constraint to understand differences between regenerative strategies tends to be important for LDMC, while it is not the case for variables such as RWC. CONCLUSIONS: Groups of species with different post-fire regenerative strategies (seeders and resprouters) have different functional traits related to water use. In addition to the role of phylogenetical constraints, these differences are also likely to be related to the respective life history characteristics. Therefore, the presence and abundance of species with different post-fire regenerative responses influence the functional properties of the communities.     

Performance of 11 tree species under different management treatments in restoration plantings in a tropical dry forest

Ecological restoration in tropical dry forests urgently needs to incorporate experimental evidence to increase effectiveness. The main barriers for tree establishment are adverse microenvironmental conditions and competition with exotic grasses. Therefore, management should address such barriers in order to enhance tree performance. We evaluated the effect of plastic mulching, grass removal, and no management on survival after 2 months and stem volume and canopy size after 2 years and integrated response index (IRI) in plantings of 11 native tree species with different growth rates in pastures near the tropical dry forest of Chamela, Mexico. Results revealed that: (1) initial seedling mortality was minimal in all treatments (8%) and lowest under no management (2%); (2) plastic mulching, but not grass removal, leads to increased size for most species, irrespective of their growth rank; (3) a trade‐off between initial plant survival and size after 2 years occurred due to plastic mulching; and (4) most species showed similar values of the IRI because of high survival, stem volume, or canopy cover. Grass removal decreased early survival of all species and increased stem volume only for one slow‐growing species. The use of plastic mulching increased stem volume for slow‐growing species, whereas fast‐growing species developed larger canopies with that treatment. Effects of grass removal and mulching seem to be very species‐specific and not dependent in growth rank of species, although overall mulching seems to provide better conditions for seedling performance than grass removal alone.     

Leaf flushing phenology and herbivory in a tropical dry deciduous forest,southern India

Patterns of leaf-flushing phenology of trees in relation to insect herbivore damage were studied at two sites in a seasonal tropical dry forest in Mudumalai, southern India, from April 1988 to August 1990. At both sites the trees began to flush leaves during the dry season, reaching a peak leaf-flushing phase before the onset of rains. Herbivorous insects emerged with the rains and attained a peak biomass during the wet months. Trees that flushed leaves later in the season suffered significantly higher damage by insects compared to those that flushed early or in synchrony during the peak flushing phase. Species whose leaves were endowed with physical defenses such as waxes suffered less damage than those not possessing such defenses. There was a positive association between the abundance of a species and leaf damage levels. These observations indicate that herbivory may have played a major role in moulding leaf flushing phenology in trees of the seasonal tropics.     

Dew and its effect on two heliophile understorey species of a tropical dry deciduous forest in Mexico

 A series of horizontal and vertical measurements of dew deposition and dew duration were carried out in a tropical dry deciduous forest in western Mexico (19° 30′ N, 105° 03′ W). The effect of dew on transpiration in heliophile species was also investigated. The amount of dew was very variable with no temporal or spatial pattern. The amount of dew measured at two horizontal transects (maximum and minimum) (at heights of 0.20 m and 1.30 m above ground level) was from 0.014 to 0.203 mm and from 0.013 to 0.061 mm in the middle and at the end of the dry season, respectively. Dew deposition at different vertical levels (0.50–12.5 m height) ranged from 0.04 to 0.36 mm. The duration of dew formation ranged between 60 and 129 min after sunrise above the canopy (a height of 11 m), and between 259 and 290 min after sunrise at a height of 2 m. Daily transpiration rates were 883 and 632 g m^–2 d^–1 in Coccoloba liebmannii and 538 and 864 g m^–2 d^–1 in Jacquinia pungens in January and April, respectively. Transpiration was restricted from sunrise to early afternoon in April, as a result of the pronounced midday closure of stomata in both species. The reduction of transpiration by dew ranged from 13.2 to 50.1 g m^–2 d^–1 and from 4.5 to 77.7 g m^–2 d^–1 for C. liebmannii and J. pungens, respectively. Dew can play an important role in enhancing the survival of heliophile species in the dry season by reducing transpiration rates during the morning. Received: 30 April 1998 / Accepted: 14 December 1998     

Functional diversity of macromycete communities along an environmental gradient in a Mexican seasonally dry tropical forest

Macromycetes are important for ecosystem functioning due to their role in the nutrient cycling, and their function as pathogens and mutualists. Diversity metrics based on functional traits are robust predictors of ecosystem functionality since they incorporate an evolutionary and ecologic background. We examined diversity patterns of macrofungi using functional trait-based metrics of diversity along an altitudinal gradient in a seasonally dry tropical forest in southern Mexico. Our findings show that: (1) functional diversity varies with elevation, relating more to climatic variables than to vegetation structure; (2) functional diversity indexes exhibited contrasting patterns, so measures reflecting heterogeneity on trait abundance and niche complementarity tend to increase with elevation, whereas the measure of trait evenness decreases; and (3) functional diversity patterns depend on the type of functional trait considered and how they respond to environmental conditions. Our results indicate that functional diversity analyses help understanding of how macrofungal communities respond to environmental variation.     

Callus and cell suspension cultures of Rudgea jasminoides,a tropical woody Rubiaceae

Rudgea jasminoides is a woody Rubiaceae that produces phytoalexins in response to fungal inoculation, the response being dependent of the seasonal conditions. With the aim of studying phytoalexin induction under controlled conditions, callus cultures were established from petiole explants of R. jasminoides on a modified basal MS medium supplemented with picloram alone or in combination with kinetin. The highest frequency of callus formation was observed in solid medium containing 2.22 M kinetin and 2.07 M picloram. Development of fast-growing friable white callus was achieved in the absence of kinetin, in cultures supplemented only with 8.28 M picloram. Cell suspension cultures were established from this friable callus by transferring pieces directly to the same medium without agar. Preliminary experiments revealed that cell suspension cultures of R. jasminoides represent a useful system to analyse induced defensive metabolites produced by this Rubiaceae species.     

热带雨林恢复演替中优势树种黄桐气体交换对环境的响应

用Li-6400便携式光合测定系统(Li-CorInc.,USA)对海南岛热带山地雨林恢复演替先锋建群种黄桐(EndospermumchinenseBenth.)叶片的气体交换特征及其对环境的响应进行了测定。结果表明:(1)净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(E)日变化均为双峰型曲线。出现"午睡"原因是光合有效辐射(PPFD)不足和Gs的关闭,不是强光抑制和水分胁迫。(2)叶片Pn大小与Gs、E、PPFD、气温(Ta)和叶面温度(Tl)等为密切的正比关系,与胞间CO2浓度(Ci)、大气CO2浓度(Ca)和大气相对湿度(RH)等相关度极低甚至是负相关,光饱和点(LSP)较高,表现出阳性树种特性。(3)短期高Ca作用会引起Gs、E的降低和Pn增高。Ca倍增,则Pn提高了70%,E降低4.43%,水分利用效率(WUE)提高78%。(4)叶片Pn日平均值和日最大值分别达6.40±0.17、11.60μmolCO2/(m2·s),表现出速生性。     

Liana community and functional trait analysis in tropical dry evergreen forest of India

Aim Lianas are abundant and diverse throughout the world and constitute an important structural and functional component of tropical forests. This study aims to investigate liana diversity, abundance and their functional traits in Indian tropical dry evergreen forest (TDEF).Methods A total of ten 1-ha plots, one each in 10 Indian TDEF sites were demarcated. Each 1-ha plot was divided into one-hundred 10- × 10-m quadrats to facilitate woody species inventory. All lianas ≥1cm diameter measured at 130cm from the rooting point and all trees ≥10-cm girth at breast height (gbh) were recorded from the study sites to analyze the patterns of liana diversity and abundance and also to compare the contribution of lianas to the total woody species richness, density and basal area. Liana variables across the study sites were compared using one-way analysis of variance. The qualitative functional traits of inventoried lianas and trees were assessed on the field and referring to pertinent field manuals.Important findings A total of 9237 liana individuals (ranged from 408–1658 individuals ha^-1) representing 52 species, 45 genera and 28 families were encountered from the 10 study sites. Liana species richness ranged from 11–31 species ha^-1 in 10 sites, which averaged 23.4 (±5.7) species ha^-1. The total basal area of lianas in the study sites was 7. 3 m 2 (0.20–1.76 m 2 ha^-1). There was a significant variation in liana species richness, density and basal area across the studied sites. On the whole, lianas contributed 52%, 49.3% and 4.1% to the total woody species (lianas and trees) richness, density and basal area, respectively. Liana trait analysis revealed the majority (50%) of lianas belonged to brevi-deciduous type. Stem twining was the chief climbing mechanism, exhibited by 21 species (52.6% of total abundance). More than half of the liana species (34 species; 6925 individuals) had microphyllous leaves. Fleshy-fruited lianas mostly bearing berries and drupes constituted the major fruit type in the studied sites. Zoochory was the predominant dispersal mode observed in 63.4% of species. Considering the ecological and functional role of lianas in Indian TDEF, the need for conservation is emphasized.     

吊罗山热带天然林物种多样性的海拔分布格局

海拔梯度是影响物种多样性格局的关键因素。为探究吊罗山热带天然林物种多样性的海拔分布格局，该研究对吊罗山245～1 130 m海拔内的6个热带天然林样地进行植被调查，从群落物种组成、物种多样性、区系组成和叶性质等方面分析沿海拔梯度吊罗山热带天然林物种多样性与群落特征变化规律。结果表明：(1)随海拔升高、温度降低、湿度升高、人为干扰减少，吊罗山热带天然林物种组成以及Margalef、Shannon-Wiener、Simpson、Pielou多样性指数均呈现先升高后降低的格局；中海拔群落水热条件最为适宜、人为干扰适中、α物种多样性最高。(2)随海拔升高，优势种重要值占比呈现先降低后升高的格局，且优势种具有明显的更替现象，中海拔群落呈现低地雨林与山地雨林的过渡性质。(3)群落间S?rensen群落相似度和海拔高度差呈显著负相关(P<0.05)。(4)区系组成以热带区分布为绝对优势，并以热带亚洲(印度-马来西亚)分布为主；热带区分布比例和海拔呈极显著负相关(P<0.01),温带区分布比例和海拔呈极显著正相关(P<0.01)。(5)叶性质呈现出以中型叶、单叶、革质叶、全缘叶为主的...     

Linking vein properties to leaf biomechanics across 58 woody species from a subtropical forest

• Leaf venations have elements with relatively lower elasticity than other leaf tissue components, which are thought to contribute to leaf biomechanics. A better mechanistic understanding of relationships between vein traits and leaf mechanical properties is essential for ecologically relevant interpretation of leaf structural variations.
• We investigated 13 major (first to third order) and minor (>third order) vein traits, six leaf mechanical properties and other structural traits across 58 woody species from a subtropical forest to elucidate how vein traits contribute to leaf biomechanics.
• Across species, vein dry mass density (ρ_v), total vein dry mass per leaf area (VMA) and minor vein diameter (VD_min), but not the lower‐order vein density (VLA_1?2), were positively correlated with leaf force to punch (F_p) and force to tear (F_t). Structural equation models showed that ρ_v and VD_min not only contribute to leaf mechanical properties directly (direct pathway), but also had impacts on leaf biomechanics by influencing leaf thickness and leaf dry mass per area (indirect pathway).
• Our study demonstrated that vein dry mass density and minor vein diameter are the key vein properties for leaf biomechanics. We also suggest that the mechanical characteristics of venations are potential factors influencing leaf mechanical resistance, structure and leaf economics spectrum.