Opposing mechanisms affect taxonomic convergence between tree assemblages during tropical forest succession

Whether successional forests converge towards an equilibrium in species composition remains an elusive question, hampered by high idiosyncrasy in successional dynamics. Based on long‐term tree monitoring in second‐growth (SG) and old‐growth (OG) forests in Costa Rica, we show that patterns of convergence between pairs of forest stands depend upon the relative abundance of species exhibiting distinct responses to the successional gradient. For instance, forest generalists contributed to convergence between SG and OG forests, whereas rare species and old‐growth specialists were a source of divergence. Overall, opposing trends in taxonomic similarity among different subsets of species nullified each other, producing a net outcome of stasis over time. Our results offer an explanation for the limited convergence observed between pairwise communities and suggest that rare species and old‐growth specialists may be prone to dispersal limitation, while the dynamics of generalists and second‐growth specialists are more predictable, enhancing resilience in tropical secondary forests.     

Correlations of understory herb distribution patterns with microhabitats under different tree species in a mixed mesophytic forest

Summary This study examines the role of canopy trees in the formation and maintenance of different herb microhabitats in a mixed mesophytic forest stand. Herb abundance and reproductive success were recorded in 54 circular plots under seven species of canopy trees and in 15 circular control plots>2 m from any tree. Soil moisture, soil nutrient levels, litter depth, and light intensity were measured in a subset of these plots. Ordination of plots by both herb relative abundance and by reproductive success of common species indicated that herb assemblages under most canopy tree species were similar to those away from trees. However, herb assemblages under Fagus grandifolia trees differed moderately from the others while plots under Quercus alba trees supported significantly different herb assemblages. Analyses of variance revealed that several herb species occurred at significantly closer mean distance to the base of Q. alba or Fagus trees or at higher densities under these tree species. Soils around Q. alba trees had significantly higher concentrations of calcium and sulfate ions, and higher pH than plots under other tree species and control plots. This correlated closely with Q. alba stemflow which had higher concentrations of calcium and sulfate ions and lower concentrations of hydrogen ions than stemflow from other trees at this site. The slightly lower soil pH near the base of Fagus trees may have been related to the high volumes of stemflow produced by this species. Stepwise regression showed significant correlations between abundances of five common herb species and soil nutrient patterns. Maintenance of spatial heterogeneity in forest floor resources by the presence of different species of canopy trees may therefore be important in the maintenance of diversity in these understory herb 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.     

Gap regeneration of major tree species in different forest types of Japan

Gap regeneration of major tree species was examined, based on the pattern of gap phase replacement, in primary old-growth stands of warm-temperate, cool-temperate and subalpine forests, Japan. Using principal component analysis, the gap-regeneration behavior of major tree species could be divided into three guilds and that of Fagus crenata (monodominant species of cool-temperate forests). The criteria used for this division were total abundance of canopy trees and regenerations and relative abundance of regenerations to canopy trees. The gap-regeneration behavior of species in the first guild was that canopy trees regenerate in gaps from seedlings or saplings recruited before gap formation; they had higher total abundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of F. crenata was same as species in the first guild, but F. crenata had less abundant regenerations relative to its canopy trees. Species in the second guild had lower total abundance and less abundant regenerations to their canopy trees. The guild contained species whose canopy trees regenerate in gaps from seedlings or saplings recruited after gap formation or regenerate following largescale disturbance. The third guild consisted of species with lower total aboundance and more abundant regenerations relative to their canopy trees. The gap-regeneration behavior of some species in this guild was that trees regenerate in gaps from seedlings or saplings recruited before gap formation, and grow, mature, and die without reaching the canopy layer, while the gap-regeneration behavior of other species was same as that of species in the first guild or F. crenata. Major tree species of subalpine forests were not present in the third guild.     

不同干扰强度下针阔混交林树种空间格局及种间关联性

为了探究不同干扰程度下针阔混交林树种空间格局变化及树种种间关联性,本研究以关帝山庞泉沟自然保护区不同干扰强度的针阔混交林为对象,选取郁闭度、林分密度、伐桩数量作为划分干扰程度的因子,采用相对影响法,将林分划分为未干扰、中度干扰和严重干扰3个等级.利用空间点格局K2函数分析了林分的空间分布格局及其不同树种的种间关联.结果...     

Pathogenesis-related genes and proteins in forest tree species

Trees occupy more than 30% of the land biosphere. They are important from both ecological and environmental standpoints and provide some of the most valuable commodities in the world economy. The perennial nature and size of trees are the critical determinants of their survival in response to biotic and abiotic stresses. The identification of the defense pathways at biochemical and genetic levels in tree pathosystems are beginning to be addressed. The basic physiological and biochemical mechanisms in woody perennials in response to pathogen is homologous to the model annual crop like Arabidopsis, but their secondary metabolic processes and ecological survival strategies are likely to be divergent from their annual counterparts. The limited domestication in tree species makes its molecular mechanisms less comparable to the highly pedigreed crop species. Recent reports have highlighted that the possible difference in genetic programs responding to invasive pathogens between annuals and perennials could be the spatial and temporal pattern of gene regulation. Several reviews on pathogen defense with reference to crop species are available, while similar reports from the tree species are limited to few commercially important species like Populus, Pinus, Picea, Eucalyptus, Castanea, and Pseudotsuga. This paper reviews the present status of pathogenesis-related genes and proteins from tree species with emphasis on the resistant genes and the proteins induced during systemic acquired resistance and highlights the ecological and evolutionary significance of defense-related genes from tree species.     

不同光强下生长的亚热带树苗的光合-光响应特性的比较

鼎湖山亚热带森林中的优势树种马尾松、荷木、黧蒴和黄果厚壳桂的幼苗,盆栽于100%、40%和16%的自然光下生长1年.利用氧电极离体测定叶片的光合-光响应曲线,结果表明不同树种及同一树种不同生长光强处理之间差异明显.比较最大净光合速率(Amax)、光补偿点、光饱和点、光抑制点及光能利用效率(QUE)等的变化可见,黄果厚壳桂为耐阴植物,对高光强的光合适应潜力为有限,100%的自然光明显抑制其最大同化力;其余3种植物均为喜光植物,其中马尾松的光合作用对遮阴的适应能力较差,而荷木和黧蒴则相对较强.本文还对植物的光合生理特性与其演替状态的联系作了初步探讨.     

Drought acclimation of two deciduous tree species of different layers in a temperate forest canopy

Water-use strategies of Populus tremula and Tilia cordata, and the role of abscisic acid in these strategies, were analysed. P. tremula dominated in the overstorey and T. cordata in the lower layer of the tree canopy of the temperate deciduous forest canopy. Shoot water potential (), bulk-leaf abscisic acid concentration ([ABA]_leaf), abscisic acid concentration in xylem sap ([ABA]_xyl), and rate of stomatal closure following the supply of exogenous ABA (v) decreased acropetally through the whole tree canopy, and foliar water content per area (w), concentration of the leaf osmoticum (c), maximum leaf-specific hydraulic conductance of shoot (L), stomatal conductance (g_s), and the threshold dose per leaf area of the exogenous ABA (d_a) required to reduce stomatal conductance increased acropetally through the tree canopy (from the base of the foliage of T. cordata to the top of the foliage of P. tremula) in non-stressed trees. The threshold dose per leaf dry mass of the exogenous ABA (d_w) required to reduce stomatal conductance, was similar through the tree canopy. After a drought period (3 weeks), the , w, L, g_s, d_a and d_w had decreased, and c and v had increased in both species. Yet, the effect of the drought period was more pronounced on L, g_s, d_a, d_w and v in T. cordata, and on , w and c in P. tremula. It was concluded that the water use of the species of the lower canopy layer—T. cordata, is more conservative than that of the species of the overstorey, P. tremula. [ABA]_leaf had not been significantly changed in these trees, and [ABA]_xyl had increased during the drought period only in P. tremula. The relations between [ABA]_leaf, [ABA]_xyl and the stomatal conductance, the osmotic adjustment and the shoot hydraulic conductance are also discussed.     

Performance of some forest tree species in saline soils under shallow and saline water-table conditions

Summary Field studies were carried out to study the influence of seasonal variations in salinity and soil moisture profiles due to fluctuating water table on the performance of 16 tree species. Over a yearly cycle water table having an EC of 2–46 mmhos/cm fluctuated between 10–140 cm from the surface. Seasonal variation in salinity profiles indicated that subsurface planting (30 cm below surface) provides less hostile saline environment to the roots. Due to genetic differences, species of trees differed in their ability to withstand salinity and aeration stresses individually and simultaneously. In areas where salinity is not associated with high water table conditions, tree species likeAcacia auriculiformis, Terminalia arjuna andLeucaena leucocephala can be grown. Tree species likeCasuarina equisetifolia Tamarix articulata andProsopis juliflora can be planted where high salinity or high water table conditions exist separately or simultaneously. If planting occurs on ridges,Acacia auriculiformis, Acacia nilotica andTerminalia arjuna can also be grown in these conditions.     

Contrasting mechanisms of secondary metabolite accumulation during leaf development in two tropical tree species with different leaf expansion strategies

Young leaves of most species experience remarkably higher herbivore attack rates than mature leaves. Considerable theoretical effort has focused on predicting optimal defense and tradeoffs in defense allocation during leaf expansion. Among others, allocation to secondary chemistry may be dependent on growth constraints. We studied flavanoid production during leaf development in two species of Inga (Fabaceae: Mimosoideae) with different expansion strategies: Inga goldmanii, a species with slowly expanding young leaves, and Inga umbellifera, a species with fast-expanding young leaves. In these two species, the most abundant and toxic class of defensive compounds is flavanoids (which include tannins). We measured their concentration by leaf dry weight, their total content per leaf, their HPLC chemical profile and their toxicity to a generalist herbivore at different expansion levels. Although in both species the flavanoid concentration decreased with increasing leaf expansion, that decrease was twice as pronounced for I. umbellifera as it was for I. goldmanii. I. umbellifera leaves produced flavanoids only during the first half of their development while I. goldmanii leaves continued production throughout. The changes in flavanoid HPLC profiles and toxicity were also more dramatic for I. umbellifera, which had different flavanoids in young than in mature leaves. Relative to I. umbellifera, I. goldmanii showed smaller changes in both flavanoid composition and toxicity in the transition from young to mature leaves. These results indicate that, even though young leaves suffer higher rates of attack and are predicted to have better chemical defenses than mature leaves, growth constraints may modulate defense allocation and thus, evolution of defense strategies.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Physiology-based phenology models for forest tree species in Germany

Models of phenology are needed for the projection of effects of a changing climate on, for example, forest production, species competition, vegetation-atmosphere feedback and public health. A new phenology model for deciduous tree bud burst is developed and parameters are determined for a wide geographical range (Germany) and several forest tree species. The new model is based on considerations of simple interactions between inhibitory and promotory agents that are assumed to control the developmental status of a plant. Several alternative model structures were formulated emphasizing different hypothetical physiological processes. The new models fitted the observations better than classical models. The bias of the classical models, i.e. overestimation of early observations and underestimation of late observations, could be reduced but not completely removed. Differences in the best-fitting model equations for each species indicated that, for the late spring phases (bud burst of Fagus sylvatica and Quercus robur), the photoperiod played a more dominant role than for early spring phases (bud burst of Betula pendula and Aesculus hippocastanum). Chilling only plays a subordinate role for spring bud burst compared to temperatures preceding this event in our data. The presented modeling approach allowed for a species-specific weighting of the dominant processes. The model results are in accordance with experimental findings that indicate an important role of day length in late spring BB. Potentials for model improvement are discussed.     

Regional variation in Caribbean dry forest tree species composition

How does tree species composition vary in relation to geographical and environmental gradients in a globally rare tropical/subtropical broadleaf dry forest community in the Caribbean? We analyzed data from 153 Forest Inventory and Analysis (FIA) plots from Puerto Rico and the U.S. Virgin Islands (USVI), along with 42 plots that we sampled in the Bahamian Archipelago (on Abaco and Eleuthera Islands). FIA data were collected using published protocols. In the Bahamian Archipelago, we recorded terrain and landscape variables, and identified to species and measured the diameter of all stems ≥5 cm at 1.3 m height in 10 m radius plots. All data were analyzed using clustering, ordination, and indicator species analysis at regional and local scales. Regionally, the largest cluster group included over half of all plots and comprised plots from all three island groups. Indicator species were native Bursera simaruba (Burseraceae) and Metopium toxiferum (Anacardiaceae). Species composition was similar to dry forests throughout the region based on published studies. Other groups we identified at the regional scale consisted of many Puerto Rico and USVI plots that were dominated by non-native species, documenting the widespread nature of novel ecosystems. At the local scale the Bahamian data clustered into two main groups corresponding largely to the two islands sampled, a pattern consistent with the latitudinal aridity gradient. Bahamian dry forests share previously undocumented compositional similarity with native-dominated dry forests found throughout the Caribbean, but they lack extensive post-disturbance novel dry forests dominated by non-native trees found in the Greater Antilles.     

Climatic relationships of some New Zealand forest tree species

Abstract. A dataset of some 10 000 plots was used to describe the climatic relationships of 33 widespread New Zealand tree species. Estimates of mean annual temperature, temperature seasonality, mean annual solar radiation, and moisture balance were derived from mathematical surfaces fitted to climate station data. Plots were also categorized into five lithological classes and three drainage classes. Generalized additive models were used to examine species/environment relationships. Mean annual temperature and mean annual solar radiation are most strongly correlated with current tree distributions, followed by moisture balance, temperature seasonality, lithology, and drainage. Most broad-leaved tree species other than Nothofagus spp. reach their greatest levels of occurrence in warm, moist environments with high solar radiation. In contrast, Nothofagus spp. generally reach their greatest levels of occurrence in cooler and/or lower insolation environments, and all have lower levels of occurrence on rhyolitic substrates which have resulted from large-scale geomorphic disturbance, mostly over the past few thousand years. Although coniferous species have widely differing climatic optima, many are biased towards lithological classes characterized either by large-scale geomorphic disturbance or harsh edaphic conditions. The relevance of these results to particular synecological questions is briefly discussed. Continuing adjustments in the range of slow-dispersing Nothofagus spp. are strongly suggested, and the climatic suitability of extensive rhyolitic basins in the central North Island, from which these species are largely absent, is confirmed.     

不同光强下生长的亚热带树苗的光合—光响应特性的比较

鼎湖山亚湖热带森林中的优势树种马尾松、荷木、黛蒴和黄果厚壳桂的幼苗,盆栽于１００％、４０％和１６％的自然光下生长１年。利用氧电极离体测定叶片的光合－光响应曲线,结果表明不同树种及同一种树种不同生长光强处理之间差异明显。比较最大净光合速率、光寂偿点、光饱和点、光抑制点及光能利用效率等的变化可见,黄果厚壳桂为耐阴植物,对高光强的光合适应潜力为有限,１００％,自然光明显抑制最大同化力;其余３种植物均为喜     

亚热带不同树种凋落叶分解对氮添加的响应

为探究不同质量凋落物对氮(N)沉降的响应, 该研究采用尼龙网袋分解法, 在亚热带福建三明格氏栲(Castanopsis kawakamii)自然保护区的米槠(Castanopsis carlesii)天然林, 选取4种本区常见的具有不同初始化学性质的树种凋落叶进行模拟N沉降(N添加)分解实验(施N水平为对照0和50 kg·hm ^-2·a ^-1)。研究结果表明: 在2年的分解期内, 对照处理的各树种凋落叶的分解速率依次为观光木(Michelia odora, 0.557 a ^-1)、米槠(0.440 a ^-1)、台湾相思(Acacia confusa, 0.357 a ^-1)、杉木(Cunninghamia lanceolata, 0.354 a ^-1); N添加处理凋落叶分解速率依次为观光木(0.447 a ^-1)、米槠(0.354 a ^-1)、杉木(0.291 a ^-1)、台湾相思(0.230 a ^-1), 除杉木凋落叶外, N添加显著降低了其他3种凋落叶分解速率。N添加不仅使4种树木凋落叶分解过程中的N释放减慢, 同时还抑制凋落叶化学组成中木质素和纤维素的降解; N添加在凋落叶分解过程中总体上提高β-葡萄糖苷酶(βG)和酸性磷酸酶活性, 对纤维素水解酶的活性影响不一致, 而降低β-N-乙酰氨基葡萄糖苷酶活性和酚氧化酶活性。凋落叶分解速率与凋落叶中的碳获取酶(βG)活性以及其化学组分中的可萃取物含量极显著正相关, 与初始碳浓度、纤维素和木质素含量极显著负相关, 与初始N含量没有显著相关性。凋落物类型和N添加的交互作用虽未影响干质量损失速率, 但对木质素和纤维素的降解具有显著效应。综上所述, 化学组分比初始N含量能更好地预测凋落叶分解速率, 而N添加主要通过抑制分解木质素的氧化酶(如PHO)来降低凋落叶分解速率。     

Patterns of daily stem growth in different tree species in a warm-temperate forest in northern China

Radial growth in trees responds to environmental changes in various ways ranging from immediate to hysteretic responses. However, species-specific tree radial growth patterns and their responses to short-term weather changes are not fully understood. Here, the daily stem radial changes (SRCs) in four common tree species, linden (Tilia mongolica), birch (Betula dahurica), oak (Quercus wutaishanica) and larch (Larix principis-rupprechtii), were monitored with high-resolution point dendrometers during the main growing seasons in 2017–2019 on Dongling Mountain, northern China. The SRC was differentiated into tree water deficit-induced stem shrinkage (TWD) and growth-induced irreversible stem expansion (GRO) to evaluate species-specific responses to weather variables and short-term drought events. We found that the TWD and GRO of the four species were significantly different. The TWD was influenced primarily by the vapor pressure deficit (VPD), whereas the GRO was influenced primarily by precipitation (P). In linden and birch, a larger proportion of the GRO occurred at higher air temperature (T_mean) and VPD values; in contrast, the range of these changes was lower in oak and larch. With the increased durations of drought periods, oak and larch experienced large and rapid increases in TWD, whereas birch and linden showed small and slow increases. These results indicate that oak and larch would be sensitive to warmer and drier weather conditions predicted for the future, while linden and birch would have a conservative growth strategy. Our results provide further insights into the physiology of these four tree species and allow us to better predict the growth response of forest dynamics under climate change.     

Pattern of tree species diversity in riparian forest fragments of different widths (SE Brazil)

Width is an essential element of the spatial configuration of riparian forests and may be fundamental in determining their corridor function. In the present study we tested the effect of forest width on floristic structure (tree species composition and diversity) in 15 fragments of riparian forest in an agricultural fragmented landscape of SE Brazil. All these fragments were chosen in a geomorphological homogeneous river reach under similar soil, topographic and human disturbance conditions in order to minimize the influence of these factors. The forest widths considered ranged from 30 to 650 m. The results showed that total species richness and climax species richness were significantly greater when we consider larger fragments, as has been observed in other studies. Nevertheless, species diversity and evenness were not significantly correlated with forest width. The analysis of species composition showed that the narrowest fragments were characterized by species well adapted to temporary flood conditions, while medium and wide fragments showed a composition typical of drier upland areas. Therefore, the effect of forest width on floristic structure appears to be more strongly linked to the effect of river floods in the case of the fragments studied. The existence in riparian corridors of a drier forest, in general richer and more diversified than the annually flooded forest, seems to favor the maintenance of regional species diversity in fragmented landscapes.