华北石质山区核桃-绿豆复合系统氘同位素变化及其水分利用

通过对比核桃枝条和绿豆茎内δD值差异来分析核桃和绿豆水分来源和利用。结果表明,核桃-绿豆农林复合系统的根系在表层土壤(0—30cm)中交叉存在,生态位重叠。旱季中表层土壤含水量与δD值之间存在显著的负相关关系(R2=0.77,P=0.02),雨季相关关系不显著(R2=0.03,P=0.73)。δD值分析表明,旱季中核桃利用深层土壤(30—80cm)水分占总水分来源的51%以上,雨季中则主要利用浅层土壤水分,间作绿豆和单作绿豆主要利用表层土壤水分。雨季中表层土壤水分能同时满足核桃和绿豆生长需要,但复合系统中光能竞争导致间作绿豆光合速率显著地低于单作绿豆。旱季间作绿豆0—20cm土壤水分含量、凌晨叶片水势和光合速率明显高于单作绿豆,显示间作绿豆体内水分状况好于单作绿豆。线性模型分析结果显示间作绿豆体内约有1.58%—5.39%的水分来核桃夜晚水力提升,表明复合系统在旱季一定程度上缓冲季节性水分胁迫对农作物生长的影响。     

Observations and modeling of aboveground tree carbon stocks and fluxes following a bark beetle outbreak in the western United States

Bark beetle epidemics result in tree mortality across millions of hectares in North America. However, few studies have quantified impacts on carbon (C) cycling. In this study, we quantified the immediate response and subsequent trajectories of stand‐level aboveground tree C stocks and fluxes using field measurements and modeling for a location in central Idaho, USA that experienced an outbreak of mountain pine beetle (Dendroctonus ponderosae Hopkins). We measured tree characteristics in lodgepole pine (Pinus contorta) plots spanning a range of structure and mortality conditions. We then initialized the forest vegetation simulator, an individual tree‐based model, with these measurements and simulated the response of aboveground production of C fluxes as well as trajectories of C stocks and fluxes in the coming decades. Mountain pine beetles killed up to 52% of the trees within plots, with more larger trees killed. C stocks in lodgepole pine were reduced by 31–83% following the outbreak, and plot‐level C fluxes decreased 28–73%. Modeled C stocks increased nearly continuously following the infestation, recovering to preoutbreak levels in 25 years or less. Simulated aboveground tree C fluxes increased following the immediate postoutbreak decrease, then subsequently declined. Substantial variability of C stocks and fluxes among plots resulted from the number and size of killed and surviving trees. Our study illustrates that bark beetle epidemics alter forest C cycling unlike stand‐replacement wildfires or clear‐cut harvests, due in part to incomplete mortality coupled with the preference by beetles for larger trees. The dependency of postoutbreak C stocks and fluxes on stand structure suggests that C budget models and studies in areas experiencing mountain pine beetle disturbances need to include size distribution of trees for the most accurate results.     

武夷山常绿阔叶林乔木与灌木小枝树皮主要功能性状的趋同

树皮是维管形成层以外的所有组织,其功能性状是反映植物生态适应策略的重要研究对象。为了揭示亚热带山地乔、灌木小枝树皮功能性状特征及其关联性,采用独立样本T检验和标准主轴回归方法对武夷山19种常见木本植物小枝树皮的主要功能性状的基本特征及其相关性进行了分析。结果发现：(1)树皮厚度、树皮密度与树皮含水量在乔、灌木之间无显著差异,其均值分别为(0.78±0.06)mm、(0.58±0.03)mg/cm³和(155.07±14.16)%。树皮碳(C)、氮(N)、磷(P)生态化学计量特征在乔、灌木之间差异也不显著,C、N、P平均值分别为(492.43±4.25)mg/g、(8.90±0.74)mg/g和(0.61±0.06)mg/g,树皮C∶N、C∶P与N∶P平均值分别为60.76±4.17、905.53±67.36与15.19±0.84。(2)树皮性状之间存在关联,其中树皮厚度与密度、密度与含水量均呈异速生长关系,而树皮厚度与含水量、氮含量与磷含量均呈等速生长关系。乔木树皮碳含量和磷含量间、灌木树皮密度和氮含量间均呈异速生长关系,乔木与灌木各性状间关系差异不显著。结果表明...     

The different responses of Batocera horsfieldi adults to Juglans regia bark and leaf volatile compounds

Batocera horsfieldi (Hope) (Coleoptera: Cerambycidae) is an important pole borer pest. It causes serious harm to various hosts, particularly Juglans regia L. (Juglandaceae). In this study, headspace solid-phase microextraction (HS-SPME), gas chromatography–mass spectrometry (GC–MS), and electroantennogram (EAG) responses were combined to examine the mechanism by which B. horsfieldi adults locate their host, J. regia. The results showed that J. regia contained 65 volatile compounds in all, with 36 and 42 volatile substances in bark and leaves, respectively. Moreover, terpenes accounted for the largest relative content among the volatile compounds of bark and leaves, 43.4 and 78.9%, respectively. Ten of 19 selected volatile components elicited significant EAG responses in adult B. horsfieldi, which indicated that the pest may prefer certain volatile compounds when selecting a host. Sex and volatile concentration affected the responses of B. horsfieldi. Male adults had the strongest EAG responses to 1-octen-3-ol, whereas female adults had the strongest EAG responses to linalool. Host selection in B. horsfieldi was somewhat positively associated with the concentrations of the effective volatile compounds in the host. Furthermore, B. horsfieldi showed varying preferences for isomers. This work provided data support for the development of insect attractants, and laid a theoretical foundation for the ecological protection of local forestry.     

Anthropogenic fire and bark thickness in coastal and island pine populations from Alta and Baja California

Aim  Native American fire use influenced bark thickness of coastal and island Monterey pine ( Pinus radiata D. Don) and bishop pine ( Pinus muricata D. Don) populations.
Methods  Basal bark thickness and d.b.h. were measured in two common-garden pine plantations that included all five native Monterey pine populations and nine of 10 native bishop pine populations. One-factor analysis of covariance was used to determine if significant differences in bark thickness existed between island and coastal populations.
Results  Bark thickness was measured on 228 Monterey and 42 bishop pines. Bark thickness in coastal and island Monterey pine populations was significantly different. Bark thickness in coastal and island bishop pine populations was not significantly different.
Main conclusions  Basal bark was thick in populations where there was a history of Native American burning. Basal bark was thin in two island populations where Native Americans have been absent or distant from the pine populations. While other influences no doubt affect the evolution of lower-bole bark thickness, it appears that frequent anthropogenic fires may be a powerful selection force.     

Putrescine metabolism in excised cotyledons of Pinus radiata cultured in vitro

The metabolism of ¹⁴C-putrescine and the changes in the endogenous concentrations of putrescine, spermidine and spermine were studied when cotyledons of Pinus radiata D. Don were cultured under shoot-forming (SF, + N⁶-benzyladenine) and non-shoot-forming (NSF, - N⁶-benzyladenine) conditions. Differences in the total uptake of ¹⁴C-putrescine during a 2 h pulse feeding were not significant between the SF and NSF cotyledons except on day 3. The maximum uptake of label was on day 3 in the SF cotyledons, which released the highest amount of ¹⁴CO₂ as well. ¹⁴C from the labeled putrescine was incorporated mainly into γ-aminobutyric acid, aspartate and glutamate. High performance liquid chromatography of the endogenous polyamines indicated that spermidine was the most predominant polyamine in the cultured cotyledons of radiata pine. Spermine increased by about 60% in the SF and 25% in the NSF cotyledons between days 0 and 3 of culture.     

RATP: a model for simulating the spatial distribution of radiation absorption, transpiration and photosynthesis within canopies: application to an isolated tree crown

The model RATP (radiation absorption, transpiration and photosynthesis) is presented. The model was designed to simulate the spatial distribution of radiation and leaf-gas exchanges within vegetation canopies as a function of canopy structure, canopy microclimate within the canopy and physical and physiological leaf properties. The model uses a three-dimensional (3D) representation of the canopy (i.e. an array of 3D cells, each characterized by a leaf area density). Radiation transfer is computed by a turbid medium analogy, transpiration by the leaf energy budget approach, and photosynthesis by the Farquhar model, each applied for sunlit and shaded leaves at the individual 3D cell-scale. The model typically operates at a 20–30 min time step. The RATP model was applied to an isolated, 20-year-old walnut tree grown in the field. The spatial distribution of wind speed, stomatal response to environmental variables, and light acclimation of leaf photosynthetic properties were taken into account. Model outputs were compared with data acquired in the field. The model was shown to simulate satisfactorily the intracrown distribution of radiation regime, transpiration and photosynthetic rates, at shoot or branch scales.     

Nitrogen allocation and carbon isotope fractionation in relation to intercepted radiation and position in a young Pinus radiata D. Don tree

The three dimensional distribution of intercepted radiation, intercellular CO₂ concentration (C_i) and late summer needle nitrogen (N) concentration were determined at the tips of all 54 branches in a 6·2-m-tall Pinus radiata D. Don tree growing in a New Zealand plantation. Measurements included above- and below-canopy irradiance, leaf stable carbon isotopic composition (δ¹³C) and tree canopy architecture. The radiation absorption component of the model, MAESTRO, was tested on site and then used to determine the branch tip distribution of intercepted radiation. We hypothesized that in branch tip needles: (i) the allocation of nitrogen and other nutrients would be closely associated with the distribution of intercepted radiation, reflecting carbon gain optimization theory, and (ii) C_i would predominantly reflect changes in photosynthetic rate (A) rather than stomatal conductance (g_s), indicating that the increase in A for a given increase in N concentration was larger than the corresponding increase in g_s. Needle nitrogen concentration was poorly related to intercepted radiation, regardless of the period over which the latter was calculated. At a given height, there was a large azimuthal variation in intercepted radiation but N concentration was remarkably uniform around the tree canopy. There was, however, a linear and positive correspondence between N concentration and δ¹³C and needle height above ground (r² = 0·73 and 0·68, respectively). The very strong linear correspondence between N concentration and C_i (r² = 0·71) was interpreted, using gas exchange measurements, as supporting our second hypothesis. Recognizing the strong apical control in P. radiata and possible effects of leaf nitrogen storage in an evergreen species, we propose that the tree leader must have constituted a very strong carbon sink throughout the growing season, and that the proximity of branch tip needles to the leader affected their photosynthetic capacity and nutrient concentration, independent of intercepted radiation. This implies an integrated internal determination of resource allocation within the tree and challenges the current convention that resources are optimally distributed according to the profile of intercepted radiation.     

凹叶厚朴粗壮枝和细弱枝的树皮和韧皮部结构的比较研究

凹叶厚朴的树皮由外向内为周皮、皮层、初生韧皮部的纤维束和次生韧皮部.筛管分子具有复筛板或单筛板、P-蛋白质,筛板孔开放,可见联络索,无淀粉粒.伴胞为与筛管分子等长的一列或单个细胞.粗壮枝周皮的木栓层约6层细胞组成,皮层中油细胞、淀粉粒、石细胞较多.细弱枝周皮的木栓层约3层细胞组成,皮层中油细胞、淀粉粒、石细胞较少.粗壮枝和细弱枝筛管分子宽度相当,但前者筛管分子较长,筛管蛋白质较多,后者筛管分子较短,筛管蛋白质较少.     

磷元素和土壤酸化交互作用对核桃幼苗光合特性的影响

核桃(Juglans regia)向南推广种植不可避免地会遇到土壤酸化和缺磷的环境, 这种环境如何影响核桃的生长是生产中需要知晓的基础问题。该文研究了土壤不同pH值对核桃的磷素营养影响以及缺磷对核桃幼苗水分平衡、光合特性和生长的影响。在温室内采用砂培盆栽试验, 研究一年生核桃嫁接幼苗在不同pH值、磷水平基质中的水分关系、光合特性和生长的应对机制。研究设4种处理, 即: 对照(正常供应磷素+ pH 6.0); 正常供应磷素+ pH 3.0; 不添加磷素+ pH 6.0; 不添加磷素+ pH 3.0。结果显示: pH值与磷素对核桃幼苗的影响是两个相互独立的过程, 酸性(pH值3.0)条件下, 核桃幼苗根系生物量降低、根冠比减小, 根系导水率降低, 对磷素的吸收利用减少, 尽管其供磷正常, 但各生长指标及生理指标与磷胁迫条件下反应相似; 两因素具有一定的叠加性, 在磷胁迫条件下, 酸化(pH值3.0)对核桃幼苗的损害进一步加剧。各指标具体变化如下: 酸化及磷胁迫条件下核桃根系水分导度降低, 叶柄木质部结构改变, 导管密度降低, 木质部导管栓塞程度增加, 叶柄导水率下降, 植株水分运输效率降低, 叶片水势降低, 诱导气孔关闭; 气孔导度降低, 光合作用能力下降; 胁迫条件下, 叶绿素荧光参数最大光化学效率低于0.8, 实际光化学效率、光化学淬灭下降, 非光化学淬灭增加, 核桃幼苗受胁迫环境损害, 叶片光系统II光合电子传递活性受到抑制, 光合能力下降。总之, 土壤酸化抑制了核桃幼苗对磷元素的吸收利用, 造成体内缺磷; 磷胁迫及酸化抑制了叶柄木质部的发育, 降低了根系水分导度和叶柄导水率, 干扰了核桃幼苗水分平衡, 通过气孔与非气孔共同调节, 限制了核桃幼苗光合作用, 抑制了核桃幼苗高生长、直径生长及叶面积增加; 但并没有发现土壤酸化和缺磷之间有明显的交互作用。     

An empirical method that separates irreversible stem radial growth from bark water content changes in trees: theory and case studies

Substantial uncertainty surrounds our knowledge of tree stem growth, with some of the most basic questions, such as when stem radial growth occurs through the daily cycle, still unanswered. We employed high‐resolution point dendrometers, sap flow sensors, and developed theory and statistical approaches, to devise a novel method separating irreversible radial growth from elastic tension‐driven and elastic osmotically driven changes in bark water content. We tested this method using data from five case study species. Experimental manipulations, namely a field irrigation experiment on Scots pine and a stem girdling experiment on red forest gum trees, were used to validate the theory. Time courses of stem radial growth following irrigation and stem girdling were consistent with a‐priori predictions. Patterns of stem radial growth varied across case studies, with growth occurring during the day and/or night, consistent with the available literature. Importantly, our approach provides a valuable alternative to existing methods, as it can be approximated by a simple empirical interpolation routine that derives irreversible radial growth using standard regression techniques. Our novel method provides an improved understanding of the relative source–sink carbon dynamics of tree stems at a sub‐daily time scale.     

Fire‐induced tree mortality in a neotropical forest: the roles of bark traits,tree size,wood density and fire behavior

Large‐scale wildfires are expected to accelerate forest dieback in Amazônia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire‐induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large‐scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cambium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire‐induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return interval was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low (≤20%) for thick‐barked individuals (≥18 mm) subjected to medium‐intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire‐induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests.     

Synergistic effects of α-pinene and exo-brevicomin on pine bark beetles and associated insects in Arizona

The southern pine beetle (Dendroctonus frontalis) and western pine beetle (Dendroctonus brevicomis) cause significant mortality to pines in the southern and western United States. The effectiveness of commercial lures at capturing these bark beetles in Arizona has not been tested and may vary from other regions of their distribution. We conducted experiments using baited Lindgren funnel traps to investigate (i) if D. frontalis is more attracted to the standard commercial lure for D. brevicomis (frontalin + exo‐brevicomin + myrcene) than the D. frontalis lure (frontalin + terpene blend), (ii) whether replacement of myrcene with α‐pinene changes trap catches of Dendroctonus and associated insects, and (iii) whether the attraction to these lures varies across the geographical range of ponderosa pine forests throughout Arizona. In 2005, we tested various combinations of frontalin, exo‐brevicomin, myrcene and α‐pinene to D. frontalis, D. brevicomis and associated species. Dendroctonus frontalis, D. brevicomis and the predator Temnochila chlorodia were most attracted to lures with exo‐brevicomin. The replacement of the myrcene component with α‐pinene in the D. brevicomis lure resulted in the capture of twice as many bark beetles and Elacatis beetles. However, T. chlorodia did not differentiate between monoterpenes. In 2006, traps were set up in 11 locations around Arizona to test the relative attraction of lure combinations. In 9 out 11 locations, the D. brevicomis lure with α‐pinene was more attractive than the lure with myrcene or a terpene blend. These results suggest that the D. brevicomis lure with α‐pinene rather than myrcene is more effective lure to capture D. brevicomis and D. frontalis in Arizona. However, geographical variation in attractiveness to lures is evident even within this region of the beetles’ distributions. Differential attraction of Dendroctonus and their predators to these lures suggests potential use in field trapping and control programmes.     

Response of transpiration and photosynthesis to a transient change in illuminated foliage area for a Pinus radiata D. Don tree

Sudden but transient changes in the fraction or illuminated foliage area in a well-watered 7-year-old Pinus radiata D. Don tree were imposed by completely covering either the upper 22% or the lower 78% of the foliage for periods of up to 36 h. Measurements of transpiration flux density (E), tree conductance (g_t), stomatal conductance (g_s) and net photosynthesis (A) were made to test the hypothesis that compensatory responses would occur in the remaining illuminated foliage when the cover was installed. When the lower foliage was covered there was an immediate decrease in g_t. However, when tree conductance was normalized with respect to the illuminated leaf area (g_t'), it increased between 50 and 75%, depending on the value of air saturation deficit (D). The effect was also apparent from concurrent measurements of increases in g_s and A up to 59 and 24%, respectively, for needles in the top third of (he crown. When the cover was removed these effects were reversed. The changes in the lower foliage when the upper foliage was covered were much smaller. Changes in bulk needle water potential were small. It is suggested that the observed responses occurred because of a perturbation to the hydraulic pathway in the xylem that could have triggered the action of a chemical signal to regulate stomatal conductance and photosynthesis.     

Pinus radiata invasion in Australia: Identifying key knowledge gaps and research directions

Abstract Early recognition of plant invaders has been widely identified as the key to their successful management and yet too often species are only noticed and receive adequate attention once they have become widespread and control has become difficult and costly. Slow growing species are at particular risk of being overlooked, despite their ability to cause significant ecological damage. One such species, Pinus radiata (Monterey pine), has spread from large commercial plantations into native vegetation across the southern hemisphere. Here we review the status of P. radiata invasion in Australia, a country where the species has successfully naturalized but remains an invader of only low‐level concern. Patterns of spread in Australia mirror those in New Zealand and South Africa, two countries where invasive pines are considered major threats to biodiversity. While many areas adjacent to plantations remain free from invasion, dense infestations have occurred at several sites in areas of high conservation value demanding the implementation of adequate control measures. Expansion of Australia's plantation estate and increasing human disturbance of natural areas surrounding plantations will increase the likelihood and extent of invasion. Continued monitoring of wildling populations will determine the ability of pines to dominate native eucalypt forest and will provide insight into broader ideas of community invasibility.     

Indole-3-acetic acid level in wood,bark and cambial sap of apple rootstocks differing in growth vigour

Free and conjugated IAA levels were determined in wood, bark and cambial sap of M.9, M.26 and MM.106 apple rootstock genotypes differing in growth vigour. The measurements were done on May 15^th, June 15^th and July 15^th. The level of free IAA in bark and wood of the tested trees varied from 27.0 to 52.7 ng·g⁻¹ f.w. while the conjugated hormone content averaged 3–5 times higher. In the bark and wood samples, the differences in auxin content between rootstock genotypes and the time of stem harvesting were insignificant. The level of free IAA in cambial sap was on average 10 to 20 times higher than in both bark and wood tissues, while the conjugated hormone level varied from none (below detection limit) to 37 ng·g⁻¹ f.w. Content of free IAA level in cambial sap from dwarf M.9 rootstock was significantly lower than that in either of the more vigorous genotypes. In both vigorous rootstocks IAA level in cambial sap remained at a similar level at all sampling dates but M.9 cambial sap showed a trend towards decreasing auxin content later in the growing season.     

Effects of green tree retention and prescribed burning on the crown damage caused by the pine shoot beetles (Tomicus spp.) in pine-dominated timber harvest areas

Abstract: We explored how two recently introduced methods to promote biodiversity during the timber harvest in boreal forests – green tree retention and use of fire – may affect damages caused by pine shoot beetles (Tomicus piniperda and Tomicus minor; Col., Scolytinae) in the surrounding pine forests. The experimental design included 24 separate study sites, 3–5 ha each, which were assigned to different treatments according to factorial design. Retention levels included 0, 10, 50 m³/ha and uncut controls. Twelve of the sites were burned and thus there were three replicates of each treatment combination. Old and new fallen pine shoots were counted from transects in adjacent pine‐dominated forests 2 and 3 years after the treatments. Populations of Tomicus spp. in the sites were monitored using window traps before and after the treatments, and by examining felled sample trees. Numbers of fallen shoots returned to background levels around unburned and burned clearcuts with no retention trees in 3 years after the treatments, but remained still at increased level in burned harvested sites with 10 and 50 m³ of retained trees per hectare. Numbers of fallen shoots in burned uncut forests increased in one site only, where the fire was intense enough to kill large pine trees, but the damage did not extend outside the burned area. Shoot numbers remained at such low levels (<18 000 shoots/ha) in all treatment combinations that growth losses were not likely. Numbers of egg galleries of Tomicus spp. in trees killed by fire were low, indicating that burnings that take place after the swarming of Tomicus beetles create dead wood that is not optimal for the breeding of these pests. We conclude that green tree retention and prescribed use of fire do not automatically affect populations of Tomicus spp. more than traditional forestry operations (thinnings and clearcuttings) do.