常绿阔叶树种栲树幼苗对不同光环境的光合生理响应

常绿阔叶树种栲树是亚热带常绿闭叶林中的优势种之一.对比研究了林下、林窗和旷地3个光环境下栲树幼苗的光合特征参数、比叶质量、叶氮含量及叶解剖结构等,结果表明:林下栲树幼苗的光补偿点和暗呼吸速率低,比叶质量小,表观量子效率和光合氮素利用率高,利用弱光的能力强,在低光环境下保持了较高的光合能力;海绵组织发达且表皮细胞厚,是对凉爽环境的积极响应.在旷地,栲树的最大光合速率明显下降,暗呼吸速率显著升高,单位面积的叶氮含量较高但氮素利用率较低;叶厚度和栅栏组织厚度均增加,栅栏组织/海绵组织厚度比值也升高了,但栅栏组织不如海绵组织发达,不能适应高光环境.栲树幼苗在林窗有较高的光合能力,在林窗中能正常生长和更新.     

蜜环菌诱导子对丹参冠瘿组织积累丹参酮的影响

Using a computer software `uniform design, regression analysis and optimization system' (UROS), the effects of Armillaria mellea Karst elicitor, with respect to its concentration, time of supplement and harvest time, on the accumulation of tanshinones in the crown gall cultures of Salvia miltiorrhiza Bunge in 67-V liquid medium were studied. The result showed that the maximum tanshinone yield was 147 mg/L (P＜0.05）, 62 mg/L (P＜0.05）, 94 mg/L (P＜0.05） in the liquid medium and the cultures 29 day after addition of A. mellea (119 mL/L) at day 0, in the medium 26 day after the addition of 113 mL/L of A. mellea, 28 day after addition of 87 mL/L of A. mellea, respectively. The results confirmed that the computer software UROS was a good tool in the multi-factor study.     

油松种子园球果产量近期预测方法的研究

用可见半面树冠法和信息段法,对陇县八渡油松种子园球果近期产量进行了预测,建立了预测模型,并验证其预测结果精度高,可靠性强。其中信息段法更适合油松种子园球果产量近期预测预报。     

Automatic extraction and measurement of individual trees from mobile laser scanning point clouds of forests

Background and AimsIn addition to terrestrial laser scanning (TLS), mobile laser scanning (MLS) is increasingly arousing interest as a technique which provides valuable 3-D data for various applications in forest research. Using mobile platforms, the 3-D recording of large forest areas is carried out within a short space of time. Vegetation structure is described by millions of 3-D points which show an accuracy in the millimetre range and offer a powerful basis for automated vegetation modelling. The successful extraction of single trees from the point cloud is essential for further evaluations and modelling at the individual-tree level, such as volume determination, quantitative structure modelling or local neighbourhood analyses. However, high-precision automated tree segmentation is challenging, and has so far mostly been performed using elaborate interactive segmentation methods.MethodsHere, we present a novel segmentation algorithm to automatically segment trees in MLS point clouds, applying distance adaptivity as a function of trajectory. In addition, tree parameters are determined simultaneously. In our validation study, we used a total of 825 trees from ten sample plots to compare the data of trees segmented from MLS data with manual inventory parameters and parameters derived from semi-automatic TLS segmentation.Key ResultsThe tree detection rate reached 96 % on average for trees with distances up to 45 m from the trajectory. Trees were almost completely segmented up to a distance of about 30 m from the MLS trajectory. The accuracy of tree parameters was similar for MLS-segmented and TLS-segmented trees.ConclusionsBesides plot characteristics, the detection rate of trees in MLS data strongly depends on the distance to the travelled track. The algorithm presented here facilitates the acquisition of important tree parameters from MLS data, as an area-wide automated derivation can be accomplished in a very short time.     

Evaluation of automated pipelines for tree and plot metric estimation from TLS data in tropical forest areas

Background and AimsTerrestrial LiDAR scanning (TLS) data are of great interest in forest ecology and management because they provide detailed 3-D information on tree structure. Automated pipelines are increasingly used to process TLS data and extract various tree- and plot-level metrics. With these developments comes the risk of unknown reliability due to an absence of systematic output control. In the present study, we evaluated the estimation errors of various metrics, such as wood volume, at tree and plot levels for four automated pipelines.MethodsWe used TLS data collected from a 1-ha plot of tropical forest, from which 391 trees >10 cm in diameter were fully processed using human assistance to obtain control data for tree- and plot-level metrics.Key ResultsOur results showed that fully automated pipelines led to median relative errors in the quantitative structural model (QSM) volume ranging from 39 to 115 % at the tree level and 10 to 134 % at the 1-ha plot level. For tree-level metrics, the median error for the crown-projected area ranged from 46 to 59 % and that for the crown-hull volume varied from 72 to 88 %. This result suggests that the tree isolation step is the weak link in automated pipeline methods. We further analysed how human assistance with automated pipelines can help reduce the error in the final QSM volume. At the tree scale, we found that isolating trees using human assistance reduced the error in wood volume by a factor of 10. At the 1-ha plot scale, locating trees with human assistance reduced the error by a factor of 3.ConclusionsOur results suggest that in complex tropical forests, fully automated pipelines may provide relatively unreliable metrics at the tree and plot levels, but limited human assistance inputs can significantly reduce errors.     

长白山红松阔叶林林冠木竞争生长及林冠空隙动态研究

以长白山红松阔叶林林冠木的年龄资料为基础,分析林木冠重叠与年轮径向生长的关系;通过林冠空隙边缘人隙边缘株的干扰释压分析,揭示林冠空隙集中形成的动态规律。红松林相邻林木间理论树冠重叠率与年轮径向生长呈显著负相关,不同树种间存在不同的竞争和协同关系;红松林中除个别小空隙是经过一个集中形成期形成外,大部分空隙是经过２－３个集中形成期形成的,１９００－１９２０和１９１０－１９３０是大部分空隙的集中形成期。     

Sky exposure, crown architecture, and low-temperature photoinhibition in conifer seedlings at alpine treeline

In the alpine-treeline ecotone of the Snowy Range in Wyoming, USA, microsite sky exposure of Englemann spruce ( Picea englemannii ) and subalpine fir ( Abies lasiocarpa ) seedlings (< 5 years) was associated with the avoidance of low-nocturnal temperatures and high insolation, factors which appeared to result in low-temperature photoinhibition. In a field experiment, light-saturated photosynthesis ( A _sat) in current-year seedlings (newly germinated) of fir increased significantly (approximately seven-fold) in response to increased long-wave irradiance at night (warming), solar shading (approximately five-fold), and the combination of the two treatments (approximately eight-fold). A _sat in current-year spruce remained unchanged in response to all treatments, but was over four-times higher than fir in control plots. These results indicated substantial low-temperature photoinhibition, and were supported by similar A _sat trends in natural seedlings. Increased needle inclination and clustering in more exposed microsites for both species implicates the possible role of structural adaptations for decreased sky exposure and warmer leaf temperatures at night.     

Including tree spatial extension in the evaluation of neighborhood competition effects in Bornean rain forest

Classical tree neighborhood models use size variables acting at point distances. In a new approach here, trees were spatially extended as a function of their crown sizes, represented impressionistically as points within crown areas. Extension was accompanied by plasticity in the form of crown removal or relocation under the overlap of taller trees. Root systems were supposedly extended in a similar manner. For the 38 most abundant species in the focal size class (10–<100 cm stem girth) in two 4‐ha plots at Danum (Sabah), for periods P₁ (1986–1996) and P₂ (1996–2007), stem growth rate and tree survival were individually regressed against stem size, and neighborhood conspecific (CON) and heterospecific (HET) basal areas within incremented steps in radius. Model parameters were critically assessed, and statistical robustness in the modeling was set by randomization testing. Classical and extended models differed importantly in their outcomes. Crown extension weakened the relationship of CON effect on growth versus plot species’ abundance, showing that models without plasticity overestimated negative density dependence. A significant negative trend of difference in CON effects on growth (P₂−P₁) versus CON or HET effect on survival in P₁ was strongest with crown extension. Model outcomes did not then support an explanation of CON and HET effects being due to (asymmetric) competition for light alone. An alternative hypothesis is that changes in CON effects on small trees, largely incurred by a drought phase (relaxing light limitation) in P₂, and following the more shaded (suppressing) conditions in P₁, were likely due to species‐specific (symmetric) root competition and mycorrhizal processes. The very high variation in neighborhood composition and abundances led to a strong “neighborhood stochasticity” and hence to largely idiosyncratic species’ responses. A need to much better understand the roles of rooting structure and processes at the individual tree level was highlighted.     

The age of the crown group of passerine birds and its evolutionary significance – molecular calibrations versus the fossil record

Based on calibrations of molecular phylogenies and biogeographic considerations, it has been argued that the basal divergences of crown group Passeriformes occurred in the late Cretaceous, following the break-up of eastern Gondwana. Some implications of this hypothesis have, however, not yet been adequately addressed. In particular, a Cretaceous divergence of crown group passerines would imply an unprecedented evolutionary stasis for more than 80 million years in one of the most species-rich group of endothermic vertebrates. The temporal distribution and phylogenetic affinities of northern hemispheric fossils further conflicts with current hypotheses on the historical biogeography of passerines, and is in better concordance with a Cenozoic divergence of crown group Passeriformes.     

Expression of nopaline synthesis in tumorous and regenerant tobacco crown galls

Summary Tissues formed in liquid cultures of tobacco (Nicotiana tabacum cv. Wisconsin 38) crown galls incited byAgrobacterium tumefaciens C58 were of three types: unorganized callus, organized teratoma, and organized normal appearing. These tissues contained 400±12, 410±17, and 614±53 μg nopaline/g fresh weight, respectively. Using [¹⁴C]arginine, methods were developed for measuring in vivo nopaline biosynthetic rates. Tissues were incubated in a low concentration (i.e., 3 μM) of [¹⁴C]arginine to minimize disruption of the internal pool (approximately 140 μM free arginine). Radioactivity in the tissue was assayed and the specific radioactivity of free arginine, the precursor of nopaline, was determined. The linear rate of incorporation of radioactivity into nopaline was used to calculate the following biosynthetic rates (expressed as microgram nopaline per gram fresh weight per 24 h): callus, 14; teratoma, 21; normal appearing, 24. These results show conclusively that normal appearing tissues obtained from crown gall tumors can synthesize nopaline. Abnormal growth and opine biosynthesis, therfore, can be expressed independently.