Montezuma pine nutrient status as affected by alder densities nitrogen fertilization

Literature reports both positive and negative effects of N‐fixing alders on conifer growth in alder‐conifer stands. Such divergent effects probably result from poorly understood species interactions. The aim of this work was to examine how varying alder‐to‐pine ratios (APRs) and N fertilization affect pine nutrient status. A pseudo‐experiment was installed in each of two areas of regeneration (AR) with different amounts of radiation reaching alder. The experimental approach consisted of a series of pseudoreplicated plots with five APRs within each AR. Half of each plot received 200 kg N ha^–1. Data were interpreted by vector analysis. Alders in the AR 1987 induced needle‐biomass reductions, K deficiency, and P accumulation in pine needles. However, nutrient availability increased with the proportion of alders in the AR 1989, where alders received high sunlight due to a less dense pine stand. Nitrogen fertilization increased needle biomass and N in three out of five alder proportions where alders were sunlight‐limited. In the other stand, with the exception of the no‐alder and A4 plots, positive effects of N fertilization increased with decreasing alder density. We conclude that sunlight‐limited alders may not positively affect associated‐species growth even in N‐limited sites.     

Waterlogging Affects Leaf and Tillering Dynamics in Wheat and Barley

The aim of this study was to analyse (i) the crop attributes that determine flowering time (i.e. final leaf number, FLN; and phyllochron, Phy), (ii) the dynamics of tiller appearance and (iii) the synchrony between leaf and tiller appearance in wheat and barley plants exposed to waterlogging. Two experiments were carried out in pots, in which wheat and barley cultivars were exposed to five waterlogging treatments, during different periods throughout the crop cycle, from emergence to maturity. The appearance of leaves and tillers on the main stem was measured twice a week in labelled plants. Waterlogging from emergence to flag leaf appearance significantly delayed time to flowering. The delay was greater when waterlogging occurred at the beginning of tillering, lengthening the period from emergence to flowering 24 % (13–15 days) in barley and 10–15 % (6–10 days) in wheat, as compared to control. Phy was the main attribute explaining the delay in flowering, as FLN was not altered. Waterlogging during the early stages of development reduced tiller appearance rate (TAR) in both species, but this effect was partially counterbalanced by a lengthening of the tillering phase, so the effect on final tiller number at maturity was limited. In conclusion, the exposure of wheat and barley to waterlogging during early stages of development delayed time to flowering and reduce TAR in both species. Waterlogging during more advanced crop stages produced slight effects on tillering dynamics, which would indicate that waterlogging affected structure generation more than mortality.     

Empirical evaluation of confidence and prediction intervals for spatial models of forest structure in Jalisco,Mexico

In recent years there has been an increasing interest in developing spatial statistical models for data sets that are seemingly spatially independent.This lack of spatial structure makes it difficult,if not impossible to use optimal predictors such as ordinary kriging for modeling the spatial variability in the data.In many instances,the data still contain a wealth of information that could be used to gain flexibility and precision in estimation.In this paper we propose using a combination of regression analysis to describe the large-scale spatial variability in a set of survey data and a tree-based stratification design to enhance the estimation process of the small-scale spatial variability.With this approach,sample units(i.e.,pixel of a satellite image) are classified with respect to predictions of error attributes into homogeneous classes,and the classes are then used as strata in the stratified analysis.Independent variables used as a basis of stratification included terrain data and satellite imagery.A decision rule was used to identify a tree size that minimized the error in estimating the variance of the mean response and prediction uncertainties at new spatial locations.This approach was applied to a set of n=937 forested plots from a state-wide inventory conducted in 2006 in the Mexican State of Jalisco.The final models accounted for 62% to 82% of the variability observed in canopy closure(%),basal area(m2·ha-1),cubic volumes(m3·ha-1) and biomass(t·ha-1) on the sample plots.The spatial models provided unbiased estimates and when averaged over all sample units in the population,estimates of forest structure were very close to those obtained using classical estimates based on the sampling strategy used in the state-wide inventory.The spatial models also provided unbiased estimates of model variances leading to confidence and prediction coverage rates close to the 0.95 nominal rate.     

墨西哥哈里斯科(Jalisco)林分结构小面积估测

对小的生态经济区开展自然资源统计是很困难的,政府决策人员只能依靠州水平的数据库来评价一定区域或局部的自然资源（森林、牧场、草地、农田等）状况。小面积评估技术可以用于评定这些资源。然而,哪一种小面积估测法可以给出最可靠、最准确的结果还不得而知。本研究检测了小面积评估分析常用的两种方法（即综合估计法和回归估计法）的可靠性、准确性。运用这两种方法分析墨西哥哈里斯科（Jalisco）州全州的自然资源数据,从而检测每种方法对所选择的森林林分结构特征预测结果的好坏。研究表明,回归方法在多个地理尺度上,对森林林分结构特征预测的可靠性和准确性均最好。因此,推荐州或地方资源管理者,在没有其他适当的辅助信息资料的情况下,可运用回归分析法来评估小区域内自然资源状况。图4表5参14。     

The elicitor protein BcIEB1 and the derived peptide ieb35 provide long-term plant protection

BcIEB is a small protein secreted by the phytopathogenic fungus Botrytis cinerea that is recognized as a pathogen-associated molecular pattern (PAMP) by plants. This activity is mapped to a highly conserved region of 35 amino acids, the peptide ieb35. Moreover, it has been shown that the protein and the peptide induce systemic resistance to B. cinerea after their infiltration into tobacco leaves. In this work, the possible use of BcIBE1 or ieb35 as plant protective agents has been tested. Tobacco plants were sprayed, infiltrated, or treated at the seedling stage with the protein or the peptide, and plant susceptibility to pathogens with different lifestyles was then studied at various times after treatment. The results showed that both BcIEB1 and ieb35 caused a similar reduction in the lesion sizes caused by B. cinerea and in colonization by Pseudomonas syringae pv. tabaci (reduced by c. 30% and c. 40%, respectively), independently of the treatment type. In addition, the number of B. cinerea inoculations leading to successful infections was also reduced in plants infiltrated or sprayed with BcIEB1/ieb35. The defence-related genes PR1a, NPR1, and osmotin ap24 were all induced by the protein and the peptide. BcIEB1, and especially ieb35, may be considered as a potential environmentally friendly treatment to increase plant resistance to pathogens.     

Influence of climatic conditions,topography and soil attributes on the spatial distribution of site productivity index of the species rich forests of Jalisco,Mexico

This paper presents an approach based on field data to model the spatial distribution of the site productivity index （SPI） of the diverse forest types in Jalisco, Mexico and the response in SPI to site and cli-matic conditions. A linear regression model was constructed to test the hypothesis that site and climate variables can be used to predict the SPI of the major forest types in Jalisco. SPI varied significantly with topog-raphy （elevation, aspect and slope）, soil attributes （pH, sand and silt）, climate （temperature and precipitation zones） and forest type. The most important variable in the model was forest type, which accounted for 35% of the variability in SPI. Temperature and precipitation accounted for 8 to 9% of the variability in SPI while the soil attributes accounted for less than 4% of the variability observed in SPI. No significant differences were detected between the observed and predicted SPI for the individual forest types. The linear regression model was used to develop maps of the spatial variability in predicted SPI for the individual forest types in the state. The spatial site productivity models developed in this study provides a basis for understanding the complex relationship that exists between forest productivity and site and climatic conditions in the state. Findings of this study will assist resource managers in making cost-effective decisions about the management of individual forest types in the state of Jalisco, Mexico.