Impacts of silvicultural thinning treatments on beetle trap captures and tree attacks during low bark beetle populations in ponderosa pine forests of northern Arizona

Our research used a combination of passive traps, funnel traps with lures, baited trees, and surveys of long-term thinning plots to assess the impacts of different levels of stand basal area (BA) on bark beetle tree attack and on trap captures of Ips spp., Dendroctonus spp., and their predators. The study occurred at two sites in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests, from 2004 to 2007 during low bark beetle populations. Residual stand BA ranged from 9.0 to 37.0 m2/ha. More predators and bark beetles were collected in passive traps in stands of lower BA than in stands of higher BA; however, significance varied by species and site, and total number of beetles collected was low. Height of the clear panel passive traps affected trap catches for some species at some sites and years. When pheromone lures were used with funnel traps [Ips pini (Say) lure: lanierone, +03/-97 ipsdienol], we found no significant difference in trap catches among basal area treatments for bark beetles and their predators. Similarly, when trees were baited (Dendroctonus brevicomis LeConte lure: myrcene, exo-brevicomin and frontalin), we found no significant difference for days to first bark beetle attack. Surveys of long-term thinning treatments found evidence of bark beetle attacks only in unthinned plots (approximately 37 m2/ha basal area). We discuss our results in terms of management implications for bark beetle trapping and control.     

Wood‐boring insect abundance in fire‐injured ponderosa pine

• 1 Wood‐boring larvae in the families Cerambycidae and Buprestidae are often found in high densities in burned trees after wildland fires. They play an important role in tree decomposition, often reducing the value of salvageable timber, and represent an important avian food source.
• 2 Three forest areas that experienced wildfires 1–3 years previously were surveyed during the summer of 2004. Ponderosa pine trees with green, scorched and consumed needles were examined for wood borer occurrence. Within each of the three needle damage categories, the mean wood borer incidence was similar between different age fires. Trees with scorched or consumed needles had significantly more wood borers than trees with green needles.
• 3 Larvae collected from under tree bark were identified to family; when possible, cerambycids were identified further to Acanthocinus spp., Monochamus sp., Rhagium inquisitor (L.) and Stictoleptura canadensis (LeConte), and buprestids were identified to Chalcophora spp. and Chrysobothris sp.
• 4 Classification tree models showed that the estimated probability of tree infestation by wood borers varied among needle damage categories. For trees with green needles, tree injury variables of high bole char height and phloem discolouration were important predictive variables. In trees where needles were consumed, tree size variables of diameter at breast height and tree height were important predictive variables.
• 5 More than half the dead trees examined were infested with wood borers, indicating that infestation of fire‐killed ponderosa pine may represent an important food source for species such as woodpeckers and a potential problem for the utilization of infested trees.

     

Vertical distribution and assemblages of corticolous myxomycetes on five tree species in the Great Smoky Mountains National Park

Corticolous myxomycetes of the Great Smoky Mountains National Park were studied in relation to their association with certain tree species and height of occurrence in the forest canopy. Using the double-rope climbing method, bark was collected at 3 m increments to the tops of trees of five different species. Bark samples from 25 trees were used to prepare 418 moist chamber cultures maintained and observed 4 wk. Eighty-four myxomycete species were identified, including 30 species not known to occur in the park. Tree species, pH, height in tree and water-holding capacity of the bark samples were analyzed to determine the relationships of myxomycete assemblages cultured on the bark. Results suggested that myxomycete community composition among selected tree species were similar, but occurrence and abundance of certain species were related to differences in bark pH. Community similarity values among trees of different species show that trees with the most similar myxomycete communities also have the most similar bark pH. Most myxomycete species in this study have a pH optimum. No variation in species richness was detected at different heights in the trees, and most species were obtained at all heights up to at least 24 m. The water-holding capacity of the bark could not be correlated with species richness or abundance of myxomycetes that inhabit the bark of living trees. This is the first study to characterize myxomycete communities of tree canopies.     

Pinewood Nematode,Bursaphelenchus xylophilus,Associated with Red Pine, Pinus resinosa,in Western Maryland

Red pines Pinus resinosa in Garrett and Allegany counties, Maryland, were examined during 1982-84 to determine distribution of the pinewood nematode, Bursaphelenchus xylophilus, within and among trees. Approximately 25-year-old (younger) and 47-year-old (older) trees were subdivided into the following categories: 1) trees with mostly green needles; 2) trees with mostly reddish-brown needles; 3) trees lacking needles but with bark intact; 4) trees lacking both needles and bark; and 5) trees with chlorotic, bleached-green needles. Bursaphelenchus xylophilus was found infecting 68% of younger red pines and 77% of older red pines. Nematodes were not evenly distributed in trees within any given tree decadence category or in trees of the same age. Nematodes were recovered from 20% of wood samples from trunks and primary and secondary branches in younger pines and from 15 % of older red pines. On the basis of tree decadence category, the highest incidence of infection in younger trees (31%) was in bleached-green needled trees (category 5), whereas in older trees the highest infection (25%) occurred in green needled trees (category 1). At both sites trunks were infected more often than branches.     

Post-fire regeneration strategies and tree bark resistance to heating in frequently burning tropical savanna woodlands and grasslands in Ethiopia

Regeneration mechanisms of vegetation and the role of tree bark resistance to frequent fire were studied in savanna woodlands and grasslands in Gambella, Western Ethiopia. Data were collected from four sites, each with three replicate plots. The variation between sites in species composition and biomass correlated with the differences in fire intensity. Foliar cover was recorded for individual plant species regenerating by sprouting from older parts of plants that had survived fire or by seedlings; records were made during the dry season and at the beginning of the wet season. Data on bark thickness and tree diameters of 12 dominant tree species were also recorded. Both facultative and obligate sprouters significantly contributed to post‐fire recovery, comprising 98.5 % of total vegetation cover. The contribution of seedlings to cover and abundance immediately following fire was negligible, but seedling density increased in the beginning of the rainy season, 4 to 5 months after fire. The importance of the sprouting and seeding strategies varied between the different plant growth forms. The highest contribution to cover and frequency was made by the most abundant grass species, which reproduced in both ways. Facultative sprouters made up 67.3 % of the vegetation cover, out of which 54 % consisted of grasses. Broad‐leaved herbs and trees/shrubs regenerating mainly by sprouting made up 31.3 % of the vegetation cover. Adaptations to fire in tree species seemed to include the development of a thick bark, once the tree has passed seedling stages. Tree bark thickness and tree diameter at breast height were strongly correlated with the time taken for cambium to reach an assumed lethal temperature of 60°C when exposed to fire, which indicated that mature trees with thick barks might resist stronger fire better than, e.g., small or young trees and trees with thin bark. However, for a given bark thickness the cambium resistance to heat varied three‐fold among species. Hence, site differences in fire intensity seemed to influence the distribution of trees depending on their bark characteristics and resistance to fire.     

元江干热河谷木质藤本的多样性及其与宿主树木的关系

木质藤本是森林生态系统的重要组分。本研究在元江干热河谷地区随机设置了30个20 m×20 m的样方,调查样方中胸径≥0.5 cm的木质藤本多样性及其与宿主树木之间的关系。结果显示:30个样方中记录到胸径≥0.5 cm的木质藤本植物共945株(隶属于22种20属11科),其中,豆科木质藤本的丰富度和多度最高;胸径≤2 cm的木质藤本占个体总数的63.7%;茎缠绕类木质藤本的个体数最多。样方中胸径≥5 cm的树木共有1060株(隶属于38种31属16科),36.0%的树木上至少附藤1株。不同径级和不同树皮粗糙度的树木被木质藤本侵扰的百分比之间存在极显著差异(P0.001)。随着宿主树木平均枝下高的增加,附藤率呈下降趋势。76.5%的木质藤本选择离其根生长点最近的树木进行攀援。表明元江干热河谷中的木质藤本以小径级占优势,树木胸径、枝下高、树皮粗糙度和木质藤本根生长点到树木的距离是影响木质藤本侵扰树木的重要因素,支持木质藤本对宿主树木的侵扰具有选择性的假说。研究结果对中国西南干热河谷退化植被的恢复与物种多样性保护具有重要意义。     

Leaf litter and the small-scale distribution of carabid beetles (Coleoptera, Carabidae) in the boreal forest

Management practices favoring conifers at the expense of deciduous tree species, and the eradication of deciduous trees, especially aspen Populus tremula , from managed forests have resulted in population declines in several species in Fennoscandia. In addition to species depending on decaying wood of deciduous trees, earlier evidence suggests that leaf litter, especially that of aspen, is favored by many carabid species. We ran a four-year experiment in order to compare carabid assemblages of unchanged forest floor with artificially created leaf-litter plots in central Finland. A total of 18 plots (5 m in diameter) were established in three forest stands without aspen a few kilometers apart. Each stand had 3 litter plots (litter added) and 3 control plots, Pre-treatment samples were compared with those collected alter litter addition.
The litter addition affected the carabid-assemblage structure by increasing the catches of some species and decreasing the catch of one species. The number of carabid species was similar in control and litter plots. The litter effect was smaller than variation among forest stands and year-lo-year fluctuations. There was a strong temporal constancy among the plots: 'rich' plots remained 'rich' from year to year and similarly, 'poor' plots remained 'poor'.
The significant influence of leaf litter on carabid abundance can be attributable to both abiotic factors (microenvironmental conditions, especially humidity and temperature), and biotic ones (changes in niche structure, improved food supply). Leal litter seems to have an effect on carabid distribution patterns, and deciduous trees scattered among conifers are likely to be of importance on carabid fauna in boreal forests.     

影响广东黑石顶树附生苔藓分布的环境因子

通过对广东省黑石顶自然保护区内5个2500 m2样地内树附生苔藓的调查及有关环境因子的测定,研究了树附生苔藓的分布格局及其与环境因子的关系.树附生苔藓在不同高度的分布存在一定梯度,20 cm高处树附生苔藓的种类数与盖度均大于60 cm及更高处,且其群落优势种的数量组成与后者存在较大差异.不同树种附生苔藓盖度和种数差异较大.基于附生苔藓植物的盖度进行DCA排序及聚类分析将树种分成四组,马尾松(Pinus massoniana)因具有两种特有的网藓(巴西网藓Syrrhopodon prolifer和鞘刺网藓S.armatus)单独一组,福建青冈(Quercus chungii)亦与其余各种的差异均较大,形成一组,其余阔叶树种根据其所处的森林类型分成两组,针阔叶混交林内的阔叶树种和次生阔叶林内的阔叶树种各形成一组.对环境因子及树皮含水量和pH的分析显示,垂直梯度上空气湿度的差异可能是造成附生苔藓在不同高度分布差异的主要影响因子之一,不同树种附生苔藓的差异在一定程度上受树皮pH的影响,而与树皮含水量无关.同一树种上树附生苔藓的分布又在一定程度上受森林类型的影响.     

Response of the foraging behaviour of red wood ants (Formica rufa group) to exclusion from trees

Abstract 1 Because of the large numbers within a colony and their aggressive nature, red wood ants (Formica rufa group) have a potential to greatly influence the cold‐temperate forest ecosystem. Wood ants are omnivorous and hunt in trees as well as on the forest floor. 2 A field experiment in a mixed forest in central Sweden was carried out to examine (i) the foraging behaviour of wood ants on the forest floor and (ii) the impact of increased numbers of wood ants on the soil fauna. The foraging behaviour of wood ants was manipulated by excluding the ants from their food resources in the tree canopy, with the intention to increase ant activity on the forest floor. To estimate this activity, the number of trees with foraging ants, the numbers of ants going to and from their nests and the prey carried by home‐running wood ants were determined during the summer period. Pitfall traps were placed in the soil to determine effects on mobile soil invertebrates. 3 When excluded from local trees, wood ants searched other trees further away from the nests rather than searching more intensively for prey on the forest floor. By contrast to the initial hypothesis, more soil‐living prey were caught by ants in the control plots than in the plots where the local trees were not accessible to the wood ants. The proportion of soil‐living to tree‐living prey tended to be greater in the control plots. 4 In the treated plots (no access to the trees), wood ants had a negative effect on the activity of Linyphiidae spiders. There was little effect of wood ants on other soil invertebrates. 5 This study suggests that the role of wood ants as top predators in the forest soil food‐web in central Sweden is limited.     

Effects of flooding on wood and bark anatomy of four species in a mangrove forest community

Variation in the wood and bark anatomy of the dominant species of a mangrove forest community in Mexico was evaluated in relation to some environmental factors, and their physiological adaptations to salinity and flooding period are discussed. The forest is characterized by three zones according to the presence of dominant tree species and flooding periodicity. Vessel arrangement and wood and bark ray height are strongly associated with flooding zones where trees are growing. Variance analyses revealed significant differences among zones for these anatomical characteristics. Soil texture and water salinity were the most useful parameters for the prediction of values of anatomical characteristics. More abundant vessels in radial multiples in a shorter flooding period suggest a functional advantage of multiple vessel groups. Taller wood and bark rays in response to prolonged flooding period can be attributed to anoxic conditions. Among zones, significant differences in the vulnerability index of the species were detected, but not with respect to relative conductivity. Significant differences among zones exist for wood and bark characteristics involved in vertical and horizontal water transport, photosynthates and gas exchange.     

Colonization of disturbed Scots pine trees by bark‐ and wood‐boring beetles

相似文献   

Ants,fire, and bark traits affect how African savanna trees recover following damage

Bark damage resulting from elephant feeding is common in African savanna trees with subsequent interactions with fire, insects, and other pathogens often resulting in tree mortality. Yet, surprisingly little is known about how savanna trees respond to bark damage. We addressed this by investigating how the inner bark of marula (Sclerocarya birrea), a widespread tree species favoured by elephants, recovers after bark damage. We used a long‐term fire experiment in the Kruger National Park to measure bark recovery with and without fire. At 24 months post‐damage, mean wound closure was 98, 92, and 72%, respectively, in annual and biennial burns and fire‐exclusion treatments. Fire exclusion resulted in higher rates of ant colonization of bark wounds, and such ant colonization resulted in significantly lower bark recovery. We also investigated how ten common savanna tree species respond to bark damage and tested for relationships between bark damage, bark recovery, and bark traits while accounting for phylogeny. We found phylogenetic signal in bark dry matter content, bark N and bark P, but not in bark thickness. Bark recovery and damage was highest in species which had thick moist inner bark and low wood densities (Anacardiaceae), intermediate in species which had moderate inner bark thickness and wood densities (Fabaceae) and lowest in species which had thin inner bark and high wood densities (Combretaceae). Elephants prefer species with thick, moist inner bark, traits that also appear to result in faster recovery rates.     

Sources of variation in the incidence of ant–aphid mutualism in boreal forests

• 1 The mutualism between wood ants of the Formica rufa group and aphids living in the canopy of trees is a widespread phenomenon in boreal forests, and it can affect tree growth. However, not all trees in the forest are involved in this interaction.
• 2 To assess the incidence of host trees involved in this ant–aphid mutualism and its spatial distribution in boreal forests, we inventoried sample plots with a radius of 10–15 m around wood ant mounds in 12 forest stands of two age classes (5–12‐year‐old sapling stands and 30–45‐year‐old pole stands) and two dominant tree species (Scots pine and silver birch) in Eastern Finland from 2007 to 2009.
• 3 The proportion of trees visited by ants out of all trees on the individual study plots were in the range 4–62%, and 1.5–39% of the trees on the plots were consistently visited by ants during all 3 years. The percentage of host trees increased with the ant mound base area on the plots. Trees visited by ants were larger and closer to the mound than trees not visited by ants. Within the group of visited trees, more ants were found on bigger trees and on trees close to the ant mounds.
• 4 Extrapolated from plot to stand level, we estimated that 0.5–6.6% of the trees were host trees in at least one of the three study years, and that only 0.01–2.3% of all the trees were consistently visited by ants during all 3 years. It is concluded that ant–aphid mutualism is a minor occurrence at the stand level.

     

The Influence of Location,Tree Age and Forest Habitat Type on Basic Fuel Properties of the Wood of the Silver Birch (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth.) in Poland

The most extensive study to be carried out in Poland, and one of only a few worldwide, regarding the influence of location, tree age and forest habitat type on the basic fuel properties of silver birch (Betula pendula Roth.) wood was conducted in 12 Forestry Districts of the Polish State Forests. The field study included trees in three age groups of approximately 30, 50 and 70 years. The research was carried out in a fresh broadleaved forest (FBF) habitat type, where in Poland silver birch stands predominate in respect of coverage area and merchantable volume. Additionally, for five selected Forestry Districts, a comparative study was conducted in a fresh mixed broadleaved forest (FMBF), the second most important habitat of this tree species. A total of 306 test trees were examined. For every sample, calorific value and contents of ash, carbon, hydrogen, nitrogen, sulphur and chlorine were determined. The results indicated a statistically significant influence of location on the calorific value (p?=?0.0001) and on the contents of ash (p?<?0.0001), carbon (p?<?0.0001), hydrogen (p?<?0.0001), nitrogen (p?<?0.0001) and chlorine (p?<?0.0001) in the analysed wood. Moreover, statistically significant differences were observed between values of ash content (p?=?0.046) and of calorific value (p?=?0.0026) depending on the forest habitat type. Tree age was found to have no significant influence on the calorific value of silver birch wood.     

Influence of bark pH on the occurrence and distribution of tree canopy myxomycete species

This study compares the occurrence and distribution of myxomycete species in the canopy of living trees and neighboring grapevines. Corticolous myxomycetes of three temperate forests in southeastern USA were studied on six tree species (30 trees) and grapevines (30 vines) to determine distribution and occurrence of myxomycete species relating to geographic location, host species, and bark pH. The double-rope climbing technique was used to access the canopy and sample bark up to 16.5 m. Bark samples were examined in 580 moist chamber cultures and 44 myxomycete species were identified representing 21 genera, averaging 3.0 +/- 2.1 species per sample site. Jaccard's coefficient determined community similarity between five individuals of six tree species, Acer saccharum, Fraxinus americana, Liquidambar styraciflua, Liriodendron tulipifera, Platanus occidentalis and Tsuga canadensis, and neighboring grapevines, Vitis aestivalis and V. vulpina. Vertical variation in species richness was significantly different only for Platanus occidentalis and might be attributable to flaking of bark with increasing height in the canopy. Tsuga canadensis and neighboring grapevines had greatest community similarity. Cribraria violacea was observed on all tree and grapevine species except T. canadensis and neighboring grapevines. Occurrence and species assemblages of myxomycetes were associated with bark pH, not geographic location. Bark of V. aestivalis (pH 4.5) was more acidic than neighboring T. canadensis (pH 4.1), compared to grapevines of the same species neighboring other tree species. Results indicated that most species are not regionally restricted, and although some myxomycetes are associated with a certain pH range, others develop on any substratum. Future research protocols for corticolous myxomycetes should emphasize sampling adequate amounts of substrata in a local region from different host species that have a wide range of bark pH, ensuring a representative sample of species for an entire region.     

Past attacks influence host selection by the solitary bark beetle Dendroctonus micans

1. A spatio‐temporal study of host selection and local spread of a solitary bark beetle attacking live spruce Dendroctonus micans (Kugelann) was carried out using a combination of standard statistical methods, geostatistical analyses, and modelling. The study was based on data from three plots (150–300 trees, 0.3–1 ha) from 1978 to 1993. All trees were mapped and successful and abortive bark‐beetle attacks on each tree were counted annually. Because the attacked trees usually survived, temporal attack patterns as well as spatial patterns could be analysed. 2. The distribution of successful insect attacks on the trees was slightly aggregative, indicating some degree of choice rather than totally random establishment. 3. The level of yearly individual attacks per tree was very stable, suggesting that D. micans usually leave the host in which they develop. 4. The attacked trees were distributed randomly in the plots; at the study's spatial scale, the insects dispersed freely throughout the plot (no spatial dependence). 5. On the other hand, time dependence was strong; some trees were attacked repeatedly while others were left untouched. 6. Among a choice of scenarios (random attack, fixed variability in individual host susceptibility, induced host susceptibility following random attack), the best fit was obtained with the model involving induced individual host susceptibility. This type of relation to the host tree contrasts strongly with patterns generally described in host–plant relationships (including gregarious, tree‐killing bark beetles), where local herbivore damage results in induced resistance. 7. These results suggest that the first attacks in a new stand are made at random, that all or most of the beetles emerging from a tree disperse and resample the stand, and that they settle preferentially on trees that were colonised successfully by previous generations.     

Are tree trunks habitats or highways? A comparison of oribatid mite assemblages from hoop-pine bark and litter

Abstract Oribatid mites (Acari: Oribatida) are among the most diverse and abundant inhabitants of forest soil and litter, but also have species-rich assemblages on bark and in the canopies of trees. It is unclear whether the trunk of a tree acts simply as a 'highway' for movement of mites into and out of the canopy, or whether the trunk has a distinctive acarofauna. We compare oribatid assemblages from the trunk bark of hoop pine ( Araucaria cunninghamii ) with those from litter collected beneath the same trees. A 1.0 by 0.5 m area of bark was sampled from three trees at each of five sites using a knockdown insecticide. A 1-L sample of leaf litter was collected as close as possible to the base of each sampled tree. Mites were extracted using Tullgren funnels, identified to genus and morphospecies, and counted. Assemblages were almost 100% distinct, with only one oribatid morphospecies ( Pseudotocepheus sp.) collected from both litter and bark. Litter had a higher taxon richness than bark in total and per sample, but oribatids made up a greater percentage of the acarofauna in the bark samples. We had expected that the more consistent physical substrate of bark would be reflected in greater similarity of oribatid faunas on trunks than in litter; however, the opposite proved to be the case. We conclude that hoop-pine trunks are habitats rather than highways for oribatid mites. Based on the observed higher turnover among bark faunas, tree trunks may represent habitat islands whose colonisation by particular oribatid species is more stochastic than that of the more continuous 'sea' of litter.     

城市行道树pH值和电导率与交通环境

对南方１８种觉的城市行道树的树皮ＰＨ值和电导率进行了测定。结果表明,不同的行道树的树皮ＰＨ值和电导率不同。对同一种种来说,靠近汽车道;的行道树的树皮的ＰＨ值泪地靠近人行道的一侧的树皮的ＰＨ值;而导电率表现为离汽车道越近或离工厂的污染源越近,树皮的电导率越高的规律。树皮ＰＨ值和导导率二者可以定性表示交通环境污染的程度。     

SURFACE AREA RELATIONS OF WOODY PLANTS AND FOREST COMMUNITIES

Surface area of wood and bark is an important dimension of forests, with implications for respiration rate, energy exchange, and water and mineral budgets. Surface area of stem wood and bark can be estimated effectively from linear regressions on conic surface (one-half basal circumference times tree height) or from regressions of the logarithm of area on the logarithm of diameter at breast height. Branch surface can be estimated from a formula using branch basal diameter, length, and number of current twigs, and from logarithmic regressions of branch bark surface on basal diameter of branches and breast-height diameter of trees. In temperate deciduous forests several square meters of plant surface occur above each square meter of ground surface; these plant surfaces include 0.3–0.6 m² of stem bark, 1.2–2.2 m² of branch bark, and 3.0–6.0 m² of leaf blades. Branch bark surface increases more rapidly than leaf surface with increasing size of branches and trees. Growth and aging of trees, and maturation of forests, imply increasing ratios of bark (and wood) surface to the photosynthetic leaf surface which supports its growth and respiration.     

Asynchronous recruitment history of Abies spectabilis along an altitudinal gradient in the Mt. Everest region

Aims Forest growth and recruitment and their relationships to climate are complex. The aims of our study are (i) to examine the patterns in tree radial growth and recruitment along an altitudinal gradient in Mt. Everest region and (ii) to identify the climatic factors that are responsible to the observed patterns in tree growth and recruitment.Methods Four plots, each 30 × 60 m in size, were established from the lower to upper limits of the eastern Himalayan fir forest in Dingjie County of the Mt. Everest Nature Reserve, China. Dendrochronological techniques were applied to obtain information about the radial growth and age of the trees in the plots. Correlation analysis was used to identify the relationships between radial growth and recruitment of trees and climatic variables, i.e. monthly mean temperature and Palmer Drought Severity Index (PDSI). The population age structure was analyzed to investigate the recruitment history.Important findings The timberline plot was characterized by significant tree recruitments in the recent three decades and sporadic recruitments in earlier periods. The other three plots showed recruitment pulses during 1880–1910 in Plot 3?700 m, during 1870–80 and 1920–30 in Plot 3?520 m and during 1900–40 in Plot 3?410 m. The recruitment of fir trees in the timberline was sensitive to summer (June–September) temperatures, but it was mainly controlled by episodic disturbances in lower altitudes. Fir radial growth in the upper two plots was positively correlated with previous winter and current August temperature. Fir radial growth at the two lower plots was positively correlated with PDSI from previous September to current September.