Cut Trees Research Articles

Elongate hemlock scale, an exotic scale insect pest of Christmas trees and other conifers

Elongate hemlock scale, Fiorinia externa Ferris (Hemiptera: Diaspididae), is an armored scale insect native to Japan and eastern Asia. This insect was first documented in the United States in 1908 in Queens, NY, and has since spread throughout most of the eastern United States. Though the primary hosts of the pest, hemlocks and firs, do not occur in Florida, there are concerns that elongate hemlock scale coming into the region on cut Christmas trees may disperse and establish on conifers that do occur in Florida. Of specific interest are two endangered species, Florida torreya (Torreya taxiflora) and Florida yew (Taxus floridana), which are native to a small region in northwestern Florida. Also of concern are Florida forestry species, Florida Christmas tree species, and species used for ornamental plantings in Florida. What can Florida do to protect its native conifers and farmed trees from the elongate hemlock scale? Find out in this 5-page fact sheet written by Adam Dale, Travis Birdsell, and Jill Sidebottom and published by the UF/IFAS Entomology and Nematology Department. http://edis.ifas.ufl.edu/in1253

Factors Determining Soil Water Repellency in Two Coniferous Plantations on a Hillslope

Soil water repellency (SWR) is a cause of low water infiltration, overland flow and soil erosion in mountainous coniferous plantations in Japan. The factors determining SWR intensity were investigated in two coniferous plantations of Chamaecyparis obtusa (Siebold et Zucc.) Endl. and Cryptomeria japonica (L.f.) D. Don, using intact tree plots and cut tree plots on the same hillslope. The SWR of Ch. obtusa plots was stronger than that of Cr. japonica plots. SWR intensity decreased after tree cutting. There were no significant differences in SWR upslope and downslope of individual trees/stumps for both tree species, though areas downslope of individual Ch. obtusa trees had higher SWR intensity than those upslope. SWR intensity and soil aggregate stability were positively correlated in the Ch. obtusa intact tree plot (r = 0.88, p < 0.01), whereas in the cut tree plot, this correlation was weak with no significance (r = 0.29, p = 0.41). Soil aggregate size had a non-significant influence on SWR intensity. These findings suggest that SWR intensity was not related to the soil aggregate size, but SWR intensity seemed have a role in soil aggregation in the Ch. obtusa intact tree plot. Destruction of soil aggregates could occur after tree cutting because of physical disturbances or increased input of different types of organic matter from other vegetation into soil. The presence of Ch. obtusa introduces a source of SWR, although uncertainty remains about how water repellency is distributed around soil aggregates. The distribution pattern of soil water content and soil hydraulic conductivity around Cr. japonica was related to other factors such as the litter layer and non-water-repellant soil.

Cost Analysis of Innovative Biomass Harvesting Systems for Young Dense Thinnings

The objective was to analyze three innovative harvesting systems for early thinnings and compare forest-to-industry supply costs. FlowConv consists of a harvester equipped with an innovative continuously cutting, accumulating and bunching head (the FlowCut head), a forwarder and a truck to transport loose tree-parts. FlowFix consists of a harvester equipped with the same cutting head but also a bundling unit (the Fixteri system), plus a forwarder and roundwood truck for biomass transport. FlowCin consists of a new conceptual biomass harvester (the Cintoc system) equipped with the same cutting head and a second crane to pass the cut trees from the front of the machine to a bundling unit at the back, plus the same forwarding and trucking units as in the FlowFix system. Empirical data were used to assess the FlowConv system’s performance, while the FlowFix and FlowCin systems’ performance was simulated. Results indicate that supply costs of the FlowCin system would be 6–10% and 24–29% lower than those of the FlowFix and FlowConv systems, respectively. Thus, it would be more suitable to be equipped with an innovative cutting head, which is up to 100% more efficient than the current commercially available options. Key features of the Cintoc-based system (which minimize possible waiting times during operation) include its buffering cradle and delivery of biomass acquired in two cutting crane cycles to the intermediate delivering crane. The apparent superiority of the FlowCin system is consistent with previous conclusions regarding developments needed to maximize the cost-effectiveness of harvesting young dense stands.

Direct measurements of tree root relative permittivity for the aid of GPR forward models and site surveys

ABSTRACTGround penetrating radar has been used extensively in near‐surface studies to detect underground objects and features typically located within a few metres beneath the surface. In urban areas, ground penetrating radar is widely used to study buried utilities such as pipes and cables. A more recent and unconventional application of ground penetrating radar is the detection of tree roots, which can interact negatively with the human infrastructure in a number of ways. However, the geophysical study of tree roots has proven quite challenging and site‐specific. Most tree roots (even coarse roots) have a small diameter and are hard to resolve through geophysical methods. In addition, the sheer amount of potential variability regarding the tree species, age, size, health and the subsurface environment (e.g., soil or a man‐made material such as concrete or asphalt) makes it very hard to implement a one‐size‐fits‐all approach. This is where robust, easily customizable forward models can be of assistance, indicating the range of detectable geophysical contrast and the limitations of the method, as well as the suitable antenna frequencies. Here, a vector network analyser with a commercial open‐ended coaxial probe was used to take direct measurements of the relative permittivity of freshly cut tree root segments at frequencies from 50 MHz to 3 GHz. The results were used as inputs to ground penetrating radar forward modelling using gprMax open source software, depicting various realistic scenarios which could be encountered in actual field surveys. The developed models help better understand the applicability, potential and limitations of ground penetrating radar surveys for detecting tree roots in different environments, aiding the development of future surveys. The notable variability in the tree roots is a significant consideration for surveys and forward models.

Use of n-alkanes to trace erosion and main sources of sediments in a watershed in southern Brazil

Erosive processes can transport sediments containing nutrients, heavy metals and contaminants of organic and inorganic origin into bodies of water, therefore affecting the local ecosystem and the population that benefits from the water sources. In order to better understand the origin of sediment sources and establish mitigation measures, the use of the sediment fingerprinting technique has been highlighted. Thus, the present work had as objective to apply n-alkanes in order to trace and understand the main sources of organic matter in sediments and associate the results with land and soil occupation. The study area is located in the municipality of Rio Negrinho - Brazil, in the Saci river basin. Soil samples were collected and classified according to their use and occupation, as well as and samples of local vegetation to be used as reference. The distribution of n-alkanes in the sediments was compared with the distribution found in the vegetation and soil. Previously, a distribution pattern of n-alkanes had been identified in all major vegetation used to trace the source of organic matter and hence the soil. The concentrations of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and granulometry were also analyzed in the soil and sediment samples. Indexes between n-alkanes were used and applied to assess the source together with statistical analysis (PCA). In sum, the results showed that the sediments are mainly composed of Pinus taeda reforestation soils, as well as soil from the abandoned roads used to transport the cut trees, while the contribution of autochthonous sediments was found to be minimal. In this way, the fingerprint technique served as an auxiliary tool in order to establish measures for the good management of a river basin, bringing important information about the contributing sources of sediment to water bodies.

Effects of disturbance and site factors on sapling dynamics and species diversity in northern hardwood stands

The northern hardwoods forest ecosystem of eastern North America provides a wealth of products and services to human society. These forests have been managed under partial harvesting treatments to meet wood production objectives of desired species while maintaining or increasing structural and compositional heterogeneity. Few studies have examined how disturbance and site factors interactions may influence sapling dynamics and species diversity in northern hardwood forests. We used a retrospective approach to examine the impacts of disturbance and site factors on sapling (trees > 130 cm in height and <10.0 cm dbh) dynamics and species diversity across 37 stands with time since harvest ranging from 6 to 20 years. We assessed American beech (Fagus grandifolia Ehrh), sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.) and yellow birch (Betula alleghaniensis Britt.) saplings density as functions of disturbance intensity (% basal area cut and overstory tree mortality rate (%)) and site factors. We also examined the effects of disturbance, site factors and relative density of American beech, red maple, sugar maple and yellow birch saplings on species diversity at the sapling layer. The density of American beech saplings decreased significantly with harvest intensity. High harvest intensity significantly reduced American beech sapling density at high depth-to-water sites. However, the densities of red maple and yellow birch saplings increased significantly with increasing harvest intensity. We found that high harvest intensities had less negative effect on sugar maple sapling density compared with American beech. Our results also showed that tree species diversity (Shannon diversity index (H′)) increased with harvest intensity up to about 75% and then declined. However, depth-to-water (DTW) significantly changed the magnitude of tree species diversity response to harvest intensity. Red maple appeared to have contributed more to species diversity than the other hardwood tree species. Given that sugar maple sapling density was generally higher than American beech at high harvest intensities in this study, management regimes that promote mid-tolerant species in American beech-presence stands may eventually benefit sugar maple more than American beech in these forest types. These strategies may also increase species diversity and improve forest ecosystems functions and services.

Identifying trees most likely to die after a partial cut in sugar maple or yellow birch stands

Many research findings related to tree mortality have been published since 2005, and it is now possible to assess postselection cut tree mortality risks in maple or softwood/yellow birch forest sta...

Soil hydraulic conductivity differences between upslope and downslope of two coniferous trees on a hillslope

ABSTRACTStanding trees influence the redistribution of soil water around the trunk and alter water movement under the canopy on hillslopes. We investigated soil properties around trees to clarify the effect of trees on soil hydraulic properties of soil surface layers on a slope. The intact tree and cut tree plots of two coniferous tree species, Cryptomeria japonica and Chamaecyparis obtusa, were considered in the northern part of Kyushu, Japan. The soil properties on the upslope and downslope of individual trees or stumps were compared. The soil near-saturated hydraulic conductivity (kns) on the upslope of individual trees and stumps was higher than that on the downslope for both species. Although the distribution patterns of kns were similar in all plots, the determinant factors of kns seemed to be different. In the Cr. japonica intact tree plot, more litter tended to accumulate on the upslope of individual trees, and it seemed to indirectly enhance kns. However, the results of the cut tree plot suggested that kns was affected by factors other than the litter layer biomass. In the Ch. obtusa intact plot, high water repellency of soil on the downslope of individual trees reduced kns. Organic matter tended to accumulate on the upslope of Ch. obtusa individual stumps and in combination with water repellency appeared to affect kns. Our findings showed that soil hydraulic conductivity was affected by the distance and direction from a tree on a slope and that the effect was maintained for a few years after cutting.

Trembling aspen root suckering and stump sprouting response to above ground disturbance on a reclaimed boreal oil sands site in Alberta, Canada

Trembling aspen (Populus tremuloides Michx.) is an important early successional species in the boreal region that commonly regenerates via root suckering and, to a lesser extent, stump sprouting after aboveground disturbance such as harvesting or wildfire. However, the response of aspen to disturbance on reclaimed oil sands sites is not known. To determine the suckering and sprouting response of 6-year-old seedling origin aspen growing on a reclamation site, we destructively sampled 87 individual trees in May 2017. Trees were selected across two soil types, forest floor-mineral mix and peat-mineral mix, and three height classes, 100–199 cm, 200–299 cm, and > 300 cm. In August 2017, we returned to each cut tree to assess the type (sucker vs. stump sprout) and abundance of regeneration. Aspen readily responded to disturbance; however, responses were highly variable between trees, ranging from zero to 47 suckers and zero to 42 sprouts. Trees growing on peat-mineral mix were 7.8 times more likely to produce at least one sucker and generally had a higher abundance of suckers. Tree height was also positively correlated with suckering probability and abundance, while competition from surrounding vegetation decreased the probability and abundance of suckering, especially when cover of competing species was greater than 52.5%. The probability of stump sprouting was not affected by soil type or tree size, but did decrease with increases in tree competition. Overall, trembling aspen respond vigorously to disturbances on mine reclamation sites which is a promising sign of resilience for these novel and young ecosystems.

Model for diameter distribution from assortments volumes: theoretical formulation and a case application with a sample of timber trade data for clear-cut sections

This study examined a theoretical model for stand structures from the volumes of pulpwood and saw logs of clear-cut stands. The average stem size was used to estimate the number of cut trees. The distribution was solved using nonlinear derivative-free optimization. The truncated 2-parameter Weibull distribution was used to describe the stand structure of the commercial stems. This method was first tested with harvester data collected from seven clear-cut stands in southern Finland. Validation included reliability in the stand characteristics and goodness-of-fit of the species-specific distributions. The distributions provided unbiased estimates for the saw log volume, while the bias in the estimated pulpwood volume was 2%. The standard stand characteristics from the Weibull distributions corresponded notably well with the harvester data. A Kolmogorov-Smirnov (KS) test rejected two distributions out of 21 cases, when the accurate input variables were available for the theoretical model. The results of the study suggest that the presented method is a relevant option for predicting the stand structure. In practice, the reliability of the presented method was dependent on the quality of the information available from the stand prior to cutting. With a timber trade data set, the solution for the distribution for a clear-cut section was found. The goodness-of-fit was dependent on the accuracy of the visually assessed timber trade variables. Especially the average stem size proved difficult to assess due to high number of understorey pulpwood stems. Due to overestimated average stem sizes, the solved number of harvested trees was underestimated. Less than 50% of the distributions predicted for clear-cut sections passed the KS test.

Environmental impact in building a new frontier

A three years research project along the plain section of the Roman frontier known as Limes Transalutanus has reached some peculiar conclusions. Between them one can count the fact that some sectors, summing three quarters of length of the northern section, although crossing open fields, has no obvious frontier obstacle. The common explanation, about ‘the state of art’, does not work this time, therefore one will need a rationale for that ‘anomaly’. The Romanian Plain of today is one of the most disfigured territories, due to the socialist exploitation of the land (mainly by draining and deforestations); consequently, it is impossible to make a historical assessment only on things today visible in the landscape. I tried to use all resources at hand, beginning with medieval documents and pursuing with cartographic depictions of several generations, place names and pedology, as much as an archaeologist can deal with them. The final answer is far simpler than expected: not all the sectors of the frontier were closed by manmade obstacles, because they were already secured by natural items, either thick forests or unexplored marshes. The only needed proof for a Roman boundary is the road running along the frontier, but this is difficult to prove on a field completely devoid of stone. I am suggesting also wooded barriers made of cut trees left on the spot, but such an obstacle leaves no archaeological traces.

A Survey on the Menace of Lingzhi Mushrooms on Trees in Shell Residential Area, Port Harcourt

Observations through routine tree surveys and reports by estate managers and residents show an increasing rate of sudden fall of healthy looking trees recently in Shell Petroleum Development Company of Nigeria Residential Area (SPDC RA), thus creating a high potential risk to lives and facility. An earlier survey had suggested that a weakening of the root system due to the presence of mushroom species of a cosmopolitan basidiomycete in the genus Ganoderma may be responsible for the tree falls. Consequently, a team was constituted for an emergency tree hazard hunt exercise using the approved criteria for tree cutting as terms of reference. During the tree hunt exercise, a survey was undertaken with the aim of identifying the mushroom species involved and type of disease, disease symptoms, method of infection/spread, any diagnostic tools for the disease as well as curative and preventive measures for the management of the disease in order to proffer suitable recommendations. Forty-one (41) out of a total of two hundred and seventy-one (271) trees surveyed (15%) were impacted by the mushroom. Disease symptoms include yellowing, necrosis, wilting of the palms fronds and development of a basidiocarp at the tree base. The fungus is soil-borne, spreading from root to root and by migration of airborne basidiospores from basidiocarp. It overwinters in dead woody debris and tree stumps. Some diagnostic tools have been developed both in the laboratory and field for the diagnosis of this disease which include; Calorimetric method using Ethylenediamine-tetraacetic acid, Ganoderma selective media, use of Polyclinal Antibodies (PAbs) and Polymerase Chain Reaction (PCR), Remote Sensing System, application of colour indices using multispectral and thermal camera as well as tomography instrument. The use of trench system, soil mounding, fungicidal treatment and replanting techniques have great potentials in the management of this disease. Periodic checks, routine removal of basidiocarps, geo-referencing and superimposing the impacted trees positions on an existing RA Base map and replanting the cut trees to re-vegetate the environment in phases with seedlings around the camp are recommended. Proper taxonomic study on the Ganoderma species diversity in the RA environment is necessary. Keywords: Shell Petroleum Development Company Residential Area (SPDC RA); Basidiomycete; Basidiocarp; Calorimetric method; Polyclinal Antibodies (PAbs); Polymerase Chain Reaction (PCR); Remote Sensing; Taxonomic study; etc.;

A Novel Approach to 3-D Change Detection in Multitemporal LiDAR Data Acquired in Forest Areas

Light Detection and Ranging (LiDAR) data have been widely used to characterize the 3-D structure of the forest. However, their use in a multitemporal framework has been quite limited due to the relevant challenges introduced by the comparison of pairs of point clouds. Because of the irregular sampling of the laser scanner and the complex structure of forest areas, it is not possible to perform a point-to-point comparison between the two data. To overcome these challenges, a novel hierarchical approach to the detection of 3-D changes in forest areas is proposed. The method first detects the large changes (e.g., cut trees) by comparing the Canopy Height Models derived from the two LiDAR data. Then, according to an object-based change detection approach, it identifies the single-tree changes by monitoring both the treetop and the crown volume growth. The proposed approach can compare LiDAR data with significantly different pulse densities, thus allowing the use of many data available in real applications. Experimental results pointed out that the method can accurately detect large changes, exhibiting a low rate of false and missed alarms. Moreover, it can detect changes in terms of single-tree growth, which are consistent with the expected growth rates of the considered areas.

Substitution of pig feed preparation using firewood with biogas in Samosir Island: transforming an environmental catastrophe into environmental, social, economic benefits

In Samosir Island, Indonesia pigs care was not environmentally friendly as people were used firewood in pig feed preparation. A series of research has been conducted from March until September 2017 which was preceded by survey. It was found that people cut tree for firewood. As Samosir Island was under Toba Go Green Project which was a tree planting project so feed pig preparation was in contrast to the project. More over, Indonesia has been committed to reduce its green house gases (GHG) by 26% in 2020, any mitigation on GHG was strongly recommended. One way of mitigation in Samosir was by installing biogas for pig feed preparation. 5 biodigesters 500 liters capacity each were installed in Parbaba Village, Samosir Island and biodigester input were pig manure, water hyacinth. Research design was Randomized Completely Design. Parameters were gas production, pH, temperature and C/N ratio. Biogas than used to cook feed pig. It was known that to cook for 5 finisher pigs, 3 kg firewood could be substituted by 250 liters of biogas.

La mort en soins palliatifs… et après ? Imaginaire de la mort chez des soignants en soins palliatifs

ObjectiveThe services of palliative care have a function to ensure a life-comfort for patients who cannot be cured. The activity of these structures is based on the evolution of the body and ends when death occurs. The end of a person's life corresponds to biological death. Future cannot be imagined, because there is nothing in a rationally conceptual vision of death. Death is the negation of life. However in every culture, imaginary of death has been developed. They all build a “beyond-death”. The concepts are generally carried by religions, which create a discourse and offer varied imaginary of postmortem life. Finally, one can say that there are two imaginary about death. One that affirms there is no “beyond-death” but an absolute end; the other that death is a passage towards a life, which continues in other forms. In a case death is an end, in the other it is a transformation. These two concepts have very different consequences for patients as for carers. This aim of this study is to locate which concepts of death are present for carers in palliative care and if transformation death is present, how it functions. Patients, materials, methodFive volunteers, who are carers in palliative care, took the Test of the Three Trees, a method which helps to speak about death, in analogical ways by using drawings and stories with trees. The protocol has 12 stages divided into three phases. Death can thus appear in various manners. ResultThe topic of death is very present in the protocols. It is divided into two components: death as an end for 64% of the statements and death as a transformation for 36%. Two case studies illustrate the two conceptions. In phase II of the protocol, volunteers are asked to draw a tree of nightmare and a tree of dream and to tell their respective dreams. The drawings, which represent death as an end, show for one, a tree lying on the ground and for the other a cut tree. The theme is clearly identified. The tree tells the disaster of death, as opposed to the life. Death can be pictured and named. At stage 11, the person tells a dream which associates these two trees. In one case, the tree of nightmare is burnt but its ashes allow the tree of dream to have beautiful fruit, which are eaten by children. In the other case, the tree of nightmare is cut but its roots remain in the ground and they are used by the tree of dream. Thus the two trees representing death continue to live. In these two cases, the tree of nightmare, which symbolizes death as an end, is integrated in a process. Its life continues in another form: it is death as a transformation. The tree is a good mediation to approach a topic, which cannot be represented. Death as a transformation is not a final event, which stops a life, but a process, which contributes to the general process of life. Death and life are the two faces of a phenomenon, which must be thought like a process without an end. ConclusionContrary to death as an end in relation with biological death, death as a transformation opens the possibility of a future according to a spontaneous movement present in the psyches. This alternative forms an important resource for carers confronted daily to death but also for patients. That gives a new perspective to the end-of-life and helps in professional practices. This alternative of death as a transformation makes one think that this trend corresponds to a natural movement of the psyche to always create a beyond. Perhaps, the space of beliefs and of religions extends this orientation?

Quaking aspen woodland after conifer control: Tree and shrub dynamics

Western juniper (Juniperus occidentalis spp. occidentalis Hook.) woodlands are replacing many lower elevation (<2100 m) quaking aspen (Populus tremuloides Michx.) stands in the northern Great Basin. We evaluated two juniper removal treatments (Fall, Spring) to restore aspen woodlands in southeast Oregon, spanning a 15-year period. The Fall treatment involved cutting 1/3 of the juniper followed by a high severity broadcast burn one year later in October 2001. The Spring treatment involved cutting 2/3 of the juniper followed by a low severity broadcast burn 18 months later in April 2002. The cut trees increased the amount of dry fuels to carry fire through stands. We tested the effectiveness of treatments at removing juniper from seedlings to mature trees, assessed aspen ramet recruitment and development, and evaluated recovery of the shrub layer. In the Fall treatment, burning eliminated all remaining juniper trees and saplings, stimulated an 8-fold increase in aspen density (16,000 ha⁻¹) and increased aspen cover 6-fold compared to the untreated controls. After 15 years, aspen density in the Spring treatment was about 1/3 of the Fall treatment, however, aspen cover did not differ from the Fall treatment. Because spring burning was less effective at removing juniper, leaving about 20% of the mature trees and 50% of the saplings, retreatment of conifers will be necessary to maintain the aspen community. In the Fall treatment, juniper began establishing within 15 years after conifer control indicating retreatment might be necessary earlier than expected. Total shrub cover and density in the Spring treatment was greater than the control and Fall treatments. Cover and density of sprouting shrub species, particularly western snowberry (Symphoricarpus oreophilus Gray), increased and were greater in the Spring treatments than the Fall treatment where they had declined. Shrubs that increased in the Fall treatment were species where seed germination is enhanced by fire, especially snowbrush (Ceanothus velutinus Douglas ex Hook) and wax currant (Ribes cereum Dougl.). If an objective is to maintain or increase native understories the Spring treatment was more effective than the Fall treatment for recovering the shrub layer.

Regeneration dynamics of planted seedling-origin aspen (Populus tremuloides Michx.)

Aspen (Populus tremuloides Michx.) is a foundational tree species of the North American boreal forest. After disturbance, clonal aspen stands quickly achieve canopy closure by sending up numerous clonal shoots (root suckers) from their lateral root system. Controlled aboveground disturbance will commonly induce prolific root suckering and thereby increase stem density in clonal aspen stands, but it is unclear if increases in stem density will be observed in planted seedling-origin aspen stands. The objectives of this study were to determine (1) overall root suckering response of planted aspen to aboveground disturbance; (2) if different cut heights of the stem or infliction of root damage impact the number of root suckers produced. We found that planted aspen regenerated readily after disturbance, averaging five root suckers per cut tree. However, individual response was highly variable, ranging from zero to 29 root suckers per root system. Of the cut trees, 75% produced at least one root sucker and 60% produced at least one stump sprout. Cutting trees close to the soil surface produced more root suckers than leaving a 25 cm stump. While root system size (mass and length) was well correlated with aboveground measures of planted aspen, root suckering was not related to root system size. As a result of increased forest reclamation efforts in the boreal forest region the planting of aspen has become a more common practice, necessitating a better understanding of the regeneration dynamics and root suckering potential of these planted and seedling-origin aspen forests.

Cutting down $\mathbf{p}$-trees and inhomogeneous continuum random trees

We study a fragmentation of the p-trees of Camarri and Pitman. We give exact correspondences between the p-trees and trees which encode the fragmentation. We then use these results to study the fragmentation of the inhomogeneous continuum random trees (scaling limits of p-trees) and give distributional correspondences between the initial tree and the tree encoding the fragmentation. The theorems for the inhomogeneous continuum random tree extend previous results by Bertoin and Miermont about the cut tree of the Brownian continuum random tree.

Environmental Determinants to Household Food Security in Kyangwithya West Location of Kitui County

This study analyzed the environmental determinants to household food security in Kyangwithya West location of Kitui County. Quantitative data were collected using systematic sampling method to select 344 households with the aid of a structured questionnaire. Qualitative data was obtained from key informants and focus group discussants that were purposively sampled. The data were subjected to descriptive statistics and presented using tables and verbatim narratives. The findings revealed that majority (89%) of the participants had experienced weather changes in the study area and a significant number (27%) were food secure. Few households (11%) had not observed any weather change and (28%) of them were food secure. The weather changes observed were assessed and inadequate rainfall was observed by majority (82%) of the respondents (26%) of whom were food secure. High temperatures were reported by (12%) of the respondents (28%) of whom were food secure. Recurrent drought was reported by the least number of respondents (6%) that were the most food secure (30%). Influence of cutting trees on household food security revealed that majority (82%) of the respondents do not cut tree and are more food secure (29) compared to the few (18%) who cut trees. The results reveal that majority of the households observed changes in weather patterns although the percentage of the food secure was low. Inadequate rainfall was the most observed weather change with the most influence on household food security followed by high temperatures and recurrent droughts. Majority of the households did not cut trees and are more food secure than those that cut trees. Environmental factors are thus significant determinants to household food security. The study recommended that regular updates on weather forecast be made available to households to enable them make informed plans during planting seasons.

American elm cultivars: Variation in compartmentalization of infection by Ophiostoma novo‐ulmi and its effects on hydraulic conductivity

SummaryFive cultivars and two populations of wild‐type seedlings of American elm (Ulmus americana), 3 and 4 years old, were examined for differences in their abilities to compartmentalize and resist infection by artificially inoculating with Ophiostoma novo‐ulmi. Morphological characteristics of tree defence, often referred to as the compartmentalization of decay in trees model, were used as a conceptual framework, with particular emphasis on the limiting of tangential spread of infection within the xylem and barriers that limit spread outwards to cells formed after infection. To investigate the change in functional xylem over time, 3‐year‐old trees were assessed at multiple time points following inoculation for hydraulic conductivity. Three and four‐year‐old cut trees were placed in 0.1% w/v safranin O for 18 to 24 hr to indicate functional xylem. Transverse sections of the stained stems were used to calculate per cent of sap‐conducting xylem area and the per cent of circumference conducting of first formed cells and later formed cells. At each collection time, trees were assessed for disease severity on a 1–12 scale, based on the percentage of permanent wilt in the crown. There was considerable variation between cultivars in disease severity and their capacity to localize and resist infection. “Prairie Expedition,” which had the lowest disease severity rating in 2015 and the second lowest in 2016, consistently limited the spread of infection into newly formed xylem and had functional xylem around the entire circumference of the stem at 90 days post‐inoculation. “Valley Forge” in 2016 had the lowest overall disease severity rating and was the only cultivar to consistently limit the tangential spread of infection within extant xylem. This research identifies key characteristics that some cultivars have to resist and limit infection and provides new information that can be used in disease screening programmes to evaluate other cultivars and older plant material.