Mean Stem Height Research Articles

Effects of Water Stress on Growth and Chlorophyll Contents of Ocimum gratissimum L. (Basil) [Lamiaceae

Ocimum gratissimum is an essential plant because of its wide food and medicinal usage. Despite its relevance, its morpho-physiological compositions are influenced by several abiotic stresses. Hence, this study examined the effects of water stress on the growth and chlorophyll contents of O. gratissimum. Seedlings of O. gratissimum were grown in twenty-four pots, two per pot and were arranged using a complete randomized design with four groups: Very Wet O. gratissimum (VWO), Moderately Water Stress O. gratissimum (MWSO), Strongly Water Stress O. gratissimum (SWSO) and Adequately Watered O. gratissimum (AWO) as control. Fifty centiliters of water was applied in AWO once daily, VWO twice daily, MSWO once in three days and SWSO once a week. Growth parameters: Stem height, number of leaves, leaf area, stem girth and petiole length were determined one week after treatment for six weeks. Chlorophyll contents were determined at two weeks intervals after treatment for eight weeks. Descriptive statistics such as mean±standard deviation and one-way Analysis of Variance (p < 0.05) were done using SAS software. Results obtained showed the highest mean stem height (27.50 ± 0.29 cm), number of leaves (37.00 ± 9.0), leaf area (735.7 ± 4.12 cm2), stem girth (0.40 ± 0.00 cm) and petiole length (7.20 ± 0.40 cm) in VWO. Similar results were obtained for chlorophyll (56.70 ± 0.65 mg–1). It could be concluded that regular watering of O. gratissimum could promote growth and increase chlorophyll contents of the plant.

Population dynamics and regeneration of Shorea roxburghii, a threatened timber species in Southern region, Viet Nam

Abstract. Bao TQ, Viet LH, Hai NH, Tuan NT, Cuong LV. 2021. Population dynamics and regeneration of Shorea roxburghii, a threatened timber species in Southern region, Viet Nam. Biodiversitas 22: 5649-5656. Despite its wide distribution in South and Southeast Asia, Shorea roxburghii G. Don is classified as Vulnerable in the IUCN Red List of Threatened Species due to over-exploitation for its valuable timber. This study aims to investigate the population dynamics and regeneration of S. roxburghii in southeastern Vietnam, serving for conservation and sustainable development plan. Six plots of 2,500 m2 each (50 m × 50 m) were established at two forest conditions: i) forest with standing volume > 200 m3/ha (SV>200), and ii) < 200 m3/ha (SV<200); to investigate stems with diameter at breast height (DBH) ? 5 cm and that < 5 cm. Moisture (%), pHH2O of the topsoil and the occurrence of regenerating S. roxburghii were collected from 125 points in the study site. The results indicated that mean stem height, DBH, basal area, and aboveground biomass were significantly higher at the forest stand with SV>200 than that at the forest stand with SV<200 for the pool of all species. Similar higher figures were found in SV>200 for the pool of S. roxburghii compared to that in SV<200, except mean DBH, which was larger in SV<200. There were missing stems with DBH < 5 cm in SV<200, while it was numerous in SV>200 (1,313 stems/ha). DBH/stem distributions in both forest types had an inverted-J shape with a peak at 10-15 cm DBH for the pool of all species, while there was no clear pattern for the pool of S. roxburghii in both forest types. Regression analysis indicated that higher total crown area of stems ? 23 tall leads to higher S. roxburghii stems, while the higher total crown area of stems < 23 tall leads to fewer S. roxburghii stems with DBH < 5 cm. It is concluded that the total crown area of forest stand plays an important role in the sustainable regeneration of S. roxburghii. Silvicultural treatment should be applied to reduce stand density and crown area of stems < 23 m tall to enhance sunlight reaching the forest floor for germination, growth, and survival of S. roxburghii. The moisture of the topsoil ranging from 60 - 80% and the pHH2O ranging from 3.8 - 4.6 are suitable conditions for natural regeneration of S. roxburghii.

Yield Performance of Newly Developed Cassava Varieties in Response to Inorganic Fertilizers

A study was conducted at Kyambogo University Farm in randomized complete block design with three replications to assess the effect of NPK (17:17:17) fertilizer on the growth and tuber yields of two newly developed cassava (Manihot esculenta Crantz) varieties, NAROCASS 1 and NASE 14. Cassava varieties were assigned to the main plots, while fertilizer rates (zero/control, 200, 400, 600 kg/ha) were sub-plots. Fertilizer was applied in two splits, at planting and four months after planting. Fertilizer application significantly (P<0.05) increased the cassava stem heights to first branching and at harvest, and the number of stems per plant when compared with the control treatments. Mean stem heights to first branching and at harvest of plants that received NPK were higher than those of the respective control treatments by 62.8 and 70.5% for NAROCASS 1, and 57.0 and 76.5% for NASE 14, respectively. Fertilizer rate of 400 kg/ha significantly increased the lengths, numbers of tubers and tuber yields per plant when compared with the control treatments. Mean lengths, numbers of tubers and tuber yields of plants that received NPK were higher than those of respective control treatments by 48.2, 36.9 and 68.3% for NAROCASS 1, and 39.9, 50.5 and 67.6% for NASE 14, respectively. Therefore, to achieve optimum tuber yields of newly developed cassava varieties, farmers should integrate NPK fertilizer application into already existing management practices, particularly the use of high quality planting materials and integrated pest, disease and weed management. However, government ministries concerned should ensure that inorganic fertilizers are readily accessible and affordable to farmers.

Nonlinear yield models for young Tectona grandis L. f. stands in Nnamdi Azikiwe University Awka, Southeastern Nigeria

Yield models are very important to forest management, especially for site quality assessment, subsequent inventories, timber valuation and assessment of stand growth. This study developed yield models for the young Tectona grandis stands in Nnamdi Azikiwe University Awka, Southeastern Nigeria. These models were necessary to the guide forest managers in timber valuation as well as monitoring growth of the stand. Data for this study was collected through complete enumeration method, tree height and stem diameters of the 295 Teak stands were measured. Non-destructive method (Newton’s formula) was used in computing individual tree volumes. The tree growth variables data were subjected to descriptive statistics and used for fitting five nonlinear regression functions. The mean stem height, diameter at breast height and volume were 10.6 m, 8.9 cm, 0.032 m3, respectively. Out of the five yield equations fitted; the generalized combined variable model had the best predictive ability; with the lowest root mean square error (0.0084 m3) and Akaike information criterion (-2809). Therefore, the generalized combined variable model was recommended for yield estimation of Tectona grandis.

The Effects of Waste Contaminated Soil on the Productive Capacity of Capsicum frutescens I. Yusuph, A. Raheem, V. Simpson, U. Aliboh, T.O.A Adeyemi, C. Igboanugo, and H. O. Sawyer ABSTRACT The effects of waste contaminated soil on the growth and yield o

The effects of waste contaminated soil on the growth and yield of Capsicum frutescens was studied. Soil samples were collected from: (1) chemical dump sites (2) Cocoa Processing Locations, (3) Federal University of Technology, Akure (FUTA) farms (i.e. Obanla, Obakekere and Abaoyo), and (4) a fallow field (control) all within Akure metropolis. The electrical conductivity and pH of the different soils were determined using standard methods while heavy metal analysis of the various soil samples was carried out using Buck 200 Atomic Absorption Spectrophotometer (ASS) after digesting the samples. The length of stem and leaves were recorded. Soil samples obtained from all the cocoa processing locations and chemical dumpsites in Akure metropolis showed no growth. Meanwhile, the control showed growth of C. frutescens. The highest height of stem was in Obanla on day 29 (15.92 ± 0.82 cm) while that of leaf (4.06 ± 1.32 cm) was in Obakekere on the same day. The control had higher mean stem height of 24.67 ± 1.32 cm on day 29 and 6.17 ± 0.17 cm for leaf on same day. Although, relatively higher organic matter was recorded in FUTA area with Obakekere having the least of 4.26±0.06% and Abaoyo having the highest of 4.36 ± 0.06%, this was lower than the control which had 4.50 ± 0.12%. Generally, the heavy metals concentration was higher in the cocoa processing locations and chemical dumpsites, as compared to FUTA area and the control. The low organic matter and heavy metal concentration in the soils cannot guarantee food security in terms of intensive crop production.

Population survey of Milicia excelsa, Pouteria adolfi-fridercii, Antiaris toxicaria and Prunus africana in south and south-western Ethiopia: implications for domesticating and establishing Seed Production Areas

The population dynamics and genetic qualities of stem height and dbh of the populations of Milicia excelsa, Pouteria adolfi-fridercii, Antiaris toxicaria and Prunus africana were assessed and studied in 14 forest ecosystems in south and south-western Ethiopia. A systematic random quadrat sampling technique was employed to identify potential habitat area for selected timber species in south and south-western Ethiopia. So, a total of 10 parallel transect lines were set out across each forest habitat. Milicia excelsa was assessed in four forest ecosystems; Bebeka -Duduka natural forest (45 tree stem ha-1) and Yayu coffee mixed forest (40 tree stem ha-1) appeared to have relatively denser population of M. excelsa compared to the other pilot forests. Similarly, statistically larger stem height (m) is observed in Bebeka-Duduka natural forest (x̅=29.5, SD=4.2) and larger dbh size (cm) in Bebeka 1 coffee mixed forest (x̅=48.5, SD=25.2) at p<0.05. Hence, Bebeka-Duduka natural forest and Bebeka 1 coffee mixed forests are identified for in-situ SPA establishment project of the target species. Pouteria adolfi-fridercii was assessed in eight forest ecosystems; Masha-Gora shewi forest appeared to have dense population of P. adolfi-fridercii (150 tree stem ha-1) followed by Bebeka-Kebereta (80 tree stem ha-1) as compared to the remaining pilot forests. However, statistically larger stem height (m) is scored in Bebeka 2 natural forest (x̅=30.6, SD=2.98) and Bebeka-kebereta forest (x̅=30.0, SD=4.4) and larger dbh size (cm) in Bebeka 2 natural forest (x̅=96.5, SD=19.9) at p<0.05. So, Bebeka 2 natural forest and Bebeka-kebereta forest are identified for SPA establishment project of the target species. Antiaris toxicaria was assessed in two forest ecosystems where both forest habitats appeared to have the same density of Antiaris toxicaria in hectare. Moreover, analyses of mean stem height (cm) of Bebeka 1 forest (x̅=21.4, SD=5.2) and Bebeka-kebereta forest (x̅=22.4, SD=2.7), and mean dbh size (cm) of Bebeka 1 forest (x̅=48, SD=16.4) and Bebeka-kebereta forest (x̅=48, SD=8.2) appeared to have not significantly different at p<0.05. Prunus africana was assessed in five forest ecosystems; Masha-Gora shewi forest appeared to have dense population of Prunus africana (150 tree stem ha-1) followed by Kaho-shemeta forest (130 tree stem ha-1) as compared to the remaining pilot forests. However, statistically larger stem height (m) is scored in Kaho-shemeta natural forest (x̅=31, SD=7.6) and larger dbh (cm) in Masha-Gora shewi forest (x̅=64.7, SD=28.2) at p<0.05. As the result, Kaho-shemeta natural forest and Bonga-Teja-adela forest are identified for establishment of seed production area of the target species in-situ. Hence, while implementing the project of domestication and seed production area establishment in south and south-western Ethiopia, in-situ and ex-situ areas must be selected and delineated in accordance with this preliminary information of the population dynamics and genetic qualities of stem height and diameter at breast height. The survey data generated in this study would bridge the research gap in relation to the population status of the target tree species in the designated area.

Intraspecific diversity at two trophic levels influences plant–herbivore interactions

AbstractDiversity within species can have community‐level effects similar in magnitude to those of species diversity. Intraspecific diversity in producers and consumers has separately been shown to affect trophic interactions, yet we have little understanding of how variation at these two levels could simultaneously affect trophic interactions. Salt marshes dominated by Spartina alterniflora are an ideal system in which to ask this question as this plant exhibits substantial genetically based trait variation. Further, herbivores can have sizable impacts on Spartina, but the impact of herbivore trait variation is not well understood. We conducted an experiment in a Massachusetts salt marsh to determine how herbivorous crab (Sesarma reticulatum) size diversity and Spartina genotypic diversity affect the plant community. Herbivore effects on plant traits varied by herbivore size, with large crabs generally having stronger impacts on plants. At times, the effect of small crabs on plant traits depended on plant genotypic diversity. The effects of crab size diversity (i.e., small and large crabs combined) were most often predicted by the independent effects of each size class, though there were synergistic effects on stem density, flowering stems, and mean stem height. Finally, we tested whether herbivore size or size diversity could have reciprocal effects on plant genotypic diversity. Small‐ and mixed‐crab treatments promoted plant genotypic richness, whereas large crabs did not. Our results demonstrate that intraspecific diversity at multiple trophic levels can have simultaneous and sometimes interactive effects on species interactions, highlighting the importance of variation within species for understanding species interactions and community processes.

Forage growth, yield and nutritional characteristics of four varieties of napier grass (Pennisetum purpureum Schumach) in the west Usambara highlands, Tanzania

Abstract Low pasture biomass production and dry seasons fodder scarcity are among the major challenges affecting productivity of dairy cattle in Tanzania. Field experiments were set to evaluate growth, biomass yields and nutritional contents of four napier grass (Pennisetum purpureum Schumach) varieties as feed for ruminants. Experimental napier varieties included Ouma, Kakamega 2 (KK2), Bana and local napier (LN). The study was conducted in the Western Usambara highlands (WUHs) in Tanzania between December 2016 and April 2017 (110 days). The results indicated that the varietal mean stem heights differed significantly (P

Rapid production of willow biomass using a novel microcutting-based field planting technology

Phytoremediation is becoming recognised as a promising environmental approach to decontaminate land. However, establishing large-scale plantations for phytoremediation purposes can bear prohibitive costs. In order to deliver large-scale phytoremediation projects, easily implemented plant establishment solutions need to be available to practitioners. Here, we present a novel planting technology based on willow microcuttings for the rapid establishment of phytoremediation plantations. An experiment was performed testing the effect of microcutting planting density and diversity on various growth parameters including aboveground biomass yields. After two growing seasons, aboveground dry biomass reached an equivalent of 23.1 t/ha. Willow microcutting planting density and diversity did not significantly affect biomass yields, although other growth parameters (survival, stand density and mean stem height) differed across treatments. Our results suggest that this willow microcutting planting technology is viable at large-scale, robust across willow species and represents a lower cost alternative to more traditional planting technologies.

Competitive interactions between native Spartina alterniflora and non-native Phragmites australis depend on nutrient loading and temperature.

We explored the nature and impact of competitive interactions between the salt marsh foundational plant Spartina alterniflora and invasive Phragmites australis in New England under varying levels of anthropogenic influence from nutrient loading and temperature warming. Plants were grown with and without competition in mesocosms over a four-month growing season. Mesocosms were split evenly among three levels of nutrient additions and two temperatures varying by an average of ~3° C, manipulated using small greenhouses. We measured aboveground productivity as total biomass, numbers of new stems, and mean stem height. Nutrient enrichment increased all growth parameters, while competition generally reduced aboveground biomass and the production of new stems in both species. Most importantly, smooth cordgrass suffered no negative consequences of competition when no nutrients were added and temperature was elevated. The results of this study suggest that minimizing nutrient loading into coastal marshes could be an important factor in slowing the spread of common reed into the low marsh zone of New England salt marshes as global temperatures continue to warm.

AFRICAN MAHOGANY SUBMITTED TO DRIP IRRIGATION AND FERTILIZATION

ABSTRACT African mahogany (Khaya ivorensis A. Chev.) is a tree species that has been increasing in Brazilian commercial planting. However, the lack of water and nutrition are great obstacles for crop production. The aim of this study was to evaluate the growth of young mahogany plants submitted to drip irrigation and topdressing. The experimental design was of randomized blocks, with three repetitions in subdivided plots. Treatments consisted of drippers: 1, 2 and 3plt-1; flows: 2, 4 and 8L h-1, and a treatment without irrigation. For topdressing, subplots levels were, as follows: 1) 17.5 and 25.2; 2) 35.1 and 50.1; 3) 52.5 and 75.0; 4) 70.0 and 100.2; and 5) 87.5 and 125.1 g plant-1 N and K2O, respectively, divided into five bimonthly applications, which started in the 4th month after planting. Plant height, diameter at root collar and at breast height (DBH), and stem height were evaluated. Results showed statistically significant differences (P>0.05) between irrigated and non-irrigated plants. Mean plant height ranged (from 2 to 20 months in field) from 0.33 to 3.25 and 2.67m for irrigated and non-irrigated plants, respectively. Mean stem height ranged from 0.23m to 0.87 and 0.71m for irrigated and non-irrigated plants, respectively. Thus, irrigation with 1 dripper per tree and flow of 2L h-1 was able to supply mahogany water requirements in the first two years in field. Trees have not responded to N and K topdressing at the beginning of the cycle.

Growth of Common Brackish Marsh Macrophytes Under Altered Hydrologic and Salinity Regimes

Coastal marsh plants are increasingly subject to physicochemical stressors under rising sea levels, and the maintenance of marsh ecological functions can depend on the ability of individual species and communities to tolerate or adapt to altered conditions. We conducted a greenhouse experiment to identify hydrology and salinity effects on growth of three common brackish marsh macrophytes of coastal Florida, USA: Distichlis spicata, Juncus roemerianus, and Spartina bakeri. The species were potted as monocultures and exposed to three salinities (0, 15, or 28 psu) and two hydrologic conditions (saturated, tidal) over 22 months. Final stem density of J. roemerianus and S. bakeri did not differ among treatments. In D. spicata, however, stem density was lowest at 28 psu and lower in tidal compared to saturated conditions. Mean stem height of all species was lowest at 28 psu. Aboveground biomass of J. roemerianus was not affected by the treatments, but in D. spicata and S. bakeri it was lowest at 28 psu. Results indicated that J. roemerianus was the most adaptable species and may, therefore, be more resilient to climate-change driven stressors. However, plant-plant interactions such as interspecific competition and facilitation can alter the response of individual species to environmental factors.

Accuracy of optical image analysis compared to conventional vegetation measurements for estimating morphological features of emergent vegetation

In this paper we evaluate the effectiveness of using optical image analysis to determine plant morphology for an emergent species of salt marsh vegetation, threesquare bulrush (Schoenoplectus pungens), and compare the results to conventional vegetation measurement methods. We find that mean stem height may be estimated optically to within 10% of mean stem height measured with conventional methods and that total above ground biomass may be estimated by lateral percent cover values between 0 and 70% (R2 = 0.89, linear regression) within a 10 cm–60 cm depth of vegetation. Additionally, we show that stem height may be used to estimate stem diameter by linear regression (R2 = 0.94). The product of the plant stem height, stem diameter and density measured by conventional methods are shown to correspond with the horizontal two-dimensional projection of vegetation estimated by image analysis. The optical method provided robust estimates when the depth of field is between 10 cm and 60 cm. When the depth of field exceeded 60 cm, the images were saturated, resulting in a loss of information.

Interactions among herbivory, climate, topography and plant age shape riparian willow dynamics in northern Yellowstone National Park, USA

Summary Understanding how the environmental context modifies the strength of trophic interactions within food webs forms a central challenge in community ecology. Here, we demonstrate the necessity of considering the influence of climate, landscape heterogeneity and demographics for understanding trophic interactions in a well‐studied food web in Yellowstone National Park, USA. We studied riparian willow (Salix spp.) establishment and stem growth reconstructed from tree rings on the northern range of Yellowstone over a 30‐year period that included the reintroduction of a top predator, the grey wolf (Canis lupus). We used climate variables (annual precipitation, stream flow and growing season length), herbivore abundance and landscape descriptors (elevation and topographic wetness index) to predict establishment and growth processes through time before and after the reintroduction of wolves. We fitted Bayesian hierarchical models to establishment data and time series of individual stem heights from 1980 to 2008. Explaining variability in establishment required models with stream flow, annual precipitation and elk abundance. Climate, trophic and landscape covariates interacted with stem age to determine stem height and growth rate through time. Growth rates of most stems ages (2+) declined after the reintroduction of wolves. However, stem growth rates naturally declined with age, and the decline we observed was coincident with faster growth rates for the youngest stems. Mean stem heights at age have remained relatively stable through time for most age classes. Estimated effects of landscape topography had approximately the same magnitude of effect on stem growth rate at age as elk abundance. Synthesis. We show that the effects of modification of a food web cannot be predicted by studying trophic dynamics in isolation. No single driver explained patterns of willow establishment and growth over the past three decades in Yellowstone. Instead, interactions among trophic forces, interannual climate variability and landscape topography together shaped how the ecosystem responded to perturbations. Top‐down effects of ungulates on riparian woody vegetation must be considered in the context of plant age, and climate and landscape heterogeneity.

Effects ofAlbizia saman(Jacq. Mull) leaf mulch on vegetative growth of maize (Zea maysL.) and soil chemical properties through biomass transfer

The study presents the effects of Albizia saman (Jacq. Mull) leaves in a biomass transfer as a source of organic fertilizer on the soil chemical properties and vegetative growth of maize (Zea mays) compared with NPK (15-15-15) in greenhouse condition. Albizia saman leaves and NPK (15-15-15) were applied at the rate of 2.5, 5.0 and 7.5 t/ha or 60, 90 and 120 kg/ha respectively, separately or in combination. The findings revealed that application of 2.5 t/ha A. saman leaves produced the maximum values for mean leaf number, leaf area and stem height (7.77, 212.24 cm2 and 49.67 cm, respectively) among the leaf much treatments but were not significantly different from those obtained by applying 90 kg/ha NPK fertilizer (7.86, 225.55 cm2 and 48.78 cm, respectively). However, the maximum number of leaf (8.4), leaf area (240.5 cm2), plant height (54.64 cm) and biomass (16.17 g) were obtained from the combination of 2.5 t/ha leaves with 90 kg/ha NPK. There was significant improvement in the soil chemical status with the application of 2.5 or 5.0 t/ha A. saman leaves whereas the application of 5.0 t/ha A. saman leaves experienced the highest value for organic carbon (3.56%), total nitrogen (0.23%) and potassium (0.16 mg/kg) and 2.5 t/ha leaves gave the highest value for available phosphorus (22.30 mg/kg). It can, therefore, be inferred that the application of 2.5 t/ha A. saman leaves as source of organic fertilizer will give a better growth of maize and the combination of this quantity with 90 kg/ha of NPK would give better results in crop yield and maintenance of soil fertility.

Altitudinal patterns of stand structure and herb layer diversity of <I>Picea schrenkiana</I> forests in the central Tianshan Mountains, Northwest China

Altitude is a useful indicator to examine patterns of forest structure and species diversity in relation to environmental factors. In this study, the altitude patterns of forest stand structure and species diversity were analyzed across 20 plots in the Tianchi Nature Reserve, Northwest China. The results showed that mean stem height (Hm), maximum stem height (Hmax) and mean stem diameter at breast height (Dm) of Picea schrenkiana trees all decreased significantly with increasing altitude. Potential tree height (H*) decreased while stem taper increased significantly as altitude increased, suggesting remarkable altitudinal changes in biomass allocation between the diameter and height growth of Picea schrenkiana. Understory herbaceous richness increased significantly with increasing altitude, or with decreasing total basal area (TBA), Hm and stand volume (Volume). High light availability for understory herbs might account for the higher species richness at high altitude. Sorensen Index decreased significantly with the increase in altitude intervals, while the Cody Index demonstrated a converse pattern, suggesting greater differences in species composition with larger distances.

Community Structure and Conservation of Wild Fruit Forests in the Ili Valley, Xinjiang

Ili Valley in Xinjiang is one of the distribution centers of wild fruit species in the world. In this study,the species richness and structure of wild fruit forests in the Ili Valley were analyzed based on the investigated data from 67 sample plots. The results show that Juglans regia,Malus sieversii,Armeniaca vulgaris and Prunus sogdiana forests are the main wild fruit forests in the Ili Valley. In total,207 species in 141 genera and 46 families have been recorded. Species richness is higher in the A. vulgaris and P. sogdiana forests than that in the J. regia and M. sieversii forests. Stem density of the M. sieversii forests is significantly higher than that of the A. vulgaris forests. Mean stem height (Hm) of the J. regia forests is higher than that of the P. sogdiana forests. There is no significant difference in mean stem diameter at breast height (Dm) among the four forest types. Species richness tends to decrease,whereas Hm and Dm tend to increase,and there is no significant change of stem density with the increase of altitude. The results of a canonical correspondence analysis (CCA) reveal that the J. regia forests are mainly distributed in the warm areas,whereas the M. sieversii forests in the cold regions,and the A. vulgaris forests widely across the Ili Valley. Compared with other three forest types,P. sogdiana forests are only distributed in the mountainous areas in Huocheng County,where water availability is relatively high. The wild fruit forests in the Ili Valley are suffering from the severe destruction due to the intensive human activities,and they should be protected in some ways,such as the collection of germplasm resources and ex-situ conservation.

Community Structure and Its Affecting Factors of Mountain Coniferous Forests in Xinjiang, China

Spatial distribution patterns and environmental factors of forests are one of the primary topics of forest ecology. In this paper,the patterns and affecting factors of community structure of mountain coniferous forests in Xinjiang are explored after carrying out the survey of 120 plots of 11 locations in the Altay Mountains (Altay),northern slope of the Tianshan Mountains (NT in abbreviation,the same below),southern slope of the Tianshan Mountains (ST) and the Kunlun Mountains (KL). The results show that the mean stem height (Hm),maximum stem height (Hmax),mean stem diameter at breast height (DBHm),maximum stem diameter at breast height (DBHmax),total basal area (TBA) and stem volume of coniferous forests were the highest in NT,followed by Altay,ST and KL. There was no significant difference of stem density among the four regions. Among different forest types,community structure characteristics of Juniperus centrasiatica and J. jarkendensis forests were all lower significantly than those of other forests. In Xinjiang,Hm,Hmax,DBHm and TBA of mountain coniferous forests decreased significantly with the increase of altitude and mean annual temperature (MAT),but increased significantly with the increase of annual precipitation (AP). A general linear model (GLM) indicated that AP,aspect and moisture of plots were the most important factors affecting community structure of these coniferous forests in Xinjiang.

Genetic variation for susceptibility to storm-induced stem breakage in Solidago altissima: The role of stem height and morphology

While storms can have obvious ecological impacts on plants, plants’ potential to respond evolutionarily to selection for increased resistance to storm damage has received little study. We took advantage of a thunderstorm with strong wind and hail to examine genetic variation for resistance to stem breakage in the herbaceous perennial Solidago altissima. The storm broke the apex of nearly 10% of 1883 marked ramets in a common-garden plot containing 26 genets of S. altissima. Plant genets varied 20-fold in resistance to breakage. Stem height was strongly correlated with resistance to breakage, with taller stems being significantly more susceptible. A stem’s growth form (erect versus nodding) had no detectable effect on its resistance to breakage. Therefore, we rejected the hypothesis that a function of the nodding, or “candy-cane,” morphology is protection of the apex from storm damage. The significant genetic variation in S. altissima for stem breakage suggests that this plant has the capacity to respond to selection imposed by storms – particularly through changes in mean stem height. Tradeoffs between breakage resistance and competition for light and pollinators may act to maintain a large amount of genetic variation in stem height.

Predicting performance for ecological restoration: a case study using Spartina alterniflora

The success of population-based ecological restoration relies on the growth and reproductive performance of selected donor materials, whether consisting of whole plants or seed. Accurately predicting performance requires an understanding of a variety of underlying processes, particularly gene flow and selection, which can be measured, at least in part, using surrogates such as neutral marker genetic distances and simple latitudinal effects. Here we apply a structural equation modeling approach to understanding and predicting performance in a widespread salt marsh grass, Spartina alterniflora, commonly used for ecological restoration throughout its native range in North America. We collected source materials from throughout this range, consisting of eight clones each from 23 populations, for transplantation to a common garden site in coastal Louisiana and monitored their performance. We modeled performance as a latent process described by multiple indicator variables (e.g., clone diameter, stem number) and estimated direct and indirect influences of geographic and genetic distances on performance. Genetic distances were determined by comparison of neutral molecular markers with those from a local population at the common garden site. Geographic distance metrics included dispersal distance (the minimum distance over water between donor and experimental sites) and latitude. Model results indicate direct effects of genetic distance and latitude on performance variation among the donor sites. Standardized effect strengths indicate that performance was roughly twice as sensitive to variation in genetic distance as to latitudinal variation. Dispersal distance had an indirect influence on performance through effects on genetic distance, indicating a typical pattern of genetic isolation by distance. Latitude also had an indirect effect on genetic distance through its linear relationship with dispersal distance. Three performance indicators had significant loadings on performance alone (mean clone diameter, mean number of stems, mean number of inflorescences), while the performance indicators mean stem height and mean stem width were also influenced by latitude. We suggest that dispersal distance and latitude should provide an adequate means of predicting performance in future S. alterniflora restorations and propose a maximum sampling distance of 300 km (holding latitude constant) to avoid the sampling of inappropriate ecotypes.