Mulch Depth Research Articles

Dasometric variables that determine fuel load in oak forests in Guerrero, Mexico

Climate change and the lack of fuel management in oak forests promote favorable conditions for the occurrence of forest fires. The objective of the present research was to know the relationship of dasometric variables, terrain slope (Pe), depth of leaf litter (Ph) and depth of mulch (Pm) on the fuel load in oak forests in the Mountain region of Guerrero. The dasometric variables mean diameter (Dm), mean height (Am), number of trees ha-1 (Na) and basal área ha-1 (Ab) were evaluated according to the sampling design of the 2015 National Forest and Soil Inventory; At each sampling site, three planar intersection lines were established for sampling woody material (Ml), leaf litter (Ho) and mulch (Ma) were collected in 0.09 m2. The total fuel load ranged from 23.2 to 46.5 t ha-1 (p < 0.05), the Ma presented the highest load with 43%, followed by woody material (Ml) and leaf litter (Ho) with 31 and 26%. The total charge (Ct) showed a relationship with Ma, Ho and Ml (r = 0.81 to 0.41), Ho with Ph and Pe (r = 0.71 and -0.72). The c1h showed a relationship with Na, Ma, Pe and Dm (r = 0.72 to -0.41), the c10h showed a correlation with Ab, Pe and Na (r = 0.51 to 0.42). The dasometric variables only explain the fuel load with a diameter less than or equal to 2.5 cm.

Pine Straw Mulch Depth Modulates Soil Conditions

Mulching landscape beds is a common task for landscapers seeking to affect soil conditions and reduce weed pressure. This study investigated the effects of three pine (Pinus sp.) straw mulch depths (5, 10, and 15 cm) on soil moisture/temperature modulation during late winter/spring. No differences in soil volumetric water content were observed; however, increasing mulch depth to ≥10 cm decreased fluctuations in temperature. This research provides a better understanding of the effect of mulch depth and potential environmental benefits so that landscape contractors can determine cost-benefits of mulching applications.

Comparative analysis of fuel loads in the area affected by fire and without fire in Malinaltepec, Guerrero

Forest fires are one of the factors that contribute to climate change, among the components that form the fire triangle, fuel is theonly factor that can be manipulated. The objective of this work was to estimate the load of forest fuels in Mg ha-¹ in an area burnedin 2015 and another area without fire. For the evaluation of forest fuel, three sampling sites were established in each of the areas,the woody material was counted by delay time (1, 10, 100 and 1000 h) according to the technique of planar intersections; at the endof each line, litter (h) and mulch (m) were collected in 0.09 m². Tests were carried out to contrast the general fuel load and by typebetween ecosystems; Tukey's means comparison test was used to contrast the fuels in a given area, finally the woody material (ml),mulch (m) and litter (h) were correlated with the total load (ct), litter depth (ph) and mulch depth (ph) using Pearson correlationtests. The total fuel load was 53.10 Mg ha-¹ in the burned area, while the area without fire showed a load of 27.26 Mg ha-¹ withoutsignificant differences (p = 0.114). On the comparison of loads by delay time, the fuel of 1, 10 and 100 h showed a higher load inthe burned area, although it was not significant (p > 0.05); the analysis by component showed a higher litter load in the non-burnedarea with 12.90 Mg ha-¹ (p = 0.015) and the woody material was statistically higher in the burned area with 35.95 Mg ha-¹ (p =0.024). The correlation of variables showed an r = 0.95 between the woody material and the total load; followed by leaf litter andmulch (r = 0.80); on the contrary, the total load in the non-burned area showed a correlation with the mulch and leaf litter (r = 0.89and 0.83). The forest fire contributed to the reduction of litter and mulch but maximized the load of woody fuel.

Influence of different organic mulches on soil hydrothermal and plant growth parameters in potato crop (Solanum tuberosum L.)

Present study was conducted to investigate the effect of different mulching materials on soil hydrothermal environment and plant growth parameters for potato crop at field experimental station of National Institute of Technology, Hamirpur in the humid sub-tropical agro climate of Western Himalayas. The field experiments were conducted in a randomized complete block design with four mulching treatments; wheat straw mulch, pine needle mulch, rice straw mulch and no mulch in three replications. An increase in soil moisture retention ranging from 5.14% to 42% was observed depending upon the mulch material and depth of the soil layer in root zone. Mulching also reduced the daily maximum soil temperature up to 3.5ºC with an average temperature reduction of 1-2ºC during the period of tuber formation. Mulching produced beneficial effects on root depth, plant height, leaf area index and tuber yield. Mulching helped to bring about a yield surplus of 1.7-4.4 tonnes ha-1 over unmulched conditions and an increase in water use efficiency which varied from 13.5% in rice straw mulch to 34.9 % inwheat straw mulch.

Investigation of soil microbiome under the influence of different mulching treatments in northern highbush blueberry

Microbial communities on soil are fundamental for the long-term sustainability of agriculture ecosystems. Microbiota in soil would impact the yield and quality of blueberries since microbial communities in soil can interact with the rhizosphere of plant. This study was conducted to determine how different mulching treatments induce changes in soil microbial composition, diversity, and functional properties. A total of 150 soil samples were collected from 5 different mulch treatments (sawdust, green weed mat, sawdust topped with green weed mat, black weed mat, and sawdust topped with black weed mat) at 3 different depths (bottom, middle, and top region of 20 cm soil depth) from 2 different months (June and July 2018). A total of 8,583,839 sequencing reads and 480 operational taxonomic units (OTUs) of bacteria were identified at genus level. Eight different plant growth promoting rhizobacteria (PGPR) were detected, and the relative abundances of Bradyrhizobium, Bacillus, and Paenibacillus were more than 0.1% among all soil samples. Sampling depth and month of soil samples impacted the amount of PGPR, while there were no significant differences based on mulch type. Functional properties of bacteria were identified through PICRUSt2, which found that there is no significant difference between mulch treatment, depth, and month. The results indicated that sampling month and depth of soil impacted the relative abundance of PGPR in soil samples, but there were no significant differences of functional properties and beneficial microbial communities based on mulch type.

ОБОСОВАНИЕ ПАРАМЕТРОВ ЭЛЛИПСОВИДНОГО ИГОЛЬЧАТОГО ДИСКА ПОЧВООБРАБАТЫВАЮЩЕГО ОРУДИЯ

Due to the well-known advantages, rotary tillage implements are widely used in the cultivation of many agricultural crops. Structurally, the working units of rotary implements are located (installed) on the frame, as a rule, sequentially one after the other. This reduces the maneuverability of the tillage unit, increases the material consumption of the implement and the energy consumption of the technological operation. In the rotary tillage tool developed at Kazan State Agrarian University for pre-sowing soil cultivation, these disadvantages are eliminated by installing a spiral-screw working unit and a section of active ellipsoidal needle disks on the frame coaxially. The research was carried out in order to determine and substantiate the design parameters of the elliptical needle disk. A theoretical dependence is obtained to substantiate the angle α of inclination of the major axis of the ellipsoid disk to the axis of rotation. It was revealed that its rational value must correspond to the condition: α> 44°…62°. An expression for determining the number of needles on a disk is given. The calculation carried out with a disk diameter D= 0.4 m, an angle α= 65 °, an indicator of a kinematic mode λ= 2, a mulching depth a= 0.04 m, a ridging h= 0.004 m showed that a rational number of needles per disc k= 16. Analytically, a theoretical expression for determining the angle of inclination of the needles to the axis of rotation has been derived. The calculation performed at α= 65 ° revealed that the first needle is inclined to the axis of rotation at a minimum angle jmin= 65 °, the fifth and thirteenth needles are inclined to the axis of rotation at an angle of 90 °, the ninth needle is inclined to the axis of rotation at a maximum angle jmax= 115 °. Also obtained are theoretical dependences for determining the angle of attachment of the needles on the hub and the length of the needles along the entire perimeter of the disk. The calculation showed that each needle is fixed on the disc hub at its calculated angle of inclination, equal to 29.0°...32.6°, and the length of the needles along the perimeter of the hub varies within 0.1372 ... 0.1503 m

Increased light availability due to forestry mowing of invasive European buckthorn promotes its regeneration

The invasive shrub Rhamnus cathartica L. (common buckthorn) dominates the understory of many temperate forests of eastern North America. Common buckthorn outcompetes native understory species for light, forming monospecific stands that suppress plant and animal diversity. Removing common buckthorn is a common management priority within its invasive range. In recent years, forestry mowing has become popular in removing common buckthorn. This control method removes a midstory of common buckthorn, increasing light availability to the lower understory (which could favor buckthorn regeneration) and creating a layer of mulch on the forest floor (which could suppress buckthorn regeneration). Here we investigate whether and how increased light availability and increased ground cover (mulch) resulting from forestry mowing affects buckthorn regeneration from the seed bank. We evaluated buckthorn germination, survival, and early growth in response to a factorial combination of shading treatments and buckthorn mulch depth treatments in an oak forest in Minnesota, U.S.A. Increased light availability increased buckthorn seedling survival and growth, whereas increased mulch depth did not significantly affect the number of buckthorn establishing from seed over one growing season and winter. Thus, removing buckthorn by forestry mowing (or any other method) is likely to facilitate buckthorn reestablishment by increasing light availability at the ground.

Infiltración y escurrimiento de agua en suelos de una cuenca en el sur de México

Changes in the land use of a basin area affects the infiltration and surface water runoff directly, altering the balance of the hydrological cycle. Therefore, estimating parameters of water infiltration and runoff for each type of land use and vegetation (USV) is fundamental to differentiate the impact caused by a change of land use over the hydrical balance of a given area. The objective of this study was to estimate cumulative inf iltration (F), basic inf iltration rate (Ti), constant inf iltration rate (fc) and inf iltration decay coeff icient (k); as well as inf iltration and runoff coefficients in mountainous cloud forest (BMM), (SMSPC), pine-oak forest (BPQ), oak forest (BQ), induced grassland (PI), pine forest (BP), agricultural land in use (TC) and fallowed agricultural land (TCD). Thirty-eight simulated rain experiments were carried out at an average intensity of 100 mm h-1 with a hand-portable single nozzle rainfall simulator. The exponential model was employed to estimate fc and k and the Horton semi-empirical model to estimate Ti and F. The analysis of variance was performed by the generalized linear model (GML) to evaluate the effects of USV and texture type, and the analysis of covariance was employed to determine the effects of slope, mulch depth, organic matter % of total variability content, sand, mud and clay content, and bulk density. The exponential model fitted more than 80% of total variability (R2) at all USV. Agricultural land in use and TCD showed the lowest F and Ti and the highest k (P < 0.001), BMM exhibited the highest infiltration capacity (F) and lowest decay rate (k). The bulk density of the soil, and content of mud and organic matter were the variables positively associated to infiltration (P < 0.01).

Parametric Analysis of the Mulching Depth of Oil Palm Fronds Achieved by Tractor Operated Mulcher

Parametric Analysis of the Mulching Depth of Oil Palm Fronds Achieved by Tractor Operated Mulcher

Emergence of garden spurge (Euphorbia hirta) and large crabgrass (Digitaria sanguinalis) in response to different physical properties and depths of common mulch materials

AbstractGreenhouse and outdoor container experiments were conducted to determine garden spurge and large crabgrass emergence when seeds were placed either on top of or below three different mulch materials [pine bark (PB), hardwood (HW), or pine straw (PS)] applied at five depths (0, 1.3, 2.5, 5.1, and 10.2 cm). To elucidate mulch characteristics that contributed to weed control, photosynthetic active radiation (PAR) was recorded underneath each mulch layer, moisture retention was monitored for 24 h following irrigation, and particle size was determined using standard soil sieves. HW reduced PAR (97%) more than did PB (90%) or PS (92%) at 1.3 cm, but few or no differences were noted between mulches at greater mulch depths. HW also contained the highest percentage of small particles and consequently retained more water (29%), than PB (14%) or PS (22%) 24 h following a simulated irrigation event. Emergence of large crabgrass and garden spurge was consistently greater when seeds were placed on top of the mulch, compared to seeds placed below. Emergence of both species also tended to respond to increasing depth in a quadratic manner, indicating that once a critical level of mulch was applied (2.5 to 5 cm), further reductions in weed emergence would not be observed, at least over the short term (12 wk). PB and PS tended to provide a greater reduction in emergence of both species compared to HW. This research also indicates that larger particle materials such as PB or PS would be advantageous because of their ability to suppress weed emergence regardless of seed position.

Does helimulching after severe wildfire affect vegetation recovery in a coastal area of Northwest Spain?

Helimulching is commonly applied after high-severity wildfires in North America because of its effectiveness in reducing post-fire runoff and erosion. However, its use in other parts of the world is still very limited and information about its effects in different environments is scarce. In this study, the effects of helimulching on vegetation recovery and species composition were assessed in 70 experimental plots (80 m2 each) established in five shrubland areas in Northwest Spain affected by wildfire in summer 2013. The effects on shrub, forb, fern and grass cover, and on total vegetation cover, as well as on species richness, Shannon diversity index and heterogeneity were studied over the 2 years following the fire. The impacts of soil burn severity and mulch depth on these variables were also considered. Overall, the mulching treatment had little effect on the cover variables. Although it had a positive effect on forb cover, these species represented only a small portion of the total vegetation cover. Soil burn severity was not a significant factor in explaining the variation in the variables under study. The treatment had a low impact on species composition. In the mulched plots only three non-native species were recorded and these displayed a limited capacity to act as invasive species as they were absent at the end of the period of study. The results indicate that helimulching is a feasible soil stabilization treatment with neutral effects on vegetation cover and the composition of shrubland in coastal areas of Northwest Spain.

Mulch Type and Depth, Herbicide Formulation, and Postapplication Irrigation Volume Influence on Control of Common Landscape Weed Species

Mulch is often applied in landscape planting beds for weed control, but little research has focused specifically on mulch and preemergence (PRE) herbicide combinations. The objectives of this research were to determine the efficacy of herbicide + mulch combinations and which factors significantly affected weed control, including herbicide formulation and posttreatment irrigation volumes. Additional objectives were to determine efficacy derived from mulch or herbicides used alone under herbicide + mulch combinations and to identify differences in the additive (herbicide + mulch combinations) or singular (herbicide or mulch) effects compared with the use of herbicides or mulch only. Large crabgrass (Digitaria sanguinalis), garden spurge (Euphorbia hirta), and eclipta (Eclipta prostrata) were used as bioassay species for prodiamine, dimethenamid-P + pendimethalin, and indaziflam efficacy, respectively. The experiment consisted of a factorial treatment arrangement of two herbicide formulations (granular or spray applied), three mulch types [hardwood chips (HWs), pine bark (PB), and pine straw (PS)], two mulch depths (1 and 2 inches), and three levels of one-time, posttreatment irrigation volumes (0.5, 1, and 2 inches). Three sets of controls were used: the first set included three mulch types applied at two depths receiving only 0.5-inch irrigation volume, the second set included only two herbicide formulations and three one-time irrigation volumes, whereas the last set received no treatment (no herbicide or mulch) and only 0.5-inch irrigation volume. High levels of large crabgrass and garden spurge control (88% to 100%) were observed with all herbicide + mulch combinations evaluated at mulch depths of 1 inch or greater. When comparing mulch types, the best eclipta control was achieved with hardwood at 2 inches depth. The spray formulation of indaziflam outperformed the granular formulation in most cases when used alone or in combination with mulch. Overall, the results showed that spray formulations of prodiamine and dimethenamid-P + pendimethalin were more effective than granular formulations when applied alone, whereas indaziflam was more effective as a spray formulation when used both alone and in combination with mulch. Increasing irrigation volume was not a significant factor for any of the herbicide + mulch combinations when evaluating overall weed control.

Evaluation of Mulching Practice on the Survival and Subsequent Early Growth Performances of the Transplanted Coffee Seedlings

The global temperature has been increasing over the years due to recurrent climate change and variability, which directly or indirectly affects the agriculture sector. This has made the necessary for the farmer to get the best out of the little rainfall. Therefore, the objectives of the present study were to identify effective mulching materials and their optimum application thickness for newly transplanted coffee seedlings. The field experiment was conducted during 2015 and 2016 at Mechara Agricultural Research Center (McARC) on-station and Sakina on-farm. Coffee seedlings of Mechara-1 variety and organic mulching materials of stalk of maize and vetiver grass at 5cm and 10cm mulching depth thickness were compared with farmers' practices of using soil as mulching material and no-mulch bare soils. The experiment was laid out in RCBD with three replications. Parameters such as seedling survival rate, soil moisture content, moisture stress score, weed density and subsequent early growth performance of the seedlings were studied. The result indicated that there are statistically significant differences (p<0.05) among the treatment for most parameters studied at both locations and seasons. Vetiver grass mulches applied at 5 cm mulching thickness resulted in the highest combined over location and season percentage of coffee seedling survival rate (94.6%), soil moisture content (16.5%), the lowest moisture stress score (1.5) and the highest mean values of the different early growth measurement of coffee seedlings. However, weed species and their densities were lowest of all under coffee seedlings treated by stalk of maize mulches at 10cm mulching depth. Therefore, from these results mulching newly transplanted coffee seedlings with vetiver grass at 5cm mulching depth can be the recommended to farmers in moisture deficit areas as this practice conserved soil moisture resulting in better seedlings survival through increasing their tolerance to moisture stress.

Mulch Type and Depth Influences Control of Three Major Weed Species in Nursery Container Production

Two commonly used management practices for weed control in container plant production are hand pulling and herbicide applications. There are problems associated with these methods including crop phytotoxicity and environmental concerns associated with off-target movement of herbicides. Other nonchemical weed control methods could reduce herbicide-based environmental concerns, mitigate herbicide-resistance development, and improve the overall level of weed control in container nursery production. Readily available tree-mulch species, eastern red cedar (Juniperus virginiana), ground whole loblolly pine (Pinus taeda), chinese privet (Ligustrum sinense), and sweetgum (Liquidambar styraciflua) were harvested, chipped, and evaluated at multiple depths with and without the herbicide dimethenamid-p. Pine bark mini-nuggets were also evaluated. Mulches were applied at depths of 1, 2, and 4 inches and evaluated over three 30-day periods for their effectiveness in suppressing spotted spurge (Chamaesyce maculata), long-stalked phyllanthus (Phyllanthus tenellus), and eclipta (Eclipta prostrata). After 30 days, herbicide/mulch combinations, as well as mulch treatments alone, had reduced weed fresh weight 82% to 100% with 1 inch of mulch. By 168 days after treatment, dimethenamid-p had lost all efficacy, and mulch depth was the only factor that still had significant effects, reducing spotted spurge fresh weight by 90%, 99.5%, and 100% with depths of 1, 2, and 4 inches, respectively. The economics of mulch weed control will depend on variables such as available time, nursery layout, location, and availability of resources, equipment, among others. Regardless of variable economic parameters, data from this study reveals that any of these potential mulch species applied at a depth of at least 2 inches will provide long-term weed control in nursery container production.

Efficacy and Estimated Annual Cost of Common Weed Control Methods in Landscape Planting Beds

Organic mulch is commonly used in landscape planting beds to improve plant growth and reduce competition from weed species. Although many different mulch materials have been evaluated in landscape, forestry, or agricultural settings, there have been no previous reports concerning the maintenance costs associated with different mulch materials from a weed control perspective. Trials were conducted at two locations in Florida to estimate the annual maintenance costs associated with pine bark nuggets (bark derived from pine species not specified) and pine straw mulch [mix of longleaf pine (Pinus palustris) and slash pine (Pinus taeda) needles] with and without the use of a granular preemergence herbicide when maintained at similar depths in schilling’s holly (Ilex vomitoria ‘Schilling’s Dwarf’) shrub beds and asiatic jasmine (Trachelospermum asiaticum ‘Minima’) groundcover beds. Weed coverage and residual mulch depth were tracked over time, with maximum and minimum thresholds (20% and 2 inches, respectively) set as triggers for maintenance activities. Results showed that the addition of herbicide (trifluralin + isoxaben) had little to no impact on weeding frequency or time when plots were mulched, but did reduce hand weeding frequency and time compared with nontreated, nonmulched plots. Both mulch materials used alone reduced hand weeding frequency and time compared with herbicide-only treatments. Although results varied by bed type and location, pine bark generally provided greater weed control compared with pine straw and required fewer mulch additions and less mulch by volume. Results from this study suggests that using pine bark nuggets as mulch may result in lower maintenance costs and weed pressure compared with pine straw when both are applied and maintained at 2-inch depths.

Monilinia vaccinii-corymbosi Apothecial Development Associated With Mulch Depth and Timing of Application.

Pseudosclerotia of Monilinia vaccinii-corymbosi overwinter on the soil surface and develop apothecia in early spring, supplying primary inoculum for mummy berry disease of blueberry. Burial of pseudosclerotia in soil and incubation in the dark have previously been identified as critical factors inhibiting M. vaccinii-corymbosi apothecial development. Mulches of Douglas-fir (Pseudotsuga menziesii) sawdust at 2.5 or 5 cm depths, blueberry leaves (Vaccinium corymbosum cv. Bluetta) at a 2.5 cm depth, and a bare ground (no mulch) control were assessed for an effect on apothecial development in the spring for 2 years. Mulches were applied corresponding to pseudosclerotial overwintering stages. Loss of mulch depth was also assessed throughout the overwintering season. A 5 cm depth of Douglas-fir sawdust was associated with greater apothecial suppression in comparison with bare ground. Douglas-fir sawdust at a 2.5 cm depth varied in effectiveness, while 2.5 cm of blueberry leaves was not more effective at suppressing apothecial development than the bare ground treatment. Application timing did not affect apothecial development, but mulches lost significantly more depth when applied at the beginning of the overwintering season as compared with late winter mulches. Therefore, loss of mulch thickness due to weathering and/or decomposition may also affect apothecial development.

Effect of plastic mulch and burial depth on purple nutsedge (Cyerperus rotundus) emergence and growth

ABSTRACTCyperus rotundus L. causes high yield losses in fruiting vegetables and cucurbits in eastern and southeastern parts of Iran. Greenhouse and field experiments were conducted to investigate the effect of mulch type (1- and 2-layer black and clear low-density polyethylene (LDPE) sheets as well as a non-mulched control) and tuber burial depth (0, 2.5, 5, 10, 20, 30, 40, and 50 cm) on C. rotundus above- and belowground growth. All experiments were conducted using three different populations from Birjand, Kahnooj, and Jiroft. It was found that the greatest suppression of C. rotundus growth in all populations was observed in plots covered with 2-layer black LDPE, so that no above- or belowground growth was found with this type of LDPEs. It was also concluded that C. rotundus can emerge from tuber burial depths in the range of 30–50 cm depending on the population studied, indicating mechanical operations that bury the tubers in soil depths even as deep as 50 cm (e.g. moldboard ploughing), cannot guarantee to suppress the emergence and tuber production of this noxious weed species. Our study clearly showed that using a 2-layer black LDPE can be recommended as a promising technique for the control of C. rotundus rather than implementing a deep tillage.

Assisted lodgepole pine regeneration on reclamation sites using logging slash as both a mulch and natural seed source

In this study, we tested the efficacy of establishing lodgepole pine (Pinus contorta Dougl.) from seed using woody mulch produced from slashed tree tops from a pine harvesting site; this mulch contained the closed serotinous cones of the lodgepole pine. Mulch was spread on prepared reclamation sites at depths of 0, 1, 3, and 5 cm. Broadcast seeding of pine was also done at mulch depths of 0 and 1 cm. Mulch cover that was 1 cm thick was the preferred treatment, as it produced 17 000 seedlings·ha−1by the third year after treatment while being similar in seedling density to the 3 and 5 cm treatments. When 50 000 seeds·ha−1were added, seedling density went up more on the sites with 1 cm of mulch than the sites with no mulch. Soil temperature was lower and temperature extremes were reduced under the mulch layer compared with the control plot. The plots with 1 cm of mulch also had higher soil moisture in the mineral layer than the plots with 0 cm of mulch. A thin layer of woody mulch, therefore, provided a source of pine seed and the covering of the ground provided a more benign environment for the establishment of pine germinants.

红河干热河谷木棉种群的天然更新

PDF HTML阅读 XML下载 导出引用 引用提醒 红河干热河谷木棉种群的天然更新 DOI: 10.5846/stxb201407161446 作者: 作者单位: 西南林业大学国家林业局西南地区生物多样性保育重点实验室 昆明 650224,西南林业大学国家林业局西南地区生物多样性保育重点实验室 昆明 650224 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31260175); 云南省高校科技创新团队建设项目 Causes of difficulties with natural regeneration of a Bombax ceiba population in Hong-He dry-hot valleys (DHV) Author: Affiliation: Southwest Forestry University,Southwest Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在以干热为显著特点的干热河谷,木棉成年树生长、开花良好。但其实生苗天然更新不良,其发生过程和影响因子至今尚不明确。通过对红河干热河谷木棉种群种子扩散特点、萌发策略和影响因素研究,在分析木棉实生天然更新困难影响因子的同时,对更新幼苗的发生进行了探讨。结果表明:单株木棉成年母树平均生产果实(358±46)个,单果和单株种子数分别为(274±45)粒和(98092±2540)粒,木棉种质资源丰富。种子的扩散范围广,而田间种子损失量大(损失比例为霉变54.0%、动物取食18.2%和搬运12.0%)。自然条件下种子活力在落种后10-35 d,种子含水量为2.1%-5.9%时为最佳,落种45 d后活力显著下降。干旱条件下木棉落种萌发成苗过程是天然更新的关键环节,其间水分因子起直接作用,连续数日20%-40%的土壤含水率能促进幼苗更新。适度覆土(1-2 cm)可起到改善落种的水分环境的作用,从而促进萌发。旱季降雨少,干旱持续时间长是阻碍更新幼苗向幼树转化的瓶颈。可见,地表种子存留量低、土壤含水量低、种子自然活力保存时间短、自然和人为干扰等环节限制了木棉种群成功的实生天然更新。 Abstract:Kapok trees (Bombax ceiba) grow well and have normal flowering and seeding capacity in Hong-He dry-hot valley (DHV), which is characterized by a dry and hot climate. The valley sees small rainfall and long duration of drought during the dry season. Kapok seeds have a normal germination potential, but their natural regeneration is very poor. Young trees or seedlings are seldom observed under a mature kapok tree. The causes of the difficulties with their natural regeneration and the related factors controlling the regeneration process remain unclear. To understand the process of seedling development and the causes of problems with natural regeneration, we measured seed production per tree, seed dispersal characteristics as well as the field and indoor seed germination potential in a kapok natural population in Hong-He DHV. The results showed that each mature kapok tree produced (98092±2540) seeds on average. The mean fruit number per tree and the mean seed number per fruit were 358 ± 46 and 274 ± 45, respectively. These findings indicated that the seed source was abundant. The seeds started to disperse by flying with kapok fiber after the fruit cracking from late April to early May. Most of the seeds (82.7%) dispersed within the distance 4-22 m around the parent tree. The area 14 m away from the parent tree was the concentrated seed dispersal zone, with seed density 1005 seeds/m2. The seed rain lasted for 15 days. The losses among the seeds falling on the ground were high. Approximately 30.2% of these seeds were taken by birds, ants, and mice, and 54.0% of the seeds perished because of mildew. Field germination tests showed that the germination rate for the treatment with 2 cm surface soil mulching was 60.3%, whereas the germination rate for the treatment without soil mulching ranged from 15.0% to 38.8%. The seeds did not germinate if the soil mulching depth was 6 cm. Apparently, the seeds falling onto the bare land without soil mulching or with excessively deep soil mulching have low germination rates. Additionally, the sterilization test with different disinfection treatments demonstrated that an infection reduced the germination rate by 40.8%. The seed viability was also influenced by seed moisture conditions. The seed moisture decreased with the increasing period after seed falling up to 40 days. Seeds at 10-35 days after maturation had moisture content of 2.1%-5.9% and showed the best seed viability, but the viability declined significantly 45 days after maturation. Soil moisture of 20%-40% was favorable for seedling development. This result indicated that both seed and soil moisture directly affected seed germination and the seedling development process. The seeds showed a wide span of tolerance to temperature changes. The seeds could germinate at a temperature between 10 and 50 ℃, showing the best germination rate at 30-35 ℃. In conclusion, weak precipitation and prolonged drought during the dry season in these dry-hot valleys lead to conditions that are inhospitable to germination and growth. These conditions reduce the number of remaining seeds, lower soil moisture content, and shorten the seed viability period. Therefore, weak rainfall and a long drought seem to be the bottleneck that restricts the progression from seedlings to young trees. Soil mulching (1-2 cm) can increase the seed germination rate by improving moisture conditions. 参考文献 相似文献 引证文献

Rice Hull Mulch Affects Germination of Bittercress and Creeping Woodsorrel in Container Plant Culture

Mulches are commonly used to control weeds in container nursery crops, especially in sites where preemergence herbicides are either not labeled or potentially phytotoxic to the crop. Parboiled rice hulls have been shown to provide effective weed control when applied 1.25 to 2.5 cm deep over the container substrate surface. The objective of this research was to determine if weed seed placement, above or below the mulch layer, affects flexuous bittercress or creeping woodsorrel establishment. Seeds of both species were placed either above or below rice hull mulch layers 0, 0.6, 1.3, or 2.5 cm deep in nursery containers with a 80 pine bark: 20 sphagnum peat moss substrate. Establishment of both weeds decreased with increasing mulch depth. Establishment of both species was generally greater from beneath the mulch compared to when seed were applied above the mulch. Light penetration through varying depths of rice hulls was determined with a spectroradiometer. Photosynthetically active radiation (PAR) decreased exponentially with increasing rice hull depth, and was less than 1 μmol·m-2·s-1 beneath depths greater than 1 cm. Germination of both species was determined in Petri dishes placed beneath varying densities of shade cloth. Flexuous bittercress germination responded quadratically to decreasing light level, but still germinated (13%) in complete darkness after 3 weeks. Creeping woodsorrel germination was not affected by light level and was high (92%) after 3 weeks. The role of light exclusion by rice hulls as a mechanism for controlling buried weed seed is discussed. Water retention immediately after irrigation, and for 24 hr following irrigation, was determined for a 2.5 cm layer of rice hulls, sphagnum peat moss, and pine bark. Rice hulls retained less water, and dried more quickly than peat moss or pine bark. The volumetric water content of the rice hull layer is less than 0.20 cm·cm-1 and what has been shown necessary for plant growth. Lack of water availability in the rice hull layer is discussed as the primary mechanism of control of weed seed above the mulch layer.