基于林木病虫害防治的移动喷雾参数对雾滴穿透性影响分析

林木病虫害防治过程中,常采用皮卡搭载喷雾系统进行移动喷雾,以达到快速高效的目的。为了研究移动喷施农药过程中喷雾技术参数对雾滴穿透性的影响,本研究构建了由供液模块、喷雾压力调控和速度实时显示模块、喷头高度和角度调节模块、速度控制调节模块和防冲撞限位模块5大部分组成的移动喷雾测试系统。通过研制的移动喷雾测试开展试验分析,分别设置了3种喷施压力、4种搭载平台行驶速度、国产和进口不同的多个喷头,对仿真树靶标进行了喷雾试验,在仿真树冠层内设置8个采样点铺放卡纸来测定雾滴沉积覆盖率,采用iDASPRO雾滴沉积分析数据,以此来测试喷雾技术参数对雾滴穿透规律的影响。经过统计分析,得到影响喷头穿透效果大小的因素次序:喷雾压力>搭载平台移动速度>喷头孔径,采用Design Expert试验分析软件,建立以喷头孔径、搭载平台移动速度和喷雾压力为自变量、以雾滴覆盖率为应变量的多元非线性回归模型。结果表明:雾滴沉积量随着喷雾压力的增加呈现增加的趋势,当移动速度为最小的0.25m/s时,雾滴沉积量明显高于移动速度为0.50m/s和0.75m/s时的值,研究结果对于植保作业中移动喷雾参数确定和器械选择提供了理论依据与应用参考。     

Research Advances in Effect of Nitrogen Deposition on Forest Carbon Sequestration

Nitrogen deposition imposes important impact on the function and the stability of forest carbon sequestration.This paper reviewed the research advances in the increasing response of forest carbon sequestration to nitiogen deposition, described the application prospects of stable carbon isotope technique in the research field.And finally this paper pointed out that,on the condition that nitrogen deposition rises,on the allocation of forest photosynthetic products and the change in soil carbon turnover rate are the two hotspots in the future carbon cycling research.     

Effects of elevated nitrogen deposition on soil microbial biomass carbon in major subtropical forests of southern China

2003

Wallenstein M D.McNulty S.Fernandez I J.Boggs J Schlesinger W H Nitrogen fertilization decreases forest soil fungal and bacterial biomass in three long-term experiments [其它论文] 2006

Wang X F.Li S Y.Bai K J.Kuang T Y Influence of doubled CO2 on plant growth and soil microbial biomass C and N 1998(12)

Xue J H.Mo J M.Li J.Li D J The short-term response of soil microorganism number to simulated nitrogen deposition 2007(02)

Yao W H.Yu Z Y The nutrient content of throughfall inside the artificial forests on downland 1995

Yi Z G.Yi W M.Zhou L X.Wang X M Soil microbial biomass of the main forests in Dinghushan Biosphere Reserve 2005(05)

Zhou G Y.Yan J H The influence of region atmospheric precipitation characteristics and its element inputs on the existence and development of Dinghushan forest ecosystems [其它论文] -Acta Ecologica Sinica2001

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Nitrogen leaching in response to increased nitrogen inputs in subtropical monsoon forests in southern China

Dissolved inorganic nitrogen (DIN) (as ammonium nitrate) was applied monthly onto the forest floor of one old-growth forest (>400 years old, at levels of 50, 100 and 150 kg N ha⁻¹ yr⁻¹) and two young forests (both about 70 years old, at levels of 50 and 100 kg N ha⁻¹ yr⁻¹) over 3 years (2004–2006), to investigate how nitrogen (N) input influenced N leaching output, and if there were differences in N retention between the old-growth and the young forests in the subtropical monsoon region of southern China. The ambient throughfall inputs were 23–27 kg N ha⁻¹ yr⁻¹ in the young forests and 29–35 kg N ha⁻¹ yr⁻¹ in the old-growth forest. In the control plots without experimental N addition, a net N retention was observed in the young forests (on average 6–11 kg N ha⁻¹ yr⁻¹), but a net N loss occurred in the old-growth forest (−13 kg N ha⁻¹ yr⁻¹). Experimental N addition immediately increased DIN leaching in all three forests, with 25–66% of added N leached over the 3-year experiment. At the lowest level of N addition (50 kg N ha⁻¹ yr⁻¹), the percentage N loss was higher in the old-growth forest (66% of added N) than in the two young forests (38% and 26%). However, at higher levels of N addition (100 and 150 kg N ha⁻¹ yr⁻¹), the old-growth forest exhibited similar N losses (25–43%) to those in the young forests (28–43%). These results indicate that N retention is largely determined by the forest successional stages and the levels of N addition. Compared to most temperate forests studied in Europe and North America, N leaching loss in these seasonal monsoon subtropical forests occurred mainly in the rainy growing season, with measured N loss in leaching substantially higher under both ambient deposition and experimental N additions.     

Overstory vegetation influence nitrogen and dissolved organic carbon flux from the atmosphere to the forest floor: Boreal Plain,Canada

Nitrate, ammonium, total dissolved nitrogen (TDN), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and flux were measured for one year in bulk deposition and throughfall from three stand types (upland deciduous, upland conifer and wetland conifer) on the Boreal Plain, Canada. Annual (November 2006 to October 2007 water year) flux rates in bulk deposition were 80, 216, 114 and 410 mg N m⁻² for nitrate, ammonium, DON and TDN, respectively, and 3.5 g C m⁻² for DOC. The nitrate and ammonium flux in throughfall were approximately 50% of the flux in bulk deposition, while TDN flux in throughfall was 60–74% of the flux in bulk deposition. The DOC flux in throughfall was approximately 2 times greater than DOC flux in bulk deposition, while there was no detectable difference in DON flux. The forest canopy generally had the most impact on throughfall chemistry during the active growing season as compared with the dormant season, although DOC concentrations in throughfall of deciduous stands was highest during autumn. For the upland stands, TDN flow-weighted mean concentrations in the snowpack were not detectably different from the concentrations in throughfall and bulk deposition throughout the rest of the year. However, ammonium concentrations were lower and DON concentrations were higher in the snowpack than in either throughfall or bulk deposition for the other seasons, suggesting some transformation of ammonium to DON within the snowpack.     

Ozone,Acid Deposition,and Mycorrhization Effects on Loblolly Pine and White Oak

Abstract

Above- and below-ground responses of juvenile loblolly pine (Pinus taedaL.) and white oak (Quercus albaL.) to tropospheric ozone (0.0, 0.06, and 0.12 μL L^-1 O₃), acid precipitation (pH 4.8, 4.2, and 3.6), and induced ectomycorrhizal colonization (Pisolithus tinctorius [Pers.] Coker & Couch vs. natural mycobiont), alone and in combination, were examined. After 30 weeks, the filtered air treatment (ozone 0.0) reduced foliar injury but also produced smaller stem diameters, lower total foliage and total shoot dry weights, decreased needle density, and shorter root systems in inoculated pine, growth responses not found in uninoculated pine. Height growth of inoculated oak was increased by the filtered air treatment while leaf density was reduced by 0.12 μL L^-1 O₃, results also not found in uninoculated oak. Ectomy-corrhizal colonization percentages in pine decreased with increasing O₃ concentration regardless of mycorrhizal treatment, and the filtered air treatment produced the highest infection percentages in inoculated oak as well. Rains of pH 4.2 stimulated height growth in inoculated pine while diameter decreased in inoculated oak but increased in uninoculat-ed oak with declining pH. Also, pH 4.2 rainfall increased root weight in inoculated oak while that of pH 4.8 reduced foliar injury but also shoot weight in oak regardless of mycorrhizal treatment. Generally, the my-corrhization response to increasing rainfall acidity was reduced colonization. Independent of the other treatments, inoculation produced a substantial increase in above- and below-ground growth of both pine and oak, and also increased foliage density but reduced specific root length in each species. Overall, these results indicate that the growth responses to O₃ and acid deposition of loblolly pine and white oak are strongly influenced by mycorrhization, but that the magnitude of these responses is exceeded by those to mycorrhization alone. However, the propensity revealed here for both O₃ and acid precipitation to suppress mycorrhizal colonization in these two species may indicate the potential for a gradual reduction in long-term forest productivity in the southeastern United States.     

Nutrient fluxes in rainfall,throughfall and stemflow in Eucalyptus stands on the Zululand coastal plain,South Africa

Atmospheric deposition was assessed at two sites over a four-year period in post-canopy-closure (mature) Eucalyptus stands in the northern Dukuduku and southern KwaMbonambi commercial plantation forestry areas of Zululand, South Africa. The aim of this study was to determine the magnitude and relevance of nutrient addition with rainfall, throughfall and stemflow to commercial forestry in this region. Canopy cation exchange was used with rainfall and canopy drainage to derive wet, dry and total atmospheric deposition. Nutrient concentrations measured in the rainfall, throughfall and stemflow varied widely throughout the study period, and between sources and sites. Rainfall was slightly acidic at both sides, but became less acidic upon passing through the tree canopies. Canopy exchange and collection of dry deposition resulted in increased cation concentrations under the tree canopy, while the canopy generally absorbed nitrogen (N), from the rainfall, reducing the below canopy concentrations. Atmospheric deposition was shown to be responsible for large quantities of nutrients added to the eucalypt stands at each site. Annualised deposition averaged across all years at each site amounted to N, calcium, magnesium, and potassium (K) fluxes of 11.0, 6.0, 2.7 and 10.2 kg ha^?1 y^?1 at Dukuduku and 10, 10.6, 7.5 and 18.8 kg ha^?1 y^?1 at KwaMbonambi, respectively. Organic N fluxes contributed a further 8.1 kg ha^?1 y^?1 at Dukuduku and 7.1 kg ha^?1 y^?1 at KwaMbonambi to the total N deposition. Although K deposition values were high, additions of all other nutrients, although also high, were within the ranges reported in local and international research. Over the course of a full rotation, the atmospheric deposition levels recorded at these sites may have potential to supply a large proportion of the nutrients that are lost during stem-wood harvesting. This study adds value to understanding of nutritional sustainability of fast-growing plantation forests, demonstrating the importance of atmospheric deposition as a nutrient addition source to plantation-grown eucalypts along the Zululand coastal plain.     

Effect of nitrogen addition on DOC leaching and chemical exchanges on canopy leaves in Guangdong Province,China

The impact of nitrogen(N)deposition on dissolved organic carbon(DOC)fractions in throughfall is not well understood.We performed a laboratory experiment and compared DOC leaching from canopy leaves after dipping leaves in pure water(control)and NH4NO3 solution(N-treatment)for 18 h.Net changes of DOC,NH4^+,NO3^-,SO4^2-,K^+,Mg^2+,Ca^2+and H^+contents after dipping leaves were determined by comparing solutions with and without leaves.We recorded no differences of DOC leaching between control and N-treatment,implying that N deposition had minor impacts on canopy DOC production.This confirmed that previous experiments testing the effects of N addition on DOC dynamics without considering the effects of the canopy reaction successfully described the real situation.We also confirmed the previously-reported canopy exchange process in spite of a high background N deposition at our study site.N-treatment significantly increased base cation leaching,especially K^+,and the increase was positively correlated with foliar NH4?retention.Net leaching of H^+and SO4^2-was not affected by the N-treatment.     

Root parameters of forest trees as sensitive indicators of acidifying pollutants: a review of research of Japanese forest trees

The root parameters of forest trees can be indicators of a changing environment. We summarize the results of root studies with regard to the effects of acidifying pollutants, especially soil acidification and aluminum toxicity, on various root parameters of Japanese forest trees under experimentally controlled conditions. All root parameters such as biomass, morphology, nutritional status, and physiology can be regarded as indicators, because, under laboratory conditions, root responses occur prior to the responses in the aboveground parts. However, considering the conditions of forest sites, the nutritional status and physiological changes are better indicators of soil acidification and Al stress than the biomass and morphological response. The currently available data suggest that the most important indicator is the Ca/Al molar ratio in roots of Japanese tree species. In order to predict and detect the initial effects of soil acidification, we postulate that the specific root response to the Ca/Al molar ratio of tree roots should be considered as a parameter for use in long-term forest monitoring sites.     

New sampler for dry deposition in forest canopy

A new type of sampler for dry deposition in a forest canopy was designed and tested to confirm its usefulness. The new sampler is made of Teflon chips packed in a nylon net, and tied on a rod like a branch in the canopy. The validity and characteristics of the new sampler were checked by comparing it with the conventional bucket sampler and the foliar extraction method using hinoki (Chamaecyparis obtusa) trees. The comparison between the deposited amounts on the dummy branch and those on the bucket indicates that the dummy could trap gaseous matter more effective than the bucket. From a comparison with the foliar extracting method, it is concluded that the trapping of particulate matter by the new dummy branch is comparable to that of natural needle leaves. However, its efficiency for gaseous matter is relatively small. This disadvantage should be improved by applying other materials to the dummy. Moreover, it is found that the uptake of gas especially SO₂ through the stomata is an important point in the discussion about dry deposition. To evaluate the amounts of dry deposition in the forest canopy more precisely, combination with the additional method should be useful. This study was supported in part by a grant-in-aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan.