松褐天牛成虫补充营养特性研究

１９９７－１９９８年浙江省杭州市和岱县进行的松褐天牛成虫补充营养特性研究表明：松褐天牛成虫主要取食１年生树枝，室内测定雌成虫取食１年生树枝面积占总面积的３６．５８％，雄成虫占３８．９９％，林间测定点２６．３４％，成虫羽化后２０天以内的取食量最大。伐倒松材线虫病致枯萎的松树，统计天牛取食痕和取食面积在树冠上的分布显示，松褐天牛更多选择树冠下部１年生的树枝取食、取食痕和取食面积分别占５０．４２％和５１．０６％。     

板栗主要病虫害及防治方法

一、铜绿金龟子以成虫大量取食叶片,咬断花柄,对新造板栗幼林危害最大.成虫椭圆形,体长16～19毫米,体背面铜绿色,有光泽,腹面黄褐色,密生细毛.一年发生1代,以3龄幼虫在土中越冬.次年5月上旬成虫开始羽化,6月至7月上旬为羽化盛期.成虫具强趋光性,具假死性和群集危害的习性,白天潜伏,傍晚时成群飞至树上整夜取食,次晨飞离树冠潜伏.     

松墨天牛成虫咬筑刻槽习性及对寄主的危害

2001—2003年6—8月对南岳景区松墨天牛成虫的取食、产卵、咬刻槽等习性进行了观察研究,结果表明,松墨天牛成虫除取食危害外,在健康松树上咬筑刻槽也会对寄主造成危害。在华山松枯立木、衰弱木和健康木上,无卵刻槽的比率分别为14.54%、44.09%和84.19%。大量的无卵刻槽导致健康松树树势衰弱,引起更多的同种成虫前来取食危害。因此,在健康松树上咬筑刻槽是松墨天牛成虫的另一种危害方式。     

松墨天牛取食为害与松树枯死关系的研究

笔者通过室内外饲养观察,初步掌握了松墨天牛成、幼虫的取食习性;阐明了松墨天牛成虫取食与松树生理衰弱、幼虫钻蛀与松树枯死之间的关系;同时还研究了松墨天牛幼虫与其它蛀干害虫之间的关系;对成虫产卵习性和幼虫种群分布规律也进行了探讨。笔者认为,松墨天牛成、幼虫取食是造成我国松树枯死的主要原因之一。为防止松树的大面积死亡,必须密切注意松墨天牛成虫种群数量的增长。     

柽柳条叶甲生物学特性研究

柽柳条叶甲1a发生2代,以成虫在靠近树干基部的枯枝落叶下或土壤缝隙中越冬,翌年4月下旬开始活动,5月上旬开始取食危害并交尾产卵,5月中旬幼虫开始取食危害,老熟幼虫入土化蛹。第1代成虫于6月上旬开始出现,7月下旬出现第2代成虫。成虫、幼虫均取食危害。     

马尾松抗松毛虫植株的抗性机制研究

本文研究了广西玉林地区、林科所1959年种植的马尾松抗虫11号植株的抗性机制。通过用抗11号松树对马尾松毛虫成虫产卵选择性试验和幼虫饲养试验。发现抗11号松树对成虫具有拒产卵性,对幼虫具有拒取食性。用抗11号松树针叶饲养的幼虫,出现发育迟缓,死亡率高,蛹重减轻等现象。本研究证明了抗11号松树对马尾松毛虫具有抗选择性和抗生性。抗虫性的主要原因是针叶内含物起了变化,产生拒成虫产卵及幼虫取食并致令生成营养屏障。     

林木幼苗期采用诱杀法消灭黑绒金龟子

黑绒金龟子属鞘翅目金龟子神,又叫东方金龟子(俗名缎子马褂)。形态及习性。成虫长8～9mm,卵圆形,黑色或红褐色,具光泽,被黑色绒毛。一年一代,成虫在土壤中越冬,四月中、下旬出土,五月为为害盛期。产卵于植物根际表土中,六月中旬孵化出幼虫,八月中旬在土中化蛹,蛹期10天左右。羽化成虫不出土,即准备在土中越冬。成虫翌春出土活动,夜间和     

草履蚧的发生与防治

草履蚧每年1代,1月下旬越冬,卵在0℃以上就可孵化.初龄若虫2月中旬上树后,定居在1年生枝条上芽眼旁、叶痕处或1～2年生枝条交界处吸取树液危害.2龄若虫4月上旬出现,3龄若虫4月中旬出现.4月底雌雄成虫交尾后,雄虫死去,雌虫减少取食,下树潜入土中或老树皮产卵30～50粒,以卵越冬.不同时期的防治措施如下:     

补充营养材料对松褐天牛成虫存活期的影响

2000－2001年对马尾松不同龄级枝条及混合枝条饲养松褐天牛成虫的存活期及取食情况进行了研究。结果表明,不同龄级枝条对松褐天牛成虫存活期产生显著影响,混合枝条饲养平均存活期显著长于2年生枝条及3年生枝条饲养,而与当年生枝条饲养无显著差异。存活期的差异与取食密切相关,当年生枝条饲养具有最大的日均取食量,并极显著地大于2年生枝条饲养和3年生枝条饲养的相应值。混合枝条和单龄级枝条饲养日均取食量均无显著差异。混合枝条饲养处理当年生枝条被食面积占取食总面积的55％以上,3年生枝所占比例不足20％。研究显示松褐天牛自然状态下从不同级枝条中获取所需物质,以当年生枝条为主;无选择单龄枝饲养时通过增加取食来尽可能满足物质需要。     

大灰象的生物学特性及防治方法的研究

大灰象Sympiezomias velatus（Chevrolat）食性很杂,在宁夏固原市六盘山林区苗圃地主要危害青海云杉幼树,在该地区2年发生1代,6月上旬幼虫孵出后取食须根及根皮,9月下旬幼虫做土室越冬,翌年4月上旬春暖后继续取食,至6月上旬开始化蛹,7月中旬羽化为成虫,并在原处越冬,4月中、下旬越冬成虫开始出土活动,群集取食苗眼和幼嫩的针叶,并进行交尾,5月下旬成虫在地下土壤中产卵.本次研究在摸清了大灰象生物学特性的基础上,最后结合大量防治试验结果提出了防治方法.     

Short- and long-term effects of thinning and prescribed fire on carbon stocks in ponderosa pine stands in northern Arizona

Euro-American logging practices, intensive grazing, and fire suppression have increased the amount of carbon that is stored in ponderosa pine (Pinus ponderosa Dougl. Ex Laws) forests in the southwestern United States. Current stand conditions leave these forests prone to high-intensity wildfire, which releases a pulse of carbon emissions and shifts carbon storage from live trees to standing dead trees and woody debris. Thinning and prescribed burning are commonly used to reduce the risk of intense wildfire, but also reduce on-site carbon stocks and release carbon to the atmosphere. This study quantified the impact of thinning on the carbon budgets of five ponderosa pine stands in northern Arizona, including the fossil fuels consumed during logging operations. We used the pre- and post-treatment data on carbon stocks and the Fire and Fuels Extension to the Forest Vegetation Simulator (FEE-FVS) to simulate the long-term effects of intense wildfire, thinning, and repeated prescribed burning on stand carbon storage.The mean total pre-treatment carbon stock, including above-ground live and dead trees, below-ground live and dead trees, and surface fuels across five sites was 74.58 Mg C ha⁻¹ and the post-treatment mean was 50.65 Mg C ha⁻¹ in the first post-treatment year. The mean total carbon release from slash burning, fossil fuels, and logs removed was 21.92 Mg C ha⁻¹. FEE-FVS simulations showed that thinning increased the mean canopy base height, decreased the mean crown bulk density, and increased the mean crowning index, and thus reduced the risk of high-intensity wildfire at all sites. Untreated stands that incurred wildfire once within the next 100 years or once within the next 50 years had greater mean net carbon storage after 100 years compared to treated stands that experienced prescribed fire every 10 years or every 20 years. Treated stands released greater amounts of carbon overall due to repeated prescribed fires, slash burning, and 100% of harvested logs being counted as carbon emissions because they were used for short-lived products. However, after 100 years treated stands stored more carbon in live trees and less carbon in dead trees and surface fuels than untreated stands burned by intense wildfire. The long-term net carbon storage of treated stands was similar or greater than untreated wildfire-burned stands only when a distinction was made between carbon stored in live and dead trees, carbon in logs was stored in long-lived products, and energy in logging slash substituted for fossil fuels.     

Do partial cross sections from live trees for fire history analysis result in higher mortality 2 years after sampling?

Although partial cross sections from live trees have been utilized in the development of fire history studies, few efforts have been made to examine the effects of this method on the individual trees that were sampled. We examined 115 red pine (Pinus resinosa Ait.), eastern white pine (Pinus strobus L.), and jack pine (Pinus banksiana Lamb.) trees from which partial cross sections had been removed 2 years earlier, and 209 similarly sized neighboring red pine and eastern white pine trees. Two years following the removal of partial cross sections, 22 sampled trees (19%) had died. When compared with neighboring trees, removing a partial cross section did not appear to increase the mortality rate for a given tree (t-test; P = 0.150). However, when we compared the characteristics of the trees with partial cross sections removed, we did observe some trends; i.e., those trees that died were primarily killed by wind-induced breakage at the level of the partial cross section. Almost all stems where partial cross sections were collected from a catface edge or had >30% of the total area removed were more susceptible to stem breakage and experienced an increased likelihood of mortality. While these results suggest that the collection of partial cross sections from live trees may be an effective method for fire-history sampling, the negative impacts of the sampling on individual trees may be reduced by ensuring that samples are collected from the center, rather than the catface edge, and <25% of the total stem area is removed.     

Stand characteristics and downed woody debris accumulations associated with a mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in Colorado

Lodgepole pine (Pinus contorta Dougl. ex Loud.)-dominated ecosystems in north-central Colorado are undergoing rapid and drastic changes associated with overstory tree mortality from a current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak. To characterize stand characteristics and downed woody debris loads during the first 7 years of the outbreak, 221 plots (0.02 ha) were randomly established in infested and uninfested stands distributed across the Arapaho National Forest, Colorado. Mountain pine beetle initially attacked stands with higher lodgepole pine basal area, and lower density and basal area of Engelmann spruce (Picea engelmannii [Parry]), and subalpine fir (Abies lasiocarpa (Hook.) Nutt. var. lasiocarpa) compared to uninfested plots. Mountain pine beetle-affected stands had reduced total and lodgepole pine stocking and quadratic mean diameter. The density and basal area of live overstory lodgepole declined by 62% and 71% in infested plots, respectively. The mean diameter of live lodgepole pine was 53% lower than pre-outbreak in infested plots. Downed woody debris loads did not differ between uninfested plots and plots currently infested at the time of sampling to 3 or 4–7 years after initial infestation, but the projected downed coarse wood accumulations when 80% of the mountain pine beetle-killed trees fall indicated a fourfold increase. Depth of the litter layer and maximum height of grass and herbaceous vegetation were greater 4–7 years after initial infestation compared to uninfested plots, though understory plant percent cover was not different. Seedling and sapling density of all species combined was higher in uninfested plots but there was no difference between infested and uninfested plots for lodgepole pine alone. For trees ≥2.5 cm in diameter at breast height, the density of live lodgepole pine trees in mountain pine beetle-affected stands was higher than Engelmann spruce, subalpine fir, and aspen, (Populus tremuloides Michx.), in diameter classes comprised of trees from 2.5 cm to 30 cm in diameter, suggesting that lodgepole pine will remain as a dominant overstory tree after the bark beetle outbreak.     

Influence of fire intensity on structure and composition of jack pine stands in the boreal forest of Quebec: Live trees,understory vegetation and dead wood dynamics

North American jack pine (Pinus banksiana Lamb.) stands are generally characterized by an even-aged structure resulting from high intensity fires (HIF). However, non-lethal fires of moderate intensity (MIF), which leave behind surviving trees, have also been reported. The objectives of this study were two-fold: (1) assess the concurrent dynamics of live trees, understory vegetation and different types of coarse woody debris (CWD) during succession after HIF; and (2) document how MIF affects stand structure component dynamics compared to HIF. Stands affected by both HIF and MIF were selected. Tree characteristics and age structure, understory biomass, and CWD volume were assessed. Our results suggest that the structural succession of jack pine stands following HIF comprises three stages: young stands (<48 years), premature and mature stands (58–100 years) and old stands (>118 years). Canopy openness and jack pine density significantly decreased with time since HIF, while black spruce density and CWD volume significantly increased. The highest structural diversity was measured in the premature and mature stands. Compared to HIF, MIF increased mean jack pine basal area, decreased average stand density, delayed the replacement of jack pine by black spruce replacement in the canopy, decreased CWD volume, and significantly increased bryophytes mass. MIF increased the diversity of live trees and generally decreased CWD structural diversity. The study confirms the diversity of natural disturbance magnitude and successional processes thereby initiated. Thereafter, it appeared to be relevant for adjustment of disturbance emulating forest-management systems.     

The persistence and function of living roots on lodgepole pine snags and stumps grafted to living trees

In Alberta, Canada, pairs of grafted lodgepole pine trees were selected to study the longevity and location of live roots of snags that were grafted to living trees, to determine the impact of these live residual roots on the diameter growth of the living tree. In a second study, dense groups of grafted trees were manually thinned and one leave tree was left to grow for two growing seasons. For both studies, roots were excavated. Results indicate that more live roots were maintained on snags connected to living trees with a large graft and that roots located within 90° of the root grafted to the live tree persisted longer. Also, tree ring index in the living trees significantly increased following manual thinning, but was unaffected when the grafted partner died naturally. Grafts with large phloem connections maintained a higher number of live roots on snags, than grafts with small connections.     

Natural Variation in Seed Characteristics of Eastern White Pine (Pinus strobus L.)

Natural variation in seed characteristics of eastern white pine (Pinus strobus L.) trees and its relationship with the size, form, and crown class of parent trees was examined in second-growth, white pine mixedwood stands in Ontario. Cones were collected prior to and following partial harvesting of two stands during 2 years of above-average seed production. Fully enlarged seed extracted from mature cones was X-rayed to determine seed yield per cone, the percentage of sound, partially filled, and empty seed, and the sound seed mass for each tree. Variation in seed yield per cone, the proportion of sound, partially filled, and empty seed, and seed mass was much greater among individuals than between stands or seed years. The strength and significance of the relationship of seed mass with sound seed yield differed with stand and seed year. In uncut stands, seed mass was higher for trees with dominant crown class, larger live crown ratios, and smaller height to diameter ratios, suggesting tree vigour and microsite quality influence seed mass. Proportion of partially filled seeds was significantly reduced in both stands in the second year likely due to increased growing degree days during female gametophyte development. The implications of these results to natural and artificial regeneration of white pine are discussed.     

Effects of Mechanized Thinning and Prescription Fire on Stand Structure,Live Crown,and Mortality in Jeffrey Pine

ABSTRACT

Forest thinning, using cut-to-length and whole-tree harvesting systems with subsequent underburning were assessed for their influence on stand structure, health, and fire resilience in uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf). Stand attributes, derived from measuring trees ≥ 10.2 cm diameter at breast height (DBH), were collected from permanent plots. Trees were divided into three size classes that generally corresponded to dominant/codominant, intermediate, and suppressed crown classes. Comparisons of post- to pre-burning mortality revealed significant thinning and fire main treatment effects as well as significant interaction between these two treatments in the two larger size classes. Mortality increased by 250% in the intermediate crown class within the burned stand portion of the whole-tree treatment, whereas among dominant/codominant trees mortality rose by 160% in the burned cut-to-length treatment combination. Pre- to post-burning shifts in live crown, expressed as a percentage of total tree height, were significantly influenced by both thinning and fire main treatments in the two larger size classes, while the interaction of these treatments was also significant among the largest trees. Within both of these size classes, decreases in live crown percentage were greatest in the burned portion of the unthinned treatment, where intermediate crown class trees lost over 20% of their crowns, while reductions in dominant/codominant trees averaged nearly 25%. The second highest losses for both size classes occurred within the burned cut-to-length treatment. In the smallest trees, mortality rose sharply and live crown decreased substantially after burning in both thinning treatments and in the unthinned control. Within the two larger size classes, preburn live crown size was negatively correlated with changes in crown size subsequent to underburning while DBH was negatively correlated with postburning changes in mortality, but only in intermediate crown class trees. These results present land managers with outcomes of differing management practices presently being evaluated for their potential to enhance forest health and reduce wildfire risk in the Sierra Nevada and similar dry forest regions.     

Effect of natural root grafting on growth response of jack pine (Pinus banksiana) after commercial thinning

Commercial thinning is a silvicultural treatment used to increase the merchantable yield of residual trees. Growth response to thinning, however, is highly variable and discrepancies between studies remain largely unexplained. The objective of this study was to demonstrate the effect of natural root grafting on growth response after thinning. We excavated root systems of jack pine (Pinus banksiana) in five naturally regenerated stands, in which three had been commercially thinned 6 and 9 years earlier. Radial growth before and after thinning was examined using dendrochronological techniques. Thinning increased radial growth of trees, however growth increments were significantly less for trees that had root grafts with removed trees, while growth of grafted trees was better in unthinned stands. Furthermore, radial growth response of trees grafted to removed trees was smaller than that of non-grafted trees 4 years and more post-thinning. On average, non-grafted stumps survived less than 1 year (0.4 year), while grafted stumps lived 2.0 years after the stem was removed. Differences in growth response to thinning between grafted and non-grafted trees thus appear to be linked to the support of roots and stumps of removed trees by live residual trees.     

Comparison of stand dynamics after dieback caused by pine wilt disease among pine forests with different management regimes in western Japan

In pine forests damaged by pine wilt disease, in western Japan, the effect of protection regimes of pine trees on the stand dynamics were examined in the following four stands: (1) lightly damaged stand (age 30–40 years) with no procedure in operation for protecting pine trees; (2) severely damaged stand (age 30–40 years) with no procedure in place for protecting pine trees; (3) severely damaged stand (age 50 years) with a selective cutting of infected trees; (4) severely damaged stand (age 30–40 years) with a selective cutting of infected trees. All the stands had been abandoned before the pine wilt disease damage. The understory structure of the severely damaged stand with no protection procedure was similar to that of the lightly damaged stand. Frequent invasion by tree species and acceleration in the growth of understory trees occurred after the dieback in the selective cutting stand. These results suggest that a deficiency in the canopy layer caused by the dieback resulted in low disturbance intensity in the early stages after the dieback, but the selective cutting increased the intensity by the reduction in the understory as well as the canopy layer. The intensity of the disturbance in the selective cutting stands was larger in the younger stand because it had a higher density of selectively cut pine trees. The different stand structure of pine forests occurred after the dieback because the intensity of the disturbance varied as a result of the selective cutting operation and the stand age.     

Influence of herbicides and felling,fertilization, and prescribed fire on longleaf pine establishment and growth through six growing seasons

Recovery of longleaf pine (Pinus palustris P. Mill.) is necessary to arrest the decline of many associated plants and animals, and the establishment of longleaf pine on much of its original range requires artificial regeneration and diligence. In central Louisiana, USA, two fertilization levels (No [NF] or Yes [F-36 kg/ha N and 40 kg/ha P]) in combination with three vegetation treatments (check, two prescribed fires [PF], or multi-year vegetation control by herbicidal and mechanical means [IVM]) were applied to container-grown longleaf pine plantings in two studies. In Study 1 (grass dominated), 6-year-old longleaf pine survival was 52% on the F–checks, 78% on the F–PF plots, and averaged 93% on the other four treatment combinations. Longleaf pine trees on the IVM plots (3.4 m) were significantly taller than on the other two vegetation treatments, and trees on the PF plots (1.8 m) were taller than trees on the check plots (1.2 m). In Study 2 (brush dominated), survival averaged 65% across the six-treatment combinations after 6 years. The longleaf pine trees were 4.7 m tall on the IVM plots and averaged 3.9 m tall on the check and PF plots. Fertilization increased P concentrations in the soil and longleaf pine foliage, while fertilization did not significantly affect longleaf pine height growth. Native fertility was not apparently limiting longleaf pine development contrary to prior research recommendations for these soils. In both studies, the IVM treatment reduced early herbaceous competition and the number and height of arborescent plants. The PF treatment reduced arborescent plant height on the grassy site where fires were more intense than on the brushy site.