When the ground cover brings guests: is <Emphasis Type="Italic">Anaphothrips obscurus</Emphasis> a friend or a foe for the biological control of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> in clementines?

Biological control of Tetranychus urticae Koch (Acari: Tetranychidae), a key pest of clementines, can be improved in this crop with the establishment of a ground cover of Festuca arundinacea Schreber (Poaceae). This cover houses an abundant and diverse community of predatory Phytoseiidae mites including Euseius stipulatus (Athias-Henriot), Neoseiulus barkeri Hughes, Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot and a dense population of the grass thrips Anaphothrips obscurus Müller (Thysanoptera: Thripidae) throughout the year. The aim of this study was to determine whether the presence of this thrips species could be related to the improvement in the biological control of T. urticae. Therefore, the capacity of the abovementioned phytoseiids to feed and reproduce on A. obscurus and their feeding preferences when T. urticae and A. obscurus were simultaneously offered, were analyzed. The results show that E. stipulatus, N. barkeri and N. californicus have a type II functional response when offered A. obscurus nymphs, whereas P. persimilis barely feeds on this thrips species. Furthermore, N. barkeri and N. californicus can reproduce feeding only on thrips. Regarding prey preference, the Tetranychus spp.-specialist P. persimilis preferably preyed on T. urticae, the generalists N. barkeri and E. stipulatus preferred A. obscurus, and the selective predator of tetranychid mites N. californicus showed no preference. Therefore, we hypothesize that the enhanced biological control of T. urticae observed could be related to A. obscurus becoming an alternative prey for non-specialist phytoseiids, without altering the control exerted by the T. urticae-specialist P. persimilis and likely reducing intraguild predation.     

Is root nutrient uptake a modular function? A test using <Emphasis Type="Italic">Solidago canadensis</Emphasis>

Plant roots have been recognized to be modular, and a third order root cluster has been proposed to be the basic root module unit based upon the life cycle. This experiment examines root modularity of the nutrient-uptake function using stable isotope ¹⁵N. Solidago canadensis root clusters of second or third orders—from the same third or fourth order roots, respectively—were treated with ¹⁵NH ₄ ¹⁵ NO₃, NH₄NO₃, and de-ionized water for 15 and 180 min. The δ¹⁵N values of the root clusters were then analyzed and compared. The δ¹⁵N values of ¹⁵N-treated root clusters of both second and third orders were hundreds of times higher than that of the ¹⁵N untreated root clusters. However, the differences of the δ¹⁵N values among ¹⁵N untreated root clusters (though expressed some significant variations), did not indicate the ¹⁵N shared by the sister root clusters came from a common higher-order root. These results demonstrated functional modularity of root nutrient uptake, revealed a second order root, perhaps even a first order root to be a base module unit in terms of root nutrient uptake. The results also suggested that the concept of root modularity is function-specific. This experiment further revealed the importance of treatment timing in stabilizing the internal ¹⁵N/¹⁴N ratio in roots and avoiding top-down transportation of ¹⁵N back into roots to secure unbiased measurements.     

Can a natural experiment be used as a tool to design partial cutting regimes? The decline of <Emphasis Type="Italic">Austrocedrus chilensis</Emphasis> forests,an example

The forests of Austrocedrus chilensis in Argentina suffer mortality from what is locally known as ‘mal del ciprés’. This disturbance usually appears as aggregations of dead trees of varying sizes. The mortality process seems unpredictable, and regeneration establishment is variable under these conditions. The highly variable mortality rates results in a natural experiment that allows the correlation of overstory mortality with regeneration rate. This correlation should then make it possible to estimate the regeneration success which would follow after different levels of partial cutting, allowing the purposeful direction of the regeneration process. We collected data from eight Austrocedrus chilensis-dominated stands and reconstructed overstory mortality over time and correlated it to the regeneration recruitment. Mortality showed two patterns: increasing ‘continuous’ mortality over time, and ‘pulses’ of important basal area loss in short periods. Overstory mortality had an effect on the recruitment and composition of the regeneration by allowing different species establishment depending on the degree of mortality. By quantifying mortality basal area and recruitment over time, we calculated estimates that can provide partial cutting guidance. Partial cuttings would then allow the purposeful direction of the regeneration process. Stand reconstruction studies provided a useful tool to help designing regeneration systems using a natural experiment. Some specific management implications for symptomatic A. chilensis forests are given.     

Effect of major inorganic nutrients on <Emphasis Type="Italic">β</Emphasis>-thujaplicin production in a suspension culture of <Emphasis Type="Italic">Cupressus lusitanica</Emphasis> cells

 The optimum conditions for β-thujaplicin production in a Cupressus lusitanica cell suspension culture were investigated. The conditions required for β-thujaplicin production were clearly different from the conditions for cell growth. The initial phosphate concentration and pH did not affect β-thujaplicin production. A total nitrogen source concentration higher than 3.2 mM suppressed production due to the presence of the ammonium ion. β-Thujaplicin production was observed at 95 mg/l without adding the ammonium ion to the medium. Strict control of major inorganic nutrients was not necessary to produce β-thujaplicin. This finding seems to be favorable for future automated production of β-thujaplicin in commercial cell culture plants.     

Are marginal beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) provenances a source for drought tolerant ecotypes?

Due to the expected increases of number and intensity of summer droughts in Central Europe the identification of drought tolerant ecotypes becomes more important in future forestry. A common garden experiment with seedlings of Fagus sylvatica provenances from the center (Germany) and eastern margin (Poland) of the species’ distribution range was conducted. Responses of morphological, physiological, chemical and growth parameters to three drought treatments were analyzed. Relative growth rates of the marginal provenance were lower as compared to the central provenance. The marginal seedlings showed a tendency to higher total biomasses because of higher seed masses. In both provenances drought decreased biomass production and root/shoot ratio which was lower in the central provenance. A lower specific root area of the marginal provenance indicated a better adaptation to low xylem water potentials. Under moderate drought, lower leaf δ¹³C signatures may indicate lower stomatal limitation (or a reduced rate of CO₂ assimilation) in the marginal provenance. We conclude that marginal beech provenances may exhibit a better drought adaptation.     

牡丹&#183;杜鹃&#183;石竹

由于森林缔造了我,因此我生命的每一个细节都在与森林对话。当我心浮气躁时,森林用宁静的语言使我顿悟,至纯至静的哲理,才是修炼的主题。     

Fine-root dynamics in a young hinoki cypress (<Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>) stand for 3 years following thinning

Fine roots play a key role in carbon and nutrient dynamics in forested ecosystems. Fine-root dynamics can be significantly affected by forest management practices such as thinning, but research on this topic is limited. This study examined dynamics of fine roots <1 mm in diameter in a 10-year-old stand of hinoki cypress (Chamaecyparis obtusa) for 3 years following thinning (65% in basal area). Fine-root production and mortality rates were estimated using a minirhizotron technique in combination with soil coring. In both thinned and un-thinned control plots, fine-root elongation occurred from early spring to winter (March to December) and fluctuated seasonally. In the thinned and the control plots, the annual fine-root production rates were estimated to be 101 and 120 g m⁻² year⁻¹, respectively, whereas the estimated annual fine-root mortality rates were 77 and 69 g m⁻² year⁻¹, respectively. At 3 years after thinning, live fine-root biomass was significantly smaller in the thinned plot (143 g m⁻²) than in the control plot (218 g m⁻²), whereas dead fine-root biomass was not (147 and 103 g m⁻², respectively). Morphological and physiological indices of fine roots such as diameter, specific root length, and root tissue density of the live fine roots was similar in both plots. These results suggested that thinning tended to decrease biomass and production of fine roots, but the effects on characteristics of fine roots would be less evident.     

Optimum pruning intensity for reducing crop suppression in a <Emphasis Type="Italic">Gmelina</Emphasis>–maize smallholder agroforestry system in Claveria,Philippines

On-farm trials were conducted to assess the effects of four branch pruning levels on maize grain yield, tree growth and stem shape. The experimental plots consisted of Gmelina (Gmelina arborea R.Br.) trees planted at 1 × 10 m with maize intercropped in the 10 m-wide alleys between lines of trees. Pruning levels consisted of retaining a live crown ratio of 60–70% (T ₁), 40–50% (T ₂); 30–40% (T ₃) and of 20–30% (T ₄). At the end of the experiment, the total maize grain yield was highest under the high pruning intensity (T ₄) (18.06 t ha⁻¹) and lowest under T ₁ (14.48 t ha⁻¹). Maize grain yield under the pruning regime T ₂ and T ₃ were 16.08 and 17.21 t ha⁻¹, respectively. Mean annual increment (MAI) in tree diameter was greater (5.0 cm year⁻¹) under T ₁ than those at T ₄ (4.1 cm year⁻¹). Pruning regimes T ₂ and T ₃ resulted in a MAI of 4.7 and 4.5 cm year⁻¹, respectively. Financial analysis showed that maize-tree systems under T ₄ were more profitable than under T ₁ as long as the reduction of the average dbh at harvest were not greater than 1 cm. Pruning trees intensively also generated greater returns from labour than moderate pruning, as the greater maize grain yields under T ₄ compensated for the cost of pruning and the lower timber yield. In the context of resource-poor farmers, intensive branch pruning was a practice that prolonged the period of profitable intercropping and was compatible with commercial timber production.     

Fagacées: a tree-centered growth and yield model for sessile oak (<Emphasis Type="Italic">Quercus petraea</Emphasis> L.) and common beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

• Introduction  

Fagacées is a growth model that has been developed for pure Oak or Beech stand management in even-aged high forests and coppice with standards forests. It has been calibrated for the plain forests of northern France.     

Tree and stand growth for clonal <Emphasis Type="Italic">E. urophylla</Emphasis> × <Emphasis Type="Italic">grandis</Emphasis> across a range of initial stockings in southern China

A large initial stocking × fertilizer factorial field trial established in 1993 with a Eucalyptus urophylla × grandis hybrid clone in southern Guangxi province, China, included 6 initial stocking treatments ranging from 667 to 2,222 trees ha⁻¹ and 6 fertilizer treatments. Growth data was collected at various intervals up to age 192 months and also data on outer-wood pilodyn penetration (as an indicator of wood density) and acoustic velocity through the outer-wood (as an indicator of modulus of elasticity) at the last assessment. This report examines the results for the main effect of initial stocking treatments and stocking × fertilizer interactions across ages. There were significant differences between initial stockings for both average individual tree volume and standing volume ha⁻¹ at all ages up to 144 months, but just average individual tree volume at 192 months. At ages up to 75 months total standing volume decreased as initial stocking decreased—maximum volume being obtained at 2,222 trees ha⁻¹. From 88 to 110 months the highest standing volume was obtained at 1,667 trees ha⁻¹ and then at ages 144 and 192 months, 833 trees ha⁻¹ provided the highest standing volume. Average individual tree volume at all ages generally increased as initial stocking decreased—the largest trees were obtained at 667 trees ha⁻¹. As age increased the proportional differences between tree volumes at higher and lower stockings increased—at age 27 months average individual tree volume at 667 trees ha⁻¹ was 72% greater than that at 2,222 trees ha⁻¹ and differences increased steadily with age up to 190% at 192 months. There were no significant differences between initial stockings for the properties of the outer-wood assessed by pilodyn penetration and acoustic velocity. Also, no significant interactions were found between initial stocking and fertilizer treatments for any traits at any ages implying that effects of initial stocking and fertilizer are additive for the traits assessed.     

Factors controlling soil water-recharge in a mixed European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)–Norway spruce [<Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst.] stand

The spatial dynamics of soil water-recharge in a forest stand is the product of a number of interacting processes. This study focuses on the role of tree species and antecedent soil water content upon horizontal and vertical patterns of soil water recharge in heavy clay soils of a mixed European beech–Norway spruce stand and of a pure Norway spruce stand after rewetting periods with different rain quantities and intensities. Volumetric water content (VWC) was measured at 194 locations across 0.5-ha plots in each stand using time-domain reflectometry (TDR) with fixed 30- and 60-cm vertical waveguides. This was repeated 28 times (as close as possible) before and after rewetting periods during the vegetation seasons in 2000 and 2001. In addition, the locations of all trees within the plots were recorded. Geostatistics was used to describe the spatial correlation between VWC measurements and to interpolate soil water recharge in space. Spatial patterns of soil water recharge were then evaluated according to antecedent soil water-content and tree species distribution. Open-field precipitation of 30 mm (maximum intensity 10 mm h^–1) on extremely dry initial soil conditions resulted in higher subsoil (30–60 cm soil depth) recharge and erratic recharge patterns. This was presumably due to preferential flow in opening shrinkage cracks of the heavy clay soil. A comparable quantity and intensity of rainfall under moderately dry antecedent soil water conditions resulted in almost exclusively topsoil (0–30 cm soil depth) water recharge and patterns of recharge that were clearly related to tree species distribution. The higher recharge around beech trees can be attributed to the lower interception rates there. Spatial patterns of soil water recharge reflect patterns of antecedent soil water conditions.     

Soil phosphorus and water effects on growth,nutrient and carbohydrate concentrations, δ<Superscript>13</Superscript>C,and nodulation of mimosa (<Emphasis Type="Italic">Albizia julibrissin</Emphasis> Durz.) on a highly weathered soil

Growth and physiological performance of multipurpose tree species can be severely constrained by low phosphorus (P) availability in highly weathered soils. Limitations to plant growth are accentuated by seasonal dry periods. The overall objective of this study was to examine P fertilization and irrigation effects on survival, growth, biomass partitioning, foliar nutrients, intrinsic water-use efficiency (WUE) indexed by δ¹³C, Rhizobium nodulation, and carbohydrate content as an indicator of resprouting potential, of mimosa (Albizia julibrissin Durz.), a N₂-fixing tree species being tested for browse in agroforestry practices in south-central USA. In a field experiment carried out during two growing seasons near Booneville, Arkansas, USA, mimosa had a strong growth response to irrigation. The trial was arranged in a split plot design with three replications with irrigation as main plot treatment and P as sub-plot treatment. Mean total plant aboveground biomass at the end of the second growing season was 9.8 and 44.1 g plant⁻¹ for the rainfed treatment without and with 300 mm of irrigation water, respectively. Placed P fertilization increased mean total aboveground biomass from 19 g plant⁻¹ for the 0-P treatment to 69 g plant⁻¹ for the treatment with 90 kg P ha⁻¹ year⁻¹. Similarly, irrigation consistently increased stem basal diameter, total height, survival, root, stem, foliar and total aboveground biomass, and number of nodules per plant. Phosphorus fertilization increased basal diameter, and root and stem biomass in both irrigation treatments, survival and nodulation in the rainfed treatment, and foliar and total aboveground biomass in the rainfed +300 mm irrigation treatment. There was a decrease of foliar δ¹³C suggesting that WUE decreased with P fertilization. In a pot experiment, seedlings were subjected to a factorial combination of two irrigation treatments and six P levels in a randomized complete block design. Irrigation increased basal diameter, root, stem, foliar and total biomass, leaf area and nodulation, whereas P fertilization (i.e., levels from 0 to 3.68 g P kg⁻¹ soil) had similar effect in all the above variables except foliar biomass. Foliar P concentration to obtain 90% of the maximum total plant biomass (critical level) was estimated at 0.157%. Total nonstructural and water soluble carbohydrate, and starch concentrations increased non-linearly with irrigation and P addition suggesting impaired re-growth potential after defoliation of seedlings with reduced water supply and at low soil P availability. Results of this study indicated strong limitations for growth and regrowth potential of mimosa on a highly weathered soil with very low P availability and seasonal water content shortages. Placed (i.e., near the plant base) application of P appeared to be a good strategy to fertilize perennial woody plants.     

Sprouting characteristics of <Emphasis Type="Italic">Quercus pubescens</Emphasis> Willd. and <Emphasis Type="Italic">Quercus frainetto</Emphasis> Ten. trees after a wildfire: To cut or not to cut the burned trees?

The aims of this study were to analyze the sprouting characteristics of Quercus pubescens and Q. frainetto trees after a wildfire and to recommend the appropriate silvicultural treatments in order to achieve dense sprout origin regeneration. This study was carried out in the area that was burned in a wildfire in northeastern Greece. Three years later, 140 Q. pubescens trees and 140 Q. frainetto trees were selected. Seventy trees for each species were individuals that were cut after the fire and were in the form of stumps, while 70 trees were intact top-killed trees, as a result of fire. In each stump and intact tree that was selected, various parameters were measured or counted: the diameter at the level of ground, the number of the developed sprouts (if any) and the height as well as the basal diameter of the tallest sprout, etc. Both species have similar sprouting behavior after a wildfire. Mother tree dimensions positively influenced the number of sprouts and the growth of the tallest sprout per individual. The mean height of the tallest sprout per stump, after three growing seasons from the forest fire, is high in both species (2.08 m for Q. pupescens and 2.29 m for Q. frainetto). Cut stumps had more sprouts than intact trees in both species. Forest practice, in order to maximize the sprouting of Q. pubescens and Q. frainetto trees after a forest fire, should cut the burned trees before the next growing season.     

Conjugation of δ-endotoxin from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> with abamectin of <Emphasis Type="Italic">Streptomyces avermitilis</Emphasis> as a new type of biocide,GCSC-BtA,for control of agricultural insect pests

Conjugation of δ-endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on “Germany-China Scientific Cooperation” research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25?mM dithiothreitol (DTT) at 37?°C for 2?h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10?mg/ml butyric anhydride at 111?°C in a water-circumfluent condensation device for 2?h. The conjugating reaction, consisting of 5?mg/ml B.t. protoxin, 10?mg/ml carboxylated abamectin and 19.17?mg/ml EDC, was successfully conducted at room temperature for 24?h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600?nm (P?<?0.01). LT₅₀ of the conjugated GCSC-BtA to the 3^rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 μg a.i./ml, about 62?% and 76?% of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14?% mortalities in larvae of P. xylostella, 93.75?% in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33?% in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33?% by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3^rd instar of P. xylostella were black color in the head part and white-yellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.