Light distribution,photosynthetic rate and yield in a Paulownia-wheat intercropping system in China

Measurements of photosynthetically active radiation (PAR), leaf photosynthesis, canopy leaf area index (LAI) and crop yield were carried from flowering to maturity to study the effects of tree shading on crop yield in a Paulownia-wheat intercropping system in China. We found that the tree shading reduced the amount of incoming PAR within the intercropping system by 22%, 44% and 56% during flowering, grain-filling and maturing, respectively. The amount of PAR intercepted by the wheat crop inside the intercropping system was 34%, 55% and 68% less than the crop outside the intercropping system during flowering, grain-filling and maturing. Estimates of PAR-saturated leaf photosynthetic rate were not affected by tree shading, and the differences between the wheat yield inside the intercropping system and outside the intercropping system can be explained by the difference in the amount of PAR intercepted. Total grain numbers and grain dry weight per 1000 grains were linearly correlated with the amount of PAR intercepted during 7 days prior to anthesis and during anthesis and grain-filling, respectively. As compared with the wheat crop outside the intercropping system, grain numbers and grain dry weight were reduced by 36% and 25%, respectively. As a result wheat yield inside the intercropping system was 51% lower than that outside the intercropping system. Our results suggest a much higher reduction in crop yield and much smaller economic gain of the Paulownia-wheat intercropping system than previous studies on the similar Paulownia-wheat intercropping systems in China.     

Light-related competitive effects of overstory trees on the understory conifer saplings in a subalpine forest

To clarify the mechanism by which overstory trees shade understory saplings, we investigated the relationships among light conditions of the saplings (measured as indirect site factor; ISF and direct site factor; DSF), the calculated competition effects of overstory trees on the saplings (W), and relative height growth rate of the saplings (RHGR). We calculated several W values in order to find a W value which can express the light conditions as appropriately as possible, and the results indicated that W explained only 21.9%–24.7% of the total variance of light conditions in the cases where W gave the best fit. In this study, W was calculated based on the basal areas of overstory trees. However, it is known that canopy structure also affects the light regimes in the forest understory, and this might yield the possible errors even within W representing the shading effects most adequately. Therefore, although W significantly represents the shading effect from overstory trees, a great proportion of the variance remained without being explained by W. RHGR was negatively correlated with W, and the W value which had the most adequate explanation of the shading effect also showed the best negative correlation with RHGR. This provides the evidence that the competitive effect of overstory trees on sapling growth is mediated by the shading effect, indicating that competition for light clearly exists within this forest. Such competition for light may closely relate to the well-known phenomenon of gap regeneration in subalpine forests in central Japan.     

3个朱顶红品种的光适应性研究

以朱顶红的3个品种为研究对象,研究了不同遮光处理（全光,遮阴度为30%、60%、90%）对其生长量及净光合速率日变化、净蒸腾速率日变化的影响。结果表明：3个朱顶红品种的叶长、叶宽、叶面积、花葶高度均随着遮阴处理程度的加大而显著增加,而花冠大小及花色无明显差别;3个朱顶红品种在30%的遮光下全天的日平均净光合速率最高,全光下日平均净蒸腾速率最高。结论：3个朱顶红品种更适宜在30%的遮光环境下栽植。     

Canopy openings may prevent fir broom rust (<Emphasis Type="Italic">Melampsorella caryophyllacearum</Emphasis>) infections

Melampsorella caryophyllacearum is a heteroecious fungus that produces disease on silver fir resulting in galls that depreciate the value of trees. Currently, little is known about its epidemiology. The purpose of this study was to identify those site or management factors associated with fir broom rust infection. A 29-plot systematic sampling was carried out throughout all silver fir forests in the Spanish Pyrenees. In every sampling plot, we examined each tree for the presence of M. caryophyllacearum galls or witch’s brooms. We differentiated their position as either on the main stem or on the branches of trees. We identified the most susceptible stands by relating a compendium of tree and stand variables with the presence and severity of symptoms. Disease symptoms were observed in 11.8% (95% CI: 5.8–17.9%) of trees. Fir broom rust-infected trees tended to be those of larger diameters. The rust infection was observed in 55.2% (95% CI: 35.7–73.6%) of the stands. We identified a wide range of severities with 5 of 29 stands having more than 30% of trees infected. Fir broom rust appeared to be a widespread disease, although we observed important differences in terms of severity. The presence and severity of the rust in stands was associated with understories composed of more shade tolerant plant species and with longer periods without thinnings. Canopy opening should be experimentally tested as a possible control method.     

Consequences of dry-season seed dispersal on seedling establishment of dry forest trees: Should we store seeds until the rains?

We examined the following hypotheses: (i) seeds of dry forest trees have high pre- and post-germination mortality by desiccation due to the time between seed dispersal and germination and to irregular rains at the onset of the rainy season; (ii) seedlings from seeds dispersed in the dry season which survive the dry spells are larger at the end of the first rainy season than those dispersed in the rainy season because the former have more time to grow. We evaluated the possible trade-off between few large seedlings (resulting from natural dispersal) × many small seedlings (resulting from delayed dispersal) on seedling survival during the dry season. We sowed eight tree species in a greenhouse in September, simulating the natural dispersal timing (before the rains), and in November, when rains are more constant. Because shading can counteract the effects of desiccation, we applied three levels of shade (10%, 40% and 72% of PPFD). From September 2005 to December 2006, we provided the daily precipitation of a median year from a major patch of dry forest in Central Brazil. At the end of the rainy season, a subset of seedlings was collected for growth measurements (dry mass) and the remainder was left to follow the dry season survivorship. The lower germination expected for seeds dispersed in the dry season and in full sun was not confirmed for species that had some dormancy. The delayed dispersal was advantageous for the initial establishment of fast germinating species, but it was irrelevant or even disadvantageous for others. Also, the greenhouse weather was certainly milder than the natural environment, reducing the potential for mortality by desiccation. The growth of the four species of higher dormancy were not affected by timing of seed dispersal, while three out of four fast germinating species had higher root biomass when dispersed in the dry season. The growth during the rainy season did not affect seedling survival during the dry season. Keeping seeds to sow when rain is constant might be a good strategy to increase the establishment of fast-germinating tree species.     

红雉凤仙花形态与光合特性对光强的响应及其耐阴性评价

评价野生花卉植物的耐阴性并揭示其耐阴机制,有助于该类植物有效的引种栽培和合理的开发利用。采用遮阳网对峨眉山野生观赏花卉红雉凤仙花(Impatiens oxyanthera)进行遮荫处理,相对光强为(26.242±1.029)%,以全光照作为对照,遮荫约4个月后,测定植株形态和气体交换特征,并计算光响应参数。结果表明:遮荫促进红雉凤仙花生长,所测定的形态指标(株高、基径、分枝数、冠幅、单叶面积、叶长和叶宽)均显著增加。与全光照条件下相比,遮荫使红雉凤仙花的蒸腾速率(T_r)和气孔导度(G_s)显著下降,进而导致净光合速率(P_n)显著降低,但对胞间CO_2浓度(C_i)、水分利用效率(WUE)和气孔限制值(L_s)影响不显著。同时,遮荫使红雉凤仙花的表观量子效率(AQY)显著增大69.841%。主成分分析以及隶属函数法综合评价表明,该植物耐阴综合平均值为0.407。红雉凤仙花通过增加单叶面积,以弥补遮荫引起的净光合速率降低,增大表观量子效率,提高对弱光的利用能力,以促进其生长,较强的耐阴性使得该植物在园林植物造景和建筑物遮荫区绿化中具有重要的应用价值。     

6个山茶品种的耐晒性研究

为筛选出耐晒性较强的山茶花品种,以烈香、六角大红、克瑞墨、金花茶、五色赤丹、迪斯6个品种为试验材料,研究不同光照强度（全光照、遮阴率50%、遮阴率70%、遮阴率90%）对植物形态指标及叶绿素含量的影响。结果表明,从生长特性、叶绿素含量、生物量积累等方面来看,全光照条件下品种迪斯、克瑞墨的生长表现最好,不同程度的遮阴处理均影响各品种的生长。最终筛选出品种迪斯、克瑞墨作为耐晒性较强的山茶品种。     

Coffee yields and soil nutrients under the shades of Inga sp. vs. multiple species in Chiapas, Mexico

For many decades, simplification of traditionally shaded coffee-production systems has been an idealised model for increasing yields. In Mexico, coffee producers have been interested in replacing diverse natural shade with Inga species monocultures due to this practice having the supposed advantages of producing higher coffee yields than diverse shade. However, the effect of different shade systems on yields is little known. The purpose of this study was to evaluate the effect of two types of shaded-coffee systems on coffee yields and soil nutrient content; the first shade system is mainly dominated by Inga latibracteata Harms and the other composed of species-rich natural vegetation. The investigation took place in producer plots in the Francisco I. Madero Community, Municipality of Jitotol, Chiapas, Mexico. Collected data included species richness, shade-tree density, number of strata, tree diameter, tree height, shade-cover percentage, direct and diffused light, coffee yields, soil-nutrient concentrations (N, P, K, Ca and Mg), soil-organic matter and pH. Evaluated shade type did not have an effect on grain yield or soil nutrients. The perceived advantage of the Inga shade system is reduced weed emergence, saving farmers one annual weed-clearing. There was no significant correlation between total N and organic matter. The presence of fewer products and services in comparison to the multiple shade system was thought to be an additional disadvantage to the Inga dominated system. Organic matter in the multiple shade system correlated positively with total N. Due to its complex structure and diversity, the multiple shade system could be certified as shade or bird-friendly coffee. This revised version was published online in June 2006 with corrections to the Cover Date.     

Productivity of Theobroma cacao agroforestry systems with timber or legume service shade trees

Timber production and cocoa yields were studied (initial 10?C11?years) in two experimental plantations: a Cocoa-Legume system (CL, Erythrina poeppigiana, Gliricidia sepium or Inga edulis), and a Cocoa-Timber system (CT, Cordia alliodora, Tabebuia rosea or Terminalia ivorensis, plus I. edulis for inter-site comparisons). These trials had two major goals: (1) to evaluate the use of mono-specific timber shade canopies as an alternative to traditional, mono-specific, legume service shade tree canopies; and (2) to determine the production potential of ten cocoa clonal bi-crosses under these shade tree species. Within each site, shade tree species did not influence dry cocoa bean yield nor pod counts (total number of pods produced, number of healthy pods harvested, pod losses due to monilia [Moniliophthora roreri], black pod [Phytophthora palmivora] or other causes??birds and squirrels in this study-, and total pod losses). Significant differences were found between cocoa bi-crosses for both cocoa bean yield and pod counts. Sites differed only in terms of total pod losses (43% in CL; 54% in CT) and their causal factors (mainly monilia in CL; both monilia, squirrels and birds in CT). At CT, all timber tree species grew rapidly, reaching 30?C34?cm?dbh, 17?C25?m total tree height and 97?C172?m³?ha^?1 total stem volume (age 10?years). Timber species should be promoted for the shade component of cacao plantations given their potential production and the fact that their presence did not negatively affect cocoa yields.     

Potential of the APSIM model to simulate impacts of shading on maize productivity

A number of agroforestry models have been developed to simulate growth outcomes based on the interactions between components of agroforestry systems. A major component of this interaction is the impact of shade from trees on crop growth and yield. Capability in the agricultural production systems simulator (APSIM) model to simulate the impacts of shading on crop performance could be particularly useful, as the model is already widely used to simulate agricultural crop production. To quantify and simulate the impacts of shading on maize performance without trees, a field experiment was conducted at Melkassa Agricultural Research Centre, Ethiopia. The treatments contained three levels of shading intensity that reduced incident radiation by 0 (control), 50 and 75% using shade cloth. Data from a similar field experiment at Machakos Research Station, Kenya, with 0, 25 and 50% shading were also used for simulation. APSIM adequately simulated maize grain yield (r² = 0.97) and total above-ground biomass (r² = 0.95) in the control and in the 50% treatments at Melkassa, and likewise in the control (r² = 0.99), 25% (r² = 0.90) and 50% (r² = 0.98) treatments at Machakos. Similarly, APSIM effectively predicted Leaf Area Index attained at the flowering (r² = 0.90) and maturity (r² = 0.94) stages. However, APSIM under-estimated maize biomass and yield at 75% shading. In conclusion, the model can be reliably employed to simulate maize productivity in agroforestry systems with up to 50% shading, but caution is required at higher levels of shading.     

Cacao-coconut intercropping in Ghana: agronomic and economic perspectives

In Ghana, shade for cacao (Theobroma cacao L.) is becoming a critical issue because of extensive deforestation. Unlike in some other cacao-growing countries, cacao is not grown under the shade of coconut (Cocos nucifera) in Ghana. An experiment to compare the merits of four cacao-coconut intercropping systems with the traditional cultivation of cacao under Gliricidia sepium shade was undertaken at the Cocoa Research Institute of Ghana. Cacao seedling girth was not affected when intercropped with coconut but was significantly (P = 0.01) reduced when intercropped with G. sepium. High density cacao facilitated better early canopy formation. Yield of cacao spaced at 2.5 m triangular (1739 plants ha^–1) with coconut at 9.8 m triangular (105 plants ha^–1) was significantly higher (P = 0.05) than from the other treatments during 1993/94 to 1995/96. There were no major disease problems associated with intercropping cacao with coconuts. Widely spaced coconuts intercropped with cacao spaced at 3 m × 3 m showed better flowering and gave higher coconut yields, but cacao spaced at 2.5 m triangular under coconuts spaced at 9.8 m triangular was more profitable than the other treatments. Moisture stress was the greatest in cacao system with G. sepium shade and this could be responsible for the low yield of cacao in that treatment. It is suggested that properly arranged high density cacao under widely spaced coconuts can be a profitable intercrop system for adoption by cacao farmers in Ghana.This revised version was published online in November 2005 with corrections to the Cover Date.     

Tree effects on forage growth and soil water in an Appalachian silvopasture

Silvopastures may have the potential to increase forage yields beneath trees compared to open pasture at some sites. This has been attributed to a combination of factors including improved water use efficiency by shaded grass and increased water availability through hydraulic lift by trees. The objectives of this research were to determine if silvopastures changed forage mass production and available soil water, and to determine how these two factors were related. Forage mass and soil water were sampled at 1.0, 2.0, and 3.6 m from the tree stem, or plot center under honey locust (Gleditsia triacanthos L.), black walnut (Juglans nigra L.) and shade cloth in 2006 and 2007. Soil water was measured in the top 10 cm of soil using a capacitance probe, and at 30-cm intervals, from 45 to 105 cm, using a neutron probe. Forage was collected to determine dry mass and annual yield. In 2006, forage mass was greater under black walnuts and honey locusts than under 70% shade cloth. In 2007, with a 50% shade cloth, forage growth was similar in all treatments. In both 2006 and 2007, soil moisture in the top 10 cm was higher under shade cloth compared to honey locust or black walnut trees. Similarities in forage mass between treatments in 2007 indicate that the differences in soil water were not biologically significant for forage growth. Lower forage mass under the 70% shade cloth in 2006 was due to suppressed growth from intense shading. The major implication for pasture managers is that trees in these pastures had no negative effect on soil water availability and forage growth.     

早竹丛枝病的调查及病原菌的分子鉴定

[目的]对早竹丛枝病进行调查及病原菌分子鉴定,为早竹丛枝病的病害诊断和防治提供科学依据。[方法]采用单株水平和单枝盘水平的2种病害分级标准对早竹丛枝病进行调查。使用植原体16S rDNA和真菌rDNA-ITS序列的特异性PCR引物,对早竹丛枝病的病原菌进行分子鉴定。[结果]调查的6块样地早竹丛枝病的平均发病率为18.59%,平均病情指数为6.67。感病的早竹DNA样品能够扩增出真菌的rDNA-ITS序列,而不能够扩增出植原体的16S rDNA序列;扩增出的序列与报道的竹针孢座囊菌的序列同源性达到99.00%,与其它真菌的序列同源性最高仅为94.00%。[结论]浙江省德清县早竹丛枝病的病原菌为竹针孢座囊菌。     

Identification of Cylindrocladium sp. causing damping-off disease of Japanese black pine (Pinus thunbergii) and factors affecting the disease severity in a black locust (Robinia pseudoacacia)-dominated area

The regeneration of Japanese black pine (Pinus thunbergii) seedlings is inhibited in a black locust (Robinia pseudoacacia)-dominated area. We examined the presence of pathogenic fungi in Japanese black pine seedlings in the area in order to determine the effect of pathogenic fungi on the inhibition of regeneration. When Japanese black pine seedlings were planted in the soil obtained from a black locust-dominated area, all of the seedlings died under low-intensity light conditions, whereas 84% of the seedlings survived in the soil obtained from a Japanese black pine-dominated area under the same light conditions. One fungus was isolated from 48.7% of the dead pine seedlings and was identified as Cylindrocladium pacificum Kang, Crous & Schoch, based on the morphological characteristics, growth, and DNA analysis. This fungus was also isolated from 50% of the dead pine seedlings in 2005 and 66.7% of the seedlings in 2006—both were planted in a black locust-dominated area. The virulence of this fungus increased under high-nitrogen and/or low-intensity light conditions. These results reveal the possibility that the soil eutrophication and shading by the black locust are conducive to a severe damping-off disease and threaten the survival and regeneration of Japanese black pine seedlings.     

Stand structure and composition of a 60-year-old larch (Larix kaempferi) plantation with retained hardwoods

Tree retention is understood as a key practice in creating complexity, leading to heterogeneity in resources and habitats in managed stands. In this article, we clarify the long-term effects of tree retention on stand structure and tree-species composition in a 60-year-old Larix kaempferi plantation in central Japan. In our study plot (1.5 ha) there were 18 stems/ha of retained trees (determined by tree-ring analysis), mostly Quercus crispula. We conducted spatial analyses and tested the hypothesis that tree abundance, size structure, and species composition and diversity change with distance from the retained trees. Near the retained trees, L. kaempferi showed a reduction of 40%–60% in basal area, due presumably to the shading effect. In contrast, the nearby area showed greater species diversity in the canopy layer. The retained trees created patches of different species composition in the understory. The spatial gradient of shade and colonization opportunity provided by retained trees greatly affect the distribution of the colonized species, according to their shade tolerance and seed-dispersal ability, which resulted in the stand structure with a heterogeneous shrub-layer vegetation. Retention proved particularly important for the enhancement and long-term maintenance of structural and compositional complexity in L. kaempferi plantations.     

Shade improves coffee quality in a sub-optimal coffee-zone of Costa Rica

Quality is an important attribute of coffee. Therefore it is important to understand the effect of overstory trees not only on the environment and long-term coffee production, but also on the quality of coffee grown underneath the trees. This study compared coffee quality of Coffea arabica L. vars. Caturra and Catimor 5175 under different levels of shade in a low-elevation, sub-optimal environment for coffee in Costa Rica. Fruit weight and bean size increased significantly when shade intensity was increased from 0% to more than 80% under unpruned Erythrina poeppigiana. While large beans (diameter > 6.7 mm) accounted for 49 and 43% of the coffee from unshaded Caturra and Catimor, respectively, these proportions increased to 69 and 72% under dense permanent shade. This suggested a stronger shade benefit for Catimor than for Caturra. The conversion percentages from fresh-weight coffee fruits to dry-weight green coffee for export were not affected by the treatments. A blind tasting experiment showed consistent shade-induced improvements in appearance of green and roasted coffee as well as in acidity and body of the brew for both varieties. The effect of shade on aroma of the brew was neutral for Caturra and slightly negative for Catimor. It is hypothesized that, in the sub-optimal (low-altitude) coffee-zone studied, shade promotes slower and more balanced filling and uniform ripening of berries, thus yielding a better-quality product than unshaded coffee plants. Shade experiments along environmental gradients should help to validate this conjecture and its relative importance in different coffee-zones.     

花叶蔓长春的耐荫性研究

对花叶蔓长春在不同遮荫度下的生长进行初步研究的结果表明,花叶蔓长春在63％遮荫处理中,夏季高温时生长良好,叶片肥大,叶绿素含量增加,开花量最多。     

Competition for light between hedgerows and maize in an alley cropping system in Hawaii, USA

Successful agroforestry systems depend on minimizing tree-cropcompetition. In this study, field experiments and a simulation model were usedto distinguish between tree-crop competition for light and belowgroundcompetition in an alley cropping system. Maize (Zea maysL.) was harvested periodically in three treatments: between vertical barriers ofshade cloth, hedgerows of Flemingia macrophylla (Willd.)Merr., and sole maize. Radiation intercepted by the maize was calculated using asimulation model based on measured values for direct and diffuse light, hedgerowdimensions and leaf area, and solar trajectory. Radiation use efficiency wascalculated as biomass production per unit of intercepted radiation. Maizebiomass and yield in both the alley crop and the shade cloth treatment weregreatest in the center of the alleys. Grain yield between hedgerows was 3.5Mg ha⁻¹ (averaged across the alley), significantlyless than in the shade cloth (7.4 Mg ha⁻¹) or thesole maize (7.7 Mg ha⁻¹) treatments. Lightintercepted by the maize in the alley crop was about half that intercepted bythe maize in the sole crop. The shade cloth intercepted less light than thehedgerows because it did not have an appreciable width. Radiation use efficiencyin the three treatments was 0.75 g mol⁻¹ PAR anddid not differ significantly among treatments. Tree-crop competition wasoverwhelmingly for light. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of shelter tubes on hardwood tree establishment in western Oregon silvopastures

Honey locust (Gleditsia triacanthos), black locust (Robinia pseudoacacia), and honey mesquite (Prosopis glandulosa) are warm season forage trees with potential to efficiently share site resources with cool season pasture plants in Pacific Northwest silvopastures. Establishment of hardwood trees can be difficult, however, because of feeding damage from wildlife and livestock. This study compared establishment and growth of trees planted in 88 cm tall solid plastic shelter tubes to 88 cm tall plastic mesh tubes, used to protect trees from animal damage. Three replications were established in May 1995 for each of the three tree species on a hill pasture near Corvallis, Oregon. Initial tree survival during the first summer and winter following planting was higher in shelter tubes than in mesh tubes. At the end of the third growing season, 58% of black locust and 94% of honey locust trees in shelter tubes were still alive compared to only 14% of black locust and 47% of honey locust in mesh tubes. Few honey mesquite trees survived regardless of tube type used. Average three-year total height growth for black locust was increased by 650% and basal diameter growth by 380% within shelter tubes, while honey locust height growth was increased by 300% and diameter growth was increased by 150% compared to trees in mesh tubes. However, shelter tube trees tended to be taller relative to their diameter and had difficulty standing upright if tubes were removed. This revised version was published online in June 2006 with corrections to the Cover Date.     

遮阴处理对金蒲桃生长量及光合参数的影响

以2 a生金蒲桃(Xanthostemon chrysanthus)幼苗为材料,研究了全光照,50%遮阴,70%遮阴,90%遮阴4种遮阴处理对金蒲桃生长特性、生物量分配、光合生理变化的影响,结果表明:与自然光全处理对比,遮光极显著(P<0.01)地抑制了金蒲桃幼苗生物量的积累,遮光处理组叶片数量减少,叶生物量比下降,茎生物量比增加;光补偿点、光饱和点、暗呼吸速率和最大光合速率降低,光能利用效率低于全光照叶,强光下遮阴叶的净光合速率保持稳定.上述结果说明:遮阴处理后,金蒲桃在生长特性、生物量分配和光合参数上表现出对遮阴弱光的适应,表明金蒲桃是一种能广泛应用于各种光照条件的优良景观树种.