Forage yield and quality of Leucaena leucocephala and Guazuma ulmifolia in mixed and pure fodder banks systems in Yucatan,Mexico

In tropical areas of Mexico, Leucaena leucocephala is widely used in silvopastoral systems. However, little information exists on other native woody species of high forage potential, such as Guazuma ulmifolia. The aim of this study was to evaluate the components of biomass, forage yield and quality, and availability of N in fodder banks of L. leucocephala, G. ulmifolia, and a mixture of both species during dry and rainy seasons, under sub-humid tropical conditions. The experimental unit was a 5 × 10 m plot, containing three rows with 2 m between rows; each row had 20 plant positions with 0.50 m between plants. Within each plant position there was either a single plant, in the case of pure-crop, or two plants, in the case of mixed of both species. A complete randomized block design with three repetitions was used. In both seasons, there were a significantly greater proportion of leaves in the G. ulmifolia fodder banks (71 %) and in mixed fodder banks (69 %) than in L. leucocephala fodder banks (64 %). Consequently, these systems had leaf-to-stem ratios of 2.4, 2.2 and 1.9, respectively. The forage yield of fodder banks was not influenced by season. The mixed fodder bank had greater forage yield (5.1 t DM ha^?1) than the L. leucocephala fodder bank (3.4 t DM ha^?1) in each season. Additionally, the mixed fodder bank accumulated more forage yield during the experimental period (10.2 t DM ha^?1 year^?1) than G. ulmifolia (9.0 t DM ha^?1 year^?1) or L. leucocephala (6.9 t DM ha^?1 year^?1). The concentrations of CP, C and C:N were not influenced by season. Forage NDF and ADF concentrations were greater in the rainy season (476 g kg^?1 DM) compared with the dry season (325 g kg^?1 DM). Mixed fodder banks had the greatest N yield (185.9 kg ha^?1) and consequently the greatest availability of N (371.8 kg N ha^?1 year^?1). We conclude that mixed fodder banks of L. leucocephala and G. ulmifolia are a better option for improving productivity and forage quality in comparison with pure fodder banks in Yucatan, Mexico.     

Morphology, productivity and forage quality of Leucaena leucocephala as influenced by irrigation under field conditions

A field study was conducted to investigate the effect of water deficit on the morphology, productivity, and quality of Leucaena leucocephala (Lam.) De Wit. Five main irrigation levels were applied based on actual evapotranspiration (AET): 0.25, 0.50, 0.75, 1.00, and 1.25 of the AET. Plant height, number of leaves and branches, and root length and diameter were measured. Fresh and dry weights were recorded at harvest, and crude protein was analyzed in leaves and roots. The results showed that morphological and yield characteristics were affected by the amount of water applied. The number of leaves remaining at the end of 21?weeks of growth was 65, 84, 93, 87 and 102 at 0.25, 0.50, 0.75, 1.00, and 1.25 AET. Root length and diameter increased with increasing irrigation. The greatest root length (66.5?cm) at 1.00 AET did not differ significantly from that at 1.25 AET (58.8?cm). The dry yield at 0.50, 0.75 and 1.00 AET showed an increased trend per plant in each treatment. Similarly, leaf crude protein showed a trend of increase with increasing irrigation although values were not significantly different between the levels of irrigation. The moisture content ranged from 60 to 63?% in leaves and 32?C35?% in branches across the five treatments. The analysis of water use efficiency showed that the 0.50 AET plants produced 2.6?kg?ha^?1?mm^?1 of dry forage compared to 1.8?kg?ha^?1?mm^?1 at 0.75 AET. The results showed that 0.50 or 0.75 AET represents the best irrigation level for L. leucocephala cultivation, producing a total dry yield of 0.68 and 0.72?t?ha^?1, respectively, in our study.     

Tree-grass relationships in open eucalypt woodlands of northeastern Australia: influence of trees on pasture productivity, forage quality and species distribution

Pasture yield, quality and species distributions were compared between zones around live and killed eucalypt trees at two woodland sites in northeast Queensland which differed markedly in soil fertility. Trees affected pasture quality and yield on an individual tree basis: N concentration and dry matter digestibility tended to be higher under trees than in inter-tree areas at both sites and pasture yields declined with distance from killed trees at the lower fertility site. However, the distribution of individual species did not vary markedly with distance from trees. Trees also affected pasture yield on a woodland basis: yields were greater where the trees were killed than under intact woodland. Soil under trees had higher levels of organic carbon and greater litter cover than soil in inter-tree areas. However, pasture yields did not generally reflect this fertility gradient since growth was limited by moisture availability due to drought conditions during the study period. Pasture N concentration was higher under trees that in inter-tree areas since plants under trees produced a similar amount of biomass as plants in inter-tree areas, but had access to higher nutrient levels. Trees appeared to have a greater effect on soil nutrient availability at the low fertility site. Live trees depressed pasture yields to a lesser degree at the low fertility site, demonstrating that the effects of trees on soil water availability (on a woodland scale) are less important when soil nutrients are more limiting to growth. These results indicate that, while removing trees may enhance pasture productivity, this benefit may be offset by a reduction in pasture quality. Given the beneficial effect of trees on soil nutrients, tree removal may also have longer term implications for soil nutrient dynamics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Germination and seedling growth of Quercus vulcanica: effects of stratification, desiccation, radicle pruning, and season of sowing

Effects of stratification, desiccation, radicle pruning, and season of sowing on Quercus vulcanica germination and growth were studied to identify optimum nursery procedures for artificial regeneration of this species. Following stratification (0, 2, 4 and 8 weeks), acorns were germinated, and acorn moisture content and germination performance were also determined at various times during desiccation. In early December unsprouted acorns were planted in containers, and in early April sprouted acorns, which had been stored in polyethylene bags at 4 °C, with radicles left intact or with radicles pruned back to 1.0 cm were planted in containers.Stratification for 2 and 4 weeks did not increase germination percentage but significantly increased germination rate. Germination percentage of the seeds dropped when the moisture content of the seeds was reduced by desiccation, and the critical minimum moisture content of the recalcitrant Q. vulcanica acorns was found to be 11–16%. Spring sowing of sprouted acorns altered the morphology the containerized seedlings and caused the formation of significantly more main roots, but resulted in significantly less shoot height and shoot dry weight. Spring-sown sprouted acorns had also a significant advantage over the fall-sown unsprouted acorns in seedling survival, and thus nursery personnel should not be concerned if acorns sprout before sowing.     

Transpiration increases during the dry season: patterns of tree water use in eucalypt open-forests of northern Australia

Australian savannas exhibit marked seasonality in precipitation, with more than 90% of the annual total falling between October and May. The dry season is characterized by declining soil water availability and high vapor pressure deficits (up to 2.5 kPa). We used heat pulse technology to measure whole-tree transpiration rates on a daily and seasonal basis for the two dominant eucalypts at a site near Darwin, Australia. Contrary to expectations, transpiration rates were higher during the dry season than during the wet season, largely because of increased evaporative demand and the exploitation of groundwater reserves by the trees. Transpiration rates exhibited a marked hysteresis in relation to vapor pressure deficit, which was more marked in the dry season than in the wet season. This result may be attributable to low soil hydraulic conductivity, or the use of stored stem water, or both. Tree water use was strongly correlated with leaf area and diameter at breast height and there were no differences in transpiration between the species studied. These results are discussed in relation to scaling tree water use to stand water use.     

Water loss regulation in mature Hevea brasiliensis: effects of intermittent drought in the rainy season and hydraulic regulation

Effects of soil and atmospheric drought on whole-tree transpiration (E(T)), leaf water potential (Ψ(L)) and whole-tree hydraulic conductance (K(T)) were investigated in mature rubber trees (Hevea brasiliensis, clone RRIM 600) during the full canopy stage in the rainy season in a drought-prone area of northeast Thailand. Under well-watered soil conditions, transpiration was tightly regulated in response to high evaporative demand, i.e., above reference evapotranspiration (ET(0)) ~2.2 mm day(-1) or maximum vapor pressure deficit ~1.8 kPa. When the trees experienced intermittent soil drought E(T) decreased sharply when relative extractable water in the top soil was?相似文献   

Yield, maturation, and forage quality of alfalfa in a black walnut alley-cropping practice

There is interest in producing alfalfa as an alley crop because alfalfa (Medicago sativa L.) is the most profitable hay crop in the USA. Field experiments were conducted near Stockton, MO in 2003 and 2004. Treatments consisted of alfalfa grown in open plots and in plots that were alley cropped between 20-year-old black walnut trees (Juglans nigra L.) planted in rows 24.4- and 12.2-m apart. Alfalfa was sampled for three harvest cycles each year. In the alley-cropping plots, samples were taken beneath the canopy (2.5 m from the tree row) and in the center of the alleys. Data were taken on dry-matter yield, maturity, and forage quality. At all harvest dates over both years, yields from beneath the canopy of both alleys and the narrow alley centers were less than yields from the wide alley centers and open plots. Yield from the wide alley centers was similar to that in open plots in every harvest but the final harvest of 2004. Transects across the plots indicated that yields increased linearly from the tree row to the center of both alleys. Alfalfa tended to mature faster in the open and wide alley centers compared to beneath the canopy of both alleys and the narrow alley centers. Forage quality differences were inconsistent across treatments. Alfalfa yield was significantly reduced and maturity was delayed by the narrow 12.2 m tree spacing, but yield was not reduced in the centers of the wider 24.4 m alleyways.     

西非Sudanian稀树草原森林在旱季火烧温度、持续时间及对种子萌发的影响

Prescribed fire is used in the Sudanian savanna-woodland of West Africa as a forest management tool. An experiment was carried out to assess the effects of season of burning, and different vertical probe positions on maximum fire temperature and temperature residence time above 60°C which is considered lethal for plant tissues. Seasons of burning considered were: an early season fire set at the beginning of the dry season (beginning of December), mid-season fire set at the peak of the dry season (mid-January), and a late season fire at the end of the dry season (end of March). The effects of these fires on the germination of buried seeds of three socio-economically valuable tree species were also examined. Results indicated significant differences in maximum fire temperature and residence time with respect to season of burning and vertical probe position (p < 0.001). The highest and longest lasting temperatures were observed at 20 cm above ground during early fire and at the soil surface during mid-season and late fires. This, in turn, affected germination responses of seeds buried at different soil depths. Implications of these findings in the current management practices are discussed.     

Growth, productivity and quality of Megathyrsus maximus under cover from Gliricidia sepium

The effect of tree canopy on the growth, productivity and forage quality of Megathyrsus maximus and changes in soil properties were evaluated over three seasonal periods. Four adjacent plots (15 m × 17 m each) in a tropical secondary deciduous forest having 12 years of growth and dominated by Gliricidia sepium were randomly assigned to two treatments: removal of trees (SCA) in two of the plots and leaving trees intact (COA) in the other two. In all plots, M. maximus was planted with 50 cm spacing among plants. Tree removal significantly increased the incident photosynthetically active radiation (PAR, P < 0.001) and grass size (12.5 % in height, P < 0.01, and 16.5 % in clump diameter, P < 0.05), but did not significantly affect any other variable. Season significantly affected grass height (P < 0.003), tiller number (P < 0.001), clump diameter (P < 0.001), net CO₂ assimilation rate (P < 0.001), forage biomass production (P < 0.003), and acid detergent fiber content (P = 0.033). Primary soil changes after 1 year of establishment of the grass were the decline by 3 % in organic carbon (P = 0.03), and qualitative changes in soil structure, regardless of tree presence. Results are consistent with the ability of M. maximus to tolerate shade. We conclude that under the conditions of the study there was no evidence for a negative effect of tree canopy on M. maximus mediated by a reduction in PAR.     

Soil nutrient availability and CO2 production in agroforestry systems after the addition of Erythrina poeppigiana pruning residues and native microbial inocula

To investigate the effects of microbial inocula and Erythrina poeppigiana pruning residues on soil K, NO^3?, and NH⁴⁺ concentrations, a greenhouse trial, a field experiment in an organic farm, and three in vitro tests were conducted. Under controlled conditions, weak, temporary effects (10 %) on maize seedling growth were observed on poor soils (taken from the 10–20 cm layer) in the first 2 weeks after application. Positive effects of pruning residue applications on soil K levels (0.09 cmol kg^?1, on average) were detected in both the field and greenhouse study. However, significant effects due to the addition of microbial inocula on soil K concentrations were not detected in the field; thus, microbial applications were ineffective at enhancing nutrient availability under field conditions. In contrast, in the in vitro experiments, CO₂ production was 31 % greater than that of untreated soil on the 8th and 15th days of incubation. These results highlight the importance of adding tree pruning residues to support coffee-plant nutrition. Experimental outcome data could be valuable for further studies focused on microbial application dosage and timing.     

Scion-rootstock interaction affects the physiology and fruit quality of sweet cherry

Water relations, leaf gas exchange, chlorophyll a fluorescence, light canopy transmittance, leaf photosynthetic pigments and metabolites and fruit quality indices of cherry cultivars 'Burlat', 'Summit' and 'Van' growing on five rootstocks with differing size-controlling potentials that decrease in the order: Prunus avium L. > CAB 11E > Maxma 14 > Gisela 5 > Edabriz, were studied during 2002 and 2003. Rootstock genotype affected all physiological parameters. Cherry cultivars grafted on invigorating rootstocks had higher values of midday stem water potential (Psi(MD)), net CO(2) assimilation rate (A), stomatal conductance (g(s)), intercellular CO(2) concentration (C(i)) and maximum photochemical efficiency of photosystem II (PSII) (F(v)/F(m)) than cultivars grafted on dwarfing rootstocks. The Psi(MD) was positively correlated with A, g(s) and C(i). Moreover, A was positively correlated with g(s), and the slopes of the linear regression increased from invigorating to dwarfing rootstocks, indicating a stronger regulation of photosynthesis by stomatal aperture in trees on dwarfing Edabriz and Gisela 5. The effect of rootstock genotype was also statistically significant for leaf photosynthetic pigments, whereas metabolite concentrations and fruit physicochemical characteristics were more dependent on cultivar genotype. Among cultivars, 'Burlat' leaves had the lowest concentrations of photosynthetic pigments, but were richest in total soluble sugars, starch and total phenols. Compared with the other cultivars, 'Summit' had heavier fruits, independent of the rootstock. 'Burlat' cherries were less firm and had lower concentrations of soluble sugars and a lower titratable acidity than 'Van' cherries. Nevertheless, 'Van' cherries had lower lightness, chroma and hue angle, representing redder and darker cherries, compared with 'Summit' fruits. In general, Psi(MD) was positively correlated with fruit mass and A was negatively correlated with lightness and chroma. These results demonstrate that: (1) water relations and photosynthesis of sweet cherry tree are mainly influenced by the rootstock genotype; (2) different physicochemical characteristics observed in cherries of the three cultivars suggest that regulation of fruit quality was mainly dependent on the cultivar genotype, although the different size-controlling rootstocks also had a significant effect.     

Water relations balance parameters of 30 woody species from Cerrado vegetation in the wet and dry season

IntroductionThehigherplantsmaintainingtheirorganstobetur-gidareveryimportantmechanism,inwhichtheaII-physiologicalprocesscouIdfonctionnorma1IyundertheIimitedWaerstress(MeinzeretaI1986).TheseasonadjustmentinWaterrelationofwoodyspeci-esottenoccursrespondingtothechangingenvi-ronmentaIconditionsinoFdertomaintainasoil-to-IeafwaterpotentiaIgradientandlowerthewiltingpointbyextendingtherangeofpositiveturgid(Ku-biske&Abrams1991).AlthoughtherewereaIOtofargumentsonthewaterreIationinpastdecades,pIa…     

控根对苦楝苗木质量的影响

容器苗根系畸形现象比较严重,采取一定的控根技术可有效改善根系分布,增加侧根数量,提高容器苗质量。试验选用不同控根方法对苦楝苗木进行容器育苗对比试验,阐明了不同控根方法对苦楝苗木质量的影响规律。结果表明,空气修根效果显著,特别是空气控根和化学控根结合的方法处理的苗木其根系成团现象比较明显,侧根数、根系活力等指标与其他处理间均达极显著差异。化学控根采用碳酸铜浓度为100～150 g/L时培育出的苗木质量最好。     

不同修剪方法对金丝小枣生长、结果和品质的影响

献县现有金丝小枣树33400hm^2，由于枣农修剪树形不规范，留枝量过多，光照条件严重恶化，致使炭疽病、轮纹病等病害连年大发生，红枣产量和品质明显下降，亟需通过树体改造来提高果实品质。试验设疏散分层形、开心形、自然圆头形3种修剪树形。试验结果表明：开心形比其它2种树形果实个大、均匀、颜色紫红、光亮，浆烂果少且轻，修剪后各项生长指标以开心形为最好，疏散分层形次之，自然圆头形最差。     

Low light availability affects leaf gas exchange,growth and survival of Euterpe edulis seedlings transplanted into the understory of an anthropic tropical rainforest

Euterpe edulis Mart. (Arecaceae) is a threatened palm tree of the Brazilian Atlantic Rainforest understory with fundamental importance for the restoration of degraded forest environments. We assessed the leaf gas exchange, growth and survival of E. edulis seedlings transplanted at three different forest sites (S1, S2 and S3) in the same area in which cocoa trees had been cultivated in a rustic agroforestry system. Measurement was carried out during the first year after seedling transplantation. The sites were characterised according to canopy openness (CO) and total daily photosynthetic photon flux density (PPFD). Average CO and PPFD values were 13.3%, 8.0% and 6.7%, and 3.34, 2.79 and 0.62 mol m^?2 d^?1 for S1, S2 and S3, respectively. A progressive decline in seedling survival was observed in all sites throughout the experiment. At 387 d after planting, survival at S1, S2 and S3 was 57%, 44% and 37%, respectively. The gross light-saturated photosynthetic rate (A_max), leaf area and plant biomass were significantly higher (P < 0.05) in S1 and S2 when compared with S3. The values of dark respiration rate (R _d) and photosynthetic compensation irradiance (I _c) were sufficiently low for a positive carbon balance. Notwithstanding, the interpretation of results of microclimate variables together with leaf gas exchange and growth variables indicated that seedlings at all sites were in a suboptimal condition to achieve A_max, which is probably the main cause of the dramatic decline in the seedlings’ survival throughout the first year after transplantation. From a practical point of view, if the values of CO and PFD are lower than 10% and 3 mol m^?2 d^?1, respectively, it is suggested that the transplanting of E. edulis seedlings to the understory of abandoned agroforestry systems be accompanied by cultural practices, such as the thinning and pruning of tree tops.     

Nursery fertilisation affects the frost-tolerance and plant quality of Eucalyptus globulus Labill. cuttings

Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 °C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality.     

Growth,stem quality and nutritional status of Betula pendula and Betula pubescens in pure stands and mixtures

The growth, technical quality and nutritional status of pure and mixed silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) plantations were studied 21 and 22 years after planting on afforested organic soil arable land and on upland forest soil. In mixtures, 50% of both birch species was planted. Silver birch trees grew better, but had higher mortality than downy birch trees on both sites. Mortality of both species was highest, and the difference in their growth smallest, on organic soil. In pure stands on organic soil, downy birch dominant height, diameter and mean volume were 96%, 92% and 82% of those of silver birch and on mineral soil 87%, 84% and 60%, correspondingly. On mineral soil, silver birch had a higher mean annual increment (MAI) (5.8 m³ ha^?1a^?1) than downy birch (3.9 m³ ha^?1a^?1), but on organic soil the MAI of both species was similar (3.3–3.4 m³ ha^?1 a^?1). Planting birches in mixture did not affect the growth of the trees on organic soil. On mineral soil, the mean diameter and mean volume of silver birch trees were higher in mixed than in pure plantations. The technical stem quality of both tree species was low. On mineral soils, pure silver birch is more productive than mixture, but on peat soil the higher growth of silver birch could contribute to increased productivity and downy birch would ensure sufficient survival for future timber production.     

Growth, allocation and tissue chemistry of Picea abies seedlings affected by nutrient supply during the second growing season

One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites.     

修枝对杉木生长、林下光照及植被的影响

设置3个年度修枝高度至6、5、4 m和不修枝A、B、C、D(CK)四个处理,研究修枝对立木生长、林下光照及植被的影响。结果表明:修枝对杉木生长无显著影响,处理A、 B、C与对照比,树高增益分别为-1.05、-0.62、-0.43个百分点,胸径增益分别为-1.05、-0.16、0.22个百分点,材积增益分别为-2.50、-1.60、1.40个百分点,波动范围极小。不同强度修枝林冠下光照率存在极显著差异,处理A、 B、C分别比不修枝提高25.30、13.39、7.30个百分点。不同强度修枝林下植被种类及鲜重也存在极显著差异,与对照比,处理A、B、C植被种类分别增多275%、250%、200%,植被鲜重分别增加483%、428%、386%。     

Diurnal and seasonal variations in carbon fluxes in bamboo forests during the growing season in Zhejiang province,China

Bamboo forest is an important forest type in subtropical China and is characterized by fast growth and high carbon sequestration capacity. However, the dynamics of carbon fluxes during the fast growing period of bamboo shoots and their correlation with environment factors are poorly understood. We measured carbon dioxide exchange and climate variables using open-path eddy covariance methods during the 2011 growing season in a Moso bamboo forest(MB, Phyllostchys edulis) and a Lei bamboo forest(LB, Phyllostachys violascens) in Zhejiang province,China. The bamboo forests were carbon sinks during the growing season. The minimum diurnal net ecosystem exchange(NEE) at MB and LB sites were-0.64 and-0.66 mg C m^-2 s^-1, respectively. The minimum monthly NEE, ecosystem respiration(RE), and gross ecosystem exchange(GEE) were-99.3 ± 4.03, 76.2 ±2.46, and^-191.5 ± 4.98 g C m^-2 month^-1, respectively,at MB site, compared with-31.8 ± 3.44, 70.4 ± 1.41,and^-157.9 ± 4.86 g C m^-2 month^-1, respectively, at LB site. Maximum RE was 92.1 ± 1.32 g C m^-2 month^-1 at MB site and 151.0 ± 2.38 g C m^-2 month^-1 at LB site.Key control factors varied by month during the growing season, but across the whole growing season, NEE and GEE at both sites showed similar trends in sensitivities to photosynthetic active radiation and vapor pressure deficit,and air temperature had the strongest correlation with RE at both sites. Carbon fluxes at LB site were more sensitive to soil water content compared to those at MB site. Both onyear(years when many new shoots are produced) and offyear(years when none or few new shoots are produced)should be studied in bamboo forests to better understand their role in global carbon cycling.