Biomass dynamics of Erythrina lanceolata as influenced by shoot-pruning intensity in Costa Rica     

Berninger Frank  Salas Eduardo 《Agroforestry Systems》2003,57(1):19-28

Pruning of agroforestry trees, while reducing shade of the crops, usually reduces both biomass production and nitrogen fixation. Short pruning cycles are often not sustainable on the long run, because tree production declines over subsequent pruning cycles. We compared biomass and labile carbohydrate dynamics of Erythrina lanceolata Standley (Papilionaceae) shade trees under total and partial pruning regimes in a vanilla (Vanilla planifolia L.) plantation in South-western Costa Rica. The highest biomass production was measured in the unpruned control, followed by trees with 50% of the leaf pruned every three months, while total pruning every six months resulted in the lowest biomass pruduction. In the more productive treatments, a higher proportion of the production was in branches. Because, the N content of woody branches was high, they were important for nitrogen cycling. In the partial pruning treatment more nitrogen was returned to the soil from litter and woody branches than from pruned leaf. Sugar concentrations were not different between treatments and the dynamics of non-structural carbohydrates (sugar and starch) seems to depend more on plant phenology than pruning treatment. However, the starch concentrations in the total pruning were lower than in the other treatments.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

Effects of different soil treatments on growth and net nitrogen uptake of newly planted Picea abies (L.) Karst. seedlings     

Fredrik Nordborg  Urban Nilsson  Gran rlander 《Forest Ecology and Management》2003,180(1-3):571-582

Five soil treatments in a 4-year-old clearcut in southern Sweden affected biomass increase and net nitrogen uptake by planted Norway spruce (Picea abies (L.) Karst.) seedlings through their on net mineralisation and root growth. The patch soil treatments studied were: (i) soil inversion in an old clearcut; (ii) mineral soil from the clearcut remaining, (iii) mineral soil from the clearcut with fertiliser application during the first season; (iv) mineral soil from a nearby uncut forest replacing the clearcut mineral soil; and (v) an untreated control. Growth increased in seedlings in treatments (i) and (iii), but growth in soil treatments with humus removal was not better than that of seedlings in untreated soil. High N uptake early in the first growing season resulted in increased growth during this season in contrast to late N uptake that resulted in a high N concentration in the seedlings after the first growing season. This in turn led to a high growth rate during the next growing season. Generally, both root growth and net N mineralisation were positively correlated to N uptake in the soil treatments. Therefore, a combination of low net N mineralisation and poor root growth as a result of high soil density appears to explain the low N uptake in seedlings in undisturbed soil. The importance of competition with field vegetation for N and water was not clear. Net mineralisation was larger in soil treatments where the humus layer was retained than where it was removed. Net N mineralisation in soil from old clearcuts was the same as in soil from fresh clearcuts.  相似文献   

Decomposition of needle/leaf litter from Scots pine, black cherry, common oak and European beech at a conurbation forest site     

Klaus Lorenz  Caroline M. Preston  Susan Krumrei  Karl-Heinz Feger 《European Journal of Forest Research》2004,123(3):177-188

Litter decomposition was studied for 2 years in a mixed forest serving as a water protection area (Rhine-Neckar conurbation, SW Germany). Two experiments differing in initial dry weight equivalent in litterbags were set up: one to compare decomposition of European beech leaves (Fagus sylvatica) with common oak leaves (Quercus robur), and the other comparing decomposition of Scots pine needles (Pinus sylvestris) with black cherry leaves (Prunus serotina Ehrh.), respectively. Mass losses were greater for oak litter than for beech (75.0 versus 34.6%), and for cherry litter than for pine (94.6 versus 68.3%). In both experiments, a strong initial loss of soluble compounds occurred. The changes in litter N and P concentrations and the decrease in C-to-N ratio coincided with changes in residual mass. However, neither tannin and phenolic concentrations nor NMR could explain the pronounced variation in mass loss after 2 years. Differences in litter palatability and toughness, nutrient contents and other organic compounds may be responsible for the considerable differences in residual mass between litter types. The fast decay of black cherry leaves appears to play a major role in the present humus dynamics at the studied site. Since black cherry has a high N demand, which is mainly met by root uptake from the forest floor, this species is crucial for internal N cycling at this conurbation forest site. These effects together may significantly contribute to prevent nitrate leaching from the forest ecosystem which is subject to a continuous N deposition on an elevated level.  相似文献   

Soil properties and nitrogen availability in silvopastoral plantings of Acacia melanoxylon in North Island, New Zealand     

I.L. Power  B.S. Thorrold  M.R. Balks 《Agroforestry Systems》2003,57(3):225-237

Acacia melanoxylon, a N₂-fixing timber tree occurring naturally in eastern Australia, is now promoted as a component of silvopastoral systems; but the interaction of the tree with pasture and soils has not been adequately studied. This study investigated the effects of Acacia melanoxylon on soil nitrogen (N) levels, N availability, soil pH, bulk density, organic carbon, C:N ratios and soil moisture in three separate silvopastoral sites with contrasting soil types in the North Island of New Zealand. At each site four tree stocking rates were studied (0, 500, 800, and 1700 stems ha^–1). The trees were nine years old at the time of the study. Soil samples from each study site were taken once at three depths (0 to 75 mm, 75 to 150 mm, and 150 to 300 mm), with three replicates per tree stocking rate. Soil analyses showed that although there were differences between soil types, few statistically significant differences occurred due to tree stocking rate. A greenhouse pot trial growing ryegrass (Lolium multiflorum L. cv. Concord) in soil from the A horizon of each soil type from under the trees and the open pasture found that ryegrass yield, N uptake and N supply increased with increasing tree stocking rate. Increased N supply under the trees, coupled with greater soil moisture compared to the open pasture may have accounted for the higher pasture yield under Acacia melanoxylon compared to non dinitrogen fixing tree species. This study suggested that Acacia melanoxylon in a silvopastoral system had the potential to increase soil N availability.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

Effects of chronic acid fog exposure with soil acidification or nitrogen loading on nutrient status in Abies firma seedlings     

Koji Yoshida  Shoko Inaba  Chisato Takenaka  Takafumi Tezuka 《Journal of Forest Research》2005,10(2):157-161

To clarify the nutrient status in momi fir (Abies firma Sieb. et Zucc.) seedlings under complex stress conditions of acid fog with soil acidification or nitrogen loading, we exposed seedling shoots to simulated acid fog (pH 3) and simultaneously loaded the soil with acid or excess nitrogen for 17 months. Proton and nitrogen loading reduced K concentration in soil, but these treatments had little effect on the nutrient status of fine roots in momi fir seedlings. Acid fog exposure resulted in reduced concentrations of Mg, Al, and Fe in current-year needles and Mg, Al, Cu, Fe, and Zn in 1-year-old needles. The complex effects of acid fog exposure with proton or nitrogen loading on nutrient status were relatively slight. However, elements such as Al and Cu notably reflect the effects of proton loading. These results show that the nutrient status of trace elements, rather than major elements, in needles of momi fir seedlings is sensitive to exposure to acid fog or proton loading.  相似文献   

Effects of VA mycorrhizae and Frankia dual inoculation on growth and nitrogen fixation of Hippophae tibetana     

Chunjie Tian  Xingyuan He  Yang Zhong  Jiakuan Chen 《Forest Ecology and Management》2002,170(1-3):307-312

Through biological inoculation technology, the joint symbiosis of Tibetan seabuckthorn (Hippophae tibetana) in pure culture was identified and the effects of dual inoculation with Frankia and mycorrhizal fungi on the host plants in pot cultures were investigated. The results obtained from the comparative study showed that H. tibetana could form nodules and VA mycorrhiza both in pot and pure cultures. VA mycorrhizae and Frankia can stimulate the growth and the nitrogen fixation ability of host plants, respectively, yet the stimulation of the dual inoculation on the growth and nitrogen fixation ability of the host plants was more significant (p<0.05): stronger nitrogen-fixing ability, higher VA mycorrhizal development and better growth of seedlings in VAH and HR16 dual inoculation.  相似文献   

Short fallows of Tithonia diversifolia and Crotalaria grahamiana for soil fertility improvement in western Kenya     

B. Thor Smestad  H. Tiessen  R.J. Buresh 《Agroforestry Systems》2002,55(3):181-194

Managed short-duration fallows may have the potential to replace longer fallows in regions where population density no longer permits slow natural fallow successions. The purpose of fallows is not only to improve subsequent crop performance but also to restore soil fertility and organic matter content for the long term. We therefore evaluated the soil organic matter and nutrient flows and fractions in a short fallow experiment managed in the western Kenya highlands, and also compared the experimental area with a 9–12-yr-oldadjacent natural bush fallow. The factorial agroforestry field experiment with four land-use and two P fertilizer treatments on a Kandiudalfic Eutrudox showed that 31-wk managed fallows with Tithonia diversifolia(Hemsley) A. Gray and Crotalaria grahamiana Wight &Arn. improved soil fertility and organic matter content above those of a natural weed fallow and continuous maize (Zea mays L.). Post-fallow maize yields were also improved, although cumulative three-season increases in yield were small (0–1.2 Mg ha⁻¹) when the yield foregone during the fallow season was accounted for. Improvements in yield and soil quality could be traced to quantity or quality of biomass recycled by the managed fallows. The non-woody recycled biomass produced by the continuous maize, weed fallow, and tithonia treatments was near 2Mg ha⁻¹, whereas crotalaria produced three times more recyclable biomass and associated N and P. Increases in topsoil N due to the fallows may have been attributable in part to deep acquisition and recycling of N by the fallows. Particulate macro-organic matter produced by the fallows contained sufficient N(30–50 kg ha⁻¹) to contribute substantially to maize production. Organic Paccumulation (29 kg ha⁻¹) similarly may play a significant role in crop nutrition upon subsequent mineralization. The effect of the P fertilizer application on soil properties and maize yield was constant for all land-use systems (i.e., no land-use system × P fertilizer interactions occurred). There was an indication that tithonia may have stimulated infestation of Striga hermonthica (Del.) Benth., and care must be taken to evaluate the full effects of managed fallows over several seasons. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

供磷水平对‘热研5号'柱花草-根瘤菌共生体系的影响     

董荣书  张洁  王文强  黄艳霞  白昌军  郇恒福  刘国道 《草地学报》2015,23(1):211-214

为研究不同供磷水平对热研5号柱花草(Stylosanthes guianensis‘Reyan No.5')-根瘤菌共生体系的影响,利用水培试验对接种7株不同根瘤菌的柱花草进行3个磷浓度的处理,通过对柱花草干重、植株含氮量、根瘤数、固氮酶活性的测定及分析确定磷对共生体系的影响。结果表明:低磷不利于柱花草及根瘤菌共生体系的生长;菌株YM11-1,FS3-1-1在高磷时固氮促生效果最佳,菌株LZ3 2,RJS9-2,BS1-1,CJ1则在中等磷条件下固氮促生效果最佳,磷对菌株PN13-3的影响不大。  相似文献   

脲酶/硝化抑制剂配施氮肥对春玉米农田氨排放的影响     

王甄烨  焉莉  蒋富琛  田洪涛  王少杰  高强  冯国忠 《玉米科学》2022,30(1):138-143

通过两年田间定位试验,探讨脲酶/硝化抑制剂配施氮肥在黑土区玉米体系中的氨减排及氮素增效效果.设置两种耕作模式(条耕和旋耕)和3种氮肥类型(常规尿素、添加脲酶抑制剂尿素、添加硝化抑制剂尿素).结果 表明,条耕产量和氮素利用率分别为8631 kg/hm2和33.4％,明显低于旋耕;氨挥发总量为20.6 kg/hm2,明显高...  相似文献   

不同铵硝配比对辣椒产量、养分积累和氮肥利用率的影响     

袁嫚嫚  邬刚  王家宝  井玉丹  张祥明  王文军  陈俊阳  孙义祥 《中国瓜菜》2022,(2):43-48

通过设施大棚辣椒盆栽试验,设置不施氮肥(CK)、铵态氮与硝态氮的氮质量比分别为0:100(A0N100)、25:75(A25N75)、50:50(A50N50)、100:0(A100N0)5个处理,研究不同铵硝态氮配比对辣椒产量、养分积累和氮肥利用率的影响.结果表明,与CK相比,不同铵硝配比处理增加了辣椒的果实数、鲜果...  相似文献