氮素营养对长白落叶松移植苗生长及养分状况的影响

尽管少数研究认为造林效果与苗木体内氮含量无关甚至负相关(Gleason et al.,1990;Boinvin et al.,2004),更多的研究表明初始氮含量与造林效果呈正相关,如蓝桉(Eucalyptus globulus)高、低氮处     

接种AM菌对麻楝不同种源苗期的生长效应

研究接种3个AM菌株对5个种源麻楝幼苗生长的影响,结果表明:菌株90068×种源CH01菌根感染率为96.3%,感染率分级为5,菌根依赖性中等;菌株90068×种源CH27在生长生物量方面作用显著;麻楝幼苗接种5至6个月后,菌株90068×种源CH01生长促进作用显著增强;矿质元素吸收方面,菌株90068×种源CH13对磷元素的吸收显著高于其他接种处理.此外,菌株90036与菌株9004在接种后幼苗测定的各项指标中表现各有优劣.其中菌根合成、生物量和苗高增长方面,菌株9004优于菌株90036;而对于矿质元素的吸收,菌株90036要优于菌株9004.综合比较而言,供试菌株90068表现较优,为对5个种源麻楝幼苗生长效应最佳的菌株.     

Sitka spruce site index in response to varying soil moisture and nutrients in three different climate regions in Ireland

We examined the relationships between Sitka spruce (Picea sitchensis (Bong.) Carr.) site index, windspeed, former land use, soil moisture and soil nutrients with a view to identifying factors limiting the growth potential of the species in three climate regions in Ireland. We selected plantations covering three climate regions (delineated on the basis of ‘growing season’ balance of precipitation and potential evapotranspiration; representing dry, moist and wet climate regions) located on sites representing the range of soil moisture regimes (SMR), soil nutrient regimes (SNR), and land use types found throughout Ireland. Site index of Sitka spruce varied among climate region, with significantly lower site index associated with the wet climate region mainly due to the deterioration in edaphic conditions and adverse climatic conditions. The effect of edaphic variables (SMR, SNR) on site index was consistent across climate regions, site index increasing with increasing SNR, and decreasing with excess moisture or moisture deficit. Site index reached a maximum on fresh/very rich sites in the dry and moist climate regions and on moist/rich sites in the wet climate region. In the dry climate region, water supply (SMR) was the most important variable regulating growth, in wetter windier climates nutrient supply (SNR) was the most important factor, accounting for 69% of the variation in site index. The study has allowed region-specific recommendations to be made for successful plantation establishment in Ireland and for countries with similar climatic regions.     

Intensive tree planting facilitates tropical forest biodiversity and biomass accumulation in Kibale National Park, Uganda

The extensive area of degraded tropical land and the calls to conserve forest biodiversity and sequester carbon to offset climate change demonstrate the need to restore forest in the tropics. Deforested land is sometimes replanted with fast-growing trees; however, the consequences of intensive replanting on biomass accumulation or plant and animal diversity are poorly understood. The purpose of this study was to determine how intensive replanting affected tropical forest regeneration and biomass accumulation over ten years. We studied reforested sites in Kibale National Park, Uganda, that were degraded in the 1970s and replanted with five native tree species in 1995. We identified and measured the size of planted versus naturally regenerating trees, and felled and weighed matched trees outside the park to calculate region-specific allometric equations for above-ground tree biomass. The role of shrubs and grasses in facilitating or hindering the establishment of trees was evaluated by correlating observed estimates of percent cover to tree biomass. We found 39 tree species naturally regenerating in the restored area in addition to the five originally planted species. Biomass was much higher for planted (15,675 kg/ha) than naturally regenerated trees (4560 kg/ha), but naturally regenerating tree regrowth was an important element of the landscape. The establishment of tree seedlings initially appeared to be facilitated by shrubs, primarily Acanthus pubescens and the invasive Lantana camara; however, both are expected to hinder tree recruitment in the long-term. Large and small-seeded tree species were found in the replanted area, indicating that bird and mammal dispersers contributed to natural forest restoration. These results demonstrate that intensive replanting can accelerate the natural accumulation of biomass and biodiversity and facilitate the restoration of tropical forest communities. However, the long-term financial costs and ecological benefits of planting and maintaining reforested areas need to be weighed against other potential restoration strategies.     

湘西南山地主要森林类型土壤养分研究

对湘西南永州市6种主要森林类型(针阔混交林、阔叶林、湿地松林、马尾松林、毛竹林和杉木林)林地的土壤养分进行测定与分析,结果表明:针阔混交林和毛竹林的土壤有机质含量较高;针阔混交林的氮、钾元素含量高,而磷元素含量相对较低;毛竹林的速效磷含量最高;阔叶林钾、磷元素含量较高,氮元素含量相对较低;湿地松和马尾松纯林的土壤有机质...     

猕猴桃对硒的吸收、分布、积累特性的研究

大田条件下,给中华猕猴桃施以浓度分别为0．15、0．3、0．5mg／培的Na：SeO,溶液,在盛花期每30d测定果实和叶对硒的积累情况;果实成熟期测定猕猴桃各部位含硒量以及鲜重、可溶性糖含量、可溶固形物和Vc含量;结果显示：施硒后,猕猴桃各部分含硒量显著升高,并且硒在猕猴桃中累计顺序为根〉叶〉花〉果实。果实鲜重、可溶性糖含量、可溶固形物和％含量随着硒浓度的增大而升高,然而在高浓度的硒（≥0．5rag／kg）水平下,受到不同程度的抑制。施硒显著提高了猕猴桃对硒的吸收、分布、积累和改善了果实的品质。     

丘塘景观植被恢复与土壤养分空间分异规律研究

丘塘景观是一种生态经济结构较为优化的人工复合生态系统。根据在丘塘景观内不同斑块的土壤调查，研究土壤养分的分异规律，为退化丘塘景观的恢复提供理论依据，并且对于水肥的调配和植被的恢复都有重要的意义。结果表明：土壤有机质含量的变化是随着土壤深度增加而减少的，全氮的变化趋势同有机质一样，随土壤深度增加而递减。土壤全磷并没有遵循此规律，基本上各个不同斑块土层10～20 cm含量都大于其他土层。不同斑块表层变异系数最小，往生层基本呈现上升趋势。土壤养分水平空间变异为0～10 cm土层土壤有机质和全氮平均含量分布为：林带>果园>草地>鱼塘，全磷平均含量分布是果园>林带>草地>鱼塘。通过比较造林前(1986年)和造林后(2002年)的土壤养分结果表明马占相思林对下层土壤有显著的影响，土壤有机碳和全氮含量大大提高。     

不同供磷状况下CO2浓度升高对番茄根系生长及养分吸收的影响

采用培养试验研究了磷缺乏与正常供磷条件下,CO₂浓度由350μL/L升高至800μL/L苗期番茄的生物量、根系特征和不同器官N、P、K养分含量的变化。结果表明,无论缺磷与否,CO₂浓度升高均能显著增加番茄地上部及根系的干物质积累量,提高根冠比。在磷缺乏条件下,CO₂浓度升高对番茄根系生长的促进主要表现为增加根系的体积和表面积;而在磷正常供应条件下主要表现为同时增加根体积和分根数,有利于形成强壮的根系。在两种供磷水平下,CO₂浓度升高对番茄各器官的N、P、K含量产生不同的稀释效应,但N、P、K总积累量却随CO₂浓度升高而显著增加;而且CO₂浓度与供P水平对番茄植株的N、P、K积累量具有极显著的正交互效应。     

Potassium Dynamics in US Coastal Plain Soils

ABSTRACT

Potassium (K) deficiency in crops in southern US Coastal Plain soils has been documented since the l880s. Long-term soil fertility studies such as Alabama’s “Cullars Rotation” experiment (circa 1911) have been conducted with K since 1911. Other Alabama long-term experiments on several Coastal Plain and related Hapludults, Paleudults, and Kandiudults also contain K variable treatments which have been monitored since 1929. Soil test data from these long-term experiments have allowed us to answer some practical questions regarding K dynamics in Coastal Plain soils. Potassium movement through the soil profile is dependent on the soil’s cation exchange capacity (CEC) but relative accumulation is greater in the plow layer regardless of soil CEC. While subsoil K testing may be useful for identifying situations where subsoil K has been depleted, this extra effort and expense is not necessary for most cropping situations. A crop will remove most of its K from the plow layer if it is present in sufficient quantity based on soil test. Crop depletion of plow-layer K to the point where yield may be reduced is gradual and may take 10–15 years or more depending upon soil CEC and initial soil K concentration. Depletion is most rapid in low CEC soils as would be expected. However, soil test K can vary considerably during the course of a crop season with the lowest soil test K concentrations occurring immediately after harvest.     

Effects of NaCl salinity on some leaf nutrient concentrations,non-photochemical quenching and the efficiency of the PSII photochemistry of two Iranian pomegranate varieties under greenhouse and field conditions: Preliminary results

The present research was conducted to study the responses of ‘Malas–e–Saveh’ (M) and ‘Shishe–Kab’ (Sh) Iranian pomegranates to sodium chloride (NaCl) stress under greenhouse and field conditions. Treatments included waters electrical conductivity (EC = 1.5, 3, 6, 9 and 12 dS m^?1 for greenhouse) and (EC = 1.05 as control, 4.61 and 7.46 dS m^?1 for field studies). Interactive effects of salinity × variety indicated the highest chlorophyll and leaf potassium concentration, and the lowest leaf chloride and sodium in control under greenhouse study. Non-photochemical quenching, effective quantum yield of photochemical energy conversion in PSII reduced under the highest salinity level in field, however, basal quantum yield of non-photochemical processes in PSII increased in the highest salinity. Sodium and chloride increased with increased in salinity. Calcium, magnesium and iron significantly decreased with increased in salinity. It seems that there are differences between pomegranate cultivars and Malas-e-Saveh is more tolerant compared with Shishe Kab.