松嫩平原盐碱化草地生态系统的模拟研究

利用面向对象技术及新型编程语言JAVA,建立了物理过程模型来模拟土壤水分、盐化／脱盐过程和碱化／脱碱过程。在此基础上建立了基于过程的模型并分别模拟了以羊草（Aneurolepidium chinese (Trin.)Kitag.）、虎尾草（Chloris virgata Sw.）、星星草（Puccinellia tenuiflora(Turcz.)Scribn.et Merr.）和碱蓬（Suaeda glauca Bunge）为建群种的4种植物群落的地上生物量、地下生物量以及枯死生物量的变化动态。模型以1d为步长,适合于模拟异质性强的土训水盐动态和多种植物群落的生长动态。利用吉林省长岭的气修资料和试验资料,模拟了1991、1996、1997、1998年土壤湿度动态,1991年4种植物群落土壤盐分、碱化度和pH值变化动态,以及1991年4种群落生长动态,并分别利用实验资料进行了验证,模拟效果非常理想。     

Loss and degradation of wetlands in southwestern Australia: underlying causes,consequences and solutions

Many wetlands (estimated to be about 70%) have been lost in the coastal plain region of southwestern Australia since British settlement (in 1829), primarily as a result of infilling or drainage to create land for agricultural use or urban development. While further loss is almost universally acknowledged as undesirable, wetland degradation continues with little overt public recognition of the causes or consequences. Obvious and direct causes include nutrient enrichment, salinization, pollution with pesticides and heavy metals, the invasion of exotic flora and flora, loss of fringing vegetation and altered hydrological regimes occurring as a result of urbanization and agricultural practices. Underlying causes include a lack of understanding of wetland hydrology and ecology on behalf of both planning agencies and the private sector, and poor coordination of the many different agencies responsible for wetland management. Public and political awareness of wetland values continues to increase, but sectoral organization and responsibilities for wetland management lag behind. Sufficient scientific information now exists for improved management, protection and restoration of wetlands in southwestern Australia. However, this improvement cannot occur without the necessary political will and corresponding sectoral responses needed to implement coordinated wetland management policies and actions.     

干旱、半干旱区湖泊周围盐生植物群落的多样性格局及特点

干旱、半干旱地区湖泊周围是盐渍化土壤的主要分布区,盐渍化是荒漠化的主要类型之一。目前,关于盐生植被的分布格局及群落多样性随着盐渍化程度加深的动态变化的研究仍很缺乏, 为阐释这种关系,作者在内蒙古干旱、半干旱地区选择吉兰泰(盐池)、乌梁素海、查干诺尔(碱矿)以及额吉诺尔(盐池)等4个湖泊,研究了其周围盐生植物群落的物种组成、分布特征以及群落结构的差异, 讨论了群落多样性沿盐分梯度的变化特点, 并在此基础上探讨了盐生植物群落对土壤盐分环境的指示意义。为建立群落耐盐值与群落多样性的关系,我们计算了群落耐盐值。结果表明, 盐生植物群落沿盐湖呈明显的环带状分布;随着土壤盐渍化程度的增加, 按照芨芨草群落(Comm. Achnatherum splendens)、盐爪爪群落(Comm. Kalidium foliatum)、盐角草群落(Comm. Salicornia europaea)和碱蓬群落(Comm. Suaeda glauca)的顺序演替, 而且物种种类趋向单一化, 群落结构趋向简单化。群落的物种多样性和群落间物种的替代速率都随土壤盐分的增加而减小, 而群落间物种的相似性则增加。区域性气候特点对盐生植物群落的特征也会产生一定的影响, 特别是在低盐渍化的条件下, 这种影响比较显著, 使得盐生植物群落体现出地带性的特点, 而随着土壤盐渍化程度的提高, 盐生植物群落的隐域性特征更为突出。因此, 这一地区的盐生植被又呈现出非常明显的地带性植被向非地带性植被过渡的特点。     

Simulation Study on the Alkalized-salinized Grassland Ecosystem in the Songnen Plain

Using Object-oriented design and a new programming language JAVA, a physically-based model was built to simulate the hydrological, alkalization/de-alkalization and salinization/desalinization processes in soil. Furthermore, a process-based model was built to evaluate the dynamics of four herbaceous ecosystems (including dynamics of above-ground biomass, below-ground biomass, and litter biomass), each dominated by Aneurolepidium chinense (Trin.) Kitag., Chloris virgata Sw., Puccinellia tenuiflora (Turcz.) Scribn. et Merr. and Suaeda glauca Bunge. This model is a daily-time step model, suitable for simulating hydrological, alkalization/de-alkalization and salinization/desalinization processes of heterogeneous soil, and growth dynamics of different grassland communities. With climatic data and experimental data of Changling Experimental Site in Jilin Province, the soil moisture content (in 1991, 1996, 1997 and 1998), soil salt concentration, exchangeable cation percentage and pH in soil and growth dynamics of these four sorts of grassland communities (in 1991) were simulated and the results were verified to be in accord with observed data.     

松嫩平原羊草草地植被退化与土壤盐渍化的关系

本文以羊草在群落中的重要值(Importance Value,Ⅳ)。相对盖度(C′)和相对地上生物量(W′)为植被退化程度指标,以土壤电导率(E1ectrical Conductivity,EC)和碱化度(Exchangeable Sodium percentage,ESP)为土壤盐渍度指标,探讨了它们之间的相互关系。结果表明,重要值(Ⅳ)与电导率(EC)及碱化度(ESP)的函数关系式分别为：Ⅳ＝60.1×0.69EC和Ⅳ＝64.03×0.97ESP。相对盖度(C′)与电导率(EC)及碱化度(ESP)的函数关系式分别为：C′＝96.2×0.56EC和C′=95.48×0.95ESP。随着土壤电导率(EC)和碱化度(ESP)的增大,羊草重要值(Ⅳ)和相对盖度(C′)呈指数曲线形式下降。并讨论了羊草生物量对土壤有机质(OM)和水解氮(N)含量的影响。羊草相对地上生物量(W′)与土壤有机质及水解氮含量均呈直线正相关。相关系数分别为： rOM=0.6486**(和rN=0.8809**。 均达极显著相关水准。随着土壤有机质含量的增加,羊草生物量(W′)呈直线上升。而土壤电导率(EC)和碱化度(ESP)则呈指数曲线形式迅速下降。它们之间的函数关系可用：EC=8.84×0.85OM和ESP=38.93×0.96OM来表示。研究结果证明,提高土壤肥力,恢复植被,改善植物生长状况,增加草地生物量积累和土壤有机质含量,是松嫩平原盐渍土改良治理的有效途径。     

北方泥质海岸防护林生态工程的研究

对泥质海岸防护林体系建设中造林树种选择、土壤改良和生态工程造林技术措施的分析表明,在轻度盐碱地可栽植绒毛白蜡、群众杨、刺槐、109柳;在中度盐碱地修台田并压沙后可栽植沙枣、群众杨、刺槐、绒毛白蜡及辽河杨耐盐品系;在苏打盐渍土地修台田压稻乱后栽植沙枣、辽河杨耐盐品系;在重盐土地上进行土壤改良及工程措施后栽植柽柳、沙枣.     

Effects of NaCl, Na2SO4, and mannitol on storage lipid mobilization in the cotyledons and roots of purple alfalfa seedlings

The effects of NaCl, Na₂SO₄, and mannitol on mobilization of storage lipids in the cotyledon mesophyll and root meristem cells during the germination of purple alfalfa (Medicago sativa L.) seeds were studied using the transmission electron microscopy technique. The ultrastructural analysis showed that the number and shape of specific organelles, oleosomes, depended on the osmotic effects of a salt used. In control seedlings grown on distilled water, lipid mobilization in roots terminated by the 4th day, and in cotyledons, only by the 8th day. The disruptions in the storage lipid mobilization in the treated seedlings were specific and depended on the stress agent used, the osmotic pressure induced by this agent, as well as on the tissue type. The presence of a great number of oleosomes in the cytoplasm of cells subjected to osmotic stress, in contrast to the control ones, demonstrated the inhibition of mobilization processes. All concentrations of Na₂SO₄ and mannitol suppressed lipid mobilization in the cotyledons and roots. At the same time, NaCl markedly suppressed this process in the root cells only at a higher osmotic pressure of the solution. The results obtained suggest that the cytological analysis of cotyledon storage-lipid mobilization can tentatively assess the resistance of dicotyledonous plants to abiotic stresses.     

Drought‐induced saltwater incursion leads to increased wetland nitrogen export

Coastal wetlands have the capacity to retain and denitrify large quantities of reactive nitrogen (N), making them important in attenuating increased anthropogenic N flux to coastal ecosystems. The ability of coastal wetlands to retain and transform N is being reduced by wetland losses resulting from land development. Nitrogen retention in coastal wetlands is further threatened by the increasing frequency and spatial extent of saltwater inundation in historically freshwater ecosystems, due to the combined effects of dredging, declining river discharge to coastal areas due to human water use, increased drought frequency, and accelerating sea‐level rise. Because saltwater incursion may affect N cycling through multiple mechanisms, the impacts of salinization on coastal freshwater wetland N retention and transformation are not well understood. Here, we show that repeated annual saltwater incursion during late summer droughts in the coastal plain of North Carolina changed N export from organic to inorganic forms and led to a doubling of annual NH₄⁺ export from a 440 hectare former agricultural field undergoing wetland restoration. Soil solution NH₄⁺ concentrations in two mature wetlands also increased with salinization, but the magnitude of increase was smaller than that in the former agricultural field. Long‐term saltwater exposure experiments with intact soil columns demonstrated that much of the increase in reactive N released could be explained by exchange of salt cations with sediment NH₄⁺. Using these findings together with the predicted flooding of 1661 km² of wetlands along the NC coast by 2100, we estimate that saltwater incursion into these coastal areas could release up to 18 077 Mg N, or approximately half the annual NH₄⁺ flux of the Mississippi River. Our results suggest that saltwater incursion into coastal freshwater wetlands globally could lead to increased N loading to sensitive coastal waters.     

盐生境下硅对坪用高羊茅生物学特性的影响

干旱半干旱区草坪绿地的长期灌溉容易引发土壤次生盐渍化,提高草坪草在盐生境下的生长发育能力是应对土壤次生盐渍化的主要途径之一.采用盆栽试验研究了盐生境下硅对坪用高羊茅(Festuca arundinaea)生物学特性的影响.结果表明,向盐生境土壤中添加不同浓度硅均提前高羊茅出苗时间2d,加快出苗速率,增加出苗总数,提高保苗率,且总出苗率和保苗率随着硅浓度增加而显著增大(P＜0.05),这说明盐生境下向土壤添加硅改善了幼苗完全死亡的现象.盐生境下硅显著增加了高羊茅叶长,株高和分蘖数,但对叶宽影响不显著,说明硅能够促进高羊茅生长,但对草坪绿地的质地影响不大.虽然硅能显著增加高羊茅总生物量(P＜0.05),但较低浓度时促进其茎叶生长,高浓度促进其根系生长.硅在高羊茅体内的沉积量随施入硅增加而增大,但其茎叶和根系内硅含量不超过3.0％,且根系内硅含量约为茎叶内硅含量的2倍.结果显示,硅提高了坪用高羊茅在盐生境下的适应能力,这为以后草坪绿地管理中应对土壤潜在盐渍化的问题提供了一定的科学依据.     

设施菜地土壤次生盐渍化分类与分级标准

近三十年来,我国设施蔬菜栽培发展迅速,已成为我国农业中最有活力的新兴产业之一.但在长期的设施蔬菜生产过程中,普遍存在着不合理施肥、养分比例失调、肥效下降和资源浪费严重等问题,致使土壤养分富集,盐分积累现象日趋严重.本文对我国设施菜地土壤次生盐渍化的现状、发生原因及其对作物的危害进行综述和分析,在此基础上制定设施菜地土壤次生盐渍化分类与分级的标准的建议及初步构架,旨在为防治设施菜地土壤次生盐渍化,实现设施菜地土壤的质量调控与可持续利用提供理论指导和科学依据.