我国平原农区复合农林业小气候效应研究概述

通过对近50年来我国平原农区复合农林业小气候效应总结，指出农田防护林及农林间作等复合农林业模式具有降低风速、调节气温和改善农田水分状况等小气候效应，为农业生产提供了重要的生态保障。     

Moisture modulates rhizosphere effects on C decomposition in two different soil types

While it is well known that soil moisture directly affects microbial activity and soil organic matter (SOM) decomposition, it is unclear if the presence of plants alters these effects through rhizosphere processes. We studied soil moisture effects on SOM decomposition with and without sunflower and soybean. Plants were grown in two different soil types with soil moisture contents of 45% and 85% of field capacity in a greenhouse experiment. We continuously labeled plants with depleted ¹³C, which allowed us to separate plant-derived CO₂-C from original soil-derived CO₂-C in soil respiration measurements. We observed an overall increase in soil-derived CO₂-C efflux in the presence of plants (priming effect) in both soils. On average a greater priming effect was found in the high soil moisture treatment (up to 76% increase in soil-derived CO₂-C compared to control) than in the low soil moisture treatment (up to 52% increase). Greater plant-derived CO₂-C and plant biomass in the high soil moisture treatment contributed to greater priming effects, but priming effects remained significantly higher in the high moisture treatment than in the low moisture treatment after correcting for the effects of plant-derived CO₂-C and plant biomass. The response to soil moisture particularly occurred in the sandy loam soil by the end of the experiment. Possibly, production of root exudates increased with increased soil moisture content. Root exudation of labile C may also have become more effective in stimulating microbial decomposition in the higher soil moisture treatment and sandy loam soil. Our results indicate that moisture conditions significantly modulate rhizosphere effects on SOM decomposition.     

Plant species richness in the Chaco Serrano Woodland from central Argentina: Ecological traits and habitat fragmentation effects

The Chaco Serrano Woodland from central Argentina has been dramatically reduced during the past 30 years, and is currently confined to several isolates of different size. In this study, we evaluated the effects of forest size, isolation and edge formation on plant species richness. Furthermore, we tested whether plants species with particular ecological traits were differentially affected by habitat fragmentation. Habitat area showed the highest explanatory value for plant species richness in stepwise multiple regressions. The effect of area was most pronounced for rare species, suggesting that large forests are necessary to preserve species with low local or regional abundance. Differences between edge and interior of Chaco Serrano were more pronounced for native and shrub species richness. The analysis of individual species cover revealed that native and biotically pollinated plants were less abundant in woodland edges. Our results showed that forest transformation into smaller remnants has lead to an impoverishment of plant communities, with particular subsets of species defined by ecological traits (rarity, origin and pollination mode) being more susceptible.     

Influence of dieldrin on the reproduction of the earthwormEisenia fetida (Oligochaeta)

Summary The environmental hazard of the agricultural pesticide dieldrin for the earthwormEisenia fetida was experimentally determined in order to assess and quantify sublethal effects. We determined that the non-toxic dieldrin had a negative effect on cocoon production. An inverse relationship was found between the concentration of dieldrin in the environment and the number of hatchlings per cocoon. The hatchlings were also smaller than those from the controls.Hatching success of cocoons was also adversely affected and the incubation period was longer. Knowledge of sublethal effects has predictive value in ecotoxicological work and could serve as a timely warning device of an overburdened soil ecosystem.     

坡地植物篱农业技术生态经济效益评价

坡地植物篱农业技术是一条有效防治水土流失、提高土地生产潜力的坡地改良利用途径,是山丘区环境、资源与经济协调发展的努力方向。2年试验结果表明,植物篱农业技术可减小坡地坡度3°,增加土壤有机质10.39%,减少土壤侵蚀量96.74%,减少地表径流量75.82%,农业生产投入产出比为1.58,是山丘区值得大力推广应用的农业技术体系。     

“泡沫砂”改良黏重黄壤孔隙结构的粒径效应

以贵州毕节黏重的黄壤为研究对象,通过掺入等量不同粒径的泡沫砂进行温室模拟试验,泡沫砂粒径分别为0.5?2 mm(1T)、2?7 mm(2T)和7?10 mm(3T),研究孔隙特征改良的粒径效应。研究表明:与CK相比,添加3种粒径泡沫砂的处理均增加了土壤的通气孔隙,但在同等添加比例下,随着泡沫砂粒径的增大,土壤通气孔隙度也随之增加,1T、2T和3T处理相较于CK处理分别增加了4.68%、7.39%和14.5%;不同粒径泡沫砂对不同当量孔径的孔隙影响不同,1T、2T和3T处理分别显著提升了当量孔径200?500、1 000?2 000、2 000μm的孔隙;不同处理均很好地提升了土壤孔隙连通度,但不同处理之间无显著差异。2T处理在改良土壤总孔隙和容重方面,与3T处理一同并为较优处理;在改良土壤通气孔隙度方面,2T处理的土壤通气孔隙度达到农业生产上最适宜区间,为最优处理;在改良分级孔隙配比方面,2T处理为次优处理。因此,从土壤通气孔隙、土壤分级孔隙和土壤孔隙形态等多角度考虑,2?7 mm粒径泡沫砂可作为黏重土壤改良的最佳材料。     

考虑尺度效应的土壤溶质运移动力学特征分析

[目的]为了了解土壤环境中弥散尺度效应、动力学吸附等作用对溶质运移过程的影响。[方法]应用Laplace变换方法和复变函数理论推得溶质运移动力学模型的解析解。利用De Hoog数值反演方法,验证解析解的正确性,利用解析解分析溶质在土壤中的运移特征。[结果]解析解的计算结果与反演函数Fourier级数项数2 N较大(N=500)时的De Hoog数值计算结果吻合很好;土壤溶质浓度随尺度效应的增强、吸附作用及生物降解作用的减弱而增大;分子扩散、一阶动力学吸附以及吸附相溶质降解作用对溶质运移变化影响较小。[结论]所推求解析解是正确的;土壤溶质运移的弥散尺度效应,溶质在液相和吸附相间的线性分配作用及溶质在液相中的降解作用是影响土壤溶质运移过程的主要因素。     

喀斯特峡谷地区不同等级石漠化治理的生态效应——以贵州省花江石漠化生态综合治理示范区为例

 选取贵州省花江石漠化生态综合治理示范区为研究区,对比分析石漠化生态治理前后不同等级石漠化的土壤理化性质、小气候特征、植被数量特征和地表水土流失状况等指标。结果表明:石漠化是可以治理的,强度石漠化治理效应优于中度石漠化,轻度石漠化次之,潜在石漠化生态效应速度最慢;治理措施有效地改善了土壤理化性质、增强了土壤肥力,提高了地表生物量和植被覆盖度,生物多样性得到了有效恢复和保护,改善了区域局部小气候。     

Web spider community response along an edge between pasture and Araucaria forest

We investigated how vegetation features and temporal variation influenced web spider richness, abundance and composition along an edge between Araucaria forest and pasture in southern Brazil. Web spiders and vegetation were surveyed four times over a 1-year period, in five 5 × 5 m plots randomised in four locations: 50 m into the pasture, 0, 50 and 250 m into the forest. We collected a total of 836 web spiders (33 morphospecies and six families). We found different web spider assemblages occurring at the pasture edge and forest interior. The richness and abundance of web spiders decreased up to 50 m towards the forest interior in all seasons, and we found a positive influence of vegetation richness on web spider abundance. In conclusion, web spider assemblages are influenced by an edge gradient, this pattern is consistent throughout the year and is strongly related to vegetation features.