Secondary Succession and Natural Habitat Restoration in Abandoned Rice Fields of Central Korea

Floristic composition and soil characteristics (moisture, pH, nutrient contents) in abandoned upland rice paddies of different ages were analyzed to clarify the regenerative aspects of succession as a tool for habitat restoration. The study sites represented five seral stages: newly abandoned paddy fields; successional paddy fields abandoned for 3, 7, and 10 years; and a 50‐year‐old Alnus japonica forest. A vegetation sere was apparent in changes of dominant plant species in the order Alopecurus aequalis var. amurensis (annual grass), Aneilema keisak (annual forb), Juncus effusus var. decipiens (rush), Salix koriyanagi (willow), and Alnus japonica (alder) communities. These temporal stages resemble the spatial zonation of vegetation in local riparian floodplain ecosystems, indicating a hydrosere, with soil moisture decreasing over time. Age distributions and life forms of the dominant plant species support a “tolerance” model of secondary succession, in which the established species persist into later successional stages. Persistence of earlier colonizers led to a net cumulative increase in species richness and a more even distribution of species cover with increasing field age. Between 10 and 50 years, vegetation stabilizes as an alder community. Soil moisture content decreased steadily with paddy field age after an initial rise immediately after their abandonment, whereas pools of organic matter, N, P, K, Ca, and Mg, increased with field age. The pace and direction of recovery of native vegetation and natural soil properties in these abandoned rice paddies resembled classic old field succession, a form of secondary succession that often serves as a template for guiding restoration efforts. Active intervention, in particular dismantling artificial levees, could accelerate the recovery process, but natural habitat recovery generally appears sufficiently robust to achieve “passive” restoration of this rare community without intervention.     

不同养分和水分管理模式对水稻土质量的影响及其综合评价

田间小区试验下 ,通过对土壤理化和生物学特性指标的测定和分析 ,系统比较和研究了不同养分和水分管理模式对水稻土质量的影响及其综合评价。研究结果表明 :在干湿交替和控水模式下 ,有机无机肥配施可明显改善水稻土壤物理特性 ,提高土壤的有效养分含量 ,增加土壤酶的活性和土壤微生物生物量。在连续淹水下 ,土壤中加入有机物料 ,特别是厩肥 ,加剧了土壤的还原过程 ,削弱了有机肥料对水稻土理化特性和生物学特性的改善效果。模糊综合评判显示 ,有机无机肥配施的水稻土在干湿交替的水分模式下 ,其质量指标综合表现较好 ,特别是厩肥与化肥配施和干湿交替的水肥模式组合的隶属度为 0 .74 78,其土壤质量指标综合表现为最好。单施化肥和连续淹水的肥水模式组合的隶属度最低 ,为 0 .4 112     

DCD不同施用时间对水稻生长期CH4和N2O排放的影响

硝化抑制剂传统的施用方法是在作物移栽或播种前与基肥配合施用.通过温室盆栽试验研究相同施肥条件下,硝化抑制剂双氢胺(dicyandiamide, DCD)不同施用时间(与基肥混施、分孽肥后施入、穗肥后施入)对水稻生长期CH4和N2O排放的影响.结果表明,施入DCD能同时降低CH4和N2O排放量.就整个水稻生长期而言,与基肥混施DCD分别降低21.41%的CH4排放量和8.00%的N2O排放量;调节DCD施用时间至分孽肥后显著降低30.30%的N2O排放量,同时降低5.24%的CH4排放量.就施入DCD到水稻收获的特定生长阶段而言,缓施DCD分别降低32.65%的N2O排放量和11.18%的CH4排放量;晚施DCD对CH4和N2O排放的影响不大.CK、早施DCD、缓施DCD及晚施DCD处理CH4平均排放通量分别为0.95、0.75、0.87 mg/(m2 · h)及0.94 mg/(m2 · h),N2O平均排放通量为155.67、143.24、108.50 μg/(m2 · h)及153.24 μg/(m2 · h),缓施DCD显著降低CH4和N2O排放量(p＜0.01).土壤温度是影响N2O排放的主要因素,而CH4排放通量与土壤Eh呈显著负相关(p＜0.01).     

湿地农田土壤磷素的分布、形态与有效性及磷素循环

对江汉平原四湖地区湿地农田土壤磷素的含量分布、形态、有效性、磷素循环及施肥效应进行了研究.结果表明农田土壤全磷和有效磷含量随着地势的降低呈明显降低趋势,潜育性土壤全磷和有效磷含量均极显著低于非潜育性土壤.水田土壤Ca-P、Al-P、Fe-P和O-P分别占无机磷总量的58.1%、3.7%、10.6%和27.5%,其中Ca-P和Al-P与有效磷呈高度正相关(r分别为0.9286**和0.9038**),说明Ca P和Al-P是该地区水田土壤有效磷的主要来源之一.潜育性土壤Ca-P、Al-P和Fe-P的平均含量分别比非潜育性土壤低84.0、10.2和21.1mg/kg,其差异达显著或极显著水平,证明潜育性土壤磷素降低的主要原因是Ca-P、Al-P和Fe-P的损失.五种耕作制度下潜育性稻田土壤磷素输入输出平衡值为盈余2.3～27.9kg/hm2·a,其输入输出比(1/0)为1.06～1.88.对于土壤速效磷小于5mg/kg的潜育性稻田,早、中、晚稻的最高产量施磷量分别为4.83,4.93和1.78 P2O5kg/666.7m2.     

长期不同施肥模式对南方双季稻田生态系统净碳汇效应和经济收益的影响

施肥措施与稻田生态系统净碳汇效应、经济收益的关系密切。本研究以长期(35年)定位施肥试验田为平台,分析了单独施用化肥(MF)、秸秆还田+化肥(RF)、30%有机肥+70%化肥(OM)和无肥对照(CK)4种不同施肥模式对我国南方双季稻田耕层土壤固碳速率、碳密度、年碳汇平衡和经济收益的影响。研究表明: 不同施肥处理双季稻田耕层土壤碳库变化范围为216.02～866.74 kg·hm^-2·a^-1,OM处理土壤碳年变化量显著高于MF、RF和CK处理;双季稻田土壤固碳速率为51.5～650.7 kg·hm^-2·a^-1,表土碳密度为55.64～78.42 t·hm^-2,各施肥处理高低顺序均为OM>RF>MF>CK。各施肥处理双季稻田生态系统水稻的碳吸收为4.42～9.32 t C·hm^-2·a^-1,其高低顺序为OM>RF>MF>CK;与MF处理相比,OM和RF处理稻田土壤净碳汇量分别提高了27.6%和13.6%。各施肥处理双季稻田生态系统的碳成本物质投入变化范围为1.49～2.17 t C·hm^-2·a^-1,年经济收益变化范围为1.30×10³～7.83×10³元·hm^-2·a^-1,其高低顺序为RF>OM>MF>CK;OM、RF和MF处理双季稻田生态系统经济效益的净收益均显著高于CK处理。总之,长期施用有机肥、秸秆还田配施化肥措施均有利于增加双季稻田土壤固碳速率、碳汇效应和经济收益,是提高南方双季稻田土壤有机碳贮量的施肥模式。     

Effects of conservation tillage on soil organic matter in paddy rice cultivation

In this study, the effect of conservation tillage on soil organic matter (SOM) in paddy rice cultivation after 10 yr was investigated. Four treatments, disk till-fallow (DTF), disk till-wheat (DTW), conservation till-fallow (CTF) and conservation till-wheat (CTW) were used. The results indicated that the combinative application of no-tillage, ridge culture and wheat cultivation was a sound conservation practice in paddy rice cultivation. It not only significantly increased the concentration of SOM in the topsoil, but also affected optical and pyrolysis characteristics of humic acids (HA) through changing the composition and structure of SOM. At 0–10 cm, the greatest SOM content was in CTW, but declined sharply with depth, while in DTF, DTW and CTF the SOM content was not as high at the surface as in CTW, but did not decline as fast as in CTW. The oxidation stabilization of SOM was generally greater in no-tillage and ridge culture than that in disk till. The HA optical density in CTW at wavelength 665 nm and 465 nm was 0.122 and 0.705, while in DTF was 0.062 and 0.321, respectively. E₄/E₆ ratio in CTW was higher than that in the other treatments. The enthalpy capacity of the exothermal peak (360–365°C) for the HA DTA curve in no-tillage and ridge culture was lower than that in disk till, while the HA absorption peaks in 1000–1050 cm^?1 presented the reverse trend. The oxidation stabilization coefficient of HA in no-tillage and ridge culture was higher than that in disk till, indicating that the polycondensation degree and aromatization of HA were stronger. These findings suggest that it may be possible to manipulate paddy soil through conservational tillage and crop practices, and thereby maintain adequate SOM concentrations, and mitigate soil organic carbon loss from soil to atmosphere.     

环境因素对黑水滩河上游河段潜流层大型无脊椎动物群落的影响

在黑水滩河上游河段选取5个断面调查了潜流层大型无脊椎动物及其生境特征,研究微观尺度环境因素对潜流层大型无脊椎动物群落组成及分布的影响。结果表明:调查河段共发现大型无脊椎动物29种,其中水生昆虫种类最多;各断面大型无脊椎动物的密度、生物量和丰富度均随着潜流层深度的增加而降低;潜流层沉积物的中值粒径、垂向水力梯度和垂向渗透系数是影响大型无脊椎动物组成和分布的主要因素,其中最重要的是中值粒径。潜流层无脊椎动物群落变化也可能受到食物源和生物之间相互作用等因素的影响,所有这些因素共同形成了一个复杂的自然过滤系统,控制着潜流层无脊椎动物的群落结构和空间分布。     

Paddy straw as substrate for ethanol production

Pretreatment of paddy straw with 2% sodium hydroxide at 15 psi for 1 h resulted in 83% delignification. The hydrolysis of alkali treated paddy straw with a commercial preparation of cellulase for 2 h at 50°C resulted in release of 65% total reducing sugars. Maximum sugars were released at enzyme loading of 1.5% (v/v). The fermentation of hydrolysate supplemented with nutrients by S. cerevisiae resulted in the production of 20–30 g L⁻¹ ethanol after 48 h incubation which was further improved with addition of yeast nitrogen base and inoculated with 1% (w/v) yeast cells.     

绿肥配施氮肥对岩溶区稻田土壤微生物群落的影响

绿肥参与耕作改制是土壤培肥及作物增产的有效措施,对土壤微生物群落结构及多样性的影响至关重要。【目的】研究绿肥配施氮肥对岩溶区稻田土壤微生物群落结构的影响,阐明微生物、土壤生态环境因子及作物产量的相互关系,为岩溶稻区绿肥替代氮肥提供理论依据和数据支撑。【方法】以典型岩溶稻田土壤为研究对象,设置冬闲+不施氮肥(CK)、冬闲+氮肥(N)、绿肥+不施氮肥(M)、绿肥+氮肥(MN) 4个处理,通过3年田间定位试验,对土壤微生物进行高通量测序,解析不同施肥处理对细菌和真菌群落的影响。【结果】与CK相比,MN处理显著提高了早稻产量,提升了土壤有机质、全氮、碱解氮和速效钾含量,降低了速效磷含量。MN处理显著提高细菌群落丰富度及多样性,而真菌群落丰富度和多样性在MN处理有降低趋势。岩溶稻田土壤优势细菌类群主要为Chloroflexi、Proteobacteria和Acidobacteria等,优势真菌类群主要为Ascomycota、Basidiomycota和Zygomycota等。冗余分析(RDA)结果表明,土壤速效钾是影响土壤细菌群落组成的关键环境因子。共现网络分析结果表明,细菌-真菌群落交互关系主...