外源Cd胁迫对红壤性水稻土微生物量碳氮及酶活性的影响

研究外源Cd对红壤性水稻土微生物学指标的影响。采集湖南长沙红壤性水稻土,设置外源Cd胁迫浓度梯度为0、1、3、5、7 mg·kg~(-1)和10 mg·kg~(-1),进行室内模拟土壤Cd污染培养实验,测定土壤微生物生物量碳、氮和土壤酶活性指标。结果表明:土壤微生物生物量碳、氮含量随外源Cd胁迫浓度的增加表现为先上升后降低的趋势,当外源Cd胁迫浓度为1 mg·kg~(-1)时,土壤微生物生物碳、氮含量达到最大值;土壤脱氢酶、过氧化氢酶和脲酶的活性随着外源Cd胁迫浓度的增加而显著降低;而土壤蔗糖酶活性随外源Cd胁迫浓度的增加表现为先下降后上升再下降的趋势。由通径分析可知:外源Cd胁迫可以直接影响土壤微生物生物量,也可以通过酶活性间接影响土壤微生物生物量,Cd污染对酶活性的影响也有同样的作用机制;其中Cd胁迫对微生物生物量碳的直接抑制作用系数最大(-1.110),与脱氢酶的相关系数最大(-0.952~(**))。综上,外源Cd胁迫对土壤微生物生物量和酶活性均有不同程度的抑制作用,其中对脱氢酶活性抑制作用最为明显。     

烟杆生物炭对砒砂岩与沙复配土壤理化性状及玉米生长的影响

为明确施用生物炭对砒砂岩与沙复配土壤水分保持及肥力提升的影响,采用盆栽试验,研究了不同生物炭施用量(0,10,20,30,50g/kg(以风干土计))对砒砂岩与沙复配土壤理化性状及玉米生长的影响。结果表明:在种植玉米一季后,施用生物炭可显著降低复配土壤容重,尤其当生物炭施用量达到30g/kg时,土壤容重可降低至1.37g/cm3,但当生物炭施用量增加到50g/kg时,土壤容重又出现增加的趋势;土壤田间持水量随生物炭施用量的增加呈显著增加趋势,但当施用量增加到50g/kg时又会出现下降趋势;土壤pH、全盐量随生物炭添加量的增加显著增加,尤其当生物炭添加量为50g/kg时,土壤pH可达8.80,全盐量可达2.51g/kg;土壤有机质、有效磷、速效钾含量也随生物炭施用量的增加而显著增加,但有效磷在生物炭施用量增加至50g/kg时出现下降趋势。进一步分析不同生物炭处理对玉米生物量的影响,发现玉米根干重、地上部分干重、百粒重、单株产量均随生物炭施用量的增加呈显著增加趋势,但当生物炭施用量增加到50g/kg时,上述各指标反而显著降低。生物炭对于砒砂岩与沙复配土壤理化性状、水分保持、肥力提升、作物生长及产量等诸多方面都有明显改善效果,在施用过程中需要注意使用量,在本试验条件下,生物炭推荐施用量为30g/kg干土。     

生物质炭添加对重金属污染稻田土壤理化性状及微生物量的影响

分析了生物质炭添加对红壤性水稻土理化性状、重金属含量及微生物生物量的影响。通过田间小区长期定位试验,一次性施入不同量生物质炭(0,10,20,30,40t/hm2),于2017年9月采集各处理表层土样(0—15cm),研究土壤理化性状、重金属含量及微生物生物量的变化。结果表明:生物质炭添加对土壤理化性状、重金属含量及微生物生物量均有显著影响。与对照相比,供试土壤的pH、EC和有机质含量随生物质炭添加量的增加而增大,增幅分别为5.11%~18.43%,37.62%~104.31%和1.72%~22.41%,而有效磷和铵态氮含量随生物质炭添加量的增加呈先增大后减小趋势,分别在生物质炭添加量为10t/hm2和30t/hm2时达到最大值。随生物质炭添加量的增加,土壤有效态Cd和有效态Pb含量均呈降低趋势,而土壤有效态As含量呈先增加后减少的趋势,三者均在生物质炭添加量为40t/hm2时达到最小值。土壤微生物生物量碳、氮和微生物商随生物质炭添加量的增加均呈先升高后降低的趋势,均在生物质炭添加量为20t/hm2时达到最大值。相关分析表明,生物质炭添加量分别与土壤有效态Cd和Pb含量之间呈极显著负相关(P0.01);通径分析表明,生物质炭主要是通过直接作用影响土壤有效态Cd含量,而土壤pH、EC、有机质、微生物生物量碳、氮和有效磷主要是通过间接作用影响土壤有效态Cd含量。因此,添加适量生物质炭不仅可以改善土壤重金属污染现状和土壤理化性状,提高土壤养分含量,还可以改良土壤生物学性质,增加土壤微生物量。研究结果可为提高稻田土壤肥力和改善土壤重金属污染状况提供科学依据。     

Long-term grazing exclusion influences arbuscular mycorrhizal fungi and their association with vegetation in typical steppe of Inner Mongolia,China

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal(AM) fungi and their association with steppe vegetation. In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983(E83) and 1996(E96), and one site of free-grazing(FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus(P) uptake as well. The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site. In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG. Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant. These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production. Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.     

Impacts of silicon on biogeochemical cycles of carbon and nutrients in croplands

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon (Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis indicates that the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable development of agriculture.     

生物质基SiC陶瓷材料制备及应用研究进展

生物质基SiC陶瓷是一种环境友好的新型材料,具有硬度高、抗氧化、耐腐蚀、力学性能优异等特点,因而受到越来越广泛的关注。文中主要阐述了国内外学者对生物质基SiC陶瓷材料制备方法及应用的研究进展,包括以木材、竹材、稻壳、纸张、废弃棉绒等生物质材料为碳模板,运用液态渗硅法、溶胶凝胶-碳热还原法、气相渗透法3种方法制备生物质基SiC陶瓷方面的研究现状,以及对其作为电磁屏蔽材料、防弹材料、电容器、电极材料、催化剂材料等方面的应用进行了探讨,并分析了当前SiC陶瓷研究存在的问题及未来发展趋势。     

不同荒漠生态系统下有机碳和微生物碳的分布特征

基于新疆古尔班通古特沙漠南缘原始盐生旱生荒漠的3种建群灌木琵琶柴(Reaumuria soongori-ca)、多枝柽柳(Tamarix ramosissima)和梭梭(Haloxylon ammodendron)生态系统下土壤剖面实测数据,分析了土壤有机碳(SOC)和土壤微生物量碳(Mc)的垂直分布特征及其与土壤理化因子的关系。结果表明:3个生态系统类型之间土壤剖面SOC分布状况和含量不存在显著差别,但每个生态系统土壤剖面土层之间存在显著差别。各生态系统土壤上层均存在着一定厚度的SOC富集层,中部(10～30cm)SOC含量迅速下降,下部有机碳含量低而稳定。Mc分布与含量与SOC存在相似的规律。Mc对90cm以上的土壤碳循环起着重要的作用,而对深层次的碳库影响不大,不会对全球变化做出响应,但意义更重要,它们可以更长期保留于土壤中而不释放回大气圈。     

不同生态恢复措施对紫色土活性有机碳的影响

研究不同生态恢复措施—“参考林分”(C0)、“林果草+水平沟”(C1)、“乔灌草+竹节沟”(C2)、“油茶+等高草带”(C3)和“未治理地”(CK)对土壤总有机碳和活性有机碳的影响。结果表明：生态恢复后,其中C1 和C2 措施总有机碳含量分别比未治理地CK增加了51.87%和52.90% (P<0.05),达到C0 措施的48.42%和48.75%。然而,C3 措施未显著影响总有机碳含量,仅为C0 措施的29.32%。C1 和C2 措施的微生物量碳、冷水和热水浸提的可溶性有机碳含量均显著提高,分别比CK措施增加了49.91%~78.77%、43.15%~91.11%和28.17%~108.36%,达到C0 措施的67.01%~89.47%、35.65%~57.95%和32.88%~39.21%,而C3 措施的微生物量碳和冷水浸提的可溶性有机碳略为减少,而热水浸提的可溶性有机碳增加了29.87%。土壤总有机碳与各活性碳之间以及各活性碳之间相关性均达到极显著水平。微生物量碳、冷水和热水浸提的可溶性有机碳占总有机碳的比例分别介于1.91%~4.73%、0.76%~2.49%和4.11%~8.16%之间。     

3种植物对镉污染土壤修复的试验研究

为探究植物修复技术在济源镉(Cd)污染土壤的应用特征和效果,笔者以不同Cd污染程度的实际土壤为对象,采用盆栽试验,对比三叶鬼针草、黑麦和印度芥菜对Cd的耐受、富集、转移能力及修复效率。结果表明：污染组植物的生物量无显著下降,供试植物均具有较强的Cd耐性。3类植物富集特征不同,地上部分富集Cd浓度顺序依次是：三叶鬼针草＞印度芥菜＞黑麦。3种植物中黑麦地下部分Cd含量最高,轻、重度污染组的Cd含量分别达到11.95 mg/L、28.56 mg/L。三叶鬼针草对Cd具有较强的转移能力,其中在轻度污染土壤中转移系数(TF=2.23)最大。此外,三叶鬼针草修复效率最高,轻、重度污染组分别为2.04%、1.59%。综上所述,三叶鬼针草的生物量、富集转运系数和修复效率均高于黑麦和印度芥菜。因此,三叶鬼针草可作为济源Cd污染土壤修复植物之一,为当地土壤Cd污染治理提供理论指导和技术依据。     

Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient

Production of biomass is central to the ecology and sustainability of fish assemblages. The goal of this study was to empirically estimate and compare fish assemblage production, production‐to‐biomass (P/B) ratios and species composition for 25 second‐ to third‐order streams spanning the Appalachian Mountains (from Vermont to North Carolina) that vary in their temperature regimes. Fish assemblage production estimates ranged from 0.15 to 6.79 g m^?2 year^?1, and P/B ratios ranged from 0.20 to 1.07. There were no significant differences in mean assemblage production across northern cold‐water, southern cold‐water and southern cool‐water streams (p = .35). Two warm‐water streams, not included in these comparisons, had the highest mean production and biomass values. Mean assemblage P/B was significantly higher in northern cold‐water streams relative to southern cold‐water and cool‐water streams (p = .01). Species evenness in production declined with stream temperature and differed significantly across the lower latitude cold‐water, cool‐water and warm‐water streams and the higher latitude (i.e. more northern) cold‐water streams. Our fish assemblage production estimates and P/B ratios were both lower and higher compared to previously published estimates for similar stream habitats. This study provides empirical fish assemblage production estimates to inform future research on southern Appalachian streams and on the potential impacts of varying temperature regimes on cold‐water, cool‐water and warm‐water fish production in the coming decades as climate change continues to threaten fish assemblages.