Water quality and coral bleaching thresholds: Formalising the linkage for the inshore reefs of the Great Barrier Reef, Australia

The threats of wide-scale coral bleaching and reef demise associated with anthropogenic climate change are widely known. Here, the additional role of poor water quality in lowering the thermal tolerance (i.e. bleaching ‘resistance’) of symbiotic reef corals is considered. In particular, a quantitative linkage is established between terrestrially-sourced dissolved inorganic nitrogen (DIN) loading and the upper thermal bleaching thresholds of inshore reefs on the Great Barrier Reef, Australia. Significantly, this biophysical linkage provides concrete evidence for the oft-expressed belief that improved coral reef management will increase the regional-scale survival prospects of corals reefs to global climate change. Indeed, for inshore reef areas with a high runoff exposure risk, it is shown that the potential benefit of this ‘local’ management imperative is equivalent to ∼2.0-2.5 °C in relation to the upper thermal bleaching limit; though in this case, a potentially cost-prohibitive reduction in end-of-river DIN of >50-80% would be required. An integrated socio-economic modelling framework is outlined that will assist future efforts to understand (optimise) the alternate tradeoffs that the water quality/coral bleaching linkage presents.     

Nitrogen stable isotope ratio in the manila clam, Ruditapes philippinarum, reflects eutrophication levels in tidal flats

Understanding the effects of anthropogenic eutrophication on coastal fisheries may help in the enhancement of fishery production by effective utilization of sewage effluents, as well as in the consequent reduction of eutrophication. In this study, it was revealed that the nitrogen stable isotope ratio (δ¹⁵N) in the soft tissues of the manila clam, Ruditapes philippinarum, can be used as an indicator of anthropogenic eutrophication levels in tidal flat environments by investigation of δ¹⁵N in dissolved inorganic nitrogen (DIN), particulate organic matter (POM), sedimentary organic matter (SOM) and soft tissues of the clam in five tidal flats in Japan with different levels of DIN concentration. In addition, it was found that the acid insoluble fraction of the shell organic matrix, conchiolin, can be used as a proxy for the soft tissues in δ¹⁵N analyses. This will contribute in easier storage handling and the expansion of chances for sample acquisition.     

施肥及刈割对干旱地区紫花苜蓿产量和品质的影响

在黄土高原中部干旱区采用随机区组试验,研究3个施氮水平(0、51.75、103.5 kg·hm^-2)和3个磷水平(0、126、252 kg·hm^-2)下不同刈割次数(3、4次)对“甘农3号”紫花苜蓿种植当年和第2年产量、株高、再生速度及品质的影响,并对紫花苜蓿生长两年中各指标进行比较.结果表明:干旱地区“甘农3号”紫花苜蓿在具备灌溉条件下,种植当年施肥可显著提高产量、株高和再生速度,且4次刈割下显著高于3次刈割;施肥也能增加紫花苜蓿粗蛋白含量,降低中性洗涤纤维和酸性洗涤纤维含量,4次刈割下品质更好;高氮低磷处理(N 103.5 kg·hm^-2+P₂O₅ 126 kg·hm^-2)下效果最好,单施氮肥较单施磷肥效果好.同时,第2年紫花苜蓿产量显著高于第1年,第1年增幅较第2年明显,说明在试验地区,“甘农3号”紫花苜蓿种植当年施肥更有效,第2年施肥仍有益;在灌溉和配施N103.5 kg·hm^-2+P₂O₅ 126 kg·hm^-2条件下,种植当年即可实现4次刈割.     

氮素及水分添加对科尔沁沙地4种优势植物地上生物量分配的影响

氮素和水分是半干旱沙地生态系统植物生长主要的影响因素,氮沉降和降水量与降水格局的变化可能会对植物生长产生深刻影响,进而影响沙地生态系统功能。本文通过科尔沁沙地草地连续2年增加水分（夏季增雨,冬季增雪）、添加氮素和同时添加氮素和水分的田间试验,分析了不同处理对4种优势草本植物种（尖头叶藜Chenopodium acuminatum 、白草Pennisetum centrasiaticum 、糙隐子草Cleistogenes squarrosa 和狗尾草Setaria viridi ）地上生物量积累和分配的影响。结果表明：单纯添加氮素或水分对当地4种优势植物平均地上总生物量、各构件平均生物量及繁殖体和茎平均生物量分配无显著影响。夏季增雨×氮素添加使4种植物平均地上总生物量及各构件平均生物量在2010年显著增加,冬季增雪×氮素添加使叶生物量分配在2010年显著增加;但是在2012年各处理对生物量的分配影响不显著。这说明夏季增雨×氮素添加能够解除氮素对水分的限制作用,使植物将所获得的有限资源供于叶片生物量的积累和分配。但是添加氮素与水分影响的生物量分配变化程度因物种而异,对尖头叶藜、白草、糙隐子草的影响不明显,对狗尾草的影响显著。     

亚热带人工针叶林冠层叶氮浓度的星载高光谱遥感能力评估(英文)

冠层叶片氮浓度(CNC)是影响森林生态系统生产力的重要参数之一。本研究探讨了星载成像光谱遥感在估测亚热带红壤丘陵区人工针叶林CNC的表现。分析包括了星载成像光谱数据(Hyperion影像)覆盖的两条样带上的57个野外样方,并将其分为三个子集(A-C)。利用一元回归和偏最小二乘回归方法分析了CNC与成像光谱信息之间的关系。在A-C子集中,CNC与近红外反射率(NIR)之间的相关性一致都呈现显著的正相关关系(R2=0.29,0.33和0.36,P0.05或P0.01)。另外,我们利用归一化的氮指数(NDNI)估计森林CNC的变异。在3个子集中,NDNI与CNC都呈现极显著的正相关关系,但相关性不高(R2=0.38,0.20和0.17,P0.01)。然后利用偏最小二乘方法分析了CNC与整个成像光谱数据(反射率、对数变换和一阶导数变换)之间的相关性,对于各个子集相关性不同且相对微弱。在分析已有数据和对比前人文献基础上,文章分析了影响成像光谱遥感森林CNC的可能原因,并指出研究区人工针叶林单一的冠层结构可能减弱了该地区森林CNC与成像光谱信息之间的相关关系。     

从中沟与王圪垱遗址看公元前三千纪前后洛阳盆地的生业经济

作为早期王权国家诞生的核心区域,洛阳盆地新石器时代晚期至青铜时代早期发生了剧烈的社会变革,对这一过程中该地区生业经济状况的研究主要集中于动植物考古方面,尚需其他证据予以全面评估。为此,本文对仰韶晚期的中沟遗址和龙山晚期至二里头早期的王圪垱遗址出土人骨开展了碳氮稳定同位素分析。研究发现,中沟(δ^13C=-7.5±1.4 ‰,δ^15N=8.5±0.8 ‰,n=28)与王圪垱遗址人群(δ^13C=-9.9±1.9 ‰,δ^15N=8.8±1.1 ‰,n=14)的δ^13C值略有差异,而δ^15N却比较接近。结合植物考古等相关研究结果,我们认为两遗址先民虽然均主要以粟、黍等C4类食物为食,但王圪垱先民食物中水稻的比例有所增加。这种状况可能与龙山晚期之后本地与南方稻作农业人群文化交流更加密切有关。本研究的另一发现是,中沟与王圪垱遗址中墓葬人群(δ^15N=8.9±0.6 ‰,n=17;δ^15N=9.2±1.0 ‰,n=9)的δ^15N值明显高于灰坑人群(δ^15N=7.8±0.7 ‰,n=11;δ^15N=7.9±0.7 ‰,n=5),即前者饮食中肉类比例高于后者。考虑到仰韶中期以来中原地区社会分层越演愈烈,肉食消费的多少一定程度上是人群分化的体现。     

贵阳次生林不同演替阶段土壤微生物生物量与反硝化酶活性的研究

土壤营养元素赋存状态和微生物活性是喀斯特地区生态恢复的关键质量指标,温室气体N2O的排放是全球变暖的重要因子。研究了雨季贵阳不同演替阶段森林表层土壤（0～10cm）微生物生物量（SMB）、反硝化酶活性（DEA）、无机氮（N）库和N转化特征,并与玉米地、茂兰喀斯特原始森林土壤做了对比分析。结果表明,微生物群落对土壤水分条件响应强烈,土壤有效N的增加有助于微生物群落的增长,土壤N转化速率越快,微生物N同化作用越低。人为干扰（火烧和农业活动）会增加或降低土壤SMB、增加潜在的气态N流失。总的来说,不同演替阶段土壤SMB、DEA和土壤N库均有显著差异,随植被恢复土壤SMB呈上升趋势,温室气体N2O的排放量呈下降趋势,气态N流失形态从N2O转变为N2,N循环过程趋于优化,表明自发演替是退化喀斯特森林恢复的可靠方式。     

Analysis of the influence of free ammonia on the accumulation of nitrite in the nitrite nitrification system

Low- and high-concentration nitric wastewater can induce stable nitrite accumulation and realize the nitrification system, with the nitrite accumulation rate between 50% and 90%. In the low-concentration nitrite nitrification system, the average FA concentrations during the period of stable nitrite accumulation remained at 7 to 10 mg/L. In the high-concentration nitrite nitrification system, the nitrogen oxidation activity will not be affected by biomass, the nitrite oxidation activity is related to the system biomass, it is recommended to be measured by FA/MLSS. Keeping the FA sludge load below 0.1 is the precondition of making good nitrite accumulation and nitrogen degradation rate. Nitrite oxidation bacteria cannot be totally eliminated or washed out from the system.     

The distribution characteristics of nitrogen and phosphorus in the ecological system of Mt. Beigu wetland

The Mt. Beigu wetland, which has undergone periodical changes in water level, lies by the Yangtze River, and its dominant plants are Phragmites communis, Phalaris arundinacea and Polygonum lapathifolium. In order to study the distribution characteristics of nitrogen and phosphorus in the ecological system of the Mt. Beigu wetland, the authors measured the contents of total nitrogen and total phosphorus in Phragmites communis, Phalaris arundinacea and Polygonum lapathifolium, and the contents of nitrogen and phosphorus in the wetland soils with different plant species. In addition the authors investigated the influence of various plants on the spatial and seasonal (spring/autumn) distributions of nitrogen and phosphorus in the wetland soil. The contents of nitrogen and phosphoms in Phalaris arundinacea are significantly higher than those of the other two plant species in the same part. Secondary pollution of phosphorus in the wetland results mainly from Phalaris arundinacea. Phragmites com-munis effectively carries away nitrogen and phosphorus in the wetland soil in the wet season. The capacity of Poly-gonum lapathifolium to remove nitrogen is lowest among the 3 species of plants. These findings offer a theoretical foundation for the selection of plant species to restore the ecological environment and for the selection of time and depth for purging silt on the riverside wetland.     

Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation

Semi-sealed preservation of soil samples at different moisture of 4% and 23%, respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively. The results show that during preservation, the quantity of microbial communities tended to increase first and then decrease, with a wider variation range at higher moisture (23%). At the moisture content of 23%, the microbial communities became more active on the 7th day, but less after 30 days, and their activity was stable with little fluctuation at the moisture content of 4%. However, there were no significant changes in the contents and isotopic compositions of the total organic carbon and total nitrogen. During preservation, the responses of soil microbes to the environment are more sensitive to changes in the total nitrogen and organic carbon contents. It is thus suggested that the variations of microbial communities have not exerted remarkable impacts on the isotope compositions of the total nitrogen and total organic carbon.