Impact of inorganic nitrogen additions on microbes in biological soil crusts

Many studies have shown that changes in nitrogen (N) availability affect the diversity and composition of soil microbial community in a variety of terrestrial systems, but less is known about the responses of microbes specific to biological soil crusts (BSCs) to increasing N additions. After seven years of field experiment, the bacterial diversity in lichen-dominated crusts decreased linearly with increasing inorganic N additions (ambient N deposition; low N addition, 3.5 g N m⁻² y⁻¹; medium N addition, 7.0 g N m⁻² y⁻¹; high N addition, 14.0 g N m⁻² y⁻¹), whereas the fungal diversity exhibited a distinctive pattern, with the low N-added crust containing a higher diversity than the other crusts. Pyrosequencing data revealed that the bacterial community shifted to more Cyanobacteria with modest N additions (low N and medium N) and to more Actinobacteria and Proteobacteria and much less Cyanobacteria with excess N addition (high N). Our results suggest that soil pH, together with soil organic carbon (C), structures the bacterial communities with N additions. Among the fungal communities, the relative abundance of Ascomycota increased with modest N but decreased with excess N. However, increasing N additions favored Basidiomycota, which may be ascribed to increases in substrate availability with low lignin and high cellulose contents under elevated N conditions. Bacteria/fungi ratios were higher in the N-added samples than in the control, suggesting that the bacterial biomass tends to dominate over that of fungi in lichen-dominated crusts after N additions, which is especially evident in the excess N condition. Because bacteria and fungi are important components and important decomposers in BSCs, the alterations of the bacterial and fungal communities may have implications in the formation and persistence of BSCs and the cycling and storage of C in desert ecosystems.     

不同苜蓿根瘤菌固氮能力和黄酮变异研究

从重庆、安徽和新疆3个地区的宿主苜蓿上分别分离纯化出1个根瘤菌菌株。将3个菌株分别接种到WL323和阿尔冈金两个品种苜蓿上。分析不同处理的固氮能力和它们的芦丁的含量，以及黄酮含量和固氮的关系。结果表明：固氮能力、芦丁、黄酮含量都受到根瘤菌菌株、苜蓿品种和两者的相互作用影响；并且各组合的芦丁含量与固氮量之间成负相关，黄酮含量越高，固氮量越少。     

Fine root decomposition,nutrient mobilization and fungal communities in a pine forest ecosystem

Despite its importance to energy flow and nutrient cycling the process of fine root decomposition has received comparatively little detailed research. Disruption of the fine root-soil interface during preparation of root litterbags for decomposition studies could affect decay rates and nutrient mobilization in part by altering the community of decay organisms. We compared rates of decomposition and nutrient release from fine roots of pine between litterbags and intact cores and characterized the fungal community in the decomposing roots. Fine root decomposition was about twice as fast overall for intact cores than litterbags, and rapid mobilization of N and P was observed for roots in cores whereas nutrients were immobilized in litterbags. Fungal communities characterized using 454 pyrosequencing were considerably different between decaying roots in intact cores and litterbags. Most interesting, taxa from ectomycorrhizal fungal orders such as Boletales, Thelephorales and Cantharellales appeared to be more common in decaying roots from cores than litterbags. Moreover, the rate of N and P mobilization from decaying fine roots was highly correlated with taxa from two orders of ectomycorrhizal fungi (Thelephorales, Cantharellales). Although we caution that DNA identified from the decaying roots cannot be conclusively ascribed to active fungi, the results provide tentative support for a significant role of ectomycorrhizal fungi in decomposition and nutrient mobilization from fine roots of pine.     

微波消解-FAAS测定番木瓜不同部位的金属元素含量

为探讨番木瓜果肉、果皮、瓜籽中金属元素的含量,采用微波消解-FAAS法测定了番木瓜3个部位的K、Na、Ca、Mg、Cu、Fe、Zn共7种金属元素的含量,并对微波消解条件进行了优化。结果显示,在优化的微波消解条件下,样品消解完全、速度快、效果好,FAAS测定的各金属元素质量浓度与吸光度均呈良好的线性关系,相关系数r为0.995 7～0.999 9,检出限为0.002～0.131,回收率为98.30%～101.67%,RSD为0.20%～4.12%(n=6),说明测定方法可靠,结果稳定;番木瓜3个部位均含有较高的K、Ca、Mg,但Cu、Fe、Zn含量均较低,与番木瓜果肉相比,番木瓜果皮和瓜籽中K、Mg、Cu、Zn、Fe含量较高,食品和药品开发优势更突出。     

Leaf chlorophyll content as a possible diagnostic mean for the evaluation of plant nitrogen uptake from the soil

The influence of temperature, irradiance, and soil humidity on the nitrogen (N) concentration in some organs, chlorophyll in the leaves, N uptake and accumulation of dry matter in plants of winter wheat was investigated. In the plants grown under equal initial N supplement but in contrasting conditions of the evironment, the correlation between concentration of total N and chlorophyll in the leaves was absent. No interrelationship was found between concentration of total N in the leaves and accumulation of N and dry matter in the whole plants. There is a close correlation between chlorophyll in the leaves, accumulation of total N, and dry matter of the whole plant. It was concluded that chlorophyll is a more stable informative parameter for the estimation of the N uptake from the soil under different growth conditions than leaf N concentration.     

Significance of salt transport patterns in rice varieties differing in salt tolerance

Abstract

The absorption mechanisms for Na, K, SO₄ and Cl were tested in a salt tolerant (PVR 1) and a salt sensitive (GEB 24) rice varieties. The salt tolerant variety accumulated significantly larger amounts of Na than the salt sensitive variety. Further, PVR 1 absorbed SO₄ from Na₂SO₄ in preference to that from K₂SO₄. The absorption patterns for K and Cl were similar in both the varieties. It is concluded that the capacity of plant species to accumulate greater amounts of Na is a reflection of their halophytic feature.     

微生物菌剂对兰州城市生活污泥堆肥效果的影响

以兰州市城市生活鲜污泥和40%干污泥为原料，以玉米秸秆为辅料，添加金宝贝生物发酵剂和阿姆斯生物发酵剂进行堆肥，研究微生物菌剂对堆肥过程中温度、含水率、NH₄₊ N、NO₃^- N和全N的影响。结果表明，除鲜污泥（D 1，CK）处理外，其他各处理堆体温度保持在50 ℃以上均超过7 d，达到堆肥卫生标准，加入微生物菌剂使堆体提前5 d达到50 ℃；其他各处理经过20 d堆置含水率降至45%以下，达到园林绿化使用标准；加入微生物菌剂使堆体全N损失增加0.56%~4.47%，并促进NH₄₊ N的生成和NO₃^- N的积累。     

OK-50特效吸油材料的性能研究

通过试验，将公司自主研发的特效吸油材料OK-50应用于不同的油品吸附中，研究其适用油品种类、吸油量和保油率，得出该材料吸油倍率高，保油率也较高，使用范围较为广泛，应用前景广阔。     

Calcium nutrition of the sugarbeet

Abstract

When sugarbeet seedlings are transferred from a complete nutrient solution to one from which Ca has been withheld, the rootlets and tops fail to develop. The same transfer at the eight‐leaf stage causes the rootlets to become stubby and swollen at the tips and blade expansion becomes modified; particularly the upper portions of the blades attaining nearly full development, which pucker and often develop a cupping or hooding effect; a unique symptom characteristic of Ca deficiency. As each new leaf develops, the blade area becomes smaller until only a black tip remains at the apex of the petiole, which is the symptom referred to as tip‐burn for this petiole and the successively . shorter petioles formed as Ca deficiency increases in severity. Strangely, these symptoms also appear during periods of rapid growth when the nutrient solution contains as much as 10 to 28 milliequivalents per liter of Ca or when soils are high in Ca. This implies that Ca absorption and possibly translocation limits the Ca supply at the growing point. Increasing Mg in the nutrient solution decreases Ca uptake and increases Ca deficiency. Potassium deficiency, unexpectedly, induces Ca deficiency apparently by decreasing the translocation of Ca to the growing point.

These phenomena suggest the hypothesis that when ion absorption takes place from the root exchange site that has the affinity for H > Ca > Mg > K > Na, then the H generated internally replaces, and the roots absorb, Na, K and Mg preferentially. Externally, Ca would be adsorbed preferentially from the nutrient solution by the exchange complex, and with the addition of Mg, it would compete for the common adsorption site of Ca and limit Ca absorption internally. Under these conditions potassium‐deficient nutrient solutions would not induce Ca deficiency by decreasing Ca absorption but rather by decreasing Ca translocation. Theoretically, Ba would replace H more readily than Ca on the exchange complex, and therefore, Ba would be adsorbed preferentially and Ca uptake would increase. This effect of Ba was verified experimentally.

Since the translocation of ⁴⁵Ca to the growing point was found to be unrestricted under Ca‐sufficient and Ca‐deficient conditions and since the formation of insoluble Ca compounds such as phosphate or oxalate did not account for the Ca deficiency at the growing point, the cause of the Ca deficiency at the growing point is most likely the higher priority of the storage root for Ca over tops when leaf blades and storage root are both expanding rapidly. However, Ca retransport from older to younger parts of the sugarbeet plant may be restricted by the formation of Ca phosphate under Ca‐deficient conditions and Ca oxalate under Ca‐sufficient conditions.

Calcium deficiency increases net photosynthesis per unit blade area initially, probably because of blade puckering, but not on a per unit chlorophyll basis.