云南德宏州油茶土壤和叶片养分含量及生态化学计量特征

目的 云南德宏州是我国唯一处在热带北缘的油茶种植区,研究该区域油茶土壤和叶片养分含量及生态化学计量特征,为油茶科学施肥、精准管理提供理论依据。方法 采用生态化学计量学的研究方法,测定并分析油茶土壤和叶片碳、氮、磷、钾含量与化学计量特征。结果 油茶林地土壤有机碳、全氮、全磷和全钾质量分数分别为47.77、2.56、0.69 和5.28 g·kg^-1,土壤有效磷和速效钾质量分数分别为3.69 和26.05 mg·kg^-1,土壤有机碳、全氮、全磷的变化具有协同性,土壤速效钾、有效磷含量直接取决于土壤全钾、全磷含量。油茶叶片碳、氮、磷和钾质量分数分别为422.09、13.51、0.97 和4.92 g·kg^-1;氮、磷协同变化,且均受到土壤磷调控,油茶生长发育受到氮、磷双重限制,其中磷为主要限制元素。叶片磷和磷钾比具有内稳态特征,内稳态指数H_P为5.08,H_P:K为3.26,其余元素及化学计量比均不具备内稳态特征。结论 云南德宏州油茶需持续加强磷元素投入,同时均衡投入氮、钾元素,以保障油茶的健康与持续产出。     

荒漠草原不同放牧强度下土壤酶化学计量特征的研究

为探讨不同放牧强度对土壤酶活性及其化学计量比的影响,本研究依托于内蒙古农牧科学研究院长期放牧平台(2004年开始放牧),每个区组内设置4个不同放牧强度：重度(Heavy grazing, HG)、中度(Moderate grazing, MG)、轻度放牧区(Light grazing, LG)和对照区(Contral, CK),各小区放牧羊的数量分别为12,8,4,0只,于2021年5月利用土钻法进行野外取样,室内分析土壤理化性质、土壤微生物生物量、土壤酶活性及其化学计量特征。结果表明：随放牧强度增加,土壤理化性质,养分含量及其化学计量特征发生显著变化(P<0.05)。土壤微生物养分含量及与C(αG、βG)、N(NAG、LAP)、P(ALP)相关的5种酶活性均随放牧强度增加而降低。随放牧轻度增加,向量长度(Vectoe Lengh)和向量夹角(Vectoe Angle)均显著增加,与C、N、P循环相关的5种土壤酶活性及其化学计量比显著降低(P<0.05)。荒漠草原受C、N限制,且放牧强度越大限制越严重。     

论图书馆立法及制约法实现的因素

一部科学性、民主性和可行性较强的图书馆法的制定需要坚持基本的指导思想和原则,然而法自身具有的局限性及社会成员综合素质、政治体制、经济实力等因素,却客观地制约着图书馆法的实现。     

Growth and Photosynthesis Responses of a Super Dwarf Rice Genotype to Shade and Nitrogen Supply

Specific aspects of plant cultivation require tests under fully controlled environmentalconditions with restricted energy supply, such as orbit-based space laboratories and low-light conditions.For these growing conditions, super dwarf plants have been developed as model crops, and a gibberellindeficientSuper Dwarf Rice genotype was proposed as a model crop for space flight plant experiments.We tested this genotype in a climate chamber experiment under different illumination and nitrogen supplylevels to assess its suitability under scenarios with limited resource availability. A 25% reduction inillumination led to a 75% reduction in yield, mainly due to a 60% reduction in formed tillers and 20%reduction in grain weight, and a 80% reduction in illumination caused total yield loss. Leaf area underreduced illumination was significantly lower, and only marginal changes in the dimensions of leaves wereobserved. Plant photosynthesis was not significantly different between control and 75% illumination. Thiswas explained by a higher photochemical efficiency under lower light conditions and a reduced mesophyllresistance. Therefore, we concluded that this genotype is well-suited for plant experiments under spaceand light-limited conditions since it kept its small stature and showed no shade avoidance mechanisms,such as leaf elongation, which would complicate experiments under low-light conditions. Nitrogenconcentrations of 2.8 and 1.4 mmol/L led to no differences in plant growth. We concluded that a nitrogenconcentration of 1.4 mmol/L is sufficient for this genotype under the light intensities.     

低温锻炼对黄瓜幼苗光合作用的影响

低温处理中能降低黄瓜幼苗的净光合速率,同等条件下低温锻炼的黄瓜幼苗,比未锻炼幼苗降低较少,低温锻炼后和低温处理使幼苗气导度和叶肉细胞间ＣＯ２浓度的降低,气孔限制值上升,未经低国锻炼的黄瓜幼苗在净光合速率降低的同时,叶肉细胞间ＣＯ２浓度增加,气孔限制值下降,光合作用的降低主要以非气孔限制为主。     

Soil carbon and nitrogen mineralization: Theory and models across scales

In the last 80 years, a number of mathematical models of different level of complexity have been developed to describe biogeochemical processes in soils, spanning spatial scales from few μm to thousands of km and temporal scales from hours to centuries. Most of these models are based on kinetic and stoichiometric laws that constrain elemental cycling within the soil and the nutrient and carbon exchange with vegetation and the atmosphere. While biogeochemical model performance has been previously assessed in other reviews, less attention has been devoted to the mathematical features of the models, and how these are related to spatial and temporal scales. In this review, we consider ∼250 biogeochemical models, highlighting similarities in their theoretical frameworks and illustrating how their mathematical structure and formulation are related to the spatial and temporal scales of the model applications. Our analysis shows that similar kinetic and stoichiometric laws, formulated to mechanistically represent the complex underlying biochemical constraints, are common to most models, providing a basis for their classification. Moreover, a historic analysis reveals that the complexity and degree and number of nonlinearities generally increased with date, while they decreased with increasing spatial and temporal scale of interest. We also found that mathematical formulations specifically developed for certain scales (e.g., first order decay rates assumed in yearly time scale decomposition models) often tend to be used also at other spatial and temporal scales different from the original ones, possibly resulting in inconsistencies between theoretical formulations and model application. It is thus critical that future modeling efforts carefully account for the scale-dependence of their mathematical formulations, especially when applied to a wide range of scales.     

淹渍对花椰菜根系活力和叶片光合特性的影响

以上海崇明岛花椰菜品种“崇花120天”为试材,于2014年8-11月人工气候室开展盆栽试验,将花椰菜植株根部分别淹水处理3、6、9、12、15d,以正常灌溉为对照（CK）,测定花椰菜的根系活力和叶片光合参数等指标。结果表明：(1)随着淹渍胁迫时间的延长,花椰菜的根系活力呈不同程度的降低。当淹渍胁迫超过9d后,根系活力趋于0;(2)与CK相比,淹渍胁迫3、6、9、12和15d时,叶片最大净光合速率分别下降4.90%、68.13%、78.71%、90.92%和98.68%,与此同时,光补偿点降低、光饱和点也随之增大;(3)淹渍胁迫下花椰菜气孔导度、蒸腾速率和胞间CO2浓度明显下降,淹渍胁迫初期,气孔限制值增大。说明胁迫初期影响花椰菜净光合速率下降的因素为气孔限制因子。(4)淹渍胁迫前6d各项指标下降明显,之后趋于稳定,可以确定淹渍胁迫第6天为致灾临界指标。     

苜蓿结实格局及其影响因素的研究

用生殖生态学的相关方法，对不同生长年限的新牧1号杂花苜蓿结实格局进行测定，并对其影响因素进行分析。不同生长年限的苜蓿，在群体水平上上、中、下不同冠层和花序水平上上、中、下不同位置，均具有明显不同的结实特点。1年生在初花期光合产物积累不足，到末花期又出现了资源的限制。从而制约了种子产量的形成。3年生初花期传粉不足。盛花期的营养生长和生殖生长的资源争夺，结荚期的资源限制，成为产量形成的重要制约因素。传粉和资源限制是影响苜蓿结实格局的主要原因。在荚果水平上。苜蓿荚果内种子在形成过程中表现出明显交替败育的趋势，其中从果实基部算起偶数位置的胚珠形成种子的机会更大。资源限制和邻近种子争夺资源的干扰是导致荚果内种子交替性败育格局的主要原因。     

Leaf stoichiometry and resorption of N and P in Lucerne at different growth stages under different water supplies

Drought affects not only nutrient cycling but also the internal cycling in the plant. We conducted a greenhouse experiment with lucerne at low, moderate and high soil water levels (LW, MW and HW). Green-leaf N:P (N:P_gr) decreased at squaring and flowering stages as water supply increased, while senesced-leaf N:P (N:P_sen) increased mostly. N:P_gr increased with the growth at LW and MW, while hardly changed at HW. N:P_sen increased and then decreased with the growth at LW and HW, but increased at MW. Water supply may affect soil N or P limitation in a growth stage-specific way. Water supply barely affected leaf N resorption of lucerne, while enhanced leaf P resorption. P resorption was positively correlated with soil P limitation, while there was no relationship of N resorption with N limitation. Therefore, increased water supply would lead to enhanced P resorption to ameliorate the restriction of soil P limitation to lucerne growth.     

Moss-nitrogen input to boreal forest soils: Tracking 15N in a field experiment

Cyanobacteria living epiphytically on mosses in pristine, unpolluted areas fix substantial amounts of atmospheric nitrogen (N) and therefore represent a primary source of N in N-limited boreal forests. However, the fate of this N is unclear, in particular, how the fixed N₂ enters the soil and becomes available to the ecosystem. In this study, we applied ¹⁵N-ammonium chloride (¹⁵N-NH₄Cl) onto carpets of the feather moss Pleurozium schreberi and traced the ¹⁵N label into green (living) and brown (senescent) moss and into the upper soil layer over time. Further, we placed filters between moss and soil to assess the role of moss-associated fungi for N-transfer to the soil. The experiment was conducted at endpoints of a N₂ fixation gradient in Northern Sweden. Feather moss retained the applied N in the green moss parts for up to 1 year and no increase of excess ¹⁵N was found in the brown moss parts or in the soil within that same time frame. The filter treatment did not alter the ¹⁵N-distribution in moss or soil. Nitrogen retention in the moss was similar regardless of position along the N₂ fixation gradient. Our results suggest that mosses represent a short-term inorganic N sink and that transfer of N to the soil is not facilitated by fungal hyphae.