林地砍伐开垦对土壤酶活性及养分的影响

由土壤微生物生命活动和植物根系产生的土壤酶,不但在土壤物质转化和能量转化过程中起主要的催化作用,而且通过它对进入土壤的多种有机物质和有机残体产生的生命化学转化,使生态系统的各组分间有了功能上的联系,从而保持了土壤生物化学的相对稳衡状态［１］。土壤酶作...     

放牧牲畜粪便降解及其对草地土壤养分动态的影响研究进展

放牧牲畜粪便沉积是影响草地土壤养分动态的重要途径之一,粪便降解过程调控着其养分返还效率,从而可能对草地土壤养分平衡和植被生长的养分供应等产生重要影响。针对放牧牲畜排粪行为特性、牲畜粪便的物质组成及其降解过程、以及粪便养分归还对土壤养分动态的影响等进行了系统论述,阐明了牲畜粪便降解与其养分迁移转化的关系,以及粪便养分输入对放牧草地生态系统养分生物地球化学循环的影响效应和可能的作用机制,以期为加深对牲畜粪便降解的养分动态变化过程的认知和厘清粪便-植物-土壤体系养分迁移和转化的影响机制积累理论基础,进而为优化牲畜粪便管理模式、维持土壤养分平衡和促进草地生态系统的健康协调和可持续发展提供科学依据。     

土壤真菌群落生态特征与养分转化

土壤真菌是腐生或共生在土壤中及其有机质层或母质层中的最大类群的微生物区系,其优势度和多样性是随着土壤类型和植被而变化的,生态扰动会影响其群落构成．抑菌作用是土壤真菌适应环境的生理现象,可以被利用和解除．土壤真菌不仅与土壤胶体链合构成菌丝桥,而且参与土壤碳、氮、磷等养分转化．因而土壤真菌是土壤中最为重要的微生物类别．     

土壤增温和秸秆还田对土壤养分和胞外酶活性的影响

气候变暖和秸秆还田是影响农田生态系统碳氮循环和土壤养分周转的重要因子,然而两者的交互作用尚缺乏系统研究。通过大田模拟试验,设置土壤正常温度+秸秆不还田、土壤正常温度+秸秆还田、土壤增温+秸秆不还田和土壤增温+秸秆还田四个处理,探讨土壤增温与秸秆还田对土壤养分循环及胞外酶活性的影响。结果显示,土壤增温使硝态氮含量、土壤可溶性有机碳含量和氧化酶活性分别增加了40.4%,25.8%和6.0%,但也使土壤水分、铵态氮含量与土壤微生物量碳分别损失了10.6%,33.4%和29.9%。秸秆还田则使土壤含水量、全氮、铵态氮、有效磷与可溶性有机碳的含量分别增加了7.5%,7.2%,44.1%,32.3%和18.4%,同时也使土壤碳氮磷循环酶的活性分别增加了46.2%,22.9%和20.6%。因此研究表明,土壤增温提高了氧化酶的活性,加速了土壤碳的转化,也使土壤氮矿化与硝化反应速率提高。秸秆还田通过增加外源有机物质,丰富了土壤的碳、氮源,使土壤养分含量提高,一定程度上弥补了增温带来的养分损失。     

林地覆盖经营雷竹林叶片养分特征及其与土壤养分的关系

探讨了短期覆盖经营(覆盖1 a)、休养式覆盖经营(覆盖3 a 后休养3 a)、长期覆盖经营(覆盖6 a)和不覆盖雷竹林(CK)2年生立竹叶片养分含量、化学计量比和再吸收率及其与土壤养分的关系。结果表明：(1)短期和休养式覆盖经营促使雷竹叶片养分含量和再吸收率总体上提高,而长期覆盖经营对雷竹叶片 P 含量和N、K 再吸收率会产生较为明显的影响,叶片 P 含量、N 再吸收率显著升高,K 再吸收率降低;(2)短期和休养式覆盖经营对雷竹林土壤、叶片养分化学计量比影响不明显,但长期覆盖经营使雷竹林土壤、叶片 N∶P、K∶P 显著降低;(3)短期覆盖经营能增强雷竹林土壤养分与叶片的养分含量、化学计量比和养分再吸收率的相关性,但随覆盖经营年限的延长,相关性总体上呈减弱趋势;(4)土壤养分含量及其平衡关系对林地覆盖经营雷竹林叶片养分特征影响明显;(5)长期覆盖经营雷竹林土壤、叶片养分间相关性明显减弱,竹子吸收利用养分的能力下降,生产中应实行雷竹林休养式覆盖经营方式。研究结果为林地覆盖经营雷竹林的可持续发展提供了理论参考。     

湿地松混交林地土壤养分、微生物和酶活性的研究

1　引　　言土壤养分、微生物和酶是森林生态系统的重要组成成分 .土壤养分含量对林木生长有重要影响 .土壤微生物参与土壤的物质循环和能量转化[16] ,而土壤酶参与土壤的许多重要的生物化学过程和物质循环[18] ,二者一起推动着土壤的代谢过程 ,影响着林木生长 .长期以来 ,有关森林土壤养分、微生物和酶的研究受到广泛重视[4 ,6～ 2 0 ] .黎蒴栲 (Ｃａｓ ｔａｎｏｐｓｉｓｆｉｓｓａ)、红荷 (Ｓｃｈｉｍａｗａｌｌｉｃｈｉｉ)和湿地松 (Ｐｉｎｕｓｅｌ ｌｉｏｔｔｉｉ)是我国南方重要的用材树种 ,但是关于黎蒴栲×湿地松及红荷×湿地松混交…     

火烧对古尔班通古特沙漠土壤养分和土壤酶活性的影响

以古尔班通古特沙漠2016年6月意外火烧事件为背景,对比分析火烧和未火烧样地区不同土壤深度化学性质、土壤酶活性的变化特征,为全面评估火烧对温带荒漠生态系统的影响提供土壤学依据。结果表明:火烧样地和对照样地土壤养分含量和酶活性总体上均表现为上层土壤(0—5 cm)大于下层土壤(5—10 cm),仅土壤氧化酶(过氧化氢酶)活性表现为下层土壤大于上层土壤。同时,火烧和土壤深度存在交互效应,火烧对土壤特性的影响受土壤深度的限制。土壤化学性质受火烧的影响主要表现在0—5 cm土壤层,尤其是速效养分在火烧之后有显著增加趋势。火烧对5—10 cm土壤层土壤化学性质无显著影响。火烧后,硝态氮(NO3-N)含量显著下降,铵态氮(NH4-N)含量上升。土壤水解酶、氧化酶活性在火烧之后降低,具体表现为,蔗糖酶、脲酶、β-葡萄糖苷酶活性在0—5 cm和5—10 cm土壤层均极显著下降,而碱性磷酸酶活性仅在0—5 cm土壤层显著下降。过氧化氢酶活性则在5—10 cm土壤层活性显著下降。表明上层土壤水解酶活性对火烧干扰较为敏感,氧化酶活性在火烧干扰下相对稳定。从各土层土壤酶活性的变化特征来看,火烧对水解酶活性的影响随土壤深度增加而降低,而氧化酶则呈现相反的趋势。总体而言,火烧显著提高了古尔班通古特沙漠土壤速效养分的含量,降低了土壤酶活性,不同土壤酶对火烧响应的敏感程度不同。为深入评估火烧干扰对温带荒漠生态系统的影响提供一定理论依据。     

三峡库区不同林龄马尾松土壤养分与酶活性的关系

基于对三峡库区不同林龄马尾松林下土壤养分和酶活性的测定及典范对应分析,探讨了不同林龄马尾松林土壤养分、酶活性特征及其相互关系.结果表明:马尾松林0 ～ 20 cm土壤有机质、总氮、铵态氮和有效磷含量均表现出成熟林＞中龄林＞近熟林;随着林龄的增加,土壤转化酶活性先降低后增加,纤维素酶、多酚氧化酶活性逐渐降低,而脲酶和过氧化物酶活性先增加后降低.经典范对应分析,不同林分中主要土壤养分对酶活性的影响顺序为总氮＞有机质＞pH＞容重＞铵态氮＞有效磷,转化酶与土壤有机质、总氮、总磷呈显著正相关,过氧化物酶与有机质、总氮、总磷、容重呈显著负相关,土壤主要养分含量高,转化酶活性较高,过氧化物酶活性相对较低.转化酶、纤维素酶和过氧化物酶是评价土壤质量及肥力较好的生物学指标.     

不同林龄刺槐叶片养分重吸收特征及其对土壤养分有效性的响应

为揭示丘陵沟壑区刺槐的养分重吸收特征及其驱动因素,研究该区不同林龄刺槐叶片全氮和全磷的浓度,以及土壤有机碳、全氮、全磷、铵态氮、硝态氮和速效磷浓度及其化学计量,分析了叶片氮磷重吸收效率与土壤养分特性之间的关系。结果表明: 植物和土壤的养分随林龄增长发生显著变化,而土壤总磷和速效磷浓度较低。氮重吸收效率随林分生长先增加后降低,范围为48.2%～54.0%,平均为48.5%;磷重吸收效率则显著增加,范围为45.2%～49.4%,平均为46.9%。氮重吸收效率与土壤氮素和氮磷比呈负向响应,而磷重吸收效率与氮磷比呈显著正相关,与土壤速效磷呈负相关。表明土壤养分有效性的变化负向驱动养分重吸收效率。由于该生境中刺槐林的固氮效应及磷限制,叶片养分重吸收策略对土壤氮磷比响应强烈。     

养分管理对农田土壤微生物量的影响

土壤微生物与土壤质量、健康、植物的生产力和农业的可持续发展密切相关。任何对土壤中微生物的扰动都可能影响土壤的长期生产力,并可能产生严重后果。大量研究结果表明,肥料类型、施肥处理年限长短、施肥水平高低及施肥措施都会造成土壤成分的变化,进而影响土壤中微生物的生长以及繁殖。简要介绍了微生物量的几种测定方法,综述了各种养分管理措施对农田生态系统中土壤微生物量的影响,从而了解土壤微生物因人类对土壤的利用而发生的变化,以期为农业的可持续发展和生态环境的保护提供理论依据。     

Ecosystem Nutrient Use Efficiency, Productivity, and Nutrient Accrual in Model Tropical Communities

Ecosystem nutrient use efficiency–the ratio of net primary productivity to soil nutrient supply–is an integrative measure of ecosystem functioning. High productivity and nutrient retention in natural systems are frequently attributed to high species diversity, even though some single-species systems can be highly productive and effective at resource capture. We investigated the effects of both individual species and life-form diversity on ecosystem nutrient use efficiency using model tropical ecosystems comprised of monocultures of three tree species and polycultures in which each of the tree species was coplanted with species of two additional life forms. Tree species significantly influenced nutrient use efficiency by whole ecosystems in monocultures; however, in polycultures, the additional life forms interacted with the influence exerted by the dominant tree. Furthermore, the presence of the additional life forms significantly increased nutrient uptake and uptake efficiency, but in only two of the three systems and 2 of the 4 years of the study period. These results indicate that the effect of life-form diversity on ecosystem functioning is not constant and that there may be temporal shifts in the influence exerted by different components of the community. Furthermore, although species (and life forms) exerted considerable influence on ecosystem nutrient use efficiency, this efficiency was most closely related to soil nutrient availability. These findings demonstrate that ecosystem nutrient use efficiency is an outcome not only of the characteristics of the species or life forms that comprise the system but also of factors that affect soil nutrient supply. The results argue against the simple upward scaling of nutrient use efficiency from leaves and plants to ecosystems. Received 29 March 2000; accepted 27 April 2001.     

River Nutrient Loads and Catchment Size

We have used a total of 496 sample sites to calibrate a simple regression model for calculating dissolved inorganic nutrient fluxes via runoff to the ocean. The regression uses the logarithms of runoff and human population as the independent variables and estimates the logarithms of dissolved inorganic nitrogen and phosphorus loading with R² values near 0.8. This predictive capability is about the same as has been derived for total nutrient loading with process-based models requiring more detailed information on independent variables. We conclude that population and runoff are robust proxies for the more detailed application, landscape modification, and in-stream processing estimated by more process-based models. The regression model has then been applied to a demonstration data set of 1353 river catchments draining to the sea from the North American continent south of the Canadian border. The geographic extents of these basins were extracted from a 1-km digital elevation model for North America, and both runoff and population were estimated for each basin. Most of the basins (72% of the total) are smaller than 10³ km², and both runoff and population density are higher and more variable among small basins than among larger ones.While total load to the ocean can probably be adequately estimated from large systems only, analysis of the geographic distribution of nutrient loading requires consideration of the small basins, which can exhibit significant hydrologic and demographic heterogeneity between systems over their range even within the same geographic region. High-resolution regional and local analysis is necessary for environmental assessment and management.     

三峡库区不同土地利用方式的养分流失研究

通过两年的定位实验,研究了三峡库工我５种代表性土地利用方式对养分流失的重要性。寝实验表明,不同土地利用方式的养分年输出总量有较大的变异,其变化趋势为坡地农田＞梯田农田＞梯田农田＞坡地果园。不同土地利用方式下,降雨量和降雨强度与系统径流量和含沙量的相关性都达到５％显著性水平。不同土地利用方式,其径流养分输出占系统养分总输出的比例明显不同。土地利用方式对系统Ｎ、Ｐ、Ｋ的径流输出影响显著。三峡库区脆弱生     

Effects of High Nutrient Supply on the Growth of Seven Bamboo Species

Over the last decade, bamboo has emerged as an interesting plant for the treatment of various polluted waters using plant-based wastewater treatment systems. In these systems, nitrogen and phosphorous concentrations in wastewater can exceed plant requirements and potentially limit plant growth. The effects of two nutrient rates on the growth of seven bamboo species were assessed in a one-year experiment: Dendrocalamus strictus, Thyrsostachys siamensis, Bambusa tuldoides, Gigantochloa wrayi, Bambusa oldhamii, Bambusa multiplex and Bambusa vulgaris. Nutrient rates were applied with a 20:20:20 NPK fertilizer as 2.6 and 13.2 t.ha.yr^?1NPK to three-year-old bamboo planted in 70 L containers. Morphological characters, photosynthetic responses, and NPK content in bamboo tissues were investigated. Under high-nutrient supply rate, the main trend observed was an increase of culm production but the culms’ diameters were reduced. For the seven species, the aboveground biomass yield tended to increase with high-nutrient rate. Increasing in nutrient rates also improved the photosynthetic activity which is consistent with the increase of nitrogen and phosphorus contents measured in plant tissues. All the bamboo species tested appears suitable for wastewater treatment purposes, but the species Bambusa oldhamii and Gigantochloa wrayi showed the higher biomass yield and nutrient removal.     

Root Development and Nutrient Uptake

Root system formation proceeds in close coordination with shoot growth. Accordingly, root growth and its functions are regulated tightly by the shoot through materials cycling between roots and shoots. A plant root system consists of different kinds of roots that differ in morphology and functions. The spatial configuration and distribution of these roots determine root system architecture in the soil, which in turn primarily regulates the acquisition of soil resources like nutrients and water. Morphological and physiological properties of each root and the concomitant tissues further affect nutrient uptake and transport, while the root traits that are related to such acquisition also depend on the kinds of nutrients and their mobility in the soil. In addition, mechanisms involved in the uptake and transport of mineral nutrients recently have been elucidated at the molecular level. A number of genes for acquisition and transport of various mineral nutrients have been identified in model plant systems such as Arabidopsis thaliana, and rice, and in other plant species. An integration of studies on nutrient behavior in soils and the morphological and physiological functions of root systems will further elucidate the mechanism of plant nutrient uptake and transport by roots, and offer a real possibility of genetically improving crop productivity in problem soils.

     

Nutrient stocks in managed and natural humid tropical fallows

Managed fallows which recover nutrients more rapidly than natural secondary vegetation may improve the performance of shifting agriculture systems operating under inadequately long fallow cycles. Our objective was to construct nutrient balances for the soil, vegetation, and litter compartments of six planted leguminous fallows and natural secondary vegetation during 53 months. The fallows were planted on a previously cultivated Ultisol (Acrisol) in the Peruvian Amazon and included:Centrosema macrocarpum (Centrosema),Pueraria phaseoloides (Pueraria),Stylosanthes guianensis (Stylosanthes),Desmodium ovalifolium (Desmodium),Cajanus cajan (Cajanus), andInga edulis (Inga). In addition, in the natural fallow treatment secondary vegetation was allowed to establish and grow naturally. Quantities of extractable P, K, Ca, and Mg, total N, and organic C in soil to a 45 cm depth, and macrouttrients in aboveground biomass, roots, and litter were estimated at fallow planting, at 8, 17, and 29 months afterward, and at fallow clearing (53 months). Total N stocks increased by 10% in the Stylosanthes, Desmodium, Pueraria, and Inga treatments, but changed little in the Cajanus, Centrosema and natural fallows. This difference was largely due to greater net increases in both soil and vegetation compartments in the former group of treatments. In the Inga, Desmodium, and natural fallows, total stocks of P and K at 53 months were about 40% to 80% greater and 12% greater, respectively, than initial values, but Ca and Mg stocks were reduced by 25% to 40%. In the other treatments, there was generally little change in P stocks, but large (30% to 60%) reductions in K, Ca, and Mg during the course of the fallow. Although there were net decreases of stocks of P, K, Ca, and Mg in soil in all treatments during the fallow, storage of P and K in vegetation and litter in the Inga, Desmodium, and natural fallows offset losses of these nutrients from soil. These treatments also tended to accumulate more Ca and Mg in biomass and litter than the other treatments. These results suggest that leguminous fallow vegetation that accumulates large amounts of biomass may increase N, P, and K stocks, but that incomplete recuperation of Ca and Mg may limit the sustainability of short-rotation fallow-based systems on acidic, infertile soils. ei]Section editor: G R Stewart     

Nutrient cycling strategies

This paper briefly reviews pathways by which plants can influence the nutrient cycle, and thereby the nutrient supply of themselves and of their competitors. Higher or lower internal nutrient use efficiency positively feeds back into the nutrient cycle, and helps to increase or decrease soil fertility. These tendencies are further enhanced by secondary effects (higher or lower rates of decomposition of litter and hence of nutrient mineralization) in resp. fertile and infertile soils. Such feedbacks may strongly increase the fitness of the plants involved. Plants can also influence the external inputs and outputs into the plant-soil system, by affecting the general hydrology of their environment. Sphagnum peat bogs exemplify an extreme degree of control of plants over the hydrological cycle, causing intense nutrient impoverishment by making the ecosystem dependent on nutrient supply from the atmosphere, apparently giving Sphagnum a competitive edge over other plants.     

Nutrient cycling and foodwebs in Dutch estuaries

In this review several aspects of the functioning of the Dutch estuaries (Ems-Dollard, Wadden Sea, Oosterschelde, Westerschelde, Grevelingen and Veerse Meer) have been compared. A number of large European rivers (especially Rhine) have a prevailing influence on the nutrient cycling of most Dutch estuaries. Owing to the increased loading of the estuaries with nitrogen and phosphorus compounds, effects of eutrophication on the biological communities could be demonstrated, mainly in the western Wadden Sea. The causality, however, of the relation between increased nutrient loading and increased biomass and production of primary producers in the turbid tidal Dutch ecosystems is questioned. The most obvious biological effects of eutrophication have been observed in a non-tidal brackish lagoon, Veerse Meer. The estuarine food web received major attention. Budget studies of the main primary producers revealed a dominance of phytoplankton in all Dutch estuaries, followed by microphytobenthos in the tidal systems and macrophytes in the lagoons. The quantitative distribution of primary producers and primary and secondary consumers shows remarkable similarities along the physical and chemical estuarine gradients, notwithstanding the large variability in space and the considerable inconstancy over time. Among the secondary consumers (waterfowl, marine fish, larger invertebrates) the levels of organic carbon consumption — expressed in g C m⁻² y⁻¹ — are almost the same, when tidal estuaries are compared with non-tidal lagoons, notwithstanding the fact that the consumer populations show large qualitative differences. The transfer from primary consumers to secondary consumers reveals a bottle neck: especially during late winter, when macrozoobenthos reaches its lowest biomass, food may be a serious limiting resource for large numbers of migratory waders foraging on the intertidal flats. The consequences of the Deltaplan, the closure of several estuaries in the southwest of the Netherlands and their subsequent transfer into non-tidal lagoons, offer complicated case studies of ecosystem changes. Several examples of long-term trends in ecosystem development in Grevelingen lagoon have been discussed.     

Uncertainty in Nutrient Spiraling: Sensitivity of Spiraling Indices to Small Errors in Measured Nutrient Concentration

Abstract Proper assessment of ecological data must consider uncertainty. However, reported estimation of uncertainty in calculated values of nutrient spiraling indices is rare. Interpretations based on single values of spiraling indices, may therefore be unwittingly flawed. We investigated the sources of analytical uncertainty in the nutrient concentrations used to calculate two spiraling indices, uptake length (S _w ) and uptake velocity (V _f ), and used Monte Carlo Simulation (MCS) to estimate the resultant uncertainty in index values. We also examined the effect of the level of nutrient enrichment on the magnitude of index uncertainty. Outcomes under high and low nutrient uptake capacity were compared by performing nutrient addition experiments in two streams with contrasting ambient nutrient concentrations. We found that small differences (or uncertainties) in the average plateau nutrient concentration resulted in large uncertainties in spiraling indices. The uncertainty resulted from a combination of small differences in nutrient concentrations between upstream and downstream stations (particularly for the low uptake case), the low nutrient concentration added into the stream, and the sample matrix and storage. The stream with low nutrient uptake capacity had larger relative uncertainties in S _w than when the nutrient uptake capacity was high. The presence of such errors demands that S _w and V _f values should be reported with uncertainty, rather than the normal practice of a single calculated value. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Nutrient cycling in an excessively rainfed subtropical grassland at Cherrapunji

Cycling of six mineral elements (N, P, K, Na, Ca and Mg) was studied in a humid subtropical grassland at Cherrapunji, north-eastern India during 1988-1989. Elemental concentrations in the shoot of four dominant grass species,viz., Arundinella khaseana, Chrysopogon gryllus, Eragrostiella leioptera andEulalia trispicata were very low, and none of the species appears suitable for fodder use. Among different vegetation compartments, live root was the largest reservoir of all the nutrients (except Ca) followed by live shoot, dead shoot, litter and dead root. For Ca, live shoot was the major storage compartment. The total annual uptake (kg ha^-1) was 137.3, 10.4, 51.1, 5.5, 8.7 and 18.2 for N, P, K, Na, Ca and Mg, respectively. In an annual cycle 98% N, 77% P, 49% K, 109% Na, 87% Ca and 65% Mg returned to the soil through litter and belowground detritus. A major portion of N, P and Na was recycled through the belowground system, whereas nearly half of K, Ca and Mg was recycled through the shoot system. Precipitation acts as the source of N and P input, but at the same time causes loss of cations.