Decomposition of Metrosideros polymorpha leaf litter along elevational gradients in Hawaii

We examined interactions between temperature, soil development, and decomposition on three elevational gradients, the upper and lower ends of each being situated on a common lava flow or ash deposit. We used the reciprocal transplant technique to estimate decomposition rates of Metrosideros polymorpha leaf litter during a three‐year period at warm and cool ends of each gradient. Litter quality was poorest early in soil development or where soils were most intensely leached and waterlogged. In situ litter decomposition was slowest on the young 1855 flow (k= 0.26 and 0.14 at low and high elevation, respectively). The more fertile Laupahoehoe gradient also supported more rapid in situ decay at the warmer low elevation site (k= 0.90) than at high elevation (k= 0.51). The gradient with the most advanced soil development showed no difference for in situ decay at low and high elevations (k= 0.88 and 0.99, respectively) probably due to low soil nutrient availability at low elevation, which counteracted the effect of warmer temperature. Comparisons of in situ, common litter, and common site experiments indicated that site factors influenced decomposition more than litter quality did. The effect of temperature, however, could be over‐ridden by soil fertility or other site factors. Field gradient studies of this sort yield variable estimates of apparent Q₁₀, even under the best conditions, due to interactions among temperature, moisture, nutrient availability, decomposer communities and litter quality. Such interactions may be as likely to occur with changing climate as they are along elevational gradients.     

Weathering versus atmospheric sources of strontium in ecosystems on young volcanic soils

We used isotopes of Sr to quantify weathering versus atmospheric sources of foliar Sr in 34 Hawaiian forests on young volcanic soils. The forests varied widely in climate, and in lava flow age and texture. Weathering supplied most of the Sr in most of the sites, but atmospheric deposition contributed 30–50% of foliar Sr in the wettest rainforests. A stepwise multiple regression using annual precipitation, distance from the ocean, and texture of the underlying lava explained 76% of the variation in Sr isotope ratios across the sites. Substrate age did not contribute significantly to variation in Sr isotope ratios in the range of ages evaluated here (11–3000 years), although atmospheric sources eventually dominate pools of biologically available Sr in Hawaiian rainforests in older substrates (≥150,000 years). Received: 25 January 1999 / Accepted: 23 June 1999     

广州南沙区4种典型城市林业土壤质量调查研究

为掌握广州南沙区城市林业土壤养分及肥力整体状况,提高广州南沙区城市林业土壤管养水平,以广州南沙区4种典型城市林业土壤(森林公园、湿地公园、生态景观林带、河涌防护林)为研究对象,测定土壤pH值、电导率、容重、渗透率、非毛管孔隙度、有机质、水解氮、有效磷、速效钾等9项理化指标,通过土壤理化性质分析、土壤综合肥力分析,对广州...     

不同林龄马尾松凋落物基质质量与土壤养分的关系

凋落物的质量、数量及分解速率在一定程度上代表了土壤的营养状况。为了精确估算凋落物分解对土壤碳库的年净归还量及凋落物-土壤生物化学连续体的深层理解,从凋落物基质质量的角度分析了三峡库区不同林龄马尾松凋落物基质质量与土壤养分的作用关系,结果表明:中龄林、近熟林、成熟林马尾松凋落物基质质量中的C、C/N比、C/P比、木质素/N比、木质素/P比差异显著,其中近熟林凋落物叶木质素/N分别比中龄林和成熟林的高33.65%、39.24%,N、P、K、木质素含量差异不显著;但各组织器官的N、P、K含量差异显著,均是皮<枝<叶<杂物,C/N比、C/P比的变化则相反。不同林龄马尾松0-20 cm(0-5 cm、5-10 cm、10-20 cm)土壤有机质、总氮、有效磷含量均表现出近熟林<中龄林<成熟林,0-5 cm最大,10-20 cm最小,且随着土壤深度的增加而明显降低,总磷则是中林龄最低,成熟林最大,pH值则各土层均表现为中龄林<成熟林<近熟林,平均pH值为4.55-5.51。凋落物基质质量指标与土壤养分之间冗余分析(RDA)表明:马尾松凋落物基质质量和土壤养分之间关系紧密,N、P、纤维素、半纤维素、木质素、木质素/N比、C/N比对土壤养分影响比较大;凋落物中木质素/N比、C/N比与土壤有机质呈显著负相关,其含量越高越不利于土壤有机质的形成,土壤养分积累的越慢;凋落物基质质量氮含量与土壤氮含量呈显著正相关;土壤pH值、容重与N含量呈显著负相关,与凋落物C/N比、木质素/N比呈显著正相关。马尾松土壤表面有机质、N、P养分含量与凋落物基质质量对应养分含量变化规律一致,土壤养分高,凋落物基质质量相对较高,土壤贫瘠,凋落物基质质量相对较低。     

The Microbial Efficiency‐Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

The decomposition and transformation of above‐ and below‐ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant‐derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency‐Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix.     

全球植物凋落物纤维素分解速率的变化特征及其影响因子

纤维素作为凋落物的关键组分之一, 其分解过程在陆地生态系统碳循环中具有重要作用。该研究汇集了现有研究关于凋落物纤维素分解的时间序列数据, 根据一级指数动力学方程估算了凋落物纤维素分解常数(k), 探索了k在不同气候带、生态系统和叶形态的分布格局, 以及气候、地形、土壤性质、凋落物底物质量对k的影响。结果表明: (1) k在不同气候带与叶形态上差异显著, 表现为: 热带(0.086) >亚热带(0.069) >温带(0.048), 阔叶树种(0.069) >针叶树种(0.059); (2)考虑了随机效应后, k随凋落物初始碳氮比、木质素纤维素比增加而下降, 而随年平均气温升高而增加。该结果表明, 凋落物底物质量和气候对纤维素分解具有重要影响。该研究深化了对凋落物纤维素分解规律的认识, 有助于优化植物凋落物周转和生态系统碳循环模型。     

喀斯特峰丛洼地植被演替过程中土壤养分的积累及影响因素

以桂西北环江县典型喀斯特峰丛洼地为对象,利用空间代替时间的方法,于2009年分析了植被演替过程中表层土壤(0～15 em)养分的变化及其主要控制因素.结果表明:随着植被正向演替(草地-灌丛-次生林-原生林),表层土壤的有机碳、全氮和全磷等含量显著增加,分别由演替初期(草地)的29.1、2.48和0.72 g·kg-1增加为演替后期(原生林)的73.9、8.10和1.6g·kg-1.土壤阳离子交换量与有机碳和全氮密切相关,是喀斯特土壤C、N积累的主要控制因素;凋落物中的P含量、C/P和N/P是土壤全磷积累的主要控制因素,较高的凋落物P含量、N/P以及较低的C/P有利于土壤中P的积累;而坡度、坡向和裸岩率等地形因子对土壤养分的影响较小.     

降水量变化对蒙古栎落叶分解过程的间接影响

分析了在4种不同降水量条件下蒙古栎叶凋落物基质质量的变化,并应用分解袋法研究其凋落物在蒙古栎次生林内的分解过程.结果表明：与对照相比,降水量减少条件下,蒙古栎叶凋落物的初始N、P、K浓度显著升高,初始木质素浓度显著降低,凋落物分解速率大,N、P、K矿化率高,N和P固持时间缩短;降水量增加情况下,其凋落物初始N浓度显著降低、木质素浓度显著升高,N、P、K矿化率低,N和P固持时间延长.4种类型叶片凋落物的质量损失过程均符合指数降解模型,分解速率可以由凋落物木质素/N来预测.相关性分析显示,木质素浓度高、N浓度低的两种凋落物的分解速率与N浓度相关性最大;而木质素浓度低、N浓度高的两种凋落物的分解速率与木质素浓度相关性最大.说明降水量的变化显著地改变了蒙古栎叶凋落物的基质质量,进而间接地改变了凋落物的分解过程.     

Determinants of Leaf Litter Nutrient Cycling in a Tropical Rain Forest: Soil Fertility Versus Topography

We investigated the influence of landscape-level variation in soil fertility and topographic position on leaf litter nutrient dynamics in a tropical rain forest in Costa Rica. We sampled across the three main edaphic conditions (ultisol slope, ultisol plateau, and inceptisol) to determine the effect of soil nutrients on leaf litter nutrient concentrations while controlling for topography, and to examine topographic effects while controlling for soil nutrients. Both leaf litter macronutrient [phosphorus (P), nitrogen (N), sulfur (S), calcium (Ca), potassium (K), magnesium (Mg)] and micronutrient concentrations were quantified throughout a 4-year period. Leaf litter [P], [N] and [K] varied significantly among soil types. The variation in [P], [N], and [K] was explained by soil fertility alone. Leaf litter [S], [Ca], and [Mg] did not vary among the three soil types. Macronutrient (P, K, Mg, S, Ca) concentrations in the leaf litter were much less variable than those of Fe and Al. Lower variability in essential plant nutrients suggests a great deal of plant control over the amount of nutrients resorbed before senescense. Leaf litter macronutrient concentrations varied significantly over the 4-year period, but the temporal variation did not differ among the three edaphic types as anticipated. Hence, although the magnitude of nutrient fluxes may be controlled by local factors such as soil fertility, temporal patterns are likely regulated by a common environmental variable such as precipitation or temperature.     

不同林窗马尾松凋落叶与土壤养分变化研究

以现有42年生的马尾松（Pinus massoniana）人工纯林;经过采伐形成4种不同大小有效面积的林窗（100、400、900和1 600 m²）为研究对象;以未经采伐的42年生马尾松人工纯林为对照样地;采用凋落叶分解袋法;研究不同大小有效面积林窗对马尾松凋落叶、土壤C、N、P及化学计量比和养分损失率的影响。研究结果表明:（1）不同大小有效面积林窗下的马尾松凋落叶、土壤C、N、P含量及养分损失率除土壤P含量和马尾松凋落叶P养分损失率外;均存在显著差异。随着林窗有效面积G1~G4的增大;马尾松凋落叶C、N、P含量均呈降低趋势;三者均在G3林窗体现出较小值。马尾松凋落叶C、N、P养分损失率、土壤C、N、P养分含量多呈抛物线趋势;且均在G2或G3林窗体现出最大值。（2）不同大小有效面积林窗下的马尾松凋落叶、土壤C/N/P均存在显著差异。随着林窗有效面积G1~G4的增大;马尾松人工林土壤C/N/P基本呈抛物线变化趋势;土壤C/N在G3林窗出现最大值;土壤C/P、N/P均在G2林窗体现出最大值;土壤C/N、C/P、N/P变异系数分别为13.31%、16.51%、17.21%。马尾松凋落叶C/N、C/P均在G3体现出最小值。（3）马尾松凋落叶C、N含量与土壤C、C/N/P及环境因子的相关性较强;P含量与它们的相关性较弱;C/N与土壤P、C/N/P及环境因子的相关性较强;C/P、N/P与土壤C/P及环境因子的相关性较强;C、N养分损失率与土壤C、C/N、C/P及环境因子的相关性较强;P养分损失率与土壤C、N、P含量及其化学计量比和环境因子的相关性较弱。土壤C、N、P含量及其化学计量比与环境因子的相关性较强。     

Effects of nutrient additions on litter production and nutrient return in a nutrient-poor Cape fynbos ecosystem

Litter production and N and P return were determined at bimonthly intervals for two years in 10×5 m plots, amended with a complete factorial fertilizer addition of N as NH₄NO₃(N_a), P as Ca₃(PO₄)₂(P_a) and a mixture of all essential nutrients excluding N and P (M_a) in a 4–7-year-old post-fire sand-plain lowland fynbos ecosystem, South Africa. Litter production increased with vegetation age, was highly seasonal and peaked from late spring to mid-summer (November to January). No significant differences in annual litter production and N return were found in response to the nutrient treatments, although both tended to increase during the second year in response to N_a and M_a. Phosphorus return increased significantly with P_a, and to a lesser extend, N₃, during the first year, whereas it increased in response to N_a and M_a and decreased in the P_a amended plots during the second year. The nutrient treatments did not result in a change in the timing of the annual peak litter production period or in the plant growth form composition of the litter. The litter layer dry mass and N and P contents increased in response to N_a and M_a, while P_a resulted in an increased P content. The evidence from this study indicates that the vegetative growth of the evergreen sclerophyllous shrubs and hemicryptophytes of sand-plain lowland fynbos is not only limited by N, as shown by other studies on shoot growth and vegetation cover, but also by one or more other nutrients excluding P.     

中亚热带木本植物各器官凋落物分解特性

植物因资源条件的差异形成不同的生态对策以获取养分进行代谢,具有不同的植物功能性状,从而可把植物凋落物分解特性与生态对策联系起来。为探究中亚热带地区木本植物凋落物分解特性与生态对策的关系,选取两种生态系统中的植物物种的地上、地下各器官凋落物(包括细根、粗根、细枝和叶片),采用分解袋法在两种土壤基质中(砂岩与石灰岩)进行为期2a(凋落叶片为1a)的分解实验,同时进行交叉实验。分解1a及2a的各器官凋落物间分解常数的关系采取Pearson相关性分析,并用SMA进行线性回归,结果表明植物各器官凋落物间的分解具有正相关关系,且分解1a后的细根与粗根、细根与细枝及分解2a后的细根与粗根呈现出显著正相关;而比较常绿植物及落叶植物凋落物在两种土壤基质和两种物种来源分解1a后的差异,除枝条外落叶植物凋落物的分解常数都大于常绿植物,在0.05置信水平上呈现出显著差异性。植物各器官凋落物间的分解具有一致性,不同生活型植物的各器官间的分解速率在不同物种来源或不同土壤基质中都表现出相似的差异。     

不同石漠化草地凋落物对土壤养分的贡献

凋落物是草地生态系统的重要组成部分和养分循环的重要途径,为探明草地凋落物对土壤养分的贡献,于2017年3月至2018年1月,采用土钻法、收集器法和分解袋法研究3种石漠化(潜在、中度和强度)草地凋落物的产量、组成、分解、养分释放及对石漠化的响应.结果表明:3种石漠化草地的凋落物组成以叶为主,占比84.39％—89.73％...     

Establishment of mixed plantations of Pinus sylvestris var. mongolica and Populus × xiaozhuanica may not be appropriate: evidence from litter decomposition

AimsMongolian pine (Pinus sylvestrisvar.mongolica) and Xiaozhuan poplar (Populus × xiaozhuanica) are two predominant afforestation tree species in the semi-arid sandy lands of northeast China, which are characterized by poor soil nutrients. Plant litter decomposition plays a critical role in regulating nutrient cycling in terrestrial ecosystems. Admixture of broadleaf litter to conifer litter is expected to improve litter decomposition and soil fertility, and thus productivity. However, the effects on the decomposition of litter mixture of the above two tree species are not well understood. Therefore, it is essential to assess the decomposition performance of litter mixture with the aim of improving forest nutrient management and the establishment of mixed plantation. Appropriate forest management practice is critical for the sustainability of site productivity in plantation forests.