Litterfall as a measure of primary production in Mediterranean holm-oak forest

In this paper we discuss the use of litterfall as a method to measure primary production and its between year relation to climatic fluctuation. Seven years of study in a mediterranean holm-oak forest showed a moderate inter-annual variability of litterfall (C.V. 11%), while the annual variability of the actual evapotranspiration was three times higher (C.V.30%). Furthermore, the inter- and intra-annual variability of nutrient content in the various fractions are presented in relation to water availability. Monthly and seasonal variability was higher than the annual variability for all analyzed elements.     

浙江天童常绿阔叶演替过程凋落物数量及分解动态

 浙江天童常绿阔叶林演替过程森林凋落物量呈增长趋势,其中：乔木叶比例最大,其它器官组分在不同演替阶段的比例不一致,灌木叶和草本、树皮比例随着演替进程而呈减少趋势,树枝和繁殖器官则呈增大趋势。以分解袋法测得凋落物年失重率和指数方程模拟的分解系数K在演替过程中均呈增长趋势,这与年凋落物数量变化趋势相似。可见,随着演替进程,生物循环加快,群落自肥能力增强。     

不同坡位对琉球松人工林凋落物及其养分归还量的影响

对日本冲绳岛北部不同坡位的琉球松人工林凋落物量及其养分归还量进行了为期3年的观测研究,结果表明,琉球松成林年凋落物量为6．54～8．05Mg·hm^-2·年^-1,其凋落高峰出现在6、7月份．台风干扰对年凋落物量及其季节动态影响显著．凋落物不同组分的养分含量差异明显．年均养分归还总量为113．4～154．6kg·hm^-2·年^-1,其中氮素归还量最大,占42．2％;各养分归还量的大小依次为N>Ca>K>Mg>Na>P．两调查林分由于立地条件的显著差异,年均凋落物量及其相应的养分归还量亦存在明显差异．在立地条件较好的下坡,林分P1的年均凋落物量达8．05Mg·hm^-2·年^-1,高于立地条件相对较差的上坡的林分P2的23．1％;其相应的年养分归还量为：N66、04,P1.63,K17．42,Ca48.31,Mg14.65和N。6、57kg·hm^-2·年^-1,分别高于林分P2的39.7％、48.8％、39．4％、32.9％、24.8％和49.3％．两林分凋落物的养分利用效率分别是N为122和138,P为4934和5945,K为462和523,林分P1明显低于林分P2,这与林分P2的立地条件较差相关．可见,所调查的琉球松林是一种高效的养分利用系统。     

三大硬阔树体动态结构的研究Ⅱ.叶的生长与死亡过程

对胡桃楸、水曲柳和黄菠萝叶出生和死亡过程的分析表明,它们的叶出生是一个渐进过程,持续期可达40～65d,不同时期出生的叶可形成明显的龄级结构。小叶生长过程基本上呈S型。叶死亡过程可分为小叶和复叶两种情况,初期落叶以小叶为主,凋落量少、速度慢;而后整个复叶才开始凋落,使落叶数量和速度加快,整个落叶期仅在30～35d左右。小叶凋落过程属于DeeveyⅠ型存活曲线,复叶凋落过程基本符合DeeveyⅡ型存活曲线。     

Litterfall and Leaf Consumption by Animals in Humid Seasonal Rainforest in Xishuangbanna,China

Litterfall and element return dynamic and leaf consumption by animals were studied in humid seasonal rainforest in Menglun, Xishuangbanna, Southwesten China. 1. The litterfall was l1.29+l.96t/ha·a, and the amount of litterfall component was (t/ha·a±S. E.): for leaves, 7.41±0.82; wood (≤2 cm diameter), 2.16±1.78; flowers, 0.223±0.13; fruits, 0.7244±0.456 and mixed matter (includs plant trash, wastes of animals and died animal bodies from canopy), 0.77±0.18. A marked peak of litterfall occurred during a March-April period of the late dry season. 2. Large wood litterfall (>2 cm diameter) was measured twice during rainy season and dry season, the large wood litterfall mean was 0.82t/ha·a. 3. Returns (kg/ha·a) of the elements to the forest floor in the litterfall were ranged Ca (146.4) > N (57.3) > Mg (39.0) 3> K(31.2) > P (6.33) > Mn (5.49) 2> A1(4.40) > Fe(1.92) > Zn(0.56) > Cu (0.24).and a marked peak of element return coincided with the litterfall's. 4. The leaf area eaten by animals accounted for 16.2% of the total leaf area.     

小良热带人工混交林的凋落物及其生态效益研究

对小良热带人工混交林１０年凋落量及其季节和年际动态研究表明,小凋落物总量年均５．５３９ｔ·ｈｍ－２;凋落量的季节变化明显,一般以湿季的７月为凋落高峰;随着人工林的发育,其凋落物量的年际变化逐渐稳定;森林枯枝落叶层贮量为４．９ｔ·ｈｍ－２,少于其年均凋落量,处于分解大于积聚的周转过程中;森林枯枝落叶层的存在可降低温度,提高湿度,显著减少径流量和泥沙流失量,并可提高土壤肥力和增加土壤动物的多样性．     

Is nutrient availability related to plant nutrient use in humid tropical forests?

Data on soil nutrient availability for humid tropical forests are often reported, but are rarely integrated in an ecologically meaningful way with other measures of nutrient cycling. In this paper, estimates of soil nutrient availability and the inverse of litterfall nutrient concentrations (as an index of plant nutrient use) were compared, using data from 36 sites throughout the humid tropics, to determine if relationships exist between commonly used indices of nutrient cycling for plants and soils. Measures of both extractable and total soil P were significantly and positively correlated with the ratio of litterfall mass/P, particularly for montane tropical forests. Extractable soil P was also significantly correlated with litterfall mass for lowland humid tropical forests, explaining 58% of the variability in litterfall mass. A weak, albeit significant correlation was found between exchangeable soil Ca and litterfall mass/Ca, even though soil extraction techniques vary greatly. No significant relationship was found for total soil N, the most commonly measured soil N pool, and the inverse of litterfall N concentrations. The results suggest that our indices of soil P are related to litterfall processes, but that other measures, particularly total soil N, may not be as relevant to nutrient cycling by the vegetation.     

Litter production, leaf litter decomposition and nutrient return in Cunninghamia lanceolata plantations in south China: effect of planting conifers with broadleaved species

This study compared litter production, litter decomposition and nutrient return in pure and mixed species plantations. Dry weight and N, P, K, Ca, Mg quantities in the litterfall were measured in one pure Cunninghamia lanceolata plantation (PC) and two mixed-species plantations of C. lanceolata with Alnus cremastogyne (MCA) and Kalopanax septemlobus (MCK) in subtropical China. Covering 6 years of observations, mean annual litter production of MCA (4.97 Mg·ha⁻¹) and MCK (3.97 Mg·ha⁻¹) was significantly higher than that of PC (3.46 Mg·ha⁻¹). Broadleaved trees contributed 42% of the total litter production in MCA and 31% in MCK. Introduction of broadleaved tree species had no significant effect on litterfall pattern. Total litterfall was greatest in the dry season from November to March. Nutrient returns to the forest floor through leaf litter were significantly higher in both MCA and MCK than in PC (P < 0.05). The amounts of N, K, and Mg returned to the forest floor through leaf litter were highest in the MCA, and P and Ca returns were highest in the MCK. Percent contribution of broadleaf litter to total nutrient returns ranged from 41.7% to 86.9% in MCA and from 49.3% to 74.8% in MCK. The decomposition rate of individual leaf litter increased in the order: C. lanceolata < K. septemlobus < A. cremastogyne. Litter mixing had a positive effect on decomposition rate of the more recalcitrant litter and promoted nutrient return. Relative to mass loss of A. cremastogyne decomposing alone, higher mass loss of the mixture of C. lanceolata and A. cremastogyne was observed after 330 days of decomposition. These results indicate that mixed plantations of different tree species have advantages over monospecific plantations with regards to nutrient fluxes and these advantages have relevance to restoration of degraded sites. Responsible Editor: Alfonso Escudero.     

Litter production,nutrient recycling and litter accumulation inPinus caribaea Morelet var.hondurensis stands in the northern Guniea savanna of Nigeria

Summary The seasonal pattern and quantity of litterfall were studied during a two-year period in two unthinned stands ofPinus caribaea Morelet var. hondurensis Barr. and Golf. in Nigeria. Although pine needles were cast continuously throughout the year, the peak period of litterfall occurred in the dry months of March and April. Mean values of annual litterfall were 3068 and 3665 kg/ha in the two stands aged 7–9 and 9–11 years respectively. Nutrient returns in litterfall in the stands had mean values of 15.0, 0.6, 17.3, 18.2 and 6.3 kg/ha of N, P, K, Ca and Mg respectively. Comparatively low amounts of N and P returned in litterfall were attributed to soil deficiencies of the two elements.Measurements of ground litter showed considerable dry matter accumulation (11378 kg/ha) in the litter layers. Estimates of litter decomposition rate and recycling time showed that it would take 3 to 4 years for the organic matter in annual litterfall to decompose completely as contrasted to about 2 to 5 months often reported under mixed nautral savanna vegetation in the same climatic environment. Similar estimates of nutrient recycling time also showed that between 2 to 4 years were required to mineralize nutrient elements in the annual litterfall; the relative mobilities of the elements were in the order K>Mg>P>NCa.     

黑石顶自然保护区南亚热带常绿阔叶林生物量与生产量研究VII.凋落量、现存凋落量和凋落物分解速率

本文研究了黑石顶自然保护区南亚热带常绿阔叶林的凋落量及其季节动态,并对现存凋落量和凋落物分解速率进行了初步测定。 小凋落物[叶、D(直径)