Nutrient transfer by leaf litterfall during a sugar maple decline episode at Lake Clair watershed,Québec,Canada

In a declining sugar maple (SM) stand, we tested the hypothesis that an increasing relative abundance of American beech (AB) and yellow birch (YB) would improve litter quality by providing a higher proportion of litterfall richer in base cations and lower in acidity. From 1989 to 2006, SM leaf fall diminished from 59% (1,718 kg ha⁻¹ year⁻¹) to 36% (915 kg ha⁻¹ year⁻¹) of the total leaf fall biomass. Overall, the increase in AB and YB litterfall compensated for the SM decrease, resulting in constant annual leaf litterfall fluxes (2,803 kg ha⁻¹ year⁻¹) over the period studied. However, because the leaf litter for AB and YB had Ca and Mg concentrations 2–3 times higher than did SM, Ca and Mg concentrations and fluxes in leaf litterfall significantly increased between 1989 and 2006. Leaf litterfall of AB and YB also has a higher base/acid ratio than SM. Consequently, changes in forest composition following SM decline led to a clear improvement in litterfall quality in terms of base cations content and fluxes and acid–base properties.     

Litterfall and nutrient return in a semi-arid southern African savanna woodland dominated by <Emphasis Type="Italic">Colophospermum mopane</Emphasis>

The objective of this study was to investigate litter production, litter standing crop and nutrient return to soil in a semi-arid southern African savanna in Bulawayo, Zimbabwe. We used a randomized block design with five blocks of 100 × 100 m demarcated in a 10-ha pocket of Colophospermum mopane-dominated open woodland protected from grazing and fire. Litter traps were installed beneath large (8.3 m crown diameter) and small mopane trees (2.7 m crown diameter) and in the intercanopy area, representing 27, 3 and 62% of the woodland area, respectively. Mean annual total litterfall over 2 years of observations was 197, 83 and 35 g m⁻² yr⁻¹ beneath large and small trees as well as in the intercanopy area, respectively. Leaf proportions of total litterfall beneath large and small trees and in the intercanopy area were 68.6, 73.0 and 75.3%, respectively. Litterfall followed a uni-modal distribution pattern and was much higher during the period of May–September (dry period) compared to other months. The total potential annual element inputs via litterfall beneath large trees were 2 and 5 times greater than beneath small trees and in the intercanopy area, respectively. Total litter standing crop was 405, 177 and 67 g m⁻² beneath large and small trees and in the intercanopy area, respectively. Concentrations of N, P and K in litterfall and surface soil were closely correlated with each other. At all sampling sites, element accession to soil through litterfall followed the decreasing sequence C > Ca > N > Mg > K > P. These results suggest that litterfall is a major process responsible for soil organic matter and nutrient enrichment beneath isolated trees in semi-arid savannas.     

Conversion of secondary broadleaved forest into Chinese fir plantation alters litter production and potential nutrient returns

Litter production, litter standing crop, and potential nutrient return via litterfall to soil were studied during a 4-year period (January 2004–December 2007) in a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation and a secondary broadleaved forest in Hunan Province in subtropical China. Mean annual litterfall in the sampling sites varied from 358 g m⁻² in the pure plantation to 669 g m⁻² in the secondary broadleaved forest. Total litterfall followed a bimodal distribution pattern for both forests. Amount of litterfall was also related to the air temperature in both forests. During the period under this study, annual variation in the total litterfall in the pure plantation was significantly higher than that in the secondary broadleaved forest. Litterfall was markedly seasonal in the both forests. Leaf proportions of litterfall in the pure plantation and secondary broadleaved forest were 58.1 and 61.7%, respectively. Total potential nutrient returns to the soil through litterfall in the pure plantation were only 46.2% of those in the secondary broadleaved forest. Total litter standing crop was 913 and 807 g m⁻² in the pure plantation and secondary broadleaved forest, respectively. Our results confirm that conversion from a secondary broadleaved forest into a pure coniferous plantation changes the functioning of the litter system.     

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.     

Spatial Variability in Litterfall,Litter Standing Crop and Litter Quality in a Tropical Rain Forest Region

Understanding the spatial variability in plant litter processes is essential for accurate comprehension of biogeochemical cycles and ecosystem function. We assessed spatial patterns in litter processes from local to regional scales, at sites throughout the wet tropical rain forests of northern Australia. We aimed to determine the controls (e.g., climate, soil, plant community composition) on annual litter standing crop, annual litterfall rate and in situ leaf litter decomposability. The level of spatial variance in these components, and leaf litter N, P, Ca, lignin, α‐cellulose and total phenolics, was determined from within the scale of subregion, to site (1 km transects) to local/plot (~30 m²). Overall, standing crop was modeled with litterfall and its chemical composition, in situ decomposability, soil Na, and topography (r² = 0.69, 36 plots). Litterfall was most closely aligned with plant species richness and stem density (negative correlation); leaf decomposability with leaf‐P and lignin, soil Na, and dry season moisture (r² = 0.89, 40 plots). The predominant scale of variability in litterfall rates was local (plot), while litter standing crop and α‐cellulose variability was more evenly distributed across spatial scales. Litter decomposability, N, P and phenolics were more aligned with subregional differences. Leaf litter C, lignin and Ca varied most at the site level, suggesting more local controls. We show that variability in litter quality and decomposability are more easily accounted for spatially than litterfall rates, which vary widely over short distances possibly in response to idiosyncratic patterns of disturbance.     

Litterfall dynamics in carbonate and deltaic mangrove ecosystems in the Gulf of Mexico

From 1996 to 2002, we measured litterfall, standing litter crop, and litter turnover rates in scrub, basin, fringe and riverine forests in two contrasting mangrove ecosystems: a carbonate-dominated system in the Southeastern Everglades and a terrigenous-dominated system in Laguna de Terminos (LT), Mexico. We hypothesized that litter dynamics is driven by latitude, geomorphology, hydrology, soil fertility and soil salinity stress. There were significant temporal patterns in LT with litterfall rates higher during the rainy season (2.4 g m⁻² day⁻¹) than during the dry season (1.8 g m⁻² day⁻¹). Total annual litterfall was significantly higher in the riverine forest (12.8 Mg ha⁻² year⁻¹) than in the fringe and basin forests (9.7 and 5.2 Mg ha⁻² year⁻¹, respectively). In Southeastern Everglades, total annual litterfall was also significantly higher during the rainy season than during the dry season. Spatially, the scrub forest had the lowest annual litterfall (2.5 Mg ha⁻² year⁻¹), while the fringe and basin had the highest (9.1 and 6.5 Mg ha⁻² year⁻¹, respectively). In LT, annual standing litter crop was 3.3 Mg ha⁻¹ in the fringe and 2.2 Mg ha⁻¹ in the basin. Litter turnover rates were significantly higher in the fringe mangrove forest (4.1 year⁻¹) relative to the basin forests (2.2 year⁻¹). At Southeastern Everglades there were significant differences in annual standing litter crop: 1.9, 3.3 and 4.5 Mg ha⁻¹ at scrub, basin and fringe mangrove sites, respectively. Furthermore, turnover rates were similar at both basin and fringe mangrove types (2.1 and 2.0 year⁻¹, respectively) but significantly higher than scrub mangrove forest (1.3 year⁻¹). These findings suggest that litter export is important in regulating litter turnover rates in frequently flooded riverine and fringe forests, while in infrequently flooded basin forests, in situ litter decomposition controls litter turnover rates.     

Impacts of the exotic,nitrogen-fixing black locust (Robinia pseudoacacia) on nitrogen-cycling in a pine–oak ecosystem

We investigated the influence of the exotic nitrogen-fixing black locust (Robinia pseudoacacia) on nitrogen cycling in a pitch pine (Pinus rigida) −scrub oak (Quercus ilicifolia, Q. prinoides) ecosystem. Within paired pine-oak and adjacent black locust stands that were the result of a 20-35 year-old invasion, we evaluated soil nutrient contents, soil nitrogen transformation rates, and annual litterfall biomass and nitrogen concentrations. In the A horizon, black locust soils had 1.3-3.2 times greater nitrogen concentration relative to soils within pine-oak stands. Black locust soils also had elevated levels of P and Ca, net nitrification rates and total net N-mineralization rates. Net nitrification rates were 25-120 times greater in black locust than in pine-oak stands. Elevated net N-mineralization rates in black locust stands were associated with an abundance of high nitrogen, low lignin leaf litter, with 86 kg N ha^–1 yr^–1 in leaf litter returned compared with 19 kg N ha^–1 yr^–1 in pine-oak stands. This difference resulted from a two-fold greater litterfall mass combined with increased litter nitrogen concentration in black locust stands (1.1% and 2.6% N for scrub oak and black locust litter, respectively). Thus, black locust supplements soil nitrogen pools, increases nitrogen return in litterfall, and enhances soil nitrogen mineralization rates when it invades nutrient poor, pine-oak ecosystems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of typhoon disturbance on fine litterfall and related nutrient input in a subtropical forest on Okinawa Island, Japan

Typhoons are frequent on Okinawa Island, southwestern Japan. The effects of typhoon disturbance on the patterns of fine litterfall and related nutrient inputs in a subtropical evergreen broad-leaved forest were studied over 5 years from May 1996 to April 2001. Annual fine litterfall averaged 7558 kg ha⁻¹ (range from 6188 to 9439 kg ha⁻¹) for six sampling plots over 5 years, which differed significantly among years (p<0.001) but not among plots (p=0.122). A seasonal maximum was most evident for leaf litter component. Woody litter fell more irregularly through the year, and peak fall varied with typhoon and windstorm. The mean ratio of annual litterfall mass of sexual organs to leaves was 0.06, much lower than that in other tropical and subtropical rain forests. Nutrient concentrations varied in litterfall components, but were not significantly different among plots. The lowest concentrations of N and P in leaf litter were observed in March, which is also the month with the greatest leaf fall. However, the highest concentrations were recorded in typhoon season. Nitrogen and P concentrations were 34% and 106% greater in the green leaves that fell during typhoons than in senescent leaves. Mean nutrient inputs by litterfall were: N 83, P 3.2, K 25, Ca 71, Mg 19, Al 12, Na 10, Fe 0.86 and Mn 3.9 kg ha⁻¹ yr⁻¹, and differed significantly among years for all elements (p<0.0005) and among plots only for K (p<0.05) and Mn (p<0.0001). Typhoon disturbance strongly affected annual fine litterfall and related nutrient inputs, which contributed an average of 30% of the annual litterfall mass, and from 30% to 39% (for different nutrient elements) of annual total nutrient inputs. The results from this study suggest that typhoon-driven maintenance of rapid cycling of P and N and their high availability in soil appears to be an important mechanism to maintain productivity in the subtropical forest on Okinawa Island.     

Litter and forest-floor dynamics in aPinus resinosa plantation in Wisconsin

Summary Breakdown of dry matter and release of nutrients from decomposing leaf litter and forest-floor material were measured in a 34-year-old red pine (Pinus resinosa Ait.) plantation in central Wisconsin using (1) leaf-litter bags (2) litterfall and forest-floor nutrient data and an exponential decay function, and (3) nutrient flux data and a mass balance equation. After one year of decomposition, 77% of the original dry matter in leaf-litter bags remained. The release of macronutrients in decomposing leaf litter was K>Mg>P, S>N>Ca, and the release of micronutrients and aluminum was Mn, B>Al>Cu>Zn. Nitrogen in decomposing leaf litter showed the leaching, accumulation, and final release phases delineated by Berg and Staff⁴. Half-lives of dry matter and nutrients in the forest floor ranged from 0.5 (K) to 39 (Al) yr. Forest-floor turnover rates of the various elements followed the same trends as in leaf-litter bags except that Ca turned over more readily than P, S, and N and Zn turned over more readily than the other micronutrients. A forest-floor nutrient balance sheet confirmed that the macronutrients N and Ca are accumulating most readily in the forest floor. The overall implications of these trends for tree nutrition are discussed.     

Invasion by a Perennial Herb Increases Decomposition Rate and Alters Nutrient Availability in Warm Temperate Lowland Forest Remnants

We determined the impact of the invasive herb, Tradescantia fluminensis Vell., on litter decomposition and nutrient availability in a remnant of New Zealand lowland podocarp–broadleaf forest. Using litter bags, we found that litter beneath mats of Tradescantia decomposed at almost twice the rate of litter placed outside the mat. Values of k (decomposition quotient) were 9.44±0.42 yrs for litter placed beneath Tradescantia and 5.42±0.42 yrs for litter placed in native, non-Tradescantia plots. The impact of Tradescantia on decomposition was evident through the smaller forest floor mass in Tradescantia plots (2.65±1.05 t ha⁻¹) compared with non-Tradescantia plots (5.05±1.05 t ha⁻¹), despite similar quantities of annual leaf litterfall into Tradescantia plots (6.85±0.85 t ha⁻¹ yr⁻¹) and non-Tradescantia plots (7.45±1.05 t ha⁻¹ yr⁻¹). Moreover, there was increased plant nitrate available, as captured on resin bags, in Tradescantia plots (25.77 ± 8.32 cmol(−)/kg resin) compared with non-Tradescantia plots (9.55±3.72 cmol(−)/kg resin). Finally, the annual nutrient uptake by Tradescantia represented a large proportion of nutrients in litterfall (41% N, 61% P, 23% Ca, 46% Mg and 83% K), exceeded the nutrient content of the forest floor (except Ca), but was a small proportion of the topsoil nutrient pools. Taken together, our results show that Tradescantia increases litter decomposition and alters nutrient availability, effects that could influence the long-term viability of the majority of podocarp–broadleaf forest remnants affected with Tradescantia in New Zealand. These impacts are likely mostly due to Tradescantia's vegetation structure (i.e., tall, dense mats) and associated microclimate, compared with native ground covers. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of a neotropical herbivore (<Emphasis Type="Italic">Lamponius portoricensis</Emphasis>) on nutrient cycling and soil processes

The role of phytophagous insects in ecosystem nutrient cycling remains poorly understood. By altering the flow of litterfall nutrients from the canopy to the forest floor, herbivores may influence key ecosystem processes. We manipulated levels of herbivory in a lower montane tropical rainforest of Puerto Rico using the common herbivore, Lamponius portoricensis (Phasmatidea), on a prevalent understory plant, Piper glabrescens (Piperaceae), and measured the effects on nutrient input to the forest floor and on rates of litter decomposition. Four treatment levels of herbivory generated a full range of leaf area removal, from plants experiencing no herbivory to plants that were completely defoliated (>4,000 cm² leaf area removed during the 76-day study duration). A significant (P<0.05) positive regression was found between all measures of herbivory (total leaf area removed, greenfall production, and frass-related inputs) and the concentration of NO ₃ ⁻ in ion exchange resin bags located in the litter layer. No significant relationship was found between any of the herbivory components and resin bag concentrations of NH ₄ ⁺ or PO ₄ ⁻ . Rates of litter decay were significantly affected by frass-related herbivore inputs. A marginally significant negative relationship was also found between the litter mass remaining at 47 days and total leaf area removed. This study demonstrated a modest, but direct relationship between herbivory and both litter decomposition and NO ₃ ⁻ transfer to the forest floor. These results suggest that insect herbivores can influence forest floor nutrient dynamics and thus merit further consideration in discussions on ecosystem nutrient dynamics.     

Litter Decomposition and Nutrient Release in a Tropical Seasonal Rain Forest of Xishuangbanna,Southwest China1

We studied litter decomposition and nutrient release in a tropical seasonal rain forest of Xishuangbanna, Southwest China. The monthly decay rates (k) of leaf litter ranged from 0.02 to 0.21/mo, and correlated with rainfall and soil moisture. Annual k values for leaf litter (1.79/yr) averaged 4.2 times of those for coarse wood (2.5–3.5 cm in diameter). The turnover coefficients of forest floor mass (annual litterfall input/mean floor mass) were: 4.11/yr for flowers and fruits, 2.07/yr for leaves, and 1.17/yr for fine wood (≤2 cm in diameter), with resident time decreasing from fine woods (0.85 yr) to leaves (0.48 yr) and to flower and fruits (0.24 yr). Nutrient residence times in the forest floor mass were ranked as: Ca (1.0 yr) > P (0.92 yr) > Mg (0.64 yr) > N (0.36 yr) > K (0.31 yr). Our data suggest that rates of litter decomposition and nutrient release in the seasonal rain forest of Xishuangbanna are slower than those in typical lowland rain forests, but similar to those in tropical semideciduous forests.     

High litterfall in old-growth and secondary upper montane forest of Costa Rica

Tropical upper montane forests usually comprise trees of small stature with a relatively low aboveground productivity. In contrast to this rule, in the Cordillera de Talamanca (Costa Rica), tall trees (>35 m in height and more than 60 cm in diameter) are characteristic for the upper montane old-growth oak forests which are growing at an altitude of almost 3,000 m close to the alpine timberline. For these exceptional forests, productivity data are not yet available. In this study, we analyzed litterfall and its components (tree leaves, litter of epiphytic vascular and non-vascular plants, mistletoes, twigs and other canopy debris) in three forest stands belonging to different successional stages and related seasonal changes in litterfall to micrometeorological variables. The studied stands were early-successional forest (10–15-year-old), mid-successional forest (40-year-old), and old-growth forest. The stands are dominated by Quercus copeyensis and are located at 2,900-m altitude. Total litterfall was highest in the mid-successional forest (1,720 g m⁻² y⁻¹), and reached 1,288 g m⁻² y⁻¹ in the old-growth forest and 934 g m⁻² y⁻¹ in the early-successional forest. Litter mass was dominated by leaves in all stages (56–84% of total litterfall). In the old-growth forest, however, twigs and small canopy debris particles (33%), epiphytes (6%), and mistletoes (5%) also contributed substantially to litter mass. Leaf litterfall showed a clear seasonal pattern with a negative correlation to monthly precipitation and highest values in the dry season (January–April). However, the strongest correlation existed with minimum air temperature (negative), probably because temperatures already dropped at the end of the rainy season, when precipitation had not yet declined and leaf shedding already increased. In contrast, litterfall of epiphyte mass, and twigs and other debris was mostly dependent on occasional strong winds. We conclude that the upper montane oak forests of the Cordillera de Talamanca are exceptional with respect to the large tree size and the relatively high productivity as indicated by litterfall. Litter mass was especially high in the mid-successional and old-growth forests, where the observed annual totals are among the highest recorded for tropical forests so far.     

Seasonal patterns of nutrient deposition in a Quercus douglasii woodland in central California

The monthly deposition of total nitrogen, phosphorus, potassium, calcium and magnesium via canopy throughfall, and various components of the litterfall was measured for 31 months under mature Quercus douglasii and in the bulk precipitation in the surrounding open grassland. Seasonal patterns of nutrient concentration in leaf litter, throughfall, and precipitation were also measured. Total annual subcanopy deposition exceeded open precipitation deposition by approximately 45–60x for nitrogen, 5–15x for phosphorus, 30–35x for potassium, 25–35x for calcium, and 5–10x for magnesium. Total annual subcanopy deposition was low in comparison to other oak woodland sites reported in the literature. Throughfall and leaf litter were the primary sources of nutrients and thus determined the seasonal peaks of nutrient deposition. The first autumn rains and leaf fall were associated with one peak in nutrient deposition, and throughfall during early spring leaf emergence was associated with a second peak in potassium, magnesium and phosphorus. Non-leaf plant litter (excluding acorns) provided approximately 15–35% of most nutrients, with twigs and bark depositing over 12% of the annual calcium flux in 1987–1988, and flower litter depositing over 8% of the annual nitrogen flux in 1986–1987. Acorns had high concentrations of phosphorus and nitrogen and during the mast season of 1987–1988 they contained a large proportion of the total subcanopy annual flux of these elements. With acorns excluded, total annual nutrient deposition was similar between years, but timing of nutrient deposition differed. Late summer leaf fall associated with drought, variation in precipitation, and variation in deposition of non-leaf parts were associated with seasonal differences in nutrient deposition between years.     

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.     

Litter fall and nutrient dynamics in a Nigerian rain forest seven years after a ground fire

Abstract. Seasonal litter fall and mineral element content (N, P, Ca, Mg, K) of regrowth forest communities at the base and on the slope of an inselberg in Ile-Ife, Nigeria, were studied 7 yr after a ground fire ravaged the forest. Litter fall (tha^?1 yr^?1) was 4.6 (total), 4.2 (leaf), 0.3 (small wood < 2.5 cm diameter) and 0.1 (reproductive parts: fruits and flowers) in the base community and 6.4 (total), 5.4 (leaf), 0.9 (small wood) and 0.1 (reproductive parts) in the slope community. There was significant monthly variation in litter fall in the two communities with lowest amount of litter recorded during the wettest months of the year (May - August) and the highest amount during the dry season. Significant monthly variation (P<0.05) in Ca, Mg and K concentration in leaf litter and for Mg (P < 0.01) in fruit litter occurred, with the lowest concentration recorded during the wettest months (May-August). In leaf and wood litter the order of mineral element concentration was Ca>N>K> Mg > P while in fruit litter it was N > K > Ca > Mg > P. Quantities of mineral element (kg ha^-1 yr¹) returned to the soil via litterfall were N: 66; P: 4; Ca: 97; Mg: 15; K: 45 in base forest, and N: 112; P: 5; Ca: 142; Mg: 20; K: 66 in slope forest. Through leaf litter >88.5% of these elements was returned into the two communities, through wood > 4.0% and through reproductive organs > 0.3%. The order of quantities of these elements returned in leaf and wood litter was Ca > N > K > Mg > P, in fruit litter N ～ K > Ca > Mg > P. Significant monthly variation in the amounts of the various elements returned were recorded in leaf litter, but not in wood and fruit litter. The lowest amount of various elements was returned during the wettest months (May-August) which coincided with the period of the lowest element concentration and litter fall.     

Nutrient return with leaf litter fall in Fagus sylvatica forests across a soil fertility gradient

Leaf litter fall is an important nutrient flux in temperature deciduous forests which supplies a large part of the rapidly mineralisable nutrient fraction to the soil. This study investigates nutrient return with leaf litter fall in 36 old-growth forest stands of Fagus sylvatica across a broad gradient of soil fertility covering 9 mesozoic and kaenozoic parent material types (three limestones, two sandstones, two clay stones, one sand and one loess substrate). Study objectives were to analyse (i) the dependency of leaf litter nutrient concentrations on soil fertility, and (ii) the relationship between soil fertility and nutrient return with leaf litter at the stand level. Beech stands on the nine parent material types produced similar annual leaf litter masses irrespective of soil fertility or acidity. Leaf litter from the nine parent materials showed only minor variation with respect to N and K concentrations (factors of 1.5 and 1.4), moderate variation for Ca, Mg and P concentrations (factors of 2.2 to 2.9), and high variation for Al and Mn concentrations (factors of 6.7 and 10.5). Consequently, annual nutrient return with litter fall (leaf litter mass x litter nutrient concentration) was more similar among the parent materials for N (165–273 mmol m⁻² yr1) ⁻¹ and K (16–30 mm m⁻² yr⁻¹) than for Ca, P, Mg, Mn and Al. A possible explanation is increased N deposition in recent time. According to a correlation analysis, return rates of N, P, K and Mg (but not Ca) were independent of the pool size of the respective nutrient in the soil. N return rate was neither influenced by the soil pools of Nt, plant- available P (Pa) or exchangeable Ca, K and Mg, nor by soil acidity or the exchangeable Al pool. P return, in contrast, showed a negative relation to soil fertility. We hypothesize that nutrient fluxes with leaf litter fall do not necessarily reduce the fitness of tree populations as has been postulated from a tree-centred view. Rather, we suggest that nutrient fluxes with litter fall can increase, instead of decrease, plant fitness by improving nutrient availability in the densely rooted topsoil which reduces the roots’ carbon and nutrient costs of nutrient acquisition.     

万木林自然保护区2种天然林及杉木人工林凋落量及养分归还

通过对福建建瓯万木林自然保护区内以观光木(Tsoongiodendron odorum,TSO)和细柄阿丁枫(Altingia gracilipes,ALG)为建群种的2种天然林及杉木(Cunninghamia lanceolata,29年生)人工林凋落量与养分归还为期3a(2000~2002年)的研究表明,3种林分年均凋落量(t.hm-2)范围从杉木人工林的4.63t.hm-2到观光木林的6.74t.hm-2,叶所占比例范围为62%~69%。细柄阿丁枫林凋落量每年只出现1次峰值(3月份或4月份),观光木林的出现2次(3月份、6~8月份),而杉木林的则出现3次(3月份或4月份、6~8月份和11~12月份)。3种林分Ca和Mg年归还量大小排序与按总凋落量的不同。除杉木人工林的Ca年归还量最大外,其余养分年归还量均以观光木天然林的最大。通过凋落物各组分的养分归还中,落叶是养分归还的主体。与针叶树人工林相比,天然林的凋落量大、养分归还量高,具有良好维持地力的能力。因此,保护和扩大常绿阔叶林资源已成为南方林区实现森林可持续经营的重要措施之一。     

鼎湖山森林凋落物量及营养元素含量研究

 本文研究了鼎湖山南亚热带常绿阔叶林和针叶林的凋落物量及凋落物中主要营养元素(N、P、K、Ca、Mg)的含量。8年的测定结果表明,两个森林类型的年均凋落物量(t·ha-1)及凋落物中主要营养元素的含量(t·ha-1·yr-1)分别为：常绿阔叶林9.056,0.220;针叶林2.695,0.032。凋落物中叶、枝和花果的百分组成及凋落特征各异。鼎湖山南亚热带常绿阔叶林的年均凋落物量低于热带雨林而高于暖温带落叶阔叶林,说明不同气候带的森林类型,其凋落物量是有差异的。与针叶林相比较,常绿阔叶林的凋落物量较大,凋落物中主要营养元素的含量较高,凋落物的分解速率也较快,因此从提高森林的质量和增强森林的生态效益来考虑,在造林绿化上应提倡多营造常绿阔叶林或针阔叶混交林。     

Loss of nutrients due to litter raking compared to the effect of acidic deposition in two spruce stands, Czech Republic

We evaluated how litter raking removed basic nutrients from forest soils by simulating this historical silvicultural practice on two spruce stands (Picea abies) in the Czech Republic. Experimental litter raking depleted the soil pool of exchangeable base cation nutrients (Ca²⁺, Mg²⁺ and K⁺) by up to 31% after the first litter raking in 2003. A second litter raking in the following year further reduced the soil pool by up to 16%, and the third litter raking in 2005 reduced the pool by up to 6% more. These losses of base cations were substantially greater than their annual input into the forest soil (estimated as from total atmospheric deposition and mineral weathering) as well as their annual runoff. The concentration of Mg and Ca in spruce needless decreased considerably within 3 years from the beginning of the experiment. In addition, the observed litter chemistry was used to estimate historical nutrient removal from litter raking by applying them to historical records of litter removal rates. According to these calculations, the annual loss of total Ca, Mg and K from spruce stands would be from 40% to 100% of its present annual input into the soil, and from 50% to 190% of annual runoff. On the basis of previous results estimated by geochemical modeling, we found that the loss of base cations due to litter raking was similar to their leaching due to acid deposition. We conclude that long-term removal of litter as widely practiced throughout the 19th century in Central Europe may have been responsible for a loss of base cations equivalent to that caused by acid deposition during the 20th century.