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Aboveground litter production is an important biogeochemical pathway in forests whereby carbon and nutrients enter soil detrital pools. However, patterns and controls of aboveground litter production are often based on an understanding of how autumnal, foliar inputs are related to aboveground tree production. Here we use three separate data sources of aboveground litter production in temperate forests to ask how aboveground woody productivity affects foliar litter production in light of other factors, such as the climate sensitivity of litter production and the seasonality of not only foliar but also fine woody debris and reproductive litter inputs. We find that foliar litter production increases with aboveground woody production, and this relationship is modified both by plant functional group and climate. Basal area also provides a crucial control on litter production. Conifer forests produce approximately half as much foliar litter as broadleaf deciduous forests. Litter production is sensitive to both amongsite and among-year variation in climate, such that more litter is produced in warmer, wetter locations and years. On average 72% of aboveground litter is foliar material, with the remaining split about evenly between fine woody debris and reproductive material, and although about 88% of broadleaf litter falls during autumn, only about 61% of needles, 37% of fine woody debris and 43% of reproductive material falls during the same period. Together these results illustrate key differences in the controls of litter production in coniferous and deciduous forests, and highlight the importance of often overlooked litter fluxes, including non-autumn and non-foliar litterfall.

Aims Mangrove above- and belowground litter contributes greatly to soil carbon (C) especially in systems with limited allochthonous input. This study aims to estimate the relative contributions of mangrove leaf litter vs. fine roots to the annually accumulated plant debris in the soil. Methods Annual production of leaf litter and fine roots in four mono-specific mangrove forests was combined with their mass remaining after one year of decomposition to make the estimation. Results Annual fine root production was 2.2–5.1 times greater than leaf litter production, which ranged between 266 and 814 g m−2. After 391 days of decomposition, 0–41% and 75–88% of leaf Utter and fine root initial mass respectively remained. Only 5.9–69 months were expected for leaf litter to reach an approximately complete decomposition, in contrast to 111–655 months expected for fine roots. Annual plant detritus accumulation in the soil amounted to 405–2812 g m−2, with leaf litter and fine roots contributing 2.5–7.6% and 92.4–97.5%, respectively. Conclusions Fine roots are the dominant contributor to soil organic matter accumulation in mangroves due to high production and low decomposition rates. Management practices that foster fine root production are expected to accelerate soil C accumulation.

I present a meta-analysis of plant responses to 48 nutrient addition experiments conducted with native species in naturally growing tropical forests, exclusive of mangrove forests. The added nutrients include nitrogen (N) in 36 experiments, phosphorus (P) in 33 experiments, calcium and potassium in one experiment each, and various mixtures of essential nutrients in the remaining experiments. I evaluate the hypotheses that nutrients limit tropical forest plants, nutrient limitation is stronger in successional than in old-growth forests, P but not N is limiting in lowland forests, and N is limiting in montane forests. Responses to the most complete nutrient mix used in each experiment were strong for plant functions that contribute to aboveground production (Hedges' g averages 0.87) and nonsignificant for fine root biomass. Responses to N addition and to P addition were strong for tissue concentrations of the added element (Hedges' g averages 0.75 and 1.4, respectively), moderate for fine litter production (0.64 and 0.65, respectively), moderate to weak for plant growth (0.46 and 0.37, respectively) and nonsignificant for fine root biomass. Growth responses were stronger in successional than in old-growth forests. All responses were unrelated to elevation. The 48 experiments included 30 factorial nitrogen-phosphorus experiments that enable additional direct tests of the widely cited hypotheses that P limitation is stronger than N limitation in lowland forests and vice versa in montane forests. Both hypotheses were rejected. The N × P interaction effect was nonsignificant across the factorial experiments. In conclusion, nutrients clearly limit tropical forest plants. Limitation by N is widespread in both lowland and montane forests, and the same is true for P. Single experiments identify limitation by calcium and potassium, and correlative studies suggest limitation by calcium, potassium, and magnesium. The available evidence is consistent with the possibility that most macronutrients limit tropical forest plants; however, experiments focus almost exclusively on N and P. The way forward will include taking fuller advantage of existing nutrient addition experiments, siting new experiments strategically, and developing cost-effective methods to assay responses to all of the essential nutrients soils supply to plants.

We present a meta-analysis of plant responses to fertilization experiments conducted in lowland, species-rich, tropical forests. We also update a key result and present the first species-level analyses of tree growth rates for a 15-yr factorial nitrogen (N), phosphorus (P), and potassium (K) experiment conducted in central Panama. The update concerns community-level tree growth rates, which responded significantly to the addition of N and K together after 10 yr of fertilization but not after 15 yr. Our experimental soils are infertile for the region, and species whose regional distributions are strongly associated with low soil P availability dominate the local tree flora. Under these circumstances, we expect muted responses to fertilization, and we predicted species associated with low-P soils would respond most slowly. The data did not support this prediction, species-level tree growth responses to P addition were unrelated to species-level soil P associations. The meta-analysis demonstrated that nutrient limitation is widespread in lowland tropical forests and evaluated two directional hypotheses concerning plant responses to N addition and to P addition. The meta-analysis supported the hypothesis that tree (or biomass) growth rate responses to fertilization are weaker in old growth forests and stronger in secondary forests, where rapid biomass accumulation provides a nutrient sink. The meta-analysis found no support for the long-standing hypothesis that plant responses are stronger for P addition and weaker for N addition. We do not advocate discarding the latter hypothesis. There are only 14 fertilization experiments from lowland, species-rich, tropical forests, 13 of the 14 experiments added nutrients for five or fewer years, and responses vary widely among experiments. Potential fertilization responses should be muted when the species present are well adapted to nutrient-poor soils, as is the case in our experiment, and when pest pressure increases with fertilization, as it does in our experiment. The statistical power and especially the duration of fertilization experiments conducted in old growth, tropical forests might be insufficient to detect the slow, modest growth responses that are to be expected.

Nutrient addition experiments indicate that nitrogen and phosphorus limit plant processes in many tropical forests. However, the long-term consequences for forest structure and species composition remain unexplored. We are positioned to evaluate potential long-term consequences of nutrient addition in central Panama where we have maintained a factorial nitrogen–phosphorus–potassium fertilization experiment for 21 yr and an independent study quantified the species-specific nutrient requirements of 550 local tree species. Here, we ask whether nutrients limit reproduction at the species and community levels. We also ask whether species-specific reproductive responses to nutrient addition are stronger among species associated with naturally fertile soils, which could contribute to a shift in species composition. We quantified species-level reproductive responses for 38 focal species in the 21st year of the experiment and community-level reproductive litter production for the first 20 yr. Species-level reproductive responses to nitrogen and potassium addition were weak, inconsistent across species, and insignificant across the 38 focal species. In contrast, species-level responses to phosphorus addition were consistently and significantly positive across the 38 focal species but were unrelated to species-specific phosphorus requirements documented independently for the same species. Community-level reproductive litter production was unaffected by nutrient addition, possibly because spatial and temporal variation is large. We conclude that phosphorus limits reproduction by trees in our experiment but find no evidence that reproductive responses to phosphorus addition favor species associated with naturally phosphorus-rich soils.

This study elucidates the litter dynamics including decomposition rate both in-situ and ex-situ, the initial acquisition traits (LATs), morphological traits (LMTs) and production rate of leaf litter of four economically important tree species viz. Terminalia arjuna (TA), Tectona grandis (TG), Eucalyptus citriodora (EC) and Psidium guajava (PG) with the major objective of restoration of degraded urban ecosystems in dry tropics. Annual litterfall production rates were observed as: TG > TA > EC > PG. LMTs, that is, specific leaf area followed the trend: TG > TA > PG > EC, whereas leaf mass per area followed the reverse trend. In TA, LATs involving carbon (C), nitrogen (N) and cellulose were highest but C/N and lignin/N ratios were lowest, whereas lignin, polyphenol, C/N and lignin/N ratios were highest in PG. In the leaf litter bag experiment, the decomposition rate followed the trend: TA > TG > EC > PG. In-situ and ex-situ rates of decomposition of all the four leaf litters were found to be similar. LATs especially lignin/N, N and C/N ratios rather than LMTs were found to be a better predictor of the litter decomposition rate. TA plantation having a higher litter decomposition rate, may be recommended for inclusion in the restoration strategies of degraded urban land.

Aim The objective of this research was to investigate the spatio-temporal variations in sedimentary nutrient levels and establish correlations with various hydro-geomorphic and ecological parameters, including the magnitude of tidal-inundation, distance from the river and sea-front, and litter production by different mangrove species within the study area. Methods Twelve transects were selected, each with atleast four sampling points spaced at intervals averaging 100 m, considering various hydro-geomorphic attributes for seasonal sediment sample collection. Eight major soil parameters were measured, including the nutrient parameters TN, TP, TK, OC, OM, NO 3 – and PO 4 3– , as well as CaCO 3 . Mangrove litter collections were conducted using litter traps. Results The total-nitrogen (TN) exhibited distinct patterns: the lowest annual mean was 152.24 ± 7.05 kg/ha in the lower zone, peaking at 209.7 ± 11.8 kg/ha in the middle zone, and decreasing in the upper zone with increasing distance from the sea. Along the ‘mangrove dominated intertidal mudflat’ gradient, TN was lower near the riverfront and higher in the forest interior. Seasonally, TN was highest in postmonsoon and lowest during the monsoon. Other parameters showed similar patterns with varying magnitudes. Litter production varied among species, with Excoecaria agallocha showed highest rate at 41.60 ± 9.58 g/m 2 /month, followed by Bruguiera gymnorrhiza and Avicennia alba . Litter production was highest in postmonsoon, declining towards the monsoon. ANOVA results revealed intricate relationships between seasons, transects, and the eight dependent variables. Conclusion The analysis underscored the pronounced spatio-temporal variability in nutrient levels, influenced by a range of hydro-geomorphic factors, and highlights a good correlation with litter productivity of the region.

Shrub encroachment into grasslands is ubiquitous but its impact on soil organic C (SOC) remains unclear. In previous work we had observed that shrub encroachment into mesic mountain grasslands increased SOC content. Here we sought the mechanisms of this increase. To this end, we assessed aboveground and belowground production for a conifer shrub (Juniperus communis L), a legume shmb (Cytisus balansae ssp. europaeus (G. López & Jarvis) Muñoz Garmendia) and grass (Festuca eskia Ramond ex DC), together with decomposition rates for both aboveground litter and roots. Belowground C net inputs do not clearly explain SOC increase: grass root production was higher than that of either shrub and the decomposition rate of grass roots was the lowest. Aboveground C net inputs were only slightly greater in shrubs than in grass, but the decomposition rate of litter of both shrubs was much lower than that of grass. The decomposition of conifer litter was N-limited, whereas that of legume shrub litter was P-limited. Thus we conclude that the SOC increases after shrub encroachment into mesic grasslands probably as a result of higher recalcitrance of shrub aboveground litter relative to grass litter.

Background and aims Increased soil temperature and nutrient availability enhance soil biological activity. We studied how these affect fine root growth and survival, i.e. below-ground litter production, in relation to above-ground foliage litter production of Norway spruce (Picea abies (L.) Karst.). Methods The treatments, irrigation (I), soil warming + irrigation (WI), fertilization + irrigation (FI) and soil warming + fertilization + irrigation (WFI) were started in 1987 (F, I) and in 1995 (W). The annual production of fine root litter was estimated from minirhizotrons (survival) and soil-cores (biomass) and the annual above-ground litter production from litter traps. Results and conclusions The number and elongation of fine roots tended to be higher in WI and I compared to the other treatments, which may indicate nutrient shortage. Fine roots in the WFI treatment had the lowest median longevity and from three to fourfold higher below-ground litter production compared to WI, FI or I - higher soil temperature increased the litter input particularly into the mineral soil. Only fertilization increased the above-ground litter production. As warmer and more nutrient-rich soil significantly shortened the fine root lifespan and increased the litter input, the storage of carbon in boreal forest soil may increase in the future.

Mangroves and coastal afforestation are important biodiversity conservation, shoreline stabilization, and carbon sequestration, essential components of climate change mitigation. However, limited studies have estimated the net primary productivity (NPP) of mangrove plantations across age classes, especially in Bangladesh, where afforestation plays a crucial role in climate resilience. This study evaluates the NPP and carbon sequestration rate for young (20 years) and mature (40 + years) mangrove stands along the Bishkhali River in Barguna district, central coastal Bangladesh. Above- and below-ground biomass increments were estimated using periodic tree measurements, allometric equations, and the root biomass from soil pit method. At the same time, litter production was measured using traps over three years. NPP was calculated by summing annual above- and below-ground biomass increments and litter production, then converted to carbon sequestration rate. Young stand exhibited significantly higher basal area increment (3.06 m 2 /ha/yr) and above-ground biomass accumulation (17.58 ± 0.72 t/ha/yr) than mature stand. Peak litter production occurred from September to November, ranging from 1.78 to 1.88 t/ha in the young stand and 2.27 to 2.32 t/ha for the mature stand. However, total annual litter production (12.27 ± 0.92 t/ha/yr in young stand vs. 15.94 ± 1.2 t/ha/yr in mature stand) showed no significant (p > 0.05) difference. NPP and carbon sequestration rates ranged from 39.67 ± 0.49 to 37.64 ± 0.57 t/ha/year and from 18.64 ± 0.23 to 17.69 ± 0.27 t/ha/year, respectively, showing significant (p(T ≥  = t) two-tail) differences between young and mature stands. These findings address important knowledge gaps in age-specific productivity and provide insights for optimizing mangrove-based climate adaptation strategies.