Litter fall and decomposition in a Pinus halepensis forest on Mallorca

Abstract. Litter fall and decomposition in a Pinus halepensis forest was studied in order to help understand nutrient cycles in this ecosystem, threatened as it is by fire and tourism. The study was done over two years in an experimental forest stand at Cap des Pinar on Mallorca, Spain. The woodland area has not been disturbed for about 40 yr. Total litter fall amounted to 3.44 ton ha^-1 yr^-1 and 2.52 ton ha^-1 yr^-1 in the first and second year, and leaf fall to 2.00 ton ha^-1 yr^-1 and 1.93 ton ha^-1 yr^-1 respectively with a maximum in July. As to litter fall, there was a summer maximum for brown needles and kernels, a spring maximum for inflorescences and bud scales, and an autumn maximum for bark. Erratic maxima occurred for fall of green needles, cones and branches, linked to strong winds in winter. The total amount of litter mass on the forest soil reached 12.68 ton/ha: 5.75 ton/ha in the L organic horizon, 3.46 ton/ha needles, and 6.93 ton/ha in the F organic horizon. Weight loss from annual decomposition, measured using litter bags, was 18.1 % in year 1 and 26.8% in year 2. Over 365 days, an Olson (1963) decomposition rate of 0.045 %/day was found in year 1 and of 0.084 %/day for year 2. Decomposition half-time was 1529 for year 1 and 827 days for year 2.     

Lignin properties in topsoils of a beech/oak forest after 8 years of manipulated litter fall: relevance of altered input and oxidation of lignin

Background and aims

We studied the response of lignin oxidation in soils of a beech/oak forest to changes in litter fall. Additionally we considered possible factors in lignin oxidation, including altered (i) input of fresh organic matter and (ii) fungi-to-bacteria ratios.

Methods

The field-based experiment included (i) doubling and (ii) exclusion of litter fall and (iii) controls with ambient litter fall. Soil (0–20 cm depth) was sampled after 8 years. We analyzed (i) lignin using the CuO oxidation method, (ii) stocks of free and mineral-bound organic carbon (OC), (iii) the response of soil organic matter (SOM) decomposition to addition of labile organic compounds in laboratory incubations, and (iv) ratios of fungal- vs. bacterial-derived amino sugars (F/B ratios).

Results

Litter exclusion increased stocks of free-light fraction OC, F/B ratios, the ability of the microbial community to use labile compounds for SOM decomposition, as well as acid-to-aldehyde ratios of vanillyl-type lignin phenols in A horizons. Litter addition had no such effects. We assume that litter exclusion caused enhanced transport of organic debris from lower forest floor horizons with rainwater into the A horizon. Enhanced input of organic debris might have increased (i) the availability of labile compounds and (ii) F/B ratios. Consequently, lignin oxidation increased.

Conclusions

Enhanced input of organic debris from forest floors can increase lignin oxidation in mineral topsoils of the studied forest. The expected gradual changes in litter fall due to climate change likely will cause no such effects.     

Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia

Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5 Mg ha/y) and in pine (7.8 Mg ha/y), but very low in cypress (3.5 Mg ha/y). Litter standing was 1.76, 1.73 and 1.3 Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115 kg/ha), followed by oak (78 kg/ha) and cypress (24 kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains.     

Experimental shading alters leaf litter breakdown in streams of contrasting riparian canopy cover

1. Headwater stream ecosystems are primarily heterotrophic, with allochthonous organic matter being the dominant energy. However, sunlight indirectly influences ecosystem structure and functioning, affecting microbial and invertebrate consumers and, ultimately, leaf litter breakdown. We tested the effects of artificial shading on litter breakdown rates in an open‐canopy stream (high ambient light) and a closed‐canopy stream (low ambient light). We further examined the responses of invertebrate shredders and aquatic hyphomycetes to shading to disentangle the underlying effects of light availability on litter breakdown. 2. Litter breakdown was substantially slower for both fast‐decomposing (alder, Alnus glutinosa) and slow‐decomposing (beech, Fagus sylvatica) leaf litters in artificially shaded stream reaches relative to control (no artificial shading) reaches, regardless of stream type (open or closed canopy). 3. Shredder densities were higher on A. glutinosa than on F. sylvatica litter, and shading had a greater effect on reducing shredder densities associated with A. glutinosa than those associated with F. sylvatica litter in both stream types. Fungal biomass was also negatively affected by shading. Results suggest that the effects of light availability on litter breakdown rates are mediated by resource quality and consumer density. 4. Results from feeding experiments, where A. glutinosa litter incubated under ambient light or artificial shade was offered to the shredder Gammarus fossarum, suggest that experimental shading and riparian canopy openness influenced litter palatability interactively. Rates of litter consumption by G. fossarum were decreased by experimental shading in the open‐canopy stream only. 5. The results suggest that even small variations in light availability in streams can mediate substantial within‐stream heterogeneity in litter breakdown. This study provides further evidence that changes in riparian vegetation, and thus light availability, influence organic matter processing in heterotrophic stream ecosystems through multiple trophic levels.     

Accounting for tree spatial distribution in a comparison of plot sizes and shapes in dense forest and woodland in Benin (West Africa)

The study examined simultaneously, the effect of tree spatial distribution, inventory plot size and shape on the estimation error of basal area in two contrasting environments. Twenty and fifteen square plots of 1 ha each (divided into 100 quadrats of 0.01 ha) were randomly set in dense forest and woodland, respectively. Thirteen subplots of various shapes and sizes were obtained from the association of adjacent quadrats. Estimation error was calculated using residual mean square of one‐way ANOVA, based on replications of subplot within 1 ha plots. Tree spatial distribution was measured using Green index. Weighted linear regression and mixed effect models were applied to Box & Cox transformed data. In general, the estimation error of basal area decreased with increase in subplot size. However, the effects of tree spatial distribution and plot shape varied with the vegetation type. Where trees tended to be aggregated, estimation error increased with degree of aggregation, and rectangular plots of 0.24 ha produced an acceptable precision. It was concluded that 0.24 ha rectangular plots can be used in tropical environments where the target parameters vary constantly according to one direction, while square plots of the same size are optimal for reliable analysis in case of randomness.     

Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface‐incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open‐top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures.     

Response of dissolved organic matter in the forest floor to long-term manipulation of litter and throughfall inputs

Dissolved organic matter (DOM) contributes to organic carbon either stored in mineral soil horizons or exported to the hydrosphere. However, the main controls of DOM dynamics are still under debate. We studied fresh leaf litter and more decomposed organic material as the main sources of DOM exported from the forest floor of a mixed beech/oak forest in Germany. In the field we doubled and excluded aboveground litter input and doubled the input of throughfall. From 1999 to 2005 we measured concentrations and fluxes of dissolved organic C and N (DOC, DON) beneath the Oi and Oe/Oa horizon. DOM composition was traced by UV and fluorescence spectroscopy. In selected DOM samples we analyzed the concentrations of phenols, pentoses and hexoses, and lignin-derived phenols by CuO oxidation. DOC and DON concentrations and fluxes almost doubled instantaneously in both horizons of the forest floor by doubling the litter input and DOC concentrations averaged 82 mg C l⁻¹ in the Oe/Oa horizon. Properties of DOM did not suggest a change of the main DOM source towards fresh litter. In turn, increasing ratios of hexoses to pentoses and a larger content of lignin-derived phenols in the Oe/Oa horizon of the Double litter plots in comparison to the Control plots indicated a priming effect: Addition of fresh litter stimulated microbial activity resulting in increased microbial production of DOM from organic material already stored in Oe/Oa horizons. Exclusion of litter input resulted in an immediate decrease in DOC concentrations and fluxes in the thin Oi horizon. In the Oe/Oa horizon DOC concentrations started to decline in the third year and were significantly smaller than those in the Control after 5 years. Properties of DOM indicated an increased proportion of microbially and throughfall derived compounds after exclusion of litter inputs. Dissolved organic N did not decrease upon litter exclusion. We assume a microbial transformation of mineral N from throughfall and N mineralization to DON. Increased amounts of throughfall resulted in almost equivalently increased DOC fluxes in the Oe/Oa horizon. However, long-term additional throughfall inputs resulted in significantly declining DOC concentrations over time. We conclude that DOM leaving the forest floor derives mainly from decomposed organic material stored in Oe/Oa horizons. Leaching of organic matter from fresh litter is of less importance. Observed effects of litter manipulations strongly depend on time and the stocks of organic matter in forest floor horizons. Long-term experiments are particularly necessary in soils/horizons with large stocks of organic matter and in studies focusing on effects of declined substrate availability. The expected increased primary production upon climate change with subsequently enhanced litter input may result in an increased production of DOM from organic soil horizons.     

Litter type control on soil C and N stabilization dynamics in a temperate forest

While plant litters are the main source of soil organic matter (SOM) in forests, the controllers and pathways to stable SOM formation remain unclear. Here, we address how litter type (¹³C/¹⁵N‐labeled needles vs. fine roots) and placement‐depth (O vs. A horizon) affect in situ C and N dynamics in a temperate forest soil after 5 years. Litter type rather than placement‐depth controlled soil C and N retention after 5 years in situ, with belowground fine root inputs greatly enhancing soil C (x1.4) and N (x1.2) retention compared with aboveground needles. While the proportions of added needle and fine root‐derived C and N recovered into stable SOM fractions were similar, they followed different transformation pathways into stable SOM fractions: fine root transfer was slower than for needles, but proportionally more of the remaining needle‐derived C and N was transferred into stable SOM fractions. The stoichiometry of litter‐derived C vs. N within individual SOM fractions revealed the presence at least two pools of different turnover times (per SOM fraction) and emphasized the role of N‐rich compounds for long‐term persistence. Finally, a regression approach suggested that models may underestimate soil C retention from litter with fast decomposition rates.     

The effect of plant litter on ecosystem properties in a Mediterranean semi‐arid shrubland

Abstract. We studied the distribution of litter in a shrubland of the Negev with a semi‐arid Mediterranean climate of less than 200 mm of rainfall per year. Our focus was on the effects of litter on properties of landscape patches relevant to ecosystem processes (water runoff and soil erosion), annual plant community responses (seedling density, biomass production and species richness), and animal activity (soil disturbance by termites). Three 60‐m transects, extending across a pair of opposing north‐ and south‐facing slopes and their drainage channel, showed that litter accumulates not only under shrubs, but to a lesser extent also on the crusted inter‐shrub open areas. We used 35 experimental units (‘cells’, 0.5m × 1 m), each containing a crust and a shrub patch. Because runoff flows from crusted patches and is intercepted by shrub patches, the latter were in the lower third of the cells. Leaf litter was added in single and double amounts providing ca. 0.5 and 1.0 cm litter depth, to either, both, or none of the patches. Litter addition significantly decreased the amount of runoff, regardless of the location and amount of litter applied. Litter on the crust increased species number and seedling density of species with low abundance. Adding a double litter layer increased annual plant biomass production, while a single amount had no effect. Litter addition to the shrub patch affected neither biomass nor species richness. Litter addition to both patches at both quantities caused a large increase in termite activity. Termites caused disturbance by disrupting the crust, which may contribute to the reduction in runoff amounts. In the open, flat crust patches, annual plant communities are limited in their productivity and species richness, as there are few structures stopping the outflow of water, soil and seeds. Litter adds such structures, but affects the plant communities only when added to litter‐free crust. Litter accumulation and its patchy distribution have large impacts on landscape patch properties affecting resource distribution, plant productivity and diversity, and animal activity. Therefore, understanding litter distribution in relation to the patchy structure of the landscape of semi‐arid shrubland should be viewed as an important component of shrubland management.     

Identification and differential expression of microRNAs in the ovaries of pigs (Sus scrofa) with high and low litter sizes

Litter size affects profitability in the swine industry. Mammalian ovaries play important roles during reproduction, including ovulation and hormone secretion, which are tightly regulated by specific microRNAs (miRNAs). In this study, we investigated the effects of specific miRNAs on porcine litter size. We compared the ovarian miRNAs of Yorkshire pigs with high (YH) and low (YL) litter sizes using Solexa sequencing technology. We identified 327 and 320 miRNAs in the ovaries of YH and YL pigs respectively. A total of 297 miRNAs were co‐expressed; 30 and 23 miRNAs respectively were specifically expressed in the two libraries. A total of 83 novel miRNAs were predicted; 37 specific miRNAs were obtained, of which 21 miRNAs were upregulated and 16 miRNAs were downregulated in YH compared with YL. Additionally, 19 628 and 19 250 target genes were predicted in the two libraries respectively. The results revealed that specific miRNAs (i.e., miR‐224, miR‐99a, let‐7c, miR‐181c, miR‐214 and miR‐21) may affect porcine litter size. The results of this study will help in gaining understanding of the role of miRNAs in porcine litter size regulation.     

Dual,differential isotope labeling shows the preferential movement of labile plant constituents into mineral‐bonded soil organic matter

The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral‐bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual ¹³C and ¹⁵N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched ¹³C and ¹⁵N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance ¹³C–CO₂ and ¹⁵N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in ¹³C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO₂ measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral‐associated organic matter.     

Effect of available P and phenolics on mineral N release in acidified spruce forest: connection with lignin-degrading enzymes and bacterial and fungal communities

We conducted over four months a short-term laboratory incubation experiment to find the best prediction parameters (i.e. initial chemical characteristics) to explain differences in microbial respiration rates and mineral N (DIN) release in different litter in an acidified spruce forest. In addition, we wanted to find the link between the activity of key extracellular ligninolytic enzymes, phenoloxidases (PhOx) and peroxidases (Perox), microbial respiration and composition of fungal and bacterial communities. Samples of spruce needles (Picea abies) and litter of four dominant understorey vegetation; lady fern (Athyrium alpestre), blueberry (Vaccinium myrtillus), reedgrass (Calamagrostis villosa) and hair grass (Avenella flexuosa), were collected in 2005, 2006 and 2007 from six sites located in watersheds of two glacial lakes (Plesne Lake and Certovo Lake) in the Bohemian Forest, Czech Republic. Litter samples were incubated at 0 and 10 °C in laboratory controlled conditions for 90 days. Activities of PhOx and PerOx, and C mineralization rate were measured regularly each 14 days. Litter quality characteristics and endophytic microbial community structure, based on 16SrDNA-DGGE fingerprint of bacteria and ITS-DGGE of fungi, were determined at the beginning and end of litter incubation. Our results showed a close correlation of phenolics/P_OX with DIN release (r > 0.74, p < 0.001). Using multivariate analyses, P_OX seems to play an important role in the change of litter fungal and bacterial community composition. At 0 °C the fungal and bacterial communities of reedgrass and blueberry litter changed in relation to P_OX and Perox activity, while at 10 °C the fungal communities after the incubation were additionally affected by the phenolics/N_TOT and phenolics/P_TOT ratios.     

Microbial Colonization of Beech and Spruce Litter—Influence of Decomposition Site and Plant Litter Species on the Diversity of Microbial Community

The present study was conducted to investigate the effect of decomposition site and plant litter species on the colonizing microbial communities. For this, litter bag technique using beech and spruce litter was combined with RNA-based fingerprinting and cloning. Litter bags were incubated for 2 and 8 weeks in the A_h horizon of beech and beech–spruce mixed forest sites. Although sugars and starch were rapidly lost, lignin content increased by more than 40% for beech and more than doubled for spruce litter at both soil sites at the end of the experiment. Denaturing gradient gel electrophoresis analysis of 16S and 18S rRNA RT–PCR products was used for screening of differences between bacterial and fungal communities colonizing the two litter types. Development of the microbial community over time was observed to be specific for each litter type and decomposition site. RT–PCR products from both litter types incubated in beech–spruce mixed forest site were also cloned to identify the bacterial and fungal colonizers. The 16S rRNA clone libraries of beech litter were dominated by γ-proteobacterial members, whereas spruce libraries were mainly composed of α-, β-, and γ-proteobacterial members. Ascomycota members dominated the 18S rRNA clone libraries. Clones similar to Zygomycota were absent from spruce, whereas those similar to Basidiomycota and Glomeromycota were absent from beech libraries. Selective effects of litter quality were observed after 8 weeks. The study provides an insight into the bacterial and fungal communities colonizing beech and spruce litter, and the importance of litter quality and decomposition site as key factors in their development and succession.     

利用辅助变量对污染土壤锌分布的克里格估值

采用协同克里格及与回归相结合的克里格方法,以36个下层(10～20 cm)土壤锌数据为目标变量、另36个下层土壤锌数据为校验数据、72个上层(0～10 cm)土壤锌为辅助变量,对沈阳市南郊某有色金属加工厂附近农田0.1 mol·L^-1 HCl浸提态土壤锌进行插值分析,并对这两种利用辅助变量的克里格方法在土壤锌空间分布研究中的适用性进行评价.结果表明,与回归相结合的克里格的估值效果明显优于协同克里格及普通克里格法.结合回归模型的变异函数理论模型决定系数较大、残差较小,估值精度比普通克里格法提高4%,且基于回归克里格的土壤锌分布图与利用72个样点普通克里格插值图具有高度的相似性.而协同克里格与普通克里格相比未表现出明显优势.借助辅助变量,采用基于回归模型的克里格方法是进行土壤重金属空间分布估值的一种有效方法.     

The influence of litter quality and micro-habitat on litter decomposition and soil properties in a silvopasture system

Studies to understand litter processes and soil properties are useful for maintaining pastureland productivity as animal husbandry is the dominant occupation in the hot arid region. We aimed to quantify how micro-habitats and combinations of litters of the introduced leguminous tree Colophospermum mopane with the grasses Cenchrus ciliaris or Lasiurus sindicus influence decomposition rate and soil nutrient changes in a hot desert silvopasture system. Litter bags with tree litter alone (T), tree + C. ciliaris in 1:1 ratio (TCC) and tree + L. sindicus 1:1 ratio (TLS) litter were placed inside and outside of the C. mopane canopy and at the surface, 3–7 cm and 8–12 cm soil depths. We examined litter loss, soil fauna abundance, organic carbon (SOC), total (TN), ammonium (NH₄–N) and nitrate (NO₃–N) nitrogen, phosphorus (PO₄–P), soil respiration (SR) and dehydrogenase activity (DHA) in soil adjacent to each litter bag. After 12 months exposure, the mean residual litter was 40.2% of the initial value and annual decomposition rate constant (k) was 0.98 (0.49–1.80). Highest (p < 0.01) litter loss was in the first four months, when faunal abundance, SR, DHA and humidity were highest but it decreased with time. These variables and k were highest under the tree canopies. The litter loss and k were highest (p < 0.01) in TLS under the tree canopy, but the reverse trend was found for litter outside the canopy. Faunal abundance, litter loss, k, nutrient release and biochemical activities were highest (p < 0.01) in the 3–7 cm soil layer. Positive correlations of litter loss and soil fauna abundance with soil nutrients, SR and DHA demonstrated the interactions of litter quality and micro-habitats together with soil fauna on increased soil fertility. These results suggest that a Colophospermum mopane and L. sindicus silvopasture system best promotes faunal abundance, litter decomposition and soil fertility. The properties of these species and the associated faunal resources may be utilised as an ecosystem-restoration strategy in designing a silvopasture system. This may help to control land degradation and increase productivity sustainably in this environment.     

Leaf litter production and decomposition in a poplar short-rotation coppice exposed to free air CO2 enrichment (POPFACE)

The capacity of forest ecosystems to sequester C in the soil relies on the net balance between litter production above, as well as, below ground, and decomposition processes. Nitrogen mineralization and its availability for plant growth and microbial activity often control the speed of both processes. Litter production, decomposition and N mineralization are strongly interdependent. Thus, their responses to global environmental changes (i.e. elevated CO₂, climate, N deposition, etc.) cannot be fully understood if they are studied in isolation. In the present experiment, we investigated litter fall, litter decomposition and N dynamics in decomposing litter of three Populus spp., in the second and third growing season of a short rotation coppice under FACE. Elevated CO₂ did not affect annual litter production but slightly retarded litter fall in the third growing season. In all species, elevated CO₂ lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations. Litter decomposition was studied in bags incubated in situ both in control and FACE plots. Litter lost between 15% and 18% of the original mass during the eight months of field incubation. On average, litter produced under elevated CO₂ attained higher residual mass than control litter. On the other end, when litter was incubated in FACE plots it exhibited higher decay rates. These responses were strongly species‐specific. All litter increased their N content during decomposition, indicating immobilization of N from external sources. Independent of the initial quality, litter incubated on FACE soils immobilized less N, possibly as a result of lower N availability in the soil. Indeed, our results refer to a short‐term decomposition experiment. However, according to a longer‐term model extrapolation of our results, we anticipate that in Mediterranean climate, under elevated atmospheric CO₂, soil organic C pool of forest ecosystems may initially display faster turnover, but soil N availability will eventually limit the process.     

Disentangling factors limiting diamondback moth,Plutella xylostella (L.), spatio‐temporal population abundance: A tool for pest forecasting

Data‐mining techniques play an important role in hyperparameter optimization of heterogeneous environmental factors and their relative contribution as determinants of incidences in insect pest ecological studies. A multidimensional field‐based surveillance was conducted in two seasons (24 months), July–June of each season (2015/2016 ‐ season 1 and 2016/2017 ‐ season 2) using sex‐pheromone‐baited traps and Thermocron i‐Buttons to identify key determinants of population abundance of diamondback moth, Plutella xylostella L., across spatial horticultural hotspots of Botswana. The moth is a notorious global brassica pest. Pearson's product moment correlation matrix showed month of the year (M), mean temperature (T_mean) and maximum temperature (T_max) as positively correlated (p < 0.001) to number of moths (N), while minimum temperature (T_min), minimum relative humidity (RH_min), mean relative humidity (RH_mean), maximum relative humidity (RH_max) and host plant (h) were negatively correlated (p < 0.001) to N. Using Waikato Environment for Knowledge Analysis (WEKA) data‐mining techniques, two models were developed: (a) M5P decision‐tree algorithm associated with nine linear models (LMs) and (b) principal component analysis (PCA) based on four principal components. Both approaches identified M as the major predictor of moth abundance, followed by h and farming region (R). However, R was a function of T_max (positive auto‐correlation) and RH_max (negative auto‐correlation). These results provide simplified relative contribution of heterogeneous factors in influencing P. xylostella spatio‐temporal abundance, essential for early warning systems in pest management. This is an important component of sustainable pest management aimed at managing insect pests and minimizing pesticides abuse in brassica production systems.     

High carbon storage and oxygen (O2) release potential of Mahagony (Swietenia macrophylla) woodlot plantation in Bangladesh

Woodlot plantation takes our attention nowadays because of having high wood value, biomass and carbon stock. It also has considerable potential for regulating climate change by sinking CO₂. This study investigated the market value of Swietenia macrophylla woodlots concerning the current carbon trade mechanism, local timber and oxygen value. The carbon-di-oxide equivalence (CO_2e) and release oxygen (O_{2 Release}) ranged from 125.5 to 1004.5 Mg/ha (mean 436.3 Mg/ha) and 91.25–730.26 Mg/ha (mean 317.2 Mg/ha), respectively. Form carbon trade, the Swietenia macrophylla woodlots owner will earn 4,285–34,470 BDT/ha (mean 14,900 BDT/ha). It also seemed that the present market value of release oxygen (O_{2 Release}) ranged from 3.2 to 25.5 million BDT/ha (average 11.1 million BDT/ha). However, the study area's average DBH, height, density, and basal area were 18.9 cm, 12.6 m, 1233 stem/ha, and 36.6 m²/ha, respectively. The above-ground biomass, below-ground biomass, and total biomass ranged from 45.9 to 389.7 Mg/ha (mean 166.5 Mg/ha), 22.5–157.7 Mg/ha (mean 71.2 Mg/ha), and 68.4–547.4 Mg/ha (mean 237.7 Mg/ha) correspondingly. Besides, the produced wood volume ranged from 64.95-1225.19 m³/ha (average 481.48 m³/ha). While the price of wood ranged from 0.8 to 15.14 million BDT/ha (mean 5.95 million BDT/ha). However, the above-ground, below-ground, and total carbon ranged 22.97–194.85 Mg/ha (mean 87.27 Mg/ha, 11.23–78.85 Mg/ha (35.61 Mg/ha), and 34.2–273.7 Mg/ha (118.89 Mg/ha) independently. Moreover, our three developed basal area-based allometric models are fit for calculating the carbon stock of Swietenia macrophylla woodlots. This study explores the potentiality of woodlots in Bangladesh. Policymakers should encourage the farmers to create more woodlots that actively participate in climate change mitigation.     

Carbon pools and fluxes in Bruguiera parviflora dominated naturally growing mangrove forest of Peninsular Malaysia

Estimation of carbon pools and fluxes were conducted in Bruguiera parviflora dominated naturally growing protected mangrove forest in Kuala Selangor Nature Park of Peninsular Malaysia. Above and below-ground carbon pools in seedlings were estimated from destructive methods. While, carbon pools and fluxes in saplings and trees were estimated from the derived allometric biomass equations. Carbon concentrations in different parts of seedlings, saplings and trees; and litter were measured during the dry, wet and intermediate seasons. Soil cores up to 1 m were analyzed to measure carbon concentrations and bulk densities at different depths. Litter standing crop of the study area was measured at the dry, wet and intermediate seasons and the range of total amount of litter standing crop was from 0.66 to 0.88 Mg/ha. Carbon concentration found to vary with the plant and litter parts; and also with the seasons and the range of mean weighted carbon concentration was 40.19 ± 0.87–56.52 ± 1.01 %. The carbon pools in seedling, sapling, tree and litter were 0.69, 0.51, 82.62 and 0.41 Mg C/ha respectively. However, 13.95 Mg C/ha/year of carbon flux was associated with saplings, trees and litter. The estimated carbon pool in the soil (up to 1 m) of the study area was 488.04 Mg C/ha. The findings of this study are the first estimation of carbon pools and fluxes in B. parviflora dominated sites and suggests the potential of this site as a carbon pool.