Adjacent Secondary Forest Research Articles

Effect of In Situ Large Soil Column Translocation on CO2 and CH4 Fluxes under Two Temperate Forests of Northeastern China

Global warming has a significant impact on soil carbon dioxide (CO2) and methane (CH4) fluxes in temperate forests. However, due to a lack of field observations, limited information is available about the responses of soil CO2 and CH4 fluxes to changes in temperature during the non-growing season and throughout the year in temperate forests. The broadleaf and Korean pine mixed mature forest (MF) and adjacent secondary white birch forest (BF) at different succession stages in the Changbai mountain region in northeastern China were selected, to study the effect of in situ soil column translocation on CO2 and CH4 fluxes in temperate forests. On average, the air temperature and soil temperature at 5 cm depth under BF stands from October 2018 to October 2022 increased by 0.64 and 0.42 °C during the non-growing season and by 0.49 and 0.43 °C throughout the year, respectively, compared with those under MF stands. Based on multi-year measurements in field experiments, it was shown that during the non-growing season, fluxes of CO2 and CH4 from soil columns under MF and BF stands ranged from 0.004 to 1.175 and from 0.015 to 1.401 (averages of 0.321 and 0.387) μmol CO2 m−2 s−1, and from −1.003 to 0.048 and from −1.037 to −0.013 (averages of −0.179 and −0.250) nmol CH4 m−2 s−1, respectively, accounting for approximately 20.8% and 25.3%, and 48.8% and 69.1% of the corresponding average fluxes during the growing season. When undisturbed soil columns of MF were transferred to a BF stand, to simulate warming, the cumulative soil CO2 emissions and CH4 uptake increased by 23.5% and 15.3% during the non-growing season, and by 9.5% and 16.3% across the year, respectively. However, when soil columns of BF were transferred to a MF stand, to simulate cooling, the cumulative soil CO2 emissions decreased by 16.9% and 0.1% during the non-growing season and across the year, respectively. Upon cooling, the cumulative soil CH4 uptake decreased by 21.8% during the non-growing season but increased by 15.4% across the year. The soil temperature and moisture at 5 cm depth in soil columns could explain 84–86% of the variability in CO2 fluxes and 16–51% of the variability in CH4 fluxes under the two forest stands throughout the field measurement period. The results of the in situ soil column translocation experiments highlight that a small climate warming in nature can increase soil CO2 emissions and CH4 uptake in the temperate forests of northeastern China, particularly during the non-growing season, which should be considered when predicting soil C fluxes in the temperate forests of northeastern China under global warming scenarios.

Native forest regeneration and eucalyptus plantations in the Malagasy Highland

AbstractEucalyptus plantations (EP) offer a number of goods and services that can reduce pressure on native forests. Eucalyptus trees can also be invasive and have a negative impact on native species diversity and regeneration. This article deals with the complex interaction between EP and native forests by studying the case of the humid forests of Malagasy Central High Land that are surrounded by EP. Floristic inventories were carried out on 400 m2 plots in adjacent secondary forests (n = 5) and EP (n = 6). Eucalyptus has not spread to secondary forests understory. Native species from secondary forests have colonised EP understory.

Impact of Useful Species Preferences on Carbon Stocks and Annual Increments in Various Cocoa-based Agroforestry Systems in Central Region of Cameroon

ABSTRACT This paper evaluates the potential effects of farmers’ species preferences on carbon stock in cocoa-based agroforestry systems (CAFS) in the Central Region of Cameroon. To achieve this goal, the species composition and structural variables of two land-use systems were investigated using 26 plots of 30 m × 30 m each, of which 20 were distributed in CAFS and 6 in adjacent secondary forests. Allometric models were used to estimate the species aboveground and root carbon stock. Ordination analysis indicated three types of species management systems: high-density timber and fruit trees; high-density Musaceae, palms and other shading trees; and low-density timber and fruit trees. The average densities of cocoa shading trees and shrubs were 234 ± 136 and 843 ± 360 individuals’ ha−1, respectively. Thus, the average potential carbon stock of the sampled CAFS was estimated at 186.97 ± 86.06 Mg C ha−1, 22% representing the root carbon stock. The transformation of secondary forest into various species management systems decreased the aboveground carbon by 18–34%. The annual rate of carbon accumulation estimated based on ring analyses was within the range 2.32–13.74 Mg C ha−1 year−1. The monetary value of the total carbon stored and the carbon accumulation rate were US$4042 ha−1and US$159 ha−1year−1, respectively.

Soil Carbon, Glomalin, And Aggregation in Onion Crop Under No-Tillage with Cover Crops or Conventional Tillage Systems for Eight Years

Crop systems using cover crops affect soil physical, chemical, and biological attributes, including aggregate formation. This work aims to evaluate winter cover crop species' effect on soil total organic carbon, glomalin, and aggregation in areas with onion crops in a no-tillage vegetable production system (NTVS) and conventional tillage system (CTS) for eight years. The experiment treatments were: control, with natural vegetation(NV); black oats (Avena strigosa); rye(Secale cereale);oilseed radish(Raphanus sativus);intercropped black oats and oilseed radish; intercropped rye and oilseed radish; and a conventional tillage systems area. A 33-year old adjacent secondary forest was evaluated as a reference for undisturbed conditions. We assessed soil total organic carbon, total glomalin, and easily extractable glomalin in three soil layers (0-5, 5-10, and 10-20 cm depth). Undisturbed samples were used to quantify soil aggregate stability, aggregation indexes (weighted mean diameter; geometric mean diameter), aggregate mass distribution (macroaggregates, mesoaggregates), and macroaggregate carbon contents. The conventional tillage areas had the lowest weighted mean soil aggregate diameter, geometric mean diameter, and macroaggregate mass. Those areas also had the lowest bulk soil and aggregate organic carbon contents and the lowest total and easily extractable glomalin. Winter cover crops' use resulted in a 10% higher aggregate weighted mean diameter and geometric mean diameter. Areas with cover crops had 13% higher organic carbon contents in aggregates and 17% higher macroaggregate mass than conventional tillage areas. The highest values of total and easily extracted glomalin occurred in plots with black oats. Winter cover crops, single or intercropped, improved physical attributes of soils with onion crops under not-tillage compared to conventional tillage areas.

Monitoring soil resilience via the dynamic changes of selected physicochemical properties of soil in a tropical rehabilitated forest

Recovery of soil organic matter and mineral nutrient cycling are critical to the success of rehabilitation process of replanted forest. We investigated the dynamic changes in soil of selected physicochemical properties including organic carbon (C), nitrogen (N), phosphorus (P) and sulphur (S) of replanted forest rehabilitation that had been previously disturbed by anthropogenic activities. Soil samples were collected from the rehabilitated forest of three ages stands (3-, 12- and 23-years old) while samples from adjacent secondary forest was collected for comparison. Altogether, 36 samples were taken randomly with a soil auger at depths of 0-20 cm from a plot of 20 × 20 m2 at each site. Soils were analyzed for pH, bulk density, C, N, P and S. The data obtained were statistically analyzed using ANOVA with Tukey’s test performed by SAS 9.2 at P ≤ 0.05. Results showed that total C, N, P, C/N ratio and C/S ratio increased with age of rehabilitated forest except for pH, S and C/P ratio. Forest rehabilitation by planting indigenous tree species has shown a potential of recovery, but further investigation into the process control of the dynamic changes of soil physicochemical properties, particularly in the event of further ecosystem disturbance is needed.

VANILLA YERSINIANA (ORCHIDACEAE), A NEW RECORD FOR PENINSULAR MALAYSIA

MAT ESA, M. I., NORDIN, F. A., GO, R. & RAFFI, A. 2021. Vanilla yersiniana (Orchidaceae), a new record for Peninsular Malaysia. Reinwardtia 20(2): 51−55. — The genus Vanilla Plum. ex Mill. from Peninsular Malaysia is now enriched with the discovery of a newly recorded species, Vanilla yersiniana that made up its regional diversity to eight taxa. This species was documented from two adjacent secondary lowland forests in Perak; further south to the southern tail of Thailand. This paper describes the first record of V. yersiniana in Peninsular Malaysia with some highlights of its morphology and ecology. The data presented will add to the present state of knowledge on the species botanical profile.

An old-growth subtropical evergreen broadleaved forest suffered more damage from Typhoon Mangkhut than an adjacent secondary forest

Typhoons are having an increasingly severe and widespread impact on forest ecosystems around the world due to climate change. However, few studies have examined the impacts of strong typhoons on subtropical evergreen broadleaved forests, particularly in rare old-growth forests. Here, using a 20 ha permanent subtropical forest plot in Guangdong Province, southern China, the impact of super Typhoon Mangkhut on secondary and old-growth subtropical evergreen broadleaved forests was quantitatively investigated and compared. The old-growth forest was damaged more than twice as much as the secondary forest, as measured by the proportion of the basal area of damaged trees. Forest structure and composition played a significant role in determining the vulnerability of forests to powerful typhoons. This study advances knowledge about how old-growth forests respond to global climate change.

Changes in soil carbon and nutrients and related extracellular enzymes in successive rotations of Japanese larch plantations

Extensive areas of secondary forests (SF) have been converted into larch plantations to meet the demand for timber and other forest products in northeast China since the early 1960s. However, the successive rotations of larch plantations may alter the understory vegetation and soil properties following reforestation. The aim of this study was to determine how soil carbon and nutrients and related extracellular enzymes changed after conversion from SF to larch plantations. Six larch plantations, including 16-, 30- and 47-year-old in the first rotation, 8-, 16-, and 30-year-old in the second rotation, and one adjacent SF as the 0-year site were selected using the space-for-time substitution (chronosequence) method. The results showed that most soil parameters [pH, soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN) and available potassium (AK) concentrations, and β-glucosidase, N-acetyl-glucosamine, cellobiohydrolase, and phenol oxidase activities] decreased initially from 16- to 30-year-old in the first rotation, and then increased from 30- to 47-year-old in the first rotation and 8-year-old in the second rotation, and were finally reduced from 8- to 30-year-old in the second rotation after conversion from SF, whereas soil bulk density (SBD) showed the inverse pattern. However, SOC (except at 0–10 cm) and nutrient stocks did not change significantly along the chronosequence. Redundancy analysis showed that litter biomass significantly affected most of the soil parameters, and correlated significantly and negatively with the concentrations of SOC, TN, AN and AK, and the activities of β-glucosidase, N-acetyl-glucosamine, cellobiohydrolase and phenol oxidase, while it had a significant positive relationship with SBD. Thus, rational thinning treatments should be conducted at earlier 16 years to create available space and favorable conditions for understory vegetation and litter decomposition. The appropriate rotation age of a larch plantation should be > 45 years with effective measures to maintain soil sustainability.

Depth profile of plant nutrients and acidity in a non-allophanic Andosol as affected by a half-century of fertilization

ABSTRACT To clarify the effects of long-term fertilization on the depth profile of plant nutrients and soil acidity in non-allophanic Andosols, a soil survey was conducted on fertilized grassland and adjacent secondary forest in Kuju highland, Oita Prefecture, Japan. Both of the experimental plots had been managed as a semi-natural grassland (managed by cutting, mowing, and burning for raising cows) before mid of the 1960s, and then, the former had been converted into reclaimed grassland with applying agricultural materials such as fertilizers, manure, and lime, and the latter had been abandoned which resulted in secondary succession into the secondary forest. The comparison of the depth profiles between the two plots revealed that the applied Ca2+ and Mg2+ reached at least 100 cm depth of the non-allophanic Andosol profile. The soil pH was increased at least at the depth of 100 cm, and the plant-toxic level of soil acidity (≥12 mmol kg−1), which is one of the characteristic properties of non-allophanic Andosols, was decreased in the fertilized grassland soil. Soil available P was also observed to be increased at least 80 to 100 cm depth, although the mobility was smaller than those of exchangeable cations and soil acidity. Other soil chemical properties, such as cation exchange capacity, total C and N contents, pyrophosphate-extractable Al (Alp) and Fe (Fep), acid-oxalate-extractable Al (Alo), Fe (Feo), and Si (Sio), Alp/Alo ratio, and Alo + 1/2 Feo, were not significantly altered by the modern grassland management activities. This study reveals considerable loss of plant nutrients from the fertilized grassland soil of a non-allophanic Andosol during a half-century. The loss of plant nutrients should be reduced for sustainable agriculture and conserving the natural environment.

A Method for Performing Reforestation to Effectively Recover Soil Water Content in Extremely Degraded Tropical Rain Forests

Deforestation continues to be extensive in the tropics, resulting in reduced soil water content. Reforestation is an effective way to recover soil water content, but the recovery depends on the type of reforestation efforts that are implemented. Monoculture of fast-growing species is a common reforestation strategy, because it is an effective means of preventing landslides resulting from the frequent typhoons and heavy rains in the tropics and easy to implement. To quantify whether monoculture plantings can help recover soil water content, we initiated a reforestation project within a 0.2 km2 area of an extremely degraded tropical monsoon forest. We hypothesized that much higher transpiration rate of fast-growing tree species would deplete soil water more than the dominant slow-growing species in the adjacent secondary tropical rain forest during both wet and dry seasons, thereby resulting in much lower soil water content. To test this hypothesis, we compared transpiration rates and key functional traits that can distinguish transpiration rates between fast-growing and dominant slow-growing species in both wet and dry seasons. We also quantified whether soil water content around these species differed. We found that fast-growing species had transpiration rate and transpiration-related trait values that were 5–10 times greater than the dominant slow-growing species in both seasons. We also found that soil water content around dominant slow-growing species was 1.5–3 times greater than for fast-growing species in both seasons. Therefore, reforestation based on monoculture plantings of fast-growing species seems difficult to effectively recover the soil water content. We also provide a simple method for guiding the use of reforestation efforts to recover soil water content in extremely degraded tropical rain forests. We expect that this simple method can be an effective means to restore extremely degraded tropical rain forests in other parts of the world.

Soil carbon and associated bacterial community shifts driven by fine root traits along a chronosequence of Moso bamboo (Phyllostachys edulis) plantations in subtropical China

Moso bamboo (Phyllostachys edulis) is widely considered to be effective in capturing and sequestering atmospheric C, but the long-term effects of extensive management strategies on soil organic carbon (SOC), bacterial communities, fine root (FR, ø ≤ 2 mm) traits, and their inherent connection remain unclear. In this study, we simultaneously measured the SOC content of the bulk and rhizosphere soil fractions, the aggregate stability, the chemical composition of SOC (solid-state 13C nuclear magnetic resonance [NMR]), the bacterial community structure in the rhizosphere, and the FR morphological traits including biomass, specific root length (SRL), and root length density (RLD) along a chronosequence (stand age of 19, 37, and 64 years) of extensively managed Moso bamboo plantations and in an adjacent secondary forest as a control. The organic C content in both the rhizosphere and bulk soil increased rapidly with plantation age in the 0–20- and 20–40-cm soil layers, accompanied by an increase in the aggregate stability. FR traits including biomass, SRL, and RLD also increased continuously in response to soil C:N:P stoichiometry. All of these traits were significantly correlated with SOC, occluded particulate organic C (oPOC), and mineral-associated organic C (MOC), suggesting that FR traits could drive the soil C sequestration with the plantation age. Further analysis indicated that the microbial biomass C (MBC) content, MBC/total organic carbon (TOC) ratio, and bacterial abundance decreased with the plantation age, and the shift from soil oligotrophy to copiotrophy bacteria were mainly driven by changes in FR traits and SOC properties. Such a reassembly of bacterial communities combined with an increase in root biomass is favorable for the accumulation of stable C functional groups (alkyl C or aromatic C). Our findings indicate that extensive management regimes of Moso bamboo plantations could promote long-term soil C sequestration especially in the rhizosphere by promoting the formation of soil aggregates and organic-mineral complexes and by shifting bacterial community composition, and that these changes can be inferred through changes in the FR traits.

Evaluation of physicochemical attributes of a yellow latosol under agroforestry system as compared to secondary forest in the Eastern Amazon

In Brazil, the productive and sustainable use of Amazonian soils under agroforestry systems (AFS) has been considered a research challenge. This study aimed to evaluate the physicochemical attributes of a soil under AFS, comparing it with the soil under an adjacent secondary forest (SF). The study was carried out in an AFS area cultivated with passion fruit (Passiflora edulis), cupuacu (Theobroma grandiflorum) and Brazilian mahogany (Swietenia macrophylla), between 2005 and 2019. Both study areas (AFS and SF) were divided into five blocks. Sampling was carried out in two soil depths (0–20 cm and 20–40 cm), which was subjected to chemical analysis to determine the pH in water, contents of macro- and micronutrients, exchangeable bases, exchangeable aluminum, base saturation, cation exchange capacity and organic matter contents. As for the physical attributes, penetration resistance (PR) up to 40 cm deep in the soil was evaluated, using 50 randomized measurement per study area. The contents of macronutrients were higher in AFS, and the content of organic matter was higher in SF. The contents of micronutrients did not follow a specific pattern, and presented a similar distribution in both environments. The PR was higher in SF, showing a linear behavior that increases with increasing depths, while in AFS, there was a stabilization tendency within soil depth. Soil fertility was better in AFS, mainly due to the residual contents of periodic fertilization, in addition to presenting better conditions for root establishment.

A seed rain community in a reforested post-agricultural field and adjacent secondary forest of Mount Papandayan Nature Reserve, West Java, Indonesia

Understanding the mechanisms and barriers to the restoration of degraded land, especially post agriculture, will help provide protocols on effective ways of restoration into functional ecosystems. One of the barriers in early stages of forest restoration is the arrival and availability of propagules. Seed rain and factors affecting it (i.e., distance to the forest edge, species diversity and surrounding vegetation) were measured in a reforested post-agricultural field and in an adjacent secondary forest. Multivariate glm analysis was used on the seed rain community data and univariate lm analysis on the most abundant seed captured (i.e., Schima wallichii (DC.) Korth.). After 8 months of seed rain collection, there was a total of 3596 seeds from eight tree species. Seeds were more abundant and more diverse in the secondary forest (74.9%, 8 species) compared to the reforested field (24.1%, 2 species). There was a limitation on seed dispersal in reforested field from the adjacent forest. The abundance of S. wallichii seeds determined by the dominance of adult trees (136 trees/ha in the forest and 115 trees/ha in the reforested field). Our study suggests, that after 7 years of planting, the reforested field has received limited seed rain and has not yet recovered.

English

This study sought to assess the contribution of coffee agroforestry systems (CAFS) in conserving tree diversity and carbon stocks in the western region of Cameroon. Inventory was carried out in 52 plots laid out in CAFS and in adjacent secondary forest. Above-ground biomass was estimated using allometric method. A total of 30 species belonging to 19 families were identified in CAFS and 30 species belonging to 15 families in the forest. The Jaccard similarity index between CAFS and forest was 43%. In the CAFS, the average value of Shanon diversity index was 1.61, reflecting a low diversity. The average tree density was 133 stems/ha in CAFS and 345 stems/ha in the forest. The CAFS stored an amount of carbon of 24.28 tC/ha, representing only 10.30% of the average amount of carbon stored by the forest (235.88 tC/ha). In the CAFS, Elaeis guineensis was the most dominant species with an important value index of 169.96%. The most efficient species for carbon sequestration were Triplochiton scleroxylon with 2.38 tC/tree. These results indicate the need to integrate CAFS as a biodiversity conservation and carbon sequestration land-use system due to the many socio-economic and ecological benefits they provide both in climate change adaptation and mitigation. Key words: Coffee agroforestry system, diversity, ecosystem services, climate change mitigation, carbon stock.  

Effects of freeze-thaw and soil moisture on content and spectral structure properties of dissolved organic matter in forest soil leachates.

The contents and stability of soil dissolved organic matter (DOM) can affect key processes of soil carbon and nitrogen cycle. The responses of DOM content and its spectral structure pro-perties in forest soils to climate change remain unclear. We collected soil samples from two temperate forests, i.e., the broadleaf and Korean pine mixed forest (BKPF) and adjacent secondary white birch forest (WBF), in Changbai Mountains, northeastern China. Using a combination of three-dimensional fluorescence spectrum and parallel factor analysis, a simulated freeze-thaw experiment was conducted in the laboratory. We examined the effects of freeze-thaw intensity, freeze-thaw cycle and their interaction on the content, components and spectral properties of DOM leached from the two forest surface soils with different moisture levels. The results showed that DOM content and components of soil leachates varied with forest types, soil moisture, freeze-thaw intensity and freeze-thaw cycle. The DOM content in the leachates was lowest at medium moisture level and was significantly affected by the high freeze-thaw intensity. In addition, the DOM content increased first and then decreased with the increases of freeze-thaw cycles. Three fluorescence components of DOM in the forest soil leachates were identified as humic acid-like DOM, fulvic acid-like DOM and protein-like DOM. The DOM components of BKPF soil leachates were mainly consisted of fulvic acid-like substances with a high humification index. However, the DOM from WBF soil leachates was dominated by humic acid-like substances with low stability, and the three fluorescence components were significantly affected by the freeze-thaw intensity. Results from the redundancy analysis showed that under the experimental conditions, forest type played a leading role in changing DOM properties. The DOM content and its three fluorescence intensities of WBF soil leachates were higher than those of BKPF. Soil moisture significantly affected the aromaticity of DOM in the forest soil leachates, and the DOM aromaticity of soil leachates from the two forest stands ranked as medium moisture > high moisture > low moisture. With the increases of freeze-thaw intensity, the DOM aromaticity of BKPF soil leachates significantly decreased. Furthermore, the increases of freeze-thaw cycles significantly increased the humification degree of DOM in the forest soil leachates. Therefore, upon different freeze-thaw disturbance, the DOM content and bioavailability of soil leachates with low moisture tended to increase, particularly in the WBF soil leachates, which may result in an increased lea-ching of DOM in temperate forest soils during spring freeze-thaw periods. The results provide a refe-rence for further investigating DOM turnover in temperate forest soils during spring freeze-thaw periods.

Evaluation of Physicochemical Properties of Sandy-Textured Soils under Smallholder Agricultural Land Use Practices in Sarawak, East Malaysia

A study was conducted in the Sabal area, Sarawak, to evaluate the physicochemical properties of sandy-textured soils under smallholder agricultural land uses. Study sites were established under rubber, oil palm, and pepper land uses, in comparison to the adjacent secondary forests. The sandy-textured soils underlain in all agricultural land uses are of Spodosols, based on USDA Soil Taxonomy. The soil properties under secondary forests were strongly acidic with poor nutrient contents. Despite higher bulk density in oil palm farmlands, soil properties in rubber and oil palm land uses showed little variation to those in secondary forests. Conversely, soils under pepper land uses were less acidic with higher nutrient contents at the surface layer, especially P. In addition, soils in the pepper land uses were more compact due to human trampling effects from regular farm works at a localized area. Positive correlations were observed between soil total C and soil total N, soil exchangeable K, soil sum of bases, and soil effective CEC, suggesting that soil total C is the determinant of soil fertility under the agricultural land uses. Meanwhile, insufficient K input in oil palm land uses was observed from the partial nutrient balances estimation. In contrast, P and K did not remain in the soils under pepper land use, although the fertilizers application by the farmers was beyond the crop uptake and removal (harvesting). Because of the siliceous sandy nature (low clay contents) of Spodosols, they are poor in nutrient retention capacity. Hence, maintaining ample supply of organic C is crucial to sustain the productivity and fertility of sandy-textured soils, especially when the litterfall layers covering the E horizon were removed for oil palm and pepper cultivation.

Using multi-source remote sensing data to classify larch plantations in Northeast China and support the development of multi-purpose silviculture

Due to increasing timber demands, large areas of secondary forests have been converted to larch plantations (LPs) in Northeast China because the secondary forests could not produce timber as much as LPs. However, there are a series of ecological problems such as lower soil fertility, reduced water-holding capacity and acidification of surface runoff water occurring in LPs because of the single-species composition of LPs. Therefore, a guidance on how to transform LPs into larch-broadleaf mixed forests (LBMFs) at a large spatial scale is needed for local foresters. First, Landsat time series data set and SPOT-5 images were combined to map the spatial–temporal distribution of LPs in Northeast China. Then, the topographical characteristics of LPs in 2010s were determined. Furthermore, three sub-regions of LPs were divided closely linking to their ecosystem services and forest management aims. Finally, detailed information on how to transform the LPs into LBMFs was given according to the three sub-regions. The results showed that the area of LPs increased during 1980s and 2010s, and reached 2.61 million ha in 2010s. Of which, 0.72 million ha (27.6%) and 1.89 million ha (72.4%) LPs distributed in slopes less than 5° and greater than 5°, respectively. Of the LPs (72.4%) in slopes greater than 5°, 48.7 and 23.7% located in downslope (LPs locating at the down slope of adjacent secondary forests in the same aspect) and upslope (LPs locating at the up slope of adjacent secondary forests in the same aspect), respectively; 0.10 million ha (3.8%) located in slopes greater than 25°. The LPs were divided into Sub-Regions-I, II, III according to slopes. For Sub-region-I (top role is to produce timber), self-fertilizing shrub species can be introduced after clean cutting for young-aged LPs, and release thinning can be applied for middle-aged LPs, fast growth thinning for near-matured LPs, and clear cutting for matured LPs. For Sub-Region-II (the priority is to provide water conservation combined with timber production), the LPs should be induced into LBMFs. The LPs located the downslope positions in Sub-Region-II can be transformed to LBMFs by natural regeneration of broadleaved tree species after thinning because of enough seed sources of broadleaved tree species from the secondary forests locating the upslope positions. The LPs located the upslope positions or the region where seed sources of broadleaved tree species are unavailable in Sub-Region-II must be induced to LBMFs by artificial regeneration. For Sub-Region-III (the preference is only for water conservation because the slope is greater than 25°), the LPs should be particularly protected from intensive disturbances, and induced into LBMFs by natural regeneration.

Erosion proxies in an exotic tree plantation question the appropriate land use in Central Chile

In South-Central Chile, slopes degraded by former erosion have been afforested with exotic tree species since the 1950s for erosion protection. From 1975 on, primary and secondary forests have increasingly been replaced by tree plantations. This practice is often justified by claiming plantations would similarly protect the soil from erosion, even on areas which used to be natural forest. We assessed if plantations offer a comparable level of erosion protection as the natural forests. A six-year-old Eucalyptus globulus (Labill.) plantation was compared to an adjacent secondary forest using soil profiles and erosion proxies, i.e. topsoil parameters linked to erosion and 137Cs inventories. These pointed to higher erosion in the plantation: the mean bulk density of the plantation was 22% higher compared to the forest site, the gravel content in the plantation was 61% higher, the organic matter content was 20% lower, the mean thickness of the litter layer was 2.2cm lower and the total sand content was 20% higher. The soil loss of the plantation was estimated to be between 4.8cm (mean profile truncation) and 6cm (137Cs approach). These results clearly hint to the conclusion, that the tree plantations in South-Central Chile might promote soil erosion instead of preventing it. Thus, current land use management practices seem to impose erosion risks on Chilean soils raising concern about the sustainable development within the study site.

Soil fertility management in indigenous homegardens of Central Amazonia, Brazil

Homegardens in an upland forest area in the Kwata-Laranjal indigenous territory (state of Amazonas, central Amazonia) were studied to assess how their management contributes to soil fertility. The characteristics of the homegarden soil were compared with those of adjacent primary and secondary forest, at soil depth of 0–10, 10–20 and 20–30 cm. Significant homegarden effects were observed, which raised pH (H2O) (4.3–4.4 at 0–20 cm) and phosphorus content (5–14 mg kg−1 at 0–30 cm); and decreased the content of calcium (0.1 cmolc kg−1 at 20–30 cm). At the same time, levels observed in homegardens for aluminum (3.0–3.2 cmolc kg−1), organic carbon (11–13 g kg−1), calcium (0.24–0.38 cmolc kg−1 at 0–20 cm), magnesium (0.08–0.20 cmolc kg−1) and potassium (0.06–0.10 cmolc kg−1) were not significantly different from those of primary and secondary forest. These results indicate that the management of these homegardens contributes to maintain or increase soil fertility. However, feasible management options to increase the content of these soils in carbon, calcium, magnesium and potassium are highly desirable.

Ant and termite communities in isolated and continuous forest fragments in Singapore

The conservation of tropical rainforest biodiversity is a pressing issue, due to the rapid rate of deforestation. Secondary forests may provide a useful alternative to old growth forests, as they often contain a substantial proportion of the original biodiversity. In this study, we investigate species richness, density and composition of ants and termites in six forest sites in Singapore, each differing in habitat isolation and land-use history. The six sites include an old growth forest, a selectively logged old growth forest, and four secondary forests: either located on abandoned agricultural lands or in abandoned villages, and either isolated or adjacent to old growth forests. We found that the old growth forest had significantly higher species density of ants and termites than any other site. Rarefaction curves showed that ant and termite species richness were highest in the old growth forest followed by the selectively logged forest albeit these results were not significantly different from other sites. Ant species composition changed along a gradient of fragment isolation. Termite community composition in the old growth forest shared a higher proportion of species with the adjacent secondary forest, than with the selectively logged old growth forest, suggesting that the species pool of adjacent habitats is important for species re-colonisation of regenerating habitats. Our results suggest, albeit without replications, that secondary forests differ in conservation value and that disturbed habitats in continuous forest fragments recover more rapidly than isolated ones. Further, we emphasise the importance of old growth forest fragments within man-made ecosystems as sources of original biodiversity.