Recovery of woody plant diversity in tropical rain forests in southern China after logging and shifting cultivation

Logging and intense shifting cultivation have caused major degradation of tropical forests and loss of biodiversity. Understanding the direct and indirect effects of those land uses on plant biodiversity is essential to the restoration of tropical forests. We compared the species diversity, community composition and basal area of all stems ?1 cm dbh among 18 1-ha tropical lowland and montane rain forest plots with a well-recorded long-term history of shifting cultivation and logging on Hainan Island, south China. We also explored the relative importance of disturbance and environmental factors in determining forest recovery. We found that the species density and diversity in old growth forests were higher than in shifting cultivation fallows (55 years old) but lower than in logged forests (35–40 years since logging). The species composition of shifting cultivation fallows was distinct from other forest types but logged forests were similar to old growth forests, especially in lowland forests. Disturbance intensity was the most frequently important factor in determining species composition, species density, diversity, and basal area accumulation. Soil nutrient availability explained some of the variation in species composition and diversity. Stem density was related to multiple factors including disturbance history, soil nutrients, and distance to old-growth forest. In general, we found that disturbance intensity was a better predictor of forest structure and diversity than edaphic environmental variables, highlighting the importance of human impacts in shaping tropical forest successional pathways.     

Effect of land-use and elevation on microbial biomass and water extractable carbon in soils of Mt. Kilimanjaro ecosystems

Microbial biomass carbon (MBC) and water-extractable organic carbon (WOC) – as sensitive and important parameters for soil fertility and C turnover – are strongly affected by land-use changes all over the world. These effects are particularly distinct upon conversion of natural to agricultural ecosystems due to very fast carbon (C) and nutrient cycles and high vulnerability, especially in the tropics. The objective of this study was to use the unique advantage of Mt. Kilimanjaro – altitudinal gradient leading to different tropical ecosystems but developed all on the same soil parent material – to investigate the effects of land-use change and elevation on MBC and WOC contents during a transition phase from dry to wet season. Down to a soil depth of 50 cm, we compared MBC and WOC contents of 2 natural (Ocotea and Podocarpus forest), 3 seminatural (lower montane forest, grassland, savannah), 1 sustainably used (homegarden) and 2 intensively used (maize field, coffee plantation) ecosystems on an elevation gradient from 950 to 2850 m a.s.l. Independent of land-use, both MBC and WOC strongly increased with elevation on Mt. Kilimanjaro corresponding to ecosystem productivity and biodiversity. Through the agricultural use of ecosystems MBC and WOC contents decreased – especially in surface layers – on average by 765 mg kg⁻¹ for MBC and 916 mg kg⁻¹ for WOC, compared to the respective natural ecosystems. The decrease with depth was highest for forests > grasslands > agroecosystems and also was positively correlated with elevation. We conclude that MBC and WOC contents in soils of Mt. Kilimanjaro ecosystems are highly sensitive to land-use changes, especially in topsoil. The MBC and WOC contents were considerably reduced even in sustainable agricultural systems. Since MBC and WOC are very fast reacting and sensitive C pools, we expect a decrease in other soil C pools accompanied by a strong decrease in fertility and productivity due to changes in land use from natural to agricultural ecosystems.     

Are we approaching ‘peak timber’ in the tropics?

Over the past few decades, tropical timber production in many Asia–Pacific countries has been akin to the symmetric logistic distribution curve, or ‘Hubbert Curve’, observed in the exploitation of many non-renewable resources—a rapid increase in production followed by a peak and then decline. There are three principal reasons why logging of native tropical forests resembles the mining of a non-renewable resource: the standard cutting cycle of 30–40 years is too brief to allow the wood volume to regenerate; tropical logging catalyses considerable deforestation; and the bulk of logging is undertaken by multinational corporations with little interest in long-term local sustainability. Unless something fundamental changes, we believe tropical forests will continue to be overharvested and cleared apace, leading to an inevitable global decline in tropical timbers of non-plantation origin. It has become common these days to speak of ‘peak oil’. In the tropics, we suggest that we should also begin to discuss the implications of ‘peak timber’.     

Global food security,biodiversity conservation and the future of agricultural intensification

There is vigorous debate about the potential for reforestation to offset losses in biodiversity associated with tropical deforestation, but a scarcity of good data. We quantified developmental trajectories following active restoration (replanting) of deforested pasture land to tropical Australian rainforest, using 20 different bird community indicators within chronosequences of multiple sites. Bird species composition in restored sites (1–24 years old) was intermediate between that of reference sites in pasture and primary rainforest. Total species richness was much less sensitive to land cover change than composition indicators, because of contrasting species-specific response patterns. For example, open-country (grassland/wetland) bird species declined in richness and abundance with increasing site age, while rainforest-dependent species increased. Results from two different landscapes (uplands and lowlands) were remarkably consistent, despite differing bird assemblages. After 10 years, restored sites averaged about half the number of rainforest-dependent bird species typical of rainforest. Mean values at around 20 years overlapped with the “poorest” rainforest reference sites, but projections suggest that >150 years are required to reach mean rainforest levels, and high variability among sites means that many were not on track towards ever achieving a rainforest-like bird community. Regional rainforest endemics were half as likely to occupy older revegetated sites as non-endemic rainforest-dependent species. Between-site variability and slow colonisation by regional endemics strongly constrain the potential of rainforest restoration to offset the biodiversity impacts of tropical deforestation. The results also mean that ongoing monitoring of biodiversity is an essential part of restoration management.     

Scale-independent significance of river and riparian zones on three sympatric Myotis species in an agricultural landscape

Conserving biodiversity in agricultural landscapes is an urgent issue. The effective conservation of biodiversity requires plans based on species’ habitat preferences at multiple spatial scales. We examined how the foraging habitat selection of bats varied with grain size (50, 150, 250, and 350 m) and how habitat selection in the home range differed from that in the foraging habitat in an agricultural landscape. Focusing on three sympatric Myotis species (Myotis petax, Myotis gracilis, and Myotis frater), we radio-tracked 10 individuals of each species for 121 nights in Hokkaido, northern Japan. Rivers and broadleaved riparian forests were commonly preferred at multiple scales, although the preferred land-cover type was dependent on both extent and grain size for most species. The best grain sizes for predicting the foraging-habitat use of M. petax and M. gracilis were 50 and 150 m. By contrast, M. frater showed no tendency across the grain sizes. Our results indicate that it is necessary to consider both extent and grain size to understand the habitat selection of bats. Our findings also suggest that focusing primarily on preferred land-cover types at multiple scales is effective for conservation planning, given the limited resources in terms of time, manpower, and finances. Although arable did not negatively affect the selection of foraging habitats and home ranges in these bat species, preventing the loss of rivers and forests should be prioritized over preventing arable land expansion.     

Old manor parks as potential habitats for forest flora in agricultural landscapes of Estonia

Forest biodiversity conservation in intensively managed agricultural landscapes is a constant concern. The dispersal ability of forest plants is, hypothetically, the major limiting factor in fragmented forest landscapes and, therefore, we tested the validity of the theoretical dispersal scheme for plants in fragmented landscapes: ancient forest > woody corridor > emerging forest patch. To this end, we examined the distribution pattern of forest-dwelling plant species in rural landscapes, specifically the occurrence of common forest plant species in old historical forests and in closed-canopy stands of rural ornamental parks, planted on an agricultural land one–two centuries ago.We found that (i) the shade tolerant plant flora in parks’ stands more resemble forests than woody linear habitats (corridors), (ii) nearly 50% of the local forest species pool was present in parks, (iii) the abundance of seed source habitats and the ecological quality of the target habitat determine success rate of colonization. Models predicted that optimal stand characteristics for forest herbs are a minimum area 2.5 ha, canopy closure 0.7–0.8, basal area of trees 10–20 m² ha^?1 and the presence of moderate understory management.We conclude that only patch-type habitats provide suitable environmental conditions for forest-specific plant species. Many common forest plant species are capable of long-distance dispersal between habitat patches across hostile agricultural land, and accordingly, their dispersal follows a modified scheme of the island biogeography, without intermediary role of corridor habitats. Old rural manor parks provide an ecosystem service for nature conservation by harbouring forest biodiversity, and should be considered as potential refugium habitats.     

Inhibition of the germination and growth of Phymatotrichopsis omnivora (cotton root rot) by oilseed meals and isothiocyanates

The meals (co-products remaining after oil extraction) from many oilseed crops contain biocidal chemicals that are known to inhibit the growth and activity of some soil microorganisms including several plant pathogens. The fungus Phymatotrichopsis omnivora (Duggar) Hennebert is the causal agent of cotton root rot that has greatly hindered the production of cotton and alfalfa in Texas and the southwestern USA. We investigated the effect of oilseed meals from both brassicaceous plants including mustard and camelina as well as non-brassicaceous plants including jatropha, flax, and Chinese tallow on P. omnivora sclerotial germination and hyphal growth in Branyon clay soil, as well as the effects of 4 types of individual isothiocyanates (ITCs) including allyl, butyl, phenyl, and benzyl ITC on P. omnivora growth on potato dextrose agar (PDA). The oilseed meals were added to the soil at rates of 0%, 1%, and 5% (w/w). The results showed that all tested brassicaceous and jatropha seed meals were able to inhibit P. omnivora sclerotial germination and hyphal growth at 5% and 1% application rates respectively, with mustard seed meal being the most effective. Neither flax nor Chinese tallow showed any inhibitory effects on sclerotial germination. All tested ITCs inhibited P. omnivora OKAlf8 hyphal growth, although the level of inhibition varied with concentration. The IC₅₀ values were 0.62 ± 0.19, 4.47 ± 0.08, 5.67 ± 0.10, and 20.48 ± 0.30 μg cm⁻³ for allyl, butyl, phenyl, and benzyl ITC respectively. These results indicate that press meals of several brassicaceous species as well as jatropha may have potential for reducing cotton root rot.     

Irrigation Capability Evaluation of Illushi Floodplain,Edo State,Nigeria

Many irrigation projects, especially in the developing tropical regions, are embarked upon without any land capability assessment, resulting in avoidable and undesirable ecological consequences. The aim of this study is to assess the irrigation capability potentials of the soils of a rice growing Illushi/Ega community in Edo State of Nigeria. Soils of Illushi/Ega (200 ha) were studied to establish their irrigation capabilities. Water samples were collected from the rivers within and near the sites at the proposed points of intake structures and analyzed for salinity (ECw), permeability (SAR) and ion toxicity [Chlorine (Cl) and Boron (B)]. Gravity irrigation suitability assessment was carried out following the guidelines of the United States Bureau for Land Reclamation (USBR, 1953) and FAO (1979). Results showed that about 5.5 % of the land was non-irrigable, 11.5 % was marginally irrigable, 30.5% was moderately irrigable and 52.5 % highly irrigable.Thus about 83 % of the total land area was found to be irrigable. The results of analyses of irrigation water [E_Cw, SAR and Cl and B (ion toxicity) problems in water sources were 0.1 – 0.7 dS m^- 1, 1.2 – 1.7, 0.6 – 1.8 cmol kg^- 1 and 0.5 – 0.7 mg kg^- 1] also show that there is no indication of salinity or ion toxicity problem.     

Recovery of amphibian species richness and composition in a chronosequence of secondary forests,northeastern Costa Rica

In some tropical regions, following the abandonment of agriculture and pastures, secondary forests can recover plant species richness and forest structure (e.g. canopy cover, biomass); however, the importance of these secondary forests for fauna is not clear. Secondary forests can benefit fauna by providing suitable habitats, connecting forests fragments, and increasing gene flow. Previous studies of forest regeneration have showed different levels of amphibian recovery. In Puerto Rico, 1–5 years old secondary forests achieved similar amphibian species richness and composition in comparison with old-growth forests, while in Brazil secondary forests from 14 to 19 years of recovery only recovered 60% of the species of old-growth forests. We evaluated amphibian recovery in secondary forests in northeastern Costa Rica, by assessing amphibian recovery in 12 secondary forests that vary in age of recovery and in three old-growth forests using visual and acoustic surveys. Our sites varied in terms of their landscape (e.g. amount of surrounding forest) and forest characteristics (e.g. forest age, aboveground biomass, basal area, number of tree species, number of stems, leaf-litter depth), but there was no relationship between these characteristics and amphibian species richness or species composition. We found that amphibians are recovering rapidly in secondary forests in Costa Rica, and even young forests (10–16 years) had similar species richness and composition in comparison with old-growth forests. These forests are providing suitable microhabitats conditions for amphibians. In addition, this study highlights the importance of landscape characteristics. The abundance of amphibian species sources (e.g. forest patches) and connections between forests appear to be helping the species colonize these sites. Worldwide, the area of secondary forests is increasing, and our results show that these habitats are suitable for a diversity of amphibian species, suggesting that these forests can help reduce amphibian population and species decline.     

Uncovering the fruit bat bushmeat commodity chain and the true extent of fruit bat hunting in Ghana, West Africa

Harvesting, consumption and trade of bushmeat are important causes of both biodiversity loss and potential zoonotic disease emergence. In order to identify possible ways to mitigate these threats, it is essential to improve our understanding of the mechanisms by which bushmeat gets from the site of capture to the consumer’s table. In this paper we highlight the previously unrecognized scale of hunting of the African straw-colored fruit bat, Eidolon helvum, a species which is important in both ecological and public health contexts, and describe the commodity chain in southern Ghana for its trade. Based on interviews with 551 Ghanaians, including bat hunters, vendors and consumers, we estimate that a minimum of 128,000 E. helvum bats are sold each year through a commodity chain stretching up to 400 km and involving multiple vendors. Unlike the general bushmeat trade in Ghana, where animals are sold in both specialized bushmeat markets and in restaurants, E. helvum is sold primarily in marketplaces; many bats are also kept by hunters for personal consumption. The offtake estimated in this paper raises serious conservation concerns, while the commodity chain identified in this study may offer possible points for management intervention. The separation of the E. helvum commodity chain from that of other bushmeat highlights the need for species-specific research in this area, particularly for bats, whose status as bushmeat is largely unknown.     

Reviewing SEBAL input parameters for assessing evapotranspiration and water productivity for the Low-Middle São Francisco River basin,Brazil: Part B: Application to the regional scale

The intensification of irrigated agriculture in the semi-arid region of Brazilian North-east results in a change of natural vegetation by irrigated fruit crops. New applications of remote sensing technologies are presented in this paper to estimate the impact of this land use change on regional water consumption – and ultimately the water balance – in Low-Middle São Francisco River basin. Ten Landsat images for a period from 2001 to 2007 were used, together with the locally calibrated Surface Energy Balance Algorithm for Land (SEBAL) and agro-meteorological data to derive information on regional actual evapotranspiration (ET), biomass production (BIO), and crop water productivity (CWP). The Landsat-based results revealed that regional mean ET for irrigated crops was 3.6 mm d^?1 being higher than for natural vegetation (1.4 mm d^?1). Similar incremental ET values between natural and irrigated ecosystems were found from micro-meteorological field experiments. The consequence of this land use change on São Francisco River's downstream stream flow was assessed by estimating volumetric incremental evapotranspiration at the regional scale. The bio-physical crop water productivity per unit of actual evapotranspiration (CWP_ET) varied between 0.4 and 1.7 l of wine per m³ of water for wine grapes; 1.7 and 4.0 kg of fruits per m³ of water for table grapes; and 2.2 and 5.0 kg of fruits per m³ of water for mangos. The accompanying paper (Part A) describes the calibration and validation of SEBAL steps witnessed under the actual field conditions in this study area.     

What are the limits of the drilosphere? An incubation experiment using Metaphire posthuma

The near infrared reflectance spectroscopy (NIRS) method was used in the present study to compare earthworm-made soil aggregates to aggregates found in the surrounding bulk soil. After initially assessing the daily cast production of Metaphire posthuma, boxes with soil incubated with M. posthuma and control soils were subjected to wetting in order to reorganize the soil structure. After two months of incubation, soil aggregates produced by earthworms (casts and burrows), soil aggregates that were appeared to be unaffected by earthworms (bulk soil without visible trace of earthworm bioturbation from the earthworm treatment) and soil aggregates that were entirely unaffected by earthworms (control – no earthworm – treatment) were sampled and their chemical signatures analyzed by NIRS. The production of below-ground and surface casts reached 14.9 g soil g worm^?1 d^?1 and 1.4 g soil g worm^?1 d^?1, respectively. Soil aggregates from the control soils had a significantly different NIRS signature from those sampled from boxes with earthworms. However, within the earthworm incubation boxes the NIRS signature was similar between cast and burrow aggregates and soil aggregates from the surrounding bulk soil. We conclude that the high cast production by M. posthuma and the regular reorganization of the soil structure by water flow in and through the soil lead to a relatively homogenous soil structure. Given these results, we question the relevance of considering the bulk soil that has no visible activity of earthworm activity as a control to determine the effect of earthworms on soil functioning.     

Differences in soil respiration between different tropical ecosystems

We examined the relationship between soil respiration rate and environmental determinants in three types of tropical forest ecosystem—primary forest, secondary forest, and an oil palm plantation in the Pasoh Forest Reserve on the Malaysian Peninsula. In August 2000, the soil respiration rate and environmental factors (soil temperature, soil water content, soil C and N contents, biomass of fine roots, and microbes) were measured at 12–16 points in research quadrats. Soil respiration rates were 831 ± 480, 1104 ± 995, 838 ± 143, 576 ± 374, and 966 ± 578 (mean ± S.D.) mg CO₂ m⁻² h⁻¹ in the primary forest canopy and gap site, secondary forest canopy and gap site, and oil palm plantation, respectively. Although the mean soil respiration rates in the three forest ecosystems did not differ significantly, differences were evident in the environmental factors affecting the soil respiration. The major causes of spatial variation in soil respiration were fine root biomass, soil water content, and soil C content in the primary and secondary forests and oil palm plantation, respectively.     

Nitrous oxide production in turfgrass systems: Effects of soil properties and grass clipping recycling

Soil N₂O emissions can affect global environments because N₂O is a potent greenhouse gas and ozone depletion substance. In the context of global warming, there is increasing concern over the emissions of N₂O from turfgrass systems. It is possible that management practices could be tailored to reduce emissions, but this would require a better understanding of factors controlling N₂O production. In the present study we evaluated the spatial variability of soil N₂O production and its correlation with soil physical, chemical and microbial properties. The impacts of grass clipping addition on soil N₂O production were also examined. Soil samples were collected from a chronosequence of three golf courses (10, 30, and 100-year-old) and incubated for 60 days at either 60% or 90% water filled-pore space (WFPS) with or without the addition of grass clippings or wheat straw. Both soil N₂O flux and soil inorganic N were measured periodically throughout the incubation. For unamended soils, cumulative soil N₂O production during the incubation ranged from 75 to 972 ng N g⁻¹ soil at 60% WFPS and from 76 to 8842 ng N g⁻¹ soil at 90% WFPS. Among all the soil physical, chemical and microbial properties examined, soil N₂O production showed the largest spatial variability with the coefficient of variation ~110% and 207% for 60% and 90% WFPS, respectively. At 60% WFPS, soil N₂O production was positively correlated with soil clay fraction (Pearson's r = 0.91, P < 0.01) and soil NH₄⁺–N (Pearson's r = 0.82, P < 0.01). At 90% WFPS, however, soil N₂O production appeared to be positively related to total soil C and N, but negatively related to soil pH. Addition of grass clippings and wheat straw did not consistently affect soil N₂O production across moisture treatments. Soil N₂O production at 60% WFPS was enhanced by the addition of grass clippings and unaffected by wheat straw (P < 0.05). In contrast, soil N₂O production at 90% WFPS was inhibited by the addition of wheat straw and little influenced by glass clippings (P < 0.05), except for soil samples with >2.5% organic C. Net N mineralization in soil samples with >2.5% organic C was similar between the two moisture regimes, suggesting that O₂ availability was greater than expected from 90% WFPS. Nonetheless, small and moderate changes in the percentage of clay fraction, soil organic matter content, and soil pH were found to be associated with large variations in soil N₂O production. Our study suggested that managing soil acidity via liming could substantially control soil N₂O production in turfgrass systems.     

Comparing measurements methods of carbon dioxide fluxes in a soil sequence under land use and cover change in North Eastern Spain

Carbon dioxide measurements from soil surface may indicate the potential for soil respiration and carbon consumption according to microbial biomass and root activity. These processes may be influenced by land use and cover change, and abandonment especially in the upper soil organic layer. Seven environments from cultivation to late abandonment, with the same soil type classified as Lithic Xerorthent, were tested to ascertain the respiration capacity according to the current use and cover, and to establish the ability to preserve and eventually increase the organic matter pools after abandonment. Given the importance of carbon dioxide measurements at soil surface, a comparison between the classic soda lime method (SL) and a rapid method based on infrared sensor analyzer (IR) was performed from autumn 2008 to autumn 2009 in the field. The field measurements of CO₂ proved significant correlations between the values from the two techniques under the same natural conditions and along the period of observation. However, the values of CO₂ measured by the soda lime method were always higher than those obtained by the infrared analyzer. This pattern was attributed to the difference in time of measurement, larger in the former method, and type of measurement technique. Despite that the trend of measured CO₂ values was rather similar along the year. On average, the highest values of CO₂ emission in the field were recorded in the warmest periods of the year and with soil surface moisture not lower than 3% independently on the method used. High soil surface temperature with soil moisture below 3% decreased drastically the CO₂ production from the dry soil. The cultivated environments and soil under forests have resulted higher CO₂ producers than abandoned soils depending on the age of abandonment, climatic conditions, and within abandonment perturbations. Those abandoned soils preserved by perturbations like wildfire showed a higher potential for accumulating organic carbon, as indicated by the lowest emission of CO₂ with respect to SOC content, during the period of observation. Results demonstrated the reliability of the methods used to evaluate the soil carbon dioxide production capacity and allowed to classify through environments with increasing potential for carbon sequestration. The classification was rather similar by using both methods indicating a higher susceptibility to carbon loss in the following order: soil under Vines (V) > under Olives (O) > under Pine trees (PI) > under Cork Trees (S) > under Pasture (PR) > under Cistus scrub (MC) > under Erica scrub (MB) by using the SL method and V > O > PI > S > MC > MB > PR by using the IR method. Indications about the need of management of abandoned areas were also considered in order to recover the landscape heterogeneity.     

Dynamic performance assessment of protected areas

Recognizing the importance of preserving biodiversity and ecosystem services, human society has established extensive protected area networks to conserve these resources in recent decades. Are protected areas working as expected? Empirical coarse-scale assessments of this question across large regions, or even globally, tend to answer “yes”, while fine-scale studies of individual protected areas often and repeatedly answer “no”. We conducted a first fine-scale analysis of Brazil’s extensive Amazonian protected area network (1.8 million km²) and have quantitatively estimated conservation effectiveness in light of changing human development pressures in the surrounding landscape. The overall network maintained intact forest cover for 98.6% of protected forest lands, largely agreeing with previous coarse-scale studies. However, detailed examination of 474 individual protected areas unveils a broad range of efficacy. Many protected areas (544,800 km²) experience default protection simply due to their remoteness. Many others (396,100 km²) have provided highly effective protection in the face of substantial human development pressure. Conversely, 12% (38) of protected areas have failed to protect the 27,300 km² that they encompass, and another 7% (23) provide only marginal protection of 37,500 km². Comprehensive landscape assessments of protected area networks, with frequent monitoring at scales matching the patterns of human-caused disturbances, are necessary to ensure the conservation effectiveness and long term survival of protected areas in rapidly changing landscapes. The methods presented here are globally adaptable to all forested protected areas.     

Effect of warming on the temperature dependence of soil respiration rate in arctic,temperate and tropical soils

We examined the response of the temperature coefficient (Q₁₀) for soil respiration rate to changes in environmental temperature through a laboratory incubation experiment. Soil samples were collected from three climatic areas: arctic (Svalbard, Norway), temperate (Tsukuba, Japan) and tropical (Pasoh, Malaysia). The arctic and temperate soils were incubated at 8 °C (control), 12 °C (4 °C warming) and 16 °C (8 °C warming) for 17 days. The tropical soil was incubated at 16 °C (8 °C cooling), 24 °C (control) and 32 °C (8 °C warming). Before and after the incubation experiment, the temperature dependence of soil microbial respiration was measured using an open-airflow method with IRGA by changing the temperature in a water bath. The initial Q₁₀ before the incubation experiment was larger in the soils from higher latitudes: 3.4 in the arctic soil, 2.9 in the temperate soil, and 2.1 in the tropical soil. The response of the microbial respiration rate to change in temperature differed among the three soil types. The temperature dependence of respiration rate in the arctic soil did not change in response to warming by 4 and 8 °C with a Q₁₀ of about 3. On the other hand, the Q₁₀ in the temperate soil decreased with increasing incubation temperature: from 2.8 in soils incubated at 8 °C to 2.5 at 12 °C and 2.0 at 16 °C. In the tropical soil, the Q₁₀ was not changed even by the 8 °C warming with a value of 2.1, whereas the Q₁₀ was increased from 2.1 to 2.7 by the 8 °C cooling. These results suggest that the response of microbial respiration to climatic warming may differ between soils from different latitudes.     

Evapotranspiration and water use efficiency in different-aged Pacific Northwest Douglas-fir stands

We used the eddy-covariance technique to measure evapotranspiration (E) and gross primary production (GPP) in a chronosequence of three coastal Douglas-fir (Pseudotsuga menziesii) stands (7, 19 and 58 years old in 2007, hereafter referred to as HDF00, HDF88 and DF49, respectively) since 1998. Here, we focus on the controls on canopy conductance (g_c), E, GPP and water use efficiency (WUE) and the effect of interannual climate variability at the intermediate-aged stand (DF49) and then analyze the effects of stand age following clearcut harvesting on these characteristics. Daytime dry-foliage Priestley–Taylor α and g_c at DF49 were 0.4–0.8 and 2–6 mm s^?1, respectively, and were linearly correlated (R² = 0.65). Low values of α and g_c at DF49 as well at the other two stands suggested stomatal limitation to transpiration. Monthly E, however, showed strong positive linear correlations to monthly net radiation (R² = 0.94), air temperature (R² = 0.77), and daytime vapour pressure deficit (R² = 0.76). During July–September, monthly E (mm) was linearly correlated to monthly mean soil water content (θ, m³ m^?3) in the 0–60 cm layer (E = 453θ ? 21, R² = 0.69), and GPP was similarly affected. Annual E and GPP of DF49 for the period 1998–2007 varied from 370 to 430 mm and from 1950 to 2390 g C m^?2, respectively. After clearcut harvesting, E dropped to about 70% of that for DF49 while ecosystem evapotranspiration was fully recovered when stand age was ～12 years. This contrasted to GPP, which varied hyperbolically with stand age. Monthly GPP showed a strong positive linear relationship with E irrespective of the stand age. While annual WUE of HDF00 and HDF88 varied with age from 0.5 to 4.1 g C m^?2 kg^?1 and from 2.8 to 4.4 g C m^?2 kg^?1, respectively, it was quite conservative at ～5.3 g C m^?2 kg^?1 for DF49. N-fertilization had little first-year response on E and WUE. This study not only provides important results for a more detailed validation of process-based models but also helps in predicting the influences of climate change and forest management on water vapour and CO₂ fluxes in Douglas-fir forests.     

Toxicity of chlorpyrifos,carbofuran, mancozeb and their formulations to the tropical earthworm Perionyx excavatus

Effects of chlorpyrifos, carbofuran, mancozeb and their formulated products on survival, growth and reproduction of the tropical earthworm Perionyx excavatus were investigated in standard artificial soil. The toxicity of the three chemicals decreased in the order carbofuran > chlorpyrifos > mancozeb. In general, formulations were more toxic than the active ingredients, but differences in LC₅₀ and EC_x values were significant only in two cases and not more than a factor of 2.0. This could mainly be due to masking of the effects of additives in the soil. Comparison with available survival data revealed that P. excavatus is more sensitive than the standard test species Eisenia andrei or E. fetida. The use of tropical species in the risk assessment of pesticides in tropical regions should therefore be encouraged.     

Development of ecosystems to climate change and the interaction with pollution—Unpredictable changes in community structures

Climate change has serious impacts on ecosystems, e.g. species diversity and abundance. It is well known that changes in temperature may have a pronounced influence on the reproductive output, growth and survival of various terrestrial species. However, much less is known on to how changes in temperature combined with exposure to pollution will influence biodiversity, the interaction between species, and the resulting change in species composition. In order to understand the effects of changes in temperature and copper pollution (individually and in combination) on soil communities and processes, a factorial multispecies experiment was performed. Six animal species (representing different functional groups) were exposed in control (30 mg Cu/kg) and copper-contaminated soil (1000 mg Cu/kg) to four temperatures (10, 14, 19, and 23 °C) representing the “summer” range (low to high) for Denmark, and three exposure periods (28, 61, and 84 days). The species composition, feeding activity and OM turnover were assessed throughout. Multivariate analysis displayed significant changes in the food-web both with different copper levels and temperatures, resulting in different species composition for each exposure scenario. The most important species were Enchytraeus crypticus (most sensitive to copper and temperature) and Folsomia candida (most abundant). Major changes in abundance due to temperature occurred in the first 28 days of exposure, where population growth was higher. A temperature dependent population growth rate could be modeled for an exposure period of 28 days, whereas after 61 and 84 days of exposure the data did not fit the model. Especially for treatments that also included Cu, modeling of the population growth was no longer possible. The results of our study indicate that when climate change occurs in polluted areas, the consequences on populations cannot be predicted based on data from non-polluted areas. The risk may be synergistic for certain species, as indicated in the present study, and the final balance may depend on the particular species composition of that ecosystem.