Records 1 - 20 / 599
Competition influences tree growth, but not mortality, across environmental gradients in Amazonia and tropical Africa
Rozendaal, Danaë M.A. ; Phillips, Oliver L. ; Lewis, Simon L. ; Affum-Baffoe, Kofi ; Alvarez-Davila, Esteban ; Andrade, Ana ; Aragão, Luiz E.O.C. ; Araujo-Murakami, Alejandro ; Baker, Timothy R. ; Bánki, Olaf ; Brienen, Roel J.W. ; Camargo, José Luis C. ; Comiskey, James A. ; Djuikouo Kamdem, Marie Noël ; Fauset, Sophie ; Feldpausch, Ted R. ; Killeen, Timothy J. ; Laurance, William F. ; Laurance, Susan G.W. ; Lovejoy, Thomas ; Malhi, Yadvinder ; Marimon, Beatriz S. ; Marimon Junior, Ben Hur ; Marshall, Andrew R. ; Neill, David A. ; Núñez Vargas, Percy ; Pitman, Nigel C.A. ; Poorter, Lourens ; Reitsma, Jan ; Silveira, Marcos ; Sonké, Bonaventure ; Sunderland, Terry ; Taedoumg, Hermann ; Steege, Hans ter; Terborgh, John W. ; Umetsu, Ricardo K. ; Heijden, Geertje M.F. van der; Vilanova, Emilio ; Vos, Vincent ; White, Lee J.T. ; Willcock, Simon ; Zemagho, Lise ; Vanderwel, Mark C. - \ 2020
Ecology 101 (2020)7. - ISSN 0012-9658
climatic water deficit - competition - forest dynamics - mortality - neighborhood effects - soil fertility - trait-based models - tree growth - tropical forest - wood density
Competition among trees is an important driver of community structure and dynamics in tropical forests. Neighboring trees may impact an individual tree’s growth rate and probability of mortality, but large-scale geographic and environmental variation in these competitive effects has yet to be evaluated across the tropical forest biome. We quantified effects of competition on tree-level basal area growth and mortality for trees ≥10-cm diameter across 151 ~1-ha plots in mature tropical forests in Amazonia and tropical Africa by developing nonlinear models that accounted for wood density, tree size, and neighborhood crowding. Using these models, we assessed how water availability (i.e., climatic water deficit) and soil fertility influenced the predicted plot-level strength of competition (i.e., the extent to which growth is reduced, or mortality is increased, by competition across all individual trees). On both continents, tree basal area growth decreased with wood density and increased with tree size. Growth decreased with neighborhood crowding, which suggests that competition is important. Tree mortality decreased with wood density and generally increased with tree size, but was apparently unaffected by neighborhood crowding. Across plots, variation in the plot-level strength of competition was most strongly related to plot basal area (i.e., the sum of the basal area of all trees in a plot), with greater reductions in growth occurring in forests with high basal area, but in Amazonia, the strength of competition also varied with plot-level wood density. In Amazonia, the strength of competition increased with water availability because of the greater basal area of wetter forests, but was only weakly related to soil fertility. In Africa, competition was weakly related to soil fertility and invariant across the shorter water availability gradient. Overall, our results suggest that competition influences the structure and dynamics of tropical forests primarily through effects on individual tree growth rather than mortality and that the strength of competition largely depends on environment-mediated variation in basal area.
Fertilisers differentially affect facultative and obligate parasitic weeds of rice and only occasionally improve yields in infested fields
Tippe, Dennis E. ; Bastiaans, Lammert ; Ast, Aad van; Dieng, Ibnou ; Cissoko, Mamadou ; Kayeke, Juma ; Makokha, Derek W. ; Rodenburg, Jonne - \ 2020
Field Crops Research 254 (2020). - ISSN 0378-4290
Rainfed rice - Rhamphicarpa - Smallholders - soil fertility - Striga
Different fertilisers were field tested to investigate whether they (1) suppress the obligate parasitic weed Striga asiatica and the facultative parasitic weed Rhamphicarpa fistulosa, and (2) favour rainfed rice yields under parasitic weed infestation. Four years of experiments were conducted in southwest Tanzania, in a S. asiatica-infested rainfed upland and a R. fistulosa-infested rainfed lowland field. Treatments included sole mineral (NPK or Di-Ammonium Phosphate —DAP— plus urea), organic (cattle manure or rice husk), combinations of mineral and organic fertilisers and a no-fertiliser control. Fertilisers moderately suppressed the obligate parasite S. asiatica, but no correlations between infestation level and soil fertility status were observed. In the lowland field, fertilisers promoted the facultative R. fistulosa, in particular the ones that included organic components. Plant-available phosphorus, exchangeable potassium and soil organic matter content correlated with R. fistulosa infestation levels. Positive fertiliser effects on yields were found in both parasitic weed infested fields, except in years with high S. asiatica infestation levels. Rice husks alone and rice husks or manure combined with DAP and urea increased yields and soil fertility most. We conclude that fertilisation differentially affects the obligate and facultative parasitic weeds of rice systems; obligate parasites may be slightly suppressed, but facultative parasites may even be stimulated. Meanwhile, consistent rice yield increases under parasitic weed infested conditions cannot be obtained with fertiliser application when parasitic weed infestation levels are too high.
Soil Zinc Is Associated with Serum Zinc But Not with Linear Growth of Children in Ethiopia
Tessema, Masresha ; Groote, Hugo De; Brouwer, Inge D. D; Feskens, Edith J.M. ; Belachew, Tefera ; Zerfu, Dilnesaw ; Belay, Adamu ; Demelash, Yoseph ; Gunaratna, Nilupa S. S - \ 2019
Nutrients 11 (2019)2. - ISSN 2072-6643
Ethiopia - linear growth - preschool children - serum zinc - soil fertility - soil zinc
To our knowledge, the relationships among soil zinc, serum zinc and children's linear growth have not been studied geographically or at a national level in any country. We use data from the cross-sectional, nationally representative Ethiopian National Micronutrient Survey (ENMS) (n = 1776), which provided anthropometric and serum zinc (n = 1171) data on children aged 6⁻59 months. Soil zinc levels were extracted for each child from the digital soil map of Ethiopia, developed by the Africa Soil Information Service. Children's linear growth was computed using length/height and age converted into Z-scores for height-for-age. Multi-level mixed linear regression models were used for the analysis. Nationally, 28% of children aged 6⁻59 months were zinc deficient (24% when adjusted for inflammation) and 38% were stunted. Twenty percent of households in the ENMS were located on zinc-deficient soils. Soil zinc (in mg/kg) was positively associated with serum zinc (in µg/dL) (b = 0.9, p = 0.020) and weight-for-height-Z-score (b = 0.05, p = 0.045) but linear growth was not associated with soil zinc (p = 0.604) or serum zinc (p = 0.506) among Ethiopian preschool children. Intervention studies are needed to determine whether there are causal links between soil and human zinc status.
Impact of arbuscular mycorrhizal fungi and earthworms on soil aggregate stability, glomalin, and performance of pigeonpea, Cajanus cajan
Muchane, Mary N. ; Pulleman, Mirjam M. ; Vanlauwe, Bernard ; Jefwa, Joyce ; Kuyper, Thomas W. - \ 2018
Soil Research 57 (2018)1. - ISSN 1838-675X - p. 53 - 65.
endogeic - epigeic - integrated soil fertility management (ISFM) - soil biota - soil fertility - soil structure
Earthworms and arbuscular mycorrhizal fungi (AMF) modify soil physical and chemical properties. However, little is known about how their interactions affect water-stable aggregation, glomalin and crop performance. A greenhouse experiment was run for 9 months to test the effects of earthworms (endogeic, Pontoscolex corethrurus and epigeic, Dichogaster bolaui) and AMF (none, Glomus etunicatum and Scutellospora verrucosa) on water-stable aggregation, glomalin levels in aggregate size classes and crop performance. The test crop was pigeonpea (Cajanus cajan (L.) Millsp.). The soil material used for the experiment was a humic nitisol from central Kenya mixed with sand (ratio 1: 1). Grass residue (equivalent to 20 t ha-1) was placed on top. The AMF root colonisation and external hyphal length, water-stable macroaggregates and microaggregates, total and easily-extractable glomalin in aggregate size classes, plant biomass and plant N and P uptake were measured. Earthworms were a major source of variation for soil aggregation, glomalin content and crop performance. The epigeic earthworms (D. bolaui) increased the amount of water-stable macroaggregates (by 10%) and glomalin in microaggregates and improved crop (growth and biomass) performance. The endogeic earthworms (P. corethrurus) reduced external hyphal length, root colonisation and crop performance but had no effect on water-stable aggregates and glomalin levels in in aggregate size classes. A significant AMF × earthworm interaction was observed for plant biomass and concentrations of nitrogen (N) and phosphorus (P). The AMF species together with epigeic earthworms increased plant biomass and N and P concentrations. Our results contribute to the understanding of interactions between AMF and earthworms in relation to soil aggregation, plant productivity and nutrient uptake.
Jan Willem van Groenigen: What would the world look like without earthworms? | WURcast
Groenigen, J.W. van - \ 2017
helminths - soil fertility
Data from: Soil-mediated filtering organizes tree assemblages in regenerating tropical forests
Pinho, Bruno Ximenes ; Melo, Felipe Pimentel Lopes de; Arroyo-Rodríguez, Víctor ; Pierce, Simon ; Lohbeck, M.W.M. ; Tabarelli, Marcelo - \ 2017
Universidade Federal Rural de Pernambuco
determinants of plant community diversity and structure - environmental filtering - forest regeneration - functional traits - limiting similarity - secondary succession - soil fertility - community assembly
1.Secondary forests are increasingly dominant in human-modified tropical landscapes, but the drivers of forest recovery remain poorly understood. Soil conditions influence plant community composition, and are expected to change over a gradient of succession. However, the role of soil conditions as an environmental filter driving community assembly during forest succession has rarely been explicitly assessed. 2.We evaluated the role of stand basal area and soil conditions on community assembly and its consequences for community functional properties along a chronosequence of Atlantic forest regeneration following sugar cane cultivation. Specifically, we tested whether community functional properties are related to stand basal area, soil fertility and soil moisture. Our expectations were that edaphic environmental filters play an increasingly important role along secondary succession by increasing functional trait convergence towards more conservative attributes. 3.We sampled soil and woody vegetation features across 15 second-growth (3-30 years) and 11 old-growth forest plots (300 m² each). We recorded tree functional traits related to resource-use strategies (specific leaf area, SLA; leaf dry matter content, LDMC; leaf area, LA; leaf thickness, LT; and leaf succulence, LS) and calculated community functional properties using the community-weighted mean (CWM) of each trait and the functional dispersion (FDis) of each trait separately and all traits together. 4.With exception of LA, all leaf traits were strongly associated with stand basal area; LDMC and SLA increased, while LT and LS decreased with forest development. Such changes in LDMC, LT and LS were also related to the decrease in soil nutrient availability and pH along succession, while soil moisture was weakly related to community functional properties. Considering all traits, as well as leaf thickness and succulence separately, FDis strongly decreased with increasing basal area and decreasing soil fertility along forest succession, presenting the lowest values in old-growth forests. 5.Synthesis. Our findings suggest that tropical forest regeneration may be a deterministic process shaped by soil conditions. Soil fertility operates as a key filter causing functional convergence towards more conservative resource-use strategies, such as leaves with higher leaf dry mass content.
Data from: Soil biota suppress positive plant diversity effects on productivity at high but not low soil fertility
Luo, Shan ; Deyn, G.B. de; Jiang, B. ; Yu, Shixiao - \ 2017
Sun Yat-Sen University
plant diversity-productivity relationship - plant-microbe interactions - soil fertility - subtropical forest
1. Plant community productivity commonly increases with increasing plant diversity, which is explained by complementarity among plant species in resource utilization (complementarity effect), or by selection of particularly productive plant species in diverse plant communities (selection effect). Recent studies have also shown that soil biota can drive the positive plant diversity–productivity relationship by suppressing productivity more in low- than in high-diversity plant communities. However, much remains unknown about whether soil fertility plays a role in determining how soil biota affect plant diversity–productivity relationships. 2. We hypothesized that under high soil fertility conditions, negative soil biota effects dominate, which reduces plant monoculture biomass more than that of high-diversity plant communities. Conversely, under low soil fertility conditions, we hypothesized positive soil biota effects dominate, which facilitates plant resource partitioning and enhances community-level biomass in high-diversity plant communities. Hence we expected positive plant diversity–community productivity relationships under low and high soil fertility conditions but caused by different mechanisms. 3. We tested these hypotheses using woody seedlings and set up plant assemblages with four species richness levels (one, two, four and eight species), and grew them in sterilized and unsterilized (sterilized soil + living soil inoculum) soils at two nutrient levels (low vs. high fertility). 4. We found that at high fertility negative soil biota effects dominated and suppressed plant community biomass more in high-diversity plant communities than in monocultures, resulting in reduced complementarity effects of diverse plant communities and a non-significant plant species richness–community biomass relationship in unsterilized soil. Whereas at low fertility soil biota had net neutral to positive effects on plant community biomass but the beneficial effects did not increase with increasing plant species richness. Instead, soil biota neutrally affected the positive plant species richness–community biomass relationship, presumably due to non-specific effects of beneficial soil biota. 5. Synthesis. Soil biota and soil fertility interactively determine plant species richness–community biomass relationships. Moreover, soil biota modulate the complementary resource use among plant species. These findings suggest that environmental context plays an important role in determining whether and how soil biota generate the biodiversity–productivity relationship. Future studies would benefit from revealing the mechanisms underlying the interactive effects of soil biota, soil fertility, and plant diversity on ecosystem functioning.
Biodiversity and climate determine the functioning of Neotropical forests
Poorter, L. ; Sande, M.T. van der; Arets, E.J.M.M. ; Ascarrunz, N. ; Enquist, B.J. ; Finegan, B. ; Licona, J.C. ; Martinez-Ramos, M. ; Mazzei, L. ; Meave, J. ; Munoz, R. ; Nytch, C.J. ; Oliveira, A.A. de; Perez-Garcia, E.A. ; Prado-Junior, J.A. ; Rodriguez-Velazquez, J. ; Ruschel, A.R. ; Salgado Negret, B. ; Schiavini, I. ; Swenson, N.G. ; Tenorio, E.A. ; Thompson, J. ; Toledo, M. ; Uriarte, M. ; Hout, P. van der; Zimmerman, J.K. ; Pena Claros, M. - \ 2017
Wageningen University & Research
biodiversity - biomass - carbon - ecosystem functioning - forest dynamics - productivity - soil fertility - tropical forest - water
Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB), biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community-mean traits, and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). We used data from 26 sites, 201 one-ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community-weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Of the relationships analysed, vegetation attributes were more frequently significantly associated with biomass stocks and dynamics than environmental conditions (in 67% versus 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community-mean traits were good predictors of biomass stocks and dynamics. Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes – including species diversity and community-weighted mean traits – have independent and important relationships with AGB stocks, dynamics, and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper-diverse tropical forests.
Soil biota suppress positive plant diversity effects on productivity at high but not low soil fertility
Luo, Shan ; Deyn, Gerlinde B. De; Jiang, B. ; Yu, Shixiao - \ 2017
Journal of Ecology 105 (2017)6. - ISSN 0022-0477 - p. 1766 - 1774.
biodiversity effect - complementarity effect - plant diversity–productivity relationships - plant–microbe interactions - soil biota - soil fertility - subtropical forest
Plant community productivity commonly increases with increasing plant diversity, which is explained by complementarity among plant species in resource utilization (complementarity effect), or by selection of particularly productive plant species in diverse plant communities (selection effect). Recent studies have also shown that soil biota can drive the positive plant diversity–productivity relationship by suppressing productivity more in low- than in high-diversity plant communities. However, much remains unknown about whether soil fertility plays a role in determining how soil biota affect plant diversity–productivity relationships. We hypothesized that under high soil fertility conditions, negative soil biota effects dominate, which reduces plant monoculture biomass more than that of high-diversity plant communities. Conversely, under low soil fertility conditions, we hypothesized positive soil biota effects dominate, which facilitates plant resource partitioning and enhances community-level biomass in high-diversity plant communities. Hence, we expected positive plant diversity–community productivity relationships under low and high soil fertility conditions but caused by different mechanisms. We tested these hypotheses using woody seedlings and set up plant assemblages with four species richness levels (one, two, four and eight species), and grew them in sterilized and unsterilized (sterilized soil + living soil inoculum) soils at two nutrient levels (low versus high fertility). We found that at high fertility negative soil biota effects dominated and suppressed plant community biomass more in high-diversity plant communities than in monocultures, resulting in reduced complementarity effects of diverse plant communities and a non-significant plant species richness–community biomass relationship in unsterilized soil. Whereas at low fertility soil biota had net neutral to positive effects on plant community biomass but the beneficial effects did not increase with increasing plant species richness. Instead, soil biota neutrally affected the positive plant species richness–community biomass relationship, presumably due to non-specific effects of beneficial soil biota. Synthesis. Soil biota and soil fertility interactively determine plant species richness–community biomass relationships. Moreover, soil biota modulate the complementary resource use among plant species. These findings suggest that environmental context plays an important role in determining whether and how soil biota generate the biodiversity–productivity relationship. Future studies would benefit from revealing the mechanisms underlying the interactive effects of soil biota, soil fertility, and plant diversity on ecosystem functioning.
Agronomic and socioeconomic sustainability of farming systems : A case in Chencha, South Ethiopia
Dersseh, Waga Mazengia - \ 2017
Wageningen University. Promotor(en): P.C.. Struik, co-promotor(en): R.P.O. Schulte; D. Griffin. - Wageningen : Wageningen University - ISBN 9789463436830 - 157
potatoes - solanum tuberosum - ethiopia - food security - farming systems - mixed farming - sustainability - optimization - efficiency - farm surveys - household surveys - socioeconomics - self sufficiency - profits - training - agronomic characteristics - productivity - soil fertility - rotation - animal feeding - improved varieties - inorganic fertilizers - aardappelen - solanum tuberosum - ethiopië - voedselzekerheid - bedrijfssystemen - gemengde landbouw - duurzaamheid (sustainability) - optimalisatie - efficiëntie - bedrijfsonderzoeken - huishoudonderzoeken - sociale economie - zelfvoorziening - winsten - opleiding - agronomische kenmerken - productiviteit - bodemvruchtbaarheid - rotatie - diervoedering - veredelde rassen - anorganische meststoffen
Potato has multiple benefits and thus can play a vital role in ensuring food security in Ethiopia. However, for diverse reasons, its productivity is low. The farming systems in Ethiopia in which potato is grown, are predominantly mixed farming systems.
Most of the research in Ethiopia is focused on crop-specific constraints and thus there is limited research in which the interrelations between crop and livestock management practices are investigated. There is also not enough research focused on combined analysis of soil nutrient and animal feed balances and agronomic and socioeconomic efficiencies at farm level.
This study assessed production constraints and agronomic and socioeconomic sustainability of the farming systems in South Ethiopia and explored the possible synergetic options to alleviate major constraints. More specifically, the study intended to quantify the variation in input and output among farms, to identify constraints hindering expansion of potato production, to evaluate the sustainability of the farming systems at farm level, to identify constraints of sustainable intensification, and to explore synergetic solutions for the major constraints. Different research approaches were used ranging from lab analysis, household surveys, group discussions, to farm surveys.
Results showed that constraints related to input and product use in potato production vary across households indicating a need for a pluriform advisory model recognizing (and building upon alleviation of) the diversity of constraints identified in this analysis. The sustainability of the farming system is constrained by low agricultural productivity, low soil fertility, poor labour efficiency and limited economic return associated with improper crop rotation, inappropriate soil fertility management practices, shortage of animal feed, labour- and economically inefficient farm practices and labour shortage. However, there is ample scope to overcome the major constraints and simultaneously to optimize farm management.
The core messages of the study can be summarized as follows:
1) the current potato production is characterized by low productivity and economic returns due to various socioeconomic, agronomic and biological factors;
2) the soil fertility is low and there is uneven distribution of nutrients over plots with relatively high fertility levels in the homestead areas;
3) the current labour shortage can be attributed to mainly inefficiency of agricultural management practices and labour migration to towns for economic reasons indicating that the farming system is not sustainable in terms of labour;
4) considering the direct return from animal production, most of the farms had very low gross margin with the current management system and this reduced the overall operating profit of farms. The low return from animal rearing was offset by the relatively high profit from crop production indicating the benefit of mixed farming system in sustaining agricultural production; and
5) each farm can have a wide range of optimized solutions mainly through introduction of improved technologies and subsequent redesigning of the farm managements.
In general, the findings of the current study indicate that it is worthwhile to assess the sustainability of agricultural production in different farming systems and agro-ecologies of Ethiopia. In addition, the combined effect of introducing improved agricultural technologies and subsequent reconfiguring the farm management is very crucial to increase and sustain agricultural production.
On the role of soil organic matter for crop production in European arable farming
Hijbeek, Renske - \ 2017
Wageningen University. Promotor(en): M.K. van Ittersum, co-promotor(en): H.F.M. ten Berge. - Wageningen : Wageningen University - ISBN 9789463436632 - 211
soil fertility - soil fertility management - soil management - soil conservation - organic matter - soil organic matter - nitrogen - nitrogen fertilizers - green manures - manures - straw - soil carbon sequestration - cover crops - crop yield - yields - meta-analysis - food security - europe - drivers - barriers - bodemvruchtbaarheid - bodemvruchtbaarheidsbeheer - bodembeheer - bodembescherming - organische stof - organisch bodemmateriaal - stikstof - stikstofmeststoffen - groenbemesters - mest - stro - koolstofvastlegging in de bodem - dekgewassen - gewasopbrengst - opbrengsten - meta-analyse - voedselzekerheid - europa - chauffeurs - barrières
The aim of this thesis was to improve understanding of the role of organic inputs and soil organic matter (SOM) for crop production in contemporary arable farming in Europe. For this purpose, long-term experiments were analysed on the additional yield effect of organic inputs and savings in mineral fertiliser. In addition, a farm survey was conducted to find drivers and barriers for the use of organic inputs and to assess if arable farmers in Europe perceive a deficiency of SOM.
The findings in this thesis suggest that at least on the shorter term, on average, there seems to be no immediate threat from a deficiency of SOM to crop production in arable farming in Europe. The long-term experiments showed that with sufficient use of only mineral fertilisers, on average, similar yields could be attained over multiple years as with the combined use of organic inputs and mineral fertiliser. This was reflected in the farm survey, in which a large majority of farmers indicated not to perceive a deficiency of SOM. Analysis of long-term experiments also showed that more mineral fertiliser N was saved when using farmyard manure at high N rates (with mineral fertiliser application) than at low N rates (without mineral fertiliser application), based on comparisons at equal yield.
Specific crops and environments did benefit from organic inputs and more SOM in terms of crop production. Long-term experiments showed that organic inputs give benefit to crop production in wet climates and on sandy soils. In addition, farmers perceived a higher deficiency of SOM on steep slopes, sandy soils, wet and very dry climates. The additional yield effect of organic inputs was significant for potatoes. More in general, farmers who cultivated larger shares of their land with specialized crops (including potatoes, sugar beets, onions and other vegetables) than cereals perceived a higher deficiency of SOM. It seems that while the functions of SOM can be replaced with technical means to a large extent (e.g. tillage, use of mineral fertilisers), there are limits to this technical potential when environmental conditions are more extreme and crops are more demanding.
The farm survey revealed that farmers perceive a trade-off between improved soil quality on the one hand and increased pressures from weeds, pests and diseases and financial consequences on the other hand when using organic inputs. If policies aim to stimulate the maintenance or increase of SOM, more insight is needed into the conditions that regulate the pressures of weeds, pests and diseases in response to organic inputs. Financial consequences (at least on the short term) should also be accounted for. More importantly however, benefits from SOM for crop production cannot be taken for granted. Only in specific situations such benefits will exist. If European policies on SOM aim to include benefits for crop production, focus should be on areas with more extreme environmental conditions (very dry or wet climates, steep slopes, sandy soils), or cropping systems with more specialized or horticultural crops rather than cereals.
Species mixing effects on forest productivity in the Netherlands
Lu, Huicui - \ 2017
Wageningen University. Promotor(en): G.M.J. Mohren, co-promotor(en): F.J. Sterck. - Wageningen : Wageningen University - ISBN 9789463436397 - 134
mixed forests - temperate zones - deciduous forests - soil fertility - light - yields - netherlands - gemengde bossen - gematigde klimaatzones - loofverliezende bossen - bodemvruchtbaarheid - licht - opbrengsten - nederland
Many monoculture forests (dominated by a single tree species) have been converted to mixed-species forests (dominated by more than one tree species) in Europe over the last decades. The main reason for this conversion was to increase productivity, including timber production, and enhance other ecosystem services, such as conservation of biodiversity and other nature values. In addition, it has been suggested that mixed-species forests are more resistant, resilient and stable to disturbances.
In line with the niche complementarity hypothesis, inter-specific differences in crown architecture, leaf phenology, shade tolerance and root distribution may allow tree species to partition resources in mixed forests. Such mechanisms may lead to a higher productivity of mixed forests versus monoculture forests, a phenomenon often referred to as overyielding. Interestingly, the stress-gradient hypothesis and the resource-ratio hypothesis suggests that such inter-specific interactions vary along a soil fertility gradient, but in different ways. The stress-gradient hypothesis emphasizes that more efficient partitioning increases overyielding at low fertility soils, whereas the resource ratio hypothesis considers that the denser packing of crowns on fertile soils allows for partitioning of light and overyielding on high fertility soils. Several studies have been carried out about species mixing effects on forest productivity, but so far their findings are ambiguous. Probably, this ambiguity comes from the sites that they studied, which differ in species, age, management history, and/or environmental conditions.
This thesis analyses the mixing effect on productivity in relation to the combination of species, stand age and soil fertility, and discusses possible consequences of forest management, for five two-species mixtures in the Netherlands: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)–beech (Fagus sylvatica L.), pine (Pinus sylvestris L.)–oak (Quercus robur L.), oak–beech, oak–birch (Betula pendula Roth) and pine–birch. These mixtures and their corresponding monoculture stands were studied using long-term permanent forest plots over multiple decades, but also using two inventories (around 2003 and 2013) across the entire Netherlands. These forest plots data were used together with empirical models at total stand level (chapter 2), species level (chapter 3) and tree level (chapter 4) to evaluate the mixing effect on forest productivity.
In chapter 2, four two-species mixtures and their corresponding monospecific stands were compared for productivity (volume stem wood in m3 ha-1 year-1). It was explored whether mixing species differing in leaf phenology and shade tolerance would lead to overyielding of mixed forest stands, and whether overyielding changes with stand development. In line with the niche complementarity hypothesis, the two evergreen–deciduous species mixtures (Douglas-fir–beech and pine–oak) showed overyielding whereas deciduous–deciduous species mixtures (oak–beech and oak–birch) did not. The overyielding was strongest for the Douglas-fir–beech mixture than the pine–oak mixture, which can be attributed to the greater difference in shade tolerance in the former mixture. Overyielding did not significantly change with stand development. It is argued that the regular thinning maintained the ability of species to partition resources, i.e. the complementary resource use in those mixed stands over all stand ages.
In chapter 3, it was analysed which of the two species in these four mixtures contributed to overyielding, and whether this overyielding changed along a soil fertility gradient. It was discovered that both the fast-growing and the slow-growing species could contribute to overyielding. Yet, it was mainly the fast-growing Douglas-fir that contributed to higher productivity in the Douglas-fir–beech mixtures, and the slow-growing oak that did so in the pine–oak mixtures. For both mixtures, the greatest relative productivity gain was achieved by mixtures on the poorer soils. At first sight, these results seem in line with the stress-gradient hypothesis and not the resource-ratio hypothesis. Yet, it was argued that not only complementary use of soil resources, but also use of light, may contribute to the higher productivity of mixed stands on the poorer soils.
In chapter 4, it was assessed how the growth of individual trees in mixtures was influenced by inter- and intra-specific competition, and whether this competition was mainly size-symmetric for soil resources or size-asymmetric for light on soils differing in fertility. This chapter focussed on three mixtures, i.e. oak–birch, pine–oak and pine–birch, which were available at sufficient numbers in the Dutch national forest inventory data. It was concluded that intra-specific competition was not necessarily stronger than inter-specific competition and this competitive reduction was less seen at lower soil fertility and dependent on species mixtures, which is not in line with the stress-gradient hypothesis. Moreover, size-asymmetric competition for light was more associated with tree basal area growth than size-symmetric competition for soil resources, suggesting that light is the most limiting resource. Competition for light was generally much stronger at high fertility soils, supporting the resource-ratio hypothesis. These results suggest that light is the most limiting resource for tree basal area growth and that reduced competition for light can be explained to some degree by complementarity in light use to increase tree growth in mixed forests.
This thesis thus described the productivity patterns when mixing tree species and explored possible mechanisms of higher productivity in mixed stands compared with monoculture stands in the Netherlands. Complementary use of aboveground and belowground resources probably contributes to the higher productivity in mixed stands, but other factors including pathogens, nutrient cycling and litter decomposition were not addressed but cannot be excluded. Overyielding in Douglas-fir–beech and pine–oak mixtures was maintained over time, probably owing to the intensive thinning in Dutch forests. The results shed new light on the stress-gradient and resource-ratio hypotheses. For mixtures in Dutch forest, the greatest productivity gain in Douglas-fir–beech and pine–oak mixtures was achieved on the poorer soils, and it was argued that this is at least partially driven by complementary use of light, while the role of complementarity in use of soil resources is more obscure. Overall, this thesis suggest a substantial potential of species mixing for increasing productivity, which may run in parallel with enhancing other ecosystem services such as conservation of diversity and other nature values. Yet, more experimental studies on productivity in mixed stands are required to better unravel alternative mechanisms. Such understanding is required to manage the forests effectively in a century of unpreceded human driven changes in environmental conditions.
Soil fertility and species traits, but not diversity, drive productivity and biomass stocks in a Guyanese tropical rainforest
Sande, M.T. van der; Arets, E.J.M.M. ; Pena Claros, M. ; Hoosbeek, M.R. ; Caceres-Siani, Yasmani ; Hout, P. van der; Poorter, L. - \ 2017
Wageningen University & Research
biomass - soil fertility
In this study, we test the effects of abiotic factors (light variation, caused by logging disturbance, and soil fertility) and biotic factors (species richness and functional trait composition) on biomass stocks (aboveground biomass, fine root biomass), SOM and productivity in a relatively monodominant Guyanese tropical rainforest. This forest grows on nutrient-poor soils and has few species that contribute most to total abundance. We therefore expected strong effects of soil fertility and species’ traits that determine resource acquisition and conservation, but not of diversity. We evaluated 6 years of data for 30 0.4-ha plots and tested hypotheses using structural equation models. Our results indicate that light availability (through disturbance) and soil fertility – especially P – strongly limit forest biomass productivity and stocks in this Guyanese forest. Low P availability may cause strong environmental filtering, which in turn results in a small set of dominant species. As a result, community trait composition but not species richness determines productivity and stocks of biomass and SOM in tropical forest on poor soils.
'De plant voedt ook de bodem' : 'Inzicht in bodem-plantrelaties gunstig voor bodemvitaliteit en productkwaliteit'
Sukkel, W. - \ 2017
Ekoland 37 (2017)1. - ISSN 0926-9142 - p. 14 - 15.
bodem-plant relaties - biologische landbouw - groenbemesters - grondbewerking - bodemvruchtbaarheid - soil plant relationships - organic farming - green manures - tillage - soil fertility
Een belangrijk uitgangspunt van biologische landbouw is dat de bodem de plant voedt. Maar het omgekeerde is ook waar. Aandacht voor variatie in gewassen en groenbemesters kan de bodem helpen verbeteren. Het is een van de zaken waar WUR-onderzoekers tijdens de BioBeurs op inzoomen in een serie workshops over de bodem.
Data from: Conservative species drive biomass productivity in tropical dry forests
Prado-Junior, Jamir A. ; Schiavini, Ivan ; Vale, Vagner S. ; Sande, M.T. van der; Lohbeck, M.W.M. ; Poorter, L. - \ 2016
Wageningen University & Research
biodiversity-ecosystem functioning - biomass ratio hypothesis - carbon stocks and sequestration - community weighted mean traits - functional diversity - green soup hypothesis - niche complementarity - plant population and community dynamics - soil fertility
Data of above-ground biomass dynamics over a five-year period in eight seasonal tropical dry forests in Minas Gerais state, Southeastern Brazil. In each forest, 25 permanent sample plots (20 × 20 m) were established totaling one ha per site. Biomass dynamics, structural, floristic, functional and soil variables used in the biomass models are given. AGBi = stand biomass, AGBnet = net biomass change, AGBsurv = biomass growth of surviving trees, AGBmort = biomass mortality, AGBrecr = biomass recruitment, NI = tree-density (ha-1), CWM = community weighed mean, WD = wood density, Dmax = maximum stem diameter, SLA = specific leaf area, Dec = deciduousness, S = rarefied species richness, H’ = Shannon-Wiener index, J’ = Pielou’s index, Fric = functional richness, Feve = functional evenness, Fdiv = functional divergence, P = phosphorous, K = potassium, Ca = calcium, Mg = magnesium, Al = aluminum, CEC = cation exchange capacity.
Wisselteelt goed voor grasopbrengst : elf procent hogere grasopbrengst op De Marke dankzĳ vruchtwisseling met mais
Aarts, Frans - \ 2016
grasslands - yields - rotations - maize - soil fertility - grasses - fertilizer application - agricultural research
Wissel snĳmais af met minimaal drie jaar grasland. Dat advies geeft onderzoeker Frans Aarts van Wageningen UR. Verbetering van de bodemvruchtbaarheid leidt dan tot een hogere grasopbrengst, net als het gebruik van de nieuwste grassoorten.
De boon op de troon
Weele, Cor van der; Goot, Atze Jan van der; Giller, Ken ; Jager, Ilse de - \ 2016
food security - human feeding - beans - grain legumes - lentils - food consumption - protein sources - food and agriculture organization - meat alternates - soil fertility - pisum sativum
Geinterviewd voor artikel in Wageningen World Nr.3 2016 In het kader van het Internationaal jaar van de peulvruchten.
Leve(n) de bodem! : de basis onder ons bestaan
Brussaard, L. ; Govers, F.P.M. ; Buiter, R.M. - \ 2016
Den Haag : Stichting Bio-Wetenschappen en Maatschappij (Cahier / Biowetenschappen en Maatschappij 35e jaargang (2016) kwartaal 3) - ISBN 9789073196834 - 88
bodemkunde - bodembiologie - bodemkwaliteit - landbouwgronden - bodemvruchtbaarheid - bodembeheer - bodemweerbaarheid - bodemmicrobiologie - duurzaam bodemgebruik - lesmaterialen - soil science - soil biology - soil quality - agricultural soils - soil fertility - soil management - soil suppressiveness - soil microbiology - sustainable land use - teaching materials
De bodem is niet alleen letterlijk de grond onder ons bestaan, ze is dat ook figuurlijk. Vruchtbare bodems leveren ons bijvoorbeeld voedsel, water en grondstoffen, maar ook een heel scala aan andere ecosysteemdiensten. In één theelepel zwarte grond leven meer organismen dan er mensen zijn op de hele aarde. Ze zorgen ervoor dat planten gebruik kunnen maken van de voedingsstoffen in de bodem en in een gezonde bodem krijgen ziekteverwekkers ook minder kans. Nu we steeds beter begrijpen hóe ze dat doen, kunnen wij zelfs nieuwe antibiotica vinden in de bodem! In dit cahier laten wetenschappers van naam op het gebied van het bodemonderzoek niet alleen zien welke diensten een gezonde bodem al vele eeuwen levert. Ze vertellen ook hoe de figuurlijke bodem onder ons bestaan tegelijk grond voor inspiratie is voor voedsel en technologie voor de toekomst.
Bodemverbeteraars met focus op biochar
Reuler, H. van; Baltissen, A.H.M.C. - \ 2016
bodemverbeteraars - biochar - bodemkwaliteit - bodemvruchtbaarheid - bodembiologie - soil conditioners - biochar - soil quality - soil fertility - soil biology
Biochar is een stabiele organische verbinding die hoofdzakelijk uit koolstof bestaat. Het ontstaat bij verhitting van biomassa onder zuurstofloze omstandigheden, z.g. pyrolyse. Biochar wordt geproduceerd als bodemverbeteraar. De discussie gaat om het effect van Biochar toediening op een aantal bodemfuncties, zoals b.v. het vermogen om vocht en voedingsstoffen vast te houden, biologische activiteit.
Biomass resilience of Neotropical secondary forests
Poorter, L. ; Bongers, F. ; Aide, T.M. ; Almeyda Zambrano, A.M. ; Balvanera, P. ; Becknell, J.M. ; Boukill, V. ; Brancalion, P.H.S. ; Jakovac, A.C. ; Braga Junqueira, A. ; Lohbeck, M.W.M. ; Pena Claros, M. ; Rozendaal, Danae - \ 2016
biomass - tropical forest - secondary succession - neotropics - rainfall - land use - soil fertility - carbon - mitigation
Land-use change occurs nowhere more rapidly than in the tropics, where the imbalance between deforestation and forest regrowth has large consequences for the global carbon cycle1. However, considerable uncertainty remains about the rate of biomass recovery in secondary forests, and how these rates are influenced by climate, landscape, and prior land use2, 3, 4. Here we analyse aboveground biomass recovery during secondary succession in 45 forest sites and about 1,500 forest plots covering the major environmental gradients in the Neotropics. The studied secondary forests are highly productive and resilient. Aboveground biomass recovery after 20 years was on average 122 megagrams per hectare (Mg ha−1), corresponding to a net carbon uptake of 3.05 Mg C ha−1 yr−1, 11 times the uptake rate of old-growth forests. Aboveground biomass stocks took a median time of 66 years to recover to 90% of old-growth values. Aboveground biomass recovery after 20 years varied 11.3-fold (from 20 to 225 Mg ha−1) across sites, and this recovery increased with water availability (higher local rainfall and lower climatic water deficit). We present a biomass recovery map of Latin America, which illustrates geographical and climatic variation in carbon sequestration potential during forest regrowth. The map will support policies to minimize forest loss in areas where biomass resilience is naturally low (such as seasonally dry forest regions) and promote forest regeneration and restoration in humid tropical lowland areas with high biomass resilience.