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1.
Grazing‐induced degradation of grasslands is the primary impediment to the socioeconomic development of Inner Mongolia. It affects the entire environment of northern China. Understanding grassland dynamics is necessary for restoration and sustainable management of these degraded ecosystems. The recovery dynamics of a degraded Leymus chinensis (Trin.) Tzvel. grassland after removal of grazing was studied in comparison with its spatial variation along a grazing gradient, using its climax community as a benchmark. The species composition, diversity, and biomass of the grassland vegetation, as well as the attributes (height, density, and individual mass) of major species, were examined on the eight sites along the grazing gradient and in the recovering grassland over 11 years. The spatial pattern of grassland vegetation along the grazing gradient closely reflected its recovery trajectory over time. Both the spatial and the temporal processes exhibited the same shift in species dominance in association with grazing removal or less grazing intensity. Grassland degradation was accompanied by an increase in species density and a decrease in species size; this trend was reversed during recovery. This result suggested that the degraded grassland is highly resilient and that restoration could occur naturally by reducing or excluding grazing animals. However, some differences existed between the spatial and the temporal processes. Species richness was high on the light‐ or no‐grazing sites along the gradient, but varied little during the recovery of the degraded grassland. Species evenness was high under moderate to light grazing along the gradient and was high at the beginning of the recovery period but not at the end. Although standing biomass improved significantly during the recovery period, it did not change significantly along the grazing gradient. These observed discrepancies were related to the intrinsic difference in the spatial versus temporal processes and are discussed together with the advantage/disadvantage of the grazing gradient versus dynamic monitoring methods in grassland dynamics studies. 相似文献
2.
The stratified distribution of soil organic carbon (SOC) provides a potential means of eliminating the difference in soil background for understanding its response to ecological processes. We assessed the feasibility of SOC stratification ratio (SR) as an index to estimate the dynamics of SOC sequestration and soil quality during ecological restoration. SOC, total nitrogen, and available nitrogen contents were measured at restored sites containing three vegetation types with different stand ages and slope gradients, also at sites with three kinds of agricultural management on the hilly Loess Plateau, China. SR and SOC density (SOCD) showed a consistently significant trend of linear increase along the revegetation chronosequences. The proportion of the annual increase rates of SR to SOCD were approximately 1:15 and 1:5 for SR1 (0–5:5–10 cm) and SR2 (0–5:20–30 cm), indicating that SR of the shallow soil layers (0–10 cm) could estimate SOC accumulation to a depth of 30 cm. SRs significantly increased owing to the ecosystem restorations. Also, SRs could discriminate the difference in SOC sequestration and soil quality between vegetation types. SR, however, could not precisely indicate the variation of SOC sequestration and soil quality under different agricultural management. The study suggested that SR was an efficient indicator of the dynamics of SOC sequestration and soil quality, and an SR2 (0–5:20–30 cm) >2 indicated a distinct improvement of SOC sequestration and soil quality in ecological restoration on the hilly Loess Plateau. 相似文献
3.
The effects of stock grazing on native grassy ecosystems in temperate southern Australia are well documented. However, less is known about the potential of ecosystems to recover after a long history of stock grazing and, in particular, whether the removal of stock will have positive, negative or neutral impacts on biodiversity. We examined the response of understorey vegetation to the removal of sheep grazing in a herb‐rich Eucalyptus camaldulensis (red gum) woodland in western Victoria. Using a space‐for‐time chronosequence, woodlands were stratified into groups based on their time‐since‐grazing removal; these were long‐ungrazed (>20 years), intermediate‐time‐since‐grazing (9–14 years), recently ungrazed (5 years) and continuously grazed. We found significantly higher species density in long‐ungrazed sites relative to sites with a more recent grazing history. No differences were found in species density between continuously grazed sites and those ungrazed in the previous 14 years. Species composition differed with time‐since‐grazing removal and indicator species analysis detected several native species (including tall native geophytes and herbs) associated with long‐ungrazed sites that were absent or in low abundance in the more recently grazed sites. Seven of the eight species significantly associated with continuously grazed sites were exotic. Removal of sheep grazing in red gum woodlands can have positive benefits for understorey diversity but it is likely that recovery of key indicators such as native species will be slow. 相似文献
4.
5.
Lizanne Janssens Khuong Dinh Van Sara Debecker Lieven Bervoets Robby Stoks 《Evolutionary Applications》2014,7(3):421-430
The ability to deal with temperature‐induced changes in interactions with contaminants and predators under global warming is one of the outstanding, applied evolutionary questions. For this, it is crucial to understand how contaminants will affect activity levels, predator avoidance and antipredator responses under global warming and to what extent gradual thermal evolution may mitigate these effects. Using a space‐for‐time substitution approach, we assessed the potential for gradual thermal evolution shaping activity (mobility and foraging), predator avoidance and antipredator responses when Ischnura elegans damselfly larvae were exposed to zinc in a common‐garden warming experiment at the mean summer water temperatures of shallow water bodies at southern and northern latitudes (24 and 20°C, respectively). Zinc reduced mobility and foraging, predator avoidance and escape swimming speed. Importantly, high‐latitude populations showed stronger zinc‐induced reductions in escape swimming speed at both temperatures, and in activity levels at the high temperature. The latter indicates that local thermal adaptation may strongly change the ecological impact of contaminants under global warming. Our study underscores the critical importance of considering local adaptation along natural gradients when integrating biotic interactions in ecological risk assessment, and the potential of gradual thermal evolution mitigating the effects of warming on the vulnerability to contaminants. 相似文献
6.
Liisa Nevalainen Marttiina V. Rantala Milla Rautio Tomi P. Luoto 《Journal of Biogeography》2018,45(8):1954-1965
7.
1. The organic matter dynamics of streams dominated by herbs and grass on their banks are poorly understood, despite the fact that such streams are common worldwide. Further, herbs and grasses can provide large quantities of detritus to stream food webs, and particularly small streams can be heavily shaded by overhanging vegetation, perhaps limiting in‐stream primary production. 2. We quantified the standing crop of edge vegetation and associated macroinvertebrate communities along three headwater streams with herbaceous and grass riparian vegetation on agricultural land in the Piedmont of Maryland, U.S.A., measured the decomposition of four common species of herbs and grasses using experimental leaf packs, and removed edge vegetation experimentally to determine the effect of shading on benthic algal production. 3. Large standing crops of plant material (average range: 68–276 g ash‐free dry mass per m−2), composed largely of monocotyledons, were found at all three study streams. These values are similar to those for coarse particulate organic matter in deciduous forested streams in the eastern U.S.A. In addition, diverse assemblages of shredding macroinvertebrates were observed at all three study sites. 4. Decomposition of the herbs was faster than that of the grasses, and both decomposed faster than most deciduous tree leaf litter. The decomposition rates of the herbs and grasses were significantly related to leaf quality as measured by leaf nitrogen content. Macroinvertebrate shredders colonized all experimental leaf packs, and the colonization of the herbs was faster than that of the grasses. 5. The accrual of chlorophyll‐a after the removal of shading vegetation was faster than that measured prior to removal as well as that in an unmanipulated control reach. 6. Given that the standing crop of organic matter in streams with herbs and grass along their banks was similar to that in forested streams, that the organic matter was rich in nitrogen and used by detritivores, and riparian shading limited algal growth, we suggest that herbaceous and grass plant material may be an important allochthonous food resource in such systems. 相似文献
8.
Nutrient and mineralogical control on dissolved organic C, N and P fluxes and stoichiometry in Hawaiian soils 总被引：4，自引：2，他引：4
We measured DOM fluxes from the O horizon of Hawaiiansoils that varied in nutrient availability and mineralcontent to examine what regulates the flux ofdissolved organic carbon (DOC), nitrogen (DON) andphosphorus (DOP) from the surface layer of tropicalsoils. We examined DOM fluxes in a laboratory study from N, P and N+Pfertilized and unfertilized sites on soils that rangedin age from 300 to 4 million years old. The fluxesof DOC and DON were generally related to the % Cand % N content of the soils across the sites. Ingeneral, CO2 and DOC fluxes were not correlatedsuggesting that physical desorption, dissolution andsorption reactions primarily control DOM release fromthese surface horizons. The one exception to thispattern was at the oldest site where there was asignificant relationship between DOC and CO2flux. The oldest site also contained the lowestmineral and allophane content of the three sites andthe DOC-respiration correlation indicates arelationship between microbial activity and DOC fluxat this site. N Fertilization increased DON fluxes by50% and decreased DOC:DON ratios in the youngest,most N poor site. In the older, more N rich sites, Nfertilization neither increased DON fluxes nordecreased DOM C:N ratios. Similarly, short termchanges in N availability in laboratory-based soil Nand P fertilization experiments did not affect the DOMC:N ratios of leachate. DOM C:N ratios were similar tosoil organic matter C:N ratios, and changes in DOM C:Nratios with fertilization appeared to have beenmediated through long term effects on SOM C:N ratiosrather than through changes in microbial demand for Cand N. There was no relationship between DON andinorganic N flux during these incubations suggestingthat the organic and inorganic components of N fluxfrom soils are regulated by different factors and thatDON fluxes are not coupled to immediate microbialdemand for N. In contrast to the behavior of DON, thenet flux of dissolved organic phosphorus (DOP) and DOMC:P ratios responded to both long-term P fertilizationand natural variation in reactive P availability. There was lower DOP flux and higher DOM C:P ratiosfrom soils characterized by low P availability andhigh DOP flux and narrow DOM C:P ratios in sites withhigh P availability. DOP fluxes were also closelycorrelated with dissolved inorganic P fluxes. PFertilization increased DOP fluxes by 73% in theyoungest site, 31% in the P rich intermediate agesite and 444% in the old, P poor site indicating thatDOP fluxes closely track P availability in soils. 相似文献
9.
以闽江河口湿地为研究对象,沿自然盐度梯度分别采集不同盐度区的短叶茳芏湿地(有植被)和光滩(无植被)土壤样品,对不同盐度条件下土壤理化性质、植物生物量及土壤磷形态等进行研究,以评估盐度增加对湿地土壤磷形态变化的影响及其调控因子。结果表明:①不同盐度条件下,土壤全磷和各形态磷含量大体表现为短叶茳芏湿地高于无植被的光滩,尤其在淡水条件下最为显著。总体上,随盐度增加,土壤全磷和有机磷含量逐渐减低,无机磷和氢氧化钠磷含量表现为先降低后增加,而盐酸磷含量则逐渐增加。无机磷是闽江河口不同盐度湿地土壤全磷的主要赋存形态,分别占全磷的74%、77%和83%,占比随盐度增加而增大。②不同植被条件下,短叶茳芏湿地土壤全碳、全氮含量和氮磷比均显著高于光滩土壤(P < 0.05)。不同盐度条件下,淡水区土壤全碳、全氮含量和碳氮比均显著高于咸水湿地,并且高盐区大于中盐区(P < 0.05)。③地上和地下植物生物量沿盐度梯度呈现明显不同的趋势,地上生物量表现为随盐度增加而增大,地下生物量在淡水区高于咸水区,尤其是显著高于中等盐度区。④相关分析显示,盐度及其关联的地上/地下生物量、全碳、全氮和有机质含量等的变化共同调控了土壤磷形态和有效性的变化。研究表明,滨海河口湿地盐度的增加通过改变土壤有机质含量和地上/地下植物生物量,调控了土壤磷的形态和转化,进而影响湿地生态系统的养分循环和化学计量平衡。 相似文献
10.
时空转换最初是研究植物群落演替的方法,目前作为一种理论推断在社会科学、地理信息和地质分析等领域应用,在昆虫生态学中的应用很少,本文介绍了空间换取时间与时间换取空间两种方法,能够巧妙地缩短很多昆虫生态学的试验时间,或增加研究范围内的样本数,在大尺度景观研究昆虫迁移、预测预报、栖境恢复等方面具有重要意义。这种时空转换的技巧在昆虫生态学的研究的有广阔的应用前景。 相似文献
11.
Loss-on-ignition estimates of organic matter and relationships to organic carbon in fluvial bed sediments 总被引：5，自引：0，他引：5
Fluvial bed sediments represent an important sink and source for a variety of organic and inorganic compounds. Their most
important constituent is organic matter (OM) and its primary component organic carbon (OC). Few studies have been conducted
in fluvial environments examining bed-associated OM or OC. This is surprising given the recent interest in global carbon cycling
and the importance of bed-associated organics as ecosystem energy sources. The objective of this study was to examine the
relationship between OM, determined by loss-on-ignition (LOI), and OC in fluvial bed sediments determined by a dry combustion
analyzer. The wide adoption of the LOI method in soil science reflects its ease of use, it is inexpensive, it is rapid, requires
no specialized training, and strong statistical relationships commonly exist between OM and OC estimated by standard dry combustion
procedures. Regression models were developed between OC and OM for six bed sediment size fractions (≤2.0 mm) for 113 sample
sites in a tropical stream on Oahu, Hawaii. All models were highly significant (p < 0.0001), with coefficients of determination
ranging from 35 to 79%. Measurement of LOI explained 64% of the variation in OC for all grouped data. The black-box LOI approach
may be useful for rapid reconnaissance surveys of drainage systems. Examination of OM to OC conversion factors for Manoa bed
sediments indicates that values typically observed in the soils literature (1.7–2.2) are far too low. Values of OM/OC were
found to increase with increasing grain size, and decrease with increasing LOI percentage. Conversion factors obtained for
grouped data had a mean of 14.9, a coefficient of variation of 21%, and a range of values between 6.2 and 27.4. It is suggested
that these high conversion factors reflect significant water loss by dehydration of Fe, Al, and Mn oxides at a muffle furnace
temperature of 450 °C. Therefore, the blind application of conversion factors developed from soils should be avoided when
converting from OM to OC for fluvial bed sediments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Nathlia Vieira Hissa Safar Luiz Fernando Silva Magnago Samir Gonalves Rolim Carlos Ernesto Gonalves Reynauld Schaefer 《Biotropica》2019,51(3):342-354
Human impacts can affect the soil properties through erosion and leaching, the ecosystem functions and, consequently, the capacity of a forest to regenerate. Here, we determine the effects of forest disturbance and succession on selected soil chemical properties using two different approaches, before‐after‐control‐impact (BACI) and space‐for‐time (SFT) substitution, and the threatened Atlantic Forest biome as model. We assessed with BACI the long‐term (37‐year) effects of clear cutting on soil properties by comparing data from two topsoil surveys (1978–2017) divided into two treatments: a preserved old growth forest (control) and an adjacent forest that was experimentally cleared with full tree removal (clear‐cut). We examined with SFT the relationship between stand age and soil properties using soil data from three old growth and 13 s growth forests ranging from 7 to 33 years. We found no significant differences between treatments for any soil property or significant changes in phosphorus, potassium, and calcium + magnesium over time. In contrast, pH increased and aluminum decreased in both areas. No relation was found between forest age and most of soil properties, with the exception of potassium which returned to old growth forest levels after 20 years of natural succession, and pH. BACI indicated that deforestation of old growth forest caused no significant effects on soil chemical properties after 37 years of regeneration. SFT demonstrated that soil properties did not change significantly during forest regeneration on formerly disturbed lands. Our findings indicate that natural nutrient‐depleted lowland forests were overall resistant to deforestation followed by passive regeneration at landscape scale. Abstract in Portuguese is available with online material. 相似文献
13.
L. Arriana Brand Juliet C. Stromberg David C. Goodrich Mark D. Dixon Kevin Lansey Doosun Kang David S. Brookshire David J. Cerasale 《Ecohydrology》2011,4(1):130-142
Groundwater is a key driver of riparian condition on dryland rivers but is in high demand for municipal, industrial, and agricultural uses. Approaches are needed to guide decisions that balance human water needs while conserving riparian ecosystems. We developed a space‐for‐time substitution model that links groundwater change scenarios implemented within a Decision Support System (DSS) with proportions of floodplain vegetation types and abundances of breeding and migratory birds along the upper San Pedro River, AZ, USA. We investigated nine scenarios ranging from groundwater depletion to recharge. In groundwater decline scenarios, relative proportions of tall‐canopied obligate phreatophytes (Populus/Salix, cottonwood/willow) on the floodplain progressively decline, and shrubbier species less dependent on permanent water sources (e.g. Tamarix spp., saltcedar) increase. These scenarios result in broad shifts in the composition of the breeding bird community, with canopy‐nesting and water‐obligate birds declining but midstory nesting birds increasing in abundance as groundwater declines. For the most extreme draw‐down scenario where all reaches undergo groundwater declines, models project that only 10% of the upper San Pedro floodplain would be comprised of cottonwood/willow (73% saltcedar and 18% mesquite), and abundances of canopy‐nesting, water‐obligate, and spring migrant birds would decline 48%, 72%, and 40%, respectively. Groundwater recharge scenarios were associated with increases in canopy‐nesting birds particularly given the extreme recharge scenario (all reaches regain shallow water tables and perennial streamflow). Model outputs serve to assess the sensitivity of biotic groups to potential changes in groundwater and thus to rank scenarios based on their expected ecological impacts. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Substantial differences in littoral fish community structure and dynamics in subtropical and temperate shallow lakes 总被引：5，自引：0，他引：5
FRANCO TEIXEIRA-de MELLO MARIANA MEERHOFF ZEYNEP PEKCAN-HEKIM ERIK JEPPESEN 《Freshwater Biology》2009,54(6):1202-1215
1. Fish play a key role in the functioning of temperate shallow lakes by affecting nutrient exchange among habitats as well as lake trophic structure and dynamics. These processes are, in turn, strongly influenced by the abundance of submerged macrophytes, because piscivorous fish are often abundant at high macrophyte density. Whether this applies to warmer climates as well is virtually unknown. 2. To compare fish community structure and dynamics in plant beds between subtropical and temperate shallow lakes we conducted experiments with artificial submerged and free‐floating plant beds in a set of 10 shallow lakes in Uruguay (30°–35°S) and Denmark (55°–57°N), paired along a gradient of limnological characteristics. 3. The differences between regions were more pronounced than differences attributable to trophic state. The subtropical littoral fish communities were characterised by higher species richness, higher densities, higher biomass, higher trophic diversity (with predominance of omnivores and lack of true piscivores) and smaller body size than in the comparable temperate lakes. On average, fish densities were 93 ind. m−2 (±10 SE) in the subtropical and 10 ind. m−2 (±2 SE) in the temperate lakes. We found a twofold higher total fish biomass per unit of total phosphorus in the subtropical than in the temperate lakes, and as fish size is smaller in the former, the implication is that more energy reaches the littoral zone fish community of the warmer lakes. 4. Plant architecture affected the spatial distribution of fish within each climate zone. Thus, in the temperate zone fish exhibited higher densities among the artificial free‐floating plants while subtropical fish were denser in the artificial submerged plant beds. These patterns appeared in most lakes, regardless of water turbidity or trophic state. 5. The subtropical littoral fish communities resembled the fish communities typically occurring in temperate eutrophic and hypertrophic lakes. Our results add to the growing evidence that climate warming may lead to more complex and omnivory‐dominated food webs and higher density and dominance of smaller‐sized fish. This type of community structure may lead to a weakening of the trophic cascading effects commonly observed in temperate shallow lakes and a higher risk of eutrophication. 相似文献
15.
Packs of autumn-shed maple leaves were placed at coal ash effluent-exposed and reference sites in streams on December 5, 1977 and removed after 27 and 96 days. Leaf surface area (cm2/leaf) and disc weight (ash-free dry wt/15 mm disc) were greater at the effluent-exposed site than at the reference site after 96 days (p < .001). ATP content of leaves from the reference stream quadrupled between 27 and 96 days while ATP content of effluent-exposed leaves remained low. Macroinvertebrates colonized the leaf packs in the reference site but were not found on or in effluent-exposed packs. We concluded that leaf processing beyond the leaching of soluble organics did not occur in the effluent-exposed packs owing to reduced colonization and decomposition by fungi. Since stream invertebrates prefer decomposed leaf material and animals grow faster on leaves colonized by microbes, the ash effuent appears to indirectly affect macroinvertebrates by interfering with leaf decomposition and thus reducing the quality of their food. 相似文献
16.
Matthew D. Waterhouse Liesl P. Erb Erik A. Beever Michael A. Russello 《Molecular ecology》2018,27(11):2512-2528
The ecological effects of climate change have been shown in most major taxonomic groups; however, the evolutionary consequences are less well‐documented. Adaptation to new climatic conditions offers a potential long‐term mechanism for species to maintain viability in rapidly changing environments, but mammalian examples remain scarce. The American pika (Ochotona princeps) has been impacted by recent climate‐associated extirpations and range‐wide reductions in population sizes, establishing it as a sentinel mammalian species for climate change. To investigate evidence for local adaptation and reconstruct patterns of genomic diversity and gene flow across rapidly changing environments, we used a space‐for‐time design and restriction site‐associated DNA sequencing to genotype American pikas along two steep elevational gradients at 30,966 SNPs and employed independent outlier detection methods that scanned for genotype‐environment associations. We identified 338 outlier SNPs detected by two separate analyses and/or replicated in both transects, several of which were annotated to genes involved in metabolic function and oxygen transport. Additionally, we found evidence of directional gene flow primarily downslope from high‐elevation populations, along with reduced gene flow at outlier loci. If this trend continues, elevational range contractions in American pikas will likely be from local extirpation rather than upward movement of low‐elevation individuals; this, in turn, could limit the potential for adaptation within this landscape. These findings are of particular relevance for future conservation and management of American pikas and other elevationally restricted, thermally sensitive species. 相似文献
17.
利用吉林桦甸连续3年的田间试验结果,结合气象观测资料,对春玉米群体叶面积指数动态特征及不同产量水平下的生态因子资源量的分配特点进行了研究.结果表明：以相对生长天数、相对有效积温、相对日照时数和相对降雨量为自变量的相对叶面积指数动态模型均符合有理方程：y=（a+bx）/（1+cx+dx2）;产量（y）与吐丝前后生长天数比值（x1）、吐丝前后有效积温比值（x2）、吐丝前后降雨量比值（x3）以及吐丝前后日照时数比值（x4）的回归方程为y=5465.19+17810.64x1-23236.14x2+4093.41x3+6287.37x4(R2=0.8187,P<0.01),各生态因子对产量的影响按照偏回归系数绝对值排序为x1>x2>x3>x4;超高产（15499.86 kg·hm-2）生态因子资源量在吐丝前与吐丝后的比值分别为：生长天数1.43、有效积温1.41、降雨量1.44、日照时数1.40.在东北地区,适期早播,在延长总生长天数的前提下适当增加吐丝前的生长天数、降雨量以及日照时数均能提高产量,当生长天数、有效积温、降雨量以及日照时数在吐丝前与吐丝后的分配比值均约为1.4时,可获得高产、超高产. 相似文献
18.
Sara Debecker Maarten De Jonge Philippe Lambret Viktor Nilsson‐Örtman Lieven Bervoets Robby Stoks 《Global Change Biology》2013,19(9):2625-2633
Global warming and contamination represent two major threats to biodiversity that have the potential to interact synergistically. There is the potential for gradual local thermal adaptation and dispersal to higher latitudes to mitigate the susceptibility of organisms to contaminants and global warming at high latitudes. Here, we applied a space‐for‐time substitution approach to study the thermal dependence of the susceptibility of Ischnura elegans damselfly larvae to zinc in a common garden warming experiment (20 and 24 °C) with replicated populations from three latitudes spanning >1500 km in Europe. We observed a striking latitude‐specific effect of temperature on the zinc‐induced mortality pattern; local thermal adaptation along the latitudinal gradient made Swedish, but not French, damselfly larvae more susceptible to zinc at 24 °C. Latitude‐ and temperature‐specific differences in zinc susceptibility may be related to the amount of energy available to defend against and repair damage since Swedish larvae showed a much stronger zinc‐induced reduction of food intake at 24 °C. The pattern of local thermal adaptation indicates that the predicted temperature increase of 4 °C by 2100 will strongly magnify the impact of a contaminant such as zinc at higher latitudes unless there is thermal evolution and/or migration of lower latitude genotypes. Our results underscore the critical importance of studying the susceptibility to contaminants under realistic warming scenarios taking into account local thermal adaptation across natural temperature gradients. 相似文献
19.
Sustainable crop production is dependent on improvement of soil health using different management strategies. A study was conducted in the 2008/09 cropping season to investigate soil macrofauna order diversity and abundance under organic matter transfer system and improved fallows in a high rainfall (>800 mm year?1) area of Zimbabwe. Macrofauna were sampled using monoliths to a depth of 25 cm and Shannon‐Wiener diversity was used for diversity testing. Order diversity varied significantly with treatment under both systems. Under improved fallows, Leucaena trichandra had the highest fauna orders (6) followed by Calliandra colorthysus (5), then Acacia anguistissima (4) while Leucaena pallida and miombo forest had the least orders. Crotalaria juncea had the highest faunal orders (5), among organic material transfer system while other treatments had ≥3 orders. Unfertilized maize had one order. Calliandra colorthysus had the highest order diversity followed by maize stover > cattle manure > Cr. juncea > fully fertilized maize > unfertilized maize. Major groups identified were termites, earthworms, beetles, millipedes and ants. All taxa combined, cattle manure and miombo forest had the highest macrofauna abundance. This study showed that application of organic nutrient resources and use of improved fallows significantly influenced soil macrofauna order diversity and abundance. 相似文献
20.
Managed adaptation could reduce the risks of climate change to the world's ecosystems, but there have been surprisingly few practical evaluations of the options available. For example, riparian woodland is advocated widely as shade to reduce warming in temperate streams, but few studies have considered collateral effects on species composition or ecosystem functions. Here, we use cross‐sectional analyses at two scales (region and within streams) to investigate whether four types of riparian management, including those proposed to reduce potential climate change impacts, might also affect the composition, functional character, dynamics and energetic resourcing of macroinvertebrates in upland Welsh streams (UK). Riparian land use across the region had only small effects on invertebrate taxonomic composition, while stable isotope data showed how energetic resources assimilated by macroinvertebrates in all functional guilds were split roughly 50:50 between terrestrial and aquatic origins irrespective of riparian management. Nevertheless, streams draining the most extensive deciduous woodland had the greatest stocks of coarse particulate matter (CPOM) and greater numbers of ‘shredding’ detritivores. Stream‐scale investigations showed that macroinvertebrate biomass in deciduous woodland streams was around twice that in moorland streams, and lowest of all in streams draining non‐native conifers. The unexpected absence of contrasting terrestrial signals in the isotopic data implies that factors other than local land use affect the relative incorporation of allochthonous subsidies into riverine food webs. Nevertheless, our results reveal how planting deciduous riparian trees along temperate headwaters as an adaptation to climate change can modify macroinvertebrate function, increase biomass and potentially enhance resilience by increasing basal resources where cover is extensive (>60 m riparian width). We advocate greater urgency in efforts to understand the ecosystem consequences of climate change adaptation to guide future actions. 相似文献