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Earthworms are known to play a role in aggregate formation and soil organic matter (SOM) protection. However, it is still unclear at what scale and how quickly earthworms manage to protect SOM. We investigated the effects of Aporrectodea caliginosa on aggregation and aggregate-associated C pools using 13C-labeled sorghum (Sorghum bicolor (L.) Moench) leaf residue. Two incubations were set up. The first incubation consisted of soil samples crushed <250 μm to break up all macroaggregates with three treatments: (i) control soil; (ii) soil+13C-labeled residue and (iii) soil+13C-labeled residue+earthworms. Earthworms were added after 8 d and 12 d (days) later, aggregate size distribution was measured together with total C and 13C in each aggregate fraction. A second incubation was made to assay protected versus unprotected total C and 13C from 21-d laboratory incubations of intact and crushed large (>2000 μm) and small (250-2000 μm) macroaggregates and microaggregates (53-250 μm). Eight different pools of aggregate-associated C were quantified: (1) and (2) unprotected C pools in large and small macroaggregates, (3) unprotected C pools in microaggregates, (4) and (5) protected C pools in large and small macroaggregates, (6) protected C pool in microaggregates, and (7) and (8) protected C pools in microaggregates within large and small macroaggregates. In the presence of earthworms, a higher proportion of large macroaggregates was newly formed and these aggregates contained more C and 13C compared to bulk soil. There were no significant differences between the samples with or without earthworms in the C pool-sizes protected by macroaggregates, microaggregates or microaggregates within small macroaggregates. However, in the presence of earthworms, the C protected by microaggregates within large macroaggregates was a significant pool and 22% of this C pool was newly added C. In conclusion, these results clearly indicate the direct involvement of earthworms in providing protection of soil C in microaggregates within large macroaggregates leading to a possible long-term stabilization of soil C. 相似文献
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Heleen C. Druce 《Biological conservation》2008,141(12):3127-3138
Continuous human population expansion pressure on conservation ecosystems restricts wildlife areas, and necessitates active management. In areas of changing land-use and increasing human-animal conflict, responses of wildlife to direct human interventions can inform managers and planners. During August 2004, the boundary fences between Phinda Private Game Reserve and two neighbouring reserves were removed. This study examined behavioural responses of the resident elephants. Older, recently introduced bulls moved into the new area during the first month after fence removal, while younger resident bulls and family groups took between five and eight months. Initially family groups only moved into the new area at night and spent minimal time there, while older bulls spent longer periods of time, regardless of time of day. One year after fence removal, most of the elephants had only expanded their home ranges slightly into the new area. One of the findings of this study is that elephants appear to act cautiously in exploring new areas and responded by moving into the area slowly and over a relatively long time period. This cautious behaviour reduced through time as animals became more familiar with the area. The spatial scale of response of the elephants was relatively small, while the temporal scale of response was relatively large. 相似文献
3.
Stand age and fine root biomass, distribution and morphology in a Norway spruce chronosequence in southeast Norway 总被引：1，自引：0，他引：1
We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a depth of 60 cm. Fine root morphological characteristics, such as specific root length (SRL), root length density (RLD), root surface area (RSA), root tip number and branching frequency (per unit root length or mass), were determined based on digitized root data. Fine root biomass and morphological characteristics related to biomass (RLD and RSA) followed the same tendency with chronosequence and were significantly higher in the 30-year-old stand and lower in the 10-year-old stand than in the other stands. Among stands, mean fine root (< 2 mm) biomass ranged from 49 to 398 g m(-2), SLR from 13.4 to 19.8 m g(-1), RLD from 980 to 11,650 m m(-3) and RSA from 2.4 to 35.4 m(2) m(-3). Most fine root biomass of trees was concentrated in the upper 20 cm of the mineral soil and in the humus layer (0-5 cm) in all stands. Understory fine roots accounted for 67 and 25% of total fine root biomass in the 10- and 120-year-old stands, respectively. Stand age had no affect on root tip number or branching frequency, but both parameters changed with soil depth, with increasing number of root tips and decreasing branching frequency with increasing soil depth for root fractions < 2 mm in diameter. Specific (mass based) root tip number and branching density were highest for the finest roots (< 1 mm) in the humus layer. Season (spring or fall) had no effect on tree fine root biomass, but there was a small and significant increase in understory fine root biomass in fall relative to spring. All morphological characteristics showed strong seasonal variation, especially the finest root fraction, with consistently and significantly higher values in spring than in fall. We conclude that fine root biomass, especially in the finest fraction (< 1 mm in diameter), is strongly dependent on stand age. Among stands, carbon concentration in fine root biomass was highest in the 30-year-old stand, and appeared to be associated with the high tree and canopy density during the early stage of stand development. Values of RLD and RSA, morphological features indicative of stand nutrient-uptake efficiency, were higher in the 30-year-old stand than in the other stands. 相似文献
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Material properties determining the insecticidal activity of highly divided porous materials on the pharaoh ant (Monomorium pharaonis) 
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英国的最新研究发现表明让蛋鸡自己钝化喙是一种成功的断喙的替代方法。对蛋鸡进行断喙已经在欧盟引起广泛争议,一些国家已经禁止进行断喙,这将对家禽业产 相似文献
7.
Dissolved aluminium (Al) in soils, mobilized by acid deposition, is considered a threat to forest health through hampering root growth and nutrient uptake. Since the end of the 1980s dissolved Al in forest soil water plays a key role in the assessment of critical loads of acid deposition. So far, most evidence for toxicity of dissolved Al in forest soil water is based on nutrient solution studies and pot experiments. Here, we present results from one of the few in situ ecosystem-scale forest manipulation experiments to study the effect of Al on mature forest trees. A plotwise addition of dilute AlCl3 was conducted during seven years in an even-aged spruce forest (Picea abies) in an area in Norway with low acid deposition. Soil solution concentrations of Al were increased to potentially toxic levels (up to 500 μmol L−1) and base cation (Ca + Mg + K) to inorganic Al ratios in the soil solution in the root zone were mostly below 1 in the Al-addition treatments. In the control treatment (only water addition) Al concentrations did not exceed 15 μmol L−1 and base cation to inorganic Al ratios were above 1. The toxic effects of Al on fine root growth and plant growth found in hydroponic studies and pot trials are not confirmed by this field manipulation. However, magnesium (Mg) contents in needles decreased significantly and persistently in plots with elevated Al concentrations, whereas the needle Ca content did not respond. The depletion of the Mg content in needles is suggested to be due to antagonistic effects of high Al concentrations at the root surface, consistent with observed reductions in Mg to Al ratio of inner bark. This study clearly supports a role for Al in critical load functions for forests as dissolved Al causes a decrease in uptake of Mg. However, other signs of reduced forest vitality were not observed. Soil base cation status may need to be included in risk evaluations of forest health under acid deposition. 相似文献
8.
Espen Lund Øyvind A. Garmo Heleen A. de Wit Torstein Kristensen Kate L. Hawley Richard F. Wright 《Water, air, and soil pollution》2018,229(11):368
Acid deposition has led to acidification and loss of fish populations in thousands of lakes and streams in Norway. Since the peak in the late 1970s, acid deposition has been greatly reduced and acidified surface waters have shown chemical recovery. Biological recovery, in particular fish populations, however, has lagged behind. Long-term monitoring of water chemistry and fish populations in Lake Langtjern, south-eastern Norway, shows that around 2008, chemical recovery had progressed to the point at which natural reproduction of brown trout (Salmo trutta) reoccurred. The stocked brown trout reproduced in the period 2008–2014, probably for the first time since the 1960s, but reproduction and/or early life stage survival was very low. The results indicate that chemical thresholds for reproduction in this lake are approximately pH?=?5.1, Ali?=?26 μg l?1, ANC?=?47 μeq l?1, and ANCoaa?=?10 μeq l?1 as annual mean values. These thresholds agree largely with the few other cases of documented recovery of brown trout in sites in Norway, Sweden, and the UK. Occurrence and duration of acidic episodes have decreased considerably since the 1980s but still occur and probably limit reproduction success. 相似文献
9.
Voortman T Hendriks HF Witkamp RF Wortelboer HM 《Journal of agricultural and food chemistry》2012,60(36):9035-9042
Gastrointestinal (GI) peptide hormones play an important role in short-term regulation of food intake and blood glucose levels. Modulating their release is of potential relevance for weight management and possibly diabetes. As currently available models are hard to extrapolate to the human situation, the use of porcine intestinal tissue, collected from slaughter pigs, was investigated for this purpose. Intestinal tissue disks showed a predicted regional release pattern of GI peptides. Various long-chain fatty acids differentially stimulated release of glucagon-like peptide 1 (GLP-1) (up to 500%) and glucagon-like peptide 2 (GLP-2) (up to 200%) from ileal tissue disks, but effects on peptide YY (PYY) did not reach significance. Short-chain fatty acids had no effects on the release of GLP-1, GLP-2, and PYY in either the ileum or colon. In conclusion, this porcine tissue model shows to be of advantageous use in a tiered approach to study the potential of satiety-inducing compounds to be selected for studies in humans. 相似文献
10.
Diploid families of Tuberosum hybrids as well as Tuberosum-wild species F1 hybrids were generated to select 2n-egg producing genotypes of different genetic backgrounds. Plants were selected if they
produced more than four seeds per berry after pollination with tetraploid males (2x⋅ot4x-crosses). From the nine families
of Tuberosum hybrids that were derived from one or two 2n-egg producing parents, 12 out of 82 (15%) 2n-egg producing plants
were selected. From the 32 families of Tuberosum-wild species F1 hybrids, 21 of 274 (8%) 2n-egg producing plants were selected. The level of 2n-egg formation was estimated in 25 selected
diploid hybrids and five control clones (three high, one moderate and one low 2n-egg producers) on the basis of seed set following
2x⋅4x-crosses using 13 tetraploid males in four crossing years. Besides the effect of the diploid 2n-egg producing female
on the seed set following 2x⋅4x-crosses (P = 0.0001), there was a significant effect of the tetraploid male (P = 0.0001),
whereas the effect of the crossing year (P = 0.0688) was less significant. On the basis of differences in the seed set following
2x⋅4x-crosses as compared to the control clones for low, moderate and high level of 2n-egg formation, the level of 2n-egg
formation in two of the newly selected hybrids was classified as very high, four were high, sixteen were moderate and three
were low. The significance of the selected hybrids for the genetic analysis of various restitution mechanisms of 2n-egg formation
is discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献