Factors influencing adult emergence from soil and the vertical distribution of burrowing scarab beetles Dasylepida ishigakiensis

The present study investigates the emergence of adult white grub beetles Dasylepida ishigakiensis Niijima et Kinoshita (Coleoptera: Scrabaeidae) from soil as well as their burrowing behaviours. ‘Standby behaviour’ (i.e. adults come to the soil surface where they expose their heads) is shown in the field and, along with emergence behaviour, is entrained by LD photocycles. These 24‐h rhythms persist after transfer to continuous light conditions for 2 days. By contrast, beetles transferred from LD photocycles to continuous dark conditions fail to show standby behaviour; thus, it appears to be manifested only in the presence of illumination. Under dark conditions, beetles emerge completely from the soil directly at the time when standby behaviour is otherwise expected to occur. Emerged adults then burrow back into the soil before dawn. Virgin and mated males, as well as virgin females, which are expected to emerge from the soil for mating on later evenings, burrow to a relatively shallow depth (<2 cm), whereas mated females burrow deeper (2–10 cm). Soil properties such as moisture, grain size, topography and temperature influence the burrowing behaviour and the depths that the beetles reach.     

The moisture content of timber in relation to attack by Lyctus powder-post beetles

The relation between moisture content of oak sapwood and rate of development of Lyctus brunneus has been investigated at 23C. Oviposition took place normally in samples of various moisture contents between 5.5 and 23.5%. The eggs hatched in wood of 7.7% moisture content, but not of 61% moisture content, although the embryos developed fully. The rate of gain in weight of young larvae increased to a maximum as the moisture content of the wood rose to about 14.2% and then fell again. The rate of development from egg to adult followed a somewhat similar curve with a maximum at 16% moisture content. At all moisture contents the first male emerged a few days earlier than the first female. The average weight of the male beetles was less and their moisture content greater than those of the corresponding females. The average weight of the beetles showed a tendency to increase at moisture contents of the wood above 97%. The average moisture content of the males was fairly constant up to 156% moisture content of the wood, but that of the females rose slowly as the moisture content of the samples increased. In wood of 15.6% moisture content at 23C. the minimum period of development from egg to adult was 167 days; at 14.2% moisture content and 27.5 C. this was reduced to 142 days. Green timber was shown to be liable to infestation as soon as a superficial skin was formed of a suitable moisture content; the upper limiting moisture content is probably the fibre saturation point. Control of moisture content of timber cannot be achieved sufficiently easily for it to become an important method for the control of Lyctus infestation.     

Biomass distribution of two subalpine dwarf‐shrubs in relation to soil moisture and nutrient content

Question: Do soil water content and/or soil nitrogen (N) content and/or soil phosphorus (P) content affect the biomass of Vaccinium myrtillus and V. vitis‐idaea in a sub‐alpine heath? Location: Dolomites, northern Italy, 1800 m a.s.l. Methods: We determined above‐ground and below‐ground biomass of the shrubs at three sites, each on a different substrate type. At each site, we determined soil N‐ and P‐contents. We also determined leaf water potential (Psi;₁), N‐ and P‐concentrations in plant tissues and litter, as well as δ¹³C and δ¹⁵N in mature leaves. Results: V. myrtillus biomass was highest at the silicate site, V. vitis‐idaea biomass was highest at the carbonate site. Both shrubs had low biomass at the peat site, possibly due to a toxic effect of waterlogging in wet soils. For both species, pre‐dawn Psi;₁ indicated optimal hydration and midday Psi;₁ did not show any sign of water stress. Water use efficiency (WUE) did not differ among sites for any species. Whole‐plant nutrient concentrations showed that, with increasing biomass, N was diluted in V. myrtillus tissues while P was diluted in V. vitis‐idaea tissues. Foliar N‐concentration was higher overall for V. myrtillus. Foliar P‐concentration in V. myrtillus peaked at the silicate site. Foliar N : P ratios suggested that V. myrtillus was primarily P‐limited and V. vitis‐idaea primarily N‐limited. Conclusions: Water content affected the distribution of the two shrubs in a similar way, higher P‐availability in the soil enhanced V. myrtillus rather than V. vitis‐idaea.     

Distribution and population dynamics of Collembola in relation to soil moisture

The significance of variations in soil moisture for the distribution and abundance of the four collembolan species Tomocerus minor, Orchesella cincta. Lepidocyrtus lignorum and Entomnbrya nivalis has been studied in a pine forest. During a relatively dry summer, the distribution and abundance of these species were examined on two sites with an initially different soil water content and depth of the titter/humus layer. The distribution of the species investigated could be described with the negative binomial distribution. During the sampling period. Lloyd's "index of patchiness", / for T. minor and E. nivalis was subject to changes. For T. minor this was probably related to soil water content.
The densities of T. minor and O. cincta were higher in the wet site than in the drier site. At the beginning and at the end of the sampling period the drought tolerant E. nivalis reached equal densities in both sites. The density fluctuations of the four species appeared to be totally different during the sampling period: the drought sensitive species T. minor decreased strongly, L. lignorum remained constant and the drought tolerant species O. cincta and E. nivalis increased strongly. These latter two species were able to survive the dry periods and to attain high densities by reproduction. The results agree with laboratory data on distribution and survival in relation to humidity.     

Different distribution patterns of woody species on a slope in relation to vertical root distribution and dynamics of soil moisture profiles

Distribution patterns along a slope and vertical root distribution were compared among seven major woody species in a secondary forest of the warm-temperate zone in central Japan in relation to differences in soil moisture profiles through a growing season among different positions along the slope. Pinus densiflora, Juniperus rigida, Ilex pedunculosa and Lyonia ovalifolia, growing mostly on the upper part of the slope with shallow soil depth had shallower roots. Quercus serrata and Quercus glauca, occurring mostly on the lower slope with deep soil showed deeper rooting. Styrax japonica, mainly restricted to the foot slope, had shallower roots in spite of growing on the deepest soil. These relations can be explained by the soil moisture profile under drought at each position on the slope. On the upper part of the slope and the foot slope, deep rooting brings little advantage in water uptake from the soil due to the total drying of the soil and no period of drying even in the shallow soil, respectively. However, deep rooting is useful on the lower slope where only the deep soil layer keeps moist. This was supported by better diameter growth of a deep-rooting species on deeper soil sites than on shallower soil sites, although a shallow-rooting species showed little difference between them.     

Growth of crop roots in relation to soil moisture extraction

Growth of the roots of sugar beet, potato and barley in the field was observed through glass panels and related to changes in soil moisture measured by a neutron probe during 1969–71. The depth of observed root growth was generally related to, but 10–15 cm deeper than, the maximum depth of soil-moisture extraction. On average of three years, sugar beet, potato and barley used water from the top 23, 33 and 45 cm soil respectively by the beginning of June, and from the top 70, 68 and > 100 cm soil by the end of June. Maximum soil drying in each horizon gave an in situ measure of available water capacity, and showed that sugar beet and barley eventually extracted similar amounts of water from each horizon, but potatoes extracted less, especially from below 60 cm. Between 30 and 100 cm deep, the in situ available water capacity (per 10 cm soil) progressively decreased from 16 to 10, 15 to 5 and 16 to 8 mm under sugar beet, potato and barley respectively. The calculated soil-moisture deficit (potential evapotranspiration minus rainfall) and measured soil moisture deficit were not related early in the growing period before the crops established much leaf cover.     

Interspecific variation in sapling mortality in relation to growth and soil moisture

To examine the causes of landscape variation in forest community composition, we have quantified sapling mortality as a function of growth and soil moisture for seven dominant species in transition oak-northern hardwood forests of the northeastern USA. We located saplings in sites that encompassed a wide range of variation in soil moisture and light availability. In mesic conditions, the probability of mortality decays rapidly with increasing growth among shade tolerant species and more gradually among shade intolerant species: the rank order of survivorship at low growth rates is Tsuga canadensis > Fagus grandifolia > Acer saccharum > Fraxinus americana > Acer rubrum > Quercus rubra > Pinus strobus . The relationship between probability of mortality and growth does not vary with soil moisture among species insensitive to drought: Tsuga canadensis , Quercus rubra, and Pinus strobus . However, probability of mortality increases substantially with decreasing soil water availability for the other four species. Acer saccharum and Fagus grandifolia have high mortality rates under xeric conditions even when their growth is not suppressed. Acer rubrum and Fraxinus americana exhibited a steady but more gradual increase in the probability of mortality with decreasing soil moisture. Among the five deciduous hardwood species we examined there is a weak inverse relationship between the ability to survive growth suppression, a measure of shade tolerance, and the ability to survive in xeric conditions, a measure of drought tolerance. Tsuga canadensis , however, is tolerant of growth suppression and exhibits high survivorship in xeric conditions, while Pinus strobus is intolerant of growth suppression but insensitive to soil moisture. Species differences in water-dependent mortality are consistent with the species distributions across landscape gradients of soil water availability.     

土壤水分时空变异及其与环境因子的关系

土壤水分的时空变异是指在一定的景观内,不同时间、地点和土层的土壤水分特征存在明显的差异性和多样性。土壤水分时空变异是由多重尺度上的土地利用（植被）、气象（降雨）、地形、土壤、人为活动等诸因子综合作用的结果,但就其某一具体地区而言存在着重点尺度和主控因子,土壤水分时空变异的重点尺度与主控因子的时空关系因时间、空间和尺度而异。本文综述了土壤水分（尤其是黄土高原地区）的时空变异与其环境因子时空关系的研究进展,并提出了广眨开展多重时空尺度上土壤水分的时空变异与其诸因素的时空关系,研究土壤水分时空变异性的尺度转换规律,确定重点尺度及其相应的主控因子。     

Modelling field emergence patterns in arable weeds

A model was developed to simulate weed emergence patterns after soil cultivation. In the model, the consecutive processes of dormancy release, germination and pre-emergence growth were modelled in separate modules. Input variables of the model were: date of soil cultivation, soil temperature and soil penetration resistance. Output variables of the model were: seedling density and timing of seedling emergence. The model was parameterized for Polygonum persicaria , Chenopodium album and Spergula arvensis with data from previous field and laboratory experiments. The model was evaluated with data from an experiment, in which emergence of P. persicaria , C. album and S. arvensis was monitored in field plots that were cultivated once only, at one of five dates in the spring. At the same time as the field observations on seedling emergence, seasonal changes in seed dormancy of the buried weed seeds were assessed by testing the germination of seed lots that were buried in envelopes. From a comparison between field observations and simulated data, it appeared that the model overestimated the rate of dormancy release in spring, whereas germination and pre-emergence growth were simulated well. In general, therefore, both the numbers of emerging seedlings and the timing of emergence could be predicted accurately, when dormancy was not simulated but introduced from experimental data. Improvement of predictions of field emergence of weeds should mainly focus on increasing the precision of the simulation of dormancy release. Close correlations were found between seedbed temperature and both the extent and rate of seedling emergence, but analysis with the simulation model revealed that they were only partly based on causal relationships, so that they have limited predictive value.     

Spatial patterns of desert annuals in relation to shrub effects on soil moisture

Questions: What are the effects of a shrub (Haloxylon ammodendron) on spatial patterns of soil moisture in different seasons? How does productivity of understorey annuals respond to these effects? Are such effects always positive for annuals under shrubs? Location: South Gurbantunggut Desert, northwest China. Methods: Using geostatistics, we explored seasonal patterns of topsoil moisture in a 12 × 9‐m plot over the growing season. To determine spatial patterns of understorey annuals in response to H. ammodendron presence, biomass of annuals was recorded in four 0.2 × 5.0‐m transects from the centre of a shrub to the space between shrubs (interspace). We also investigated vertical distribution of root biomass for annuals and soil moisture dynamics across soil profiles in shrub‐canopied areas and interspaces. Results: Topsoil moisture changed from autocorrelation in the wet spring to random structure in the dry season, while soil moisture below 20 cm was higher in shrub‐canopied areas. Across all microhabitats, soil moisture in upper soil layers was higher than in deeper soil layers during the spring wet season, but lower during summer drought. Topsoil was close to air‐dry during the dry season and developed a ‘dry sand layer’ that reduced evaporative loss of soil water from deeper layers recharged by snowmelt in spring. Aboveground biomass of understorey annuals was lowest adjacent to shrub stems and peaked at the shrub margin, forming a ‘ring’ of high herbaceous productivity surrounding individual shrubs. To acclimate to drier conditions, annuals in interspaces invested more root biomass in deeper soil with a root/shoot ratio (R/S) twice that in canopied areas. Conclusions: Positive and negative effects of shrubs on understorey plants in arid ecosystems are commonly related to nature of the environmental stress and tested species. Our results suggest there is also microhabitat‐dependence in the Gurbantunggut Desert. Soil water under H. ammodendron is seasonally enriched in topsoil and deeper layers. Understorey annuals respond to the effect of shrubs on soil water availability with lower R/S and less root biomass in deeper soil layers and develop a ‘ring’ of high productivity at the shrub patch margin where positive and negative effects of shrubs are balanced.     

中国典型森林生态系统土壤水分时空分异及其影响因素

森林土壤水分作为物质与能量循环的载体影响林木生长与发育,并通过影响水分在陆气之间的循环与分配影响区域气候。基于我国不同气候带的9个森林生态系统定位观测站的长期观测数据,探究了2005-2016年中国典型森林生态系统土壤水分的空间分异及其时间动态,并进一步分析了影响其时空分异的环境因素。主要研究结论如下：（1）9个森林生态系统的土壤水分多年均值介于12.45%-36.30%之间,空间上呈现中温带、亚热带、热带土壤水分较高,暖温带土壤水分较低的分布特征。降水蒸散差（降水与蒸散的差值）可以解释我国森林生态系统土壤水分空间分异的62%（P<0.05）;（2）我国北部与东部季风区森林区域土壤水分呈上升趋势,降水上升是主因,其中暖温带北京、南亚热带鼎湖山与鹤山森林土壤水分上升趋势显著,增幅分别为0.67%/a、1.72%/a与0.69%/a;西南地区森林生态系统土壤水分呈下降趋势,该趋势由降水下降与蒸散上升共同导致,其中中亚热带贡嘎山及哀牢山森林生态系统土壤水分下降趋势显著,降幅分别为-1.77%/a与-0.94%/a;土壤水分时间分异与降水蒸散差的相关性最高（R=0.59,P<0.01）;（3）土壤水分呈下降趋势的森林生态系统中,春季土壤水分变化主导了年际变化,土壤水分上升的森林生态系统中,年际变化则是由秋、冬季主导。（4）与ERA-interim土壤水分再分析数据比较得出,两者在空间格局与变化趋势上均具有较高的一致性。CERN土壤水分观测数据反映了无人为干扰的自然条件下森林土壤-植被-气候之间的反馈作用,可为基于模型的土壤水分研究提供长时序的验证数据。     

Biodiversity of soil biota and plants in abandoned arable fields and grasslands under restoration management

The currently widespread abandoning of agricultural land use in Western Europe offers new opportunities for ecological restoration and nature conservation. This is illustrated for abandoned arable fields and for permanent grasslands cut for hay after the cessation of fertilizer application. Although initiated by a sudden reduction of nutrient input to the system, the changing nutrient supply from the soil is considered to be the main driving force of succession. The soil nutrient supply is affected by soil organisms, both directly (root symbionts and herbivores) and indirectly (nutrient mineralization from dead organic matter). It is argued that because of the close association of changes in species diversity with changes in the functioning of ecosystems, biodiversity has to be studied in an ecosystem ecology context.     

Summer bird abundance and distribution on set-aside fields on intensive arable farms in England

The abundance and distribution of breeding birds were compared on paired fields comprising one set-aside field and one crop field, on 11 intensive arable farms in eastern and western England. A single observer made four visits to all set-aside and crop fields between April and July and recorded all birds seen during standardised counts and transects.
Rotational and non-rotational set-aside supported higher densities and more species of birds than fields of wheat, brassicas, root crops and seed rye. These differences in density, between set-aside and crops, were evident across a suit of species including waders, gamebirds, pigeons and passerines and were particularly marked on rotational set-aside. The majority of species recorded in fields away from boundaries would have been feeding rather than nesting there and higher bird densities on set-aside compared with adjacent arable crops probably reflects greater food abundance in the former.
The study is the first to demonstrate a clear habitat preference for set-aside by a wide range of bird species throughout the breeding season and it allows a number of recommendations to be made concerning the development of cost-effective agri-environment measures. The fact that the majority of birds utilised the outer 5 m, or in some cases 20 m, margin of the field suggests that many of the benefits of whole field set-aside may be derived from marginal strips. A slight, but not significant preference for rotational over non-rotational set-aside suggest such margins should be managed to maintain a patchy, relatively diverse sward of arable plants. A key feature of set-aside is the scale at which it has been incorporated into the arable landscape. Agri-enviromental schemes will only provide similar national benefits if they are implemented on a wide scale in such as way as to promote high uptake by farmers.     

The role of plant water storage and hydraulic strategies in relation to soil moisture availability

Plant and Soil - We aimed to clarify the intraspecific variation in the morphological traits of branch orders under different soil conditions in Chamaecyparis obtusa (Siebold &amp; Zucc.) Endl....