Bradyrhizobium Populations Occur in Deep Soil under the Leguminous Tree Acacia albida

Soil cores were drilled under the leguminous tree Acacia albida growing in two different ecoclimatic zones of West Africa: the Sahelian area (100 to 500 mm of annual rainfall) and the Sudano-Guinean area (1,000 to 1,500 mm of annual rainfall). Soil samples were collected at different depths from the surface down to the water table level and analyzed for the presence of rhizobia able to nodulate A. albida. In both areas, population densities of rhizobia were substantially greater near the water table than near the surface. In the Sahelian area, rhizobia were present as deep as 34 m at a concentration of 1.3 × 10³/g of soil. In the Sudano-Guinean area, population densities at 0.5 to 4.5 m depth were higher than in the Sahelian area and, at several depths, comparable to that of temperate soils supporting legume crops (10⁴ rhizobia per g of soil). Surface and deep soil isolates from all four sites were found to be slow-growing rhizobia (Bradyrhizobium sp.). The proportion of effective isolates was almost the same within surface and deep soils.     

物种组成对高寒草甸植被冠层降雨截留容量的影响

高寒草甸退化减少地上生物量、叶面积指数(LAI),因而减少冠层降雨截留容量(S)。但是,未有研究评价物种组成改变对S的影响。用水浸泡法和水量平衡法研究青藏高原高寒草甸3个不同退化阶段下(未退化、轻度退化、中度退化)的S变化规律,并评价物种组成改变对S的影响。结果表明:高寒草甸退化显著减少S(P<0.05)。在未退化、轻度退化、中度退化的高寒草甸,水浸泡法测得的S分别为0.612 mm,0.289 mm 和0.217 mm;水量平衡法测得的S分别为0.979 mm,0.493 mm 和0.419 mm。物种组成改变对S的影响表现为:随着高寒草甸的3个不同退化阶段,S减少的幅度先大于后小于LAI减少的幅度。原因是:(1)在未退化的草甸,鹅绒委陵菜(Potentilla arserina)的叶面积占有显著优势,占总叶面积的31.18%;在轻度退化的草甸,禾本科植物(Graminoid)的叶面积占有显著优势,占总叶面积的44.41%,而鹅绒委陵菜是稀有种,仅占总叶面积的3.76%;在中度退化的草甸,鹅绒委陵菜的叶面积占有显著优势,占总叶面积的19.91%;(2)鹅绒委陵菜的叶单位面积吸附水量(S_L)是禾本科植物的大约2.5倍。     

Trends in savanna structure and composition along an aridity gradient in the Kalahari

Abstract. The Kalahari sand sheet occupies 2.5 million ha in southern Africa. It is an area with relatively similar deep aeolian soils, and a strong south to north gradient in rainfall, from 200 to 1000 mm mean annual precipitation (MAP) in the region studied. This provides an excellent basis for gradient studies at the subcontinental scale. This paper briefly reviews the literature on the vegetation of the Kalahari and describes the vegetation structure and composition at 11 new sites. There is a clear gradient in woody plant biomass (as indexed by basal area) from south to north. Above the minimum level of 200 mm MAP, the woody basal area increases at a rate of ca. 2.5 m².ha^‐1 per 100 mm MAP. Mean maximum tree height also increases along the gradient, reaching 20 m at ca. 800 mm MAP. The number of species to contribute > 95% of the woody basal area increases from one at 200 mm to 16 at 1000 mm MAP. Members of the Mimosaceae (mainly Acacia) dominate the tree layer up to 400 mm MAP. They are replaced by either the Combretaceae (Combretum or Terminalia) or Colophospermum mopane of the Caesalpinaceae between 400 and 600 mm MAP, and by other representatives of the Caesalpinaceae above 600 mm MAP. The vegetation is largely deciduous up to 1000 mm MAP, except for species that apparently have access to groundwater, which may be locally dominant above about 600 mm MAP.     

Soil fertility response to <Emphasis Type="Italic">Ulex europaeus</Emphasis> invasion and restoration efforts

Invasive plant species can substantially alter the soil fertility of the ecosystems they invade, and in doing so have the potential to reduce the suitability of the soil for native species. Even after removal of the invader these alterations can inhibit the reestablishment of native species. We evaluated the impact of invasion by the leguminous shrub Ulex europaeus on soil properties on Mauna Kea, HI. We also investigated the effect of efforts to remove U. europaeus and restore native ecosystems in the study area; where the efforts included bulldozing the U. europaeus and planting introduced Cryptomeria japonica to compete with regenerating U. europaeus. Mauna Kea supports a strong rainfall gradient and substantial associated variation in soil properties. We use statistical models to extract the effect of invasion and restoration from the influence of rainfall. We found U. europaeus decreases soil pH, calcium content, base saturation, and labile phosphorus. Restoration efforts over an 11-year period restored the soil’s calcium and phosphorus content to levels comparable to those found in uninvaded soils on Mauna Kea, demonstrating that the effects of U. europaeus on soils are reversible.     

Soil translocation by termites of the genus Odontotermes (Holmgren) (Isoptera: Macrotermitinae) in an arid area of Northern Kenya

Summary The study was conducted in an arid area of Northern Kenya, Marsabit District. The area receives an average annual rainfall of 200 mm and supports scanty plant and animal life.The most common termite species are of the genus Odontotermes. The assessment of soil sheeting translocated on food surfaces by O. latericius (Haviland) and O. boranicus Ghidini was carried out using a stratified random design.Both species were found to translocate soil at a rate equivalent to 1059 kg of soil per hectare per year. Rainfall was found to have an influence on the building activity of Odontotermes soil sheeting. Odontotermes soil sheeting was shown to differ from other surrounding soils in both physical and chemical properties. Therefore, Odontotermes have a significant effect on soil structure and texture.     

祁连山典型灌丛降雨截留特征

基于2010年6月至10月的野外试验数据,研究了祁连山金露梅、高山柳、沙棘和鬼箭锦鸡儿灌丛降雨截留特征,分析了降雨量和雨强对灌丛降雨截留过程的影响。结果表明:试验期间共降雨298.6 mm,在降雨量<2.1 mm时,降雨被全部截留,实际发生穿透和茎流的降雨为283.1 mm;金露梅灌丛穿透雨量、茎流量和截留量分别为175.8 mm(62.0%)、9.5 mm(3.4%)和62.0 mm(34.6%),高山柳为179.8 mm(63.5%)、9.1 mm(3.2%)和63.5 mm(33.3%),沙棘分别为148.1mm(52.3%)、22.5mm(8.0%)和52.3 mm(39.7%),鬼箭锦鸡儿分别为170.4 mm(60.2%)、11.8 mm(4.2%)和60.2 mm(35.6%);灌丛穿透雨量、茎流量和截留量均与降雨量呈显著线性正相关(P<0.001);穿透率、茎流率和截留率与降雨量呈指数函数关系(P<0.05);平均雨强与截留率关系以指数函数拟合最好(P<0.05)。在降雨性质相同的情况下,植被形态特征是影响灌丛降雨截留的重要因素。     

Germination, field establishment patterns and nitrogen fixation of indigenous legumes on nutrient-depleted soils

Integrating N₂-fixing indigenous legumes in smallholder farming systems has potential to alleviate some of the major soil fertility constraints associated with lack of nitrogen (N) inputs in many parts of Sub-SaharanAfrica. Studies were conducted under low (450–650 mm yr^?1) and high (>800 mm yr^?1) rainfall areas in Zimbabwe to investigate the establishment and nitrogen fixation patterns of fifteen indigenous legume species. The legume seeds were broadcast in mixtures at 120 seeds m^?2 species^?1 during 2004/05 and 2005/06 rainfall seasons.Eriosema ellipticum, Crotalaria ochroleuca andC. pallida had emergence rates above 15% compared with <10% forTephrosia radicans andIndigofera astragalina. Seed hardness accounted for >50% germination failure, while low viability explained 10–30%.Crotalaria ochroleuca andC. pallida attained a maximum biomass of 5–9 t ha^?1 (dry weight) over six months, while species that reached peak biomass over three months (e.g.C. cylindrostachys andC. glauca) gave lowest yields of ≈0.5 t ha^?1. Biennials,Neonotonia wightii, E. ellipticum and Tephrosia radicans, exhibited slow growth rates and only attained their maximum biomass of ≈2 t ha^?1 in the second season. The legumes derived 60–99% of their N from the atmosphere, fixing 5–120 kg N ha^?1 under low rainfall and 78–267 kg N ha^?1 under high rainfall. These findings suggest that the legumes could contribute in restoring productivity of soils continuously cultivated with little or no nutrient inputs in most of Zimbabwe and similar agro-ecologies in SubSaharan Africa.     

Species differences in carbon isotope ratios, specific leaf area and nitrogen concentrations in leaves of Eucalyptus growing in a common garden compared with along an aridity gradient

Leaves produced in 2004 of 422 species of Eucalyptus whose natural habitat is southern Australia were sampled at the Currency Creek Arboretum in South Australia where the annual (mainly winter) rainfall is about 400 mm. Tree height, leaf area, leaf dry weight, leaf nitrogen (N) concentration and leaf carbon isotope ratio (δ¹³C) were measured and the specific leaf area (SLA) calculated. Among the 422 species, the SLA varied from 1.5 to 8.8 m² kg^?1 and N concentration varied from 0.6 to 2.1%, much greater than in 64 species collected along an aridity transect from southwestern Western Australia to central Australia in 2003. Also, the range of leaf δ¹³C values was similar in the common garden to that across the aridity transect. For the 45 species present in both studies, the SLA and leaf N concentration in the common garden were similar to those measured in leaves along the aridity transect, indicating that these characteristics are inherent in the species and vary little with environment. The variation in leaf δ¹³C in the common garden was just as great as along the transect, but the values measured in the one location were poorly correlated with those along the transect. This was not expected, as the variation in δ¹³C at one common site in South Australia was anticipated to be less than along the aridity gradient where annual rainfall varied from 250 to 1200 mm. Path analysis on the 45 species common to both studies indicated that rainfall did not have a direct effect on δ¹³C, but the differences in δ¹³C resulted from indirect effects of rainfall on SLA and N concentration. δ¹³C was negatively correlated with SLA but positively correlated with N. Thus, both effects may compensate for each other so that no significant relationship between δ¹³C and rainfall was observable. However, there is a large degree of variation of δ¹³C at any level of rainfall. The origin and ecological implications of this observation are discussed.     

The occurrence of stickfast fleas Echidnophaga spp. on wild rabbits Oryctolagus cuniculus (L.) in Victoria

A survey of rabbits collected throughout Victoria showed that Echidnophaga spp. were present only in the north-west of Victoria, the Mallee region, in an area bounded by the 400 mm isohyet. There was a correlation with rainfall within this area. Overall, the ratio of male fleas to female fleas was about 0.5:1, peaking at 0.9:1 in late summer or early autumn. The infestation rates of male and female rabbits were similar, although female rabbits were generally more heavily infested than male rabbits. The species collected were E. myrmecobii and E. perilis with an occasional specimen of E. gallinacea. E. perilis was more commonly found in the southern area of the Mallee, and E. myrmecobii in the northern area. Gravid female E. myrmecobii were present in every collection but no gravid E. perilis were found during the winter months.     

Floral and macroecological evolution within Cyrtanthus (Amaryllidaceae): Inferences from combined analyses of plastid ndhF and nrDNA ITS sequences

One of the most diverse members of Amaryllidaceae is Cyrtanthus Aiton, a large, sub-Saharan Africa genus of approximately 55 species found mostly in South Africa. To investigate phylogenetic and biogeographic relationships within Cyrtanthus, sequence data from the plastid ndhF gene and the ITS nrDNA region for 41 species were analyzed with parsimony, maximum likelihood, and Bayesian-inference approaches. Various recombination detection algorithms were used to test for interspecific hybridization in the ITS alignment. The genus resolved as monophyletic, comprising three poorly to well-supported major lineages: a predominantly Afrotemperate lineage, largely restricted to seasonally moist sites in summer rainfall southern Africa, a subtropical lineage found mostly in nonseasonal rainfall regions, often in dry habitats, and a Cape Floristic Region-centered lineage in which most species are concentrated in the summer-dry to nonseasonal rainfall southwest. The ITS sequence alignment shows no evidence for reticulation between any of the species. Relationships inferred by the molecular data disagree with those derived from morphological data, but agree with previously published groupings based on karyotype morphology. Fitch optimization of selected floral characters on the combined gene tree reveals recurrent patterns of convergence. Ornithophilous floral forms occur in parallel among the three primary clades, putatively sphingophilous species are concentrated in the Afrotemperate lineage in seasonally moist upland grasslands; the brush-type Aeropetes tulbaghia butterfly and inferred long-proboscid fly pollination syndromes are unique in the Cape lineage. Macroecological factors inferred to have influenced the evolution of Cyrtanthus are changes in rainfall seasonality, the advent of fire, and the availability of new habitats at high and low altitudes and in rock-free soils or rock crevices. This study gives greater clarity on relationships within the genus and enables its division into three informal infrageneric groups.     

Distribution patterns of Dikarya in arid and semiarid soils of Baja California,Mexico

Approximately four-fifths of the land area of Baja California (BC) in Mexico are occupied by arid and semiarid soils, the mycobiota of which is virtually uncharacterized. In the first culture-independent study of the mycobiota of BC, we collected soil from five different locations in the region and constructed a Dikarya-specific gene library for the ITS region of nuclear ribosomal DNA. Clones were analyzed by RFLP, were sequenced for phylogenetic analyses, and diversity and similarity indices were calculated. The ascomycete Penicillium dipodomyicola was the most frequent fungus found in soil at the most arid location studied, and the basidiomycete Coprinellus radians was the most frequent at the location receiving the highest rainfall. Other frequent members of the soil mycobiota were identified as Alternaria spp., Ceratobasidium sp., Coniozyma leucospermi, Nematoctonus robustus, Penicillium griseofulvum, Tulostoma kotlabae and uncultured members of the Dikarya. Several sequences were identified as those of uncultured fungi, one of which was previously reported from other hot deserts. Arid soils and the transitional zones between arid and semiarid soils had the most similar fungal diversity, with the former soils having a community from which basidiomycetes were absent, and the soil receiving the highest precipitation having a community dominated by basidiomycetes.     

The effects of drought upon epigeal Collembola from arable soils

1 Springtails (Hexapoda, Collembola) are usually associated with moist microhabitats. However, some species show adaptations to ecosystems subjected to periodic desiccation. This study examined the effects of short-term drought conditions upon epigeal Collembola collected from arable fields. 2 An emergence trap was used in the laboratory to investigate collembolan activity, particularly the emergence of newly hatched juveniles from soils subjected to a simulated drought and to varied levels of simulated rainfall. 3 Addition of water to soils subjected to a 4-month simulated drought resulted in synchronized emergence of juveniles of Sminthurinus elegans, Sminthurus viridis and Bourletiella hortensis. As anhydrobiotic nymphs were not found in the soil, these juveniles are likely to have recently hatched from eggs in the soil. 4 The same species were shown to emerge when desiccated soil samples were treated with simulated heavy rainfall. No emergence occurred in soils which received no water, whilst only a few juveniles were present under a regime of the lowest monthly rainfall recorded for the area in the spring. 5 This study provides the first evidence that in northern European arable systems some epigeal Collembola can survive considerable periods of drought as eggs, emergence of which is triggered by rainfall. These findings have implications for the effects of predicted climatic changes upon collembolan populations, the recovery of collembolan communities following pesticide applications in agroecosystems, and also provide a plausible mechanism for dispersal of Collembola as wind-blown eggs.     

Canopy Interception for a Tallgrass Prairie under Juniper Encroachment

Rainfall partitioning and redistribution by canopies are important ecohydrological processes underlying ecosystem dynamics. We quantified and contrasted spatial and temporal variations of rainfall redistribution for a juniper (Juniperus virginiana, redcedar) woodland and a tallgrass prairie in the south-central Great Plains, USA. Our results showed that redcedar trees had high canopy storage capacity (S) ranging from 2.14 mm for open stands to 3.44 mm for closed stands. The canopy funneling ratios (F) of redcedar trees varied substantially among stand type and tree size. The open stands and smaller trees usually had higher F values and were more efficient in partitioning rainfall into stemflow. Larger trees were more effective in partitioning rainfall into throughfall and no significant changes in the total interception ratios among canopy types and tree size were found. The S values were highly variable for tallgrass prairie, ranging from 0.27 mm at early growing season to 3.86 mm at senescence. As a result, the rainfall interception by tallgrass prairie was characterized by high temporal instability. On an annual basis, our results showed no significant difference in total rainfall loss to canopy interception between redcedar trees and tallgrass prairie. Increasing structural complexity associated with redcedar encroachment into tallgrass prairie changes the rainfall redistribution and partitioning pattern at both the temporal and spatial scales, but does not change the overall canopy interception ratios compared with unburned and ungrazed tallgrass prairie. Our findings support the idea of convergence in interception ratio for different canopy structures under the same precipitation regime. The temporal change in rainfall interception loss from redcedar encroachment is important to understand how juniper encroachment will interact with changing rainfall regime and potentially alter regional streamflow under climate change.     

The ecology of Maesopsis eminii Engl. in tropical Africa

Maesopsis eminii is referred to as one of the most widely distributed African tree species. However, its occurrence in Africa has never been mapped and little is known as to how this species can sustain in different environments. To gain insight into Maesopsis’ ecology, we (i) made a synthesis of its functional trait data from the literature, (ii) investigated phenological patterns using data on four M. eminii trees from Yangambi, DR Congo, (iii) assessed an empirical provenance trial from Uganda on 600 Maesopsis trees and (iv) synthesized geo‐referenced point location maps of Maesopsis entailing WorldClim precipitation and temperature and FAO soils, rainfall and ecological zones for Africa. We found M. eminii to straddle the equator equidistantly in terms of latitude (10.97°N and 10.98°S) covering five forest types where twenty soil types and variable rainfall regimes support complex plant biodiversity. Maesopsis eminii was, however, largely concentrated in the tropical rainforest ecosystem which contains fertile Orthic Ferralsol soils. More than 97% of the point locations were found where annual precipitation was >1000 mm, and 82% occurred where average annual temperature was 22–28°C. Its functional traits, phenology and provenance trial findings explained its occurrence in Africa.     

Phenology of ixodid ticks of the genus Dermacentor in the Central Ciscaucasia

In Stavropol Territory, ixodid ticks of the genus Dermacentor are represented by three species: D. marginatus, D. reticulatus, and D. niveus. D. marginatus is the most widespread species, constituting 14.8% of all the ticks in the region; D. reticulatus and D. niveus are found less frequently, constituting 2.8% and 0.01%, respectively. D. marginatus and D. reticulatus are spread mostly in the forest-steppe and steppe zones of Stavropol Territory. D. niveus is represented by solitary specimens in arid and semidesert zones. The main hosts of adult D. marginatus in Stavropol Territory are cattle (88.4%) and sheep and goats (5.3%). The hosts of D. reticulatus are also cattle (72.3%) and sheep and goats (4%). D. marginatus activates at an average monthly temperature of +2.07°C and average monthly rainfall of 47.2 mm. The peak of parasitizing on hosts was observed at an average monthly temperature of +7.8°C and average monthly rainfall of 56.2 mm. The autumnal activation was recorded at an average monthly temperature of +15.3°C and average monthly rainfall of 58.2 mm.     

Growth of vineyard roots into segmentally ameliorated acidic subsoils

Grapevine growth and production is limited in the Port Macquarie region by acidic subsoils and high exchangeable aluminium. Root growth is restricted to about 15 cm depth, and despite high growing season rainfall (920 mm, September to March) which exceeds predicted evapotranspiration for the period (400 mm), the vines suffer periodic water stress. Slotting is a technique of subsoil amelioration allowing thorough incorporation of lime to depth. Slots are 150 mm wide, and in this experiment were installed to 400 mm depth. The aim of slotting is to improve root growth in the subsoil, thus increasing plant access to water and nutrients previously inaccessible. The experiment was conducted in a Chardonnay vineyard planted in 1982. Lime was incorporated into the slots at about 2 t ha^-1 with a further 8 t ha^-1 spread on the surface, mixed and moved to form an undervine bank. Soil and root samples were taken in February, 1990. Slotting caused pH_CaCl2 to increase from 4.3 to 5.0 to 400 mm depth. Associated with this was a more than ten-fold increase in root length density. The slotting technique gives the opportunity to improve dense, poorly drained acidic soils and make them suitable for horticulture production.     

Reproductive biology of Heteropneustes fossilis in a wetland ecosystem (Gajner Beel,Bangladesh) in relation to eco-climatic factors: Suggesting a sustainable policy for aquaculture,management and conservation

The stinging catfish, Heteropneustes fossilis (Bloch, 1974) is a commercially important fish species in Asia. This is an important food fish as is enriched with high amounts of protein, iron and calcium. The current research demonstrates the population structure, size at sexual maturity, spawning- and peak-spawning season and fecundity of H. fossilis in an important wetland ecosystem - Gajner Beel in northwestern Bangladesh with an aim of its sustainable conservation through induced breeding and aquaculture practices. A total of 426 stinging catfish captured from the Gajner Beel through monthly sampling from January to December 2019 used in the study. Total length (TL), standard length (SL) and body weight (BW) of individual fishes were measured. The size ranges were with 6.70–24.10 cm TL, 1.37–83.94 g BW. Gonads were removed carefully through ventral dissection and weighted. L_m was 14.02, 13.5, 13.0 and 15.0 cm based on maximum length (L_max), TL vs. GSI (%), TL vs. SL and logistic model, respectively. Monthly variations of GSI and maturation stages were confirmed in April to August as spawning season and June as peak spawning month. Fulton’s condition factor (K_F) was found to be with significant relations with GSI values. Fecundity was 1,730 to 23,870 and significantly correlated with both TL and BW. Temperature has been increasing 0.029 °C/year with the falling of rainfall at 2.96 mm/year in the study area. Environmental factors -Temperature, rainfall, dissolved oxygen and pH were found to be significantly correlated with GSI. We found the optimal range of temperature (29–31 °C), rainfall (350–380 mm), dissolved oxygen (5.0–6.0 mg/l) and pH (7.1–7.5) for spawning of H. fossilis. The paper recommended the policy guidelines to pave the ways of the aquaculture, conservation and management of H. fossilis in the changing eco-climatic events through specific management measures.     

Biotic context and soil properties modulate native plant responses to enhanced rainfall

Background and Aims The environmental and biotic context within which plants grow have a great potential to modify responses to climatic changes, yet few studies have addressed both the direct effects of climate and the modulating roles played by variation in the biotic (e.g. competitors) and abiotic (e.g. soils) environment.Methods In a grassland with highly heterogeneous soils and community composition, small seedlings of two native plants, Lasthenia californica and Calycadenia pauciflora, were transplanted into factorially watered and fertilized plots. Measurements were made to test how the effect of climatic variability (mimicked by the watering treatment) on the survival, growth and seed production of these species was modulated by above-ground competition and by edaphic variables.Key Results Increased competition outweighed the direct positive impacts of enhanced rainfall on most fitness measures for both species, resulting in no net effect of enhanced rainfall. Both species benefitted from enhanced rainfall when the absence of competitors was accompanied by high soil water retention capacity. Fertilization did not amplify the watering effects; rather, plants benefitted from enhanced rainfall or competitor removal only in ambient nutrient conditions with high soil water retention capacity.Conclusions The findings show that the direct effects of climatic variability on plant fitness may be reversed or neutralized by competition and, in addition, may be strongly modulated by soil variation. Specifically, coarse soil texture was identified as a factor that may limit plant responsiveness to altered water availability. These results highlight the importance of considering the abiotic as well as biotic context when making future climate change forecasts.     

苏南丘陵区毛竹林冠截留降雨分布格局

降雨穿过林冠层时,由于林冠的拦截作用,改变了降雨分布格局。林冠截留是一个复杂的水文过程,受降水特征及林分特性的影响较大。本文以北亚热带苏南丘陵地区人工毛竹林(Phyllostachys edulis)为研究对象,利用2007年度各场次降雨观测数据,分析了降雨量和降雨强度与林冠截留降雨的关系,研究了林冠截留过程的特点。结果表明：（1） 研究期间共观测到102次降水事件,降水总量为1110.8mm,单次最大降雨量为110.0㎜,最小为0.55㎜,事件平均降水量为10.89mm,且绝大部分降雨为低雨强、中雨量级的降雨事件。（2） 研究期间林冠截留总量为171.72mm,占同期降雨总量的15.46%。单次林冠截留量变幅为0.21—4.55mm,截留率变幅为1.3%—100%,且随林外降雨量的递增,林冠截留率呈现递减的变化趋势,二者的关系用幂函数（I0=117.34P-0.9106）拟合效果较好。（3）在林外次降雨量小于5㎜的条件下,事件降雨量占年降雨总量的5.0%,相应的降雨事件频率为9.8%,此时林冠截留量随降雨量的增大而增加,其变幅为0.55—1.9㎜,截留量与降雨量的关系用对数函数（I=0.4931Ln(P) 0.9493）进行拟合效果较好;在单场降雨量大于5㎜时,林冠截留量随各场次降雨量的增加,其变动幅度和频率均大大增强,变化范围在0.21—4.55㎜之间,二者相关性较差。（4）降雨在7—10mm雨量级范围内时,林外降雨量和林冠截留量分别为245.14mm和47.9㎜,占其全年总量的比例均为最大,分别为22.07%和27.9%;各雨量级林冠平均截留量与平均降雨量的关系表现为对数函数关系（R2=0.7287）,而截留率与平均降雨量的关系表现为极显著的幂函数关系（R2=0.9817）,且林冠对降雨的截留作用在雨量级较小时,表现十分显著。（5）全年单场降雨强度小于0.06mm/min时,降雨事件频数为73.53%,降雨量占其总量的57.93%,林冠截留量占其总量的89.34%,降雨事件平均截留率（23.84%）远高于雨强大于0.06mm/min时的降雨事件平均截留率（3.92%）。本研究结果为长江中下游丘陵山区水土保持林和水源涵养林体系建设提供了理论依据。     

Using genetic analysis to determine the distribution,prevalence and diversity of Eimeria species in pest rabbits (Oryctolagus cuniculus) in Australia

To genetically assess the Australian distribution and frequency of Eimeria species in wild rabbits, with a primary focus on Eimeria intestinalis and Eimeria flavescens as possible additional agents of rabbit biocontrol, the distal colon and faecal samples from wild rabbits sourced from 26 Australian locations with mean annual rainfalls of between 252 mm and 925 mm were analysed using amplicon sequencing of the ITS1 region. Contrary to previous microscopy studies which had only detected E. flavescens on mainland Australia at Wellstead in south-west Western Australia, we detected this species at all 23 effectively sampled sites. The more pathogenic E. intestinalis was only found at 52.2% of sites. Three unique Eimeria genotypes were detected that did not align to the 11 published sequences using a pairwise-match threshold of 90%, and may represent unsequenced known species or novel species. One genotype we termed E. Au19SH and was detected at 20 sites, E. Au19CO was detected at eight sites, and E. Au19CN was detected in one rabbit at Crows Nest (Qld). Site diversity ranged from only five Eimeria species at Boboyan (ACT) to 13 unique sequences at Cargo (NSW). Eimeria diversity in individual rabbits ranged from 11 unique sequences in a rabbit at Wellstead (WA) and a rabbit at Cargo (NSW), to one in 17 rabbits and zero in six rabbits. The three rabbit age classes averaged 4.3 Eimeria species per rabbit. No relationship was found between the number of Eimeria species detected and mean annual rainfall. As Eimeria species were found to be fairly ubiquitous at most sites they appear to be an unlikely additional candidate to assist the control of pest rabbits in Australia.