Sap flow of the major tree species in the eastern mountainous region in northeast China

This study is based on Quercus mongolica, Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica, Tilia amurensis, and Pinus koraiensis trees of the same age (12 years) and seedling origin under the same site conditions. The sap flow density, water consumption, and related environmental factors were also measured using thermal dissipation method and ICT-2000TE (Transpiration-Environment) automatic measuring system for tree transpiration and environmental factors. On clear days during the growing season, the sap flow density exhibited mono-peak diurnal patterns, mostly between 10:00 and 14:00, except for Phellodendron amurense, whose sap flow showed two peaks during the daytime three times. The photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) were the major factors influencing diurnal changes in sap flow, which explained 60%–74% variations in sap flow density for all species except Phellodendron amurense. Maximum sap flow densities for F. mandshurica, Phellodendron amurense, Q. mongolica, J. mandshurica, T. amurensis, and Pinus koraiensis were 516.36, 234.00, 625.93, 945.83, 507.93, and 286.21 cm³/(cm²·h), in July, June, September, August, August, and July, respectively. Water consumption during the whole growing season for J. mandshurica, T. amurensis, F. mandshurica, Pinus koraiensis, Phellodendron amurense, and Q. mongolica was 3,840, 2,820, 2,710, 2,120, 1,470, and 1,390 kg/sapling, respectively. __________ Translated from Scientia Silvae Sinicae, 2005, 41(3): 36–42 [译自: 林业科学, 2005, 41(3): 36–42]     

Sap flow of three co-occurring Mediterranean woody species under varying atmospheric and soil water conditions

We studied the seasonal patterns of water use in three woody species co-occurring in a holm oak forest in northeastern Spain. The three species studied, Quercus ilex L., Phillyrea latifolia L. and Arbutus unedo L., constitute more than 99% of the total basal area of the forest. The study period included the dry seasons of 1999 and 2000. Water use was estimated with Granier-type sap flux sensors. Standard meteorological variables, soil water content and leaf water potentials were also monitored. All monitored individuals reduced leaf-related sap flow (Q(l)) during the summer, concurrent with an increase in soil moisture deficit (SMD). Despite similar maximum Q(l) between species, the decline in Q(l) with increasing SMD was species-dependent. The average reduction in Q(l) between early summer and the peak of the drought was 74% for A. unedo (n = 3), 58% for P. latifolia (n = 3) and 87% for Q. ilex (n = 1). The relationship between canopy stomatal conductance (G(s)) and vapor pressure deficit (D) changed during the course of the drought, with progressively lower G(s) for any given D. Summertime reductions of Q(l) and G(s) were associated with between-species differences in vulnerability to xylem embolism, and with the corresponding degree of native embolism (lowest in P. latifolia and highest in Q. ilex). Our results, combined with previous studies in the same area, outlined differences among the species studied in manner of responding to water shortage, with P. latifolia able to maintain water transport at much lower water potentials than the other two species. In an accompanying experiment, A. unedo responded to an experimental reduction in water availability by reducing Q(l) during the summer. This species also modified its water use between years according to the different seasonal patterns of precipitation. These results are discussed in relation to the possible impacts that climate change will have on Q. ilex-dominated forests.     

Impact of artificial afforestation on the regional water supply balance in Southwest China

Ecological degradation is a key factor limiting sustainable development. Artificial afforestation has chiefly been used to combat it, especially in China. In order to contain rocky desertification and ecological and environmental degradation in Southwest China, the Government of China has planted 6000 km² of trees in this region since the year 2000. Yet, the resultant water consumption of artificial afforestation has had a significant influence on water resource supplies in Southwest China, and its internal mechanisms remain largely unclear. Studies in Southwest China have shown that artificial afforestation has degraded the natural water balance in Yunnan Province because of the elevated evapotranspiration levels associated with manmade forests. Accordingly, such increases in evapotranspiration have disturbed the water resource balance of the region. It is been suggested that natural restoration practices should therefore be encouraged in this region or plants that consume less water should be grown in place of artificial afforestation. This study sheds some light on the cycles of local water resources and the stimulus of climate change to access ways by which to afforest Yunnan Province sustainably and successfully. It also presents a strong argument on how to use water resources to enable vegetation construction initiatives in Yunnan Province while avoiding potential ecological risks.     

Variation in soil water uptake and its effect on plant water status in Juglans regia L. during dry and wet seasons

Temporal and spatial variations in the water status of walnut trees (Juglans regia L.) and the soil in which they were growing were traced by analyzing the differences in hydrogen isotopes during spring and summer in a 7-year-old walnut stand. Walnut root dynamics were measured in both dry and wet seasons. Walnut roots were mainly distributed in the upper soil (0-30 cm depth), with around 60% of the total root mass in upper soil layers and 40% in deep soil layers (30-80 cm depth). The upper soil layers contributed 68% of the total tree water requirement in the wet season, but only 47% in the dry season. In the wet season, total roots, living roots and new roots were all significantly more abundant than in the dry season. There were significant differences in pre-dawn branch percentage loss of hydraulic conductance (PLC), pre-dawn leaf water potential and transpiration between the dry and wet seasons. Water content in the upper soil layers remarkably influenced xylem water stable-hydrogen isotope (δD) values. Furthermore, there were linear relationships between the xylem water δD value and pre-dawn branch PLC, pre-dawn leaf water potential, transpiration rate and photosynthetic rate. In summary, J. regia was compelled to take a larger amount of water from the deep soil layers in the dry season, but this shift could not prevent water stress in the plant. The xylem water δD values could be used as an indicator to investigate the water stress of plants, besides probing profiles of soil water use.     

Sap flow characteristics of neotropical mangroves in flooded and drained soils

Effects of flooding on water transport in mangroves have previously been investigated in a few studies, most of which were conducted on seedlings in controlled settings. In this study, we used heat-dissipation sap probes to determine if sap flow (J(s)) attenuates with radial depth into the xylem of mature trees of three south Florida mangrove species growing in Rookery Bay. This was accomplished by inserting sap probes at multiple depths and monitoring diurnal flow. For most species and diameter size class combinations tested, J(s) decreased dramatically beyond a radial depth of 2 or 4 cm, with little sap flow beyond a depth of 6 cm. Mean J(s) was reduced on average by 20% in Avicennia germinans (L.) Stearn, Laguncularia racemosa (L.) Gaertn. f. and Rhizophora mangle L. trees when soils were flooded. Species differences were highly significant, with L. racemosa having the greatest midday J(s) of about 26 g H(2)O m(-2) s(-1) at a radial depth of 2 cm compared with a mean for the other two species of about 15 g H(2)O m(-2) s(-1). Sap flow at a depth of 2 cm in mangroves was commensurate with rates reported for other forested wetland tree species. We conclude that: (1) early spring flooding of basin mangrove forests causes reductions in sap flow in mature mangrove trees; (2) the sharp attenuations in J(s) along the radial profile have implications for understanding whole-tree water use strategies by mangrove forests; and (3) regardless of flood state, individual mangrove tree water use follows leaf-level mechanisms in being conservative.     

Occurrence of Bursaphelenchus species in declining Pinus sylvestris in a dry Alpine valley in Switzerland

We determined the incidence of Bursaphelenchus species in declining Pinus sylvestris stands in the Swiss Alps. A total of 217 trees showing different degree of decline were sampled from various locations in Valais between 2001 and 2004. Bursaphelenchus species were only found in recently dead or dying trees with an overall incidence of 40%. There was a positive relationship between Bursaphelenchus infestation and blue stain in these trees. Five Bursaphelenchus species were identified: Bursaphelenchus vallesianus, Bursaphelenchus mucronatus, Bursaphelenchus sexdentati, Bursaphelenchus leoni and Bursaphelenchus silvestris. The most frequent species were B. vallesianus detected in 75% and B. mucronatus in 20% of all Bursaphelenchus‐positive trees. Bursaphelenchus vallesianus is a recently described species within the B. sexdentati group, and could be a contributing factor in the observed pine decline in Valais.     

干热河谷地带麻疯树主要病虫害调查

对我国干热河谷地带麻疯树Jatropha curcas重点分布区和主要栽培区的22个县市进行了病虫害调查,共鉴定出8种主要病害和7种主要虫害.对大面积栽种的麻疯树可能造成极大损失的潜在危险性病虫害及防治进行了分析与探讨.     

不同施肥处理对3种海岛树种苗木生长及造林效果的影响

为了解不同施肥处理对普陀樟(Cinnamomum japonicum var.Chenii)、全缘冬青(Ilex integra Thunb.)、红楠(Machilus thunbergii Sieb.et Zucc)3种海岛树种苗木生长及造林效果的影响,设置了7个不同的施肥处理,即(1)N(对照),(2)N+P,(3)N+2P、(4)N+K、(5)N+2K、(6)N+1P+1K、(7)N+2P+2K,于2011年5月至2012年1月观测苗高和地径,并测定植物各部分的生物量。结果表明:3种苗木不同施肥处理下,通过测算苗木质量指数QI可知,在N+1K施肥组合下,全缘冬青的苗木质量最好,而红楠在N+2P+2K的施肥组合下苗木质量最高,普陀樟在N+1P+1K的施肥组合下,苗木质量要好于其他处理。     

3个南方造林树种幼苗抗旱性的比较

以聚乙二醇（ＰＥＧ－６０００）渗透溶液模拟水分胁迫的条件下，比较了不同水分胁迫强度和同一胁迫强度条件下银杏，侧柏，火炬松等树种幼苗的抗旱性，并确定了３个鉴定苗木早期抗旱性的生理指标，结果表明３个树种幼苗抗旱性的顺序为：侧柏〉银杏〉火炬松。质膜相对透性，相对含水量（ＲＷＣ）根系活力等指标可以作为快速，简便鉴定苗木早期抗旱性的生理指标。     

谈三北地区植树造林、低产林和森林经营问题

三北地域广阔，是我国造林绿化的重点地区。必须充分那里植树造林难度，积极改造低产林分，合理经营好现有林，追求和创造森林的全面高效益。     

Investigating light-use efficiency across a jack pine chronosequence during dry and wet years

Light-use efficiency (LUE) is the ability of vegetated canopies to use light for photosynthesis. Together with remote sensing estimates of canopy cover and meteorological inputs, LUE provides a physical basis for scaling carbon uptake processes from the stand to the global scale. A better understanding of the factors that control LUE will result in improved global estimates of carbon uptake from the terrestrial biosphere. To examine factors that control variability in LUE in stands of different ages during dry and wet conditions, we measured LUE in a chronosequence of four jack pine stands (recent clearcut (age 1-3), regenerating (age 8-9), immature (age 29-30) and mature (~90 years old)) during one normal (2002), one very dry (2003) and two very wet (2004, 2005) growing seasons in Saskatchewan, Canada. Cumulative CO(2) fluxes decreased significantly at all sites during the drought year of 2003, as did mean LUE. Canopy foliage at the recently regenerating jack pine site increased by 19% between 2002 and 2003. Foliage growth rate was reduced by 6% between 2003 and 2004, and foliage biomass decreased by 6% from 2004 to 2005. Over the four years studied, LUE was greatest at the mature jack pine site and lower, but similar, at the other three sites. Mean growing-season LUE varied with mean soil water content at each site, except at that of the newly regenerating stand where soil water had little influence. Mean daily vapor pressure deficit typically had the greatest influence on variability in LUE at all sites. Diffuse versus direct radiation also had significant but varying effects on LUE in jack pine stands of different ages.     

Structure and regeneration dynamics of dominant tree species along altitudinal gradient in a dry valley slopes of the Bhutan Himalaya

The aim of our study was to characterize the structure and regeneration dynamics of dominant tree species along altitudinal gradient in dry valley slopes of the Bhutan Himalaya. In the typical dry valley slopes of west-central Bhutan, we analyzed forest stratification, tree crown projection, and population structure from lower dry valley bottom (1520 m a.s.l.) to upper humid ridge top (3370 m a.s.l.) across five major forest types: i.e. (1) dry pine forest with Pinus roxburghii as a dominant species; (2) mixed broad-leaved forest with Quercus lanata (evergreen), Quercus griffithii, (deciduous), and Rhododendron arboreum (evergreen) as major canopy species; (3) evergreen broad-leaved forest dominated by Quercus semecarpifolia, Quercus glauca and Quercus oxyodon; (4) cool conifer forest dominated by Abies densa and Tsuga dumosa; (5) cold conifer forest with A. densa and Juniperus recurva as dominants. In general, regeneration pattern of major dominant species shifted from inverse-J (lower altitudes), to sporadic (mid-altitudes), and to uni-modal type (upper altitudes) corresponding to three regeneration trends: (1) invasive at the lower, warm, dry forest under relatively strong human disturbances; (2) stable/balanced at the mid-altitude, in a relatively stable, mature moist evergreen broad-leaved forest with gap regeneration; and (3) poor/low regeneration at the upper, cool, humid conifer forest with a continuously cattle-grazed understory. Overall, regeneration patterns were balanced in all forest types, however care should be taken to prevent excessive exploitation of dry pine forest of lower valley bottom, and to control cattle grazing at higher altitudes. Our findings can be incorporated into management plans for sustainable management and conservation of mountain forests.     

干热河谷造林技术及措施探讨

介绍了干热河谷的自然条件和成因．分析了植被恢复过程中面临的自然和社会的挑战．探讨了相应的针对自然因素的造林技术措施和针对社区群众有效的工作、管理方法。     

Influence of three plant species with different morphologies on water runoff and soil loss in a dry-warm river valley, SW China

Understanding of the effects of isolated plants with different morphologies on water runoff and soil loss is important for vegetation restoration in arid environments. We selected three representative species (Artemisia gmelinii; Ajania potaninii; Pulicaria chrysantha) of the dry-warm river valley of the upper reach of Minjiang River, SW China to examine these effects. Twenty-five runoff events were recorded using runoff plots at micro scale (<40 cm × 40 cm) on a south facing slope from July through October 2006. A. potaninii had sparse canopy, the smallest leaf area (0.49 ± 0.25 cm²) and specific leaf area (67.8 ± 16.5 cm²/g), and the highest leaf relative water content (27.1 ± 4.4%). It is the most resistant to drought stress. A. gmelinii was the shortest, and had relatively small leaf area (0.55 ± 0.50 cm²) and the densest canopy. P. chrysantha had the greatest leaf area (1.41 ± 0.49 cm²) and most extended canopy (4450 ± 1646 cm²). Dead branches and leaves of A. gmelinii and P. chrysantha commonly fall and collect on the soil surface. Thus they had greater improvements on soil porosity and soil water content, and higher effectiveness in controlling soil loss. However, A. gmelinii had more stable effectiveness in controlling runoff as compared with P. chrysantha. The characteristics such as relatively small leaf area but low height and dense canopy might be one criterion for selecting species to improve soil properties and controlling runoff and soil loss. Differences in soil environments, and runoff and soil loss production capacity for micro-surfaces regulates water and materials redistribution, which emphasizes the importance in designing vegetation restoration pattern.     

Sap flow of birch and Norway spruce during the European heat and drought in summer 2003

In this study the hydrological regime of Norway spruce (Picea abies) and birch (Betula pendula) growing on heavy soils in the south east of Austria was analysed. Results from the year 2003 characterised by an extremely hot and dry summer are presented in this paper. Due to the extreme weather conditions the soil water content in August 2003 was very low (0.10–0.25 m³ m⁻³) in the topsoil (0–50 cm) with no explicit difference between both tree species.     

Water relations balance parameters of 30 woody species from Cerrado vegetation in the wet and dry season

IntroductionThehigherplantsmaintainingtheirorganstobetur-gidareveryimportantmechanism,inwhichtheaII-physiologicalprocesscouIdfonctionnorma1IyundertheIimitedWaerstress(MeinzeretaI1986).TheseasonadjustmentinWaterrelationofwoodyspeci-esottenoccursrespondingtothechangingenvi-ronmentaIconditionsinoFdertomaintainasoil-to-IeafwaterpotentiaIgradientandlowerthewiltingpointbyextendingtherangeofpositiveturgid(Ku-biske&Abrams1991).AlthoughtherewereaIOtofargumentsonthewaterreIationinpastdecades,pIa…     

Comparative regeneration ecology of three leguminous timber species in a Bolivian tropical dry forest

A comparative study of the regeneration ecology ofthree lesser-known leguminous timber species wasconducted in the seasonally dry forests of SantaCruz, Bolivia to determine species regenerationstrategies and make silvicultural recommendationsfor these species. The study included arepresentative from each subfamily of Leguminosae:Anadenanthera colubrina (Vell. Conc.) Benth.(Mimosaceae), Copaifera chodatiana Kunth.(Caesalpinaceae), and Centrolobium microchaeteC. Martius (Fabaceae). After production in themid-late dry season, seeds of all species sufferedhigh (>30%) rates of predation. For seedssurviving predation, Anadenanthera germinatedwithin three days after the first rains and a highgermination capacity (82%), but most seedlings diedfrom inadequate light or during subsequent periodsof drought. Copaifera germinated more slowlybut had high germination capacity (85%). Centrolobium had very low germination capacity(4%) and germinative energy. Most successfulregeneration of Centrolobium occurred viasprouting from damaged roots on or near loggingroads where it had a density of 261 root sprouts/ha.Anadenanthera regenerated best from seedin areas with soil disturbance or burning. Theregeneration of these species will likely increaseunder more intensive logging and/or post-harvestcompetition control treatments in logging gaps. Themore shade-tolerant Copaifera is most suitedto the current regime of light selective logging,but all three species are likely to be responsive topost-harvest competition control treatments. Impacts of controlled and natural fire were mixed,but generally seedling regeneration and growth wereeither not significantly affected or were increasedby fire.     

元谋干热河谷植被恢复的物种选择与营造技术

根据适地适树的原则，通过对造林立地条件的土壤分类及物种的生物学持性的分析研究，筛选出适宜不同立地类型的物种。在栽培试验的基础上，提出了栽培技术措施，尤其针对干热河谷的特殊气候条件，研究总结了因地制宜，分类整地，直播和容器育苗移植相结合，适时定植等营造技术。     

一些竹种在不同季节不定根诱导的形式

考察了季节和植物激素、非植物激素生长调节剂对不定根形成的影响,以进行黄竹、孝顺竹、马甲竹和龙竹无性繁殖。在冬天,夏天和雨季的3个生长季节,将成熟秆截取成单节扦插方式,并用IAA,IBA、NAA、硼酸和水进行24h处理。之后,将扦插秆水平放置,盖上沙子,在喷雾箱中放2个月。     

Between and within-site comparisons of structural and physiological characteristics and foliar nutrient content of 14 tree species at a wet,fertile site and a dry,infertile site in Panama

Structural and physiological characteristics and foliar nutrient content of 14 tree species were evaluated at two sites, one being seasonally wet with relatively fertile soils and the other being seasonally dry with relatively infertile soils. Differences in environmental stress between these sites drove the resulting differences in structural and physiological characteristics and leaf nutrient content of the investigated tree species. At the wet site, trees were more productive as site conditions allowed for greater photosynthetic activity to occur. The growth of pioneer tree species such as Spondias mombin, Guazuma ulmifolia, and Luehea seemanni, correlated strongly with high water-use efficiency and large, low-density leaves. Tree species, especially N-fixing species such as Albizia adinocephala, Albizia guachapele, Enterolobium cyclocarpum, and Gliricidia sepium, adapted to the greater levels of environmental stress at the dry site with infertile soils by increasing their water-use efficiency. Species differences were also significant, indicating that certain species adapted physiologically and structurally to environmental stress. Tree productivity operated under different structural and physiological constraints at each site. Leaf mass area (LMA), foliar N, and leaf area index (LAI) best predicted mass-based net photosynthetic capacity at the more fertile, wet site while foliar N was the best predictor of mass-based net photosynthetic capacity at the less fertile, dry site. Results from this study suggest the use of pioneer species at wet, fertile sites and N-fixing species at dry, infertile sites for restoration projects.