Effects of nitrogen on leaf physiology and growth of different families of loblolly and slash pine

Leaf physiology and fractional dry weight allocation were examined in four open-pollinated families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Englm. var. elliottii) in response to growth under low and high N supply for six months. Nitrogen greatly influenced dry weight allocation, total mass, leaf net photosynthesis and leaf conductance in seedlings of both species. Family variation in fine root allocation was observed under low but not high N treatment, but for the majority of physiological and growth traits, family variation was stable under varying N treatment. Family rankings based on juvenile height, diameter and biomass accretion were similar to rankings based on field performance at 22 years in slash pine but not loblolly pine. Lower leaf maintenance respiration rates were associated with families exhibiting the most rapid juvenile growth.     

Integrating within-crown variation in net photosynthesis in loblolly and slash pine families

We examined photosynthetic characteristics of two fast- and two slow-growing half-sib families of both loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii var. elliottii Engelm.) on two sites in northern Florida to: (1) quantify variation in light-saturated net photosynthesis (Amax) associated with vertical crown position and foliage age; (2) quantify the amount and distribution of leaf area by foliage age class; and (3) determine whether photosynthetic indices, ranging from leaf-level through whole-crown Amax, were related to growth differences among species and families. In both species, leaf-level Amax was higher in more recently formed foliage both within the same year (where Amax in the third flush averaged 10 to 30% higher than Amax in the first flush) and between years (where Amax in current-year foliage averaged 20 to 40% higher than Amax in 1-year-old foliage). When expressed on a leaf area basis, Amax of current-year foliage was higher in slash pine than in loblolly pine, but Amax expressed on a mass basis did not differ between species. Loblolly pine had higher whole-tree leaf area than slash pine, whereas whole-tree Amax did not differ between species. When the mean values for fast-growing families were compared with the mean values for slow-growing families, there were no differences in leaf-level characteristics, whereas at the whole-tree level, fast-growing families had higher leaf area and whole-tree Amax than slow-growing families in both species. When comparisons were made among the individual fast- and slow-growing families, however, results were more variable. In both species, stem volume growth was strongly correlated with whole-tree Amax, with most of the strength of the correlation deriving from the relationship between volume growth and tree leaf area.     

应用遥感、人工神经网络叶面积模型和模拟过程模型估计湿地松人工林碳储量

全球气候变化引起人们对森林碳固定作用的关注。碳存储速率依赖于生态系统流通量(光合作用和生态系统呼吸),量化为净生态系统二氧化碳交换。在没有密集采样点的情况下,我们需要采用估测森林净生态系统交换的方法准确地估计林分水平和更大尺度的碳固定量。本文通过祸合遥感估算的叶面积指数和生长过程拟合模型,估计了佛罗里达州内9 770公顷湿地松人工林一年里净生态系统交换总量。地面图神经网络模型和陆地卫星数据估计的森林叶面积指数平均值是1.06(数值范围0-3.93,包括森林边界)。输入神经网络叶面积指数值,湿地松拟合模型(SPM2)估计的森林净生态交换值在-5.52 Mg·hm-2·a-1到11.06Mg·hm-2·a-1之间,平均值是3.47 Mg·hm-2·a-1。年总的碳储量是33920t,约合3.5 t/hm2。估计的叶面积指数和森林净生态交换均对对施肥高度敏感。图3表1参30。     

Thinning,fertilization, and crown position interact to control physiological responses of loblolly pine

To examine physiological responses to thinning, fertilization, and crown position, we measured net photosynthesis (P(n)), transpiration (E), vapor pressure difference (VPD), stomatal conductance (g(s)), and xylem pressure potential (Psi(1)) between 0930 and 1130 h under ambient conditions in the upper and lower crowns of a 13-year-old loblolly pine (Pinus taeda L.) plantation six years (1994) after the treatments were applied. Photosynthetic photon flux density (PPFD) and air temperature (T(a)) within the canopy were also recorded. Needle P(n) of thinned trees was significantly enhanced by 22-54% in the lower crown, because canopy PPFD increased by 28-52%. Lower crown foliage of thinned plots also had higher E and g(s) than foliage of unthinned plots, but thinning had no effect on needle Psi(1) and predawn xylem pressure potential (0430-0530 h; Psi(pd)). Tree water status did not limit P(n), E and g(s) during the late-morning measurements. Fertilization significantly decreased within-canopy PPFD and T(a). Needle Psi(1) was increased in fertilized stands, whereas P(n), E and g(s) were not significantly altered. Upper crown foliage had significantly greater PPFD, P(n), VPD, g(s), E, and more negative Psi(1) than lower crown foliage. In both crown positions, needle P(n) was closely related to g(s), PPFD and T(a) (R(2) = 0.77 for the upper crown and 0.82 for the lower crown). We conclude that (1) silvicultural manipulation causes microclimate changes within the crowns of large trees, and (2) needle physiology adjusts to the within-crown environmental conditions.     

Characterization of the induced response of slash pine to inoculation with bark beetle vectored fungi

Six 25- to 30-year-old slash pine, Pinus elliottii Englm. var. elliottii, trees were inoculated with Ophiostoma minus (Hedgc.) H.P. Sydow, O. ips (Rumb.) Nannf or sterile water. Two, 4 and 6 weeks after inoculation, the lengths of developing lesions and the monoterpene concentration of the necrotic tissue within each lesion were measured. Both sterile and fungal wounding resulted in the development of lesions in the phloem-outer xylem. At both 4 and 6 weeks after inoculation, lesions induced by O. minus were significantly larger than lesions induced by O. ips or sterile water, whereas the lesions induced by O. ips and sterile water were similar in size at all sampling periods. At 2, 4 and 6 weeks after inoculation, lesions induced by O. minus had significantly greater concentrations of monoterpenes than lesions induced by O. ips or sterile water. The monoterpene concentration of lesions induced by O. ips was significantly greater than that of lesions induced by sterile water only at the 6-week sampling period. Visual examination of the lesions indicated that O. minus but not O. ips was inhibiting the development of callus tissue, suggesting that the strain of O. ips was either nonpathogenic or avirulent.     

Leaf traits in relation to crown development, light interception and growth of elite families of loblolly and slash pine

Crown architecture and size influence leaf area distribution within tree crowns and have large effects on the light environment in forest canopies. The use of selected genotypes in combination with silvicultural treatments that optimize site conditions in forest plantations provide both a challenge and an opportunity to study the biological and environmental determinants of forest growth. We investigated tree growth, crown development and leaf traits of two elite families of loblolly pine (Pinus taeda L.) and one family of slash pine (P. elliottii Mill.) at canopy closure. Two contrasting silvicultural treatments -- repeated fertilization and control of competing vegetation (MI treatment), and a single fertilization and control of competing vegetation treatment (C treatment) -- were applied at two experimental sites in the West Gulf Coastal Plain in Texas and Louisiana. At a common tree size (diameter at breast height), loblolly pine trees had longer and wider crowns, and at the plot-level, intercepted a greater fraction of photosynthetic photon flux than slash pine trees. Leaf-level, light-saturated assimilation rates (A(max)) and both mass- and area-based leaf nitrogen (N) decreased, and specific leaf area (SLA) increased with increasing canopy depth. Leaf-trait gradients were steeper in crowns of loblolly pine trees than of slash pine trees for SLA and leaf N, but not for A(max). There were no species differences in A(max), except in mass-based photosynthesis in upper crowns, but the effect of silvicultural treatment on A(max) differed between sites. Across all crown positions, A(max) was correlated with leaf N, but the relationship differed between sites and treatments. Observed patterns of variation in leaf properties within crowns reflected acclimation to developing light gradients in stands with closing canopies. Tree growth was not directly related to A(max), but there was a strong correlation between tree growth and plot-level light interception in both species. Growth efficiency was unaffected by silvicultural treatment. Thus, when coupled with leaf area and light interception at the crown and canopy levels, A(max) provides insight into family and silvicultural effects on tree growth.     

Photosynthesis, water relations, and growth of planted Pinus strobus L. on burned sites in the southern Appalachians

We measured net photosynthesis, leaf conductance, xylem water potential, and growth of Pinus strobus L. seedlings two years after planting on two clear-cut and burned sites in the southern Appalachians. Multiple regression analysis was used to relate seedling net photosynthesis to vapor pressure deficit, seedling crown temperature, photosynthetically active radiation (PAR), needle N, xylem water potential, and soil water, and to relate seedling size and growth to physiological measurements (average net photosynthesis, leaf conductance, and cumulative xylem water potential), soil water, needle N, seedling temperature, and PAR. Seedling net photosynthesis was significantly related to vapor pressure deficit, midday water potential, crown temperature, and PAR (r(2) = 0.70) early in the growing season (May 1992) with vapor pressure deficit alone explaining 42% of the variation. As neighboring vegetation developed, light became more limiting and significantly reduced seedling net photosynthesis later in the growing season (July, August, and September). Final seedling diameter was significantly related to competitor biomass, average photosynthetic rate, and needle N (r(2) = 0.68).     

湿地松等5树种在太湖滩地造林耐淹水性比较试验

在太湖滩地用湿地松、美国白蜡、水杉、池杉和柳树（对照）进行了不同树种、不同区域、不同淹水期和不同淹水深度的耐水湿对比造林试验。在淹水深度20～60．5cm、连续淹水时间达40d时观察结果为：①湿地松和柳树（对照）的成活率分别为99．7％和99．5％;美国白蜡、水杉和池杉的成活率分别为19．5％,30．2％和31．1％。②在太湖滩地湿地松表现与柳树（对照）一样,生长势和生长量一切正常,湿地松为常绿树种,病虫害较少,从绿化、美化和景观考虑,建议湿地松作为太湖滩地造林树种之一,并建议作为我国太湖地区淡水森林湿地植被恢复与重建的的适生树种之一。     

Temporal and spatial patterns of net photosynthesis in 12-year-old loblolly pine five growing seasons after thinning

Physiological parameters were measured under natural light conditions and needle orientation from towers and walkways erected in the canopy of a loblolly pine (Pinus taeda L.) plantation. Four silvicultural treatments were randomly assigned to the twelve plots in the fall of 1988. Plots were thinned to a density of 731 trees per hectare or left unthinned, at a density of 2990 trees per hectare. The plots were left unfertilized or fertilized with 744 kg/ha of diammonium triple superphosphate was applied. During the fifth growing season (1993) following thinning and fertilization, needle level physiology was not different with respect to the thinning treatment for fertilized or unfertilized plots. In contrast, upper crown levels within the fertilized and unfertilized plots had significantly higher light levels and photosynthetic rates than lower crown foliage. Light levels were greater in the thinned, fertilized plots than in the unthinned, fertilized plots. In contrast, no effect of thinning on canopy light levels was found in the unfertilized plots. Within crown variation in photosynthesis was strongly dependent on canopy light levels. A strong interaction of canopy level with thinning was apparent for net photosynthesis. Loblolly pine, being a shade intolerant species, showed only small physiological differences between needles from different parts of the crown. Because of the variability found in this study, more extensive sampling is needed to correctly describe the physiology of a forest canopy with adequate precision.     

Aluminum sensitivity of loblolly pine and slash pine seedlings grown in solution culture

To probe variation in Al sensitivity of two co-occurring pine species, seedlings from six full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were grown in solution culture containing 4.4 mM (high-Al) or 0.01 mM (low-Al) AlCl(3) at pH 4 for 58 days. On average, both pine species had 41% less total dry weight in the high-Al treatment than in the low-Al treatment. Stem volume growth of slash pine was more sensitive to the high-Al treatment than that of loblolly pine. In both species, the high-Al treatment inhibited root dry weight more than shoot dry weight. Within-species variation in Al sensitivity among families was greater in loblolly pine (24 to 52% inhibition of seedling dry weight) than in slash pine (35 to 47% inhibition of seedling dry weight). Foliar Al concentration was positively correlated with Al sensitivity in slash pine but not in loblolly pine; however, in both species, the concentration of Al in roots was 20-fold greater than in foliage.     

测土配方施肥对湿地松生长与养分含量及其土壤肥力的影响

选择4年生湿地松优良家系试验林,通过测土配方施肥,研究其对湿地松生长与叶片、枝条养分含量及其土壤肥力的影响。结果表明:施肥后第2年,土壤全P含量与湿地松树高及胸径生长呈现极显著正相关,其数学模型分别为:y=-5.944 4 x+1.318 9、y=-7.500 0 x+2.700 0;施肥后土壤中速效K含量与叶片中全K含量呈现极显著正相关,其数学模型为:y=0.010 8 x-0.163 3;速效K含量与湿地松树高及胸径生长,其数学模型分别为:y=-0.032 8 x+1.513 3、y=-0.047 4 x+3.002 9;土壤中全N增长与湿地松叶片全N含量增长均呈现显著正相关,其数学模型为:y=7.016 1 x+0.162 1。湿地松平均树高与胸径相较于未施肥的对照组增幅分别达11%与13%以上,其差异达到了极显著水平。     

Effects of carbon dioxide, fertilization, and irrigation on photosynthetic capacity of loblolly pine trees

Branches of nine-year-old loblolly pine trees grown in a 2 x 2 factorial combination of fertilization and irrigation were exposed for 11 months to ambient, ambient + 175, or ambient + 350 micro mol mol(-1) CO(2). Rates of light-saturated net photosynthesis (A(max)), maximum stomatal conductance to water vapor (g(max)), and foliar nitrogen concentration (% dry mass) were assessed monthly from April 1993 until September 1993 on 1992 foliage (one-year-old) and from July 1993 to March 1994 on 1993 foliage (current-year). Rates of A(max) of foliage in the ambient + 175 CO(2) treatment and ambient + 350 were 32-47 and 83-91% greater, respectively, than that of foliage in the ambient CO(2) treatment. There was a statistically significant interaction between CO(2) treatment and fertilization or irrigation treatment on A(max) on only one measurement date for each age class of foliage. Light-saturated stomatal conductance to water vapor (g(max)) was significantly affected by CO(2) treatment on only four measurement dates. Light-saturated g(max) in winter was only 42% of summer g(max) even though soil water during winter was near field capacity and evaporative demand was low. Fertilization increased foliar N concentration by 30% over the study period when averaged across CO(2) treatments. During the study period, the ambient + 350 CO(2) treatment decreased average foliar N concentration of one-year-old foliage in the control, irrigated, fertilized and irrigated + fertilized plots by 5, 6.4, 9.6 and 11%, respectively, compared with one-year-old foliage in the corresponding ambient CO(2) treatments. The percent increase in A(max) due to CO(2) enrichment was similar in all irrigation and fertilization treatments and the effect persisted throughout the 11-month study period for both one-year-old and current-year foliage.     

Integration of pines and pastures for hay and grazing

When combining pine and cattle production on improved pastures, grazing may have to be delayed for several years until trees are large enough to resist injury. During this period forage would be lost unless harvested for hay. This study in south Georgia, USA, examined hay production during the first 3 years, cattle production during the next 3 years, and effects of this management system on survival and growth of slash pine(Pinus elliottii) planted in widely-spaced rows within the pastures. Pines were planted at 225 trees/ha in configurations of 3.0 x 14.6 or 4.9 x 9.1 m in pastures recently sprigged or seeded with Coastal bermudagrass (Cynodon dactylon) or Pensacola bahiagrass(Paspalum notatum). Pastures were fertilized annually and cut for hay four or five times each year. Wide-row spacings permitted haying operations, but tree rows and turning areas removed 5 to 8 percent of the area from production. However, hay yields and liveweight gains by yearling cattle were near normal for this locale. Slash pine planted in these fertilized pastures survived well, grew rapidly, and only a few trees were killed during haying operations. After 6 years, 83 percent of the trees survived and averaged 6.5 m in height and 13.2 cm in diameter. Cattle killed a few trees by rubbing during the 4th year. Wide-row spacing of pines permits harvesting forage for hay while waiting for the trees to become large enough to permit grazing. This approach to agroforestry produces annual returns to the landowner while awaiting maturity of the pines.     

湿地松采脂试验报告

本试验以大田县桃源林场13年生的湿地松为材料,对湿地松产脂量、最佳采脂间隔期的选择、采脂对湿地松生长量的影响进行试验研究,并采用方差分析等方法,对湿地松7种不同处理方法进行差异显著检验,确定合理的采脂间隔期。结果表明,胸径17cm的湿地松平均单刀产脂量为32g;采脂间隔期3—5天,不仅产脂量较大,而且对湿地松生长量影响小。     

松材线虫侵染对松树苯丙氨酸解氨酶及酚类物质的影响

以湿地松（Pinus elliottii Engelm）、日本黑松（Pinus thunbergii Parl）为材料,研究松材线虫[Bursaphelenchus xylophilus（Steiner＆Buhrer,1934）Nickle]感染对苯丙氨酸解氨酶和酚类物质的影响.两种松树的苯丙氨酸解氨酶的活性在发病过程中都有明显增加,并且伴随着酶活性的变化,各种苯丙烷次生代谢产物,如总酚、类黄酮的含量也发生明显的变化.但湿地松在苯丙氨酸解氨酶活力和酚类物质的积累上的变化比黑松要大些.结果表明,松材线虫病的发生、发展与寄主植物苯丙氨酸解氨酶活性和酚类物质含量变化有关.     

湿地松黄化病和叶枯病的发生与防治

湿地松黄化病和叶枯病,前者属生理性病害,后者属侵染性病害,两者间的互相作用,使湿地松正常生长受阻。该文对湿地松黄化病和叶枯病的发生原因进行了调查,提出了相应的防治措施和要求。     

Aluminum fractions in root tips of slash pine and loblolly pine families differing in Al resistance

Aluminum (Al) distribution among several cellular fractions was investigated in root tips of seedlings of one Al-resistant and one Al-sensitive family of slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) grown in nutrient solution containing 100 microM AlCl3 (pH 4) for 167 h. Aluminum present in 5-mm-long root tips was fractionated into cell-wall-labile (desorbed in 0.5 mM citric acid), cell-wall-bound (retained after filtering disrupted cells through 20-microm mesh) and symplasmic (filtrate following cell disruption) fractions. When averaged across both species, 12% of Al absorbed by root tips appeared in the symplasmic fraction and 88% in the apoplasmic fraction (55% as cell-wall-labile, and 33% as cell-wall-bound). On a fresh mass basis, total Al in root tips was lower in loblolly pine than in slash pine, lower in the Al-resistant slash pine family than in the Al-sensitive slash pine family, and lower in the Al-resistant families than in the Al-sensitive families across species. Although the data support the hypothesis that Al-resistant plants limit Al uptake to root apices, they do not exclude other mechanisms of Al resistance. Differential Al resistance between the species and between slash pine families may also be associated with the size of the total non-labile and cell-wall-labile Al fractions, respectively. We were unable to identify the basis for differential Al resistance in loblolly pine.     

湿加松优良家系丰产林生长表现

利用广东省湿加松良种选育协作组研制的14个优良杂种家系的扦插苗木在广东省台山市红岭种子园内营建试验示范林7 hm2,利用优良杂种家系的混合扦插苗木在广东省台山市赤溪镇营建丰产林120hm2。试验示范林5.5年生时的数据表明,优良家系扦插苗木的树高、胸径、材积生长可达到6.69 m,11.31cm,0.03603 m3,其材积生长比作为对照的湿地松、洪都拉斯加勒比松分别大136.59%,15.49%;3.5年生的丰产林的平均树高、胸径、材积分别为3.50 m,5.62 cm,0.0054 m3,材积生长比作为对照的湿地松大350%。该结果充分显示了湿加松优良家系的生长优势,说明湿加松可在广东中南部地区通过扦插扩繁、大量推广。     

Effect of elevated carbon dioxide concentration and root restriction on net photosynthesis, water relations and foliar carbohydrate status of loblolly pine seedlings

To determine the effects of CO(2)-enriched air and root restriction on photosynthetic capacity, we measured net photosynthetic rates of 1-year-old loblolly pine seedlings grown in 0.6-, 3.8- or 18.9-liter pots in ambient (360 micro mol mol(-1)) or 2x ambient CO(2) (720 micro mol mol(-1)) concentration for 23 weeks. We also measured needle carbohydrate concentration and water relations to determine whether feedback inhibition or water stress was responsible for any decreases in net photosynthesis. Across all treatments, carbon dioxide enrichment increased net photosynthesis by approximately 60 to 70%. Net photosynthetic rates of seedlings in the smallest pots decreased over time with the reduction occurring first in the ambient CO(2) treatment and then in the 2x ambient CO(2) treatment. Needle starch concentrations of seedlings grown in the smallest pots were two to three times greater in the 2x ambient CO(2) treatment than in the ambient CO(2) treatment, but decreased net photosynthesis was not associated with increased starch or sugar concentrations. The reduction in net photosynthesis of seedlings in small pots was correlated with decreased needle water potentials, indicating that seedlings in the small pots had restricted root systems and were unable to supply sufficient water to the shoots. We conclude that the decrease in net photosynthesis of seedlings in small pots was not the result of CO(2) enrichment or an accumulation of carbohydrates causing feedback inhibition, but was caused by water stress.