伴生有金雀花、黑麦草的辐射松幼苗Allophanic土壤磷肥驱动的各磷形态变化

对盆栽的伴生有金雀花(Cytisus scoparius)、黑麦草(Lolium multiflorum)的辐射松(Pinus radiata)幼苗施用3种浓度(O,50,100 μg·g-1)的三过磷酸钙,14个月后测定缺磷Allophanic土壤中各磷形态变化,确定根际土壤中施加的磷肥的去向.结果表明,施加磷肥增加了根际土壤中NaOH-Pi、NaOH-P0和H2SO4-Pi的浓度,但是减少了土壤残留磷的含量,而树脂磷浓度维持不变,在这种土壤中树脂磷浓度仍然较低(1 to 3μg·g-1).施加到土壤里的磷肥,有机磷的回收率最高(40%-49%),这是因为这种土壤具有较高的磷固定能力(92%),其次是不稳定有机磷(7%-19%).在磷肥缺乏或不施加磷肥的情况下,辐射松根际土壤中有机磷浓度低于周边土壤以及金雀花、黑麦草根际土壤.这可能与磷肥缺乏条件下,根系和菌根产生较高的草酸盐而释放部分磷到根际土壤中有关.但此观点需要进一步的研究检验.     

磷肥诱导下层植被伴生的辐射松苗生长、磷素营养和土壤有效磷变化

通过在温室条件下施加不同剂量的重过磷酸钙(0,50和100mg·kg-1P),对典型水铝英石土壤(Orthic Allophanic Soil)的土壤植物有效磷、磷素营养和伴生有金雀花(Cytisus scoparius)或黑麦草(Lolium multiflorum)的辐射松苗木生长变化情况进行了研究。结果表明,施加磷肥增强了辐射松根际和磷素匮乏土体的有效磷。与辐射松苗伴生的金雀花、黑麦草根际土壤有效磷也增加。辐射松新枝和老枝松针、茎和根系中磷含量随施加重过磷酸钙剂量的增加而增加;但是金雀花、黑麦草对辐射松苗磷素营养的影响依赖于土壤磷状态。未施肥处理下,与金雀花伴生的辐射松新枝和老村松针、茎和根系中磷含量要高于与黑麦草伴生的辐射松苗,而施肥处理下,结果相反。这可能与金雀花生长大量消耗土壤中有效磷有关。因为,在两个施肥剂量(50mg·kg-1P和100mg·kg-1P)上,与金雀花伴生的辐射松根际土壤中Bray-2磷含量始终低于与黑麦草伴生的辐射松根际土壤。此外,在施肥浓度100mg·kg-1下,与金雀花伴生的辐射松苗干特质量低于黑麦草伴生的辐射松。说明在中、高施肥水平,辐射松苗与黑麦草伴生生长好于与金雀花伴...     

Relationships between foliar phosphorus fractions of Pinus sylvestris var. mongolica and soil available phosphorus

In order to find out the best foliar diagnostic index of phosphorus (P) nutrition in Mongolian pine (Pinus sylvestris var. mongolica) in the southeastern Keerqin Sandy Lands, the concentrations of total nitrogen (N), inorganic P, organic P and total P in needles of different ages and soil available P were examined. The results show that in the study area, soil available P was rather low (0.12–0.63 mg/kg) and was significantly correlated with inorganic P (cPi) and total P (cPt) concentrations in current year needles of Mongolian pine. The significant correlation between soil available P and needle cPt derived from the significant correlation between cPi and cPt. Compared with cPt, cPi did reflect the level of soil P supply more accurately and more directly. __________ Translated from Chinese Journal of Applied Ecology, 2008, 19(3): 494–498 [译自: 应用生态学报]     

Soil properties under a Pinus radiata – ryegrass silvopastoral system in New Zealand. Part II. C and N of soil microbial biomass, and soil N dynamics

At present, our understanding of the dynamics of microbial biomass and soil N in silvopastoral systems is very limited. In this paper, the effects of understorey management on soil microbial C and N, net N mineralization, and net nitrification were studied in two seven-year-old radiata pine (Pinus radiata D. Don) – pasture systems, consisting of plots with and without ryegrass (Lolium perenne) as an understorey. Mini-plots (1 × 1 m) with animals excluded and herbage repeatedly clipped and removed were used for soil sampling. Three mini-plots formed a transect at each of two positions: 0.9 and 3.5 m north of the tree rows. Measurements were taken from July 1997 to June 1998 about once every 40 days. One composite sample was collected from each of two sampling depths (0–10 and 10–20 cm) at each transect position on each sampling date. Temporal and spatial variability of N mineralization rates and microbial biomass C and N was large. Net mineralization and nitrification rates were higher in the bare ground than in the ryegrass plots for a major part of the year, particularly from late spring to early fall. Net N mineralization and nitrification rates were higher in the 0–10 than in the 10–20 cm soil layers in both the ryegrass and bare ground treatments; however, the depth effect on microbial biomass C and N was only significant in the ryegrass treatment. In the surface soil layer, microbial biomass C and N were substantially greater in the ryegrass than in the bare ground plots. Soil microbial properties and activities were closely linked to pasture root activities, soil depth, and site biophysical conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Organic acid exudation from the roots of Cunninghamia lanceolata and Pinus massoniana seedlings under low phosphorus stress

Organic acid exudation from the roots of Chinese fir (Cunninghamia lanceolata) and Masson pine (Pinus massoniana) seedlings under low phosphorus stress was studied using the solution culture method. The results revealed that organic acid exudation from the roots of Chinese fir and Masson pine seedlings under low phosphorus stress increased. Compared with P₃ (KH₂PO₄, 0.5 mmol/L), the average organic acid exudation from the root of Masson pine seedlings under P₀ (KH₂PO₄, 0 mmol/L), P₁ (KH₂PO₄, 0.03 mmol/L) and P₂ (KH₂PO₄, 0.09 mmol/L) increased by 328.6%, 267.9% and 126.4% respectively. Masson pine from Zhejiang Province in China had the highest organic acid exudation. Under low phosphorus stress, the increase in organic acid exudation from the different provinces of Chinese fir and Masson pine varied. Masson pine from Zhejiang Province mainly increased oxalic acid, tartaric acid, citric acid and malic acid exudation, that from Guangxi Province mainly increased oxalic acid and tartaric acid exudation, and that from Guizhou Province, China mainly increased oxalic acid, tartaric acid and malic acid exudation. Chinese fir mainly increased oxalic acid and tartaric acid exudation. __________ Translated from Journal of Nanjing Forestry University, 2007, 31(2): 9–12 [译自: 南京林业大学学报]     

Phosphorus fertiliser source and weed control effects on growth of three-year-old second-rotation Pinus radiata on Orthic Pumice soil in New Zealand

Little information is available on the interactive effects of soluble and less-soluble phosphorus (P) fertilisers and weed control on growth and P nutrition of second-rotation Pinus radiata plantations. A study was initiated on three-year-old second-rotation P. radiata and to determine the relationship between needle P concentrations and soil P forms in an Orthic Pumice soil two years after application. Four rates of P (0, 50, 100, and 200 kg P ha^?1) were applied as two forms of P fertiliser sources (triple superphosphate [TSP] and Ben-Guerir phosphate rock [BGPR]) in combination with weed control (weedy and weed-free). The results showed that the applied TSP and BGPR can increase tree needle P concentrations even when the needle P concentrations before fertiliser application were marginally higher than the critical P concentrations. The application of P fertilisers had no effect on tree growth during the two-year period of the trial, though it increased P. radiata needle P concentrations. However, the weed removal increased tree height, diameter at breast height, and basal area. In this plantation site the higher needle P concentrations than the critical P concentration suggests that the growth increase due to weed removal treatment was probably due to an increase in the availability of soil water and nutrients other than P. The needle P concentrations of P. radiata can be predicted by soil tests, Bray-2 P, Olsen P, resin-P_i, and NaOH-P_i tests. Of these soil tests, Bray-2 P seems to be the best test in predicting soil P availability to P. radiata. The P concentrations in the needles had a relationship with the NaOH-P_i fraction but had no relationship with the H₂SO₄-P_i fraction. These results suggest that P. radiata was probably taking up P mainly from the pool of P-adsorbed to allophane and Fe+Al oxides (NaOH-P_i) in this high P-fixing acidic soil.     

Role of weeds in the management of nitrogen in a young Pinus radiata plantation

Pinus radiata trees were grown on a podzolized sandy soil at a second rotation site under the following treatments: total weed control, total weed control plus ammonium nitrate, strip weed control and no weed control. During the first two summers after planting the differences in needle water potential between trees under no, strip or total weed control were very small. Despite similar rates of net N-mineralization in strip and total weed control treatments, which averaged 64 kg ha^–1 yr^–1 in the 0–15 cm soil depth, weeds in the strip weed control treatment reduced soil mineral-N concentrations by 50–80%, leaching of N by the end of the first growing season by 45%, foliar-N concentrations by 4–14% and stem biomass at 20 months after planting by 46%. Although N-uptake by above-ground vegetation (trees plus weeds) was 49% higher in the strip weed control treatment, the amount of N apportioned to trees during the first 20 months after planting was reduced from 15.5 to 9.0 kg ha^–1. These effects of weeds were even more pronounced in the no weed control treatment. Since weeds had little effect on the needle water potential of trees and the annual rates of N-mineralization, but adversely affected N-uptake by trees, results indicate that weeds directly competed with trees for N, and thereby aggravated N-deficiency in trees. Application of ammonium nitrate after complete weed control increased foliar-N concentrations, and N-uptake and growth of trees, but also induced severe stem deformation.     

In vitro ectomycorrhizal formation of Pinus patula, P. pseudostrobus, P. oocarpa and P. elliotii grown in southern India

In vitro syntheses of ectomycorrhizas of Pinus patula, P. pseudostrobus, P. oocarpa and P. elliotii with Amanita muscaria, Laccaria fraterna, L. laccata, Pisolithus tinctorius, Rhizopogon luteolus, Scleroderma citrinum and Thelephora terrestris were attempted. Most of the fungi initiated mycorrhizal formation within 2 weeks after inoculation. Laccaria fraterna and S. citrinum formed mycorrhizas after 6 weeks of inoculation. Amanita muscaria failed to form mycorrhizas during the 12 week period of observation. The degree of colonization of different mycorrhizal fungi varied with different species of Pinus.     

Root growth and hydraulic conductivity of southern pine seedlings in response to soil temperature and water availability after planting

Comparison of the root system growth and water transport of southern pine species after planting in different root-zone environments is needed to guide decisions regarding when, and what species to plant. Evaluation of how seed source affects root system responses to soil conditions will allow seed sources to be matched to planting conditions. The root growth and hydraulic conductivity of three sources each of shortleaf, loblolly and longleaf pine seedlings were evaluated for 28 days in a seedling growth system that simulated the planting environment. Across species, an increase in root-zone temperature alleviated limitations to root growth caused by water stress. In the coldest temperature, longleaf pine maintained a higher hydraulic conductivity compared to shortleaf and loblolly pine. Without water limitation, the root growth and hydraulic conductivity of shortleaf and loblolly pine were superior to that of longleaf pine, but as water availability decreased, the root growth of longleaf pine surpassed that of loblolly pine. Hydraulic conductivities of the seed sources differed, and differences were attributed to either new root growth, or an increase in the efficiency of the root system to transport water.     

Photosynthetic induction responses of Pinus koraiensis seedlings grown in different light environments

The time processes of photosynthetic induction responses to various irradiances in Korean pine (Pinus koraiensis) seedlings grown in open-light environments and in understory of forest were studied in an area near the Research Station of Changbai Mountain Forest Ecosystems, Jilin Province, China from July 15 to August 5, 1997. The results showed that at 200 μmol·m⁻²·s⁻¹ photosynthetic photon flux density (PPFD) and 500 μmol·m⁻²·s⁻¹ PPFD, the induction time for the photosynthetic rates of understory-grown seedlings to reach 50% and 90% steady-state net photosynthetic rates was longer than that of the open-grown seedlings. The induction responses of open-growth seedlings at 500 μmol·m⁻²·s⁻¹ PPFD were slower than those at 200 μmol·m⁻²·s⁻¹ PPFD, but it was the very reverse for understory-growth seedlings, which indicates that the photosynthetic induction times of Korean pine seedlings grown in the understory depended on the sunfleck intensity. Biograph: ZHOU Yong-bin (1970-), female, associate professor of Shenyang Agricultural University, Shenyang 110161, P.R. China. Responsible editor: Song Funan     

滇中云南松根际土与非根际土磷的有效性

测定云南松根际土和非根际土的全磷、有机磷、有效磷、pH值、酸性、中性、碱性磷酸酶活性.结果表明:根际土与非根际土之间的全磷和有机磷含量差异不显著,而有效磷含量差异极显著.根际土pH值极显著地低于非根际的.酸性、中性磷酸酶活性占总酶量的比例较大,碱性磷酸酶的较小.根际土的3种磷酸酶的含量极显著地高于非根际土的.根际活化磷的能力与土壤中的总磷含量、有机磷含量以及pH值和碱性磷酸酶的数量成显著正相关关系,这表明磷的活化是多因素共同作用的结果.不同林龄的云南松根际对磷的活化有一定差异,年龄小的云南松根际土与非根际土之间的有效磷差异较大.     

Microenvironmental heterogeneity of physical soil properties in a broad-leaved Pinus koraiensis forest gap

Microenvironmental heterogeneity of soil physical properties in 0–20 cm and 20–40 cm soil layers in a broad-leaved Pinus koraiensis forest gap in Xiao Xing’anling Mountains were analyzed by geostatistical method. The results show that the amount of soil water, saturation water capacity, capillary water capacity and porosity in the top layer were greater than those in the lower layer, except for bulk density, where the opposite applied. Soil physical properties in the top soil layer had relatively higher ranges and coefficients of variation. The total and auto correlation spatial heterogeneity of soil physical properties in the top layer were larger than those in the lower layer. The soil water had a strong anisotropic structure in an easterly and northerly direction, but porosity shows isotropy in the same directions. With increasing spatial distance, the other three physical factors exhibited anisotropic structures. The mutual effect between semi-variograms of soil physical properties in the top layer within the spatial autocorrelation range was not significant. For spatial distribution of physical properties within different layers, the patches at the middle and lower ranks in the forest gap dominated. Patches at higher rank were only distributed in the 0–20 cm soil layer and were located north of the forest gap center. __________ Translated from Science of Soil and Water Conservation, 2007, 5(3): 52–58 [译自: 中国水土保持科学]     

Seasonal response of soil enzyme activity to thinning intensity of aerial seeded Pinus tabulaeformis stands

Aerial seeding is one of the most important vegetation restoration patterns in remote hilly areas, and studies concerning soil quality and its management have practical value. In 2000, a study of the effect of thinning intensities at five different treatments levels, 0 (CK), 30% (slight thinning), 48.75% (medium thinning), 53.75% (intense thinning) and 65.6% (super intense thinning) on soil enzyme activity was carried out on 9-year-old aerial seeded Chinese pine (Pinus tabulaeformis Carr.) stands with an initial density of 8000 trees/hm², in the Wang-jiapu Aerail Seeding Center, Yanqing County, Beijing. Five years later, the activities of five kinds of soil enzymes, soil urease, alkaline phosphatase, inertase, catalase and polyphenol oxidase in the first 20 cm of soil layer were compared during four seasons. Relationships among soil enzymes and soil physiochemical properties were also analyzed to examine the possibility of using soil enzymes to evaluate thinning intensities. The results showed that the maximum enzyme activities of catalase and polyphenol oxidase occurred in June, those of soil urease and alkaline phosphatase occurred in October, and soil invetase had its maximum in April. In addition, the five soil enzymes were affected differently by thinning intensities. Soil catalase, urease and invertase showed the highest response to a slight thinning, followed by medium thinning, which is the opposite experienced with polyphenol oxidase and alkaline phosphatase. There are statistically significant and positive relationships between soil enzymes and organic matter and available K. It should be noted that soil water was a limiting factor to soil enzyme activity. Compared with soil physicochemical characteristics, soil enzymes were more sensitive to levels of thinning intensities. Among the enzymes, soil alkaline phosphatase and catalase could be regarded as indicators to assess soil quality. It is concluded that a suitable thinning intensity benefits the development of undergrowth and soil enzymes. Generally, when the stand with initial density of 8000 trees/hm² grows up to nine years old, the most suitable thinning intensity should be about 50%. __________ Translated from Journal of Beijing Forestry University, 2008, 30(2): 82–88 [译自: 北京林业大学学报]     

Microelement contents of litter, soil fauna and soil in Pinus koraiensis and mixed broad-leaved forest

The Mn, Zn and Cu contents of litter, soil fauna and soil in Pinus koraiensis and mixed broad-leaved forest in Liangshui Nature Reserve of Xiaoxing’an Mountains were analyzed in this paper, results showed that the tested microelement contents in the litter, soil fauna and soil followed the order: Mn>Zn>Cu, but varied with environmental components, for Mn the order is soil>litter>soil fauna, for Zn is soil fauna>litter and soil, and for Cu is soil fauna>soil>litter. The change range of the tested microelement contents in litter was larger in broad-leaved forest than those in coniferous forest. Different soil fauna differed in their microelementenrichment capability, the highest content of Mn, Zn and Cu existed in earthworm, centipede and diplopod, respectively. The contents of the tested microelements in soil fauna had significant correlations with their environmental background values, litter decomposition rate, food habit of soil fauna, and its absorbing selectively and enrichment to microelements. The microelements contained in 5–20 cm soil horizon were more than those in 0–5 cm humus layer, and their dynamics differed in various horizons. __________ Translated from Chinese Journal of Applied Ecology, 2007, 18(2): 277–282 [译自: 应用生态学报]     

Seasonal changes of understorey herbage yield in relation to light intensity and soil moisture content in a Pinus pinaster plantation

The relationship of understorey herbage yield with light intensity and soil moisture content was investigated in a 20-year-old Pinus pinaster plantation in Kilkis of Macedonia, northern Greece, in three seasons (fall, winter and spring). The plantation was thinned at three density levels, high, medium and low (2500, 1750 and 1000 trees/ha respectively) and it was seeded with Dactylis glomerata. In addition, two fertilization levels (0 and 110 N+150 P₂O₅ kg/ha) and grazing intensity levels (0 and 0.8 sheep/ha/yr) were applied in a split-split plot experimental design. It was found that herbage yield was highest in the ungrazed and fertilized low tree density stands in all seasons. In the medium tree density stand, although light was lacking, fertilized plots produced higher herbage yield as compared to unfertilized low tree density stands while fertilization is of no use in close stands if herbage production is the goal. Animals seemed to prefer fertilized and medium density stands. Third degree polynomial equations were the best to explain herbage variation through the seasons both in fertilized and unfertilized plots.     

Effects of light radiation intensity on photosynthetic characteristics and water use efficiency of Platycladus orientalis and Pinus tabulaeformis seedlings

In order to offer a scientific basis for cultivation and management of forests, effects of light radiation intensity on photosynthetic characteristics and water use efficiency of Platycladus orientalis and Pinus tabulaeformis were studied under different soil moisture contents. By adopting artificial control methods to soil moisture, and under simulated photosynthetic radiation (SPR), the net photosynthetic rate (P _N), transpiration rate (T _r), water use efficiency (WUE) and intercellular CO₂ concentration (C _i) of Platycladus orientalis and Pinus tabulaeformis in the semi-arid region of the Loess Plateau, were studied. Results are as follows: within the photon range of 0–2,200 μmol/(m²·s), P _N, T _r and WUE were enhanced with an increase in SPR in both species. P _N and WUE of Platycladus orientalis and Pinus tabulaeformis, however, declined with continued increase in SPR. P _N, T _r, WUE and light saturation point (LSP) of Platycladus orientalis were higher than those of Pinus tabulaeformis, while light compensation point (LCP) of Platycladus orientalis was lower than that of Pinus tabulaeformis at the same soil moisture content. The efficiency of light energy utilization of Platycladus orientalis was higher than that of Pinus tabulaeformis; P _N, T _r and C _i of Platycladus orientalis and Pinus tabulaeformis were enhanced by increasing soil moisture content, whereas WUE declined. At soil moistures of 7.90%, 13.00% and 19.99%, LSP of Platycladus orientalis was 1,275, 1,450 and 1,675 μmol/(m²·s) respectively, and LCP was 42, 25 and 13 μmol/(m²·s) respectively, with corresponding maximal net CO₂ photosynthetic rates (P _max) of 3.04, 4.06 and 5.53 μmol/(m²·s). At soil moistures of 7.83%, 13.04% and 20.15%, the LSP of Pinus tabulaeformis was 1,100, 1,325 and 1,500 μmol/(m²·s) respectively, and LCP was 60, 30 and 23 μmol/(m²·s), with P _max of 1.08, 3.35 and 4.36 μmol/(m²·s) respectively. __________ Translated from Science of Soil and Water Conservation, 2006, 4(3): 108–113 [译自: 中国水土保持科学]     

Benefit-cost analysis of raising Pinus wallichiana seedlings in different capacities/sizes of root trainers in the nursery

Modern nursery methods of seedling production in different sized root trainers, were compared by raising seedlings of Pinus wallichiana involving costs incurred and benefits received. In order to provide a common basis for the comparisons, the study involved the raising of 1000 seedlings annually on a continuous basis for seven years. A relative economic analysis of raising P. wallichiana seedlings in 300, 150 and 100 cm³ root trainers was carried out and we estimated that the root trainers of 300 cm³ capacity recorded the highest total input cost of Rs. 35571 and Rs. 40018 for 1000 seedlings produced annually at discount rates of 12% and 6%. Seedlings raised in 100 cm³ root trainers recorded the lowest total input cost of Rs. 23390 and Rs. 27737 per 1000 seedlings annually at discount rates of 12% and 6%. Hence, returns per rupee invested in raising seedlings in the 100 cm³ root trainers accounted for the maximum benefit-cost ratio (i.e., 1.56 and 1.61) at discount rates of 12% and 6%. Thus seedlings raised in 100 cm³ and 150 cm³ root trainers were found to be most cost effective when compared with seedlings grown in 300 cm³ root trainers. The results can be attributed to the larger number of cells per tray (higher growth density) in the 100 and 150 cm³ root trainers, compared to the number of seedlings in the 300 cm³ root trainers.     

Soil properties in forest gaps and under canopy in broad-leaved Pinus koraiensis forests in Changbai Mountainous Region, China

The species composition and diversities, and soil properties under canopy gaps in broad-leaved Pinus koraiensis forests were studied in the Changbai Mountains. The results indicated that the species composition and diversities in gap were different from those under canopy. The Shannon-Wiener index, evenness index, and abundance index in gap were higher than those under canopy in the seedling layer, while the community dominance in the seedling layer increased in closed canopy. The physicochemical properties of soil changed with the change of space and resource availability in gaps. The thickness, standing crop, and water holding capacity of the litter layer under canopy were significantly (p<0.01) higher than those in gap. The content of total nitrogen and total potassium of litter in gap were 10.47% and 20.73% higher than those under canopy, however, the content of total phosphorus and organic carbon under canopy were 15.23% and 12.66% more than those under canopy. The water content of 0–10 cm and 10–20 cm of soil layer in gap were 17.65% and 16.17% more than those under canopy. The soil buck density of 0–10 cm were slightly higher under canopy than that in gaps, but there was no significant difference in the soil buck density of the 10–20 cm soil layer. The soil pH values were 5.80 and 5.85 in gap and under canopy, respectively, and were not significantly different. The content of soil organic matter, total nitrogen, and total potassium in gap were 12.85%, 7.67%, and 2.38% higher than those under canopy. The content of NH₄ ⁺-N, available phosphorus, available potassium, and total phosphorus in soil under canopy were 13.33%, 20.04%, 16.52%, and 4.30% higher than those in gap. __________ Translated from Forest Research, 2006, 19(3): 347–352 [译自: 林业科学研究]     

滇中高原云南松天然林和人工林土壤呼吸特征的比较

以云南磨盘山国家森林公园云南松天然林和人工林为研究对象,采用LI-6400-09便携式土壤呼吸室对土壤呼吸速率进行连续定位观测。结果表明:(1)两种林分的土壤呼吸速率具有明显的季节变化,均呈单峰曲线趋势;云南松天然林土壤呼吸速率在1.58~4.23μmol·m-2s-1之间,变异幅度为2.68;人工林土壤呼吸速率在1.13~3.34μmol·m-2s-1之间,变异幅度为2.96。(2)土壤呼吸速率的季节变化与不同层次土壤含水量均显著正相关(p0.05),而与不同层次土壤温度的相关性仅在云南松人工林达到显著水平。(3)双因素关系模型拟合结果表明,土壤温度和含水量共同解释了云南松天然林和人工林土壤呼吸速率的80.8%~93.0%和84.2%~85.9%。(4)两种林分土壤呼吸速率与土壤有机质含量相关性不显著(p0.05),土壤全氮含量仅与云南松天然林土壤呼吸相关性显著(R2=0.712,p0.05),而土壤水解氮含量对两林分土壤呼吸的影响均达到显著水平(p0.05),土壤C/N则与两林分呈极显著(p0.01)的负相关关系。因此,与天然林相比,人工林土壤温度、湿度及土壤C、N养分含量等土壤环境因子都存在变化,从而导致云南松天然林和人工林土壤呼吸速率时空变化的差异性。     

Scion-rootstock relationships with respect to height growth and foliar concentrations of nitrogen and phosphorus in reciprocal grafts of Pinus caribaea var. hondurensis

Both scion and rootstock clones significantly influenced scion elongation and concentrations of nitrogen and phosphorus in the scion foliage. Scion clone was the more important determinant. Scion clone × rootstock clone interactions were not significant. The ability of a clone to elongate as a scion was not correlated with its capacity to promote or retard scion elongation when used as a rootstock. Genetic differences in foliar nutrient concentrations appeared to reflect levels of nutrient demand, rather than the ability of roots to absorb nutrients. Nutrient demand of the rootstock can also explain negative correlations between nitrogen levels in rootstock clones and levels of both nitrogen and phosphorus in the scions. There was no significant relationship between scion elongation and foliar nitrogen concentrations of either rootstock or scion. The weak relationship between scion elongation and concentration of phosphorus in the rootstock apparently resulted from tissue dilution.