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1.
The efficiency of sample-based indices proposed to quantify the spatial distribution of trees is influenced by the structure of tree stands, environmental heterogeneity and degree of aggregation. We evaluated 10 commonly used distance-based and 10 density-based indices using two structurally different stands of wild pistachio trees in the Zagros woodlands, Iran, to assess the reliability of each in revealing stand structure in woodlands. All trees were completely stem-mapped in a nearly pure (40 ha) and a mixed (45 ha) stand. First, the inhomogeneous pair correlation function [g(r)] and the Clark–Evans index (CEI) were used as references to reveal the true spatial arrangement of all trees in these stands. The sampled data were then evaluated using the 20 indices. Sampling was undertaken in a grid based on a square lattice using square plots (30 m × 30 m) and nearest neighbor distances at the sample points. The g(r) and CEI statistics showed that the wild pistachio trees were aggregated in both stands, although the degree of aggregation was markedly higher in the pure stand. Three distance- and six density-based indices statistically verified that the wild pistachio trees were aggregated in both stands. The distance-based Hines and Hines statistic (h t ) and the density-based standardised Morisita (I p ), patchiness (IP) and Cassie (C A ) indices revealed aggregation of the trees in the two structurally different stands in the Zagros woodlands and the higher clumping in the pure stand, whereas the other indices were not sensitive enough. 相似文献
2.
Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta. However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on the shell ridge islands under extreme soil water stress. To evaluate the adaptability of plants to light and moisture variations under extreme soil moisture conditions present on these islands, we measured photosynthetic gas exchange process, chlorophyll fluorescence, and stem sap flow variables for 3-year-old trees of Tamarix chinensis Lour, a restoration species on these islands, subjected to three types of soil water levels: waterlogging stress (WS), alternating dry–wet (WD), and severe drought stress (SS) to inform decisions on its planting and management on shell ridge islands. Gas exchange, chlorophyll fluorescence, and stem sap flow in T. chinensis were then measured. Net photosynthetic rate (P N), transpiration rate (E), and water use efficiency (W UE) were similar under WS and alternating dry–wet conditions, but their mean E and W UE differed significantly (P < 0.05). Under SS, the P N, E and W UE of T. chinensis leaves varied slightly, and mean P N, E and W UE were all low. Apparent quantum efficiency (A QY), light compensation point (L CP), light saturation point (L SP), and maximum net photosynthetic rate (P Nmax) of leaves were not significantly different (P > 0.05) under WS and dry–wet conditions; however, under extreme drought stress, compared with the dry–wet conditions, L CP was higher, L SP was lower, and A QY and P Nmax were both at the lowest level. Therefore, drought stress weakened light adaptability of leaves, and the efficiency of light transformation was poorer. (3) Maximum photochemical efficiency (F v/F m) and the actual photochemical efficiency (Φ PSII) were similar under waterlogged stress and dry–wet conditions, indicating a similar healthy photosynthetic apparatus and photosynthetic reaction center activity, respectively. Under SS, F v/F m was 0.631, and the coefficient of non-photochemical quenching (N PQ) was 0.814, which indicated that while the photosynthetic mechanism was damaged, the absorbed light energy was mainly dissipated in the form of heat, and the potential photosynthetic productivity was significantly reduced. The daily cumulants of sap flow of T. chinensis under dry–wet alternation and severe drought stress were 22.25 and 63.97% higher, respectively, than under waterlogging stress. Daily changes in sap flow velocity for T. chinensis differed under the three soil water levels. Stem sap flow was weak at night under severe drought stress. Under dry–wet alternation, daytime average stem sap flow velocity was the highest, and night stem flow accounted for 10.26% of the day cumulants, while under waterlogged stress, the average nightly stem flow velocity was the highest, accounting for 31.82% of the day cumulants. These results provide important information for regional vegetation restoration and ecological reconstruction. 相似文献
3.
The effects of nitrogen (N), phosphorus (P) and N?+?P additions on the decomposition of green leaves and leaf litter were studied over 2 years using the litterbag technique in Acacia auriculaeformis stands with different densities in southern China. The green leaves and leaf litter were treated with four fertility treatments: control, N addition, P addition and N?+?P addition to test the effect of stand density and fertility on the decomposition of green leaves and leaf litter. The mean percentage of mass remaining (PMR) of green leaves and leaf litter significantly decreased with increasing density. Nitrogen and N?+?P additions had a negative effect on PMR, whereas the addition of P had a positive effect. The rapid decomposition of green leaves was associated with a higher N and P content and a lower N/P ratio, indicating a likely P limitation for A. auriculaeformis stands. Our results imply that stand density associated with canopy openness can impact litter decomposition, and P is an important control factor on litter decomposition in A. auriculaeformis stands. 相似文献
4.
Eric Gehring Bruno Bellosi Ambra Quacchia Marco Conedera 《Journal of pest science》2018,91(1):189-202
Dryocosmus kuriphilus has become a major issue for chestnut (Castanea sativa) cultivation since its introduction in Europe. Thus far, however, quantitative assessments of the impact of D. kuriphilus in terms of green biomass loss are lacking. In the present study, we used the leaf area to sapwood area relationship (A L:A S)—based on the pipe model approach as a green biomass indicator—to quantitatively estimate the damage to chestnut trees caused by D. kuriphilus attacks and its recovery when the pest is controlled by Torymus sinensis in the chestnut stands of southern Switzerland. Leaf area loss is used as a response variable to select the most suitable explanatory architectural features at branch level to be combined in a damage index that permits a realistic assessment covering the entire epidemic. In our case study, the peak of the epidemic was reached in the fourth year of repeated D. kuriphilus attacks (leaf area losses exceeding 70%) with significant alterations in branch architecture. Although damage symptoms first decreased once biological control was reached (fifth year), branch architecture recovery was still lacking. From a methodological point of view, our A L:A S approach highlights how traditional methods of assessing the degree of infestation (i.e. proportion of attacked buds) fail to give sound estimations of resulting damage, whereas the proposed composite damage index enables a more realistic assessment of the entire epidemic process, including the recovery phase when the gall wasp is biologically controlled. 相似文献
5.
Honglang Duan Guomin Huang Shuangxi Zhou David T. Tissue 《European Journal of Forest Research》2018,137(5):605-618
Knowledge regarding the interactive effects of elevated [CO2], warming and drought on dry mass production, allocation and water use efficiency (WUE) of tree seedlings is limited, particularly in trees exhibiting different stomatal regulation strategies. Seedlings of Callitris rhomboidea (relatively anisohydric) and Pinus radiata (relatively isohydric) were grown in two [CO2] (Ca (400 μmol mol?1) and Ce (640 μmol mol?1)) and two temperature (Ta (ambient) and Te (ambient?+?4 °C)) treatments in a sun-lit glasshouse under well-watered conditions prior to imposition of the drought. Ce increased mass production in C. rhomboidea (but not in P. radiata), while drought limited mass production in both species. Mass production was greatest in the combination of Ce, Te and well-watered conditions. Pinus radiata allocated relatively more dry mass into roots and had higher plant WUE than C. rhomboidea. Noticeably, mass allocation patterns in C. rhomboidea varied as a function of the treatments, but those of P. radiata were constant. Ce enhanced leaf WUE of both species, but to a greater degree under drought stress than well-watered conditions. Moderate drought stress increased both leaf and plant WUE compared to well-watered conditions. C. rhomboidea exhibited plasticity to variable climate conditions through morphological adjustments, while P. radiata exhibited a highly conservative strategy. Collectively, these findings indicate that the two species have different strategies in resource acquisition and utilisation under changing environmental conditions. Future studies on tree response to climate change need to fully consider the integration of species traits, including stomatal behaviour and hydraulic strategies. 相似文献
6.
Jarosław G. Paluch Zbigniew Kołodziej Jerzy Skrzyszewski Leszek Bartkowicz Piotr Gruba 《Annals of Forest Science》2016,73(4):1015-1024
Key message
In Abies alba Mill. stands and mixed stands of A. alba and Picea abies L. (H. Karst), microsites neighbouring the trunks of adult trees were more conducive to A. alba regeneration. Although at the stand level, the effect of Fagus sylvatica L. was positive; the local effect of the adult F. sylvatica neighbourhood was insignificant. Hence, forming mixed stands with a fine-grained mosaic of admixed species might better facilitate natural regeneration of A. alba than monospecific stands.Context
The establishment of natural regeneration in Abies alba Mill. stands is a slow, spatially heterogeneous and stochastic process. Recent studies based on inventory data indicate that A. alba more readily regenerates in mixed stands than in monospecific stands.Aims
The objective was to examine how this positive association evidenced at the stand level operates on the scale of microsites with contrasting local species composition and stand density.Methods
In 8 monospecific and 22 mixed stands with Fagus sylvatica L. or Picea abies L. (H. Karst), microsites with a contrasting density of A. alba seedlings were selected and compared in terms of local species composition, stand density, canopy characteristics and topsoil properties.Results
In A. alba stands, seedling density was positively associated with the proximity of adult trees. In mixed stands of A. alba and P. abies, adult trees of both species exerted a positive effect on A. alba regeneration, but the P. abies neighbourhood influenced regeneration occurrence more strongly than the A. abies neighbourhood. In mixtures with F. sylvatica, however, the effect of local stand density and local species composition was not evidenced at all.Conclusion
Although at the stand level, P. abies and F. sylvatica exert a positive effect on A. alba regeneration, on the microsite scale, their influences differ. In stands with a dominance of A. alba, the hampered seedling establishment in gaps may be considered an inhibitive effect that facilitates the emergence of other species.7.
The temporal phenology of leaf bud bursting, leaf initiation, leaf maturation, leaf fall, flower initiation, fruit initiation and fruit fall was recorded for eight tree species (Ficus hispida, F. squamosa, Mallotus nudiflorus, M. philippensis, Shorea robusta, Schleichera oleosa, Pongamia pinnata and Terminalia arjuna) in the tropical moist deciduous forest of Himalayan Terai region from November 2009 to October 2012. The study revealed that a short low temperature dry period, sufficient winter rain and temperature rise are the triggering factors for summer leaf flushing and, the increased soil water availability for second leaf flushing in rains. Initiation of flowering with leaf emergence in the dry period supports higher rate of fruit setting due to maximum availability and activities of pollinators. The dispersal and post dispersal success of fruits increased by their ripening before and/or in the rainy season. In T. arjuna, no correlation has been found between the fruiting and rains. M. nudiflorus and M. philippensis initiate leaves and flowers with the first significant increase in temperature and photoperiod and are thus suggested as the potential tree species for climate change studies in tropics. 相似文献
8.
Daniel Moreno-Fernández Fernando Montes Mariola Sánchez-González Francisco J. Gordo Isabel Cañellas 《European Journal of Forest Research》2018,137(1):17-27
The dynamics of mixed stands are more complex and less studied than those of monospecific stands. The objective of this work was to analyze the variables involved in seedling occurrence and seedling survival in mixed stands of Pinus pinaster and P. pinea in Mediterranean areas. From 2011 to 2016, regeneration of both species was monitored at two sites located in Central Spain. We installed 72 regeneration plots where seedling dynamics were monitored. All the trees in the study areas were measured and mapped. Additionally, we took hemispherical photographs in each regeneration plot. The average density of P. pinea seedlings over the study period was almost 20 times larger than that of P. pinaster. Our results indicate that the seedlings of both species grow under moderate light conditions. In addition, we found that the occurrence of seedlings of both species was related to the structure of the stand. P. pinea seedlings grew where the density and size of P. pinaster trees were low and where P. pinea trees provided moderately sheltered conditions, whereas the number of P. pinaster seedlings was related to under intermediate densities of P. pinaster trees. Furthermore, seedling survival was positively associated with age of the seedlings and negatively with the August average maximum temperature. The temporal continuity of mixed stands of P. pinea and P. pinaster in the study area is compromised by the observed lack of regeneration of P. pinaster. 相似文献
9.
Understanding the relationship between tree height (H) and diameter at breast height (D) is vital to forest design, monitoring and biomass estimation. We developed an allometric equation model and tested its applicability for unevenly aged stands of moso bamboo forest at a regional scale. Field data were collected for 21 plots. Based on these data, we identified two strong power relationships: a correlation between the mean bamboo height (H m) and the upper mean H (H u), and a correlation between the mean D (D m) and the upper mean D (D u). Simulation results derived from the allometric equation model were in good agreement with observed culms derived from the field data for the 21 stands, with a root-mean-square error and relative root-mean-square error of 1.40 m and 13.41 %, respectively. These results demonstrate that the allometric equation model had a strong predictive power in the unevenly aged stands at a regional scale. In addition, the estimated average height–diameter (H–D) model for South Anhui Province was used to predict H for the same type of bamboo in Hunan Province based on the measured D, and the results were highly similar. The allometric equation model has multiple uses at the regional scale, including the evaluation of the variation in the H–D relationship among regions. The model describes the average H–D relationship without considering the effects caused by variation in site conditions, tree density and other factors. 相似文献
10.
F. Santini J. P. Ferrio A.-M. Hereş E. Notivol M. Piqué L. Serrano T. A. Shestakova E. Sin P. Vericat J. Voltas 《European Journal of Forest Research》2018,137(6):863-878
Water and carbon fluxes in forests are largely related to leaf gas exchange physiology varying across spatiotemporal scales and modulated by plant responses to environmental cues. We quantified the relevance of genetic and phenotypic variation of intrinsic water-use efficiency (WUEi, ratio of net photosynthesis to stomatal conductance of water) in Pinus sylvestris L. growing in the Iberian Peninsula as inferred from tree-ring carbon isotopes. Inter-population genetic variation, evaluated in a provenance trial comprising Spanish and German populations, was low and relevant only at continental scale. In contrast, phenotypic variation, evaluated in natural stands (at spatial level) and by tree-ring chronologies (at temporal inter-annual level), was important and ten- and threefold larger than the population genetic variance, respectively. These results points to preponderance of plastic responses dominating variability in WUEi for this species. Spatial phenotypic variation in WUEi correlated negatively with soil depth (r?=???0.66; p?<?0.01), while temporal phenotypic variation was mainly driven by summer precipitation. At the spatial level, WUEi could be scaled-up to ecosystem-level WUE derived from remote sensing data by accounting for soil water-holding capacity (r?=?0.63; p?<?0.01). This outcome demonstrates a direct influence of the variation of leaf-level WUEi on ecosystem water and carbon balance differentiation. Our findings highlight the contrasting importance of genetic variation (negligible) and plastic responses in WUEi (large, with changes of up to 33% among sites) on determining carbon and water budgets at stand and ecosystem scales in a widespread conifer such as Pinus sylvestris. 相似文献
11.
Stomatal regulation plays a vital role related to plant functioning, especially with a limited water supply. Estimating the leaf stomatal conductance (g s) is pivotal for further estimation of transpiration as well as energy and mass balances between air and plant in arid regions. Based on successive measurements of leaf gas exchange of two typical desert riparian phreatophytes, Tamarix ramosissima Ledeb., and Populus euphratica Oliv., we estimated g s using the empirical, optimal, and mechanistic models. Measurements were conducted on T. ramosissima during the growing seasons in 2011 and 2012 and P. euphratica in 2013 and 2014. Estimated values were compared with those measured by the portable open-path gas exchange measurement system. Results indicated that Ye’s mechanistic model always performed best among all the g s models tested here with R 2 values of 0.878 and 0.723 for T. ramosissima in 2011 and 2012, and 0.625 and 0.867 for P. euphratica in 2013 and 2014, respectively. Meanwhile, Medlyn’s optimal model exhibited the least reliable performance with R 2 at values of 0.514 and 0.398 for T. ramosissima in 2011 and 2012, and 0.385 and 0.101 for P. euphratica in 2013 and 2014, respectively. Empirical models may not be suitable for application in novel situations because they have been developed from experimental observations rather than from any mechanistic understanding or theory of stomatal behavior. Consequently, the application of Ye’s mechanistic model will be of great significance for the modeling and up-scaling of g s in extremely arid regions in the future. 相似文献
12.
Joanna Mucha Andrzej M. Jagodziński Bartosz Bułaj Piotr Łakomy Adrian M. Talaśka Jacek Oleksyn Marcin Zadworny 《Annals of Forest Science》2018,75(1):22
Key message
Quercus robur seedling mass was affected more by planting density than by taproot pruning. Root pruning enhanced stem biomass at the expense of roots in later growth stages. Alteration of biomass allocation due to nursery practices may result in greater susceptibility to injury and death of the seedlings under unfavorable environmental conditions.Context
Plants adjust their growth and modulate the resource allocation in response to applied treatments and environmental conditions.Aims
The aim was to examine how taproot pruning in seedlings grown at different densities affected long-term growth of Quercus robur.Methods
Seedlings, sown as acorns at two planting densities, with or without pruned roots were harvested in the second, fourth, and fifth years of growth. The effect of root pruning on biomass allocation was determined by measuring leaf, stem, and root mass fractions; carbohydrate concentrations in the roots; and C/N ratios. Specific leaf area and root length were also determined to assess morphological adaptations to growth conditions.Results
Total seedling mass was affected more by planting density than by taproot pruning. After 4 years of growth, root mass fractions were lower and stem mass fractions were greater in seedlings planted at a higher density. Five-year old root-pruned seedlings also had a lower root mass fraction and higher stem mass fractions than unpruned seedlings. Specific root length was not affected by root pruning or planting density.Conclusion
Decrease of relative root biomass with simultaneous increase of stem biomass may be a long-term consequence of taproot pruning of Q. robur, and the effects may manifest years after the seedling stage.13.
We conducted a study to find out if arbuscular mycorrhizal (AM) fungi (Acaulospora scrobiculata, Scutellospora calospora) and phosphate solubilizing bacteria (PSB, Paenibacillus polymyxa) inoculation either individually or in combinations can improve Acacia auriculiformis seedling growth, uptake of nutrients and quality in a phosphorus deficient tropical Alfisol. The seedlings were assessed for various growth and nutrient uptake parameters after 60 days of treatment. Inoculation with P. polymyxa stimulated mycorrhizal formation. Seedling height, stem girth, taproot length, number of leaves and leaf area, plant dry matter production, nodulation, and nodular dry weight were significantly higher for seedlings that were either dual inoculated or triple inoculated compared to individual inoculation of AM fungi or PSB, and uninoculated seedlings. Dual and triple application of AM fungi and PSB also significantly improved the nutrient contents of shoots and roots and nutrient uptake efficiencies. The calculated seedling quality indexes of the AM fungi and PSB inoculated seedling were 25–208% higher than uninoculated seedlings. These findings show that A. auriculiformis seedlings when dual inoculated or triple inoculated performed better than seedlings inoculated with the microbes individually and compared with uninoculated control seedlings. We conclude that bioinoculation is important for the production of high-quality A. auriculiformis seedlings in tree nurseries for planting in nutrient deficient soils. 相似文献
14.
Pau Brunet-Navarro Frank J. Sterck Jordi Vayreda Jordi Martinez-Vilalta Godefridus M.J. Mohren 《Annals of Forest Science》2016,73(4):1025-1034
Key message
Self-thinning lines are species- and climate-specific, and they should be used when assessing the capacity of different forest stands to increase biomass/carbon storage.Context
The capacity of forests to store carbon can help to mitigate the effects of atmospheric CO2 rise and climate change. The self-thinning relationship (average size measure ～ stand density) has been used to identify the potential capacity of biomass storage at a given density and to evaluate the effect of stand management on stored carbon. Here, a study that shows how the self-thinning line varies with species and climate is presented.Aims
Our main objective is thus testing whether species identity and climate affect the self-thinning line and therefore the potential amount of carbon stored in living biomass.Methods
The Ecological and Forest Inventory of Catalonia was used to calculate the self-thinning lines of four common coniferous species in Catalonia, NE Iberian Peninsula (Pinus halepensis, Pinus nigra, Pinus sylvestris and Pinus uncinata). Quadratic mean diameter at breast height was chosen as the average size measure. The self-thinning lines were used to predict the potential diameter at a given density and study the effect of environmental variability.Results
Species-specific self-thinning lines were obtained. The self-thinning exponent was consistent with the predicted values of ?3/2 and ?4/3 for mass-based scaling for all species except P. sylvestris. Species identity and climatic variability within species affected self-thinning line parameters.Conclusion
Self-thinning lines are species-specific and are affected by climatic conditions. These relationships can be used to refine predictions of the capacity of different forest stands to increase biomass/carbon storage.15.
This study quantified variations within tree stems in tangential shrinkage (αT), radial shrinkage (αR), and tangential/radial shrinkage ratio (αT/αR) of Melia azedarach grown in two different sites in northern Vietnam. The overall values of αT, αR, and αT/αR were 7.05%, 4.38%, and 1.64, respectively. The variation pattern in αT and αR was found to increase gradually from pith to bark and this trend was similar on both sites. In radial direction, the αT/αR decreased significantly from 10 to 50% of the radial length from pith before approaching a constant value toward the outside. The transverse shrinkage variation with height was very small and without statistical significance. There were strong positive relationships between transverse shrinkage and basic density (BD). This implies that the selection for high wood density may lead to increase wood transverse shrinkage. In addition, the αT and αR had significant positive linear relationships with both acoustic wave velocity (VL) and dynamic modulus of elasticity of log (DMOElog). This result suggests that it might be possible to sort lumber with large transverse shrinkage by stress wave method for M. azedarach planted in northern Vietnam. 相似文献
16.
Effects of forest cover types and environmental factors on soil respiration dynamics in a coastal sand dune of subtropical China 总被引：2，自引：0，他引：2
Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors. 相似文献
17.
Huihui Zhang Peng Feng Wei Yang Xin Sui Xin Li Wei Li Rongtao Zhang Siyu Gu Nan Xu 《林业研究》2018,29(4):1049-1059
We applied under pot-culture conditions and the double-casing pot method to study the characteristics of photosynthetic gas exchange and chlorophyll fluorescence in the leaves of Physocarpus amurensis Maxim (PA) and Physocarpus opulifolius under flooding stress. Our results indicate a significantly higher flooding tolerance of P. opulifolius compared to P. amurensis. Especially in P. amurensis, the limitation of non-stomatal factors played a major role in the advanced stages of flooding stress, observed as a rapid increase of the intercellular CO2 concentration (C i) and a decrease of the stomatal limitation value (L s). The maximal PSII photochemical efficiencies (F v/F m) and actual photochemical efficiency (Ф PSII) in the leaves of P. opulifolius were significantly higher, and the extent of decrease during the flooding process was smaller than in P. amurensis. In addition, the non-chemical quenching (NPQ) in the leaves of P. opulifolius significantly increased from the 10th day under flooding stress, while the variation of NPQ in the leaves of P. amurensis was much smaller. This indicates that the leaves of P. opulifolius had not only higher PSII photochemical activity, but also improved tolerance to flooding stress, which may be caused by its ability to dissipate excess excitation energy by starting NPQ. At the 16th day under flooding stress, the P IABS significantly decreased with greater extent of decrease than F v/F m in the leaves of both Physocarpus, but the decreasing extent of P IABS in P. opulifolius was significantly smaller than in P. amurensis. In the 16th day under flooding stress, the fluorescence at J and I point (V J and V I) in P. amurensis were significantly higher, and the extent of increase in V J was greater than V I. However, the variations of V J and V I in the leaves of P. opulifolius were smaller, suggesting that the damage sites of flooding stress to PSII in the leaves of P. amurensis were mainly located in the electron transport process from QA at the PSII receptor side to QB. Flooding stress reduced the proportion (φE o ) of luminous energy absorbed by the PSII reaction center for the electron transport following Q A ? , while the maximum quantum yield (φD o) of non-photochemical quenching increased. However, the TRo/RC and ETo/RC in the leaves of P. amurensis decreased accompanied by a dramatic increase of energy (DIo/RC) from the dissipation in the reaction center. This further indicated that the function of the PSII reaction center in the leaves of P. amurensis was significantly lower than in P. opulifolius. 相似文献
18.
We studied leaf litter fall, decomposition and nutrient release patterns of Shorea robusta and Tectona grandis by using a litter bag technique to better understand the release pattern of nutrients to soil from leaf litter. Annual litterfall varied from 13.40 ± 2.56 t ha?1 a?1 for S. robusta to 11.03 ± 3.72 t ha?1 a?1 for T. grandis and the decay constant (k) of decomposed leaf litter was distinctly higher for T. grandis (2.70 ± 0.50 a?1) compared to S. robusta (2.41 ± 0.30 a?1). Biomass loss was positively correlated with the initial litter C, WSC, C/N and ash content in S. robusta and N, P and K concentration for T. grandis. Biomass was negatively correlated with lignin and L/N ratio for S. robusta and L, WSC, L/N and C/N ratio for T. grandis (P < 0.01). Nutrient use efficiency (NUE) and nutrient accumulation index (NAI) of S. robusta was higher than for T. grandis. The retranslocation of bioelements from senescent leaves ranked as P > N > K. Annual N, P and K input to soil through litterfall differed significantly between the two species in the following order: N>K>P. S. robusta was superior in terms of K and P return and T. grandis was superior in terms of N return. The two tree species showed a similar patterns of nutrient release (K > P > N) during decomposition of their leaf litter. Nutrients of N, K and P were the primary limiting nutrients returned to soil through litterfall with important roles in soil fertility and forest productivity. 相似文献
19.
To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture, soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa (Thunb.) Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate (P N), stomatal conductance (g s), and water-use efficiency (W UE) in the seedlings exhibited a clear threshold response to the relative soil water content (R SWC). The highest P N and W UE occurred at R SWC of 51.84 and 64.10%, respectively. Both P N and W UE were higher than the average levels at 39.79% ≤ R SWC ≤ 73.04%. When R SWC decreased from 51.84 to 37.52%, P N, g s, and the intercellular CO2 concentration (C i) markedly decreased with increasing drought stress; the corresponding stomatal limitation (L s) substantially increased, and nonphotochemical quenching (N PQ) also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II (PSII) in the form of heat, and the reduction in P N was primarily due to stomatal limitation. While R SWC decreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry (F v/F m) and the effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching (q P), and N PQ; in contrast, minimal fluorescence yield of the dark-adapted state (F 0) increased markedly. Thus, the major limiting factor for the P N reduction changed to a nonstomatal limitation due to PSII damage. Therefore, an R SWC of 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% ≤ R SWC ≤ 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F. suspensa. 相似文献
20.