Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit area

The observation of acclimation in leaf photosynthetic capacity to differences in growth irradiance has been widely used as support for a hypothesis that enables a simplification of some soil‐vegetation‐atmosphere transfer (SVAT) photosynthesis models. The acclimation hypothesis requires that relative leaf nitrogen concentration declines with relative irradiance from the top of a canopy to the bottom, in 1 : 1 proportion. In combination with a light transmission model it enables a simple estimate of the vertical profile in leaf nitrogen concentration (which is assumed to determine maximum carboxylation capacity), and in combination with estimates of the fraction of absorbed radiation it also leads to simple ‘big‐leaf’ analytical solutions for canopy photosynthesis. We tested how forests deviate from this condition in five tree canopies, including four broadleaf stands, and one needle‐leaf stand: a mixed‐species tropical rain forest, oak (Quercus petraea (Matt.) Liebl), birch (Betula pendula Roth), beech (Fagus sylvatica L.) and Sitka spruce (Picea sitchensis (Bong.) Carr). Each canopy was studied when fully developed (mid‐to‐late summer for temperate stands). Irradiance (Q, µmol m^?2 s^?1) was measured for 20 d using quantum sensors placed throughout the vertical canopy profile. Measurements were made to obtain parameters from leaves adjacent to the radiation sensors: maximum carboxylation and electron transfer capacity (V_a, J_a, µmol m^?2 s^?1), day respiration (R_da, µmol m^?2 s^?1), leaf nitrogen concentration (N_m, mg g^?1) and leaf mass per unit area (L_a, g m^?2). Relative to upper‐canopy values, V_a declined linearly in 1 : 1 proportion with N_a. Relative V_a also declined linearly with relative Q, but with a significant intercept at zero irradiance (P < 0·01). This intercept was strongly related to L_a of the lowest leaves in each canopy (P < 0·01, r² = 0·98, n= 5). For each canopy, daily lnQ was also linearly related with lnV_a(P < 0·05), and the intercept was correlated with the value for photosynthetic capacity per unit nitrogen (PUN: V_a/N_a, µmol g^?1 s^?1) of the lowest leaves in each canopy (P < 0·05). V_a was linearly related with L_a and N_a(P < 0·01), but the slope of the V_a : N_a relationship varied widely among sites. Hence, whilst there was a unique V_a : N_a ratio in each stand, acclimation in V_a to Q varied predictably with L_a of the lowest leaves in each canopy. The specific leaf area, L_m(cm² g^?1), of the canopy‐bottom foliage was also found to predict carboxylation capacity (expressed on a mass basis; V_m, µmol g^?1 s^?1) at all sites (P < 0·01). These results invalidate the hypothesis of full acclimation to irradiance, but suggest that L_a and L_m of the most light‐limited leaves in a canopy are widely applicable indicators of the distribution of photosynthetic capacity with height in forests.     

Decline of photosynthetic capacity with leaf age and position in two tropical pioneer tree species

The effect of leaf age on photosynthetic capacity, a critical parameter in the theory of optimal leaf longevity, was studied for two tropical pioneer tree species, Cecropia longipes and Urera caracasana, in a seasonally dry forest in Panama. These species continuously produce short-lived leaves (74 and 93 d, respectively) during the rainy season (May-December) on orthotropic branches. However, they differ in leaf production rate, maximum number of leaves per branch, light environment experienced by the leaves, leaf mass per unit area, and nitrogen content. Light-saturated photosynthetic rates for marked leaves of known ages (±1 wk) were measured with two contrasting schemes (repeated measurements vs. chronosequence within branch), which overall produced similar results. In both species, photosynthetic rates and nitrogen use efficiency were negatively correlated with leaf age and positively correlated with light availability. Photosynthetic rates declined faster with leaf age in Cecropia than in Urera as predicted by the theory. The rate of decline was faster for leaves on branches with faster leaf turnover rates. Nitrogen per unit leaf area decreased with leaf age only for Urera. Leaf mass per unit area increased with leaf age, either partly (in Cecropia) or entirely (in Urera) due to ash accumulation.     

黑龙江省次生林主要组成树种光合能力与叶片含氮量研究

以黑龙江省次生林主要组成树种蒙古栎、白桦、水曲柳、山杨、胡桃楸、黄波罗为研究对象,测定自然状态下这6个树种的光合能力,并分析光合能力与叶片含氮量之间的关系.研究结果表明,树种的光合能力存在明显的季节变化,不同树种间的光合能力、光合潜力存在差异.生长季中,胡桃楸具有最高的光合能力最大值,白桦具有最高的年平均光合能力,蒙古栎具有最大的光合潜力.蒙古栎叶片含氮量与光合能力线性正相关(r=0.97),白桦、水曲柳叶片含氮量与光合能力呈二次曲线相关(r=0.61,r=0.51).     

Aboveground nitrogen and phosphorus use by five plantation-grown trees with different leaf longevities

Aboveground nitrogen (N) and phosphorus (P) requirement, retranslocation and use efficiency were determined for 28-year-old red oak (Quercus rubra L.), European larch (Larix decidua Miller), white pine (Pinus strobes L.), red pine (Pinus resinosa Ait.) and Norway spruce (Picea abies (L) Karst.) plantations on a similar soil in southwestern Wisconsin. Annual aboveground N and P requirements (kg/ha/yr) totaled 126 and 13 for red oak, 86 and 9 for European larch, 80 and 9 for white pine, 38 and 6 for red pine, and 81 and 13 for Norway spruce, respectively. Nitrogen and P retranslocation from current foliage ranged from 81 and 72%, respectively, for European larch, whereas red pine retranslocated the smallest amount of N (13%) and Norway spruce retranslocated the smallest amount of P (18%). In three evergreen species, uptake accounted for 72 to 74% of annual N requirement whereas for two deciduous species retranslocation accounted for 76 to 77% of the annual N requirement. Nitrogen and P use (ANPP/uptake) was more efficient in deciduous species than evergreen species. The results from this common garden experiment demonstrate that differences in N and P cycling among species may result from intrinsic characteristics (e.g. leaf longevity) rather than environmental conditions.     

冠层部位和叶龄对红松光合蒸腾特性的影响

利用Li-6400便携式CO2/H2O红外气体分析仪测定了红松不同冠层部位和叶龄针叶的光合蒸腾特性及其环境影响因子.结果表明:冠层部位和叶龄显著地影响最大净光合速率(Pmax)、光饱和点(LSP)、光补偿点(LCP)、表观最大量子效率(α)、蒸腾速率(Tr)和比叶面积(SLA),但对水分利用效率(WUE)影响不显著.随着冠层部位的下降和叶龄的增加,红松针叶的Pmax逐渐下降,其平均值变动在6·55～9·05μmol·m-2·s-1之间.不同冠层部位和叶龄针叶的LSP和LCP的差异很大,以树冠中部针叶对弱光和强光的利用能力最大.Tr随着冠层部位的下降而降低;不同叶龄针叶的Tr在1·37～1·59mmol·m-2·s-1之间变化.不同部位和叶龄红松针叶的Tr和光合有效辐射存在极显著正相关关系(R2=0·967).红松的WUE与净光合速率紧密相关(R2=0·860).随冠层部位的上升和叶龄的增大,红松针叶的SLA递减,分别在6·61～8·41m2·kg-1和6·65～8·38m2·kg-1之间波动.     

Complex adjustments of photosynthetic potentials and internal diffusion conductance to current and previous light availabilities and leaf age in Mediterranean evergreen species Quercus ilex

Mature non-senescent leaves of evergreen species become gradually shaded as new foliage develops and canopy expands, but the interactive effects of integrated light during leaf formation (Q(int)G), current light (Q(int)C) and leaf age on foliage photosynthetic competence are poorly understood. In Quercus ilex L., we measured the responses of leaf structural and physiological variables to Q(int)C and Q(int)G for four leaf age classes. Leaf aging resulted in increases in leaf dry mass per unit area (M(A)), and leaf dry to fresh mass ratio (D(F)) and decreases in N content per dry mass (N(M)). N content per area (N(A)) was independent of age, indicating that decreases in N(M) reflected dilution of leaf N because of accumulation of dry mass (NA = N(M) M(A)). M(A), D(F) and N(A) scaled positively with irradiance, whereas these age-specific correlations were stronger with leaf growth light than with current leaf light. Area-based maximum ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylase activity (V(cmax)A), capacity for photosynthetic electron transport (J(max)A) and the rate of non-photorespiratory respiration in light (R(d)A) were also positively associated with irradiance. Differently from leaf structural characteristics, for all data pooled, these relationships were stronger with current light with little differences among leaves of different age. Acclimation to current leaf light environment was achieved by light-dependent partitioning of N in rate-limiting proteins. Mass-based physiological activities decreased with increasing leaf age, reflecting dilution of leaf N and a larger fraction of non-photosynthetic N in older leaves. This resulted in age-dependent modification of leaf photosynthetic potentials versus N relationships. Internal diffusion conductance (g(m)) per unit area (g(m)A) increased curvilinearly with increasing irradiance for two youngest leaf age classes and was independent of light for older leaves. In contrast, g(m) per dry mass (g(m)M) was negatively associated with light in current-year leaves. Greater photosynthetic potentials and moderate changes in diffusion conductance resulted in greater internal diffusion limitations of photosynthesis in higher light. Both area- and mass-based g(m) decreased with increasing leaf age. The decrease in diffusion conductance was larger than changes in photosynthetic potentials, leading to larger CO2 drawdown from leaf internal air space to chloroplasts (delta(c)) in older leaves. The increases in diffusion limitations in older leaves and at higher light scaled with age- and light-dependent increases in MA and D(F). Overall, our study demonstrates a large potential of foliage photosynthetic acclimation to changes in leaf light environment, but also highlights enhanced structural diffusion limitations in older leaves that result from leaf structural acclimation to previous rather than to current light environment and accumulation of structural compounds with leaf age.     

Relationships between photosynthetic activity and silica accumulation with ages of leaf in Sasa veitchii (Poaceae, Bambusoideae)

BACKGROUND AND AIMS: Bamboos have long-lived, evergreen leaves that continue to accumulate silica throughout their life. Silica accumulation has been suggested to suppress their photosynthetic activity. However, nitrogen content per unit leaf area (N(area)), an important determinant of maximum photosynthetic capacity per unit leaf area (P(max)), decreases as leaves age and senescence. In many species, P(max) decreases in parallel with the leaf nitrogen content. It is hypothesized that if silica accumulation affects photosynthesis, then P(max) would decrease faster than N(area), leading to a decrease in photosynthetic rate per unit leaf nitrogen (photosynthetic nitrogen use efficiency, PNUE) with increasing silica content in leaves. METHODS: The hypothesis was tested in leaves of Sasa veitchii, which have a life span of 2 years and accumulate silica up to 41 % of dry mass. Seasonal changes in P(max), stomatal conductance, N(area) and silica content were measured for leaves of different ages. KEY RESULTS: Although P(max) and PNUE were negatively related with silica content across leaves of different ages, the relationship between PNUE and silica differed depending on leaf age. In second-year leaves, PNUE was almost constant although there was a large increase in silica content, suggesting that leaf nitrogen was a primary factor determining the variation in P(max) and that silica accumulation did not affect photosynthesis. PNUE was strongly and negatively correlated with silica content in third-year leaves, suggesting that silica accumulation affected photosynthesis of older leaves. CONCLUSIONS: Silica accumulation in long-lived leaves of bamboo did not affect photosynthesis when the silica concentration of a leaf was less than 25 % of dry mass. Silica may be actively transported to epidermal cells rather than chlorenchyma cells, avoiding inhibition of CO2 diffusion from the intercellular space to chloroplasts. However, in older leaves with a larger silica content, silica was also deposited in chlorenchyma cells, which may relate to the decrease in PNUE.     

太岳山典型阔叶乔木冠层叶片性状的分布格局

以太岳山4种阔叶乔木不同冠层高度的叶片为研究对象,用LI-3000A叶面积仪和Li-6400便携式光合作用测定系统分别测定了这4种乔木不同冠层高度叶片的叶面积大小和单位面积的叶光饱和速率(Aarea);同时测定了其叶氮含量;计算了其比叶面积(SLA)、单位面积叶氮含量(Narea)、单位重量叶氮含量(Nmass)、单位重量的叶光饱和速率(Amass)和光合氮素利用效率(PNUE),对植株不同冠层高度叶片的SLA、叶氮和光合特性的空间分布格局进行了比较研究,结果表明:Aarea、Amass、Nmass、PNUE、SLA和Narea在树冠上层、中层和下层的差异均达到了极显著水平(P<0.001),表明树冠不同高度的叶片性状参数差异较大;在相同SLA下,Nmass和Narea在冠层中的分布均表现为中层>上层>下层,并出现平行位移现象;Aarea和Nmass都以中层值最大,表明冠层光合能力分布格局以中层相对较高。     

热带雨林恢复演替中优势树种黄桐气体交换对环境的响应

用Li-6400便携式光合测定系统(Li-CorInc.,USA)对海南岛热带山地雨林恢复演替先锋建群种黄桐(EndospermumchinenseBenth.)叶片的气体交换特征及其对环境的响应进行了测定。结果表明:(1)净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(E)日变化均为双峰型曲线。出现"午睡"原因是光合有效辐射(PPFD)不足和Gs的关闭,不是强光抑制和水分胁迫。(2)叶片Pn大小与Gs、E、PPFD、气温(Ta)和叶面温度(Tl)等为密切的正比关系,与胞间CO2浓度(Ci)、大气CO2浓度(Ca)和大气相对湿度(RH)等相关度极低甚至是负相关,光饱和点(LSP)较高,表现出阳性树种特性。(3)短期高Ca作用会引起Gs、E的降低和Pn增高。Ca倍增,则Pn提高了70%,E降低4.43%,水分利用效率(WUE)提高78%。(4)叶片Pn日平均值和日最大值分别达6.40±0.17、11.60μmolCO2/(m2·s),表现出速生性。     

Seedling growth of five tropical dry forest tree species in relation to light and nitrogen gradients

Aims Increasing anthropogenic nitrogen (N) deposition has been claimed to induce changes in species composition and community dynamics. A greenhouse experiment was conducted to examine the effect of increased N availability on growth and functional attributes of seedlings of five tree species with different life history characteristics under varying irradiances. The following questions have been addressed: (i) how do the pioneer and non-pioneer species respond in absolute growth and relative growth rate (RGR) to the interaction of light and nitrogen? (ii) how does the interaction between irradiance and nitrogen availability modulate growth attributes (i.e. functional attributes)? (iii) is there any variation in growth responses between leguminous and non-leguminous species along the light and nitrogen gradients?Methods Seedlings of five tree species (Acacia catechu, Bridelia retusa, Dalbergia sissoo, Lagerstroemia parviflora and Terminalia arjuna) were subjected to twelve combinations of irradiance and N levels. Various growth traits, including height (HT), basal area (BA), whole plant dry biomass (M D), leaf mass per unit area (LMA), leaf area ratio (LAR), net assimilation rate (NAR), RGR, biomass fractions, root-to-shoot ratio (R:S) and leaf nitrogen content, were studied to analyse intra- and inter-specific responses to interacting light and N gradients.Important findings Significant interactions for irradiance and N availability for majority of growth attributes indicates that growth and biomass allocation of seedlings were more responsive to N availability under high irradiance. However, species responded differentially to N addition and they did not follow successional status. Slow growers (B. retusa, a shade-tolerant species and L. parviflora, a light demander) exhibited greater response to N enrichment than the fast growers (A. catechu, D. sissoo and T. arjuna). However, N-mediated increment in growth traits was greater in non-legumes (B. retusa, L. parviflora and T. arjuna) compared with that of legumes (A. catechu and D. sissoo). Allocation of biomass to root was strongly suppressed at the highest N supply across species; however, at high irradiance and high N availability, a greater suppression in R:S ratio was observed for B. retusa. NAR was a stronger determinant of RGR relative to LAR, suggesting its prominent role in increased RGR along increasing irradiances. Overall, a higher growth response of slow-growing species to elevated N levels, particularly the non-pioneers (B. retusa and L. parviflora) suggests that future N deposition may lead to perturbations in competition hierarchies and species composition, ultimately affecting community dynamics in nutrient-poor tropical dry forests.     

The capacity to emit isoprene differentiates the photosynthetic temperature responses of tropical plant species

Experimental research shows that isoprene emission by plants can improve photosynthetic performance at high temperatures. But whether species that emit isoprene have higher thermal limits than non‐emitting species remains largely untested. Tropical plants are adapted to narrow temperature ranges and global warming could result in significant ecosystem restructuring due to small variations in species' thermal tolerances. We compared photosynthetic temperature responses of 26 co‐occurring tropical tree and liana species to test whether isoprene‐emitting species are more tolerant to high temperatures. We classified species as isoprene emitters versus non‐emitters based on published datasets. Maximum temperatures for net photosynthesis were ~1.8°C higher for isoprene‐emitting species than for non‐emitters, and thermal response curves were 24% wider; differences in optimum temperatures (T_opt) or photosynthetic rates at T_opt were not significant. Modelling the carbon cost of isoprene emission, we show that even strong emission rates cause little reduction in the net carbon assimilation advantage over non‐emitters at supraoptimal temperatures. Isoprene emissions may alleviate biochemical limitations, which together with stomatal conductance, co‐limit photosynthesis above T_opt. Our findings provide evidence that isoprene emission may be an adaptation to warmer thermal niches, and that emitting species may fare better under global warming than co‐occurring non‐emitting species.     

Carbon gain in a multispecies canopy: the role of specific leaf area and photosynthetic nitrogen-use efficiency in the tragedy of the commons

Models have been formulated for monospecific stands in which canopy photosynthesis is determined by the vertical distribution of leaf area, nitrogen and light. In such stands, resident plants can maximize canopy photosynthesis by distributing their nitrogen parallel to the light gradient, with high contents per unit leaf area at the top of the vegetation and low contents at the bottom. Using principles from game theory, we expanded these models by introducing a second species into the vegetation, with the same vertical distribution of biomass and nitrogen as the resident plants but with the ability to adjust its specific leaf area (SLA, leaf area:leaf mass). The rule of the game is that invaders replace the resident plants if they have a higher plant carbon gain than those of the resident plants. We showed that such invaders induce major changes in the vegetation. By increasing their SLA, invading plants could increase their light interception as well as their photosynthetic nitrogen-use efficiency (PNUE, the rate of photosynthesis per unit organic nitrogen). By comparison with stands in which canopy photosynthesis is maximized, those invaded by species of high SLA have the following characteristics: (1) the leaf area index is higher; (2) the vertical distribution of nitrogen is skewed less; (3) as a result of the supra-optimal leaf area index and the more uniform distribution of nitrogen, total canopy photosynthesis is lower. Thus, in dense canopies we face a classical tragedy of the commons: plants that have a strategy to maximize canopy carbon gain cannot compete with those that maximize their own carbon gain. However, because of this strategy, individual as well as total canopy carbon gain are eventually lower. We showed that it is an evolutionarily stable strategy to increase SLA up to the point where the PNUE of each leaf is maximized.     

Differences in leaf phenology between juvenile and adult individuals of two tree species in a seasonally dry tropical woodland

In temperate forests, juvenile trees anticipate leaf phenology compared to adults, thus avoiding shading and herbivory. This is also expected to occur in seasonal tropical forests due to intense herbivory and shading during the rainy season; however, the anticipation of leaf phenology by juveniles in seasonal tropical forests has yet to be demonstrated. Stem‐succulent species are expected to be prone to juvenile phenological anticipation because these species are able to use water stored in their stems for leaf flushing in the dry season. We investigated this hypothesis by comparing leaf phenology (bud break, leaf expansion) of juveniles and adults of two species with contrasting wood densities in the transition between dry and rainy seasons in a tropical dry woodland. We also investigated the level of light limitation that juveniles experience in the rainy season. Both species exhibited bud break during the dry season, but only expanded their leaves with the occurrence of the first rains. In general, the stem‐succulent species had a more precocious bud break; however, anticipation by juveniles occurred only in the species with more dense wood. Canopy openness was lower than in temperate deciduous forests, but the fact that the full expansion of leaves occurred only with rainfall indicates that bud break in anticipation of canopy closure contributes only to keeping leaf photosynthetic balance from going negative, and not to higher carbon gain. The importance of anticipated budding for escaping herbivory remains an alternative explanation in need of investigation.     

Diaheliotropic leaf movement enhances leaf photosynthetic capacity and photosynthetic light and nitrogen use efficiency via optimising nitrogen partitioning among photosynthetic components in cotton (Gossypium hirsutum L.)

• Phototropic leaf movement of plants is an effective mechanism for adapting to light conditions. Light is the major driver of plant photosynthesis. Leaf N is also an important limiting factor on leaf photosynthetic potential. Cotton (Gossypium hirsutum L.) exhibits diaheliotropic leaf movement. Here, we compared the long‐term photosynthetic acclimation of fixed leaves (restrained) and free leaves (allowed free movement) in cotton.
• The fixed leaves and free leaves were used for determination of PAR, leaf chlorophyll concentration, leaf N content and leaf gas exchange. The measurements were conducted under clear sky conditions at 0, 7, 15 and 30 days after treatment (DAT).
• The results showed that leaf N allocation and partitioning among different components of the photosynthetic apparatus were significantly affected by diaheliotropic leaf movement. Diaheliotropic leaf movement significantly increased light interception per unit leaf area, which in turn affected leaf mass per area (LMA), leaf N content (N_A) and leaf N allocation to photosynthesis (N_P). In addition, cotton leaves optimised leaf N allocation to the photosynthetic apparatus by adjusting leaf mass per area and N_A in response to optimal light interception.
• In the presence of diaheliotropic leaf movement, cotton leaves optimised their structural tissue and photosynthetic characteristics, such as LMA, N_A and leaf N allocation to photosynthesis, so that leaf photosynthetic capacity was maximised to improve the photosynthetic use efficiency of light and N under high light conditions.

     

After more than a decade of soil moisture deficit,tropical rainforest trees maintain photosynthetic capacity,despite increased leaf respiration

Determining climate change feedbacks from tropical rainforests requires an understanding of how carbon gain through photosynthesis and loss through respiration will be altered. One of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability. In this study we examine if and how both leaf photosynthesis and leaf dark respiration acclimate following more than 12 years of experimental soil moisture deficit, via a through‐fall exclusion experiment (TFE) in an eastern Amazonian rainforest. We find that experimentally drought‐stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought‐induced mortality. We hypothesize that photosynthetic capacity is maintained across all treatments and taxa to take advantage of short‐lived periods of high moisture availability, when stomatal conductance (g_s) and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times. Average leaf dark respiration (R_d) was elevated in the TFE‐treated forest trees relative to the control by 28.2 ± 2.8% (mean ± one standard error). This mean R_d value was dominated by a 48.5 ± 3.6% increase in the R_d of drought‐sensitive taxa, and likely reflects the need for additional metabolic support required for stress‐related repair, and hydraulic or osmotic maintenance processes. Following soil moisture deficit that is maintained for several years, our data suggest that changes in respiration drive greater shifts in the canopy carbon balance, than changes in photosynthetic capacity.     

Responses of leaf unfolding and flowering to climate change in 12 tropical evergreen broadleaf tree species in Jianfengling,Hainan Island

为了探讨我国热带地区植物物候与气候变化的关系, 利用海南岛尖峰岭热带树木园12种热带常绿阔叶乔木植物2003-2011年物候观测资料结合同期月平均气温和降水数据, 运用积分回归分析方法, 筛选出影响海南岛12种乔木(8种本地种、4种引入种)展叶始期与开花始期的气象因素以及不同气象因素月值变化(月平均气温和月降水量)综合作用对这些树种物候期的动态影响, 最终建立积分回归-物候预测模型, 对气候变化背景下我国热带地区植物物候变化趋势进行了预测。结果表明: 海南岛12种热带常绿阔叶乔木展叶始期与开花始期均对气候变化做出较明显的响应, 几乎所有的树种展叶始期与开花始期的发生都受到气温和降水的共同影响。多数树种展叶始期受展叶前冬季及春季气温影响显著, 且在临近展叶始期的月份, 气温的影响更显著。上一年秋季月降水量对各树种开花始期的影响比其他时段显著, 这验证了降水的滞后性假说。本地种展叶始期对气候变化的响应比其开花始期对气候变化的响应更敏感, 引入种则相反。各树种展叶和开花在受气温和降水综合影响最明显的月份(假设其余11个月份月平均气温和月降水量不变), 月平均气温升高0.1 ℃、月降水量增加10 mm可使展叶始期和开花始期提前或推迟1-3天。积分回归分析方法为解释海南岛热带常绿阔叶乔木物候与气温和降水的动态关系提供了有效的途径, 基于气温和降水与物候资料建立的积分回归-物候预测模型具有对气温和降水变化影响下物候响应的解释率和预测精度高(R²≥ 0.943)的优点, 对于预测气候变化影响下的植物物候变化趋势有一定的适用性。