Yield-density effects on growth and biomass partitioning in Leucaena leucocephala seedlings

Experiments were conducted to study the effects of density on growth and biomass partitioning of Leucaena leucocephala seedlings.Four plantations with densities of 10,000,20,000,40,000,and 80,000 seedlings ha^-1 were evaluated only from 15 to 25 months after planting.At 15 months,crown height and width decreased with increasing density.Seedling height/dbh ratios increased with increasing density.Biomass increased with greater density according to the yield–density effect equation,which was evident for all densities.With increasing age,biomass division to branches and leaves increased,whereas partitioning to roots decreased in the 10,000 and 20,000 seedlings ha-1 plantings.Partitioning to branches and leaves remained relatively steady,while partitioning to roots increased in the 40,000 and 80,000 seedlings ha^-1 plantings.Biomass division into stem and bark components remained relatively steady in all densities.Yield–density and organ yield–density curves shifted upward with increasing seedling age on a log–log graph throughout the experimental period.

Divergent biomass partitioning to aboveground and belowground across forests in China

Aims Belowground to aboveground biomass(BGB/AGB)ratio is a highly valued parameter of the terrestrial carbon cycle and productivity.However,it remains far from clear whether plant biomass partition-ing to aboveground and belowground is isometric(equal partition-ing)or allometric(unequal partitioning)at community levels and what factors are necessary in order to regulate the partitioning.This study aimed to comprehensively find out the patterns of biomass partitioning and their regulatory factors across forests in China.Methods The data of AGB and BGB were compiled from 1542 samples for communities across forests in China.Standardized major axis regression was conducted to examine whether AGB and BGB were allocated isometrically or allometrically at a community level.Redundancy analysis was used to analyze the relationships of BGB/AGB ratio with climatic factors and soil properties.Important Findings We found that the slopes of the relationship between logAGB and logBGB were not always comparable to 1.0(isometric allocation)at community levels,including primary forest,secondary forest,and planted forest.Meanwhile,samples in clay,loam,and sand soil types also presented the same phenomenon.Furthermore,the radically different allocations of AGB and BGB were found in northern and southern China.Environmental factors totally explained 3.86%of the variations in the BGB/AGB ratio at the community level,which include the mean annual precipitation,mean annual temperature,potential water deficit index,soil car-bon content,soil nitrogen content,soil clay,soil loam,soil sand,soil pH,and soil bulk density.In addition,the environmental fac-tors also have effects on the BGB/AGB ratio in other categories.The patterns revealed in this study are helpful for better under-standing biomass partitioning and spreading the carbon circle models.

Species-specific biomass allometric models and expansion factors for indigenous and planted forests of the Mozambique highlands

Secondary Miombo woodlands and forest plantations occupy increasing areas in Mozambique,the former due to anthropogenic activities.Plantations,mainly species of Eucalyptus and Pinus,are being established on sites previously covered by secondary Miombo woodlands.This affects the evolution,cycle and spatiotemporal patterns of carbon(C)storage and stocks in forest ecosystems.The estimation of C storage,which is indispensable for formulating climate change policies on sequestrating CO_(2),requires tools such as biomass models and biomass conversion and expansion factors(BCEF).In Mozambique,these tools are needed for both indigenous forests and plantations.The objective of this study is to fit species-specific allometric biomass models and BCEF for exotic and indigenous tree species.To incorporate efficient inter-species variability,biomass equations were fitted using nonlinear mixed-effects models.All tree component biomass models had good predictability;however,better predictive accuracy and ability was observed for the 2-predictors biomass model with tree height as a second predictor.The majority of the variability in BCEF was explained by the variation in tree species.Miombo species had larger crown biomass per unit of stem diameter and stored larger amounts of biomass per stem volume.However,due to relatively rapid growth,larger stem diameters,heights,and stand density,the plantations stored more biomass per tree and per unit area.

How much carbon can the Siberian boreal taiga store： a case study of partitioning among the above-ground and soil pools

In the context of global carbon cycle management, accurate knowledge of carbon content in forests is a relevant issue in contemporary forest ecology. We measured the above-ground and soil carbon pools in the darkconiferous boreal taiga. We compared measured carbon pools to those calculated from the forest inventory records containing volume stock and species composition data. The inventory data heavily underestimated the pools in the study area（Stolby State Nature Reserve, central Krasnoyarsk Territory, Russian Federation）. The carbon pool estimated from the forest inventory data varied from 25（t ha-1）（low-density stands） to 73（t ha-1）（highly stocked stands）. Our estimates ranged from 59（t ha-1）（lowdensity stands） to 147（t ha-1）（highly stocked stands）. Our values included living trees, standing deadwood, living cover, brushwood and litter. We found that the proportion of biomass carbon（living trees）： soil carbon varied from99：1 to 8：2 for fully stocked and low-density forest stands,respectively. This contradicts the common understanding that the biomass in the boreal forests represents only16–20 % of the total carbon pool, with the balance being the soil carbon pool.

Functional Equilibrium Between Photosynthetic and Above-ground Nonphotosynthetic Structures of Plants: Evidence from a Pruning Experiment with Three Subtropical Tree Species

It is well known that plants have functional equilibrium between their above-ground parts (shoots) and below-ground parts (roots), but whether the above-ground parts of plants have functional equilibrium between their photosynthetic structures (leaves) and non-photosynthetic structures (branches and stem) is unknown. The purpose of this study is to test the hypotheses that: (1) the above-ground parts of plants have functional equilibriums between their photosynthetic structures and non-photosynthetic structures; (2) the maintenance of the equilibriums is guaranteed by the alteration of biomass partitioning to photosynthetic and non-photosynthetic structures. To test these hypotheses, a pruning experiment with four pruning intensities (0%, 20%, 50%, and 70%) were carried out with three subtropical Chinese tree species ( Ficus microcarpa, Ficus virens, Cinnamomum camphora). Pruning treatments were conducted in two successive years. The results were in conformity with the hypothesis, i.e. above-ground parts of trees had functional equilibriums between photosynthetic and non-photosynthetic structures. Pruning decreased instantaneously the mass ratios of photosynthetic structures to non-photosynthetic structures (P/NP) of all three tree species, the reduction in P/NP was strengthened with pruning intensity. However, one year after pruning, the P/NP of all pruned trees increased and were not smaller than those of unpruned trees. In agreement with the expectation, the biomass partitioning of pruned trees was altered, more newly produced above-ground biomass was partitioned to leaf growth and less to branch and stem growth, thus enabled the damaged trees to restore their functional equilibrium between photosynthetic and non-photosynthetic structures. It is clear that the maintenance of functional equilibrium between photosynthetic and non-photosynthetic structures guaranteed by the alteration of biomass partitioning provides plants a good strategy to resist external disturbance and damage.

Allometric response of perennial Pennisetum centrasiaticum Tzvel to nutrient and water limitation in the Horqin Sand Land of China

Optimal partitioning theory （OPT） suggests that plants should allocate relatively more biomass to the organs that acquire the most limited resources. The assumption of this theory is that plants trade off the biomass allocation between leaves, stems and roots. However, variations in biomass allocation among plant parts can also occur as a plant grows in size. As an alternative approach, allometric biomass partitioning theory （APT） asserts that plants should trade off their biomass between roots, stems and leaves. This approach can minimize bias when comparing biomass allocation patterns by accounting for plant size in the analysis. We analyzed the biomass allo- cation strategy of perennial Pennisetum centrasiaticum Tzvel in the Horqin Sand Land of northern China by treating samples with different availabilities of soil nutrients and water, adding snow in winter and water in summer. We hypothesized that P. centrasiaticum alters its pattern of biomass allocation strategy in response to different levels of soil water content and soil nitrogen content. We used standardized major axis （SMA） to analyze the allometric rela- tionship （slope） and intercept between biomass traits （root, stem, leaf and total biomass） of nitrogen/water treat- ments. Taking plant size into consideration, no allometric relationships between different organs were significantly affected by differing soil water and soil nitrogen levels, while the biomass allocation strategy of P. centrasiaticum was affected by soil water levels, but not by soil nitrogen levels. The plasticity of roots, leaves and root/shoot ratios was ＇true＇ in response to fluctuations in soil water content, but the plasticity of stems was consistent for trade-offs between the effects of water and plant size. Plants allocated relatively more biomass to roots and less to leaves when snow was added in winter. A similar trend was observed when water was added in summer. The plasticity of roots, stems and leaves was a function of plant size, and remained unchanged in response to different soil nitrogen levels.

BAP Spray and Plastic Container Responses on Asparagus officmalis L. Crown Growth

The aims of this work were to study the effect of two different plastic containers on asparagus growth and the effect of early applied 6-benzilaminepurine （BAP） on crown growth during the first two years after seed germination. Although there was not found a root restriction effect with the use of plastic containers, there were significant differences between plants grown in plastic seedbed or single pots which suggesting an unusual and unexpected asparagus autotoxicity. The results showed that crown fresh weight, total dry weight, relative growth ratio （RGRroot）, root：shoot ratio and photosynthetic shoot number increased in BAP-sprayed plants over the controls without treatment as a result of a change in photosynthate partitioning towards the root system. The BAP snravs seem to be a ~reater effect under conditions with favor autotoxicitv such as the seedbed than in single pot crown-grown.

Effect of Weak Light on the Photoassimilates Distribution and Transformation of Young Grape Plants

The effect of weak light on the photoassimilates distribution and transformation of young Jingyu grape plants ( Vitis vinefera L. cv. Jingyu) were studied by shading. Compared to the grape grown under natural light intensity environment, the net photosynthetic rate diurnal variation curve of experimental plants grown in weak light intensity environment was remarkably lower. Its leaf and stem biomass ratio increased when light intensity decreased, the root and new shoot biomass ratio showed an opposite trend. The 14 C-photoassimilates was mostly distributed to young leaves and stem, a little was distributed to root. The metabolism of 14C-photoassimilates distributed to the entire grape body were also changed under weak light intensity environment.

Allocation patterns of nonstructural carbohydrates in response to CO_(2)elevation and nitrogen deposition in Cunninghamia lanceolata saplings

Stored nonstructural carbohydrates(NSC)indicate a balance between photosynthetic carbon(C)assimilation and growth investment or loss through respiration and root exudation.They play an important role in plant function and whole-plant level C cycling.CO_(2)elevation and nitrogen(N)deposition,which are two major environmental issues worldwide,aff ect plant photosynthetic C assimilation and C release in forest ecosystems.However,information regarding the eff ect of CO_(2)elevation and N deposition on NSC storage in diff erent organs remains limited,especially regarding the trade-off between growth and NSC reserves.Therefore,here we analyzed the variations in the NSC storage in diff erent organs of Chinese fi r(Cunninghamia lanceolata)under CO_(2)elevation and N addition and found that NSC concentrations and contents in all organs of Chinese fi r saplings increased remarkably under CO_(2)elevation.However,N addition induced diff erential accumulation of NSC among various organs.Specifi cally,N addition decreased the NSC concentrations of needles,branches,stems,and fi ne roots,but increased the NSC contents of branches and coarse roots.The increase in the NSC contents of roots was more pronounced than that in the NSC content of aboveground organs under CO_(2)elevation.The role of N addition in the increase in the structural biomass of aboveground organs was greater than that in the increase in the structural biomass of roots.This result indicated that a diff erent tradeoff between growth and NSC storage occurred to alleviate resource limitations under CO_(2)elevation and N addition and highlights the importance of separating biomass into structural biomass and NSC reserves when investigating the eff ects of environmental change on biomass allocation.

Optimal root system strategies for desert phreatophytic seedlings in the search for groundwater

Desert phreatophytes are greatly dependent on groundwater, but how their root systems adapt to different groundwater depths is poorly understood. In the present study, shoot and root growths of Alhagi sparsifolia Shap. seedlings were studied across a gradient of groundwater depths. Leaves, stems and roots of different orders were measured after 120 days of different groundwater treatments. Results indicated that the depth of soil wetting front and the vertical distribution of soil water contents were highly controlled by groundwater depths. The shoot growth and biomass of A. sparsifolia decreased, but the root growth and rooting depth increased under deeper groundwater conditions. The higher ratios of root biomass, root/shoot and root length/leaf area under deeper groundwater conditions implied that seedlings of A. sparsifolia economized carbon cost on their shoot growths. The roots of A. sparsifolia distributed evenly around the soil wetting fronts under deeper groundwater conditions. Root diameters and root lengths of all orders were correlated with soil water availabilities both within and among treatments. Seedlings of A. sparsifolia produced finer first- and second-order roots but larger third- and fourth-order roots in dry soils. The results demonstrated that the root systems of desert phreatophytes can be optimized to acquire groundwater resources and maximize seedling growth by balancing the costs of carbon gain.

Effects of irrigation and nitrogen management on hybrid maize seed production in north-west China

Scientific irrigation and nitrogen management is important for agricultural production in arid areas. To quantify the effect of water and nitrogen management on yield components, biomass partitioning and harvest index(HI) of maize for seed production with plastic filmmulching, field experiments including different irrigation and N treatments were conducted in arid north-west China in 2013 and 2014. The results indicated that kernel number per plant(KN) was signi ficantly affected by irrigation and N treatments. However, 100-kernel weight was relatively stable. Reducing irrigation quantity signi ficantly increased stem partitioning index(PI_(stem)) and leaf partitioning index(PIl_(eaf)), and decreased ear partitioning index(PI_(ear)) at harvest, but lowering Nrate(from 500 to 100 kg N$hm^(–2))did not signi ficantly reduce PI_(stem), PI leaf, andPIl_(eaf) at harvest. HI was signi ficantly reduced by reducing irrigation quantity, but not by reducing Nrate. Linear relationships were found between KN, PI_(stem), PI leaf,PIl_(eaf) at harvest and HI and evapotranspiration(ET).

Elevated CO_2 Accelerates Phosphorus Depletion by Common Bean(Phaseolus vulgaris) in Association with Altered Leaf Biochemical Properties

Phosphorus （P） is a major limiting factor for plant productivity in many ecosystems and agriculture. The projected increase in atmospheric CO2 is likely to result in changes in plant mineral consumption and growth. We studied P depletion by common bean （Phaseolus vulgaris） cultured hydroponically under ambient （377±77μmol mol^-1） or elevated （650±32 μmol mol^-1） CO2 in media of low or high P. Under elevated CO2 compared to ambient CO2, the maximum P depletion rate increased by 98% at low P and 250% at high P, and P was depleted about 2-5 weeks sooner; leaf acid phosphatase （APase） activity and chlorophyll content both increased significantly; root-to-shoot ratio increased significantly at high P, although it was unaffected at low P; lateral root respiration rate showed no change, suggesting that COs did not affect P depletion via metabolic changes to the roots; the total biomass at final harvest was significantly higher at both low and high P. Our data showed that the increased rate and amount of P depletion during plant growth under elevated CO2 occurred in association with alterations in leaf biochemical properties, i.e., enhanced activities of leaf APase and increased leaf chlorophyll content.

Symbiotic interactions as drivers of trade-offs in plants: effects of fungal endophytes on tall fescue

Studying the controls on biomass allocation trade-offs in plants are important since they affect harvestable product yields and are critical to understanding symbiotic interactions.Epichloae fungal endophytes associate with cool-season grasses,growing systemically within the plant inter-cellular spaces and are transmitted through seeds.We explore the endophytes influence on the relationship between the plant reproductive and vegetative aboveground biomass(reproductive effort:RE)and on the trade-off between two components of the reproductive biomass,number and weight of panicles(RPN),using tall fescue as a model system.Naturally endophyte-colonized,manipulatively endophyte-free,and naturally endophyte-free plants from Northern European wild-populations together with the cultivar Kentucky-31 were grown under different environmental conditions(nutrients x water).The endophyte had an effect on the RPN(E+:6.19,ME-:4.68 and E-:4.40)which indicates how reproductive biomass is partitioned into number and mass of panicles,but not on RE(≈0.06).As expected,wild plants showed higher reproductive effort(≈0.06)compared to the cultivar KY-31(0.05),irrespective of endophyte presence.Endophyte-colonized plants had lighter panicles than endophyte-free plants,a pattern that was clear among low-yielding plants.Similarly,the tradeoff between RPN and RE was higher for endophytecolonized plants.This was again evident among plants with low RE indicating that colonized plants split the yield into either greater number of panicles and/or lighter panicles.The effect of vertically transmitted endophytes has earlier been studied as ratios(e.g.RE);however,our study shows that this approach may hide size-dependent endophyte effects on these relationships.Our study reveals that Neotyphodium endophyte affects trade-offs in tall fescue plants in a complex manner,and is influenced by a number of biological and abiotic factors.

Effects of resource sharing directionality on physiologically integrated clones of the invasive Carpobrotus edulis

Aims One of the key traits associated with clonal growth in plants is the capacity for physiological integration,which allows resource sharing between connected ramets within a clonal system.Resource transport is expected to occur following a source–sink relationship:from ramets established in rich patches to ramets growing in poor patches.However,some experiments have shown that acropetal transport(from basal to apical modules)usually exceeds basipetal transport(from apical to basal ramets).In this study,we aimed to determine the resource transport directionality in physiologically integrated modules of the invader Carpobrotus edulis.Methods We conducted two manipulative experiments under common garden conditions that studied the effect of different nutrient levels located at different positions(basal,medial and apical)on connected and disconnected clonal systems of C.edulis.We compared the biomass partitioning patterns and final biomass of ramets to elucidate whether the effect of physiological integration is affected by the directionality of the resource transport.Important Findings Results indicate a prevalent acropetal transport of resources in C.edulis,with a developmentally programmed division of labor where basal ramets were specialized in obtaining soil-based resources and apical ramets specialized in aboveground growth.This biomass partitioning pattern was not affected by the nutrient conditions in which basal or apical ramets were growing,although the highest benefit was achieved by apical ramets growing under the most stressed conditions.This developmentally programmed division of labor is expected to increase the lateral growth of C.edulis,and therefore could have meaningful implications for the expansion of this invasive species.