Late Successional Research Articles

Plasticity and implications of water-use traits in contrasting tropical tree species under climate change.

Plants face a trade-off between hydraulic safety and growth, leading to a range of water-use strategies in different species. However, little is known about such strategies in tropical trees and whether different water-use traits can acclimate to warming. We studied five water-use traits in 20 tropical tree species grown at three different altitudes in Rwanda (RwandaTREE): stomatal conductance (gs), leaf minimum conductance (gmin), plant hydraulic conductance (Kplant), leaf osmotic potential (ψo) and net defoliation during drought. We also explored the links between these traits and growth and mortality data. Late successional (LS) species had low Kplant, gs and gmin and, thus, low water loss, while low ψo helped improve leaf water status during drought. Early successional (ES) species, on the contrary, used more water during both moist and dry conditions and exhibited pronounced drought defoliation. The ES strategy was associated with lower mortality and more pronounced growth enhancement at the warmer sites compared to LS species. While Kplant and gmin showed downward acclimation in warmer climates, ψo did not acclimate and gs measured at prevailing temperature did not change. Due to distinctly different water use strategies between successional groups, ES species may be better equipped for a warmer climate as long as defoliation can bridge drought periods.

Thermophilisation of Afromontane forest stands demonstrated in an elevation gradient experiment

Abstract. The response of tropical trees and tree communities to climate change is crucial for the carbon storage and biodiversity of the terrestrial biosphere. Trees in tropical montane rain forests (TMFs) are considered particularly vulnerable to climate change, but this hypothesis remains poorly evaluated due to data scarcity. To reduce the knowledge gap in the response of TMF trees to warming, we established a field experiment along a 1300–2400 m elevation gradient as a proxy for warming in Rwanda. Seedling-size trees of 20 species native to montane forests in eastern and central Africa were planted in multi-species plots at three sites along the gradient. They have overlapping distributions but primarily occur in either transitional rain forests (∼ 1600–2000 ma.s.l.) or mid-elevation TMFs (∼ 2000–3000 ma.s.l.), with both early- (ES) and late-successional (LS) species represented in each elevation origin group. Tree growth (diameter and height) and survival were monitored regularly over 2 years. We found that ES species, especially from lower elevations, grew faster at warmer sites, while several of the LS species, especially from higher elevations, did not respond or grew slower. Moreover, a warmer climate increased tree mortality in LS species, but not much in ES species. ES species with transitional rain forest origin strongly increased proportional to stand basal area at warmer sites, while TMF species declined, suggesting that lower-elevation ES species will have an advantage over higher-elevation species in a warming climate. The risk of higher-elevation and LS species of becoming outcompeted by lower-elevation and ES species due to a thermophilisation response in a warmer climate has important implications for biodiversity and carbon storage of Afromontane forests.

Contrasting warming responses of photosynthesis in early- and late-successional tropical trees.

The productivity and climate feedbacks of tropical forests depend on tree physiological responses to warmer and, over large areas, seasonally drier conditions. However, knowledge regarding such responses is limited due to data scarcity. We studied the impact of growth temperature on net photosynthesis (An), maximum rates of Rubisco carboxylation at 25°C (Vcmax25), stomatal conductance (gs) and the slope parameter of the stomatal conductance-photosynthesis model (g1), in 10 early successional (ES) and 8 late-successional (LS) tropical tree species grown at three sites along an elevation gradient in Rwanda, differing by 6.8°C in daytime ambient air temperature. The effect of seasonal drought on An was also investigated. We found that warm climate decreased wet-season An in LS species, but not in ES species. Values of Vcmax25 were lower at the warmest site across both successional groups, and An and Vcmax25 were higher in ES compared with LS species. Stomatal conductance exhibited no significant site differences and g1 was similar across both sites and successional groups. Drought strongly reduced An at warmer sites but not at the coolest montane site and this response was similar in both ES and LS species. Our results suggest that warming has negative effects on leaf-level photosynthesis in LS species, while both LS and ES species suffer photosynthesis declines in a warmer climate with more pronounced droughts. The contrasting responses of An between successional groups may lead to shifts in species' competitive balance in a warmer world, to the disadvantage of LS trees.

Quantifying the influence of different biocrust community states and their responses to warming temperatures on soil biogeochemistry in field and mesocosm studies

Biocrusts influence soil biogeochemistry by fixing carbon (C) and nitrogen (N) and through leachate inputs to soils. Functional rates can vary among biocrust community states and in response to edaphic properties, heterotrophic microbial activity, and global change. Using soils and biocrusts from the Colorado Plateau, Utah, USA, we aimed to quantify the influence of early-successional (ES) and late-successional (LS) biocrust community states on soil biogeochemistry. In a field setting, we found soil was less “fertile” under ES than LS biocrust, but ES biocrust had a relative influence 1.3 times greater than LS biocrust on soil fertility. Leachate collected from LS biocrust had, on average, 6 times more organic C and 1.7 times more dissolved N than ES biocrust, but concentrations of phosphorus (P) and inorganic N did not differ among the two biocrust types. To disentangle influences of biocrusts and soil properties on biogeochemical pools, we constructed mesocosms from homogenized soil and left the surface bare or covered with ES or LS biocrust, before assignment to ambient or warmed (+5 °C) temperature treatments for 3 months. Multivariate biogeochemical properties differed among cover types, yet all exhibited losses of P, N, and organic C and nearly half of the biogeochemical variables considered did not differ among cover types. Mesocosms with LS biocrust retained more dissolved N, supported 8 additional, significant correlations among biogeochemical pools of the biocrust and mineral soil layer on average, and lost fewer of these correlations under warming. Overall, while soils under LS biocrusts were more fertile (i.e., had higher nutrient concentrations) than under ES, we did not find evidence implicating leachate as the primary driver of this difference. Biocrust influences on soil fertility were greater when mineral soil nutrients were in lower concentrations, highlighting the value of even incipient biocrusts for dryland functioning.

Complete or overcompensatory thermal acclimation of leaf dark respiration in African tropical trees.

Summary Tropical climates are getting warmer, with pronounced dry periods in large areas. The productivity and climate feedbacks of future tropical forests depend on the ability of trees to acclimate their physiological processes, such as leaf dark respiration (R d), to these new conditions. However, knowledge on this is currently limited due to data scarcity.We studied the impact of growth temperature on R d and its dependency on net photosynthesis (A n), leaf nitrogen (N) and phosphorus (P) contents, and leaf mass per unit area (LMA) in 16 early‐successional (ES) and late‐successional (LS) tropical tree species in multispecies plantations along an elevation gradient (Rwanda TREE project). Moreover, we explored the effect of drought on R d in one ES and one LS species.Leaf R d at 20°C decreased at warmer sites, regardless if it was expressed per unit leaf area, mass, N or P. This acclimation resulted in an 8% and a 28% decrease in R d at prevailing nighttime temperatures in trees at the intermediate and warmest sites, respectively. Moreover, drought reduced R d, particularly in the ES species and at the coolest site.Thermal acclimation of R d is complete or overcompensatory and independent of changes in leaf nutrients or LMA in African tropical trees.

Contrasting Dependencies of Photosynthetic Capacity on Leaf Nitrogen in Early- and Late-Successional Tropical Montane Tree Species

Differences in photosynthetic capacity among tree species and tree functional types are currently assumed to be largely driven by variation in leaf nutrient content, particularly nitrogen (N). However, recent studies indicate that leaf N content is often a poor predictor of variation in photosynthetic capacity in tropical trees. In this study, we explored the relative importance of area-based total leaf N content (Ntot) and within-leaf N allocation to photosynthetic capacity versus light-harvesting in controlling the variation in photosynthetic capacity (i.e. V cmax, J max) among mature trees of 12 species belonging to either early (ES) or late successional (LS) groups growing in a tropical montane rainforest in Rwanda, Central Africa. Photosynthetic capacity at a common leaf temperature of 25˚C (i.e. maximum rates of Rubisco carboxylation, V cmax25 and of electron transport, J max25) was higher in ES than in LS species (+ 58% and 68% for V cmax25 and J max25, respectively). While Ntot did not significantly differ between successional groups, the photosynthetic dependency on Ntot was markedly different. In ES species, V cmax25 was strongly and positively related to Ntot but this was not the case in LS species. However, there was no significant trade-off between relative leaf N investments in compounds maximizing photosynthetic capacity versus compounds maximizing light harvesting. Both leaf dark respiration at 25˚C (+ 33%) and, more surprisingly, apparent photosynthetic quantum yield (+ 35%) was higher in ES than in LS species. Moreover, Rd25 was positively related to Ntot for both ES and LS species. Our results imply that efforts to quantify carbon fluxes of tropical montane rainforests would be improved if they considered contrasting within-leaf N allocation and photosynthetic Ntot dependencies between species with different successional strategies.

Long-term recovery of soil carbon stocks and permafrost depth lags recovery of organic layer thickness following fire in black spruce forests of the Copper River Basin, Alaska

This study investigated differences in forest structure, organic layer thickness, soil organic carbon, and permafrost depth between late-successional (LS) and postfire (PF; 90–120 years since burn) plots under black spruce (Picea mariana (Mill.) B.S.P.) growing on fine-textured, poorly drained lacustrine sediments in the Copper River Basin, Alaska. Although live stem and seedling density and organic layer thickness were not significantly different between PF and LS plots (28 ± 7 cm and 31 ± 10 cm, respectively), we did find a significant difference in soil organic carbon (SOC) stocks (30 ± 10 kg·m−2 and 46 ± 12 kg·m−2, respectively) permafrost depth (90 ± 28 cm and 56 ± 12 cm, respectively). OLT was linearly related to 1 m SOC stocks for LS plots but not for PF plots, and LS plots had a greater proportion of highly decomposed (humic) material in the organic layer. The soil properties of PF plots appear to be on a trajectory of recovery toward those of LS plots with respect to SOC stocks, permafrost depth, and organic layer composition. However, PF plots remain different despite nearly 100 years since fire disturbance and thus they are potentially more sensitive to changes in future fire frequency or climate.

Carbon stocks and dynamics at different successional stages in an Afromontane tropical forest

Abstract. As a result of different types of disturbance, forests are a mixture of stands at different stages of ecological succession. Successional stage is likely to influence forest productivity and carbon storage, linking the degree of forest disturbance to the global carbon cycle and climate. Although tropical montane forests are an important part of tropical forest ecosystems (ca. 8 %, elevation > 1000 m a.s.l.), there are still significant knowledge gaps regarding the carbon dynamics and stocks of these forests, and how these differ between early (ES) and late successional (LS) stages. This study examines the carbon (C) stock, relative growth rate (RGR) and net primary production (NPP) of ES and LS forest stands in an Afromontane tropical rainforest using data from inventories of quantitatively important ecosystem compartments in fifteen 0.5 ha plots in Nyungwe National Park in Rwanda. The total C stock was 35 % larger in LS compared to ES plots due to significantly larger above-ground biomass (AGB; 185 and 76 Mg C ha−1 in LS and ES plots), while the soil and root C stock (down to 45 cm depth in the mineral soil) did not significantly differ between the two successional stages (178 and 204 Mg C ha−1 in LS and ES plots). The main reasons for the difference in AGB were that ES trees had significantly lower stature and wood density compared to LS trees. However, ES and LS stands had similar total NPP (canopy, wood and roots of all plots ∼ 9.4 Mg C ha−1) due to counterbalancing effects of differences in AGB (higher in LS stands) and RGR (higher in ES stands). The AGB in the LS plots was considerably higher than the average value reported for old-growth tropical montane forest of south-east Asia and Central and South America at similar elevations and temperatures, and of the same magnitude as in tropical lowland forest of these regions. The results of this study highlight the importance of accounting for disturbance regimes and differences in wood density and allometry of tree species dominating at different successional stages in an attempt to quantify the C stock and sink strength of tropical montane forests and how they may differ among continents.

Survival, growth and seed mass in a mixed tree species planting for Atlantic Forest restoration

Selection of tree species is a key aspect of restoration in megadiverse biomes such as the Atlantic Forest, especially in degraded areas with past intensive land use, which usually present severe limiting conditions. The species must have high survival and growth, not only in the transition between germination and seedling but also between seedling and adult plant until allowing the establishment of a self-sustaining and renewable community. In order to reach this goal, restoration initiatives carried out in the Atlantic Forest have employed high-diversity plantings of tree species from different successional guilds. Notwithstanding, long-term silvicultural knowledge is scarce for the native species from this biome, and the effectiveness of these models is controversial. Our investigation has compared the survival and growth of species and guilds in high-diversity tree species plantings in areas with previous agricultural intensive use. The species and guilds were also compared with respect to seed mass since this parameter is pointed out as an indicator of high survival in early stages. Pioneer and secondary species did not present differences in survival and seed mass, although pioneers exhibited greater growth rate. The late successional (LS) species had lower survival and growth, and higher seed mass. Survival after 8 months and between 8–15 months after seedling planting was inversely correlated with seed mass (r2 = 0.35 and r2 = 0.36, P < 0.001). On the other hand, survival after 8 months was correlated with relative growth rate (RGR) in the same periods of time (r2 = 0.34, P < 0.001). Overall average survival was 41% after 15 months, with the survival of LS species at an average of 12%. Data suggests that the inclusion of LS seedlings could impair the efficacy of restoration during early phases, at least in highly degraded areas. Equally, the inclusion of species with high seed mass should be considered with caution.

Spatial distribution patterns of ammonia-oxidizing archaea abundance in subtropical forests at early and late successional stages.

Characterizing the spatial distribution patterns of soil microorganisms is helpful in understanding the biogeochemical processes they perform, but has been less studied relative to those of macroorganisms. In this study, we investigated and compared the spatially explicit distribution patterns of ammonia-oxidizing archaea (AOA) abundance and the influential factors between an early (ES) and a late successional (LS) subtropical forest stand. The average AOA abundance, vegetational attributes, and soil nutrient contents were mostly greater in the LS than the ES stand (P = 0.085 or smaller), but their spatial variations were more pronounced in the ES than the LS stand. The spatial distribution patches of AOA abundance were smaller and more irregular in the ES stand (patch size <50 m) than in the LS stand (patch size about 120 m). Edaphic and vegetational variables contributed more to the spatial variations of AOA abundance for the ES (9.3%) stand than for LS stand, whereas spatial variables (MEMs) were the main contributors (62%) for the LS stand. These results suggest that environmental filtering likely influence the spatial distribution of AOA abundance at early successional stage more than that at late successional stage, while spatial dispersal is dominant at late successional stage.

Tending of Young Forests in Secondary Succession on Abandoned Agricultural Lands: An Experimental Study

In Europe the area of forested land is increasing, largely due to forest development on abandoned agricultural lands. We compared the structure and composition of woody species in young stands undergoing secondary succession and within gaps of late-successional (LS) forest in Haloze (Slovenia) to derive management options. In a subset of plots in succession, silvicultural measures were carried out in one half, while the other half was left untreated. The attributes of crop trees and their competitor trees were monitored over five years, and a study on the time investment of tending was conducted. We found lower tree density, a larger share of pioneer and shrub species, and a higher diversity of woody plants in succession compared to regeneration within LS forest gaps. Tending resulted in greater density of crop trees, their better social position, fewer competitor trees, and a larger diameter at breast height (d.b.h.) increment, while differences in crop tree stability and quality between tending and control were not confirmed. Our results indicated great structural complexity and species diversity in young successional forests. Their tending represents a cost efficient method of recovering the long-term commercial value and ecosystem services of forests, if applied less intensively than traditional tending of LS forest.

Late-successional and old-growth forest carbon temporal dynamics in the Northern Forest (Northeastern USA)

Comprehensive data on the capacity and rates of change for carbon pools in managed and unmanaged forests is essential for evaluating climate change mitigation options being considered by policy makers at regional and national levels. We currently lack real and long-term data on forest carbon dynamics covering a wide range of forest management practices and conditions. Because of this, selecting the best policies for conserving forest carbon must rely on forest growth and yield models such as US Forest Service (USFS) Forest Vegetation Simulator (FVS) to predict the future forest carbon impacts of management actions. FVS may underestimate the capacity of older stands to accumulate carbon because the model relies on USFS Forest Inventory and Analysis data that lack data from late-successional and old-growth (LSOG) stands. Improving these models will increase the likelihood of selecting policies that successfully use forests to reduce atmospheric carbon. From 1995 to 2002, Manomet Center for Conservation Sciences conducted research on 65 10m by 50m permanent plots to evaluate forest structure (standing live and dead trees, and down coarse woody material) in LSOG stands across northern Maine. We re-measured these plots in 2011 to assess long-term carbon sequestration trends in LSOG stands of common forest types in the Northern Forest region for above ground alive, standing dead, and coarse woody material carbon pools. Late-successional (LS) and Old-growth (OG) aboveground live carbon (C) stocks were very high relative to regional mean C stocks (2.0–2.5 times the mean), LS plots were accumulating aboveground live C at a positive rate (0.61Mgha−1 year−1), while C stocks on OG plots are declining (−0.54Mgha−1 year−1). This change is driven by the presence of beech bark fungus (Nectria sp.) that is leading to mortality in larger diameter American beech (Fagus grandifolia) trees. We also found that the Northeast Variant of the Forest Vegetation Simulator is not a reliable predictor of aboveground live carbon accumulation rates in Northeastern LS and OG stands. This work provides important baselines for understanding the role of older forests and forest management within climate change mitigation strategies in the northeastern US. Late-successional and old-growth forests can play an important role in mitigating climate change, but understanding and quantifying natural disturbance risk to forest carbon stocks is critical for successful implementation of mitigation strategies. Further, regional forest carbon models will need calibration to accurately predict carbon accumulation rates in older forests.

Phosphorus sorption capacity and exchange by soils from mitigated and late successional bottomland forest wetlands

Abstract A central tenet of wetland mitigation is that replacement wetlands can sequester nutrients and perform other functions at the same level as natural wetlands. This study evaluated phosphorus (P) sorption capacity and P exchange in flooded soil microcosms obtained from eight early successional (ES) mitigated and eight late successional (LS) bottomland forest wetlands in western Kentucky, USA. The LS soils had three times greater capacity to remove and retain soluble inorganic P than ES soils, which was mostly due to higher amounts of amorphous aluminum (Al) oxides (oxalate extractable), organically-bound Al (CuCl2 extractable), and organic carbon in LS soils. Phosphorus exchange rates between the soil and water column were not significantly different in LS and ES microcosms, but rates in both systems were strongly related to the molar ratio of Mehlich III extractable P to Al + Fe in the soil (r2=0.64). Relationships between P sorption/exchange and organic C, Mehlich III- and oxalate-extractable for...

A soil microbial community structural-functional index: the microscopy-based total/active/active fungal/bacterial (TA/AFB) biovolumes ratio

In most studies of fungal–bacterial communities in soils, single-value indices such as fumigation–extraction (FE) of microbe-derived organic carbon, measures of specific microbial cell chemical constituents, or activity-related measures have been used. These widely used single value indices, however, do not provide information on the physical structure of the filamentous fungal and bacterial community in a soil. The filamentous fungi, considered as indeterminate organisms, have a variable and changing hyphal network, most of which is devoid of cytoplasm. To meet this need for a direct integrated measure of the physical characteristics of the indeterminate fungi and their associated bacteria, a microscopy-based microbial biovolumes ratios approach is suggested. To provide this information, the total and active biovolumes of both the filamentous fungi and bacteria are assessed by microscopy. To normalize these responses, the ratio of total to active (TA) fungal plus bacterial biovolumes is divided by the ratio of the active fungal to bacterial biovolume (AFB), to yield the total/active/active fungal/bacterial (TA/AFB) biovolumes ratio. This approach has been used to analyze data from recently-cultivated early successional (ES) and uncultivated late successional (LS) sites at a shortgrass steppe of northeastern Colorado, where control plots were compared with those receiving mineral nitrogen amendments, using samples taken during the summer of 1995. The TA/AFB ratio index showed distinct and significant decreases in response to soil disturbance which reflected the decreased hyphal lengths present in these disturbed soils. These changes were not detected by the use of FE-based extractable carbon measurements. The TA/AFB ratio also showed significant positive correlations with indices of plant community development and mineral nitrogen, especially in the plots not amended with N. This TA/AFB ratios index should be able to provide information on the physical structure of the indeterminate filamentous fungi and associated soil bacteria for use in the assessment of soil quality, health and resiliency.

Growth patterns of early versus late successional multipurpose trees of the western Himalaya

In the mid-western Himalaya (altitude 1350 m, rainfall 1100 mm), multipurpose trees found as escapees in agricultural fields or naturally growing in the forests, play an important role in providing fuel, fooder and small timber to the farmers. Shoot elogation, and tree architecture of 4 year old trees of Grewia optiva, Robinia pseudoacacia and Celtis australis (early successionals), and Quercus leucotrichophora, Q. glauca and Ilex odorata (late successionals), were analyzed. All the late successional species showed a proleptic type of bud and branch production, while the early successional trees made growth through syllepsis. The shoot elongation differed significantly (P <0.05) with the crown position, and ranged from 11 to 30 cm in different species. Early successional species tended to maintain a comparatively narrow crown and showed a significantly (P <0.05) higher ramification ratio, and multilayered canopy. The late successionals, in contrast, showed a wide crown with monolayered canopy, adapted to the weak light intensity. There was only one flush of leaves in Q. leucotrichophora and Q. glauca while in the rest of the species there were two distinct flush periods. The results are important for the management of agroforestry trees.

Plasticity and acclimation to light in tropical Moraceae of different sucessional positions.

We evaluated both the photosynthetic plasticity and acclimation to light of seedlings of five co-occurring tropical tree species in the Moraceae,Cecropia obtusifolia, Ficus insipida, Poulsenia armata, Brosimum alicastrum, andPseudolmedia oxyphyllaria. Distinct differences in the species' abilities to respond to increasing irradiance correlated with their known habitat breadths and successional status. The early successinalsCecropia andFicus exhibited the highest photosynthetic rates and conductance values in high light. There was a several-fold difference in assimilation across light regimes, consistent with a high physiological plasticity. When individuals grown at low light were transferred to higher irradiances, seedlings of bothCecropia andFicus produced leaves which photosynthesized at rates as high or higher than those of plants continuously grown in high light, indicating a high photosynthetic acclimation potential. In contrast, the late successionals were characterized by both a more restricted physiological plasticity and acclimation potential. Higher light levels resulted in only moderate increases in assimilation among the late successionals, and onlyBrosimum acclimated fully to increased irradiances. NeitherPoulsenia norPseudolmedia increased appreciably their photosynthetic rates when transferred to high light. This suggests that acclimation potential cannot always be inferred from plasticity responses, and calls for a reevaluation of arguments developed solely from plasticity studies. Finally, differences between the early and late successional species in the allocation of nitrogen into RuBP carboxylase and thylakoid nitrogen pools or non-photosynthetic compounds are suggested by the distinct relationships between maximum photosynthetic capacity and nitrogen content.

Leaf dynamics of early versus late successional shrubs of sub-tropical moist forests of north-eastern India

The two early successional shrubs (Melastoma malabathricum L. andMussenda frondosa L.) are periodic growth leaf-exchanging-types (leaf fall is associated with bud break; leaf span of leaves being approximately 12 months), whereas the two late successional ones (Litsaea khasiana Meissn andOxyspora vagans Wall.) are periodic growth evergreen types (leaf fall is completed well after bud break; life span of leaves being a little over one year). Early successional shrubs have larger leaf production and faster turn-over rates, unlike late successional shrubs with production confined during the early part of the growing season (April–May) is geared to expose larger area over a longer time period, for survival under shade. The early successional shrubs have an exploitative strategy whereas the late successionals are conservative in nature for survival under shade.

Architecture and growth patterns of early versus late successional shrubs of sub-tropical moist forests of north-eastern India

Growth and architecture of early versus late successional shrubs are compared and contrasted to evaluate their leaf display characteristics. Early successional shrubs had a higher growth rate over an extended period of time compared to late successional shrubs. Inter-branch length and branch angle were greater for late successional species as compared to early successional ones. First- and second-order branch production over third-order branches was greater in late successional shrubs, whereas the reverse was the case for early successional ones. On the other hand, length contribution by all branch orders was higher for the early successional species. The bifurcation ratio was significantly higher for early successional species growing in the open as compared to late successional shrub species growing in shade. Early successional shrubs follow an exploitive strategy and make faster growth whereas late successionals have a conservative strategy for survival in shade.

Biomass allocation strategies and productivity of tropical trees related to successional status

The productivity and biomass allocation strategies of two early successional (ES) and two late successional (LS) tropical tree species were compared and related to their successional status. Apart from distinct differences in clean bole length, crown depth, maximum crown width and leaf area index (LAI), the ES species showed higher allocation to the shoot, particularly to the bole, whereas the LS species had higher allocation to the root. The ES species with shallow root system had more root biomass within the upper 20 cm of the soil profile while the LS species with deeper roots had a higher proportion of root biomass distributed below the 20 cm depth. The productivity of the shoot of ES species was significantly higher than that of LS species. However, root productivity for ES species was higher only up to 4 years of age; the differences were not significant between 5 and 7 years. The implication of these results for agroforestry and mixed plantation forestry is emphasized.