Root competition for phosphorus between coconut, multipurpose trees and Kacholam (Kaempferia galanga L.) in Kerala, India

The magnitude of root competition 17 year-old coconut palms suffer from three year-old inter-planted multipurpose trees, Vateria indica L., Ailanthus triphysa (Dennst.) Alston. or Grevillea robusta A. Cunn. and kacholam (Kaempferia galanga L.), a herbaceous medicinal plant, was evaluated based on the extent of absorption of applied ³²P by the palms in sole and mixed crop situations. The multipurpose tree (MPT) species were grown under two planting geometries (single row and double row). The hypothesis that, when grown together, widespread root proliferation of coconut and multipurpose trees occurs in the well-fertilised kacholam beds was tested by root excavation. Interplanted MPTs substantially altered absorption of ³²P by coconut. Both Ailanthus and Vateria exerted a modest depressing effect, while Grevillea enhanced ³²P uptake by coconut. Single rows of MPTs also favoured ³²P recovery by coconut, presumably because of the increased root densities in the subsoil. Ailanthus, Vateria and Grevillea absorbed substantial ³²P. Overall, high ³²P absorption in the coconut-Grevillea plots indicates complementary root-level interactions between these species. ³²P absorption by MPTs was generally higher closer to the trees owing to the greater root concentration of the MPTs, which in turn suggests possible root interference between MPTs and coconut. Hence selection of tree species with low root competitiveness and/or trees with complementary root interaction is of strategic importance in agroforestry. Kacholam showed substantial ³²P content in its foliage. This ³²P appears to have been translocated by coconut into the kacholam beds where new coconut roots were abundant. This revised version was published online in June 2006 with corrections to the Cover Date.     

Root competition for phosphorus between ginger and Ailanthus triphysa in Kerala,India

To acquire information on the nature of belowground interactions in intercropping system involving ginger, Zingiber officinale Roscoe, and Ailanthus triphysa (Dennst.) Alston, their root activity was evaluated based on 32P recovery by each species in mixed and sole crop situations. Treatments included two Ailanthus densities (1,111 and 3,333 tress ha−1) and four lateral distances of 32P application (10 and 20 cm from the treated ginger plant and 20 and 40 cm from the treated Ailanthus trees). Recovery of 32P in ginger foliage increased with time, irrespective of tree population density and lateral distance of isotope application. Lack of significant variations in 32P recovery as a function of tree population density suggests that tree density is probably not a strong determinant of belowground competition in the well-fertilised, manured and mulched system studied (at least till four years after tree planting). Nonetheless, neighbouring Ailanthus trees absorbed a substantial potion of the 32P supplied to ginger. This, in turn, suggests that the effective root zones of ginger and Ailanthus may overlap. Data on 32P uptake of Ailanthus suggest that 41% to 59% of the root activity is concentrated within a zone of about 40-cm distance from the trunk. Neighbouring trees in the high density stands absorbed significantly more 32P than those in low density stands (P < 0.01 at 30 and 45 days after 32P application). Our observations also suggest that competition between the tree and the herbaceous crop for nutrients applied to the tree component is unlikely in the Ailanthus-ginger mixed species system studied. Therefore, from a crop management perspective, it is better to fertilise the herbaceous component of the mixed species system adequately, as it will also benefit the tree component. Nutrient use efficiency may be higher under such situations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bamboo hedgerow systems in Kerala, India: Root distribution and competition with trees for phosphorus

In a field study on bamboo (Bambusa arundinacea (Retz.) Willd.) hedgerow systems of Kerala, we tested the following three hypotheses: (1) Effective root foraging space is a function of crown spread, (2) Proximity of trees depress lateral spread of roots in mixed species systems and (3) The closer the trees are located the greater will be the subsoil root activity which in turn facilitates active absorption of nutrients from deeper layers of the soil profile. Root distribution of boundary planted bamboo and root competition with associated trees in two binary mixtures, teak (Tectona grandis)-bamboo and Malabar white pine (Vateria indica)-bamboo, were evaluated using modified logarithmic spiral trenching and ³²P soil injection techniques respectively. Excavation studies indicate that rooting intensity declined linearly with increasing lateral distance. Larger clumps manifested wider foraging zones. Eighty three per cent of the large clumps (>4.0 m dia.) extended roots beyond 8 m while only 33% of the small (<2.5 m dia.) clumps extended roots up to 8 m. Highest root counts were found in the 10–20 cm layer with nearly 30% of total roots. Although nearness of bamboo clumps depressed root activity of teak and Vateria in the surface layers of the soil profile, root activity in the deeper layers was stimulated. ³²P recovery was higher when applied at 50-cm depth than at 25-cm depth implying the safety net role of tree roots for leached down nutrients. Inter specific root competition can be regulated by planting crops 8–9 m away from the bamboo clumps and/or by canopy reduction treatments. This revised version was published online in June 2006 with corrections to the Cover Date.     

Litter dynamics of six multipurpose trees in a homegarden in Southern Kerala, India

Multipurpose trees, the integral components of homegardens, contribute significantly to the closed nutrient cycling processes and sustainability of the ecosystem. Although, the litter production and probable nutrient returns via litter in homegardens have been documented, quantification and characterization of the decomposition and bioelement release from the litter have received relatively little scientific attention. The objective of the present study is to explore the litter dynamics of six locally important multipurpose trees (Mangifera indica L., Artocarpus heterophyllus Lamk., Anacardium occidentale L., Ailanthus triphysa Dennst., Artocarpus hirsutus L. and Swietenia macrophylla L.), in an agroforestry homegarden in Southern Kerala, India. Litterfall and nutrient additions in the six species ranged from 383 to 868 g m⁻² yr⁻¹, nitrogen, 6.4 to 8.8, phosphorus, 0.17 to 0.42 and potassium, 1.1 to 2.8 g m⁻² yr⁻¹. The annual litter output in the homegarden was 425 kg with A. hirsutus, M. indica, A. heterophyllus and A. occidentale recording significantly higher litter and nutrient additions. Leaf litter decay studies revealed A. heterophyllus and A. occidentale to be the most labile litter species and S. macrophylla the most recalcitrant. The decay rate coefficients varied significantly among the species. Foliage decomposition rates related to the initial chemical composition of the litter revealed best correlation with lignin. NPK release was almost complete by the end of decay in all species inspite of the initial phases of accumulation observed for nitrogen and phosphorus. Two-way analysis of variance test revealed significant differences in the contents of the three elements as a function of species and time elapsed. Macronutrients were released in the order K>N/P. The higher rates of decay and nutrient turnover in M. indica, A. heterophyllus and A. occidentale foliage indicated the potential of using these species’ litter as nutrient inputs in agriculture while A. triphysa, A. hirsutus and S. macrophylla perform better as organic mulches taking a longer time for decay and hence nutrient release.     

Litter of multipurpose trees in Kerala,India: variations in the amount,quality, decay rates and release of nutrients

In a field study involving 8–9 year-old woodlots of nine fast growing tree species in Kerala, India, the amount and nutrient content of litterfall were monitored. Decay rate constants and litter half-lives were estimated by fitting a single exponential model to the litter decomposition data. Annual litter production ranged from 3.43 Mg ha⁻¹ (Pterocarpus) to 12.69 Mg ha⁻¹ (Acacia). Litterfall of Acacia, Ailanthus, Pterocarpus and Casuarina followed a uni-modal distribution pattern. Nutrient content of litter samples showed considerable variations, owing to species and sampling time. Based on mean litter N content, the nine species were broadly divided into high, medium and low detrital N species. Litterfall accounted for substantial nutrient recycling within the system. Results of the litter bag study revealed that residual litter mass declined exponentially with time for Ailanthus, Pterocarpus, Casuarina and Leucaena. Paraserianthes showed a linear trend, while Emblica and the two Artocarpus species exhibited a bi-phasic pattern of mass loss. Both initial lignin content and lignin–N ratio had a negative, although modest influence on decay rate coefficients, while initial N content exerted a positive influence. Nutrient release from the decomposing litter followed either a tri-phasic pattern characterised by an initial accumulation, followed by a rapid release and a final slower release phase, or a bi-phasic pattern that is devoid of the initial accumulation phase.     

Crop productivity under differently lopped canopies of multipurpose trees in Central Himalaya, India

Ficus species are multipurpose trees well known by rural populations in Sahelian and Sudanian zones of Africa. Their uses are well documented but their amenability for vegetative propagation has not been extensively studied. This paper compares the rooting ability of stem and aerial root cuttings from thirteen Ficus species found in West Africa. It highlights the differences between species belonging to the sub-genera Sycomorus and Urostigma. The former show no capacity to propagate from cuttings whereas the latter, with epiphytic development, can be propagated by cuttings, although this capacity varies among species. Thus, F. thonningii, F. leprieurii and F. ovata are easily propagated, while F. platyphylla and F. elasticoides are propagated with difficulty. The rooting capacity also varies depending on the cutting material used. It decreases in the following order: long leafless hardwood cuttings (pole) > nodal cuttings > apical cuttings. Rooting potential increases when the cuttings are harvested towards the end of the dry season(March to May). Aerial root can be used for cuttings in all species of the sub-genus Urostigma. The capacity of root cuttings to regenerate is greatest when cuttings are collected at the beginning of the dry season (November). In this case, wound-induced adventitious roots arise at the basal end of the cutting while de novo buds are developed from the cambium at the distal end. The subsequent morphological development is identical to that of a stem cutting. These results clarify and allow the optimal use of the knowledge and methods developed by the indigenous people of the Sahel and could assist and promote fig tree (Ficus sp.) domestication in the dry tropics.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effects of pruning on radial growth and biomass increment of trees growing in homegardens of Kerala, India

To evaluate the effects of pruning on stem radial growth increment and leaf and twig biomass production, an experiment with four pruning intensities (0, 50, 75 and 90%) on ten locally important tree species (Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bombax malabarica, Bridelia crenulata, Erythrina indica, Grewia tiliifolia, Macaranga peltata, Terminalia paniculata and Xylia xylocarpa ), was carried out. The results did not support the contention that a certain level of pruning promotes stem growth in trees. Instead, all species have a level of pruning that reduces annual increment in stem diameter. In Ailanthus triphysa and Artocarpus hirsutus trees subjected to different pruning intensities showed a decline in the annual increment in stem diameter while in other species diameter increment reduced when the pruning intensity was 75% and 90%. Response to pruning in terms of biomass production also varied from species to species. In Erythrina indica, Macaranga peltata and Terminalia paniculata annual foliage and branch production in pruned trees was significantly more than that of the un-pruned trees. However, in Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa pruned trees produced comparatively more amount of foliage and branches produced annually than that by the un-pruned trees when the pruning was carried out once in 2 years. Based on these observations it is recommended that trees of Erythrina indica, Macaranga peltata and Terminalia paniculata may be pruned at 50% level annually while the trees of Ailanthus triphysa, Albizia odoratissima, Artocarpus hirsutus, Bridelia crenulata, Grewia tiliifolia and Xylia xylocarpa may be pruned at the same pruning intensity once in 2 years.     

Dynamics of Homegarden Structure and Function in Kerala, India

Homegardens in Kerala have long been important multi-purpose agroforestry systems that combine ecological and socioeconomical sustainability. However, traditional homegardens are subject to different conversion processes linked to socioeconomic changes. These dynamics were studied in a survey of 30 homegardens. On the basis of a cluster analysis of tree/shrub species density and subsequent further grouping using homegarden size as additional characteristic, six homegarden types were differentiated. These were assessed regarding structural, functional, management and dynamics characteristics. Four development stages of homegardens were found along a gradient from traditional to modern homegardens. Fifty percent of the homegardens still displayed traditional features, whereas 33% incorporated modern practices. The process of modernisation includes a decrease of the tree/shrub diversity, a gradual concentration on a limited number of cash-crop species, an increase of ornamental plants, a gradual homogenization of homegarden structure and an increased use of external inputs. One homegarden was characterised as an adapted traditional homegarden combining multispecies composition and intensive management practices using internal inputs with commercial production. In comparison to modern homegardens, this homegarden type offers an example of an alternative development path in adapting homegardens to changing socioeconomic conditions. The study of structural and functional dynamics of homegardens offers the opportunity to understand the trends in socio-economic sustainability and how these relate to ecological sustainability.     

Live storage and drying of storm-felled Norway spruce (Picea abies,L. Karst.) and Scots pine (Pinus sylvestris L.) trees

Storm-felled trees left in the forest for a shorter or longer period, affect the quality of the logs. The change in quality is mainly because of attack of fungi and insects, which in turn depends on the moisture content (MC) of the sapwood. The purpose of this study was to receive more knowledge about drying of storm-felled trees by investigating how fast winter storm-felled Norway spruce and Scots pine dried when left in the forest. Sixteen storm-felled spruces with part of the roots still in ground contact were selected from three stands and in addition to 10 pines from one of the stands. The trees were examined for MC in the sapwood until 21 months after the storm. This study indicates that wind-thrown trees with roots still connected to the soil can survive one summer without any value loss caused by draught, fungi and insects. The stand conditions can be of importance as the storm-felled trees in the stand, with scattered windthrow, were in best condition after one year, as they were shadowed by the trees still standing. Comparing spruces and pines with the stand with scattered windthrow, pines were more sensitive to drought and reached critical MC earlier.     

Guava (Psidium guajava L.) trees in a pasture: population model,sensitivity analyses,and applications

A preliminary demographic model is presented for a population of guava (Psidium guajava L.) trees in a pasture. In this paper special attention is devoted to describing both the calculation and testing of the parameters of the model. Some applications of the model are described. It is predicted that the guava population will gradually decline; low seedling survival (due to chemical control of pasture weeds) seems to be the factor governing this trend. Preliminary analyses of total gross energy production and economic income, with and without the guavas, favours the presence of the trees in pastures.     

Guava (Psidium guajava L.) trees in a pasture: population model,sensitivity analyses,and applications

A preliminary demographic model is presented for a population of guava (Psidium guajava L.) trees in a pasture. In this paper special attention is devoted to describing both the calculation and testing of the parameters of the model. Some applications of the model are described. It is predicted that the guava population will gradually decline; low seedling survival (due to chemical control of pasture weeds) seems to be the factor governing this trend. Preliminary analyses of total gross energy production and economic income, with and without the guavas, favours the presence of the trees in pastures.     

Interspecific competition impacts on the morphology and distribution of fine roots in European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.)

Morphology and vertical distribution patterns of spruce and beech live fine roots (diameter ≤2 mm) were studied using a soil core method in three comparable mature stands in the Solling: (1) pure beech, (2) pure spruce and (3) mixed spruce–beech. This study was aimed at determining the effects of interspecific competition on fine root structure and spatial fine root distribution of both species. A vertical stratification of beech and spruce fine root systems was found in the mixed stand due to a shift in beech fine roots from upper to lower soil layers. Moreover, compared to pure beech, a significantly higher specific root length (SRL, P<0.05) and specific surface area (SSA, P<0.05) were found for beech admixed with spruce (pure beech/mixed beech SRL 16.1–23.4 m g⁻¹, SSA 286–367 cm² g⁻¹). Both indicate a flexible ‘foraging’ strategy of beech tending to increase soil exploitation and space sequestration efficiency in soil layers less occupied by competitors. Spruce, in contrast, followed a more conservative strategy keeping the shallow vertical rooting and the root morphology quite constant in both pure and mixed stands (pure spruce/mixed spruce SRL 9.6/7.7 m g⁻¹, P>0.10; SSA 225/212 cm² g⁻¹, P>0.10). Symmetric competition belowground between mixed beech and spruce was observed since live fine roots of both species were under-represented compared to pure stand. However, the higher space sequestration efficiency suggests a higher competitive ability of beech belowground.     

Factors affecting post-fire crown regeneration in cork oak (Quercus suber L.) trees

Cork oak (Quercus suber) forests are acknowledged for their biodiversity and economic (mainly cork production) values. Wildfires are one of the main threats contributing to cork oak decline in the Mediterranean Basin, and one major question that managers face after fire in cork oak stands is whether the burned trees should be coppiced or not. This decision can be based on the degree of expected crown regeneration assessed immediately after fire. In this study we carried out a post-fire assessment of the degree of crown recovery in 858 trees being exploited for cork production in southern Portugal, 1.5 years after a wildfire. Using logistic regression, we modelled good or poor crown recovery probability as a function of tree and stand variables. The main variables influencing the likelihood of good or poor crown regeneration were bark thickness, charring height, aspect and tree diameter. We also developed management models, including simpler but easier to measure variables, which had a lower predictive power but can be used to help managers to identify, immediately after fire, trees that will likely show good crown regeneration, and trees that will likely die or show poor regeneration (and thus, potential candidates for trunk coppicing).     

Stand structure, competition and growth of Scots pine (Pinus sylvestris L.) in a Mediterranean mountainous environment

The relationship between competition and tree growth was studied in four stands of Pinus sylvestris L. occurring in a continental Mediterranean mountain area (in the Guadarrama range, Spain), i.e., an uneven-aged stand, a stand with oak (Quercus pyrenaica Willd.) understorey, a plantation, and a mature even-aged stand. Competition was measured by a simple size-ratio distance-independent index and was negatively associated with tree diameter. This negative association was stronger in the uneven-aged, plantation and mature even-aged stands than in the stand with oak understorey. Competition was also negatively associated with current diameter increment. This relationship was moderately strong in the mature even-aged stand and weak in the uneven-aged stand and the plantation. In the uneven-aged and the mature even-aged stands, a weakly significant relationship was found between diameter growth and tree size, whereas these parameters were not associated in the stand with oak understorey. The competition index provided a better prediction of growth rate than the alternative use of diameter. Both diameter and basal area growth were greater in the uneven-aged than in the even-aged stands.     

Biomass production,carbon sequestration and nutrient characteristics of 22-year-old support trees in black pepper (<Emphasis Type="Italic">Piper nigrum</Emphasis>. L) production systems in Kerala,India

Diverse kinds of fast growing multipurpose trees are traditionally grown as support trees (standards) for trailing black pepper vines in the humid tropics of India. Apart from differential black pepper yields, such trees exhibit considerable variability to accumulate biomass, carbon and nutrients. An attempt was made to assess the biomass production, carbon sequestration potential (tree + soil) and nutrient stocks of six multipurpose tree species (age: 22 years) used for trailing black pepper vines (Acacia auriculiformis, Artocarpus heterophyllus, Grevillea robusta, Macaranga peltata, Ailanthus triphysa and Casuarina equisetifolia). Results indicate that G. robusta showed the highest total biomass production (365.72 Mg ha^?1), with A. triphysa having the least value (155.13 Mg ha^?1). Biomass allocation among tissue types followed the order stemwood > roots > branchwood > twigs > leaves. Total C stocks were also highest for G. robusta (169 Mg C ha^?1), followed by A. auriculiformis (155 Mg C ha^?1). Mean annual carbon increment also followed a similar trend. Among the various tissue fractions, stemwood accounted for the highest N, P and K stocks, implying the potential for nutrient export from the site through wood harvest. All the support trees showed significantly higher soil carbon content compared to the treeless control. Soil N, P and K contents were higher under A. auriculiformis than other species. Nitrogen fixation potential, successional stage of the species, stand age and tree management practices such as lopping may modify the biomass allocation patterns and system productivity.     

Establishment of Prosopis cineraria (L.) druce in the hot deserts of India

Prosopis cineraria (L.) Druce, commonly known as Jandi, is a deep rooted, nitrogen fixing, multipurpose tree endemic to the hot deserts of India. These trees are the essential component of the agroforestry land use system in these parts of India. The shade-intolerant tree reproduces poorly in nature and is difficult to propagate vegetatively. Germination up to 86.6% was observed after 15 days in seeds soaked in water at room temperature for 72 h. In another treatment, pouring of boiling water twice (at 0 and 6 h) over seeds and germinating after 12 h produced germination rates of 92.6%. Field establishment of containerized transplants in polythene bags (22×10 cm; 150 gauge) gave 90.3% survival after 6 months and 75.4% survival after 24 months. Seedlings were irrigated once during transplanting with 15 1 water. Bare root transplants and manual direct seeding after 6 months had a survival of 30.8 and 45.0%, respectively. Increased levels of nutrients (N, P and K), moisture content and organic carbon were observed under plantations as compared to open areas.     

Investigations on viruses from declining beech trees (Fagus sylvatica L.) in Rhineland and Westfalia,Federal Republic of Germany

Viruses of the Poty-, Potex- and Tobamo-virus groups, and presumably Nepoviruses could be isolated from degenerating beech trees (Fagus sylvatica L.) in West-Germany. They are discussed as predisposing factors of tree decline.     

Competition for light, water and nitrogen in an association of hazel (Corylus avellana L.) and cocksfoot (Dactylis glomerata L.)

Competition for light, water and nitrogen between hazel trees and cocksfoot grown under the trees was studied in two hazel plantations managed in different ways. The first plantation with a light transmission of at least 70% at grass level was compared with two control hazel and cocksfoot monocrops. The soil was a calcareous heavy clay, 1.4 m deep. Water stress during summer was severe in the intercropped stand as well as the grass- only plots, while it was much less in the sole stand of trees (without grass). Hazel tree water potential in the intercropped stand improved in the fourth year as the trees extended their roots similarly to the grass-free ones, despite their much lower canopy growth rate. The fourth year, local N fertilisation began to be effective as evidenced by the N content per leaf area unit and growth of the intercropped trees: grass root competition was high and root barriers were needed to exclude it. The second plantation was managed on a deep soil with a water table at approximately 2.5 m depth. The trees did not suffer from the presence of grass, and allowed a 15 to 75% light transmission rate. A control monocropped grass plot was established for comparison. On the basis of the multiple limitation hypothesis, a grass dry matter production model was built which accounts for radiation transmitted to the understorey, water supply, temperature and air moisture deficit in interaction with the radiation transmission rate (r2 = 0.716; 590 observations). The limits of such models are discussed with regard to insufficient knowledge on root dynamics. This revised version was published online in June 2006 with corrections to the Cover Date.