Despite its low nutrient concentration, the high amount of biomass accumulated in the tree stem makes it an important nutrient sink. Hence, nutrient loss through timber removal at harvesting is a major cause of nutrient impoverishment at some forest sites. The present study was designed to test the following hypotheses: (a) nutrient allocation in the different tree tissues would be affected by (re)translocation processes related with leaf senescence; hence, (b) timber may have a higher nutrient concentration during the defoliated period (in deciduous species); and consequently, (c) modifying harvesting time could influence nutrient export. To test these hypotheses, the present study analyzes the intra-annual dynamics of foliar and trunk nutrient concentration in a planted teak (
Forest plantations have increased globally during recent decades and now account for 290 × 106 ha, which is 7% of the global forest area, in response to the growing demand for timber, pulp, energy and other goods (
Teak (
In order to address the lack of sustainability and the possible decrease in long term production caused by nutrient depletion, authors of previous studies (
Since teak is a deciduous species, nutrient allocation in the different tissues of the tree is affected by the (re)translocation processes related to leaf senescence (for a review, see
The present case study was conducted in a planted teak (
The exact location of the study was the “El Mango” stand (10.211° N, 85.573° W) at an elevation of 115-120 m a.s.l. This is a mature stand planted on previously grazed land at the beginning of the study in 1989 (
Foliar and trunk nutrient concentration were monitored over nine sampling times from June 2012 to August 2013 (
Tissue samples were analyzed at the
Foliar nutrient concentration varies during the year with differing intensity depending on the element, although the pattern presents very high variability (
Retranslocation can be also observed in the P, K and Zn foliar concentration results (
The establishment of foliar concentration references is considered a useful tool to evaluate the nutritional status of a stand and foliar analysis has been used for diagnostic purposes and for designing nutritional and fertilization plans (
The observed increase in N concentration in the trunk corresponds with the previously mentioned decrease in N concentration in senescing leaves (
The increase in N and P concentration in the trunk between December and January corresponds directly with the decrease in foliar concentration shown at the same time (
Trunk nutrient concentration is very low compared to foliar concentration (
Timber harvested in the dry period (January to March) has an average N-P-K concentration of 0.25, 0.07 and 0.14%, respectively, while the nutrient concentration is 0.19, 0.05 and 0.08%, respectively, if harvested between August and October. Thus a reduction of 24, 29 and 43% of the N-P-K exported through timber harvesting can be achieved under this scenario.
Timber harvested in December has an average N-P-K concentration of 0.18, 0.05 and 0.12%, respectively, which will reduce the N-P-K exported through timber harvesting by 28, 29 and 14% compared to the N-P-K exported when timber is harvested in the dry period (January to March).
Based on the present results, harvesting between August and October would mean a major reduction in N-P-K export, due to the lower concentration of these nutrients in the wood and bark during that period of the year. However, this period may present certain logistic problems for harvesting operations, as it falls within the normal rainy period. A possible solution may be to perform some of the harvesting operations at this time (
Nutrient export through timber harvesting has been reported to be of specific importance for N, P and K in the various teak plantations studied in Central America (
This study provides promising results which could lead to an improvement in nutrient management and planted forest sustainability. However, a more detailed study over several years with a larger number of samples and locations is necessary to confirm the observed trends. Furthermore, future research should be aimed at analyzing the differences in trunk nutrient concentration along the stem at different heights (
Several authors have studied the temporal and spatial (radial and height variation) nutrient dynamics within stem wood and have highlighted a general tendency for nutrient translocation from senescing sapwood and hardwood to active sapwood (
The results of this study reveal the influence of nutrient resorption or (re)translocation processes associated with leaf senescence in the intra-annual dynamics of foliar and trunk nutrient concentration in planted teak forests. This confirms the hypothesis that trunk nutrient content is lower during wet periods, when the teak trees are in foliage. Therefore, shifting harvesting time can be an efficient approach to reduce nutrient export through timber extraction. Indeed, harvesting between August and October will reduce the N-P-K exported by 24, 29 and 43%, respectively, as compared with the conventional harvesting time carried out during the dry period (January-March). However, the period August-October corresponds to the rainy season in northern Costa Rica, and this rises several logistical and operational difficulties. Alternatively, harvesting in December - at the beginning of the dry period but before leaf senescence - will minimize the operational and logistical difficulties, whilst reducing the N-P-K exported by 28, 29 and 14%, respectively.
We acknowledge the kind collaboration of the Cabalceta family for allowing the use of their private forests to conduct this study, and in particular Edwin Cabalceta Yurien Gutiérrez (Pilo), Sabas Elijio Ortiz (Saba) and Randall Iván González for their help during the fieldwork. The authors also thank Adam Collins and the personnel of the Natural Resources Laboratory at CIA (UCR) for their help and comments in the production of this paper. This study was financed by PCI-AECID as part of the MACOSACEN Project.
Pictures of the sampled planted teak (
Macronutrient foliar concentration variations over time (from June 2012 to August 2013) in a planted teak (
Macronutrient trunk (wood and bark) concentration variations over time (from June 2012 to August 2013) in a planted teak (
Topsoil (0-40 cm) characteristics of 12 sampled plots in a teak (
Parameter | Mean and 95%confidence interval | Criticalvalues* |
---|---|---|
pH | 5.8 (5.5, 6.1) | 5.5 |
C org [%] | 2.18 (1.93, 2.43) | - |
Sand [%] | 41 (33, 49) | - |
Silt [%] | 19 (14, 24) | - |
Clay [%] | 39 (36, 42) | - |
Acidity [cmol (+) L-1] | 0.18 (0.17, 0.19) | 0.5 |
Ca [cmol (+) L-1] | 18.3 (17.08, 19.52) | 4 |
Mg [cmol (+) L-1] | 6.56 (5.77, 7.35) | 1 |
K [cmol (+) L-1] | 0.37 (0.28, 0.46) | 0.2 |
ECEC [cmol (+) L-1] | 25.41 (23.5, 27.32) | 5 |
AS [%] | 0.7 (0.6, 0.8) | 3 |
P [mg L-1] | 2 (1, 3) | 10 |
Zn [mg L-1] | 1 (1, 1) | 3 |
Cu [mg L-1] | 10 (8, 12) | 1 |
Fe [mg L-1] | 49 (36, 62) | 10 |
Mn [mg L-1] | 17 (13, 21) | 5 |
Diameters at breast height (DBH, cm) of trees sampled to monitor within-year foliar and trunk nutrient concentration in teak (
Sampling date | Sample A(trees 1, 2, 3) | Sample B(trees 4, 5, 6) | Sample C(trees 7, 8, 9) | Total average(trees 1 to 9) |
---|---|---|---|---|
26-Jun-12 | 35.1 ± 5.9 | 29.4 ± 2.0 | 28.1 ± 5.8 | 30.9 ± 3.2 |
26-Aug-12 | 32.2 ± 6.5 | 31.8 ± 3.5 | 33.2 ± 1.1 | 32.4 ± 2.2 |
7-Oct-12 | 32.5 ± 4.1 | 32.7 ± 4.0 | 32.0 ± 3.6 | 32.4 ± 1.9 |
3-Dec-12 | 31.4 ± 3.0 | 33.1 ± 1.9 | 31.4 ± 2.0 | 32.0 ± 1.3 |
27-Jan-13 | 33.0 ± 4.3 | 36.2 ± 3.1 | 33.1 ± 5.8 | 34.1 ± 2.5 |
24-Feb-13 | 30.1 ± 5.5 | 31.9 ± 1.6 | 32.1 ± 4.7 | 31.4 ± 2.2 |
21-Mar-13 | 28.6 ± 5.1 | 28.4 ± 0.7 | 30.9 ± 5.1 | 29.3 ± 2.2 |
28-Jun-13 | 32.3 ± 1.5 | 33.2 ± 3.9 | 32.7 ± 2.5 | 32.7 ± 1.4 |
12-Aug-13 | 32.5 ± 4.9 | 32.5 ± 3.8 | 33.1 ± 2.6 | 32.7 ± 1.9 |
Fig. S1 - Micronutrient foliar concentration variations over time (from June 2012 to August 2013) in a planted teak (Tectona grandis L.f.) forest in Guanacaste, Costa Rica.
Fig. S2 - Litter nutrient concentration variations over time (from January 2013 to March 2013) in a planted teak (Tectona grandis L.f.) forest in Guanacaste, Costa Rica.
Fig. S3 - Micronutrient trunk (wood and bark) concentration variations over time (from June 2012 to August 2013) in a planted teak (Tectona grandis L.f.) forest in Guanacaste, Costa Rica.