Báo cáo lâm nghiệp: "and nutrient cycling of a highly productive Corsican pine stand on former heathland in northern Belgium"

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Nội dung Text: Báo cáo lâm nghiệp: "and nutrient cycling of a highly productive Corsican pine stand on former heathland in northern Belgium"

Original article Biomass and nutrient cycling of a highly productive Corsican pine stand on former heathland in northern Belgium Neirynck Danny Maddelein Luc de Keersmaeker b Johan a a Noël Lust’ Bart Muys c a Laboratory of Forestry, University of Ghent, Geraardsbergsesteenweg 267, 9090 Gontrode, Belgium b Forest Service, AMINAL, Belliardstraat 14 - 18, 1040 Brussels, Belgium Flemish c Laboratory of Forest, Nature and Landscape Research, Catholic University of Leuven, Vital Decosterstraat 102, 3000 Leuven, Belgium 14 April; accepted 22 September 1997) (Received Abstract - Biomass and nutrient cycling were examined in a 62-year-old highly productive Corsican pine stand (Pinus nigra Arn. ssp. laricio Poiret) growing on a coarse and dry sandy soil with low exchangeable nutrient pools. Total aboveground biomass was estimated at 240 tons dry weight per hectare of which 201 tons concerned boles. The belowground biomass amounted to 46 t ha (16 % of total standing biomass). The current annual volume increment was estimated -1 at 20.6 m ha year Root study emphasized the role of the rooting depth as an important 3 -1 -1 . growth factor. Calculated uptake rates for N, P, K, Ca and Mg were respectively 50.5,1.9, 38.2, 15.6 and 3.3 kg ha year Despite an abundant nitrogen deposition (46 kg inorg. N ha year -1 -1 -1 -1 . ) between 23 and 35 % of the nitrogen demand was supplied by internal transfers. Retransloca- tion of phosphorus fulfilled 64 % of the annual requirement. The root uptake of potassium, cal- cium and magnesium were better coupled with the tree requirements. The uptake rates of Ca and Mg could be met by atmospheric deposition. The canopy leaching of potassium accounted for 70 % of the root uptake. The low uptake rates of P, Ca and Mg were inconsistent with the vig- orous growth of the stand, which could only be maintained by a high nutrient use efficiency. The monitoring of the nutrient status between 1988 and 1995 revealed an obvious decline in the concentrations of Ca, Mg, K and P due to growth dilution. (© Inra/Elsevier, Paris.) Pinus nigra / biomass / nutrient cycling / nitrogen deposition / nutrition * Correspondence and reprints E-mail: johan.neirynck@rug.ac.be
Résumé - La biomasse et le cycle des éléments minéraux d’un peuplement de pin laricio de Corse de forte production sur un sol sableux. La biomasse et le cycle des éléments minéraux peuplement de pin laricio de Corse (Pinus nigra Am. ssp. laricio Poiret) ont été étudiés dans un de 62 ans, de forte productivité, sur un sol sableux et sec, aux réserves d’éléments disponibles limi- tées. La biomasse épigée s’élévait à 240 tonnes de matière sèche par hectare dont 201 tonnes étaient incluses dans les troncs. La biomasse des racines était de 46 tonnes ha (16 % de la biomasse -1 totale). L’accroissement courant annuel atteignait 20,6 m ha anL’étude des racines a mis en 3 -1 -1 . évidence la profondeur de l’enracinement comme facteur de croissance important. Les prélève- ments réels de N, P, K, Ca et Mg s’élévaient à respectivement 50,5, 1,9, 38,2, 15,6 et 3,3 kg ha anMalgré un apport abondant d’azote (46 kg N inorganique ha entre 23 % et 35 % de ), -1 -1 -1 . la demande azotée était soutenue par le transfert interne. Les transferts internes de phosphore contri- buaient pour 64 % à la masse minérale nécessaire pour la formation des tissus nouveaux. Les pré- lèvements réels de potassium, calcium et magnésium correspondaient mieux à leurs prélève- ments apparents. Les prélèvements de Ca et Mg pouvaient être suppléés par des apports atmosphériques. Il ressort que le pluviolessivage de potassium constituait 70 % de l’absorption racinaire. Les prélèvements réels de Ca, Mg et P étaient en opposition avec la forte productivité qui ne pouvait qu’être soutenue par un usage efficace des nutrients. L’évolution de la nutrition foliaire décelait une baisse nette en teneurs de Ca, Mg, K et P engendrée par la discordance entre leurs réserves limitées et la forte croissance du peuplement. (© Inra/Elsevier, Paris.) nigra / biomasse / cycle des éléments minéraux / azote / nutrition minérale Pinus Today, interest is aroused about the 1. INTRODUCTION mechanisms that sustained the vigour of Over 60 % of the Flemish forest area the Corsican pine stands growing on these is located on sandy soils. Because of its sandy soils with low exchangeable pools. low drought sensitivity, the availability of In recent decades, these forest soils were, suitable provenances and, especially, its in addition, liable to high acid loads and high growth rate, Corsican pine has in were gradually impoverished due to leach- recent decades become one of the main ing of base cations displaced from tree species on these sandy soils, and occu- exchange sites. Attention was therefore pies around 30 % of these areas. drawn to the changes in nutrient cycling, A decline in Corsican pine vigour was nutrient soil turnover and stand nutrition of observed during the 1980s as a result of these stands in connection with this vigour. severe frost and infections caused by fungi (Brunchorstia pinea and Sphaeropsis sap- There are few studies concerning inea), but most Corsican pine stands have biomass and nutrient cycling of Corsican recovered well and presently produce con- pine stands growing on nutrient poor soils siderable amounts of timber. Present vol- [16, 25]. The present study was carried ume increments of some stands can even out to assess the organic matter and nutri- be called excessive compared to the yields ent distribution in a highly productive Cor- found in yield tables from stands belong- sican pine stand on a former heathland. ing to same age and yield class. This This research also aimed to calculate stand increased tree growth is also noted for nutrient uptake and requirement and to other tree species and is often associated compare the uptake rates with the present with chronic nitrogen deposition in forest nutrient pools and the nutrient status. ecosystems [1, 29, 41].
2.2. Tree selection and 2. MATERIALS AND METHODS sampling Five sample trees were selected on the basis of the basal area distribution of the trees; three 2.1. Study area sample trees were representative of the sam- ple median, and the two remaining trees The research was conducted in a 62-year- represented the lower and upper quartile of the old Corsican pine (Pinus nigra Arn. ssp. lari- basal area distribution (see table II). cio Poiret) stand located in the Pijnven Forest felled in 1992. Before The five trees (51°10’ N, 5°20’ W), near Hechtel (northeast- were felling, however, all branches were harvested ern Belgium). The forest covers about 800 individually by means of a tower waggon and hectares and is mainly composed of first gen- were weighed immediately after harvest. In eration pine stands established on former heath- addition, the diameter 3 cm from the branch lands and sand dunes. The forest is located at base and the branch length of every branch were the edge of the High Campine plateau and measured in the field. From each whorl, one ranges in elevation from 50 to 58 m. The randomly selected branch was sampled Campine plateau originates from a mixture of completely; the needles were stripped from the tertiary sands and gravel-rich sands deposited branches and separated according to their age. by the Meuse River. During the Pleistocene The branches were chopped into four size these sands were covered by aeolian sand classes (diameter: < 1, 1-2, 2-5 and > 5 cm). deposits. The fresh weight of every fraction was imme- Mean annual temperature is 9.0 °C with diately weighed on the spot. Subsequently, sub- January and July means of 1.5 °C and 16.7 °C, samples were taken from every fraction for dry respectively. Mean annual precipitation is weight determination and chemical analysis. 799 mm. Precipitation during the growing sea- Each bole was sawn into 1 m long logs; at son (May-October) averages 430 mm. The every 3 m a disc of about 3 cm thickness was prevailing wind direction is southwest. The removed for laboratory analysis. The disc frost period extends from the end of October dimensions, bark thickness and the fresh until the end of April. weights were recorded immediately. The total stem volume and basal area 463 m and 39.9 m per hectare, 3 2 The samples of branches and needles were amounts to dried for 48 h at 80 °C and weighed again. The The crop comprises 460 stems respectively. haand attains a mean height of 22.6 m. From -1 wood and bark pieces were dried at 80 °C to constant weight. The samples were ground in 1954 onwards thinnings have been carried out with a frequency of 6 years; data of thinning a wood mill before chemical analysis. volumes before 1951 were not available. The stumps of three of the Corsican pines Between 1951 and 1991, 252 m comprising 2 (one sample median and lower and upper quar- 3 021 trees planting density was (ha original ) were -1 tile) were excavated over a surface formed by the harvested per hectare. 10 000 stems intersection of the perpendicular lines that pass The stand is moderately infested by Sphaerop- the midpoints of the lines connecting through sis sapinea. the centre of the sample tree to the centre of the The coarse sandy soil has a massive, com- nearest neighbouring trees [27]. The roots were pacted and cemented spodic B horizon and is cleaned, weighed and subdivided into four diam- classified as a Haplic Podzol. The permeabil- eter classes (0.5-1, 1-2, 2-5 and > 5 cm). The ity of the Bh1 and Bh2 horizons is particularly fine rootlets thinner than 0.5 cm were not sam- low and prevents deep penetration of roots. pled. The entire sample of rootlets (0.5-2 cm) From 80 cm depth downwards, the parent was taken for analysis, whereas subsamples material is locally enriched by narrow clay and were taken from the bigger root fractions. gravel layers. The pH-H and base satura- O 2 tion remain constant and very low throughout the solum to a depth of 90 cm (table I). The 2.3. Estimation of biomass biomass of the forest floor is 57.2 tons ha . -1 and nutrient contents Its C/N ratio is 42, whereas it ranges between 32 and 41 in the surface soil. The C/N ratio of The fresh weight data obtained from the the C horizon (30 to 90 cm depth) is below selected branches were used to derive regres- 25 %.
and the current foliage production [7]. An indi- sions relating fresh weight of needles (three cation of the extent of the internal recycling age classes) and branch wood weight (total of elements was obtained by subtracting uptake wood weight of the branch and wood weight of from requirement. the four size classes) to branch diameter, branch length, whorl position and fresh weight of the Current nutrient accumulation in the wood branch (i.e. including needles). Fresh weights increment was calculated by subtracting the of the separate crown tree parts from every nutrient contents of the boles and branches sample tree could then be calculated. The fresh (four size classes) of 1988 from those of 1995, weights of the branch wood thicker than 5 cm assuming no temporal variation in woody tis- were calculated by subtracting the wood weight sue concentrations. Litter was collected using of branches < 5 cm from the total branch wood litter traps. Canopy leaching was calculated weight. The regressions that relate the fresh from detailed measurements of precipitation weights of different branch and needle frac- and throughfall fluxes. tions to independent variables are listed in Bolewood increments were calculated from table III. The regression equations were all annual measurements of height and girth incre- highly significant (P < 0.001). ments in a permanent sample 0.25 ha plot in The dead branches and the cones from each which throughfall and litterfall measurements sample tree were pooled together, weighed and were also performed. The girth measurements a subsample was taken to determine fresh started in 1988 and have continued until 1995 weight, dry weight and chemical analysis. with the exceptions of 1993 and 1994. The heights of the trees were measured with a The dry branch wood and needle weight of Blume-leiss altimeter in 1988, 1992 and 1995. every tree was estimated by reducing the cal- The height increments between 1988 and 1992 culated fresh weight by the average moisture were obtained by measuring the interwhorl content measured on the sampled branches and lengths from felled trees. The bole volumes needles. were calculated according to the cubing method The nutrient content of every tree part was of Berben [4]. Biomasses of the boles were calculated from its dry weight multiplied by estimated from bole volumes assuming that its nutrient concentration measured at the the relationship between bole volume and respective sampling height. biomass found in 1992 was also valid for the The biomass of the stand was estimated by preceding years. Branch wood increments were the sample tree biomass by the assumed to follow the measured proportionali- multiplying ratio of stand basal area to sample tree basal ty with bole volume. area [2]. A second method consisted of Litterfall (foliage, branches and cones) mea- determining the ratio of stand volume to sam- for 1988-1992 were provided by surements ple tree bole volume. The nutrient contents of of Muys [20]. Litter was collected at a height the different tree components were calculated 1 m using five randomly located 0.28 m litter in the same way. It was concluded that the traps equipped with nylon bags at 2-week inter- method involving bole volume was more accu- vals. rate for the estimation of total stand biomass, as Bulk precipitation (BP) and throughfall (TF) its coefficient of variance was much lower than measured from February 1992 to January the tree basal area proportion method (6 % vs. were 1993. Throughfall and the bulk precipitation 12 %). Further calculations of weights and (measured on a nearby clearcutting) were sam- nutrient contents of the 14 component parts pled with each four randomly distributed bulk were performed using the sample tree bole vol- collectors. They consisted of a polyethylene ume. funnel (15 cm diameter) which was connected to a 2 L polyethylene bottle. A nylon mesh was placed in the funnel to avoid contamination by 2.4. Nutrient fluxes large particles. The collectors were sampled and replaced by distilled water rinsed collectors on a monthly basis. Net throughfall (TF-BP) Nutrient uptake was calculated as the quan- of base cations was adjusted for the contribu- of nutrients incorporated into the annual tity tion of particle interception deposition by the wood increment plus litterfall, plus canopy canopy exchange model of Ulrich [33]. In this leaching. Requirement was calculated as the model Na is assumed not to be influenced by sum of the annual elemental wood increment
forest floor were extracted with Aqua Regia exchange and Ca-, Mg- and K-bear- canopy ing particles are assumed to have the same reagens. Total concentrations of Ca, Mg and mass median diameter as Na- containing par- K were measured by ICP. ticles [9]. The particle interception deposition (DD) of Ca, Mg and K were estimated by mul- 2.6.3. Rain and throughfall tipying the bulk deposition with the calculated dry deposition factor (TF The . )/BP -BP Na Calcium, magnesium and potassium in the canopy exchange rates of the base cations were rainwater were measured by atomic absorp- obtained by subtracting the estimated dry depo- tion spectrophotometry. Nitrogen (NH and 4 sition amounts from the net throughfall (TF- NO and phosphorus were determined ) 3 BP-DD). Canopy leaching of Ca, Mg and K colorimetrically. minus canopy leaching of Ca, Mg and K asso- ciated with foliar excretion of weak acids was further assumed to equal uptake of H and NH 4 3. RESULTS [9, 10]. Canopy leaching of P was assumed to be zero. 3.1. Stand increment and biomass 2.5. Nutrient status Between 1988 and 1995 the current Nutrient status was measured by sampling annual volume increment was estimated needles from five to ten dominant to codomi- at 20.6 m ha The mean height and girth 3 -1 . nant trees in the plot during October and increment averaged, respectively, 0.35 m November. The sample trees were representa- and 1.6 cm yearRadial increment was . -1 tive of the mean defoliation level of the plot subject to strong year-to-year variation [3]. The needles were taken from the upper with maximum girth increment occurring third of the crown (between the 5th and 9th whorl). The sampling was carried out in such a in 1991-1992. way that all orientations of the crown were The bark accounted on average for included. 24 % of the total bole volume, although at the stem base bark proportions as large as 35 % were observed. 2.6. Chemical analysis Stemwood accounted for on average 60 % of the total tree biomass and 71 % of 2.6.1. Tree component aboveground stand biomass (table IV). The woody part represented 85 % of the determined by the Kjeldahl Nitrogen was bole dry weight. Roots, bark and branches method, using Se catalyst. Ashes were as extracted with a 1 N HNO solution. Magne- 3 were 16, 10.8 and 8.1 %, respectively, of sium was determined by atomic absorption the total stand biomass. Foliage and dead spectrophotometry. Calcium, potassium and branches were little less than 3 % each. sodium were measured by flame emission spec- The first and second year’s needles trometry. Phosphorus contents were measured colorimetrically using vanadomolybdate respectively, 53 and 36 % of the were, kg ha Branches ). -1 reagent. = 8 265 foliage (total with thicknesses ranging between 2 and 2.6.2. Soil and forest floor 5 cm and twigs < 1 cm accounted for 50 and 28 % of the total branch weight, Total N of the soil and the forest floor sam- respectively. The mass of thicker branches was determined by Kjeldahl digestion. ples (> 5 cm) was very small (< 1 %). Total P was measured after total destruction Coarse roots (> 5 cm) constituted the in HClO (13 %) by ICP. The exchangeable 4 largest part of the total root biomass of Ca, Mg and K of the soil were measured by ICP (by 0.1 N BaCl extraction). Ashes of the 2 the tree (80 %). Roots with diameter rang-
ing from 2 to 5 cm represented 16 % of developed with well-formed closely was the total weight of the root system, linked lateral roots penetrating the com- whereas fine roots (0.5-2 cm) represented pacted subsoil along cracks up to a depth only appromixately 4 % of the below- of 240 cm. Lateral roots and rootlets were ground biomass. The weights and the interweaved to form dense vertical root shapes of the root systems from the exca- mats. vated trees varied according to the per- meability of the subsoil. The smallest sam- ple tree had developed a compact surface 3.2. Nutrient concentrations, contents root system (rooting depth only 95 cm), and nutrient distribution on top of a cemented spodic horizon, with a total biomass of 54 kg (table II). The The average nutrient concentrations of two other root systems (from the median the different tree parts are listed in table V. and 3rd quartile) were more vigorous and Needles, twigs, smaller branches and their dry weights amounted to 116 and rootlets contained the highest nutrient lev- 129 kg, respectively. A shallow tap root els. Concentrations of all nutrients were
lowest in the and the woody parts in the roots ranged between 9 and 15% coarse of the total stand nutrient content. roots. Per hectare, 659 kg N, 36 kg P, 188 kg K, 220 kg Ca and 49 kg Mg were stored in 3.3. Nutrient pools versus the stand biomass (table VI). Although nutrient fluxes comprising only 11 % of the total biomass, branches and needles were important pools for K (table VII). Almost 45 % of the total The nutrient capital of K, Ca and Mg in K content of the trees was located in the the trees represented, respectively, 46, 36 crown. Phosphorus was equally appor- and 46 % of the ecosystem total (with min- tioned to the boles and the crown (43 % eral pools defined to a soil depth of 90 cm) each). Stem boles constituted a major sink (table VIII). The amounts of total N and P for Ca, Mg and N with, respectively, 57, sequestered in the stand are small com- 52 and 49 % of their respective tree nutri- pared to the total contents stored in the ent content. The proportion of elements mineral soil and the forest floor.
which was subdivided into 17.7 kg NO only important -N 3 Canopy leaching was for K (27.0 kg ha The presence of Ca ). -1 and 28.1 kg NH The net throughfall of -N. 4 inorganic N (27.2 kg) was mainly com- and Mg in the net throughfall may be posed of ammonium, which can be ascribed to interception deposition of Ca- explained by the high gaseous or particle and Mg-bearing particles. The contribu- interception of NH The dry deposition . x tion of this dry deposition was up to 25 % of N might have been underestimated due of the throughfall fluxes. Total inorganic to uptake of NH Additions of P by rain- . x N in throughfall amounted to 45.8 kg ha , -1
fall were mostly below the detection limit LFH nutrient pool to obtain a crude insight and did not exceed 0.5 kg ha . -1 in percent soil turnover rate irrespective of atmospheric inputs and leaching losses. Annual litterfall was estimated at This ratio was especially high in the case 3 067 kg haof which 72 % was foliage, , -1 of K, Mg and Ca in decreasing order of and contained 30.8 kg N haCalcula- . -1 importance. tion of annual N immobilization in the boles (NPP 8 949 kg ha and branches ) -1 = (NPP 1 076 kg ha yielded a value of ) -1 = 3.4. Nutrition 19.7 kg haAnnual uptake rates of K . -1 were estimated at 38.2 kg ha Canopy . -1 losses accounted for 70 % of total root Monitoring of the nutrient status uptake of K. The amounts of P, Ca, K and between 1988 and 1995 clearly revealed Mg returned in litter were of similar mag- an obvious decline in nutrient concentra- nitude to the amounts which were accu- tions of P, K, Ca and Mg (table IX). In the mulated in the wood. current year’s foliage this decrease had ceased during the last years but the steady The requirements for N and P exceeded decline continued in the second year’s nee- their uptake rates, indicating the presence dles for P, Ca and Mg. Nitrogen levels of internal transfers. Retranslocation of P remained constant with the exception of fulfilled approximately 64 % of the annual the second year’s needles for which a requirement. The internal transfer of P slight increase was noted. According to constituted 77 % of the content the criteria of Van den Burgh [34, 35], sequestered in the current foliage. For nutrient concentrations of P, Ca and Mg nitrogen 28 kg N (35 % of annual require- shifted from a sufficient to an insufficient ment) was recovered from older tissues to level. The levels for K dropped from an support growth in younger needles. This optimum to a sufficient range. Nitrogen amount might have been overestimated levels were maintained in a sufficient since no allowance was made for a pos- range. sible uptake of NH by the crown. How- x ever, if NH was taken up and exchanged x These shifts were also observed for the for base cations, only potassium would element ratios with highest values occur- have been involved in this exchange, as ring in 1992. Evaluation of nutrient ratios canopy losses of Ca and Mg were negli- marked a possible nutrient imbalance gible. Canopy losses of K (27.0 kg or between N and P in 1992 and 1995. 0.69 keq) can be apportioned to excretion or exchange for NH and H (canopy 4 uptake of NH and H must balance canopy 4 4. DISCUSSION leaching of K). If we assume that only NH uptake accounted for the potassium 4 Total standing biomass of the 62-year- losses, maximum 9.6 kg NH would -N 4 old Corsican pine stand amounted to 286 have been absorbed by the canopy. This tons dry weight per hectare, of which 16 % would imply that still at least 18 kg N was is in the belowground portions. Total involved in retranslocation. aboveground biomass of the Pijnven stand The uptake of K, Ca and Mg was better was estimated at 240 tons ha The total . -1 coupled with the tree requirements, biomass of 58-year-old Corsican pine although root uptake of K exceeded the stands growing on blown sands at Culbin potassium demand by 24 %. Forest in Scotland extended from 155 (control) to 221 tons ha (highest level -1 The elemental uptake rate was of mineral and of N dressing) [23], whereas Ovington expressed proportion as
[22] estimated the aboveground biomass increment of 15-17 m hayear 3 -1-1 [4], an of a 48-year-old Corsican pine plantation likely to be expected for stands was more in the United Kingdom at 242 tons ha . -1 belonging to same age and yield class. The Miller and Cooper [ 15] and Proe et al. [23] high productivity of the stand may be due reported root proportions of 19 % and to the development of deep rooting lateral 12 % in Corsican pine stands (Pinus nigra roots penetrating the compacted subsoil ssp. maritima) growing on blown sands along friable cracks up to a depth of (Culbin Forest) at an age of 39 and 58 240 cm. The root study clearly stressed years, respectively. Minderman [ 18] the presence of a compacted to cemented reported root proportions of 16.6 % in 22- B horizon as a severe impediment to stem year-old pole-stage crops of Pinus nigra and height growth. Toth and Turrel [32], austrica. var. Timbal et al. [30] and Heinze et al. [13] Stemwood accounted for on average pointed out that Corsican pine tree growth 71 % of the aboveground biomass. Bark was determined to a large extent by the comprised 24 % of the bole volume and available root space, which ensured a more 15 % of the total bole weight. Similar bark favourable water balance. proportions were reported by Tomanic The vigorous increments might also be [31]. ascribed to the abundant airborne deposi- The foliage of the Pijnven stand tion of nitrogen (46 kg inorg. N hayear -1-1 amounted to nearly 8 300 kg haand con- -1 in throughfall). Since N was an important stituted 3.4 % of the aboveground growth-limiting factor in the past, it is con- biomass. Other studies reported foliage ceivable that relief from N deficiency by masses ranging from 5.6 [24, 40] to 21 atmospheric deposition favours current -1 ha [25]. tons growth. Miller and colleagues [15, 16] The current annual increment of the reported large increases in basal area and 3 -1 m ha . -1 year stand amounted to 20.6 volume increments after application of nitrogen in a severely nitrogen deficient the tables of Berben According yield to
pole-stage crop of Corsican pine on blown Boles and stumps contained about 65 % of the total Ca, Mg and N content. This sands at Culbin Forest. Maximum volume proportion is expected to continue to rise increment occurred when nitrogen con- with increasing age. The high allocation of centrations in the needles of top-whorl nitrogen to the boles and roots can also be foliage rose to 2 %. In the same stands explained by an alteration of nitrogen allo- Proe et al. [23] observed a long-term N cation patterns inflicted by the high nitro- fertilizer growth response, achieved gen deposition. An abundant external through internal transfers of nitrogen. Blok nitrogen supply by fertilizer may result in et al. [6] and Goor [38] noted only small a higher retention of nitrogen in the tree responses in height growth on nitrogen [36], but can also provoke a shift in nitro- dressings in young Austrian and Corsican gen storage towards the stem bole and pine stands in the Netherlands. Nys et al. roots. Proe et al. [23] observed marked [21] came to similar conclusions in fertil- nitrogen content increases by 44 % and a ization experiments in Sologne (France). concomitant shift in distribution of nitro- gen between components in 58-year-old Nitrogen fertilization in Scots pine Corsican pine stands, 22 years after nitro- stands do not always entail a sustainable or gen fertilizer application. Proportions of even a transient improvement of growth, nitrogen in boles and stumps of fertilized even when nitrogen is growth limiting. Corsican pine plots increased to 55 % Initially they result in growth increases compared with 45 % in the untreated plots. but they are, however, often followed by a This occurred at the expense of twigs and phase of growth suppression due to deple- foliage, which share dropped by 6-7 %. tion of nutrients that are not provided by The calculated annual uptake of nitro- the fertilizer [11]. Nitrogen deposition can gen matched the average value reported stimulate growth beyond the capacity of by Cole and Rapp [7] for temperate conif- the soil to supply other limiting nutrients erous forests (table X). Higher uptake val- [28]. The results of this study indicate that ues of nitrogen were reported by Ranger other elements like phosphorus and mag- [25] and Miller et al. [17] for nitrogen- nesium have become more growth limiting fertilized Corsican pine plots. Despite the than nitrogen and therefore a lower growth abundant external supply of nitrogen, rate was perhaps more likely to be between 23 and 35 % of the nitrogen requirement (between 18 and 27.6 kg) was expected.
satisfied ing. The uptake of ammonium and its by internal transfers. This is sur- prising, although other nitrogen experi- exchange for potassium as shown by field confirm that the N status of the tree investigations and ecophysiological exper- ments does not affect the efficiency of N cycling iments [26] could have reinforced these losses. The uptake rates of Ca and Mg, or the amount of N translocated [8, 14, expressed as a proportion of the available 19]. Moreover, the withdrawal of mobile nitrogen compounds from the abundant mineral soil and LFH pools, were lower. In contrast with potassium their elemental storage sites requires less energy expen- diture than uptake of nitrate from the soil inputs by bulk precipitation and dry depo- [5]. Soil solution analysis by suction ten- sition satisfy to a great extent the require- sion lysimeters yielded nitrate concentra- ments of the trees. The deposition of atmo- tions averaging 17.6 mg·L NO in -1 3 spheric base cations in Europe is, however, -N the parent material, which indicated that following a declining trend in recent the uptake capacity of the ecosystem was decades [12]. finite. uptake values for P, Ca and Mg The represented less than a half of the listed On the basis of the large phosphorus soil pool, the uptake rates were unexpect- average values for temperate coniferous forests (table X). The calculated nutrient edly low (table X). Soil solution analysis in the surface soil and the subsoil did not efficiency (above ground produc- use tion/unit of nutrient uptake) for those ele- detect any dissolved inorganic or organic phosphorus. Its absence could be largely ments is far above those found in a variety attributed to the strong biological reten- of forest ecosystems [7]. It is unclear whether a future decrease in their avail- tion within surface soils and the high geo- chemical control over phosphorus move- ability will be met by a further increase ments in the subsoil contributing to a tight in nutrient use efficiency (more cycling of phosphorus within the ecosys- retranslocation or higher production per tem [39]. Moreover, the high aluminium unit of nutrient consumed) or whether the concentrations in the soil solution (con- response will be a decline in growth. centrations of which averaged 8 mg·L -1 Monitoring of the nutrient status in the B and 19 mg·L in the C horizon) -1 revealed a decrease in concentrations of might have decreased its availability by Ca, Mg and P that was especially marked provoking precipitation of P as Al-phos- in the second year’s needles. Applying the phates. At low pH values these poorly sol- criteria to evaluate the nutrition of half uble phosphate salts are known to regu- year’s needles given by Van den Burg [34, late P availability [5]. The decreasing P 35], the nutrient status of P, Ca and Mg levels of the litter can, in addition, trigger was shifting from a suboptimal to an insuf- a stronger biological retention in the future. ficient range. Nitrogen levels remained The low P availability may be the reason constant in current foliage but increased for the high retranslocation of phospho- in the older needles. They did not attain rus (64 % of requirement) within the trees. excessive values, which are to be expected in the surroundings of pig farms. Van Dijk The uptake of basic cations was obvi- limited by the low available min- et al. [37] recorded higher nitrogen levels ously (2.2 %) in Corsican pine stands, which eral soil and forest floor nutrient pools. For potassium, annual uptake amounted were heavily affected by Sphaeropsis sap- to 16 % of the available nutrient pools. inea in the southern part of the Nether- The high potassium uptake was especially lands. A drastic increase of nitrogen in the needles as a consequence of the chronic attributable to the severe canopy losses, since this element is very subject to leach- nitrogen deposition has perhaps been off-
forest ecosystems, Bioscience 39 by a shift towards the woody parts or a (1989) set 378-386. gradual increase in foliar biomass. Aber Ando T., Estimation of dry-matter and growth [2] et al. [1] suggested that in the initial stages analysis of the young stand of Japanese black of the development of nitrogen saturation, pine (Pinus thunbergii), Adv. Front. Plant Sci. constant additions from chronic deposi- 10 (1965) 1-10. tion would not lead to a detectable increase Anonymous, Manual on methods and criteria [3] for harmonized sampling, assessment, moni- in foliar nitrogen concentration, but rather toring and analysis of effects of air pollution to a gradual increase in foliar biomass with on forests, PCCW, Hamburg, 1994. a constant nitrogen concentration. Berben J., Dendrometrische studie van de Cor- [4] sikaanse den, LISEC, Genk, 1983. Moreover, the nutrient ratios exhibited Binkley D., Forest Nutrition Management, John [5] a decline indicating the development of a Wiley & Sons, New York, 1986. nutrient imbalance. It is, however, doubt- [6] Blok H., van den Burg J., Oldenkamp L., ful whether this decline was due to a com- Bemesting en minerale voeding van naaldhout petitive inhibition by NH in the soil or 4 op jonge, zandige mariene gronden, Neder- lands Bosbouwtijdschrift 49 (1977) 281-294. an ammonium-cation exchange. The mod- [7] Cole D.W., Rapp M., Elemental cycling in for- erate nitrogen levels found in the needles est ecosystems, in: Reichle D.E. (Ed.), Dynamic (1.4 %) do not, however, support the pres- Properties of Forest Ecosystems, Cambridge ence of a strong competition between University Press, Cambridge, 1981, pp. ammonium and the other nutrients. We 341-409. suggest therefore that the steady decrease [8] Crane W.S.B., Banks J.C.G., Accumulation and retranslocation of foliar nitrogen in fertil- in Ca, Mg and P and their element ratios ized and irrigated Pinus radiata, For. Ecol. was more related to the mismatch between Manag. 52 (1992) 201-223. the low available nutrient pools and the Draaijers G.P.J., Erisman J.W., A canopy bud- [9] vigorous growth of the stand which led to get model to assess atmospheric deposition from throughfall measurements, Water Air Soil a dilution of nutrients. Poll. 85 (1995) 2253-2258. [10] Draaijers G.P.J., Erisman J.W., Spranger T., Wyers G.P., The application of throughfall ACKNOWLEDGEMENTS for atmospheric deposition mon- measurements itoring, Atmos. Environ. 30 (1996) 3349-3361. [11]Foerster W., Zusammenfassende ertragskund- This research was financed by the Ministry liche Auswertung der Kiefern-Düngungsver- of the Flemish Community and was executed in suchsflächen in Bayern - ein Beitrag zur charge of the minister of the environment of Beschreibung des Kiefernwachstums in Flanders, Belgium. The monitoring of incre- Süddeutschland, Forstl. Forschungsberichte ment, throughfall, nutrient status and soil liquid München (105), 1990. phase was coordinated by the Institute of [12] Hedin L.O., Granat L., Likens G.E., Buishand Forestry and Game Management. This moni- T.A., Galloway J.N., Butler T.J., Rodhe H., toring took place within the framework of the Steep declines in atmospheric base cations in International Co-operative Programme on regions of Europe and North America, Nature 367 (1994) 351-354. Assessment and Monitoring of Air Pollution Effects on Forests. [13] Heinze M., Fiedler H.J., Van Vien N., Stan- dort, Ernährung und Wachstum alter Schwarz- The authors want to thank Forest Service kiefem im Naturschutzgebiet Reinsiädter Berg, engineer Erik van Boghout for his permission Bez. Gera (DDR), Arch. Naturschutz Land- to use the plot and the supply of technical sup- schaftsforsch. 29 (1989) 225-245. port during the field work. [14] Lim M.T., Cousens J.E., The internal transfer of nutrients in a Scots pine stand. II. The patterns of transfer and the effects of nitrogen avail- ability, Forestry 59 (1986) 17-27. REFERENCES [15]Miller H.G., Cooper J.M., Changes in amount and distribution of stem growth in pole-stage [I] Aber J.D., Nadelhoffer K.J., Steudtler P., Corsican pine following application of nitro- Melillo J.M., Nitrogen saturation in northern gen fertilizer, Forestry 46 (1973) 157-190.
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