Review of "Physiological ecology of forest production" by J. J. Landsberg.

Accumulation of nitrogen in above-ground components of Pinus radiata Don trees was measured annually in winter between ages 2 and 12 years, and stand estimates of above-ground current annual nitrogen uptake were derived. The trees, which were growing at Puruki in stands without known nitrogen or water limitations to growth, were subjected to different intensitie thinning commencing after age 6.

At age 2 the stands contained 20 kg N/ha in above-ground tree components, which increased to 600 kg/ha in the unthinned stand by age 12. In contrast, the heavily thinned stand contained only 200 kg N/ha in the live trees at age 12, but 500 kg N/ha had been deposited on the forest floor in two thinning steps. Nitrogen concentration (dry weight basis) averaged 1.6% in 1-year-old leaves, with no trend evident with stand age or thinning treatment. However, in 2-year-old leaves nitrogen decreased from 1.5% at stand age 2 to around 1.1% at stand age 5 and thereafter increased to 1.5%, a pattern evident in older leaves as well. Nitrogen live branch wood and bark decreased from 0.3% and 1.1% respectively at age to 0.15% and 0.65% by age 6, but remained more or less constant thereafter. Nitrogen in stem wood and bark decreased asymptotically from 0.26% and 1.0% respectively at age 2 to 0.10% and 0.46% by age 12. Stem nitrogen concentrations were not affected by thinning. Calculations of the current uptake of nitrogen by the leaf mass took account of (i) the nitrogen requirement for leaf growth which peaked at 160 kg/ha/year at age 5-6), (ii) net nitrogen remobilisation from older leaves (which exported between 10% and 30% of their nitrogen, depending on current requirements for growth), and (iii) withdrawal of nitrogen from leaves immediately prior to abscission (estimated as 50% of the level in the retained cohort of leaves).

Initially the rate of nitrogen uptake above-ground increased with age from around 30 kg/ha/year at age 3 to 120 kg/ha/year at age 5. Thereafter, uptake decreased to around 90 kg/ha/year by age 12 regardless of thinning intensity, even though up to two-thirds of the stand basal area was removed at each thinning. On average 65%, 15%, and 20% of the above-ground nitrogen uptake was accounted for by leaf, branch, and stem components, respectively. With increasing stand age the percentage utilised in woody components increased slightly and leaf decreased slightly.

Soil and forest floor net nitrogen mineralisation, and inorganic nitrogen in precipitation, throughfall, soil leachate, and streamwater, were measured; estimates of apparent plant nitrogen uptake derived from these data were compared to biomass estimates of nitrogen uptake for four Pinus radiata D. Don stands - a high- and a low-stocking density on a very fertile former pasture site, and a high- and a low-nutrition treatment on a low-fertility coastal sand site. Net nitrogen mineralisation rates for the four sites were 126, 90, 9, and 2 kg/ha/yr respectively. The annual rate for the low-nutrition treatment at the coastal sand site was lower than any previously reported for forests. Apparent nitrogen uptake from the forest floor and soil did not agree with biomass uptake estimates except at the highly stocked former pasture site. Differences in stocking did not have a significant effect on nitrogen mineralisation. At the coastal sand site, nitrogen mineralisation rates were significantly greater in the high-nutrition plots than the low-nutrition plots but were much lower than the rate required for current tree growth for both treatments. There are various possible reasons for the low measured nitrogen mineralisation rate.

A 4-year sampling programme of lepidopterous defoliators in a young developing stand of Pinus radiata D. Don snowed that canopy density influenced the relative abundance of the two major defoliator groups, Pseudocoremia spp (Geometridae) and Tortricidae. Suction trap sampling showed that tortricid populations decreased as canopy closure led to reduced herbaceous growth, while Pseudocoremia spp. responded positively to increasing foliage density. Efforts to estimate the consumption of P. radiata foliage by measuring larval frassfall were frustrated by the high variability in rainfall leaching from frass traps.

Buried PVC cylinders were not effective in excluding tree roots from soil and litter in an unthinned Pinus radiata D. Don stand growing on pumice soil. Within 8 years roots had entered from a depth of 85 cm and were colonising the litter layer.

revious studies in a 12-year-old plantation of Pinus radiata D. Don characterised seasonal changes in standing crops of fine ( < l m m diam.) and small roots (1-2 mm diam.) in the thinned and control treatments. In the present study, standing crops of these roots were estimated from soil core samples for a second year to determine if the seasonal periodicity observed in the first year could be considered a general pattern. Results from Year 2 generally confirmed those from Year 1. With the exception of differences in late-winter/early-spring, standing crops of live fine roots indicated similar seasonal changes by treatment in the 2 years. Comparing the effect of treatment, we found no summer peak in the thinned treatment for either year. The over-all standing crop of live fine roots in the thinned treatment was 35% of the control. The seasonal periodicity of dead fine roots in the control was similar for both years, but in the thinned treatment, we found large differences by year. The over-all standing crop of dead fine roots was only 8% lower in the thinned treatment. Standing crops of small live roots did not change seasonally. The over-all standing crop of small live roots was lower in the thinned treatment but increased from Year 1 to Year 2. This increase may indicate an expansion of the networking system to which fine roots are attached. No similar expansion, however, was detected for fine roots in the thinned treatment.

Needle production, development, and abscission in Pinus radiata D. Don trees were examined on branches of different ages and orders over an 8-month growing season in two stands of different spacing (6700 and 760 stems/ha) and age (7 and 9 years) growing on a fertile site.

Trees of the more open stand consistently had three orders of branching and living branches up to 6 years old, while the close-spaced stand had only two orders of branching and living branches up to 4 years old. The main period of needle emergence was from August to November, although a few fascicles in the topmost crown level continued to emerge until March. Final needle length decreased with depth in the crown and generally with increasing branch order. Needle length of fascicles which emerged early in spring were in only a few cases significantly greater than those of summer-emerging needle fascicles. Generally needle elongation had ceased by mid-February while the main period of branch elongation was considerably less, i.e., from September to early November, and coincided with the period of needle emergence. The close-spaced trees showed net gains in numbers of fascicles in the first-order branches in the upper two crown levels at the end of the season. Trees of the medium-spaced

stand showed greatest net foliage gains in the second- and third-order branches and losses in the first-order branches; the upper two crown levels, however, could not be reached. Values for specific needle areas of the needles, measured in May only, ranged from 121 to 293 cm²/g and increased with crown depth and decreased with needle age.

Analyses suggest that, for all Pinus spp. where needle cross-section can be assumed to be a sector of a circle, the ratio 1/ pi should be used to convert from total to 'one-sided' surface area. The ratio pi should be used to convert from 'one-sided' to total surface area provided that needles have not been arranged in any preferred manner when measuring 'one-sided' surface area. It is emphasized that the method of measuring needle area, and whether values are of total or 'one-sided' surface area, should be clearly stated

Specific leaf area (SLA) was determined annually for three Pinus radiata D. Don stands at Puruki from ages 2 to 12 years old and undergoing periodic thinning. The canopy SLA averaged 160 cm²/g but decreased with stand age from 190 to 150cm²/g, while the SLA of individual leaf age-classes ranged between 100 and 220 cm²/g.

The most important cause of variation in canopy SLA, based on a theoretical analysis, was fascicle density. Density increased from 0.25 to 0.34 g/cm³ with stand age and by 7% as leaf age increased from 1 to 2 years old. Additional smaller sources of SLA variation were due to random fluctuations in fascicle average dimensions and a reduction in the number of needles per fascicle with increase in stand age. Most of the variation in canopy SLA was accounted for by stand age (74%) and leaf age (10%).

Assuming that there are no biases in the selection of bounded plots or trees to be biomassed, the error associated with estimates of stand biomass consists of the error associated with sampling trees for biomass and the error associated with the variability of stand characteristics between bounded plots. At Puruki, the error associated with sampling trees for biomass is generally the larger. Post-stratification of plots according to altitude had little effect on the percentage error associated with estimates of biomass per hectare, partly because poststratification reduces only one component of the error and partly because it was often reducing the smaller of the two errors. The percentage error associated with estimates of mean net stem weight increment depended on whether it is appropriate to combine data from both years in deriving a relationship between biomass and diameter over bark at breast height. Cost-effective schemes for sampling trees for biomass assume a linear relationship between a function of biomass and a function of diameter. The trees chosen are generally at the extreme ends of the diameter distribution. This means the assumption of linearity cannot be checked.

Pinus radiata D. Don dry matter and leaf area were measured at the Puruki site annually between ages 2 and 12 years in stands undergoing contrasting thinning. Current dry matter production and its partitioning to leaves, branches, and stems were estimated.

In an unthinned stand stocked at 2200 stems/ha, 230 t dry matter/ha accumulated by age 12 compared with 75 t/ha in a stand thinned to 160 stems/ha; however, the mean dbh in the unthinned stand was only 22 cm compared with 37 cm in the heavily thinned one. Basal area increment peaked at over 10 m²/ha/year at age 4 but decreased to 3-4 m²/ha/year by age 12, irrespective of thinning. Without thinning, basal area attained almost 60m²/ha by age 12, while the removal of 90% of the trees in two thinning steps reduced basal area by 70%. Leaf area (all surfaces) index peaked at 34 at age 6 but declined to 20 with increase in stand age. Above-ground production varied between 2 and 40 t/ha/ year depending on stand age and thinning treatment. Thinning prevented most branch and tree mortality evident in the unthinned stand.

Between ages 2 and 12 years, partitioning of annual above-ground dry matter production to leaves decreased from 40% to less than 20%, to stem increased from 35% to 60%, and to branches remained constant at around 23%. Thinning had little measurable effect on partitioning. Production above-ground increased, at a given leaf area index, with stand age. A shift in partitioning from roots to stem wood, rather than an increase in the efficiency of production per se, probably underlies this result. Tentative estimates of partitioning based on total current dry matter production were developed for P. radiata growing without moisture or nutrient limitations.

Seasonal variations of the non-structural carbohydrates, glucose, fructose, sucrose, cyclitols, and quinic and shikimic acids and starch were studied in buds, foliage of different ages and crown positions, stem wood and bark, and roots of Pinus radiata D. Don trees. The trees were either 12 years old from seed or rooted cuttings of two clones, growing in a fertile site at Rotorua. Of all the carbohydrates analysed, starch showed the most consistent patterns of accumulation and depletion, although the periods when starch concentration peaked differed with tissue type. In foliage, bark, and buds the proportion of carbohydrate present as starch was low, but in roots starch concentrations were similar to those of soluble carbohydrates. Soluble carbohydrates (glucose, fructose, sucrose, cyclitol, quinic and shikimic acids) were present in high concentrations throughout the year, although these also showed compositional changes with season and tissue type. Total non-structural carbohydrate contents were estimated to constitute some 2.8% of the total biomass of a tree.

Carbohydrate compositions and concentrations of the soluble fractions in foliage were found to be similar to published data for Pinus sylvestris L. and Pinus taeda L. However, starch contents differed by at least four-fold between P. sylvestris (24% of total dry weight) and P. radiata (6%); the lower starch levels in P. radiata foliage appear to result from its continuous growth habit in New Zealand.

A model for simulating canopy net photosynthesis in stands of Pinus radiata D. Don has been developed from measurements of rates of net photosynthesis on individual shoots and a radiative transfer model. It has been shown that estimates of net photosynthesis for a tree crown can be in error by up to 40% if the model assumptions do not agree with the method of measuring rates of net photosynthesis. Specific leaf area has been used to account for the variation in rates of net photosynthesis due to the physiological and morphological state of individual shoots throughout the canopy. Comparing estimates of canopy net photosynthesis for three different stands of Pinus radiata with above-ground dry matter production indicates that the model realistically estimates canopy net photosynthesis.

A model has been constructed for predicting the interception of solar radiant energy by an array of plants with ellipsoidal crowns. The applicability of the model to stands of Pinus radiata D. Don was investigated by comparing model predictions with measurements of instantaneous irradiance below tree crowns in a 9-year-old stand. The agreement between actual and predicted transmittances was generally good. However, small errors in measuring crown shape and leaf area can cause large variations in predicted instantaneous transmittances. When predicting the interception of solar radiant energy on a daily basis, small errors in measuring crown shape or leaf area did not cause large variations in intercepted radiant energy.

Model simulations indicated that there is a linear relationship between intercepted photosynthetically active radiant energy (PAR) and above-ground dry matter production in stands of P. radiata growing on a fertile site. This relationship was unaffected by thinning and light pruning. Assuming that the relationship is unaffected by more extreme thinnings and primings, simulations indicated that unthinned-pruned stands can intercept up to 25% more PAR than unpruned-thinned stands with the same leaf area index.

Nitrogen and phosphorus data were obtained monthly for 14 years for streams draining three adjacent catchments of different land use. Comparisons of concentrations between catchments showed a land-use effect for total phosphorus and dissolved reactive phosphorus in the order pasture > pine > native but this order was reversed for nitrate. No effect of land use was detected for ammonium. The catchment converted from pasture to pine near the start of the study period began to show consistent streamwater chemistry differences relative to the pasture catchment after 4 to 5 years of tree growth. The results of trend testing were difficult to interpret solely in terms of changes in land use because significant trends were found to occur in data collected from catchments with stable land use.

We conclude that long-term monitoring alone is of limited value in understanding the influence of land use on water quality and that research efforts are better directed when complementary studies on catchment processes are also conducted.

The hydrology and sediment regime of a 0.10-km² pasture, 0.34-km² pine forest, and 0.28-km² native forest catchment were compared. The highly permeable pumice soils of these catchments resulted in generally low annual stormflow yields (0.54-5.2% of gross rainfall) and consequently low annual sediment yields (4.0-27.0 t/km²/yr). The pasture catchment had the highest average flows, highest peak flow rates, and greatest stormflow yields, but lowest evaporative losses. The pasture catchment also recorded the maximum instantaneous sediment ccncentrations and the maximum instantaneous sediment discharges. The pine forest catchment had the lowest annual average flows, lowest low flows, and lowest instantaneous sediment concentrations and discharges, but evaporative losses were similar to those from the native forest catchment. The native forest catchment had the lowest stormflow yields, lowest peak flows, and highest low flows. Some of the differences in hydrologic responses from the native forest catchment could be explained by drainage density rather than land use.

Multidisciplinary research has been undertaken at the Purukohukohu experimental basin, particularly in the Puruki catchment over the past 15 years. This period covers the conversion of Puruki from pasture to Pinus radiata D. Don, the development of the trees to canopy closure, and the effects of differential intensities of thinning on growth to the middle of the rotation. Results of investigations into tree growth, nutrient cycling, and catchment hydrology are presented in papers collected in this issue of the Journal. This paper backgrounds the site, climate, history, and management of the catchment, and the development of the trees.

Puruki is a 35-ha catchment located at the southern end of the Paeroa Range in the central North Island of New Zealand, at an elevation of 600 m. The rhyolitic pumice soil, previously under rye grass/clover pasture and regularly treated with fertiliser, provides ample moisture and nutrients for P. radiata growth under the climatic conditions: 1500 mm of evenly distributed rainfall annually, 5 GJ/m² of solar irradiance annually, and average monthly temperatures of between 5° and 15°C. Puruki was uniformly planted with P. radiata at 2200 stems/ha in 1973 and trees in the individual subcatchments (Tahi, Rua, and Toru) were progressively pruned to 2.2 m height and thinned to 160, 550, and 290 stems/ha respectively by 1985, with further thinning intended. A part of Rua was left unthinned as a control. In closed canopy stands periodic volume increment attains 52 m³/ha/year. The removal of between half and three-quarters of the tree basal area every 3 to 4 years reduced volume increment to between 25 and 30 m³/ha/year, but this is likely to increase when management thinning is completed and the stand leaf area can increase uninterrupted to unthinned levels.

The interrelationships between aspects of the research work covered in the accompanying papers are illustrated using a conceptual modelling framework. The data collected at Puruki have proved valuable for testing theoretically based models and calibrating empirical models of P. radiata growth under conditions of ample moisture and nutrient supply.

Review of "Compression wood in gymnosperms" by T.E. Timell.

Pinus radiata D. Don trees exhibiting stunted growth and a terminal rosette of buds had foliar zinc concentrations less than 10 ppm. Corrective fertiliser application of 25 g zinc sulphate per tree (5.6 g Zn/tree) re-established tree vigour and improved foliar zinc concentrations to above 10 ppm.

The extracts obtained by this method of extraction of protein from mature tissues of some Pinus species are suitable for analysis of protein by electrophoresis and isoelectric focusing, isozyme analysis, and serological techniques. The relative freedom from interfering substances makes the method suitable for taxonomic studies.

Tree volume and compatible taper equations have been developed for plantation Eucalyptus regnans F. Muell. growing in a central North Island forest. Previously published non-linear and polynomial forms of compatible taper equations were estimated but found to be inadequate for describing the shape of the whole stem. An extension of the non-linear form was developed, which characterised the neiloid, paraboloid, and conoid sections of the stem satisfactorily and for which the standard error of estimate of bole diameter is ± 13 mm. This development, it is claimed, goes some way to resolving the conflict between equation compatibility and prediction bias.

The level of infection by Armillaria spp. in a 19-year-old, wide-spaced Pinus radiata D. Don stand was re-assessed after 9 years. Although the over-all infection level had changed little, the individual trees infected at the end of the period were not necessarily the same ones which had been infected at the start. Thirty-one percent of the trees infected at the start were uninfected at the end of the 9-year period. Sectional measurements showed that growth trends reflected changes in infection by Armillaria spp. Volume loss due to lethal infections was predicted to be between 26 and 61 m³/ha on a 28-year rotation. Over the same period of time the loss of potential volume attributable to sublethal infections was estimated at 5.5 to 11 m³/ha.

The distribution of rhizomorphs of species of Armillaria was determined in indigenous forests at three sites up to 80 km apart in the Rotorua-Bay of Plenty district, New Zealand, by systematically taking cylindrical soil core samples 16 cm diameter by 22 cm deep. There was significant between-site variation in the frequency of occurrence of rhizomorphs (4-19%; p <G.05). At one site with four plots (36 x 28-36 m; up to 1.4 km apart), there was between-plot variation in rhizomorph frequency (13-31%; p < 0.01), mean rhizomorph length per unit area of soil surface (2-9 m/m² ; p <0.01), and yield of isolates from samples containing rhizomorphs (41-89%; p <0.01). Distribution of viable rhizomorphs was clustered in two plots (p <0.05). Cultural techniques were used to identify species and intercompatibility groups among isolates made from rhizomorphs and basidiomata. Plots contained 19-93 groups of A. novae-zelandiae (Stevenson) Herink per hectare and 15-58 groups of A. limonea (Stevenson) Boesewinkel per hectare. Dimensions of intercompatibility group clusters varied from less than 4 m to at least 30 m across. Five out of eight billets of Beilschmiedia tawa (A. Cunn.) Kirk and Pinus radiata D. Don, protected from soil rhizomorphs by plastic shields, were each colonised by Armillaria species 20-22 months after being partially buried 1-5 m from a dense cluster of sporulating basidiomata of A. novae-zelandiae. This result, together with the high numbers of intercompatibility group density, suggests that basidiospores may play an important role in the establishment of infection centres in New Zealand forests.

Mycorrhizal fungi of Pinus radiata D. Don were studied on agroforestry sites in the central North Island of New Zealand. Rhizopogon rubescens Tul., the most common myeorrhizal fungus of P. radiata in conventionally grown forests, was replaced by two less-common mycorrhizal fungi - Tuber sp. and Scleroderma spp. The soil fertility of the agroforestry sites is high, especially in phosphorus, and this may be the major factor affecting the change of the mycorrhizal fungal species.

The hypothesis was tested that the stem volume increment in the first year after fertiliser application in a series of Pinus radiata D. Don fertiliser trials would be proportional to the needle mass, and the amount of nitrogen and phosphorus in foliage, soil, and applied fertiliser. Soil nitrogen and phosphorus contributed little to the relationship and the model could be simplified to:

∆ Volume (m³/ha/yr) = -0.115 + 0.269 kg N in the needle mass.

This simple relationship was then tested on a range of independent data and found to predict accurately. It can be used in simple physiological growth models and when reversed may be used to estimate the efficiency of fertiliser uptake.

The rationale behind foliar urea spraying of Pinus radiata D. Don seedlings after conditioning was investigated. Field application of urea (5% w/v) from the boom sprayer with and without surfactant resulted in inconsistent amounts of spray retained by the shoot, and surfactant additives gave no advantage. An increase in nitrogen subsequently resulted from recovery of spray runoff by roots.

Dipping individual needles into Tween 80, Silwet L-77, and Citowett enhanced retention 1.8, 1.8, and 1.5 times, respectively, over that in the absence of surfactant. Foliar urea uptake was 13-26 times faster than nitrate-nitrogen uptake and 3.5-7.5 times faster than ammonium-nitrogen. Absorption of ureanitrogen within 6 hours was 100% while ammonium and nitrate uptake was 40% and 55% complete, respectively. These results led to exclusive use of urea with surfactant in subsequent nitrogen applications.

Effective interception and retention of spray on needles in the field was dependent on a suitable application technique. Nursery seedlings absorbed 1.3 times and almost twice as much urea in the presence of Tween 80 and Silwet L-77, respectively, when aerosol and atomiser applications were used.

In glasshouse experiments two spray applications of urea 1% (w/v) containing 0.5% (v/v) Tween 20 raised the level of nitrogen in needles of wrenched seedlings from 0.9% to 1.6% N. It was predicted that a single, finely dispersed spray of 2% (w/v) urea could produce a similar increase in nitrogen concentration. The absorbed foliarly applied ¹⁵N urea 2% (w/v), 0.287 atoms % excess, contributed 12.5% of the nitrogen absorbed for production of new roots. Thus, foliar urea applications could be significant in root growth of conditioned seedlings.

In Pureora and Whirinaki Forest Parks 30-40% of total merchantable timber volume was harvested in 1961 from two unreplicated 15-ha blocks of podocarp/tawa forest; a further block remained unlogged as a control. In 19 years after logging at Pureora, the actual number of merchantable trees lost in the two logged blocks was considerably lower than in the control, although the rate of residual tree loss was similar. This suggests that logging has, in part, anticipated natural mortality and has not adversely affected stability. In 22 years after logging at Whirinaki, mortality of merchantable trees occurred at similar rates in all blocks, suggesting that logging has not adversely affected stability there either.

Logging appears to have had little impact on regeneration of canopy species. Naturally regenerated Beilschmiedia tawa (A. Cunn.) Kirk (tawa) seedlings are widespread in both localities, and podocarp seedlings are widespread at Pureora but scarce at Whirinaki where podocarp population structures in virgin forest are not stable.

At Pureora, gross volume increment in merchantable trees, mostly podocarps, was higher in the unlogged control and in one logged block than the other (0.5-0.6 cf. 0.3 m³/ha/annum). Net decrement occurred in all blocks, but was much higher in the control than either logged block. Total net decrement (i.e., including non-merchantable trees) is likely to be considerably higher. Growth plots in logged and virgin forest at Pureora indicate a likely average recovery period, for 80% of equilibrium basal area, of nearly 100 years for selectively logged forest.

Untended, fully stocked, even-aged stands of Nothofagus truncata (Col.) Ckn. (hard beech) or N. fusca (Hook, f.) Oerst. (red beech) of natural and cultural origin and ranging in age from 20 to 100 years, were sampled using temporary and permanent plots on a range of sites in North Westland, South Island, New Zealand. Changes in stand parameters with age were quantified in order to assess growth of these stands, and thus gain some insight into their silvicultural potential.

Stands of each species followed a similar pattern of growth, with rapid early height and basal area increment. Mean top height reached a maximum of c. 27 m by age 100 years. Basal area reached an equilibrium of c. 41 m²/ha in N. truncata and 46 m²/ha in N. fusca as early as age 30 years. Nothofagus truncata stands had, on average, a somewhat lower mean diameter at any given age than N. fusca stands, and maintained higher stockings. Both species attained similar maximum volume of c. 460 m³/ha at age 100 years.

Growth and survival of Agathis australis planted within a young Pinus elliottii stand on an exposed site on the Coromandel Peninsula were significantly better than that of kauri planted within adjacent low (1m high) and tall (3-4m high) scrub, but on a sheltered site no significant improvement occurred. Fertilizer application to kauri at planting within pines was not worthwhile but in tall scrub was beneficial. Pines thus not only provide shelter but may also induce beneficial soil changes.