CENTRAL AMERICAN PINE RESEARCH PROJECT

Commonwealth Forestry Institute, Oxford

R.H. Kemp

INTRODUCTION

The Central American Pine Research Project is financed by a grant from FAO and by the United Kingdom through a grant to the Commonwealth Forestry Institute at Oxford. Senior Research Officer for the project is R.H. Kemp. The project was due to end in April 1972 thus covering a 3-year period (1.10.69 – 31.3.72), but because of satisfactory results to date the project has been extended two years beyond the scheduled expiry date. This report covers four field trips made by Kemp up to 30th July 1971.

OBJECTIVES

1. Reconnaissaince, data collection and seed collection by provenances of Pinus oocarpa and Pinus caribaea in Central America.

2. Reconnaissance, data collection and seed collection by provenances of selected second priority species, particularly Pinus pseudostrobus (including Pinus tenuifolia) and P. strobus var. chiapensis.

3. Selection and recording of superior phenotypes of the above species, accompanied when possible and desirable by collection of seed or grafting material.

4. Establishment of “conservation stands” and “selection stands” on a variety of sites from seed of the more important coastal areas.

5. Discussions with the forestry authorities and associated authorities and institutions in all the countries visited (Nicaragua, Honduras, Guatemala, British Honduras and Mexico) about the conservation and proper management of existing forest resources and reforestation problems.

FINANCE

The total funds allocated for the project were $ 65 700.

During the first 12 months of operation total expenditure was kept about $ 2 400 below the estimated costs. In 1971 the simultaneous operation of collection teams in both coastal and inland areas proved very expensive, and the expenditure on field operations was greater than the estimate for the period. This was mainly due to the heavy transport costs for the collection teams and to the very high cost of seed collection of Pinus oocarpa in British Honduras, amounting to almost $ 500 for half a kilogram of seed. With the ending of the phase of range-wide itinerant operations the costs will be reduced in the next field period.

STAFF

During the first year the Senior Research Officer worked alone, assisted by a locally-recruited Honduran of forest-guard grade. In August 1970, after completion of reconnaissance and the first phase of seed collection for both first-priority species, two university graduates in forestry and biology were recruited under the United Kingdom Voluntary Service Overseas Programme, to act as leaders for extra collection teams for the remainder of the project.

Both volunteers chose to end their 12 months period of service in July 1971. This coincided with the ending of the phase of range-wide itinerant collection for the trials programme of the two principal pine species. The phase of extensive, simultaneous collections will now be succeeded by one more intensive, directed to obtaining the larger population seed samples for conservation or selection stands, and seed and scion material from superior pheno types in the selected areas. One or two of the climbers may be re-engaged for the next field trip. It is hoped that the Honduran team leader, who has gained a good understanding of the principles and methods of pine provenance seed collection may also be of continued help to the project in the bulk collection of seed in Honduras and possibly in Nicaragua.

EQUIPMENT

A Land Rover and two Datsun pick-up trucks of 1 ton capacity were bought. Three sets of tree bicycle equipment and other apparatus for tree climbing, seed collection and survey were purchased, as well as an altimeter and a portable cassette tape recorder. The U.K. Forestry Commission Research Station has agreed to make an annual contribution towards the increasing costs of seed storage and handling at the Commission seed store.

LOCAL OPERATING CONDITIONS

Information on the location and extent of the areas of pine forest has generally been available and reliable. There are very good topographic maps for most areas concerned in Guatemala and Nicaragua. Information on distribution of individual pine species is less complete and very little is known locally about the phenology of flowering, fruiting, cone maturation, growth rates, wood qualities and variability within species. Such information is being collected where possible. Travelling conditions are generally good enough to permit a representative sampling of the main areas of pine forest following a general zonation by latitude, topography and climate. The most inaccessible areas visited were some of the coastal lowland occurrences of Pinus caribaea in Nicaragua and Honduras, where it was necessary to use a combination of air travel, motor launch, canoe and foot trek. Such expeditions are not only very expensive of time and funds, but present problems in cone handling and seed-extraction, compounded by the wet season climate in those generally high-rainfall areas.

Seed extraction was achieved by sun-drying cones, but increasing use was made of the facilities at the Escuela Agricola Panamericana in Honduras for cleaning and storing seed. Further generous help was received from this institution in the determination of soil pH and of botanical material, as well as in raising pine rootstocks for later grafting. Good relations have been maintained with Government forestry services, who have sought advice on various subjects, and with FAO projects and country representatives.

WORK DONE

PINUS CARIBAEA

General. Reconnaissance and seed collection were directed mainly to the coastal lowland occurrences although several inland stands were also visited. In the more accessible areas both inland and on the coast the forests of this species have been extensively exploited during the past 20 years and very often almost all the remaining seed bearing trees are defective in form and vigour. Notable exceptions are the lightly-exploited areas in the less accessible parts of the Atlantic coast of Nicaragua and Honduras and the inland stands at Poptún in Guatemala. In many other areas 20 to 30 year old regeneration provides a source of seed in small quantities and the trees commonly are of much better quality than those of the older stands in the same localities. Despite the widespread occurrence of annual fires, which have locally eliminated pine regeneration in some places in recent years, the gene resources of this species in the area covered do not appear to be in immediate danger of depletion, except by slow overall negative selection. However, protection and conservation of individual trees or stands cannot at present be guaranteed and special concern may be felt for isolated stands at the extreme ends of the natural latitudinal range.

Many of the most accessible upland stands have been so heavily depleted by past expeditions and fires that no suitable collection areas could be found, although much time was spent on reconnaissance. The contrast in growing conditions between these and the coastal stands was very big. Particular interest is attached to the driest provenances.

The southernmost stands found in the vicinity of Laguna El Pinar, Nicaragua (12°13'N, 83°42'W), were small and scattered among swamps and broadleaved forests. In addition regeneration was very severely affected by fire. Selective exploitation of some of these stands occurs intermittently in the dry season and in view of their small size the progressive elimination of the best phenotypes and eventual disappearance of some stands seems very probable. At the other end of the range, in the isolated occurrence of the species at Poptún in Guatemala (16°20'N, 89°25'W), the gene pool is not in immediate danger and elements from it are already established in several other countries. However, the damage caused to individual trees by the commercial seed collectors is already severe and it will undoubtedly increase; thus productivity of this important seed source is being progressively reduced.

Distribution and variation

At present all P. caribaea in Central America is assumed to belong to the taxonomic variety hondurensis. However, the species is found in a wide range of ecological conditions from the seasonally swampy coastal sites with up to 4 000 mm annual rainfall and no prolonged dry period, to well drained hill slopes up to an elevation of 800 m, in rainfall areas of only 900 mm and with a marked dry season. In all areas visited there was apparent variation between individuals in such characters as branch thickness and angle, stem taper, “foxtail” development, etc.

Flowering and seeding

Flowering appears to occur mainly in late November or early December. On arrival in Guatemala during the first week of December most male strobili were found to be already open and many were empty. Young receptive female cones were also found at that time and could on the Atlantic Coast of Nicaragua be seen on occasional young trees as late as mid-March. No male cones could be found on any trees in the area at that time. The cones reach maturity in Nicaragua in early May and collection there is possible through most of June, which also appears to be the main period for seed fall of this species in the rest of Central America. Green cones can still be found in July and even early August in the northern part of the range. It seems that the cones take about 16 months to mature after pollination. Both 1970 and 1971 were very poor seed years with sparse cone crops, and according to some reports 1969 was also a poor crop. In some areas, particularly in isolated coastal stands surrounded by broadleaf forests, large numbers of maturing cones had been destroyed by parrots.

Seed collected

In 1969, 1970 and the first few months of 1971 seed was collected from seven sites. The collection was made by climbing selected trees. In view of the generally sparse crop no attempt was made to limit collection to an equal quantity from each tree. The number of trees varied from 28 to over 100 in the largest collections and was generally 50 to 60. In view of the difficulties and uncertainties of repeating seed collections from the same stands in future years it is desirable to obtain sufficient seed not only for the first series of provenance trials but also for a second series and for the establishment of larger blocks of plantations. A total of 22.5 kg of seed was obtained, with an average of 40 000 to 50 000 viable seed per kilogram. However, some sites are still inadequately represented and reconnaissance of further areas for seed collection was undertaken in May–July 1971. Seed extraction was made difficult by prolonged cloudy and rainy periods. In view of the need to keep to a planned sampling programme an attempt was made to dry cones in a rice-drying silo. This proved effective within 36 hours and the same method was employed with great success on two more occasions. From April to July 1971 collections were made at 10 sites. Five of these represent the “upland form” of Pinus caribaea var. hondurensis as found in the Republic of Honduras and Nicaragua. In addition arrangements have been made to obtain similar quantities of seed from the collections being made under the direction of the forestry department of British Honduras on their upland sites. A scheduled second collection from the trees selected at Poptún in 1970 could not be made as the area had already been stripped by the intensified and uncontrolled commercial seed collections. It was estimated that between 500 and 600 collectors were actively competing for the crop, which was already heavily depleted by last year's crude harvesting methods. Recommendations for effective control of seed collection in these stands were made by Mr. Kemp and have now been accepted by the Government authorities. It is hoped that before next season it will be possible to institute both a course of instruction for a restricted number of licenced collectors and also proper supervision of their activities. In the coastal areas the effort to obtain more seed from the most tropical, isolated stands in Nicaragua first collected in 1970 was very disappointing despite a very great increase in time and funds expended on this. The quantity of seed obtained is, however, representative of a large number of trees and with the earlier collection the amount should be big enough to indicate any large and important population differences between these and the other Nicaraguan coastal stands. Repeat collections from the important areas of Brus Lagoon, Guanaja and Alamicamba were more productive and these are now held in sufficient quantity for immediate establishment of a few selection stands of each provenance.

The total number of coastal provenances of P. caribaea var. hondurensis available for the International Provenance Trial is 7, and 5 are available in sufficient quantity for inclusion in all planned trials. In addition it is hoped in the near future to obtain seed from the coastal plain of British Honduras. Together with seed already obtained from the Bahamas and Cuba this makes possible fully-representative range-wide provenance tests of the species on a wide range of sites.

PINUS OOCARPA

General. A reconnaissance of P. oocarpa forests was carried out during the first field tour. In order to see representative samples of the range in the limited time available it was decided to follow a general zonation by latitude and topography, with particular attention to lower altitudes and to areas isolated by topographic barriers. Climatic information is generally incomplete but the species occur mainly in areas with an annual rainfall of 2 000 mm or less, generally between 300 and 2 000 meters' elevation, frequently on shallow, stony, seasonally dry acidic soils, often on very steep slopes. Particular interest is attached to the scattered stands on the hills above the plain of Sébaco in Nicaragua near the southernmost limit of the natural range of the species. The mean annual rainfall is only 920 mm with 4 months of 25 mm or less of precipitation. Absolute maximum temperatures of over 40°C may be recorded during these dry periods. The species grows in very dry conditions in parts of Honduras and Guatemala but it is also found on well-drained slopes in more humid zones with a total annual rainfall approaching 3 000 mm and with no clearly-marked dry season. Its distribution seems thus to be determined mainly by human activity, particularly clearing and burning. The resistance of young seedlings and saplings to fire is very strong, as the plants are able to produce new shoots from low down on the stem even after all the growing points and the majority of the main stem and branches have been killed. This ability to sprout from the base was seen on young trees with a diameter of up to 10 cm at the base. Also very young seedlings of Pinus oocarpa, apparently only a few weeks old, were seen surviving fully exposed in very dry sandy soil during prolonged periods without rain.

Distribution and variation.

Whereas P. caribaea is found mainly on the lower slopes and valley floors, the main occurrence of P. oocarpa is between 600 and 1 300 meters, generally in steeper and less accessible terrain. For this reason the forests have suffered less severely in the past from exploitation, and very impressive stands are still to be found from the northern border of Nicaragua to Baja Verapaz in Guatemala. The main extent of the species is in Honduras, where it covers an area of more than 160 km from north to south and 300 km from east to west. Large areas throughout Honduras suffered severely from the Dendroctonus epidemic in 1964, but although this very severely reduced the standing volume and growing stock it has probably not had any unfavourable effect on the gene resources. Except when there have been frequent severe fires, particularly near population centers, regeneration has been excellent. Exploitation, often succeeded or accompanied by fire, is however being greatly intensified in many areas. Apart from the general negative selection this is threatening to destroy some isolated stands, particularly near the southern extreme of the natural range. These stands have already suffered greatly and the remaining trees are unimpressive, although there is evidence that much larger trees capable of quite rapid growth existed there in the past. In view of the severely dry conditions and poor soil it seems probable that these populations contain genetic material of great value for other dry areas of the tropics. There is undoubtedly a wide range of variation in morphological features such as size and shape of cones, the development of spines and protuberance of the apophysis (this last feature was found to vary greatly, sometimes even on the same tree). In addition to the usual voucher herbarium specimens for each provenance collection, much additional material was collected throughout the range of the species in Central America and brought to Oxford for later study.

Flowering and seeding

Flowering appears to occur mainly in mid-January. Near Guatemala City some male strobili were observed to be opening during the second week of December, elsewhere production of pollen from a few trees was seen occasionally as late as the end of February. The production of female cones seems to occur over a long period of time although the main appearance of receptive conelets is mid-January. Some mature cones were found in December but the main period for collection seems to be mid-January to early March. Some fully developed green cones could still be found in March in some areas and cones apparently nearing maturity were found even in August. Collection of some seed seems to be possible almost throughout the year; this is at least partly due to the hard, woody cone scales which are slow to open, and to the persistence of cones on the tree. Nevertheless the phenology of flowering and fruiting of this species in Central America requires further study. 1970 was generally a poor crop year, but it appears likely that 1971 will be better at least in some areas.

Seed collected

In 1971 24 seedlots of P. oocarpa from the C.F.I. collections were available in sufficient quantity for inclusion in the International Provenance Trial. In addition seed was collected from a number of individual trees for taxonomic and genetic studies. A total of approximately 32 kg of cleaned seed was obtained.

Allocations of seed for the International Provenance Trial of this species were made and it was expected that most seed would be distributed by October 1971. A reserve is kept aside from the trial for later establishment of selection and conservation stands.

OTHER SPECIES

Pinus pseudostrobus was seen in all three countries visited, usually at elevations above 1 200 m (850 m in Honduras). The species seems to extend southwards in Nicaragua almost as far as P. oocarpa. Best growth seemed to occur above 1 400 m and some very large trees of excellent form were seen at an altitude of about 1 500 m in both Honduras and Guatemala, including some which measured 40 to 50 m in total height and had a diameter (d.b.h.) of 60 to 90 cm. The timber is generally whiter and softer than that of P. caribaea and P. oocarpa. P. pseudostrobus is capable of very fast growth, the trees can reach a height of 30 m and d.b.h. of 40cm in about 20 years. The species is reported to be more susceptible to fungus diseases than other Guatemalan pine species. In many areas the male cones were approaching maturity in early March and some young female conelets were emerging at that time too. Mature cones could first be seen in Guatemala in late February although the majority of the cones were still soft and green. In Honduras the main crop is said to ripen in May or later. Collection of seed was started in 1971 from widely-separated centres.

Pinus tenuifolia, usually treated as a variety of P. pseudostrobus, was seen in several localities in Guatemala. The most extensive stands were the ones found in the vicinity of Coban, Alta Verapaz, where the mean annual rainfall is about 2 400 mm and where there is no clearly marked dry season. Growth in these conditions appears to be very fast and several logs of 50–60 cm in diameter had growth rings averaging one centimetre throughout their life. One area of natural growth reported to be ten years old contained trees of 30 m in total height and 30 cm d.b.h.

Observations were also made on some valuable broadleaved species. Species of Meliaceae and Juglans were studied in all three countries visited. From the apparent rates of growth and reported timber quality if appears that some Central American Juglans species deserve further study as possible alternatives for the lowland tropics. Small trials of Juglans have been established by FAO staff at Turrialba in Costa Rica.

A small quantity of seed of Swietenia macrophylla was also collected in 1971.

FUTURE PROGRAMME

As mentioned above, the project has been extended for a further two years beyond the original expiry date in April 1972. *)

Cooperation with the Forest Research Service in Australia (Queensland) in the collection of seed, particularly of Pinus caribaea in Central America, is under discussion and it is possible that this may take the form of a contribution of funds to expand the work programme. These funds would be used strictly to undertake collection work which is not at present provided for in the revised estimates of monthly expenditure on the project.

Beyond the primary objectives and certainly beyond the present scope in time and finance of the existing research project lies the equally important need for evaluation of the collections in well-distributed and well-conducted trials, and the securing of future supplies of selected and improved material. The extension of the project would permit collection of seed for conservation and selection stands of selected provenances of Pinus caribaea and P. oocarpa, and stage-one provenance collection of Pinus pseudostrobus, P. tenuifolia, and P. montezumae.

One further field expedition is planned before the expiry of the present project period. This expedition is expected to last from the 3rd of January 1972 to mid-May. The principal objectives will be to obtain collections of P. oocarpa from the range in Mexico excluded from the project activities to date, to obtain more seed of selected provenances of P. oocarpa in Guatemala, Honduras and Nicaragua for selection and conservation stands, and to obtain some stage-one provenance seed collections of P. pseudostrobus and P. tenuifolia. Seed collection of P. oocarpa in Mexico is dependent on co-operation with the Instituto Nacional de Investigaciones Forestales. Mr. Kemp paid a brief visit to INIF at the end of July 1971, and discussions were held with the Director, the officer in charge of tree improvement and the taxonomist of this institute. There appears to be every prospect of close and fruitful collaboration with the INIF in the proposed seed collection f P. oocarpa and in the associated collections of herbarium material and data on the species. Mr. Kemp revisited INIF in early 1972.

There are some possibilities for obtaining seed of Pinus strobus var. chiapensis in Guatemala. The cones mature in May, but as attention was concentrated on collection of P. caribaea in May 1971, the collection of P. strobus var. chiapensis was postponed until 1972.

With the suspension of field operations from August to December 1971 the envisaged collection of seed of Juglans sp. could not be made this year, but will be undertaken in the Project Extension. Rootstocks of both Pinus caribaea and P. oocarpa are being raised in Honduras in case they are needed to form a gene bank of individuals that appear to be of exceptional interest and in some danger of being lost. Whenever seed collection is possible from such trees it will be preferred to collecting grafting material. The number of clones collected and the extent to which they might be used in clone collections or possibly seed orchards will depend on what financial provision may be made for their establishment and maintenance.

*) The extension grant will cover further collections of seed for research from Central American pines, and for a few hardwoods (Cedrela, Cordia and Juglans), the collection of wood samples representative of the variation within pine provenances and the collection and examination at The Tropical Products' Institute, London, of resin samples obtained throughout the range of these pines.

C.F.I. COLLECTIONS
List of seed obtained January to July 1970

Method of Collection:    A - directly, by climbing selected trees.
B - directly, from selected trees in felling areas.
C1 - indirectly, by another collector from felled trees in selected and approved stands under exploitation.
C2 - indirectly, by gift or purchase from areas not inspected.

C.F.I. COLLECTIONS

List of seed obtained October 1970 to July 1971 - (Information in brackets is approximate)

COUNTRIES PARTICIPATING IN C.F.I. INTERNATIONAL PINE PROVENANCE TRIALS AS AT THE BEGINNING OF 1972

¹ For arboretum