A positive correlation exists between Pisonia height and 

 island width (Fig. 32). On Caroline, motus were 90 m wide 

 before closed canopies of 13 m developed (Fig. 32), and tree 

 height increased to 21 m with islet width up to 200 m (Pig, 

 topmost star in Fig. 32 ). Further increases in islet width did not 

 result in taller trees. However, even on motus with sufficient 

 w idth, Pisonia did not develop unless other environmental 

 conditions were suitable. For example, on Long, Pisonia only 

 occurred in the centers of its former islets, not in the scrubby 

 areas where coalescence is more recent. Tridacna. seemingly 

 excellent for Pisonia, has not yet recovered from its Cocos 

 plantations. 



Pisonia-Seabud Relationships : Seabirds are an integral 

 part of Pisonia ecology. Its sticky seed capsules adhere to the 

 feathers of, and are thus dispersed by, seabirds such as terns, 

 boobies, and frigatebirds; thus, its early appearance on small 

 motus is not surprising. 



On Caroline, six species of seabirds nest in its branches, 

 dropping considerable guano to the ground below. Black 

 noddies, amassing in dense colonies, nest almost exclusively in 

 Pisonia, along with brown noddies, white terns, great and 

 lesser frigatebirds, and red-footed boobies. Pig Islet, with 

 7.25 ha of excellent Pisonia forest, supported a dense colony of 

 nearly 2,000 pairs of black noddies (Subchapter 1.2. this 

 volume). Bristle-thighed curlews feed on the ground beneath 

 its open understory. and the long-tailed cuckoo forages within 

 ils canopy. 



Seabirds may be so much a part of Pisonia ecology that a 

 debate exists as to whether Pisonia actually requires guano for 

 successful germination and establishment of seedlings (Shaw, 

 1952; Fosberg. 1953;Wiens. 1962). Very high phosphate and 

 nitrogen levels arc associated with mature Pisonia, and 

 concurrently the development of Pisonia forest results in 

 great!) modified soils that perpetuate its existence (Wiens, 

 1962; Spicer & Newbery. 1979). The formation of a highly 

 acid raw humus on the surface of the ground, sometimes in 

 association with phosphatic hardpan. has also been documented 

 on several atolls by Fosberg ( 1953. 1956). including Vostok 

 (AKK and John Phillips, personal observation). Perhaps 

 Pisonia's present distribution, primarily restricted to uninhabited 

 islands ( Shaw, 1 952; Wiens. 1 962 l.isin part due to the fact that 

 its primary seed carriers, seabirds. rarely coexist for long with 

 num. 



Remnant Pisonia Forests in the Pacific : Though naturally 

 and widely distributed from the western Indian Ocean to the 

 eastern Pacific (excluding Hawaii), Pisonia grandis has become 

 increasingly rare this century (Fosberg. 1953 and personal 

 i ommunication). Occupying the interior of most atolls, it may 

 have formerly covered the greatest area of any tree species in 

 the Pacific (Wiens, 1962). Shaw (1952), summarizing its 

 distribution, stated that it only occurs on remote, generally 

 uninhabited islands ranging from the western Indian Ocean to 

 the eastern Pacific, including Malaysia. However, more recent 

 studies, particularly bv Fosberg, indicate that because its habitat 

 occupies, and is in part responsible for. the most fertile areas of 

 inhabited islands, its formerly extensive forests have been 

 largely replaced by coconuts. Though Pisonia's soli wood is 



of little use to either atoll inhabitants or to the timber industry, 

 its soils were rich sources of phosphate fertilizer and w ere thus 

 greatly disturbed during the guano mining era. 



One of the most extensive Pisonia stands in the Pacific 

 ( 1 3.5 ha on Vostok) was partly burned in 1977 by members of 

 a "scientific expedition" (Fosberg. 1977b). The Royal New 

 Zealand Air Force found it smoldering 3 months later (Fosberg, 

 1977b, personal communication). In a March 1990 visit to 

 Vostok, we found that approximately 1.5 ha were completely 

 cleared ( Kepler. 1 990c ), and a further unknown amount of land 

 was affected. Other excellent groves exist on Palmyra and 

 Washington (northern Line Group land on Nikumarorol Phoenix 

 Group). Flint (Southern Line Group); Christmas (northern 

 Line Group); Bikar, Jemo, and Ujae (Marshall Islands): and 

 Aitutaki, Penrhyn. Suwarrow, and Manihiki (Cook Islands) 

 have relatively small stands. Caroline, with 62.73 ha in Pisonia 

 forest (36.94 ha in monotypic groves) holds some of the finest 

 representatives of this ecosystem in the Pacific, even though 

 much of it is not virgin. 



Coconut Woodlands (96.14 ha) (Figs. 14.36: Pis. 18.23.24. 

 28-30.33.34.37.39.40.44) 



General Distribution : Cocos. although present on 15 

 motus and known historically from another 4. covers significant 

 areas only on Caroline's 2 largest islets. South and Nake 

 (Table 13). Individual trees and small groves elsewhere are 

 drift-derived or remnants of plantings made from 1916-1 920. 



The following species occur in habitats containing Cocos 

 (Table 2): 



Trees: Pisonia grandis, Morinda citrifolia, Pandanus 

 tectorius, Cordia subcordata, Cocos nucifera, Thespesia 

 populnea, Hibiscus tiliaceus; 



Shrubs: Tournefortia argentea, Ximenia americana; and 

 Herbs: Boerhavia repens, Portulaca lutea, Laportea 

 ruderalis.Achyranthescanescens, Phymatosorusscolopendria, 

 Ipomoea macrantha, Lepturus repens, Taccaleontopetaloides, 

 Psilotum nudum, Phyllanthus amarus, and Sida fallax. 



The distribution of Cocos (Fig. 14). in order of decreasing 

 abundance is as follows: South: Forests old and neglected. 

 Healthiest palms line the lagoon, currently shading out strip of 

 native scrub. Nake: Southern forests (50-80% Cocos) healthier, 

 younger, with more native trees and Pandanus than on South: 

 grove of about 50 palms on northeast. Long: Range from < I ' i 

 cover (Tr. C) to dense fringe adjacent to lagoon. Emerald; 

 Northeast and center-west patches. Mannikiba: Main grove. 

 northeast: 40 palms. 20 m high, another patch in south centei 

 Ana- Ana: House site, northeast point. Bird. Blackfin, Brothers. 

 Nautonga. North Brothers. Pig. Pisonia. Raurau. Shark: lew 

 trees each, primarily in Tournefortia. Lone Palm: One tree, 

 central forests. 



History : A relatively small coconut grove was planted on 

 South Island prior to the 16th century by Tuamotuan settlers 

 (Emory, 1947; Maude, 1968). In 1 606. deQuiros noted -plenty 

 of palms" and "many cocoa-nuts" (Markham, 1904). Since 

 then, every visitor has recorded them as they grew, and still 

 grow . adjacent to the boat "landing." A smaller grove evidently 

 also existed in the south-southwest portion of South Island 



32 



