Differences in Amphibian Populations in Logged and Old Growth Redwood Forest

Surveys.of amphibians.were done on 8 plors 10.12t ha €ach), consisriog of a paired comparisons (Iogged and unlogged) in oi n€ar the Redwood National Park, California. ^ The numier and perceorage cover.of perennirl ve8erarion were grearer on old growrh plots thao on logged . ire. Amphibian p.)puldr ions had more indiv iduals and sreareb iom*s, , ani J i f ferent spc, i "d.omposirion on rhe old growth sires rhan on logged plots. Abundance of amphibians was lower io ihe reJwood loresrs rhar had been loggcd 6-14 _yejr-s rgo. This evidcnce suggesrs rhar lo8gjng hd. r rongterm errecr on residenr. herpf totaunal o i redqood toresrs. Apprrenr ly, opening of f ie ranopl ra\ors a rew spec,es to rhe cterr lmenr ot rhe mato1ry of fores(.dependenr spe! ies, Introduction Advertisements in natiooal magazines imply that productive, abundant wildlife populations iohabit logged lancls and that successional stages contain better habitat conditions for vrildlife rhao do marure ( somerimes termed decadent ) forests. These claims are simplistic because the cornplexity and variability of mature forest ecosl,stems or the imlnrtant roles of nongame wildlife are not considered in rhese systems. Hassinger et al, (1975) stated . har the net worth of a clearcut to vrildlife must be viewed as a balance of values, since processes detimenrai to one species may be beneficial to another. I-ogging creates vegetarional diversity (e.g., edges and openings) and thus is generally beneficial to game because it promotes increased growth of herbaceous and shrubby foods that maoy game species require ( Teague 1968, Noble 1974, Umber and Harris 1974, Costa et dl, 1976). Bur game may constiture only a small fraction of forest vrildlife, especially in mature sraods (Bnry et al, 1980'). Logging may drastically change or adverseiy affect the habitats of many animal species. Irr westero North America, for example, small mammal communities are altered by timber harvestiog. Deer mice (Petotnysczs manictlatus) generally increase in numbers after logging, rvhereas red-backed voles (Clethriononzyt californicut), red squirrels (Tamiasciurus huclso cus), and other forest-adapred species decrease (Gashn,iler 1970, I/olff and Zasada 1915, Hooven and Black 1976, Sullivan 1980). One study revealed that even big game (deer, elk, and moose) declined duriog the first 5 years after logging and that rhe carrying capacity of the forest when measured 17 years after logging nas lower than expected (Stelfox e, al. 1976). Several authors have suggested thar cleal logging ( removal or burning of downed q/ood and understory vegeration) teduces the abundance of small mammals (Lovejoy 1975, Martell and Radvanyi 1977, Haosson 1978) and game (Steifox et al. 1.97 6) by decreasing the supply of cover available ! o them. Recenr studies indicate that logging Northwest Science, Vol. 57, No. l, 1983 76j variously aff€cts different aoimal ta-\a and decreases many wildlife species (Umber and Hanis 1974, Glowacinski and Jiirvineo 1975, Shepard 1975, \Chite et al' 1975' Bunrell 1976. Anl6n 1976, Fwzeb 1977,Webb et al 1977, Kessle! 1979, Luman and Neitro 1980, Meslow e, al. 1981, Schoen et al. l98l) ' Because of diverse habitat conditioos and forest typesi the reslxrnse of wildlife to logging is difficult to predict. More comPreheosive data about the effect of timbc! harvestiog on specific types of forests and on the nongame aoimals in these ecosystems o,o,rld be useful io designing fotest managen.rent Practices favorable to wildlife Populations. This study is the firsc to examine the effect of clearcur logging oo the helPettlfauna of old growth redwood forests. Descriplion of study Areas Four study areas *,ere established in or adjacent to the Redwoods National Patk in north$/esterfl California: (1) Hilt Ptot and (2) Valley Ptot, both in North Fork draioage of Lost Man Cteek (Sec. 11, T.11N, R1E), 3.5 km E of Hwy 101 (from the Prairie Creek Fistr Hatchery), Humboldt County; (3) Bald Hil ls (Sec 1, T-10N, RlE),41 km E of Orick, along the Bald Hills road, Humboldt Couoty; and (4) Yurok Redwood Experimental Forest (Sec.21, T.14N, R1E), 1.3 km N of the Ranger Station, Del None Couotv. A1[ distances are direct line. Each study area coosisted of trvo sampling sites (oid growth aod clear-cut logged ) that had similar steePness ( Percert stope), slope ditection, and major vegetatinn types (Table 1). On the Hill and Vatley Ptots and BaLd Hills, the total number of live trees plus natural stumPs more than 1 m DBH (diameter at brea$ heiSht) wele comPamble io the number of stumps (cut trees) on the logged sire The Experimental Forest q'as more vaJiable. The okl growth site had more large trees (N-12) rh;rn rhe Logged site hacl large srumps (N : 5). But thes€ two aleas wele ooly 200 m aPart and seemetl to have similar plaot composition, aod the entire alea was once a conllguous staod of redwood. Old growth sites at Inst Mao Creek and the ExPerimeotal Forest were predominantly redwood (Sequoia JeTDperri,retut) with a ferv scattered Douglas tt (PJeudott ga 1]ten' zietiil and Sitka spruce (Picea sitchep.tit) Lost Man Creek was harvested 6-7 years before this study and had rro tlees lafger than 10 cm DBH on logged sites logging hcd occurred 15 years eadier io the Exprimental Forest (an area dominated by redwood)' ancl the site had regro*'n with a tangle of small red alder ( Alpu: oregatua) At Ba'Ld Hitls, both sites had otiginalty contained redwoods mixed $'ith a ferv tzrnbark oak (,Lithocarpt6 tlensiflou) aod $restern benlock (Tsuga heterophylla), aod many small Dougtas fir. Logging at the Bald Hills site had occrrred about 10 years before this scudy. Methods and Materials Each sampiing site measured 2) x 50 m (0.125 ha) Ail trees larger than 10 cm DBH v.ere iniividuallv measured. Oo 10 squares (1x 1m), atranged jo 10 domino configuration at each site, I recorded the number of pereonial plants present aod visually estimated the Percentage of sutface area that they coveted The oumbet and sizes o{ pieces of surface clebris (branches, downed small tiees, and logging litter) rhat coulJ be turned over were couored on all sites except the Hitl Plot. This characteristic repre-