Abstract
The increased abundance of historically rare native tree species is symptomatic of land-use change, which causes ecosystem regime shifts. I tested for an association between mean agricultural area, a proxy for land-use change, and native tree species. I first modeled agricultural area during the years 1850 to 1997 and the historical and current percent composition of tree genera, along with the dissimilarity and difference between the historical and current composition, for the northern part of the eastern U.S. I then modeled agricultural area and current genera and species for the eastern U.S. and regionally. For the northeast, agricultural area was most associated (R2 of 78%) with the current percentage of elms and a diverse, uncommon “other” genera. For the eastern U.S., Ulmus, Juglans, Prunus, boxelder (Acer negundo), black cherry (Prunus serotina), and hackberry (Celtis occidentalis) best predicted agricultural area (R2 of 66%). Regionally, two elm and ash species, black walnut (Juglans nigra), mockernut hickory (Carya tomentosa), red maple (Acer rubrum), sweetgum (Liquidambar styraciflua), and American sycamore (Platanus occidentalis) increased with agricultural area. Increases in historically rare and diverse species associated with agricultural area represent an overall pattern of invasive native tree species that have replaced historical ecosystems after land-use change disrupted historical vegetation and disturbance regimes.
Highlights
Increased tree biodiversity due to land use may seem beneficial, but diversity gains typically occur through the introduction of non-native species or encroachment by native species that were historically rare, with co-occurring losses by historically abundant species and unique ecosystems
Open forests have a limited tree presence, but stand diversity occurs in the herbaceous plants and associated wildlife, which are declining in forests with increased tree diversity and density [1]
Regardless, native and introduced plant species have assembled into novel communities in response to the human activities of devegetation and agricultural use cycles, which are unfavorable to the regeneration of historical ecosystems in the eastern United States and globally [34]
Summary
Increased tree biodiversity due to land use may seem beneficial, but diversity gains typically occur through the introduction of non-native species or encroachment by native species that were historically rare, with co-occurring losses by historically abundant species and unique ecosystems. Grasslands are one ecosystem for which greater tree diversity and density are a problem for biodiversity Another example is open forests of savannas and woodlands, where an herbaceous layer coexists with overstory trees. Open forests of fire-tolerant oaks dominated the central region, with localized forests of shade-tolerant American beech (Fagus grandifolia, about 5% of all trees), sometimes in conjunction with eastern hemlock. Instead of using diversity indices, I first tested correspondence with the agricultural area of historical and current tree genera. Desirable outcome in regions where tree diversity increases in conjunction with agricultural use, which signifies a loss of historical ecosystems [9]. NTsowiseorleatceomth-e bsipneecdie.s most associated with agricultural area, I modeled current percentages of all but rare tree species of the eastern United States and regionally (Figure 1). ReTshueltsmagnitude of disturbance and forest change in landscape diversity was expdbreyepsaesnmTeddhaeejbnomytr baraegemveneciathrujsoadfrolerrfeoerosvftmedsritssfioatruledrf-ibrdvoaeemnprcseeefniaredenae-dsndttefeorpornaeenksbtdracoenhandadtnploegiaanekfeifnafonolrardeenssptdtsissncooeafrpfmdoeiradseptisuvlteserbr(osia.rienty.dc,eiwrs-etiadnusdrmbeexapapnpercnleeeds-;sieAnend-.t rbuebercuhmf)o,raesshtsetso, adnivdercsheeerraisetser(nFibgruoraed3le)a. fNfoorneestthseolfesms,apacleco(ir.de.i,nrgedtomtahpelere; gAr.ersusborrusm, n),eaisthheers, tahnedBcrahye–rrCieusrt(iFsidguisrseim3)i.laNriotynebtehtewleesesn, athcecohridstionrgictaoltahnedrceugrreresnsotrpse, rnceeinthtaegretshoefBeraacyh–gCeunrutiss ndoisrsitmheiladriiftfyerbeentcweebenettwheeehnistthoerichailsatonrdiccaul rarnendt cpuerrrceennttapgeerscoenf teaagceh goef neuaschnogretnhuesdiwffaesrsetnrocnegbleytrweleaetnedthtoe ahgisrticourilctualraalnadrecau. rLrieknetwpiseer,cdenotmagineaonfceeabcyhthgeenhuisstowriacsalsgtreonnegralywraeslanteodt itnoflaugernitciuallt.uIrnaslteaardea, .thLeikceuwrriesnet, dpeormceinnatangceesboyf tehlme hainstdortihcealugnecnoemramwonas“nootht eirn”flugeennetiraal. wInesrteeatdh,ethmeocduerlrevnatrpiaebrlceesntwagitehs tohfeelsmtroanngdetshteruelnactoiomnmshoipn “woitthhera”ggriecnueltruarwaleraeretha;etmheodRe2l vvaalruiaebwleassw7i8t%h t(hbeostthrorneggreesstsroerlas)tifoonrsthhipe wwiitthhhaeglrdicsualmtupralelsa.rTeah;ethRe2 wR2asva6l1u%e wanads 7688%% (wboitthh orneglyreosnsoerso)f ftohrethtwe owivtharhiealbdlessa,manpdles2.1T%heanRd2 w31a%s 6w1%ithanBdra6y8–%Cuwrtiitshdoinslsyimoinlaeroitfythaes ttwheo pvraerdiaicbtloers., and 21% and 31% with Bray–Curtis dissimilarity as the predictor
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