Changes in forest structure and tree recruitment in Argentinean Chaco: Effects of fragment size and landscape forest cover.

TORRELLA, S. A.; GUIZBURG RG; ADÁMOLI, J. M.; GALETTO L

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 307 p. 147 - 154

0378-1127

Subtropical Argentinean Chaco forests have been severely deforested and fragmented due to agricultureduring the last six decades. The most affected forests are located in areas that are most favorable forcrops. This is the case of the semi-deciduous ??bosque de tres quebrachos?? (??three quebrachos forest??)in southwest of Chaco Province (Argentina), where this study was carried out. The aim of this workwas to analyze the fragmentation process, considering spatial (fragments and landscape levels) and temporal(land use changes) scales, studying the effects on the forest structure (density and basal area) andtree recruitment. All trees (adults and saplings) were recorded and measured in 112 plots (400 m2) distributedin 28 forest fragments (0.9?160 ha) located at four different landscape samples (4500 ha) in oneenvironmentally homogeneous zone (72,804 ha). The four landscape samples have different current forestcover (low/high) and different land use history (low/high). Using linear mixed models, we evaluatedthe effects of current and historic fragment size, landscape forest cover and land use changes on the densityand basal area at stand level, and considering the two different strata (upper and middle). Resultsshowed that fragmentation did not severely affect the structure of the older age classes of trees in theremaining fragments but affect the tree recruitment, which could influence over the ability of the forestto perpetuate itself. We found positive relationships between sapling density and fragment size for thetree species of middle stratum, and between sapling density and forest cover at landscape level for thespecies of upper stratum. Regarding adults, we found a negative relationship between density and historicfragment size, probably related to the past timber harvesting. We concluded that even small fragmentsof three quebrachos forest and those located in highly deforested landscapes have highconservation value since their structure does not differ from that of the larger fragments or landscapeswith higher forest cover. Our results reveal the importance of considering landscape and fragment scalessimultaneously to better understand the fragmentation process and improve the recommendations forthe management of fragmented landscapes.