Adjusting xylem anatomy and growth to inter-annual climate variability in two Fabaceae species (Centrolobium microchaete,Cenostigma pluviosum) from Bolivian dry tropical forests

Climate-growth relationships are strong in seasonally dry tropical forests (SDTFs). To better understand the ecological processes controlling these relationships we need to assess the long-term responses of wood anatomy and radial growth to year-to-year climate variability. We assessed how wood-anatomical traits (mean vessel area –MVA– and vessel density –VD–, percentage of conductive area –CA–, xylem-specific estimated hydraulic conductivity –Ks–) and growth responded to local climate (mean temperature, total precipitation, estimated moisture) variability and teleconnections (Pacific Decadal Oscillation) between 1970 and 2011 in two Fabaceae tree species (Centrolobium microchaete and Cenostigma pluviosum) coexisting in a Bolivian SDTF. We found that C. microchaete produced wider vessels and was more responsive to both local climate conditions and teleconnections than C. pluviosum. In C. microchaete VD positively responded to average temperature in the late-wet season and in the previous dry season, and CA and Ks were higher in years with warmer wet and previous early-dry seasons, as well as in years with higher PDO values. These responses were independent from ring-width variability only for C. microchaete. For C. pluviosum, vessel chronologies were more responsive to local temperature variability, and only MVA and CA positively and negatively responded to moisture in the early-dry and the previous dry seasons, respectively. Our results show that wood hydraulic structure in SDTFs is responsive to climate fluctuations. The combined study of ring width and wood anatomy allows having a more complete picture of the influence of climate on growth, particularly in species as C. microchaete which show low collinearity of tree-ring width and wood plasticity in response to climate variability.